IPA 91-11.16

PROCEEDINGS INDONESIAN PETROLEUM ASSOCIATIONTwentieth Annual Convention, October 1991

EOCENE SUBMARINE FAN SEDIMENTATION IN SOUTHWEST JAVA

D.M. Schiller*R.A. Garrard**Ludi Prasetyo*

ABSTRACT

Submarine fan deposits can be important explorationtargets but have yet to be widely exploited as potentialoil and gas reservoirs in the Indonesian region. Veryfew have been actively drilled or even recognized in thesubsurface, even though they should be relativelyfrequent given the active tectonic setting of the area.There are many reasons why these deposits havereceived so little attention, including the lack of a welldescribed ancient example within the region.

Well exposed coastal outcrops of the Middle to LateEocene Ciletuh Formation located in the Ciletuh Area,Southwest Java, have been described on the basis offield study and laboratory analysis, and interpreted as asand-dominated submarine fan complex. The outcropsconsist of laterally continuous, fine to very coarsegrained sandstones and sandy conglomerates. Anumber of classic sediment gravity flow features arepresent including turbidites with paJ;tial Boumasequences, debris flow deposits and fluidized slumpdeposits. The sediments are believed to have possiblybeen deposited in a series of parallel slope grabensoriented perpendicular to slope.

Two separate lithofacies are recognized in theCiletuh Formation; a quartzose lithofacies composedof mostly quartz (58-84%) and a wide variety oflithic rock fragments; and a less pervasive volcaniclithofacies composed almost entirely of volcaniclasticsediments. Mesozoic granitic continental crust and LateCretaceous subduction complex areas lying to the northare interpreted to have supplied the majority of quartzand lithic fragments, while a possible Eocene localvolcanic arc is believed to have sourced the volcanics.

* P.T. Robertson Utama Indonesia** Atlantic Richfield Indonesia Inc.

The reservoir quality of the quartzose sandstones ispoor due to near complete destruction of originallyhigh primary porosity by a combination of compactionand carbonate cementation. Primary intergranularporosity values are estimated to have ranged from25-40% prior to burial. Tectonic compaction associatedwith subduction compression is believed responsible fordestruction of a large percentage of the porosity.

Even though the Ciletuh Formation deposits examinedin this study have very low reservoir potential, theypresent a useful example of a sand-rich submarine fanin the region, and indicate that similar sandstoneselsewhere in Indonesia could provide a viablepetroleum reservoir under more favorable tectonic ordiagenetic conditions.

INTRODUCTION

The Ciletuh Area of Southwest Java contains one ofthe most extensive and best preserved Early Tertiarysequences (Ciletuh Formation) in Indonesia. So farvery little detailed work has been undertaken onsedimentology, petrology or biostratigraphy. Ourrecent studies have identified a classic sedimentarysuccession of submarine fan origin that was probablydeposited over the leading edge of the southern SundaShield Margin during the Middle to Late Eocene.

An attempt is made here to describe what we have seenboth in the field and in laboratory samples. We believethis may represent one of the first detailed studies todate of an Early Tertiary submarine fan sequence inIndonesia.

Throughout the study the term "submarine fan" isutilized because it is the one which has come to be most

frequently associated with the description of all deepwater turbidites and their processes. In reality, a broadspectrum of turbidite types and morphologies are now

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recognized and only few demonstrate a classical fan-shaped geometry (Barnes and Normark, 1985). Forthese reasons we do not use the term to propose a fan-shape for the Ciletuh Area sandstone deposits.

Location

Our regional investigation extended over an area of 460square km located in the Province of West Java,Indonesia, some 120 km due south of Jakarta (Figure1). The Indian Ocean lies immediately to the west andsouth while the Neogene to R~cent volcanic centers ofGunung Salak and Gunung Gede are situated to thenorth. The main outcrops of Pre-Tertiary and EarlyTertiary rocks cover an onshore area of 140 square kmmaking it one of the largest exposed sequences of thisage in Java. The town of Pelabuhan Ratu, located28 km to the northeast of Ciletuh Headland, representsthe main settlement and administrative center for thearea. The physiography and bathymetry are shown inFigure 2.

PREVIOUS FIELD INVESTIGATION ANDEXPLORATION ACTIVITY

The first published description of the Ciletuh Area iscontained in van Bemmelen (1949), which is basedmainly on the unpublished field work of Duyfyes(1941). Van Bemmelen (1949) named the LowerTertiary rock unit of the area the Ciletuh (Tjiletuh)Beds, which he divided into two main groups. Theseinclude an assemblage of quartz sandstone, quartzconglomerate, mudstone and minor coal; and anassemblage of polymict breccia, sandstone andgreywacke containing metamorphic and volcanic rockfragments. The Ciletuh Beds were later renamed theCiletuh Formation by Marks (1957) and the area wasformally mapped by Sukamto in 1975.

More recent studies have focused their attention onimbricate subduction units of Pre-Tertiary ultrabasicand metamorphic rocks which underlie the CiletuhFormation. Endang Thayyib et al (1977) described aninterpreted melange complex consisting of blocks ofPre-Tertiary ophiolite, metamorphic and sedimentaryrocks set in a pre-Middle Eocene, sheared shaleymatrix. Foraminiferal analyses suggested an age ofMiddle Eocene to Early Oligocene for the CiletuhFormation, which they concluded unconformablyoverlies the melange complex. Their view wascountered by Soejono Martodjojo et al (1978) whoproposed the Ciletuh Formation conformably overliesthe melange complex, suggesting uninterruptedsubduction of the Indian Ocean Plate within Southwest

Java since the Late Cretaceous. This was based partlyon field description of the Ciletuh Bay area, east of

Gunung Badak, which was interpreted to possess lowerslope characteristics.

Later field and laboratory work performed inconnection with the IPA Field Trip Committee firstidentified submarine fan turbidite facies within theCiletuh Headland sequence (Garrard et ai, 1990).

Petroleum exploration activity is limited to offshoreseismic data acquisition and a solitary exploration welllocated approximately 100 km to the west of CiletuhBay near Pulau Deli. The Ujung Kulon-1A well, drilledby Amoco in 1985, reportedly encountered a thicksequence of Early Tertiary sedimentary rocks. ~

METHODS

This study is based on the results of field reconnaissanceof the Ciletuh Bay Area, including measurement anddescription of sedimentary sections (Figures 9 to 13),and supportive laboratory analyses performed oncollected outcrop samples. A complete list of allsamples and analyses is presented in Table 1, andsample locations are shown in Figure 4. Lab analysesincluded thin section petrology, foraminiferal andnannofossil micropaleontology, palynology and K/Arage dating. Radiometric dating analyses wereperformed to understand the relationships of igneousand metamorphic rock units of uncertain age whichoccur in close proximity with the Ciletuh clasticsequences. A few pebbles from the Ciletuh clasticswere also analyzed (see Table 7). The surveyedlocations were restricted to mainly well-exposed andaccessible coastal outcrops (Figure 4). Thin sectionpoint count analysis (250 counts/slide) were performedonly on Ciletuh Formation clastic samples. Sorting wasdetermined using the visual comparators of Longiaru(1987).

REGIONAL GEOLOGY

Tectonic Setting

The Ciletuh Area is located on the leading edge of theSunda Shield margin to the south of the present dayactive volcanic arc. Offshore lies the Java Trench, aforearc basin and accretionary prism associated withthe northerly subduction of the Indian Oceanic Plate.To the north of the volcanic arc are the Early Tertiarybackarc basins of the West Java Sea including theSunda, Arjuna and Jatibarang Sub-basins.

The Ciletuh Area has probably remained in a forearc orinterarc position throughout the Tertiary.

Paleogene sedimentation appears to have commencedhere, and elsewhere in West Java, during the Middle toLate Eocene (Baumann et aI, 1972).

These sediments were preferentially deposited withinisolated rift-grabens which formed in response toextensional tectonics across much of the Sunda Shield(Figure 5). Rifting was a widespread regional eventwhich is believed to have been initiated by the collisionof India into Asia during the earliest Tertiary (Daly,et aI, 1991).

Prior to the Tertiary, fragments of oceanic terrain hadbeen accreted onto the southern margin to the SundaShield. Evidence of Cretaceous subduction andaccretioQary wedge formation can be seen at Ciletuhand at Karang Sambung in Central Java (Figure 1). TheEarly Tertiary Ciletuh Formation turbidite depositsprobably. rest unconformably on the Cretaceousaccretionary complex.

The north-east to south-west trending Cimandiri FaultSystem, which extends through the Bandung Valley,may have been initiated as an Early Tertiary structurallineament and defined the southern edge of the SundaShield. If so, a major submarine fault scarp possiblyexisted over which the siliciclastic-rich sediments of theCiletuh Formation were deposited onto the adjacentdeep marine plain. Thick sequences of Miocenevolcaniclastics now conceal much of this region.However, all of the Eocene sedimentary outcropslocated to the north of the Cimandiri Fault Zone areknown to be of shallow marine, deltaic or fluvial origin(Garrard et aI, 1990).

The development of a post Eocene volcanic arc alongthe axis of present day Java appears to have cut off thesupply of siliciclastic sediments from the north. All ofthe Oligocene and younger detrital sediments along thesouth coast are dominated by volcaniclastics. Nosediment transport system apparently persisted into theOligocene and later Neogene, connecting theseyounger sequences with the granitic terrain of theSeribu Platform and other areas.

During the Eocene a more southerly magmatic arcmost likely existed which supplied the Ciletuh Area attimes with large volumes of volcanic material. Unlikethe succeeding more northerly arc, this southern systemprobably remained largely below sea level for much ofits life. The presence of isolated coral fragmentsinterbedded with the volcanics indicates shallow marineconditions persisted at times.

The main episode of uplift and erosion, as elsewherealong the southern margin of the Sunda Shield, took

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place in the Middle to Late Miocene. Compressionaltectonics associated with continental collisions inEastern Indonesia inverted many of the early formedhalf grabens (Letouzey et aI, 1990) to produce classic"Sunda" type folds. Breached inverted anticlinesexposing Early Tertiary sequences can be seen clearlyat Gunung Walat, Bayah and Cikalong (see Sukamto,1975). The inversion and unroofing of the CiletuhFormation almost certainly took place at this timein response to the same compressional forces. Thethickest preserved Early Tertiary section can as a rulebe expected along the axis of the inversion.

Further episodes of sedimentation and inversion tookplace during succeeding Pliocene and Holocene timesresulting in the formation of the Jampang Plateauand other present day physiographic features. Thedevelopment of the deep water Pelabuhan Ratu Baymay have occurred at this time in response to dextralstike-slip movement along the Cimandiri Fault Zone(Figure 8). Recently uplifted Quaternary coral depositssuggest tectonism is still active in the region.

Lithostratigraphy

The interpretation of the lithostratigraphy forSouthwest Java is confused, mainly because of theprofusion of different formation names and the lackof reliable stratigraphic control. The problem iscomplicated by frequent north-south facies variationswhich in the past existed along the southern margin tothe Sunda Shield due to active tectonism and rapidlyfluctuating water depths. An attempt is made here toshow the probable relationship between the differentEarly Tertiary rocks seen in outcrop and place themwithin what may have been their paleogeographicsetting (Figure 6).

The Ciletuh Area contains the oldest geologicalsequences preserved in Java. Only Karang Sambung inCentral Java (Figure 1) has an equivalent succession.The lithostratigraphy at Ciletuh includes excellentexposures of the Pre-Tertiary (Mesozoic?), EarlyTertiary and lowermost Neogene intervals. The lateNeogene and Holocene sections are largely missing as aresult of recent uplift and erosion although they can stillbe seen to the north of the Cimandiri Fault Zone.

a. Pre- Tertiary

Pre-Tertiary outcrops occur at four main localities;Gunung Badak, Gunung Beas, Ujung Sodong Baratand Ombak Tujuh (Figure 3). An ophiolitic assemblageof peridotites, gabbros, pillow basalts and serpentinitesis associated with metamorphics, including greenschist,

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mica schist, amphibolite schist, phyllite and quartzite.Sukamto (1975) refers to the metamorphics as the"Pasir Luhur Schist" after an outcrop along theCikepuh River. Other names include the CitiremFormation for the extrusives and the Gunung BeasFormation for the ultrabasics. Until this study noradiometric age determination had been undertakenand this interval was assumed to be of Mesozoic agebased on mainly stratigraphic assumptions.

Field relationships between the various rock types arenot totally clear and the entire Pre-Tertiary sequencehas been previously interpreted as a melange complex(Thayyib et aI, 1977; Martodjojo et aI, 1978). Manyindividual subduction unit components appear to befault-bounded.

b. Early Tertiary

The subduction complex is overlain (probablyunconformably) by the Eocene Ciletuh Formation, athick series of quartz-sandstones and conglomerateswith occasional contemporaneous volcaniclastics.

During our field studies a net interval (excluding thevolcanics) of approximately 400 m was measured atoutcrop although this does not probably represent totalthickness. Both van Bemmelen (1949) and Marks(1957) suggest possible thicknesses of 1500 m or more.Offshore a more complete succession may be preservedex. ~ndi'ngup into the early part of the Oligocene (fromUjung Kulon-1A well data). No Eocene-Oligocenecontact can be seen onshore.

Radiometric age dating (K-Ar) of the sandstonessuggests an Early Cretaceous age (134 + 3 ma) for thedetrital feldspars. This is approximately equivalent tothe granitic Pre-Tertiary subcrop of the Seribu Platform(Figure 8) located 100 km to the north, in addition toother granites of the Sunda Shield. Sediment transportof the more siliciclastic Ciletuh sandstones wasprobably southward away from the granitic terrain ofthe Southern Sunda Shield Margin (Figure 8).

The Early Tertiary sequence has now been tectonized.Extensive faulting and jointing together with variablestrike and dip for the bedding is seen in the field. Thisepisode of deformation probably took place mainlyduring the Late Miocene inversion.

c. Oligocene

No Oligocene strata have been recorded i:>the CiletuhArea. Formations of this age have been reportedfurther north at Cikalong near the Cimandiri FaultZone and at Cijengkol near Bayah. Van Bemmelen

(1949) describes a 200 m thick sequence at Cikalongof "marly clays with reticulate Camerina" (i.e.Nummulites) resting conformably on 1000 m of cross-bedded sandstones, conglomerates and coal ofprobable Eocene age.

Elsewhere in some parts of Java and the East JavaSea the Eocene appears to be followed conformablyby Oligocene deep water sediments associatedwith a major marine transgression. Close to thevolcanic centers the succession becomes dominated byvolcaniclastic material (Baumann et aI, 1972 and 1973;Hamilton, 1979).

d. Neogene to Recent

Interbedded volcaniclastics and fossiliferous claystoneswith sporadic limestone intervals of the JampangFormation outcrop to the north and east of the CiletuhArea. An interval thickness of more than 1200 m outcrops in the Jampang Plateau and has been dated asEarly to Middle Miocene age (Sukamto, 1975). TheJampang Formation is fault bounded to the southagainst the Eocene (Figure 3).

The Miocene here was a period dominated by volcanic-lastic sedimentation associated with an island arcsystem located north of the Cimandiri Fault Zone.Water depth at this time appear to have been variable,although overall it is a regressive sequence.

During the Middle to Late Miocene the whole areawas uplifted, folded and eroded. The succeedingBenteng and Bagian Formations (Upper Miocene)rest unconformably on the older sediments. Theseformations do not outcrop in the Ciletuh Area but canbe seen further to the east and north.

BIOSTRATIGRAPHY AND ENVIRONMENTS OFTHE EARLY TERTIARY SECTION

Biostratigraphy

Biostratigraphic analyses were performed on a total of43 samples. A large number of the samples examinedfor palynomorphs, foraminifera and nannofossilsproved barren. The majority of the fossiliferoussamples yielded assemblages of low abundance andpoor preservation. The biostratigraphic marker taxapresent, however, indicate a Middle to Late Eoceneage for the Ciletuh Formation (Figure 7).

a. Foraminiferal Micropaleontology

The foraminiferal assemblages recorded contain

variable proportions of planktonic and calcareousbenthonic taxa. Rare occurrences of planktonic markertaxa indicate a general Middle to Late Eocene age,Zones P17-P14. The presence of Globorotalia (M)spinulosa, recorded from one sample, if in situ, wouldrestrict the age to Middle Eocene, Zones P14-PlO.

In addition, larger foraminifera including Nummulites(Oligocene-Paleocene) were recorded. Their poorpreservation, however, precludes a precise dating.

b. NannofossilMicropaleontology

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The majority of the samples yielding nannofossilscontain relatively short ranging taxa indicative of aLate-Middle Eocene age, within the range of ZonesNP20-NP15. The occurance in a number of samples ofthe marker taxa Cribrocentrum reticularium andSpenolithus spiniger would suggest a Middle Eoceneage, restricted to the zonal range NP16-NP15.

Of the three biostratigraphic disciplines utilized,nannofossil analyses proved to be the most consistent inproviding age diagnostic Eocene marker taxa.

c. Palynology,

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Palynological zonation schemes for the Early Tertiaryare not yet as well defined as those for foraminiferaand nannofossils. In addition, recovery from mostsamples was poor with short ranging index formsrarely observed. However, the co-occurence insample CLH/911002 of Proxapertites SP (psilate) andVerrucatosporites usmensis suggests an EarlyOligocene to latest Middle Eocene age. Long spinedSpinlzonocolpites echinatus also suggests that a Late tolatest Middle Eocene age is most likely for this sample.Sample CLH/911003 which contains Proxapertitescursus and Verrucatosporites usmensis is also indicativeof a Late to latest Middle Eocene age. Overall, the longranging dates obtained for most of the other samplesare consistent with the foraminiferal and nannofossildata. Possible Cretaceous reworking is evident fromthe presence of a specimen of the gymnosperm pollenInaperturopollenites limbatus in sample CTH/911002A.

d. Interpretation

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Based on a combination of foraminiferal andnannofossil evidence, the age of some CiletuhFormation samples can be further refined due tothe narrow overlap of foraminiferal Zone P14 andnannofossil Zone NP16 (Figure 7). If these samples arerepresentative of most of the Ciletuh Formation,deposition of most Ciletuh sandstones could havepossibly occurred over a period as short as 1 Ma (overthe absolute age interval 44-45 Ma). .

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Considering the depositional setting and sedimen-tological processes which took place at these locations,it is important to note that reworking of bio-stratigraphic marker taxa might have occurred. Thepossibility of a younger age, especially for samples withrare occurrences of markeT taxa, cannot totally beexcluded.

Results of analyses of three samples from the PulauKunti Breccia (Figures 7 and 13) proved stratigraphi-cally inconclusive at this stage. No age can be assignedto the section as a whole. The occurrence of both

Miocene and Eocene age indicators is possibly theresult of the presence of units of both these ages oralternatively contamination may have occurred.

Paleoenvironments

The paleontological data obtained reflects deposition ina variety of settings, ranging from estuarine to upperbathyal. Sedimentological evidence for such rapid sealevel fluctuations during deposition of the CiletuhFormation was not recorded. It is therefore thoughtthat downslope transport of material from a shallowmarine environment introduced supratidal to middleneritic elements into an outer neritic to upper bathyalsetting (100 - 200 m +) supporting sedimentologicalevidence for such processes.

These results also illustrate how environmentalbiostratigraphic analysis of drill cuttings or coresamples from a submarine fan sequence could easily bemisinterpreted due to the presence of displacedshallower fauna or flora.

RADIOMETRIC DATING AND BASEMENT AGES

Radiometric dating was performed on a numberof samples utilizing K/Ar methods (Table 7). Themajority of samples submitted for analysis wereunfortunately unsuitable due to diagenetic alteration.Most results are inconclusive and further testing will benecessary, however, they do suggest some intriguingpossibilities.

A Ciletuh Formation volcaniclastic sandstone sample(CTH -01-010) was also radiometrically tested(plagioclase and whole rock phase). The samplecontains a Middle to Late Eocene microfossil

assemblage which defines an approximate absolute ageof 39-45 Ma (see Figure 7). Assuming that the wholerock radiometric age is more accurate (50.1 + 2.1 Ma),Eocene volcanism occurred either slightly earlier orpossibly penecontemporaneous to Ciletuh Formationdeposition.

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Plagioclase and whole rock analysis from a gabbrosample (CLH-91-002A) yielded ages equivalent to arange of latest Paleocene to Middle Eocene (see Table7). These ages are significantly younger than assumedby previous studies (Mesozoic) (van Bemmelen, 1949;Sukamto, 1975). The close agreement of the gabbrowhole rock age (50.9 + 2.1 Ma) with that of thevolcaniclastic sandstone suggests possible reheating ofthe gabbro due to Eocene volcanism.

Radiometric analysis of a basaltic pebble from theCiletuh Formation conglomerates indicates that someCiletuh volcanics were probably sourced from the Pre-Tertiary Citirem Formation pillow basalts. A LateCretaceous age (89.6 + 3.0 Ma) for a portion of theCitirem Formation is also suggested.

Dating of the andesite from Pulau Kunti (see Plate 5D)is inconclusive. An Early Miocene age is indicated(Table 7), however andesitic pebbles petrographicallyidentical to the Pulau Kunti andesite were recoveredfrom debris flow/slump deposits encased in EoceneCiletuh Formation sandstone and mudstone at Ciletuh

Beach (Plate 5C). Further analysis will be necessary todetermine if these andesites are associated with Pre-Tertiary, Eocene or post-Eocene volcanism.

PETROGRAPHY AND SEDIMENTOLOGY OF THECILETUH FORMATION

FIELD SETTING AND OUTCROP DESCRIPTION

Nearly all the studied exposures were beach or coastaloutcrops located both within and south of Ciletuh Bay(Figure 4). Inland exposures were typically small orcovered due to weathering and jungle overgrowth.Outcrop measurements were often complicated by bothtectonism and partial submergence by present day sealevel.

Ciletuh Formation Lithological Facies

Two main lithological facies were recognized in theCiletuh Formation outcrops; (i) light-brown-coloredquartzose sandstones, pebbly sandstone, polymictconglomerate and very rare mudstone; and, (ii)greenish-colored volcaniclastic sandstone withoccasional interbedded tuffaceous shale, sandyvolcanic conglomerate and polymict volcanic breccia.The lithologies are both dated as Eocene based on

"biostratigraphic results (Figure 7). Examples ofinterbedded quartzose and volcanic lithofacies wereonly seen at the tectonically complex Ciletuh Beachlocality where minor interbedding of quartzosesandstone, mudstone and volcanic-rich polymictbreccia is evident. '

Quartzose Sandstone and Conglomerate Lithofacies

The quartzose sandstones are found mainly in thesouthern two-thirds of the study area, with distributionextending from Ciletuh Headland to at least as farsouth as Ujung Sodong Barat (Figure 2).

The Ciletuh Headland section from Karang Capio toLegong Bedog contains a tectonized, but relativelyconcordant, 300 m sequence of quartzose sandstoneand conglomerate. This comprises the thickestcontinuous sequence seen in the study, althoughpossible unrecognized repeated sequences may occur.Six measured sections totaling 100 m in thickness havebeen described from Ciletuh Headland. Each isseparated by covered, faulted or oceanic-sub-mergedsections (Figures 9 to 12). Mudstones are very rare andcomprise less than 1% of the sequence.

Previous descriptions of the Ciletuh Formation havementioned the presence of coal beds (van Bemmelen,1949; Sukamto, 1975), however our reconnaissancesuggests that no true coal beds exist. It is believed thatsandstone beds enriched with redeposited coal andcoalified plant fragments have been misinterpreted inpast studies (Plate 4A).

Most other quartzose sandstone/conglomerate outcropswere too small, tectonized or poorly exposed towarrant detailed measurement (Pasir Haur, CiletuhBeach, North Ujung Sodong Barat, etc). These tend tobe compositionally identical to those seen in theCiletuh Headland section.

A notable exception is an approximately 50-60 m thick,vertically continuous sequence of thinly-beddedand laterally continuous, fine to coarse grainedsandstone and lesser mudstone located south of UjungBatununggal (Figure 2). Detailed description andmeasurement has not been undertaken at this time.

Volcanic Sandstone Lithofacies

The distribution of the volcanic sandstones is confined

mainly to areas within Ciletuh Bay (Figure 4).Two well exposed sequences were measured. ThePulau Kunti section, consists of a 15 m gradually finingupward sequence containing a basal volcaniclasticconglomerate/breccia and capping shale. This isoverlain by a thick sequence of polymict brecciacontaining varied cobble-to boulder-sized meta-morphic, sedimentary and volcanic rock fragments(Figure 13) which may belong to a younger interval (seeFigure 7, P. Kunti Breccia). The Pulau Daheu sectionconsists of 15 m of thick-bedded, coarse-grainedvolcaniclastic sandstone with intervals of thinly

interbedded fine to medium grained sandstone andtuffaceous mudstone (Figure 13).

SANDSTONE PETROGRAPHY

Quartzose Sandstone

The quartzose sandstone lithofacies is characterized byquartz-rich sandstones and conglomerates that can beclassified as mainly lith arenites and sublitharenites(after Folk, 1974; Figure 15).

a. Texture

I,~) The average sandstone is fine to coarse grained, well to

moderately sorted, subangular to subrounded, andtexturally and compositionally mature to submature,although grain size ranges from silt to cobble andsorting from very well to very poor (Figure 16). Someof the larger clasts such as pebbles and cobbles arefrequently rounded to well rounded.

b. Framework Grain Composition

Framework gmin mineralogy is similar, irrespective ofgrain size, fan facies or sample location. Quartz and awide variety of lithic rock fragments comprise mostgrains, while feldspar content is low (average 3%,Table 5). Monocrystalline and polycrystalline quartz(including metaquartzite) make up 58-84% of allframework grains.

The lithic rock fragments are extremely varied andinclude, in order of decreasing frequency, chert,volcanic rock fragments (mostly altered basalt andcrystal/vitric tuff), sedimentary rock fragments,metamorphic rock fragments and plutonic rockfragments. A detailed list of all lithic grains, bioclastsand accessory grains is presented in Table 8.

Detrital feldspars are chiefly orthoclase with lesserplagioclase, microcline and rare perthite. Pre-burialfeldspar content was slightly higher since manyfeldspars have been completely replaced by authigenickaolinite.

Accessory grains make up less than 3% of most samplesand include coalified plant fragments (i.e. coalified in-situ), redeposited coal fragments, armored mud balls,mica, calcareous bioclasts (most replaced by Fe-calciteand partly iron oxide-stained), glauconite, phosphateclasts and heavy minerals.

Bioclasts observed in thin section are heavily abradedand represent mostly displaced shelf fauna rather thanindigenous deep water biota. A partial list includes

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large benthonic forams, coral and rare planktonicforams (see Table 8). It is not uncommon to only findrare planktonic forams in deep marine turbidite settingsbecause hemipelagic sedimentation is often "drownedout" by high rates of sand deposition.

c. Matrix

Detrital clay content is low in most samples. Manycontain less than 4%, though matrix content can be athigh as 8% in some very poorly sorted conglomeratesand very fine sandstones.

d. Porosity and General Diagenesis

All examined sandstone samples contain generally verypoor to poor visible porosity (trace to 7%), and nearlyall is interpreted as secondary in origin, created byrecent near surface weathering. Virtually all primaryintergranular porosity has been destroyed by acombination of compaction and cementation.

Early poikilotopic ferroan-calcite cement is abundantin some horizons (up to 20% ). This is accompanied bycalcite etching of quartz grain surfaces and partial tocomplete replacement of some feldspar and lithic rockfragments by ferroan-calcite.

Other cements and replacements include silica cementas quartz overgrowths, authigenic pore-filling andfeldspar replacing kaolinite clay, authigenic grain-coating and pore-filling chlorite clay, and pyrite. Partialreplacement of detrital and authigenic chloritic clays byiron-oxide is also common due to weathering. Theseauthigenic minerals together comprise from 2-13% ofmost samples, though their ratio greatly varies fromsample to sample (see Figure 15).

Compaction has destroyed all primary intergranularporosity which was not infilled by authigenic cements.Compaction' and diagenesis are discussed at greaterlength in the Reservoir Development section.

Volcanic Sandstone

The volcanic sandstones can all be classified aslitharentites and are composed almost entirely ofvolcaniclastic grains and lesser plagioclase (Table 6).

a. Texture

The examined samples are typically finer-grained andtexturally and compositionally more immature than thequartzose suite. The average sandstone is very fine tomedium grained and well sorted, though grain sizevaries from very fine sand to granule, and sorting, fromwell to moderate (Figure 16).

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b. Framework Grain Composition

Volcanic rock fragments comprise 77-92% of theframework grains, and include mainly microliticandesitic crystal/vitric tuff, porphyritic plagioclase /clinopyroxene andesite, basalt, pumice, glass shardsand tuffaceous shale fragments. Grain alteration isheavy, with common glass devitrification and grainreplacement by chlorite, smectite and lesser zeolites.

Plagioclase grains are normally angular, internallyzoned, and obviously represent reworked volcanicphenocrysts. Other grains include (in order ofdecreasing frequency) sedimentary rock fragments(mostly chloritized claystone/shale, calcareous mud-stone and rare quartzose siltstone and sandstone),calcareous bioclasts (mostly whole planktonic and smallbenthonic forams), pyroxene (mostly augite ), organicfragments, muscovite, glauconite, potassium feldsparand chert. Quartz comprises less than 1% of mostsamples.

c. Matrix

Matrix material consists of devitrified and chloritizedtuffaceous clay. Some interbedded claystones andshales contain carbonate mud and non-volcanicterrigenous clays, in addition to tuffaceous clay matrix.

d. Porosity and General Diagenesis

Porosity development is generally extremely poor(trace - 1%) due to a combination of compaction,propylitization and lesser cementation by zeolitesand authigenic chlorite. Volcaniclastic sandstonestypically have very low preserved porosity due to theirabundance of mechanically and chemically unstablegrains (Surd am and Boles, 1979).

DEPOSITIONAL FACIES

Evidence for Deep Marine Turbidite Sedimentation

A number of characteristics seen in the CiletuhFormation suggest that the quartzose and volcanicsandstone lithofacies were deposited as a series of highdensity sediment gravity flows in a submarine fansetting. A few of these features include turbidites withpartial and complete Bouma sequences, debris flowconglomerates, laterally continuous fine grainedturbidite facies, syndepositional slump folding,fluidization structures, resedimented conglomerateclast fabric, and displaced shallow shelf fauna mixedwith deep marine fauna.

Fan Facies Terminology

The following discussion utilizes the submarine fanfacies nomenclature (A-G) of Mutti and Ricci Lucchi(1972) which partly incorporates the well-knownclassical turbidite or Bouma Sequence (Figure 18A).The facies terms will only be used descriptively,without any fan association implications. The Mutti andRicci Lucchi "facies associations" (i.e., which faciesare associated with which fan subenvironments) wereoriginally developed for mixed clay and sand fansystems and are not directly applicable to the sand-dominated Ciletuh Formation fan sequences. Asummary of the seven facies types is provided in Figure18B.

Ciletuh Headland Quartzose Turbidite Facies

The Ciletuh Headland measured sections are composedof mostly medium to coarse grained sandstone andconglomerate equivalent to Facies A and B, withsubordinate intercalations of thin -bedded, fine tomedium grained sandstones equivalent to Facies C andlesser Facies D, E and F. The sandstone to mudstoneratio is extremely high (100:1) and clay-rich facies areeither absent (Facies G) or rare (Facies E and clay-richFacies D). Preserved burrow traces are also extremelyrare.

a. Facies Measurement

The Ciletuh Headland section is organized into at leastfour to possibly five megasequences composed ofFacies A and B sandstone/conglomerate unitsinterstratified with fining/thining-upward, morelaterally continuous Facies C sandstone units (Figures9-12). The exact thickness of each megasequence couldnot be accurately measured due to the frequency ofcovered or submerged sections. Estimations were madeby calculating the approximate thickness of unexposedsection and extrapolating the fining/coarsening trendsseen in underlying and overlying exposed sections.Using these methods, three megasequences measuringfrom approximately 30 - 50 m in thickness wereidentified from measured Section "1" to the lower

part of Section "5" (Figures 9 to 11). A fourthmegasequence composed of a coarsening upwardsandstone interval is evident in the upper thirdof Section "5" (Figure 11), however thicknessescannot be estimated due to the extent of unexposedsection separating measured Sections "5" and "6"(approximately 100 m).

A description of the depositional facies types follows:

b. Coarse Sandstone and Conglomerate Features(FaciesA and B)

These facies comprise from 75-85% of the sequences.They consist of massive to more frequently faintlygraded, moderately to poorly sorted, medium to coarsegrained sandstone, gravelly sandstone and sandyconglomerate. The bedding thickness of individualflows ranges from 0.3-4.0 m, though most beds measure0.5-1.0 m. Flow stacking has produced amalgamatedsandstone / conglomerate beds over 20 m thick.Scouring is very common, often producing uneven bedswith rapid lateral changes in both bed thickness andgrain size (Plate 2A). Complete beds are often notpreserved due to erosion by successive flows. Scours upto 1.5 m deep were observed, though most flows showmore moderate down cutting , especially Facies B. Smallscale growth faulting is also evident in some areas.

The Facies A conglomerates are typically poorly tovery poorly sorted, polymict, with rounded pebblesand cobbles set in a very fine to medium grained,sometimes argillaceous matrix. Faint planar- to cross-bedding is sometimes outlined by pebbles, thoughbedding traces are often absent. Large, light-coloredaltered basalt clasts and rust brown-colored oxidized

carbonate mudstone clasts are frequent, in addition tooccasional rip-up clasts of finer-grained sandstone andmudstone. Normal grading and less frequent inversegrading are sometimes evident.

The Facies B sandstones are typically fine to coarsegrained, moderately sorted, with parallel to sub-parallel, sometimes undulating laminations (Plate 4D).These beds are generally more laterally continuous andeven-bedded (i.e. flat upper and lower bed contacts)than facies A, though some scouring and lateralthickening / thinning are noted. Beds are in someinstances capped by a thin interval (0.1 m) of planar- towavy- to ripple-laminated, very fine to fine sandstonecontaining coalified plant fragments (Plate 4A). Faintfluid escape structures are also occasionally noted.

Some beds display characteristics intermediate toFacies A and B, or consist of Facies A grading bothvertically and laterally into Facies B (Figure 12). Theseobservations illustrate the close association of these twofacies.

c. Fine to Medium Grained Turbidite SandstoneFeatures (FaciesC, D and E)

These facies represent 15 to 20% of the measuredsections, consisting of graded, very fine to mediumgrained, well - sorted turbidite sandstone beds. Theseare comprised of mostly Bouma divisions Ta-b and Ta-c

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and Tb-c with lesser Ta-d, Tb-d and rare Ta-e (seeFigure 18A). Individual beds range in thickness from5 em to 1.2 m (typically 0.2-0Am) and display greaterlateral continuity and evenness than observed in thecoarser facies (Plate 2C). Thickness changes andscouring are minimal, though some lensing and broad,low relief scours are evident.

Common sedimentary structures include planar-bedding, wavy-bedding, ripples and occasional beddingdeformation. Coalified plant fragments are verycommon in the upper segments of fining-upward beds.Remnants of redeposited hollow seed pods are visibleon the tops of some bedding surfaces (Plate 4B).

The majority of the beds resemble Facies C with rareFacies D, however the mud-rich components whichnormally cap these facies are usually absent (Boumadivisions Td and Te, Figure 18A). The reasons for thisare possibly related to. the clay-poor nature of thesediment and erosion of poorly developed mud layersby successive flows. This could also be attributed tobypass of the clay component in each flow, resulting inclay deposition further downslope. These beds can bedescribed as "abbreviated" or "clay-starved" Mutti andRicci Lucchi Facies C.

Definitive Facies E, consisting of discontinuous, wavyto lenticular bedded sandstones, encased in sandymudstone, was only observed in a small portion ofmeasured Section "5" (Plate 3B). This is surprising forFacies E is often a major component of sand-rich fans(Howell and Normark, 1982). The atypical nature ofmany Facies C beds suggest they could instearepresent couplets of thin bedded Facies B (i.e., FaciesB2) ana unusually sand-rich Facies E (see Figure 11).

d. Deformed Bed Features (Facies F)

Deformed beds (Facies F) comprise only a smallproportion of the measured sections (approximately3%), but are often spectacular when present. Examplesinclude fluidized slump deposits with chaotic,convoluted bedding developed in Facies B (Plate 3C)and an overturned slump fold composed of thinlyinterbedded Facies C and D lithologies (Plate 3D).

Volcaniclastic Turbidite Facies

The Ciletuh Formation volcanic sandstones andassociated lithologies described at Pulau Kunti andPulau Daheu are also interpreted to representsubmarine fan gravity flow deposits. Compared withthe Ciletuh Headland section, the volcanics are finer-grained, have a lower sandstone to mudstone ratio(approxiamtely 10:1 to 15:1) and bedding with greaterlateral continuity and less frequent scouring.

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a. Polan Daheu Section

The Pulau Daheu section is composed of mainly thicklybedded (0.6-4.0m), medium to very coarse grainedsandstone equivalent to Facies B and lesser A, withinterstratified units of very fine to medium grainedFacies C and D sandstones (Figure 13, Plate 5A).Unlike similar facies seen in the Ciletuh Headland

sequence, the volcanic C and D Facies beds are cappedwith well-developed, clay-rich tuffaceous mudstone ormarl (i.e., Bouma Te division).

b. Polau Kunti Section

The Pulau Kunti section consists of 15 m of finingupward and thinning upward volcaniclastics overlainby 30-50 m or more of polymict breccia containingboulder- and cobble-sized clasts (Figure 13).

The seciton begins with a thick volcaniclastic debrisflow conglomerate/breccia containing pillow basaltfragments, which very gradually fines upward over aninterval of 8 m into an argillacous, fine grained volcanicsandstone. This is overlain by a series of fine- tomedium-grained sandstones capped with mudstone(Facies C) and culminates in a calcareous shale withthin sandstones (Facies D and G ?). A 2 m thick, poorlysorted and tectonized volcanic breccia containing largerip-up clasts of underlying shale and some polymictblocks separates the shale from the overlying polymictbreccia.

Many of the polymict breccia clasts are believed to havebeen derived from a local paleo high or horst of Pre-Tertiary accretionary wedge material, the remnants ofwhich may be the adjacent present-day peridotite/pillow basalt complex of Gunung Badak. The brecciarock types are extremely varied, and a partial listincludes basalts, chert, quartz andesite, phyllite, schist,meta-volcanics, meta-sedimentary rocks, limestone andCiletuh like quartzose sandstone.

No microfossils were recovered from the polymictboulder breccia, though both a nummulitic boulder anda single micropaleontology sample containing an agedisassemblage of Eocene and Miocene forams wererecovered from the "transitional" breccia (see Figure13). Possible contamination of the disassemblagesample is suspected, thus the age of the breccia isuncertain without further sampling.

FAN MODEL INTERPRET ATION

Ciletuh Headland Fan

The dominance of Facies A and B and the extremely

sand-rich nature of the Ciletuh Headland sequencesuggests it could possibly be analogous to a suprafanlobe (Figure 19); however, the mound-like geometry ofa suprafan can rarely ever be positively confirmed inancient fans solely from outcrop study (Nelson andNilsen, 1984; Shanmugam and Moiola, 1991). Thesetypes of fans can form in a variety of tectonic settingsincluding active margin areas with steep gradients andhigh sediment supply (Shanmugam and Moiola, 1991).Sedimentation can be extremely rapid due to the highfrequency of successive, coarse grained sedimentgravity flows. This markedly limits the available timefor suspension muds to accumulate between flows, andcan partly explain the paucity of burrowing and mud-rich facies seen in the Ciletuh sequence.

Segregation of the fan into well-developed upper,middle and lower fan regions, typical of classical mixedclay and sand fan systems, is usually absent in sand-dominated fans. The fan instead consists of a thick sandaccumulation, grossly equivalent to an expandedmiddle-fan region composed of accumulated channeland interchannel deposits. Development of slope andlower fah facies associations can be limited, and there isoften a blurred distinction between middle- and inner-fan regions (Link and Nilsen, 1980; Link et aI, 1984;Shanmugam and Moiola, 1991).

Several fan associations are represented in the Ciletuhsequence:

a. Coarse Grained Channel/Lobe Deposits

The majority of the Ciletuh Headland sequencerepresents amalgamated flow deposits consisting ofFacies A and B coarse grained sandstone, pebblysandstone and conglomerate (Plate 2B). The transportmechanisms were probably a mixture of mostly gravellyhigh density turbidity currents with fewer liquefied andfluidized sand flows (Lowe, 1982). Some of the morepoorly sorted, mud-rich and internally disorganizedconglomerates are interpreted as cohesive debris flowdeposits. At least four separate aggradational, finingupward sequences are believed to be present.

Many of the features of these deposits have be.enidentified in channelized sequences described in otherfan studies (Link and Nilsen, 1980; Link et aI, 1984).Scouring is relatively common in the Ciletuh sequence,however, there is little field evidence to suggestthat the flows were confined to semi-permanentchannels with pronounced down-cut and relief. Mostdeposits appear to have been unconfined flows or lobeswhich prograded over the top of earlier flows, usuallyresulting in only minor erosion or channeling (typicallyunder 1.0 m). Small channels, when present, appear to

have been created by small scale growth faulting, andwere quickly infilled by subsequent flows.

Alternately, it could also be reasonably argued that theflows were truly deposited in large confined channels,though the channel margins are not well-expressed inoutcrop. The entire deposit could possibly representthe infill of a single large slope channellbasin. Furtherstudy of the area will be necessary to fully resolve thesequestions.

b. Fine GrainedDeposits

Margin/LobeChannel Margin

The thin bedded, fine grained and more laterallycontim:ous intervals composed of mainly Facies C,D and E (Plate 2C) are interpreted to have beentransported by both high density and, to a lesser extent,low density turbidity currents (Lowe, 1982).

These sequences resemble levee or channel margindeposits which typically flank coarser grained channeldeposits (Link et aI, 1984; Howell and Normark, 1982),however, no examples of channels deeply eroding intothis facies are evident. The transition into overlyingcoarser grained facies is relatively gradual (Figure 11)and in some instances thickening-upward (Figure 10),suggesting possible lobe-like rather than channelizedfan deposition (see Mutti, 1985). Thus these couldalternately represent sediments deposited on themargins of a laterally-fining and laterally-thinning lobe.

Other Quartzose Turbidite Exposures

Due to the limited number of good exposurt(s, therelationship of the Ciletuh Headland fan facies withthose observed at other locations is unclear. With theexception of the fine grained quartzose sandstones seenat Ciletuh Beach and south of Ujung Batununggal, allother examined exposures were composed of coarsegrained sandstone and pebble conglomerate similar tothe coarse Ciletuh Headland A and B Facies (i.e., PasirHaur and numerous small exposures throughout thearea).

a. Ujung Batununggal Sequence

Preliminary investigation of the thinner bedded andfiner grained sequence located south of UjungBatununggal indicates they are composed of mostlyFacies B, C and E with lesser D and have a significantlylower sand to mud ratio than found at CiletuhHeadland. Many Facies C and B beds are organizedinto broad, lenticular deposits ranging from O.5-2.2m inthickness and 15-40m in width. These in some caseslaterally pinch-out into clay-rich Facies E and Facies D

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intervals (Plate 2D). The deposits are believed tocorrespond with depositional lobe facies located furtherdown slope from the Ciletuh Headland area.

b. Ciletuh Beach Area

The Ciletuh Beach area, located on the mudflatssouth-west of the Ciletuh River in Ciletuh Bay, consistsof a tectonically complex series of thinly beddedturbidite sandstones and mudstones which partly occurin association with volcanic and breccia facies.These may possibly correspond with a slope faciescontaining slump deposits, though this is uncertain dueto difficulties with distinguishing syndepositional fromlate tectonic deformation features.

A detailed discussion of this complex area is beyondthe scope of this publication, but a few of thecharacteristics include small, northwest-plunging,tightly recumbent and overturned folds, sometimeswith kink-plane development; large blocks of volcanicsandstone possibly rotated by faulting (Pulau Hadji);and lenticular to circular-shaped interbeds of volcanicsandstone and volcanic conglomeratelbreccia (debrisflows and slumps ?)set in a matrix of deformed,thinly interbedded quartzose sandstone and mudstone(Plate 5C). Some of the intervals resemble possibleolistostrome (Type I) melange (Cowan, 1985);although they may represent debris flows containingblocks of Pre-Tertiary accretion wedge materialderived from local paleohighs or horsts.

Volcanic Sandstone Turbidite As,sociations

The volcaniclastic turbidite sandstone sequences areinterpreted to have been deposited in a high gradientand sand-rich system similar to that of the CiletuhHeadland quartzose sequence. Sedimentation probablytook place under more episodic conditions andinvolved greater volumes of sediment within individualgravity flows. Facies A and B beds in the volcanicsequences are in excess of 4 m (up to 8 m). Periods oflow volcanic sediment input were long enough to allowaccumulation of thicker mudstone intervals (Figure13).

The reasons for why the volcaniclastic and quartzoseCiletuh Formation turbidite facies do not commonlyinterfinger still remains unclear. Biostratigraphicresults suggest the two were at least partially depositedduring the same period, however, their distributionsmay have been segregated due to different transportcourses partly controlled by complex basin morphology(see Paleocurrent Analysis section).

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PROVENANCE

Ciletuh Quartzose Lithofacies

Petrographic results indicate the Ciletuh Formationquartzose sediments were most likely derived from amixture of sources. These include uplifted subductioncomplex, continental crust or recycled craton-derivedsandstone, in addition to lesser contribution frompenecontemporaneous volcanism and nearby intra-basinal uplifts of Pre-Tertiary basement.

A series of ternary plots were prepared using themethods and provenance fields of Dickinson andSuczek (1979) (Figure 20). Even though our data baseis small (17 samples), smaller assemblages can yieldmeaningful results (Dickinson and Ingersoll, 1990).The average composition of the quartzose suite plotspart way between the Subduction Complex Field andthe Collision Orogen/Foreland Uplift Field (i.e.Recycled Orogen) in Ternary D (Figure 20).

Cretaceous subduction complex and continental crustareas lying to the north-northwest are the most likelysediment sources, given the location of the Ciletuh BayArea immediately south-southwest of the interpretedsuture separating these two regimes (Figure 8;Hamilton, 1979). Portions of the Cretaceous accretionwedge are believed to have supplied the majority ofchert, basalt, metaquartzite, metasediments and otherlithic rock fragments, while Sunda Shield graniticterrain areas sourced the majority of quartz, plutonicrock. fragments and feldspar. Radiometric dating offeldspar contained within a granitic pebble sampledfrom the Ciletuh Formation confer a Cretaceous agefor the quartz source (134 + 3 Ma).

The feldspar content of the Ciletuh sandstones is lowerthan expected for a sandstone sourced directly from acontinental block (see Continental Provenance Field,Figures 20A and 20B), for which there are two possibleexplanations. The quartz may have been recycled froman older, uplifted foreland sandstone for which theparent rock was Cretaceous granite. This is somewhatsupported by the presence of minor subarkosesandstone rock fragments within the Ciletuh Formationsandstones. Alternatively, the quartz could representfirst cycle, craton-derived sediments subjected tointense weathering during prolonged surface transport.Heavy weathering in tropical, low relief settings canconcentrate quartz through removal of feldspar andunstable lithics (Dickinson, 1985; Girty, 1991).

Eocene Quartzose Sediment Dispersal

The Ciletuh fan quartzose sediments were most likelysupplied from an associated shelf margin-delta. Delta-fed fans typically display rapid and uninterruptedsedimentation similar to that seen in the Ciletuhsequence. Many of the heavily oxidized clasts of theCiletuh Formation are suspected to have originatedfrom alluvial fans which fed into the associated river/delta system.

The large Eocene delta system of the Bayah Formation,visible in outcrop 35 km to the northwest of the CiletuhArea, is not believed to have been the main sedimentsupply for the Ciletuh Formation. Subtle compositionaldifferences and paleocurrent measurements (seefollowing section) suggest another delta systemmay have once existed to the northeast (possiblysoutheast ?) of the Ciletuh Area. Previous work showsthe Bayah Formation sandstones are slightly morequartz-rich, lithics-poor and finer-grained than theCiletuh quartzose sandstones (Garrard et ai, 1990).

Ciletuh Volcanic Lithofacies

The volcaniclastic sandstone average predictably fallswithin the Magmatic Arc provenance field (Figure 20).

The sediment immaturity and compositional homo-geneity suggests the volcaniclastics do not entirelyrepresent material reworked from older volcanics (i.e.,Citirem Formation), but are possibly the product of apenecontemporaneous volcanic arc which occured asnearby undersea volcanoes or volcanic islands. Thematerial could have been introduced directly, in theform of ashfalls and massive undersea pyroclastic flows,or indirectly, from periodic mobilization of subsea ornearshore accumulations of volcaniclastic material intoturbidites and debris flows (Cas and Wright, 1987).

PALEOCURRENT ANALYSIS ANDPALEOGEOGRAPHIC IMPLICATIONS

Paleocurrent indicators such as flute clasts were not

distinguishable in the Ciletuh Formation outcrops. As aconsequence, measurements are based mainly on lessreliable indicators such as the orientation of imbricate

pebbles (Plate 3A) and elongate plant fragments (Plate4B) observed mostly in plan view. Readings from ninedifferent locations within the quartzose facies weretaken using the methods of Potter and Pettijohn (1977),and corrected for structural dip when necessary. Rosediagram representations of the readings are presentedin Figure 21. Since clast dip direction could not alwaysbe determined in plan view, the data are displayed inbidirectional format.

The data indicate two different orientations; apredominant northwest-southeast paleocurrent trendwithin the northernmost six locations, and a northeast-southwest trend for the three southern-most locations.Imbricate clast fabric, seen in outcrops with well-exposed sideview, suggest a northwest paleocurrent forthe northern locations and southwest paleocurrent forthe southern locations (Figure 21). These directions arealso supported by the orientation of slump fold axesand asymetrical ripples when visible.

The implications of these results are uncertain givenboth the reliability of clast orientation measurements,and the possibility of clast orientation deviation causedby unidentified folding or tectonic rotation. If the dataare correct, the 90 degree difference in orientationbetween the northern and southern locations could beattributed to point-source sediment dispersal patternsand/or possible partial control of fan sedimenttransport by the structure of the underlying subductioncomplex (Figure 19).

A series of parallel, northwest-southeast trending slopegrabens is believed to have been developed in thesubduction complex basement of the Ciletuh Area dueto Early Tertiary extension (Daly et aI, 1991). Thelineaments and topographic remnants of this structureare still visible (see Figures 2,3 and 19). Sediment flowsentering perpendicular to the graben axis (i.e., fromthe northeast) could be abruptly redirected due to thebasin morphology (Figure 19). The result of turbiditedeposition in this setting could be a series of parallel,linear sand bodies similar to those in the Ciletuh Area.We are probably only seeing a very small portion of amuch larger fan complex in the Ciletuh outcrops, andfurther study will be required to define the true size andgeometry of the fan system, or if it is, in fact, fan-shaped at all.

HYDROCARBON EXPLORATION IMPORTANCE

RESERVOIR DEVELOPMENT AND DESTRUCTION

The Ciletuh Formation quartzose sandstones possessedhigh reservoir quality prior to burial. Primary porosityvalues are estimated to have ranged between 25-40%,using the sorting/porosity relationships of Beardand Weyl (1973). Virtually all the primary porositywas subsequently destroyed by cementation andcompaction.

Porosity Destruction Pathways

Petrographic analyses show that porosity destructioncould follow two different diagenetic pathways,depending on whether the sandstones were ferroan

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calcite-cemented or not (see lower portion Figure 22).The end result of both pathways is the same, with neartotal porosity destruction. Visible porosity seen in thinsection samples ranged from trace- 7%, however this isall secondary porosity, interpreted as a product of post-burial, near surface processes.

a. Ferroan Calcite-Cemented Pathway

In the calcite-cemented intervals, nearly all porositywas destroyed at an early stage prior to majorcompaction. This is evidenced by the absence of laterstage cements and the presence of poikilo topic ferroancalcite cement fabric (i.e. uncompacted grains withfloating to point grain contacts, set in large cementcrystals, see Plate Ie).

The controls on ferroan-calcite cement distribution

within the Ciletuh sandstones are not totally clear,however petrographic data suggest a relationshipbetween carbonate cementation and the presence ofbioclasts and other carbonate grains (Figure 16).Ferroan-calcite may only have formed in sapdstonescontaining calcareous clasts which served as nucleationsites (i.e. seed crystals) for carbonate cementprecipitation.

b. Compaction Pathway

The majority of Ciletuh quartzose sandstones containno ferroan-calcite cement and porosity has beendestroyed by mainly compaction and subordinatecementation by later stage silica and authigenickaolinite and chlorite clays. The ratio of compaction-porosity loss to cementation-porosity loss is estimatedto range from 3:1 to 2:1 for most samples. Highcompaction is illustrated in thin section by mostlyconcave-convex grain contacts, pressure solution andheavy deformation of ductile framework grains such asaltered volcahic rock fragments, shale clasts and micas(Plate lA and lB).

Burial or Tectonic Compaction?

Vitrinite reflectance analyses performed on coalifieddetrital plant fragments from the Ciletuh Formationsandstones indicate they were buried no deeper than1.5-1.7 km (Ro=O.4). This depth is much shallowerthan expected to account for the observed levels ofcompaction and compactional porosity loss.

a. Calculation of Expected Porosity Loss from BurialCompaction

Porosity prediction calculations were performed usingthe methods of Scherer (1987) in order to estimate the

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amount of compactional porosity loss and preservedporosity expected from normal burial compaction atdepths of 1.7 km (see Appendix 1). The volumepercent of intergranular cement in each sample wassubtracted from the calculated Scherer value, since thecement represents porosity destroyed by processesother than compaction.

The values of "estimated preserved porosity" calculatedin this manner average 14% (range 6-22%, n=12),suggesting that more than simple burial compactionmay be responsble for the poor reservoir quality of theCiletuh Formation sandstones.

Predictive porosity models such as the method used areadmittedly incapable of being applied universally to allsandstone compositions in different burial situations,due to their inability to incorporate corrections for allthe interelated factors which can influence porosityreduction during compaction (i.e. texture, rockheterogeneity, over-pressuring, etc.). The compactionof sandstones is still "one of the most poorly under-stood geological processes" (Houseknecht, 1989), anduntil our understanding significantly improves, thesemodels are one of the few means by which we canobtain an estimation of expected porosity reductionfrom normal compaction.

Slightly higher porosity values than those obtainedwould also be expected due to the mild silica cementa-tion of the Ciletuh sandstones (Table 5), a factor notaccounted for in the calculations used (see Appendix1). Modest silica cement can actually help reduceporosity loss from compaction by giving the rockgreater" strength.

b. TectonicCompaction

Tectonic stress resulting from subduction-relatedcompression is believed responsible for the compac-tional porosity loss not accounted for by normal burialcompaction (i.e. from overburden stress). The Ciletuharea contains a number of signs of compressionaltectonism such as faulting, tectonized beds and possibletectonic breccia and rotated blocks.

The episode of tectonic compaction probably occurredduring the Middle to Late Miocene, coinciding with aperiod of uplift and compression which resulted in thedevelopment of east-west-trending folds and reversefaults throughout Southwest Java. This has beenattributed to northward subduction of the IndianOcean Plate (Baumann et aI, 1972; Hamilton, 1979;Daly et aI, 1991).

Scenarios for Development of a Viable Reservoir

a. Submarine Fan Reservoir Properties

The Ciletuh Formation quartzose sandstones oncepossessed excellent reservoir properties with highpermeability and primary porosity ranging from25-40%. Sand-rich suprafan lobes, similar to theinterpretation of the Ciletuh fan, typically haveexcellent lateral and vertical communication due to

common stacking and cross-cutting of individual flows.This is similar to the reservoir communication seenin braided fluvial channal deposits, however, fandeposits such as these tend to lack depositionalpermeability barriers such as claystone or shaleinterbeds (Shanmugam and Moiola, 1991).

Even though the Ciletuh sandstones have verylow reservoir potential due to heavy compactionand cementation, there is no reason why a highquality reservoir could not be preseved in similardeposits under more favorable tectonic or diageneticcircumstances. To illustrate this point, the followingdiscussion briefly presents several scenarios throughwhich a viable reservoir could be developed orpreserved (Figure 23).

b. Non-Compressive Tectonic History

In the previous section it was postulated that as much as14% of the Ciletuh Formation porosity could have beenpreserved if the sandstones had not been subjected tolate stage tectonic compaction associated withsubduction stress; a feat easily accomplished bydeposition in a different tectonic setting (Figure 23A).Suprafan lob~ or radial fans can develop in a widerange of tectonic settings including continentalborderlands, forearc basins and backarc basins (Nelsonand Nilsen, 1984). Deposition in an active convergentmargin-setting does not also necessarily destine apotential fan reservoir to destruction by tectoniccompaction. With all things considered, the tectoniccompaction postulated in the Ciletuh Area is probablymore the exception than the rule.

c. Subsurface Secondary Porosity Development

Even if most of the sandstone primary porosity weredestroyed due to compaction and cementation, it wouldstill be possible to create major secondary porosityby dissolution of chemically unstable sandstonecomponents such as feldspar, lithic grains andcarbonate cements. A plausible mechanism couldinvolve carboxylic acids released from adjacentkerogen-rich lithologies by thermal maturation

(Surd am et aI, 1989). The source of carbon dioxide orcarboxylic acids could either be an organic-rich, deepmarine source rock of similar age which surrounds thefan sandstone; or alternatively an older, underlyingkerogen-rich rock unit (see Figure 23B).

Interestingly, the calculated maximum burial depthof the Ciletuh Formation sandstones would justbarely place them within the temperature window forgeneration of carboxylic acids. Some subtle porositytextures observed in thin section suggest there mayhave been a very minor episode of deep secondaryporosity development (Figure 22), though this isuncertain.

d. Near-Surface Secondary Porosity Development

Re-exposure of low porosity, once deeply buriedsandstones can result in the introduction of meteoricfresh-water into the subsurface. This is capable ofdissolving feldspar, carbonates and other unstableminerals (Bjorlykke, 1983). This process is currentlytaking place within the Ciletuh Formation, and isbelieved responsible for nearly all the porosity seen inthe outcrop thin section samples (see lower portionFigure 22). Given sufficent time and the propertectonic circumstances, the Ciletuh Formation couldconceivably be re-buried with greatly enhancedporosity (Figure 23C).

EXPLORATION POTENTIALFANS IN INDONESIA

OF SUBMARINE

Sand-rich submarine fan deposits can be importantexploration targets, but have yet to be widely exploitedwithin Jndonesia. Examples of commercial oil and gasproduction from submarine fan reservoirs elsewhere inthe world are numerous. A few of these include thePaleocene to Eocene Forties, Montrose and FriggFields in the North Sea; Eocene sandstones in theChicontepec region of Mexico; Cretaceous toOligocene sandstones of the Campos Basin, Brazil; andthe Pliocene oil fields of Southern California (North,1985).

Submarine fan and other deep marine sandstonedeposits such as trench wedges and debris aprons tendto more frequently accumulate during geologicalperiods of low sea level stand (Nelson and Nilsen, 1984;North, 1985). This fact inevitably strengthens thepossibility of locating deep marine sandstone reservoirsin Cenozoic strata of Early Tertiary and Late Oligoceneage throughout Indonesia; and also thQse of Triassic toEarly Jurassic age within Eastern Indonesia. Deepmarine sandstones, however, could be developedduring many intervals of the Cenozoic within

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Indonesia, irrespective of eustatic sea level becauseof the relatively high degree of tectonic activitythroughout most of this period.

The fan deposits are there. The exploration challengewill be in locating those with both high reservoir qualityand an association with rich source lithologies. Quartz-rich fans deposited in small, restricted basins typicallypossess the highest potential for petroleum reservoirdevelopment (Howell and Normark, 1982; Nelson andNilsen, 1984).

The hydrocarbons of many of the world's prooucingdeep marine fan reservoirs were derived fromassociated marine source rocks, accumulated under lowcirculation, dysaerobic conditions, or in areas withpronounced upwelling. So far very few good marinesource rocks have been found within Indonesia. This isespecially true in Western Indonesia, where mostsuccessful exploration has been within rifted backarc basins filled with non-marine and shallowmarine reservoir and non -marine source lithologies(Robinson, 1987). Most deep marine shales in WesternIndonesia have been found to be either low in totalorganic carbon due to deposition in well-circulatedbasins, or immature due to a combination of young age,shallow burial and/or low geothermal gradient.Because of these marine source rock problems, thegreatest potential in Western Indonesia may be fromsubmarine fan sandstones tectonically juxtaposed withnon-marine source rocks.

The far greater potential lies in Eastern Indonesiawhere more frequent development of organic-richmarine source rocks is suspected (Robinson, 1987).The older age of the sequences also increases thechances of charging young submarine fan deposits fromsignificantly older source rocks.

Many, if not most, Cenozoic Indonesian submarinefan deposits will unfortunately be dominated byvolcaniclastic sediments. As illustrated by the CiletuhFormation volcanic sandstones, volcaniclastics typicallyhave low reservoir potential due to high instabilityof the sediments. Some exceptions are possible as.evidenced by the productive, mostly fluviatile,volcaniclastic Jatibarang Field in West Java.

So far few productive sandstone intervals withinIndonesia have been identified as deep marine turbiditeor fan deposits (e.g., portions of the Baong Formation;Mulhadiono et aI, 1982). Similar to some of the earlyexploration problems experienced in the North Sea, itwould not be surprising to learn if an active field inIndonesia had some production from a deep marinesandstone horizon which has been misinterpreted as

140

deltaic deposits. Only future exploration will disclosethe true potential of deep marine sandstones within theregIOn.

CONCLUSIONS

The Eocene Ciletuh Formation clastics are

interpreted as a sand-rich submarine fan complex.

Deposition is believed to have been in a series ofparallel slope grabens oriented perpendicular toslope.

Submarine fan deposition with the Ciletuh Areamay have been result of Eocene initiation of theCimaridiri Fault Zone.

Two distinct lithofacies are present in the CiletuhFormation; a quartzose facies and a volcaniclasticfacies.

Sediments are interpreted to have been sourcedfrom Mesozoic Sunda Shield continental crust andLate Cretaceous subduction complex areas lying tothe north, with lesser volcanics supplied fromnearby Eocene volcanic activity. Local submarineuplifts of subduction complex basement are alsobelieved to have supplied some pebbles and brecciapartly composed of Pre-Tertiary lithologies.

Significant Eocene volcanic activity within and/ornearby the Ciletuh Area is indicated.

The absolute age of some of the Ciletuh Formationmay possibly be defined by the narrow overlap ofForam Zone P14 and Nannofossil Zone NP16 (44-45 Ma).

The Ciletuh Formation sandstones have verylow reservoir potential due to near completedestruction of originally high primary porosity bycompaction and cementation.

Tectonic compaction associated with Middle toLate Miocene subduction compression is believedresponsible for destruction of a large percentage ofthe Ciletuh Formation sandstone porosity.

ACKN 0 WLEDG MENTS

We would like to thank Pertamina for permission topublish this paper, and the management of P.T.Robertson Utama Indonesia (RUI) and AtlanticRichfield Indonesia Inc (ARII) for their generoussupport throughout the research and preparation of thispaper, with special thanks to Mr. David Flett of RUI

and Mr. Gene Richards of ARII. We also wish to thank

colleagues who assisted with crucial support analysesincluding Dr. Alaa Baky (nannofossil), Dr. AntoinettePollaupessy (palynology) and Dr. Andrew Livsey(geochemistry) of RUI and Dr. Stephen Bergman andDr. James Talbot (K/Ar dating) of ARCO Oil and Gas,PIano, Texas. Thanks are also due to Dr. RobertMorley and Dr. Paul Watton for palynological support,Dr. Jan Bon for micropaleontological support, Dr.Anthony Barber and Dr. Tim Charlton for melangediscussions, Dr. Peter Butterworth and Dr. Tor Nilsenfor fan discussions, Mr. Hartanto for drafting support,and Ms. Rina Junu Chaier for typing the manuscript.

REFERENCES

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Baumann, P., P. de Genevraye, L. Samuel, Mudjitoand Sri Sajekti, 1973. Contribution to the geologicalknowledge of South West Java, Proceedings ofIndonesian Petroleum Association Second Annual

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Baumann, P., H. Oesterle, Suminta and Wibisono,1972. The Cenozoic of Java and Sumatra, Proceedingsof Indonesian Petroleum Association First AnnualConvention, p.31-42.

Van Bemmelen, R.W., 1949. The Geology ofIndonesia, Government Printing Office, The Hague,2 vols. + maps.

Beard, D.c. and P.K. Weyl, 1973, Influence ofTexture on Porosity and Permeability of UnconsolidatedSand, Bulletin of American Association of PetroleumGeologists, 57:349-369.

Bjorlykke, K.B., 1983. Diagenetic Reactions inSandstones, in Parker, A. and B.W. Sellwood (eds),Sediment Diagenesis, D. Reidel, Holland, pp.169-214.

Bolli, H.M., J.B. Saunders and K. Perch-Nielsen,1985. Plankton Stratigraphy, Cambridge UniversityPress, Cambridge, 1O32p.

Cas, R.A.F. and J.V. Wright, 1987. VolcanicSuccessions: Modern and Ancient, Allen & Unwin,London, 528p.

Cowan, D.S. 1985. Structural Styles in Mesozoic andCenozoic Melanges, Western Cordillera of North

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Daly, M.C, M.A. Cooper, I. Wilson, D.G. Smith andB.G.D. Hooper, 1991. Cenozoic Plate Tectonics andBasin Evolution in Indonesia, Marine and PetroleumGeology 8:1-21.

Dickinson, W.R., 1985. Interpreting ProvenanceRelations from Detrital Modes of Sandstones, in Zuffa,G.G. (ed), Provenance of Arenites, D. Reidel, Boston,pp.333-361.

Dickinson, W.R. and R.V. Ingersoll, 1990. Physio-graphic Controls on the Composition of SedimentsDerived from Volcanic and Sedimentary Terrains onBarro Colorado Island, Panama-Discussion, J.Sedimentary Petrology 60:797-798.

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Folk, R.L., 1974. Petrology of Sedimentary Rocks,Hemphill Publishing, Austin, 182p.

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Houseknecht, D.W., 1989. Assessing the RelativeImportance of Compaction Processes and Cementationto Reduction of Porosity in Sandstones: Reply, Bulletinof American Association of Petroleum Geologists73:1277-1279.

Howell, D.G. and W.R. Normark, 1982. SubmarineFans, in Sandstone Depositional Environments,Scholle, P.A. and D. Spearing (eds.), AAPG Memoir31, pp.365-404.

Letouzey, J., P. Werner and A. Marty, 1990. FaultReactivation and Structural Inversion. Backarc and

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Link, M.H., and TH. Nilsen, 1980. The RocksSandstone, An Eocene Sand-rich Deep-Sea FanDeposit, Northern Santa Lucia Range, California, J.Sedimentary Petrology 50:583-602.

Link, M.H., R.L. Squires and I.P. Colburn, 1984.Slope and Deep-Sea Fan Facies and Paleogeography ofUpper Cretaceous Chatsworth Formation, Simi Hills,California, Bulletin of American Association ofPetroleum Geologists 68:850-873.

Longiaru, S., 1987. Visual Comparators for Estimatingthe Degree of Sorting from Plane and Thin Section, J.Sedimentary Petrology 57:791-794.

Lowe, D.R., 1982. Sediment Gravity Flows II,Depositional Models with special Reference to theDeposits of High-Density Turbidity Currents, J.Sedimentary Petrology 52:279-298.

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Martodjojo, Soejono S. Suparka and S. Hadiwisastra,1978. Status Formasi Ciletuh Dalam Evolusi JawaBarat, Geologi Indonesia, 1.5, No.2, p.29-38.

Middleton, G.V., and M.A. Hampton, 1976.Subaqueous Sediment Transport and Deposition ofSediment Gravity Flows in Stanley, D. G., andD.J. Swift (eds), Marine Sediment Transport andEnvironmental Management, John Wiley, New York,p.197-217.

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142

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APPENDIX 1

Formula used for Sandstone Porosity Prediction (afterScherer, 1987)

Porosity = 18.60 + (4.73 x In quartz) + (17.37/sorting) - (3.8 x depth 103) - (4.65 xIn age)

Where,

Porosity = Estimated Porosity

Quartz = Detrital quartz in % of solidrock volume

Sorting = Trask sorting coefficient

Depth = Depth in meters

Age = Age in million years

The volume percent of authigenic cement pointcounted from thin section was subtracted from the

estimated porosity. Calculations were only performedon samples containing little or no ferroan-calcitecement.

TA

BL

E1

SAM

PLE

LO

CA

TIO

NS

AN

DA

NA

LY

SES

+:.

w

Ana

lyse

sSa

mpl

eL

ocat

ion

Fonn

atio

nL

ithol

ogy

Thi

nFo

ram

Nan

no-

Paly

nolo

gyK

JAr

Sect

ion

Mic

ropa

leo

Foss

ilA

2eD

atiD

2C

LH

-90-

OO

1AC

iletu

hH

eadl

and

Cile

tuh

Sst

xC

LH

-90-

001B

Cile

tuh

Hea

dlan

dC

iletu

hSe

tctd

Pebb

les

xx

CL

H-9

0-00

2C

iletu

hH

eadl

and

Cile

tuh

Car

boSs

tx

xC

LH

-90-

OO

3C

iletu

hH

eadl

and

Cile

tuh

Sst

xC

LH

-90-

004

Cile

tuh

Lg.

clif

fC

iletu

hSs

tx

CL

H-9

0-00

5C

iletu

hC

iletu

hC

arbo

Sst

xx

CL

H-9

0-Q

06S.

Leg

onPa

ndan

Cile

tuh

Con

glom

erat

ex

CL

H-9

0-00

7A

S.L

egon

Pand

anC

iletu

hC

ongl

omer

ate

xC

LH

-90-

OO

7BS.

Leg

onPa

ndan

Cile

tuh

Lst

Pebb

le(S

kele

tal

Pkst

)x

CL

H-9

0-'0

08S.

Leg

onPa

ndan

Cile

tuh

Sst

xx

CL

H-9

0-00

9N

.L

egon

Bed

ogPa

leog

ene?

Tec

toni

zed

Lst

(Pla

nkto

nic

Fora

mW

kst)

xx

CL

H-9

0-D

I0L

egon

Bed

ogC

itire

mSp

illiti

cB

asal

tx

CL

H-9

0-01

1L

egon

Bed

ogC

iletu

h?

Indu

rate

dSs

tx

CL

H-9

0-01

8Pu

lau

Got

orC

itire

mSp

illiti

cB

asal

tx

CL

H-9

0-D

19Pu

lau

Man

dra

Cile

tuh

?V

olca

nicl

astic

Sst

xx

CL

H-8

9-12

1C

iletu

hB

each

Cile

tuh

Shal

ex

xC

LH

-89-

122

Cile

tuh

Bea

chC

iletu

hSh

ale

xx

CL

H-9

1-00

1U

jung

Bat

unun

ggal

Cile

tuh

Sst

xx

CL

H-9

1-00

2U

jung

Bat

unun

ggal

Cile

tuh

Slty

Sst

xx

xx

CL

H-9

1-00

3U

jung

Bat

unun

ggal

Cile

tuh

Cla

ysto

nex

xx

xC

LH

-91-

0Q4

Uju

ngB

atun

ungg

alC

iletu

hSs

tx

xC

LH

-91-

Q06

Cim

arin

jung

Wat

erfa

llJa

mpa

ngA

mph

ibol

eA

ndes

itic

Tuf

fx

xC

LH

-91-

OO

7C

imar

inju

ngW

ater

fall

Jam

pang

Am

phib

ole

And

esiti

cT

uff

xx

xC

LH

-91-

OO

8Pa

sir

Hau

rC

iletu

hSs

tx

CL

H-9

1-00

9Pa

sir

Hau

rC

iletu

hSs

tx

xx

CL

H-9

1-D

1OG

unun

gN

yalin

dung

Cile

tuh

Vol

cani

clas

ticSs

tx

xx

xC

LH

-91-

D11

Gun

ung

Ran

gkon

gC

iletu

hV

olca

nicl

astic

Sst

xC

LH

-91-

012

Pula

uH

adji

Cile

tuh

Vol

cani

clas

ticSs

tx

xx

xC

LH

-91-

D13

S.C

iletu

hB

each

Cile

tuh

Tuf

face

ous

Sst

xx

xC

LH

-91-

D14

Cile

tuh

Bea

chC

iletu

hC

lays

tone

xx

xC

LH

-91-

D16

Cile

tuh

Bea

chSc

aly

Cla

y?

Phyl

lite

xx

xx

CL

H-9

1-D

17L

egon

Bed

ogC

itire

m?

Spill

itic

Bas

alt

xC

LH

-91-

018

S.L

egon

Pand

anC

iletu

hB

asal

tPe

bble

sx

xC

LH

-91-

019

S.L

egon

Pand

anC

iletu

hC

ongl

omer

ate

xC

LH

-91-

D20

S.L

egon

Pand

anC

iletu

hSa

ndst

one

xC

LH

-91-

021

S.L

egon

Pand

anC

iletu

hG

rave

llySa

ndst

one

xC

LH

-91-

D22

Pula

uG

otor

Citi

rem

.Sp

illiti

cB

asal

tx

CL

H-9

1-D

23E

.Pu

lau

Kun

tiB

each

Cile

tuh

Tuf

face

ous

Shal

ex

xx

x

TA

BL

E1

SAM

PLE

LO

CA

TIO

NS

AN

DA

NA

LY

SES

(Con

tinue

d)

- ~ ~

Ana

lyse

s

Sam

ple

Loc

atio

nFo

nnat

ion

Lith

olog

yT

hin

Fora

mN

anno

-Pa

lyno

logy

KIA

r

Sect

ion

Mic

ropa

leo

Foss

ilA

reD

atiD

l!

CL

H-9

1-Q

24E

.Pu

lau

Kun

tiB

each

?B

recc

iax

xx

CL

H-9

1-Q

25Po

int

N.

ofP.

Kun

tiC

itire

m?

Porp

hyri

ticA

ndes

itex

x

CL

H-9

1-Q

26E

.Pu

lau

Kun

tiB

each

Cile

tuh

Vol

cani

clas

ticSs

tx

xx

CL

H-9

1-Q

27Pu

lau

Kun

tiC

itire

m?

Coa

rse

And

esite

?x

CL

H-9

1-Q

28W

.Pu

alu

Kun

tiB

each

?B

recc

iax

CL

H-9

1-Q

29G

unun

gB

adak

Gun

ung

Bea

sU

ltram

afic

x

CL

H-9

1-Q

30Pu

lau

Dah

euC

iletu

hT

uffa

ceou

sC

arbo

nate

Mud

ston

ex

xx

x

CL

H-9

1-Q

31Pu

lau

Dah

euC

iletu

hV

olca

nicl

astic

Sst

xx

CL

H-9

1-Q

32Pu

lau

Dah

euC

iletu

hT

uffa

ceou

sSh

ale

xx

xx

CL

H-9

1-Q

33Pu

lau

Dah

euC

iletu

hV

olca

nicl

astic

Sst

x

CL

H-9

1-Q

34Pu

lau

Dah

euC

iletu

hV

olca

nicl

astic

Sst

x

CL

H-9

1-Q

3SA

Tan

jung

Kar

angj

ahe

Jam

pang

?V

olca

nicl

astic

Sst

xx

x

CL

H-9

1-Q

3SB

Tan

jung

Kar

angj

ahe

Jam

pang

?V

olca

nicl

astic

Sst

xx

x

CL

H-9

1-Q

36C

iletu

hB

each

CH

erub

Pyri

te-R

ich

Sst

xx

xx

CL

H-9

1-Q

37C

iletu

hB

each

Cile

tuh

Shal

ex

xx

CL

H-9

1-Q

40C

iletu

hB

each

Cile

tuh

?B

recc

ia?

x

CL

H-9

1-Q

41C

Het

uhB

each

Cile

tuh

Shal

ex

x

CL

H-9

1-Q

42C

Het

uhB

each

Cile

tuh

?A

ltere

dpo

rphy

ritic

And

esite

Pebb

lex

xx

CL

H-9

1-Q

44C

Het

uhB

each

Cile

tuh

?Pu

mac

eous

Lap

illi

Tuf

fx

CL

H-9

1-04

SC

iletu

hB

each

Cile

tuh

?V

olca

nic

Bre

ccia

x

CL

H-9

1-Q

47C

iletu

hB

each

Oile

tuh

?Ss

tx

xx

x

CL

H-9

1-Q

49O

mba

kT

ujuh

Bay

Citi

rem

?T

uffa

ceou

sC

lay

Len

sx

CL

H-9

1-Q

S3S.

Leg

onPa

ndan

Cile

tuh

Side

rite

Cla

sts

x

CL

H-9

1-Q

S3A

Pula

uK

unti

Bea

chC

iletu

h?

Num

mul

itic

Lst

Cla

stB

recc

iax

x

CL

H-9

1-Q

S3B

Pula

uK

unti

Bea

ch?

Mat

rix

Bre

ccia

?x

x

CL

H-9

1-Q

S4A

Clif

fW

.of

Cim

arin

jung

Jam

pang

Am

phib

ole

And

esite

(Cla

st?)

x

CL

H-9

1-Q

S6Pu

lau

Ram

etu

Citi

rem

?Po

rphy

ritic

Bas

alt?

xC

LH

-91-

QS9

W.

Pula

uK

unti

?B

recc

iaSs

tC

last

x

CL

H-9

1-06

0APu

lau

Man

dra

Cile

tuh

Vol

cani

cSs

tx

CL

H-9

1-06

1K

aran

gH

adji

Cile

tuh

Vol

cani

cSa

ndst

one

x

CT

H-9

I-O

O2A

N.

Uju

ngSo

dong

Bar

atG

unun

gB

eas

Gab

bro

xx

CT

H-9

1-O

O3A

Uju

ngB

atun

ungg

alC

iletu

hC

arbo

Sst

x

CT

H-9

1-00

4AU

jung

Bat

unun

ggal

Cile

tuh

Car

boSs

tx

CT

H-9

1-O

OS

AN

.U

jung

Song

ong

Bar

atC

iletu

hSs

tx

x

TABLE 2

FORAMINIFERAL SPECIES LIST

145

KEY: 0 rare, v few, + common, A abundant

CLH CLH CLH CLH CLH CTH CTH CLHSamnle No. 003 004 014 037 047 005A 004A 010

PLANKTONIC FORAMINIFERA

Globigerina spp. v 0 0 v

Globogerina tripartita 0 0

Globorotalia centralis 0 v

Indet. planktonic foram. 0

Globigerina galavisi 0

Globorotalia (M) spinulosa 0

CALCAREOUS BENTHONIC.,

FORAMINIFERA

Globorotalites spp. v

Anomalinoides spp. 0

Gyroidina spp. 0

Cibicides spp.jHeterolepa spp. 0 0

Rotalia spp. 0 + 0 0

Nodosaria spp. 0 v

Elphidium spp. 0

Baggina philippinensis 0

Reusella spinulosa 0Bolivina alata 0

Uvigerina gallowayi v

Spiroplectamina acuta 0Lenticulina intennedia vARENACEOUS FORAMINIFERA

Cyclammina spp. 0

Haplophragmoides spp. 0 0 0 0

Bathysiphon spp. 0

Textularia sp. 0LARGER FORAMINIFERA

lndet. larger foram 0 0

Amphistegina spp. 0 0

MISCELLANEOUS

Shell debris +

146

TABLE 2 (Cont'd)FORAMINIFERAL SPECIES LIST

..

CLH CLH CLH CLH CLH CLH CLH CLH CLH CLH

SamDle No. 013 023 030 032 033 012 024 060A 061 053A

PLANKTONIC FORAMINIFERA

Globigerina spp. 0 0 A v v v v

Globigerina tripartita v 0 0

Globigerina centralis 0 0

Globorotalia cerroazulensis 0 v 0 0

Globigerina prasaepsis 0

Globigerinoides spp. v

Globorotalia spp. 0 0 v

Globigerinita dissimilis v 0 0

Globorotaloides carcocellensis 0

.Orbulina universa 0

Globigerina menardii 0

Globigerinoides sacculi fer 0

Globigerinoides trilobus 0

Neogloboquadrina acostaensis 0

Globoquadrina altispira 0

CALCAREOUS BENTHONIC

FORAMINIFERA

Cibicidesspp. 0

Gyroidina soldanii 0 0 0

Lenticulina spp. 0 0 0

.planulina wuellerstorfi 0

Gyroidina spp. 0 0

Callais auriculus 0

Globocassidulina globosa v

Globorotalites spp. v v v

Heterolepa praecincta 0

Eponides spp. v v v

Bulimina spp. v

Anomalinoides spp. 0 0

Rotalia spp. 0

ARENACEOUSFORAM

Haplophragmoides spp. 0 0 0 v

Bigenerina nodosaria 0 0 0

Reophax spp. 0

Textularia pselldogrammen 0

Bathysiphon spp. 0

LARGER FORAMINERA

Cycloclypeus spp. 0

Operculina spp. +

Amphistegina lessonii v

Operculina ammonoides 0

Nummulites spp. +/A

Assilinia spira 0

MILIOLID

Quinqueloculina spp. 0

147

TABLE3

NANNOFOSSIL SPECIES LIST

KEY: 0 rare, v few, + common, A abundant

CLH CLH CLH CLH CLH CLH

Samole No. 003 014 010 030 032 012

Species

Reticulofenestra sp. + 0 0 0

Cyclicargolithus floridanus v/+ 0 A A 0Reticulofenestra d. stavensis v

Discoaster sp. (6 armed) 0 a/vCalcidiscus sp. v

Sphenolithus sp. v A A 0

Sphenolithus morifonnis 0 0 0 + v 0Discoaster deflandrel 0 0 0

Reticulofenestra d. dictyoda 0

Helicosphaera euphratis 0 0

Sphenolithus spiniger a/v 0 v

Coccolith us pelagicus 0 0 0 v 0 0

Dictyococcites gelida 0

Reticulofenestra d. umbilica v/oDiscoaster sp. (5 armed) 0 0 a/vDiscoaster d. tanii 0 0Cribrocentrum reticulatum 0 0 0

Cyclicargolithus d. abisectus 0

Coccolith us eopelagicus 0 0 0

Ericsonia d. fonnosa 0Reticulofenestra stavensis 0 0Cyclicargolithus abisectus v v +/v 0Indet. fossils 0

Sphenolithus pseudoradians .0

Pemma papillatum 0Helicosphaera salebrosa 0Dictyococcites bisectus 0 0 0Sphenolithus cf. spinifer + +

Thoracosphaera sp. 0 0 0

Thoracosphaera saxer 0 0Dictyococcites sp. 0 0Pemma sp. 0

148

TABLE 4

PALYNOLOGICAL SPECIES LIST

GYMNOSPERMS

Bisaccates (undift)Inaperturopollenites limbatus (Rw) 1Podocarpus polystachyus type 1

1

1

CLHCLHCLHCLHCLHCLHCLHCLHCLHCLHCLHCLHCLHCLH CTHSamvle No. 002 003 007 012 014016 023 030 032 036 037 041 042 047 003B

MARKER TAXAFlorschuetzia trilobata 1Florschuetzia trilobata (robust) 1Florschuetzia sp. 1

MANGROVE TAXAZonocostites ramonae 1 1 1 1Spinizonocolpites echinatus 1 1 1 1

S. echinatus (long spined) 1 1 1

FRESHWATER TAXA

Cyperaceae 2

Myrtaceidites sp. 1Echitriporites sp. 1

Meliaceae / Sapot'lceae 3 1 1 1

Ilexpollenites sp. 1

Palmae (undiff.) 1 1Dicolpopollis spp. 4 1 1 1 9Dicolpopollis malesianus 1

Psilatricolporites spp. 1 1

Psilatricolpites sp. 1 5Retitricolporites spp. 1Triporites (undiff.) 2 5 3 1 2 1 1 2Lanagiopollis nanggulanensis 1

Proxapertites spp. (psilate) 1 1Proxapertites cursus 1Stemonunls type 1Iguanura type 1Pterocarya type 1

149

TABLE 4 (Cont'd)PALYNOLOGICAL SPECIES LIST

Numbers indicate number of specimens per sample.

ClliClliClliClliClliClliClliClliClliClliHClliClliCllicrHSamDleNo. 002 003 007 012 014 016 023 030 032 036 037 041 042 047 003B

-

PTERIDOPHYTES

Laevigatosporites spp. 3 6 10 2 17 8 5 4 3 1 10

Vermcatosporites spp. 3 1 1 1 1 3 2 1 1 1

Vemlcatosporites usmensis 4 2 2 2 3 2 1 3

Monolete spores(undiff.) 1 5 1 2

Leiotriletes spp. 3 2 2 1 3 2

Vermcosisporites spp. 1 1

Trilete spores (undiff.) 1 3. 1 6 4 2

Pteris (smooth) 1

Deltoidospora spp. 2 5

Acrostichllln type 2 3 2 3Baclliatisporites sp. 1

OTHERS

Spiniferitesramosus group 1 1

Dinocysts 1 2 1

Concentricystescirculus 1 1

Algal cysts 2 2 2

Chitinous foram lining 1

Total: 29 20 1 34 13 31 28 8 18 4 12 6 7 43

150

TABLE 5AVERAGE COMPOSITION OF QUARTZOSE LITHOFACIES SANDSTONES

=============================================================================

AVERAGEI

(%)

RANGE2(%)

DETRITAL GRAINS

Monocrystalline Quartz

Polycrystalline Quartz3Plagioclase FeldsparPotassium FeldsparChert

Sedimentary Rock FragmentsVolcanic Rock FragmentsMetamorphic Rock FragmentsPlutonic Rock FragmentsPlant / Coal FragmentsMicaCalcareous BioclastsGlauconite

MATRIX

Detrital Clay4

41

161355621

<1<1

1<1

27 - 55

5 - 31Tr - 5Tr - 7

1 - 171 - 121 - 10

Tr - 60 - 20 - 20 - 20 - 60 - 1

4 Tr - 8

CEMENTS AND REPLACEMENTS

Ferroan Calcite

Quartz OvergrowthsKaolinite

Chlorite4

pyrite5Iron Oxide4

Thin Section Porosity

431

1

2

1

0 - 20Tr - 60 - 6

Tr - 8Tr - 43

Tr - 5

3 Tr - 7

lEased on point counts of 17 thin sections.2Tr = Trace

3Includes metaquartzite.4Due to clay weathering, it was not always possible to fully differentiate matrix clay, authigenicchlorite clay and oxidized clay.5High pyrite only seen in sample CLH-91-047.

151

TABLE6AVERAGECOMPOSITIONOFVOLCANICLITHOFACIESSANDSTONES

=========================================================

AVERAGE!(%)

RANGE3(%)

DETRITAL GRAINS

lBased on point counts of 6 thin sections.

2Due to alteration it was not always possible to distinguish authigenic chlorite from tuffaceousmatrix.

3Tr=Trace

VolcanicRockFragments 70 61 - 80SedimentaryRockFragments 4 Tr - 11PlagioclaseFeldspar 12 8 - 19PotassiumFeldspar <1 0 - 1Quartz 1 0 - 3Chert <1 0 - TrPyroxene 1 Tr - 2Plant Fragments <1 0 - 1Mica <1 0 - 1CalcareousBioclasts 2 0 - 6Glauconite <1 0 - 1

MATRIX

TuffaceousClay2 4 0 - 4

CEMENTSAND REPLACEMENTS

Calcite 1 0 - 4Ferroan Calcite <1 0 - 2Chlorite2 5 0 - 11Pyrite <1 Tr - 2Zeolite 2 0 - 7

Thin SectionPorosity 1 0 - 3

152

TABLE 7

SUMMARY OF POTASSIUM / ARGON RADIOMETRIC DATING ANALYSES

*WRMS = Whole Rock Magnetic SeparateI'-

SampleNo. Location Formation/ Lithology Analyzed Age- Unit Phase (MA)

CLH-90-001B CHerub CHetuh Granitic Plagioclase 134.0 + 3.0Headland Pebble

CTH -91-OO2A Ug. Sodong Gunung Beas Gabbro Plagioclase 56.0 ..:t 2.3Barat

CTH-91-O02A Ug. Sodong Gunung Beas Gabbro WRMS* 50.9 + 2.1Barat

CLH-91-010 Gg. CHetuh Volcaniclastic Plagioclase 33.9 ..:t 2.3Nyalindung Sandstone/Tuff

CLH-91-010 Gg. CHetub Volcaniclastic WRMS* 50.1 + 2.1

Nyalindung Sandstone/Tuff

CLH-91-18B CHetuh CHetuh Basalt Pebble Plagioclase 89.6..:t 3.0Headland

CLH-91-O25 Pulau Kunti Citirem ? Quartz Plagioclase 22.4 ..:t 1.5Andesite

153

TABLE 8

DET AIL OF QUARTZOSE SANDSTONE LITHOFACIES LITffiC ROCK FRAGMENTS AND

ACCESSORY GRAINS!

I. Lithic Rock Fragments

A. Chert (radiolarian/spicularchert, meta-chert, chalcedonyand common chert).

B. Volcanic Rock Fragments (mostly altered basalt, plagioclase microlite-richandesitic crystal/vitric tuff, lesser chloritized tuff, rare rhyolite and possibledacite ?).

C. SedimentaryRock Fragments- Siliciclastic sedimentary rock fragments (slightly metamorphosed shale,

argillaceous siltstone, and sandstone; heavily compacted fine to mediumgrained subarkose; and local intrabasinal claystone, siltstone andsandstone).

- Carbonate rock fragments (iron oxide-stained sideritic and dolomiticmud~tone,some reworked sideritic/dolomiticconcretions and nodules; redalgal/skeletalwackestone/packstone;and heavily abraded, redeposited coralclasts).

D. Metamorphic Rock Fragments (low-grade quartz-mica schist, muscovite-phyllite, chlorite-phyllite, slate and rare serpentinite).

E. Plutonic Rock Fragments (including coarsely crystalline granite, granodiorite,graphic granite, diorite and possible monzonite ?).

II. Accessory Grains

A. Coalifiedplant fragmentsand redepositedcoal

B. CalcareousBioclasts(large benthonic forams (nummulitesand operculinids),gastropods, thick-walled pelecypods, coral, echinoderm fragments and rarebryozoans, red algae, smallbenthonic forams and planktonic forams.

C. Mica (mostly muscovite, rare chlorite and biotite).

D. Heavy minerals (mostly dravite tourmaline and zircon; rare clinopyroxene,magnetite, epidote and penninite).

E. Other (glauconiteand phosphateclasts).

IData from thin section, arranged in order of decreasing frequency

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FIGURE 2 - Physiography and Bathymetry of the Ciletuh Area

156

SCALE 1: 100,000 106°~'-0 1 2 :3Km.

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FIGURE 3 - Surface Geology Map of the Ciletuh Area, Southwest Java

157

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FIGURE 4 - Sample Location Map of the Ciletuh Area ( See Table 1 For Detail)

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Oceanic Crustand Associated

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FIGURE 6 - Stratigraphic Synopsis for the Ciletuh Area, S.W. Java

AGE STRATIGRAPHY

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GRANITES AND METAMORPHICS

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6_88

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FIGURE 9 - Ciletuh Headland Measured Sections 1, 2 and 3 (Quartzose Lithofacies)

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32

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A COMMON OXIDIZED

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A/B

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FIGURE 10 - Ciletuh Headland Measured Section 4 : (Quartzose Lithofacies)

18

17

16

15

14

13

12

29

28

27

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164

CILETUH HEADLANDSECTION "5"

( KARANG HEULANG )

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2

B?

3.3 METERS OFTHIN-BEDDEDF-M SANDSTONE-SCHEMATIC DESCRIPTIONDUE TO PARTIALSUBMERGENCE

\RIPPLED VF SST AND SHALE

\.-<'

A:' E- SEED PODS 01>1UPPER SURFACE

B/E

B/E?(C/O?)

RIPPLE'D SANDSTONE-AND SILTY CLAYSTONE

- RARE OXIDIZED BURROWS

,? THIN BEDS. 1-4 em

- NUMMULITICFORAMS- SEED PODS ON UPPER SURFACE

aOVERTURNED SLUMP FOLD

C/D?/F

LARGE PLANT FRAGMENTS

alA

FAULT

B

METERS 0 BASE OF SECT10H COVERED BY RUBBLE

~ I '"I'

I . i ~ I u I ; j ~:_it . ~I.'".a r ~

If/

/=10- ZO M ESTIMATEC'MISSING SECTION BE"-WF'SECTIONS 4 a ~

/

/::::: 90 -IZ0 M ESTIMATEDMISSING SECTION B!':TWEEN

2T10NS 5 a 6

27

3 u,.~",u.t. .'r~....LiLililiW g

B

SECTION PAR T LYINFERRED DUE TOWAVE HAZARD

26

a

B

FIGURE 11 - Ciletuh Headland Measured Section 5, (Quartzose Lithofacies)

25

,~

::~t-_'~22 . .

I -1- '--I--- ~

21r~1- ~20 1 1

alA .,

a

19

18

t.:17

16

15

14

13

loo'~'~~ ~~-=,

""'

,

:' '

14~'~" ,

13 ~~~<~124 v~~:?r ~ I m.MISSING"'

CILETUH HEADLANDSECTION "6"

( S, LEGON PANDAN )

CORRELATIVESECTION SHOWINGLATERAL FACIESCHANGES I"" 50 m

TO N E ALONG STRIKE}

~,,'U':~U

I~I'I,~i~ ,il§.

I'. '! I

en!!!u'"...

TOP NOT EXPOSED

- - ." --.------""~ - -- SCH~"'AT'C11

10~~il~ - __A-- :~~~O~10,~~ \

:~~--~--_/-_:- B

11

A

B

METERS

6~~' ~ ' 6~;$.."';.:~:80V0~ A

5 if'~5fr.;70'=;';;>o~-- - Ji - - - -- --5

~A, ~di.~f~~~

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~

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1 oeD p O'--:,"~ ~~o (. 1BASE SUBMERGED

I~I~I~I~I~I~ ; ~ . ~ ~ t b 3 METERS 0

= :., ". , "",,: ~SECTION ESTIMATED BETWEENSECTION 566

~

SCHEMATIC~~ SCRiPTION

AI'DUE TOTECTONIZATION ,3

- ~ on

o~~.'~~3t§jGI I I I I : ! II t I ~

TOP NOT EXPOSED21

7

20

19

~{i_,18

17" ' .. ' , :', ..' " ::\

~L~',~'L~"'~:iili116

\.,"~~::~-~15

" , .' :z.--..--

:-:-0<-:-

,-.~-'-'~

;~~~. " ,', \

~~ ~.f~\~'--~

7

4

1 -

BASE SUBMERGED

. I . Ii-. ..U .1,.

~~: . ~~r~

FIGURE 12 - Ciletuh Headland Measured Section

Facies (Quartzose Lithofacies)

B?

A

A

B

A/B

A

A/~

A

165

~

SCHEMATICDESCRIPTION -INACCESSIBLEFOR CET~ILECSTUDYI CUFFEXPOSURE I

j

B

- O,-~NT CRAG...::lns

A

B

A

- LIMESTONEC,-AST

B

A

A

6, Channelized

COAL FRAGMErns

166

PULAU KUNTI BEACH SECTION(SOME CONTACTS INFERRED DUE TO TECTONlzATION)

. ~5 . . u~~.~

lliluliliJBreccia ContinuesUp hill section

PULAU DAHEU SECTION( UJUNG KARANGJAHE )

~. u,~ ~II'>u~. . "'.'w1.1'lol~ 5!u~:::

16

15TOP OF SECTION 15 -

14

12

1111D

10 10 -'-

B

9 9

D8

A

7

6

B

c 2

--" D

Cv .

.V METERS 0METERS 0BASE SUBMERGED

~~" . u'.ueIi' .or ~

BASE OF SECTIONNOT EXPOSED

~i ~U"~ . . u:.~.Ii . ~ .or ~

"'"

II'>WU.....

BOULDERBRECCIA(MIOCENE?)

?

TRANSITION IDEBRIS FLOW? ,f

A?

DIG

c

c

c

c

POOR STRUCTUREPRESERVATION

A

FIGURE 13 - Pulau Daheu and Pulau Kunti Measured Sections (Volcanic Lithofacies)

1<1-1 =-::J-"'",::>

13 i I B..

v

7

V6 ...

.-

5

v

4

3

2v - v

FIG

UR

E14

-Sym

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end

For

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sure

dSe

ctio

ns0\ --

.)

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Y:

ST

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UR

ES

:

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YS

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TO

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AR

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DD

ING

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ED

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OR

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ING

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FIG

UR

E15

-San

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ific

atio

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atio

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ajor

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ompo

nent

s(A

fter

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,19

74)

Vol

cani

cF

acie

s

169

20

~

30

50

60

70

80

90

100

1 Includes MetaQuartzite2 Includes All Other Lithic Rock FraQments (VRF, MRF, SRF)

And Labile AccellSory Grains (Micas And Plant FraQments)

3 Includes Silica, Kaolinite And FE-Oxide

FIGURE 16 -Summary of Quartzose Sandstone Lithofacies Petrographic Analyses

.... ", .... "" '" <t CDI

0 '" <t ,...,... "' "" ;; 00 ;;:;.... 0 "" 0 "" 0 0 0 0 8 '" 0 80

0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

I

SAMPLEI I I I I I I I I I I I I I I I I

;;; 0 ;;; ;;; ;;; -;;; 0 ;;; 0 ;;; ;;; 0 0 0 ;;; NAME'" '" ", . '" '" '" '" '"

I I I I I I I I I I I I I I I I I:r :r :r :r :r :r :r :r :r :r :r :r :r :r :r :r....J ....J , ....J ....J ....J ....J ....J ....J ....J >- ....J ....J ....J ....J >- ....J ....JU U U U U U U U U U U U u I u u u u

!t I

T r PEBBLE U">I ..... GRANULEr T I I

0

I

0I I I

V COARSE ::>

r Jt I COARSE ""

T

I

I 11

.,.

I

..I

. . . WEDIUW....

I IT I

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J I ! I . .J. 1 .1. - I FINE U">....

1VFINE :;;

<tSILT IX:

<:>V.WELL

. I . I I I I I I I I I LWELL

IIWOO-wELL

WOOERArE

POOR

V POOR

II

C c I C/O I C/O I C C B B B B L B? !A B ' A A A A ITURBIDITEFACIES

0

10

I,",ONOCRYSTALLINt aUAnTZ

w::E:

40 ::;)...J0>

W...Ja..::E:

(/)

170

10

20

30

40

60

70

80

90

100

FIGURE 17 -Summary of Volcanic Sandstone Lithofacies Petrographic Analyses

.,. ;<; '" 0 ,.., N CT>,.., N

0 0 0 00 0 0 0Co I SAMPLE

CT> '" '" '" '" '" C;; CT>

:i:: :::: NAME...J ...J -' -' -' -, ...JU U U U U U U u

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I I 1 WE DIU"

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I I I I I I I IA B I ? I ? C ? C? IT.O.,O,H "<1"

I.AJ

::>...J0;>

I.AJ50 ...J

c:r(f)

GRAINSIZE

II'~,I

] ~~at

g

171

BOUMA (1962)DIVISIONS

INTERPRETATION

Tep Palite Pelagic Sedimentation

Tef Massive or Graded

TurbiditeFine Grained, LDw Density

Turbidity Current Deposition

Td Upper Parallel Laminae ???

Tc Ripples, Ww.ty orCovoluted Laminae

LDwer Part of

LDwer Flow Regime

Upper Flow RegimePlane Bed

lb Plane Parallel Laminae

Ta Massiv'e, Graded ? Upper Flow Regime

Rapid deposition and

Quick Bed (?)

FIGURE 18A - Idealized Classical Turbidite or Bouma Sequence Showing BoumaDivision Classification (After Middleton and Hampton, 1976)

FIGURE 18B -Summary of Descriptive Turbidite Facies TerminologyUtilized In Study (Modified After Mutti and RicciLucchi, 1972 ; and Shanmugan and Moiola, 1991)

FACIES LITHOLOGY BEDDING FEATURES APPROX.%IN CILETUHHEADLANDSECTION

Conglomerate, Thick,Irregular, Channel Fill, 30-35%

ACoarse Sandstone Amalgamated Abrupt Lateral Changes,Poor Sorting Scouring, Imbricate

Pebbles

Coarse to Thick, Lenticular, Channel Fill, More 45-55%

BMedium Sandstone Wedging,Subtle Lateral Continuity,Moderately Sorting Grading Parallel Undulating

Laminations,Fluidization Structures

Medium to Medium, Complete Bouma 5 -10 %

C FineSandstone Continuous Sequence (Ta-e)MinorShale,WellSorted

Fine to Very Fine Thin, Remarkably BoumaSequence 1 -2 %

D Sandstone, Siltstone, Continuous,Parallel WithBaseAndShale (Ta) MissingWellSorted

E Sandstone, Thinto Medium BedsWithSharp 5 -10 %Mudstone Irregular, Wavy to Contacts, Sand

Lenticular Lenses

F Complex Deformed, Chaotic Slumpsand Slides 2-3%

GShale, Marl Laminated, Homogeneous Not Present

Remarkably Continuous, TextureParallel

~\-

\)~\

p.\,.

.~\,.

.p.\"

p.~~

~p.\c

,rr

.~\"

,\,,~

s~O

o~\.-

..~~Q

"p.~

~~~

,,~r-

;,s

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r~

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~~~

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~\,..

~~~~

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~~~ ~~

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- -J tV

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,-~O

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~~

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~~>

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..~~~

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Y

SUB

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ION

OF

TH

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N

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LIT

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SPH

ER

E

010

2030

4050

Km

II

,.

..

APP

RO

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AT

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OR

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NT

AL

SCA

LE

FIG

UR

E19

-Sch

emat

icPa

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aphi

cal

Inte

rpre

tatio

nof

the

Cile

tuh

Are

aD

urin

gE

ocen

eT

imes

..

~

Qt

F

A

Qm

Fp

c

Criteria used for provenance ternary plots

Q : monocrystalliDe aDd polycrystalline quartz grams.including cbcn (Q - Qm + Qp);monocryscalline quartz;polycrystalline quartz. including chert;mooocrystalline feldspar (F = P + K);plagiociascK-feldsparunstable polycrystal1inc lithic fragments (L -Lv + Ls);volemic aDd mctavolemic fragmentS;cMi;", rory aDd UI~\uN\;memary fragments;L + Qp

Qm:Qp:F :P .:K :L :Lv:Ls:Lt:

173

.&

Quartzose Suite (n ; 17)

Volcanic Suite (n: 7 )

am

L

Lt

B

F

ap

Lvm

Fk

s~uc"on:mp,o

Arc Orogen

FIGURE 20 - Sandstone Provenance Ternary Diagrams (ProvenanceFields After Dickinson and Suczek, 1979)

174

..

~l~

8~M[AN INTERPRETE.

PAL EOC URRENT(NORTH AREA)

N

Ao'

W3~OO

2700 --~~: 90°. , ,

180.

,NORTH

SOUTH

EXPLANATION

~~APA LEOCURRENT

)'

(SOUTH AREA)

c:==f~?:J

UJUNG BATUNUNGGAL

12

10

NUMBER OFOBSERVATIONS

5

TOTAL NUMBEROF MEASI1REMENTS

2 KmI

FIGURE 21 - Summary of Paleocurrent Measurements, Quartzose Facies(Based on Resedlmented Conglomerate Clast Orientation,Unless Otherwise Noted)

175

FIGURE 22 - Diagenetic and Porosity Evolution History of the CiletuhFormation Quartzose Sandstones

DIAGENETIC NORMAL BUR IAL TECTONIC OUTCROP

PROCESS DIAGENESIS COMPACTION WEATHERING

Pyrite ..a)

II

- a:allZed)

fFe-CalciteI jJissolution

(Minar)

Quartz ' --', --------- I-- -Overgrowths

/ I,

KaoliniteI

---- I(Cement+replacement) I

I

Chlorite -------- II,

Overburden un -. ICompaction

.-+- II

.Tectonic 0 0"-. I

"'- 6 0 6>--,?Compaction \/

Secondary-@-?

I 0 0 Q 0 0 0

Porosity I0 0 0 0 0 0

IGrain

-@-?I

DissolutionDissolution I

I

IFe-Oxide II I I II I I

I

35-SST BEDS WITH

Porosity MAJOR Fe-CALCITE%>-a:: '':'" ,'," " , " .'

UJO 0 .z"" TIME -+og?....

i:SST BEDSWITHNOz- 3«C/)

C/)g F,-CALCITE0 Porositya..

' """':"-"-"-"-':

%

0

TIME --

r r r rTIME MAX SUBDUCTION UPLIFT

C/)BURIAL RELATtD AND.... OFzDEPTH COMPACTION EXPOSUREUJ DEPOSITION> (1,5-1.7 KM) (MID-LATE (PLIOCENE-UJ

MIOCENE) PLEISTOCENE?)

-..I

0\

Non

-C

ompr

Elts

sion

alT

ecto

nic

Set

ting

-~A~

Hea

vyC

ompa

ctio

nF

rom

Tec

toni

cC

ompr

essi

on

SIGNIFICANT

PRESERVED

PO

RO

SIT

Y(:

::::::

14%

)

-~- 0

FA

NS

AN

D.S

TO

NE

HIG

HP

RIM

AR

YP

OR

OS

ITY

(~35

%)

PA

RT

IAL

PO

RO

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ES

TR

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N

NE

AR

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LET

EP

OR

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ITY

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ION

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NT

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ITY

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e-

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ithM

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ater

Influ

x

WS

UR

FA

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a

~~

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ent

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rain

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utio

n

Dec

arbo

xyla

tion

inA

ssoc

iate

dSou

rce

Roc

ks

Cem

entI

iG

rain

Sol

utio

n

B~

~~

-~

ctzJ

--

c

FIG

UR

E23

-Sce

nari

osFo

rPo

ssib

leD

evel

opm

ent

ofC

iletu

hFo

rmat

ion

-L

ike

Res

ervo

ir

.

PL

AT

E1-

Thi

nSe

ctio

nP

hoto

mic

rogr

aphs

-~

c#i

'.-.

~ I.

:J I JA

Poor

lyso

rted

quar

tzos

esa

ndst

one

litho

faci

es,

show

ing

com

plet

ede

stru

ctio

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poro

sity

byco

mpa

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ote

tight

pack

ing

and

abun

danc

eof

conc

ave-

conv

exgr

ain

cont

acts

.M

ost

brow

nar

eas

repr

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tsq

uash

edlit

hics

.Sc

ale:

1cm

=10

0ur

n.

.RQ

uart

zose

litho

faci

es,

show

ing

heav

yde

form

atio

nof

am

echa

nica

llyun

stab

lelit

hic

rock

frag

men

t(L

)du

eto

heav

yco

mpa

ctio

n.N

ote

how

grai

nha

sbe

ensq

ueez

edin

to

adja

cent

pore

s.Sc

ale:

1cm

=40

urn

C.

Qua

rtzo

selit

hofa

cies

sand

ston

ehe

avily

cem

ente

dby

ferr

oan

calc

ite.

Not

eth

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loto

pic"

cem

ent

and

abun

danc

eof

floa

ting

topo

int

grai

nco

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ts.

Thi

sfa

bric

indi

cate

sea

rly

calc

itece

men

tatio

npr

ior

tom

ajor

com

pact

ion.

-Sc

ale

1:1

cm=

100

urn.

D.

Vol

cani

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hofa

cies

,sh

owin

ga

volc

anic

last

icsa

ndst

one

com

pose

dof

mos

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em

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l/vitr

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ffgr

ains

.Not

ew

hite

zeol

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men

t(Z

).Sc

ale

1:1c

m=

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rn- -.

)-.

)

PL

AT

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-Out

crop

Pho

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aphs

-.j

00

."

.,A

.Se

quen

ceof

thin

lybe

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Faci

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sand

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eov

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inby

amal

gam

ated

,th

ickl

ybe

dded

Faci

esB

sand

ston

es.

Not

eth

e(a

ult

atce

nter

(arr

ow)

and

pauc

ityof

scou

ring

.C

iletu

hH

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and,

Sect

ion

4.

B.

Org

anis

edpe

bble

/cob

ble

cong

lom

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acie

sA

)st

ratif

ied

with

plan

er-b

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dco

arse

grai

ned

sand

ston

e(F

acie

sB

).N

ote

the

freq

uent

scou

ring

ofco

nglo

mer

ate

into

sand

ston

e(s

eear

row

).C

iletu

hH

eadl

and,

Sect

ion

6.

C.

Mul

tiple

thin

ly-b

edde

dfi

ning

-upw

ard

sand

ston

es(F

acie

sC

,E

and

poss

ible

B)

inte

rpre

ted

aspo

ssib

lele

vee

depo

sits

.C

iletu

hH

eadl

and,

Sect

ion

5.D

.T

hinl

ybe

dded

,m

ud-r

ich

Faci

esE

and

Dsa

ndst

ones

with

less

freq

uent

thic

ker

inte

rbed

sof

Faci

esC

sand

ston

es.

Poss

ible

inte

rcha

nnel

/lobe

area

,Uju

ngB

atun

ungg

al.

PL

AT

E3-O

utcr

opP

hoto

grap

hs

A.

Poly

mic

tpe

bble

cong

lom

erat

e(F

acie

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)w

ithim

bric

ate

fabr

icof

elon

gate

clas

ts.C

urre

ntfl

owfr

omri

ghtt

ole

ft(c

last

sdi

pup

-cur

rent

).N

ote

grey

volc

anic

san

dor

ange

colo

red

oxid

ized

side

ritic

mud

ston

e.C

iletu

hH

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and,

Sect

ion

3.

C.

Flui

dize

dsl

ump

depo

sit

(Fac

ies

F)in

volv

ing

coar

segr

aine

dFa

cies

B.

No,

teco

nvol

ute

bedd

ing.

CH

etub

Hea

dlan

d,Se

ctio

n4.

B.

Len

ticul

arto

wav

ybe

dded

,co

arse

sand

ston

ese

tin

dark

-col

ored

silty

mud

ston

e(F

acie

sE

).C

Het

ubH

eadl

and,

Sect

ion

S.

D.

Ove

rtur

ned

slum

pfo

ld(F

acie

sF)

invo

lvin

g.Fa

cies

C/D

inco

rpor

ated

into

Faci

esB

sedi

men

tfl

ow.

Inje

ctio

nfe

atur

ede

note

dby

arro

w.

Cile

tub

Hea

dlan

d,Se

ctio

nS.

o...J

It:)

PL

AT

E4-O

utcr

opP

hoto

grap

hs...

...00 0

A.

Arg

illac

eous

very

fine

sand

ston

een

rich

edw

ithbl

ack

coal

ifie

dpl

ant

frag

men

tsan

dro

unde

dre

depo

site

dco

alcl

asts

(den

oted

byar

row

).N

ote

over

lyin

ggr

avel

lysa

ndst

one

with

scou

rco

ntac

t.C

iletu

hH

eadl

and,

Sect

ion

5.

B.

Mou

ldof

plan

tfr

agm

ent

with

digi

tate

seed

pods

,vi

sibl

eon

erod

edbe

ddin

gsu

rfac

e.C

iletu

hH

eadl

and,

Sect

ion

5.

C.

Bed

ding

surf

ace

ofgr

avel

lysa

ndst

one

(Fac

ies

B)

cont

aini

ngnu

mer

ous

circ

ular

-

shap

ed,

redd

ish-

stai

ned,

num

mul

itic

fora

ms

(den

oted

byar

row

s)an

dan

oxid

ized

carb

onat

em

ud-c

last

(M).

D.

Faci

esA

cobb

leco

nglo

mer

ate

scou

ring

into

unde

rlyi

ng,

undu

latin

gpa

ralle

l-be

dded

Faci

esB

sand

ston

e(s

cour

sde

note

dby

arro

ws)

.C

iletu

hH

eadl

and,

Sect

ion

6.

PL

AT

E5-O

utcr

opP

hoto

grap

hs

A.

Vol

cani

clas

tictu

rbid

itefa

cies

com

pose

dof

mos

tlyth

ick

bedd

edFa

cies

B(B

)an

d

less

erth

inly

bedd

edFa

cies

Dw

ithtu

ffac

eous

shal

e(D

).Pu

lau

Dah

eu.

B.

Vol

cani

clas

tictu

rbid

ite,

show

ing

thin

lypl

anar

lam

inat

edFa

cies

Bsa

ndst

one

over

lain

byFa

cies

Ape

bble

-gra

velc

ongl

omer

ate:

Onl

ym

inim

alsc

ouri

ngis

evid

ent

(den

oted

byar

row

).Pu

lau

Dah

eu.

C.

Prob

lem

atic

poly

mic

tvo

lcan

icbr

ecci

ade

bris

flow

/slu

mp?

(B)

surr

ound

edby

circ

ular

defo

rmed

Faci

esD

mud

ston

ean

dsa

ndst

one

(def

orm

atio

nde

note

dby

arro

ws)

.K

aran

gH

adji,

Cile

tuh

Bea

ch.

D.

Poly

mic

tbr

ecci

a(E

)co

mfo

rmab

ly?

over

lain

bylig

ht-c

olor

ed,

mon

omic

tbr

ecci

ated

ande

site

(V).

Pula

uK

unti.

00