calcareous nannofossil and dinoflagellate stratigraphy across the cretaceous/tertiary boundary at...

MarineMicropaleontology, 18 (1992) 199-228 199 Elsevier Science Publishers B.V., Amsterdam

Calcareous nannofossil and dinoflagellate stratigraphy across the Cretaceous/Tertiary boundary at Hor Hahar, Israel

Y. Eshet a, S. M o s h k o v i t z a, D. H a b i b b, C. B e n j a m i n i c and M. Magar i t z d aGeological Survey of lsrael, 30 Malkhei Israel St., Jerusalem, 95501, Israel

bDepartment of Geology, Queens College, Flushing, NY 11367, USA CDepartment of Geology and Mineralogy, Ben Gurion University, P.O. Box 653, Be'er Sheva, 84105, Israel

dlsotope Department, Weizmann Institute of Science, Rehovot, 76100, Israel

(Received April 9, 1991; revision August 21, 1991 and accepted September 3, 1991 )

ABSTRACT

Eshet, Y., Moshkovitz, S., Habib, D., Benjamini, C. and Magaritz, M., 1992. Calcareous nannofossil and dinoflagellate stratigraphy across the Cretaceous/Tertiary boundary at Hor Hahar, Israel. Mar. MicropaleontoL, 18:199-228.

In Israel, the Cretaceous/Tertiary (K/T) boundary at Hor Hahar occurs within the interval from the top of the Ghareb Formation (Maastrichtian) to just below the horizon of dark marl and clay within the overlying Taqiye Formation (Pa- leocene). The studied interval contains all the calcareous nannofossil zones: Micula prinsii (latest Maastrichtian), Mar- kalius inversus - - NP1 (earliest Paleocene), and Cruciplacolithus tenuis - - NP2 (Early Paleocene). They correlate in sequence with the Abathomphalus mayaroensis, P0 Pla, Plb, and Plc planktic foraminiferal zones.

The palynological assemblages consist mainly of dinocysts with only few pollen grains and spores. These assemblages are used to interpret five stratigraphic phases of environmental change across the K/T boundary in the Hor Hahar section. In the latest Maastrichtian, there is an overwhelming dominance of the nannofossil Micula decussata, which probably reflects environmental stress preceding the terminal Cretaceous mass extinction. A nearshore marine environment at the boundary is suggested by the increase in number of specimens of the dinocyst Cyclonephelium, and by the predominance of terrigenous organic matter sediment. There followed two episodes of transgression and regression. The calcareous cyst- producing dinoflagellate Thoracosphaera (Futterer, 1976) becomes dominant in two episodes at the boundary and ap- proximately one meter above it. It alternates in abundance with the organic-walled dinoflagellates, which suggests that different environmental parameters were operating for each group. Maastrichtian dinocysts decline in abundance toward the K/T boundary. They reach greatest abundance and species diversity at the same strata Where foraminiferids recover after their mass extinction at the boundary. Calcareous nannofossils recover only later in the early Paleocene.

Changes in 8t3C and total organic carbon, as as well as dinocyst and nannofossil composition indicate an episode of strong ecological stress about one meter above the boundary.

Introduction

T h e d r a m a t i c e x t i n c t i o n o f v a r i o u s g r o u p s o f o r g a n i s m s in t he i n t e r v a l a c r o s s t he K / T

b o u n d a r y has long b e e n a sub jec t o f i n t e n s i v e s t udy , a n d v a r i o u s m o d e l s f o r t he e x t i n c t i o n s

h a v e b e e n p r o p o s e d . A l v a r e z et al. ( 1 9 8 0 ) re- p o r t e d a p o s i t i v e w o r l d w i d e I r i d i u m ( I r )

Correspondence to: Y. Eshet, Geological Survey of Israel, 30 Malkhei Israel Street, Jerusalem 95501, Israel.

a n o m a l y at t he K / T b o u n d a r y . T h e y in ter -

p r e t e d th i s t o be deb r i s f r o m an ex t r a t e r r e s t r i a l

i m p a c t w h i c h was a l so a d i r ec t c ause fo r t he ex t i nc t i ons . M a n y o t h e r e x p l a n a t i o n s w e r e p r o p o s e d , s u c h as fo r e x a m p l e , w i d e s p r e a d

m a r i n e r eg re s s ion a n d w o r l d w i d e n u t r i e n t in-

s u f f i c i e n c y at t he e n d o f t he C r e t a c e o u s ( B r a m l e t t e , 1965; Z a c h o s a n d A r t h u r , 1986;

B r i n k h u i s a n d Z a c h a r i a s s e , 1 9 8 8 ) , ca t a - s t r o p h i c w o r l d w i d e v o l c a n i c e r u p t i o n s ( M c -

L e a n , 1980, 1982; Zo l l e r et al., 1 9 8 3 ) a n d

0377-8398/92/$05.00 © 1992 Elsevier Science Publishers B.V. All rights reserved.

2 0 0 Y. ESHET ET AL.

strong greenhouse warming (Emiliani et al., 1981 ).

Modern studies of the K / T boundary section in Israel began at Hor Hahar some ten years ago. Magaritz et al., (1983, 1985) presented the first reports on the biostratigraphy, magnetostratigraphy, and isotopic changes at the boundary. In these studies, the location of the K / T boundary was defined on the basis of the first occurrence (FO) of the calcareous nannofossil Biantholithus sparsus and the sharpest decrease in the ~3C values. Since the foraminiferal assemblages, including Parvula- rugoglobigerina eugubina, were found in layers below the FO of B. sparsus, their occurrence was regarded by Magaritz et al. ( 1983; 1985 ) as of latest Maastrichtian age. Later studies in various K / T boundary sections in the world, and especially that of E1 Kef, Tunisia (Perch- Nielsen, 1981b; Smit, 1982; Keller, 1988) established the currently used biozonation, based on foraminiferids and calcareous nannofossils. The present paper utilizes the new biostratigraphic scheme for the definition of the K / T boundary, which is based mainly on the FO of small eoglobigerinids such as Eoglobigerina fringa, E. edita, etc. (P0 Zone) and P. eugubina (P 1 a Zone ).

Subsequent studies correlated K / T boundary sections in southern Israel (Keller et al., in press ), and integrated phytoplanktonic groups ( nannofossils and dinoflagellates) into a study of the paleoenvironments that prevailed at the transition from the Cretaceous to the Tertiary (Moshkovitz and Eshet, 1989 ).

The purpose of this paper is to present additional information on the distribution of phytoplanktonic groups - - calcareous nannoplankton and organic-walled dinoflagellates - - two important segments in the marine food chain, and to use their occurrence for a recon- struction of the events at the the K / T boundary.

Geologic setting

The Hor Hahar section - - the former and

popular name for Har Zin - - (Israel grid E. 1556/N.0268) is located in the center of the Zin syncline, near the base of the Har Zin table mountain. This syncline is bounded in the north and in the south by the NNE-SSW trending Hazera and Mahmal anticlines, re- spectively (Fig. 1). The Hor Hahar section contains one of the best-studied K / T boundary intervals of the Negev and in the eastern Tethyan province (Romein, 1979a; Smit et al., 1988).

The base of the outcrop is composed of tan, indurated chalk with marl of the Upper Maas- trichtian Ghareb Formation. The layers pass gradually upwards into dark, grey-green clayey marl of the Danian Taqiye Formation. Gyp- sum veins and pyrite concretions are common and the rock unit is several tens of meters thick (Figs. 2-6 ). In the studied section, no iridium anomaly was detected at the K / T boundary. This is in contrast to many western Tethyan localities in Europe and North Africa, and in the North Atlantic.

Materials and methods

The Hor Hahar section was sampled in a 6.6 m interval (Figs. 2-6) . Eighty-four samples, collected at closely-spaced ( 10 cm or less) intervals, were examined for calcareous nannofossils. Sixty-one samples were studied for palynomorphs.

Samples for light microscope study of nannofossils were prepared following the usual suspension method (separation of the heavy fraction after one minute and concentration of the suspended material after 15 minutes of set- tling in distilled water). The technique described by Moshkovitz (1974) was used to study the same specimen in both light and scanning electron microscopy.

Samples for palynological study were digested in concentrated hydrochloric and hy- drofluoric acids. Slides for light microscope

STRATIGRAPHY ACROSS THE K/T BOUNDARY AT HOR HAHAR, ISRAEL 201

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study were prepared after sieving the organic residue through a 15 #m sieve (Doher, 1980).

Abundances of calcareous nannofossils and palynomorphs were determined by counting of at least 300 specimen per slide in light microscope, following the technique described by Moshkovitz and Erlich (1976) and Jiang and Gartner (1986). This count includes most of the common forms. A further search, for rare forms, was later conducted, and was included in the relative abundance charts. The quanti- tative classification of palynomorphs and calcareous nannofossils is presented in Figs. 2 and 4.

Selected samples of special interest were studied for stable carbon isotopes.

All samples and slides are stored at the Geo- logical Survey of Israel (at Jerusalem ).

Calcareous nannofossils-biostratigraphy

The general distribution pattern of stratigraphically important forms across the K / T boundary is shown in Figs. 2 and 3. The stratigraphic position of the boundary is determined by the first occurrence (FO) of the small Danian planktonic foraminifera Eoglobiger- ina fringa, E. edita and Guembeli tria in the lowest part of the Markal ius inversus (NP1) Zone. Three biostratigraphical nanno-zones ( Micula prinsii, Markal ius inversus- - NP 1 and Cruciplacolithus tenuis - - NP2) were distinguished and correlated with the foraminiferal planktic zonation of Smit ( 1982 ) as modified by Keller ( 1988 ). The most important calcareous nannofossils in these zones are presented in Plate I.

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1. Micula prinsii Zone

Definition: I n t e r v a l f r o m the F O o f M. prinsii

to the first c o m m o n occurrence o f Braarudos- phaera bigelowi a n d / o r Thoracosphaera operculata and Thoracosphaera spp. This z o n e was

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proposed by Perch-Nielsen ( 198 la,b) to cover the uppermost part of the Maastrichtian. Some authors (Thierstein, 1981; Jiang and Gartner, 1986 ) include it within the Micula mura Zone. In Israel, the FO of M. prinsii is always above the FO of M. mura, and very close to the K / T boundary (Moshkovitz, 1984).

Age: latest Maastrichtian. Distribution: The M. prinsii Zone occurs at the base of the section, along an interval of 240 cm (Fig. 2 ). The light to dark tan calcareous marl is composed mainly of nanno-ooze. The assemblages contains Maastrichtian forms including Micula decussata, M. prinsii (Plate I, 6, 7 ), Thoracosphaera operculata (Plate I, 22), Thoracosphaera spp., Lithraphidites quadra- tus, Arkhangelskiella cymbiformis (Plate I, 16), Prediscosphaera cretacea (Plate I, 19 ) Cribros- phaerella ehrenbergi (Plate I, 17 ), and Ahmu- erella regularis (Plate I, 11 ). The lower 150 cm of the unit are composed of dark and light marls, is mainly Micula decussata ooze (Plate I, 21 ). The number of thoracosphaerids, in re-

lation to other species, increases towards the top. Preservation of the nannofossils is moderate or good, but most of the thoracosphaerids are broken.

The latest Maastrichtian age of this interval is supported by the presence of the planktic foraminiferal forms Abathomphalus mayaroensis and Plumerita hantkeninoides, indicating the Upper Maastrichtian A. mayaroensis Zone.

2. Markalius inversus (NP-1) Zone

Definition: The interval from the first common occurrence of Braarudosphaera bigelowi and/or Thoracosphaera operculata and Thor- acosphaera spp. to the FO of Cruciplacolithus tenuis. This zone was proposed by Mohler and Hay in Hay and Mohler (1967) and was emended by Martini ( 1971 ). Age: earliest Paleocene. Based on the FO of small eoglobigerinids ( E. fringa, E. edita ), the K / T boundary is drawn just below the dark

PLATEI

1. Biantholithus sparsus Bramlette and Martini, 1964, cross-polarized light, 3750 X, sample 42. 2. Cruciplacolithusprimus Perch-Nielsen, 1977, Nomarski phase contrast, 3750×, sample 24. 3. Cruciplacolithus tenuis (Stradner, 1961 ) Hay and Mohler in Hay et al., 1967, cross-polarized light, 3750 X, sample

11. 4. Erisconia cava (Hay and Mohler, 1967) Perch-Nielsen, 1969, cross-polarized light, 3750X, sample 9. 5. Biscutum ?romeinii Perch-Nielsen, 1981a, cross-polarized light, 3750X, sample 55. 6-7. Micula prinsiii Perch-Nielsen, 1979:

6. SEM, distal side, sample 47; 7. SEM, proximal side, sample 47.

8. Micula mura (Martini, 1971 ) Bukry, 1973, cross-polarized light, 3750X, sample 81. 9. Neocrepidolithus ?bukryi Perch-Nielsen, 1981a, cross-polarized light, 3750×, sample 27.

10. Biscutum ?parvulum Romein, 1979, SEM, distal side, sample 55. 11. Ahrnuerella regularis (Goarka, 1957) Verbeek, 1977, cross-polarized light, 3750×, sample 63. 12. Nephrolithusfrequens Gorka, 1957, cross-polarized light, 3750 ×, sample 43. 13. Markalius inversus (Deflandre in Deflandre and Fert, 1954) Bramlette and Martini, 1964, cross-polarized light,

3750X, sample 49. 14. Cyclagelosphaerareinhardtii (Perch-Nielsen, 1968) Romein, 1977, cross-polarized light, 3750X, sample 19. 15. Prediscosphaera quadripunctata (Gorka, 1957) VErbeek, 1977, cross-polarized light, 3750×, sample 47. 16. Arkhangelskiella cyrnbiformis Vekshina, 1959, SEM, distal side, sample 82. 17. Cribrosphaerella ehrenbergi (Arkhangelsky, 1912 ) Deflandre, 1952, SEM, distal side, sample 82. 18. Prediscosphaera spinosa (Bramlette and Martini, 1964) Gartner, 1968, SEM, distal side, sample 80. 19. Prediscosphaera cretacea (Arkhangelsky, 1912) Gartner, 1968, SEM, distal side, sample 81. 20. Chiastozygus plicatus Gartner, 1968, SEM, distal side, sample 81. 21. Nanno-ooze composed mostly ofMicula decussata Vekshina, 1959, SEM, sample 80. 22. Thoracosphaera operculata Bramlette and Martini, 1964, SEM, sample 41.

2 0 6 Y. ESHET ET AL.

basal layers of the Taqiye Formation. Distribution: The lower boundary of the zone is located a few cm below the base of the dark clayey marls of the Taqiye Formation, where poorly-preserved foraminifera probably indicate the earliest Tertiary P0 foraminiferal zone. In most other Negev sections (e.g. Ben Gurion section in southern Israel), the top of the Ghareb Formation was also found to contain small number of early Danian forms such as E. fringa Guembelitria and Eoglobigerina spp., within an overwhelming population of reworked Maastrichtian forms (Keller et al., in press). Thus the precise K / T boundary horizon in the Hot Hahar section is not clearly defined, due to poor preservation of foraminifera and extensive reworking. The lower part of the Taqiye Formation contains poorly-preserved foraminifera of "Danian aspect", including P. eugubina (FO at a height of 243 cm from the base of the studied section), indica- tive of zone P0 or P 1 a. As in other Negev sections, the FO ofP. eugubina is accompanied by rapid fall-off of Maastrichtian reworked foraminiferal species, and represents the first rich Danian foraminiferal fauna and its first Ter- tiary evolutionary radiation.

Nannofossils are common to abundant, con- sisting mostly of Late Maastrichtian species, possibly redeposited. The number ofthoracosphaerids is relatively high throughout the lowest 50 cm (up to sample 60). Here we note the FO of rare and badly preserved occurrence of specimens of Biscutum ?parvulum and B. ?romeini (Plate I, 5, 10 ). Both forms continue upward together and therefore a subzonation of the M. inversus zone using the separate ranges of these nannofossils (cf. Perch-Niel- sen, 1981a,b; Jiang and Gartner, 1986) is not possible. Preservation of the nannofossils ap- pears fairly good under the light microscope, but SEM examination reveals that most are covered with a thin clayey layer and are partly etched. The overlying dark marly clays still contain common to abundant nannofossils of Maastrichtian aspect, but in smaller numbers.

Thoracosphaerids decrease, whereas the number of Tertiary nannofossils increases slightly with the appearance of rare Neocrepidolithus fussus and N. crassus.

At about 100 cm above the K / T boundary, there is a strong increase of thoracosphaerids, dominated by T. operculata (Plate I, 22) and in places forming a "Thoracosphaera ooze". This Thoracosphaera ooze is located at the FO ofBiantholithus sparsus (Plate I, 1 ), where the K / T boundary was previously positioned by Magaritz et al. (1983, 1985). The overall number of nannofossils, mostly of Maastrich- tian aspect, increases in this part of the section, as also do the coccoliths of Tertiary origin. Preservation remains poor.

The FO of Biantholithus sparsus is marked by the extinction of P. eugubina and related species, indicating the base of zone P 1 b.

Some 15-20 cm above the FO of Biantholi- thus sparsus and the extinction of Parvularu- goglobigerina eugubina is the FO of Subbotina, the key form marking the P lb foraminiferal zone. As in other localities, the FO of this species tends to be somewhat diachronous (MacLeod and Keller, 1991 ). Zone P lb represents a t ime of faunal turnover among the planktic foraminiferida. At about 400 cm height (sample 34 ) the FO of Cruciplacolithus primus (Plate I, 2) is recorded. Other coccoliths, mainly of Maastrichtian aspect are still present, as are the thoracosphaerids, but their number decreases steadily.

3. Cruciplacolithus tenuis (NP-2) Zone

Definition: The interval from the FO of Cruci- placolithus tenuis to the FO of Chiasmolithus danicus. The zone was proposed by Hay and Mohler (1967) and was emended by Martini (1970). Age: Early Paleocene. Distribution: The base of this zone is located in the yellowish clayey marl, at a hight of about 5 m above the base of the studied section (sample 21 ). It includes the top of planktic forami-


niferal zone P lb and goes into zone Plc. The FO of large forms of C. tenuis (Plate I, 3) is accompanied by C. primus, Erisconia cava (Plate I, 4), E. eopelagica, Toweius spp., Mar- kalius inversus (Plate I, 13) and small Biscu- turn spp. The coccolith assemblage from below continues, including mostly Maastrichtian forms. SEM examinations reveal that the preservation of the nannofossils in the section is poor. Only the lower part of NP2 zone was studied.

A darkish horizon in the variegated interval is recognized throughout the Negev, with the presence of biserial planktic foraminifera and G. daubjergensis peaking along with a significant increase in the amount of benthic foraminifera. This interval is located near the top of foraminiferal subzone Plb. Some 50 cm above the variegated interval is the FO of Sub- botina inconstans, marking the base of planktic foraminiferal subzone P lc. Guembelitria and biserial forms decline, replaced by subbo- tinids, e.g. abundant Subbotina pseudobulloides. This represents the second evolutionary radiation of Tertiary planktic foraminifera following the K / T extinction.

Magnetostratigraphy

The magnetostratigraphic reversal from C29R to C29N occurs in the lower part of zone P lb, beneath the C. tenuis NP2 datum and just above the FO of S. pseudobulloides (Magaritz et al., 1985, fig. 2 ). Although there is an uncer- tainty of some 10 cm regarding the exact position of the FO of P. eugubina, this datum and the magnetostratigraphic results can be broadly used to derive rate of sedimentation in this interval. Thus, the duration from the FO of P. eugubina (66.35 Ma) to the top of anomaly C29R (66.17 Ma, Berggren et al., 1985) includes some 180 cm of the section, avaraging about 1 cm per 1000 yrs. For comparison, sedimentation rates in the lowest Paleocene in the E1 Kef section (Tunisia), avarage between 1.04-1.40 cm/1000yrs (Keller, 1988).

Paleoecology of calcareous nannofossil assemblages

Due to their planktic mode of life and rapid distribution across wide areas, calcareous nannofossils are used mainly in stratigraphy as time, rather than paleoenvironmental indicators. However, there are some cases where composition of the assemblages may reflect ex- treme marine conditions. In these cases the normally broad species spectrum is replaced by monospecific or monogeneric forms. Blooms of Thoracosphaera (calcareous-walled dinoflagellate, Futterer, 1976), Braarudosphaera, Micrantholithus and Micula, though infre- quent, are known to occur in the stratigraphic record. These assemblages reflect restricted or unstable environments due to insufficient nutrients, low or high salinity of the water, or temperature variability (Bukry, 1974, 1981; Jafar, 1979 after Gaarder and Hasle, 1971). Several such intervals dominated by Micula and Thoracosphaera occur at Hor Hahar (see Fig. 3 ). Four major "nanno-events" are identified in the studied section, and represent the changes that occured across the K / T boundary. These events are, from the oldest to the youngest: (A) Micula decussata bloom; ( B ) First Thoracosphaera bloom; (C) Second Thoracosphaera bloom; (D) Reestablishment of marine conditions for the recovery of calcareous nannoplankton.

A. Micula decussata bloom (latest Maastrichtian)

Blooms of Micula decussata dominate the basal part of the studied section (Fig. 2), forming in some instances a monospecific M. decussata ooze (Plate I, 21 ). According to Thierstein (1980), this species is considered most resistant to dissolution. However, since most other forms in this interval are well preserved, its presence here is not attributed to selective preservation or differential dissolution. The enormous blooms of monospecific assem-

208 V. ESHET ET AL.

blages in the water body that might have had important biological influence on the associated marine biota, are an indication of unusual marine conditions prior to the K / T extinction. Similar blooms of M. decussata have been found in Late Maastrichtian layers assigned to the Micula taurus nannofossil Zone in some other well known outcrops, e.g. Braggs section, Alabama (Worsley, 1974); Brazos River, Texas; Littig Quarry, Texas (Jiang and Gart- ner, 1986); San Tolmo section, Spain (Perci- val and Fischer, 1977 ).

B. First Thoracosphaera bloom (K/T boundary interval)

An interval of about 40 cm thick (samples 65-60) is characterized by a sudden marked increase in Thoracosphaera operculata. This interval straddles the K / T boundary which is located just below the base of the dark marly clays of the Taqiye Formation.

Nearly all the K / T boundary intervals cited in the literature are characterized by a mass appearance ofthoracosphaerids (cf. Bramlette and Martini, 1964; Christensen and Birke- lund, 1979; Romein, 1979b; Perch-Nielsen et al., 1982). These forms are regarded as "opportunistic" and indicate unusual marine conditions that prevailed during the K / T extinction. Even though the present day marine biogeographical distribution of Thoracos- phaera has not yet been studied in detail, there are indications that these forms may with- stand severe ecological conditions. Investiga- tions in the Gulf of Mexico show that they are commonly found only in surface samples of high salinity values (cf. Jafar, 1979 after Gaar- der and Hasle, 1971 ).

Together with the Thoracosphaera peak in this interval, there is an increase in the overall abundance of nannofossils with Maastrichtian aspect. If these nannofossils are redeposited, then such a supply can be attributed to increased current action during a regressive phase

with increased erosion of previously deposited sediment.

Other K / T sections in the western Tethyan province, e.g. Spain, France, Tunisia and Texas contain mass occurrences of the "opportunistic" (hypohaline) forms, the braarudosphaer- ids (Perch-Nielsen, 1985) in the earliest and Early Paleocene subzones, including the C. tenuis Zone (Percival and Fischer, 1977; Perch- Nielsen, 1979; Romein, 1979b; Jiang and Gartner, 1986). These genera are absent in all K / T intervals in Israel (Moshkovitz and Ehr- lich, 1982; Magaritz et al., 1985 ), thus indicating that different paleoenvironmental marine conditions probably existed in the eastern and western Tethys.

C. Second Thoracosphaera bloom (Early Paleo- cene Pla/b Zone)

Higher up in the section, at the P l a / P l b planktic foraminifera zonal boundary, about 1 m above the K / T boundary, a 50 cm interval (between samples 44-37 ) is distinguished, in which Thoracosphaera operculata is again dominat, and forms in some levels a Thoracos- phaera ooze. This bloom is also accompanied by an increase in nannofossils of a Late Maas- trichtian aspect. It is assumed that the presence of both elements ( Thora¢osphaera bloom and redeposited material) indicates a second regressional marine phase in the Early Paleocene.

D. Reestablishment of marine conditions for the recovery of calcareous nannoplankton (Base of NP-2 and Plc Zone)

There is a moderate but steady increase in relative abundance and species diversity of Early Tertiary nannofossils upwards. How- ever, their numbers remain rather low (only ten species at the top of the section). At about 3 m above the K /T boundary, in the lower part of the Cruciplacolithus tenuis (NP2) Zone (base of planktic foraminifera P lc Zone),


there is a sudden increase in Tertiary forms (sample 14). This level represents the first reestablishment of marine conditions for the development of calcareous nannoplankton, even though the optimum has not yet been reached. The general paleoenvironmental trend indicates a moderate but steady deepening at this time. This reestablishment occurs also in the planktic foraminiferida with Subbotina pseudobulloides and its offshoots (e.g.S. inconstans) becoming dominant.

Palynomorphs

Organic particles preserved in marine rocks can be classified into groups which reflect depositional facies. At Hor Hahar, the first are the autochthonous marine particles that include organic-walled planktonic fossils (dinocysts, acritarchs, other algae) and fecal amorphous debris which is the end product of phytoplankton digested by zooplankton (Por- ter and Robbins, 1981; Habib, 1982 ). The second kind of organic particles found in marine sediments is terrigenous land plant detritus. This kind includes pollen grains, conductive tissue and cellular cuticle, tracheids and inertinite.

Analysis of the different organic facies types is useful in characterizing the depositional environment. Habib (1982) interpreted sea-level changes in the Mesozoic Northwest Atlantic from the relationships among organic facies types and between autochthonous and allo- chthonous palynomorphs. For example, the tracheal facies is dominated by woody particles and numerous well-preserved fern spores, which suggests rapid terrigenous sedimentation of organic matter during sea-level fall. The amorphous debris facies consists of abundant well-preserved fecal amorphous debris (Honjo, 1980) and numerous dinoflagellate species. It was deposited during sea-level rise, when the continental margins were covered by shallow seas. It contains very little plant detritus, ex- cept for ubiquitous inertinite. The amorphous

debris facies is especially well-established in the Cenomanian-Turonian boundary event (CTBE) in the North Atlantic basin (Habib and Drugg, 1987). This approach was supported by Eshet et al., ( 1988 ) who showed that fluctuations in the amount of terrigenous organic particles in the marine Permo-Triassic of Israel match the sea level curve of Druckman (1974). Brinkhuis and Zachariasse (1988) grouped the palynomorphs in the E1 Kef section, Tunisia, using them to infer sea-level and environmental changes across the K/T boundary, based on generalized analogies to dinoflagellate populations in Recent and sub- Recent environments.

Dinoflagellate cysts comprise the majority of palynomorphs in the Hor Hahar section (Fig. 4 ). Due to the absence of palynological mark- ers for the K/T boundary in this section, ranges and palynologic assemblage composition do not enable subdivision into chronostratigraphically-significant palynozones. The distribution of the taxa, however, does contain important information on ecological changes in the marine environment.

The FO of Danea californica (Drugg) is usually accepted as a well-established datum for the base of the Tertiary (Drugg, 1967; Han- sen, 1977; Damassa, 1979; Brinkhuis and Leereveld, 1988; Brinkhuis and Zachariasse, 1988). Unfortunately, this taxon is not found at the K/T boundary in Hor Hahar and cannot be used as a biostratigraphic marker.

At Hor Hahar, the palynomorphs form five significant, environmentally-controlled assemblages that provide clues on the development of the marine paleoenvironments. These assemblages represent palynologic phases (Fig. 4), following Schuurman ( 1977 ) who was the first to use this concept in palynostratigraphy, and Van der Zwan (1980), who defined a phase as "any recognizable step in the (local, regional (or inter-regional) gradual composi- tional development of stratigraphically succes- sive (palynological) assemblages". Phases were later utilized to describe palynological devel-

210 Y. ESHET ET AL

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opments by various authors, e.g. Visscher and Krystyn, 1978; Brugman, 1986). The differential characters of the five palynological phases in Hor Hahar are primarily based on the presence of selected (marine) dinocysts and, to a lesser extent, (land-derived) pollen and spores. This paper presents the first palynological results from a K / T section in Israel, and therefore, the use of phases is preferred for biostratigraphical subdivision. Additional palynological studies may provide a basis for a regional scheme of chronostratigraphically- significant zones. The most important palynomorphs in each of the phases is presented in Plates II-VI.

PHASE I (Fig. 4) This phase ranges from the latest Maastrich-

tian M. prinsii nannofossil Zone, to just above the K / T boundary, in the planktic foraminifera P0 Zone at the top of the Ghareb Forma- tion. The lower part of this phase contains abundant fragments of extensively degraded dinocysts. In the upper part, dinocysts are better preserved but their number and species diversity decrease. Terrestrial particles (pollen grains, spores, and woody tissues) become more common toward the top of the phase and reach a maximum at the K / T boundary (Fig. 5).

The interval between samples 83-79 contains rare to common Palaeocystodinium sp. A as the only identifiable dinocyst (Plate IV, 4). Palaeocystodinium sp. A is described here for the first time. It is characterized by solid horns, a bifurcation at one horn (Plate V, 5, 8) and by faint striations, running along the central, ellipsoidal body. The environmental or strati- graphical significance of this taxon is yet not well understood.

Towards the K / T boundary, at the top of the phases, dinocysts assignable to Cyclonephel- ium and Glaphyrocysta become gradually more common, although dinocyst number and species diversity remain rather low.

PHASE H (Fig. 4) This phase occurs in the lowest part of the

Paleocene, in the dark marly clay of the Taqiye Formation (Fig. 4). It lies within the Markal- ius inversus (NP1) nannofossil Zone which ranges from planktic foraminifera zone P0 to the top of zone P l a (samples 61-43). Com- pared with their scarcity in Phase I, dinocyst number and species diversity in Phase II become very high. This phase represents the establishment of the first diverse Tertiary dinoflagellate population. It coincides with the first evolutionary expansion of planktic foraminifera P. eugubina and E. edita. Calcareous nannoplankton are not yet reestablished.

The phase is characterized by an upward increase in abundance and diversity of organic- walled dinocysts. Spiniferites is the dominant taxon (Fig. 4). Maximum species abundance and diversity is reached at the top of the phase (Fig. 5 ). Chorate dinocysts are dominant m including Spiniferites ramosus, S. mirabilis, Exochosphaeridium bifidum, Hystrichokol- poma granulatum, Hystrichosphaeridium tubiferum and Tanyosphaeridium magdalium. Peridinioid dinocysts are less frequent, the most common of which is Manurniella druggi. Other peridinioids are Cerodinium speciosum, C. striatum, Phelodinium magnificum, Lejeu- necysta comrnunis, L. hyalina, Senegalinium bicavatum, Andalusiella polymorpha, A. dubia and Palaeocystodinium australinum. Other important taxa in Phase II are Glaphyrocysta perforata, Cyclonephelium castelcasiense and Cyclapophysis monmouthensis.

The base of Phase II is characterized by taxa which are common in the Maastrichtian, whereas toward the top of the zone more typical Tertiary taxa become dominant. This is well illustrated by the distribution of Phelodinium magnificum and Lejeunecysta communis (Fig. 4).

Several trends are notable in Phase II: ( 1 ) As shown in Fig. 5, dinocyst abundance

increases drastically from the top of Phase I

212

PLATE II

Y. ESHET ET AL


(sample 62) to the base of Phase II (sample 61).

(2) Maximum species abundance and diversity is reached at the top of the phase.

(3) Percentage and species diversity of peridinioid dinocysts, especially Senegalinium spp. andA. dubia, increase gradually toward the top of the phase (Fig. 4).

(4) Amount of terrestrial particles gradually decreases upward to a minimum at sample 43, at the top of the phase (Fig. 5 ).

PHASE III This phase ranges from sample 42 to sample

31, in the lower part of planktic foraminifera zone P 1 b, and within the calcareous nannofossil zone NP 1 (Figs. 4 and 5 ). Its base is characterized by a crisis, marked by large drops in the total organic carbon (TOC) and the stable C 13 isotope (c~3C). A drop in these parameters is usually regarded as a result of a drop in productivity. The assemblages in this phase are dominated by a high abundance of Thoracos- phaera. Recent studies of foraminiferids, indicate the presence of a hiatus between zones P 1 a and P 1 b, at the base of Phase III. Phase III is characterized by a notable decrease in the abundance and species diversity of dinocysts, and an increase in terrestrial particles (Fig. 5 ). Manumiella spp., common in the underlying Phase II, become rare, whereas another peridinioid, Isabelidinium pellucidum becomes prominent (Fig. 4) and continues to the top of the studied section. Most taxa are chorate cysts. Oligosphaeridium becomes more frequent, while Spiniferites decreases slightly. Other taxa in Phase III are: Exochosphaeridium bifidum,

Palaeocystodinium australinum, Cyclonephel- ium castelcasiense, Cyclapophysis monmouthensis, Oligosphaeridium spp., Cordosphaeri- dium inodes, Florentinia mantelii, Kenleyia nuda, and Tanyosphaeridium magdalium (Fig. 4).

PHASE IV This phase ranges from sample 30 to sample

13, in the variegated clay interval. The stratigraphic position is from within the planktic foraminifera zone P 1 b to the base of zone P 1 c, crossing the boundary between the NP 1 and NP2 nannofossil zones. (Fig. 5 ). Planktic foraminifera show crisis at this horizon, with abundance of opportunistic species. This phase is characterized by a dominance of amorphous debris, including faecal pellets and abundant unidentifiable remains of dinocysts, which indicate intensive degradation. Terrestrial particles are very rare.

PHASE V This phase ranges from sample 13 to the top

of the studied section, 6.61 cm above the base, in dark grey marly clay. It is in the P 1 c planktic foraminifera zone and the NP2 nannofossil zone. This horizon marks the second evolutionary expansion of planktic foraminifera, the decline of opportunistic foraminiferal taxa, and the start of the establishment of marine conditions suitable for the development of calcareous nannoplankton.

The phase is characterized by high abundance and diversity of dinocysts. Among the chorate cysts, Oligosphaeridium spp., Cor- dosphaeridium fibrospinosum, C. inodes, Flo-

PLATE II

1, 5. Lejeunecysta communis Biffi and Grignani, 1983: 1. 400 ×, sample 44; 5.800 X, sample 13. 2. Palaeocystodinium australinum (Cookson, 1965) Lentin and Williams, 1976, 500X, sample 57. 3. Phelodininium magnificum (Stanley, 1965) Stover and Evitt, 1978, 1000X, sample 61. 4. Manumiella sp. 500 X, sample 47. 6. Andalusiellapolymorpha (Malloy, 1972) Lentin and Williams, 1977, 800×, sample 43. 7. Paleoperidiniumpyrophorum (Ehrenberg, 1838) Sarjeant, 1967, 800×,sample 61. 8. Phelodinium magnificurn (Stanley, 1965) Stover and Evitt, 1978, 600X, sample 57.

2 1 4 Y. ESHET ET AL

P L A T E II l

6

v


rentinia mantelii, Hysterichokolpoma granulatum, Impletosphaeridium severinii, Pervosphaeridium truncigerum, Hystricho- sphaeridium tubiferum and Spiniferites spp. are the most important forms. Among the peridinioid forms, Senegalinium bicavatum, Anda- lusiella polymorpha, A. dubia and Isabelidi- nium pellucidum are the prominent taxa.

A notable palynological trend in this phase is the upward increase in Senegalinium spp. and A. dubia. Terrestrial particle are rare and the overall dinocyst abundance and diversity is high.

Most of the samples in the studied section are dominated by amorphous organic debris, with minor amounts of terrestrial detrital particles. Despite their low numbers, changes in the amount of terrestrial organic particles was found to be a useful tool in determining sea- level and environmental changes in this study (Fig. 5 ).

In order to analyze paleoenvironmental changes along the studied section, the palynomorphs were classified into environmentally- significant palynologic groups (Fig. 5). Each group is defined based on the predominant palynomorphs in it. Three of these groups have a similar composition to the environmentally- significant groups of Brinkhuis and Zachar- iasse ( 1988 ) in El Kef, Tunisia.

The following groups are utilized in this study (Fig. 5 ):

1. Organic-walled phytoplankton group This includes all dinocysts and acritarchs.

They form the autochthonous palynologic ele-

ments and their abundance is used to characterize changes in the marine environment. As shown by Habib and Miller (1989), during transgression, dinocyst species diversity increases, reaching a peak just after the time of maximum flooding. This approach is used here in some intervals to detect possible sea-level changes. This group is especially dominant in Phases II and V.

2. Terrestrial particles group This group includes pollen, spores, cuticles,

tracheids and all other remains of land plants. Following Habib (1982), Brinkhuis and Za- chariasse (1988) and Stanley (1965, 1966), high quantities of terrestrial particles may indicate low sea levels. Terrestrial particles are generally scarce in the studied section, but their abundance increases at the K / T boundary and at the top of Phase II.

3. Cyclonephelium group (Brinkhuis and Za- chariasse, 1988)

This group comprises Cyclonephelium castelcasiense, Cyclonephelium spp., Glaphyro- cysta perforata, and Glaphyrocysta spp.

Cyclonephelium is regarded by Marshall and Batten (1988) as an indicator of environments of nearshore anoxic stress, where the low oxygen zone extends tiigh in the water-column. Brinkhuis and Zachariasse (1988) considered Cyclonephelium and other members of the Cy- clonephelium group to be possible indicators of a warm shallow inner neritic setting. Liengjar- ern et al. (1980) found Glaphyrocysta, an important member of the Cyclonephelium group,

PLATE III

1, 4. DinogTmnium acuminatum Evitt et al., 1967, 500X, sample 61. 2. Isabelidiniumpellucidurn (Deflandre and Cookson, 1955) Lentin and Williams, 1977), 800X, sample 13. 3. Manumiella druggii (Stover, 1974) Bujak and Davies, 1983, 1000×, sample 44. 5. Phelodinium magnificum (Stanley, 1965) Stover and Evitt, 1978. 400 X, sample 59. 6, 8. Senegalinium bicavatum, Jain and Millepied, 1973, 500×, sample 6. 7. Andalusiella dubia, Jain and Millepied, 1973, 400 ×, sample 44. 9. Cerodinium striatum (Drugg, 1967) Lentin and Williams, 1977), 800×, sample 44.

10. Palaeoperidiniumpyrophorum (Ehrenberg, 1838). 500×, sample 50.

216

PLATE IV

Y. ESHET ET AL

3


in Oligocene-Eocene estuarine sediments in the Isle of Wight.

4. Spiniferites group (Brinkhuis and Zachar- iasse, 1988)

This group comprises species of Spiniferites and Achomosphaera. Recent species of Spini- ferites live in shallow oxygenated marine environments of the shelf, e.g. the Persian Gulf (Bradford and Wall, 1984). Marshall and Bat- ten (1988 ) consider Spiniferites an indicator of open, oxygenated marine environments in Cenomanian-Turonian black shales in North- ern Europe. Wall et al. (1977) and Bradford and Wall (1984) report a decrease in its abundance and diversity toward the offshore. Schrank (1984) considers Spiniferites an indicator of open shallow marine environments. Offshore of West Africa, it is found in deeper marine sediments, but there it is considered to be transported from the shelf by turbidity cur- rents (Zonneveld, 1989, written commun.) . Following Brinkhuis and Zachariasse ( 1988 ), and the above authors, the Spiniferites group is regarded here as an indicator of open marine shelf environments.

5. Senegalinium group (Brinkhuis and Za- chariasse, 1988)

This group includes Senegalinium spp., An- dalusiella dubia, Phelodinium magnificum, Lejeunecysta communis, L. hyalina and other peridinioid dinocysts. Brinkhuis and Zachar- iasse ( 1988 ), regarded the Senegalinium group to be representative of heterotrophic dinoflag-

ellates. Their distribution may, hence, be di- rectly or indirectly, related to productivity and nutrients in the water-body. In this study, the group is usually associated with low amounts of terrestrial particles, and relatively high dinocyst species diversity, all of which suggest a possible transgression.

Palynological synthesis (Fig. 5)

It is possible to infer paleoenvironmental changes across the K / T boundary from the stratigraphic distribution and relative abundances of the major palynological groups as plotted in Fig. 5.

Due to the scarcity of dinocysts, it is hard to infer paleoenvironmental changes in the lower part of Phase I. In the upper part of this phase, the increase in species diversity in the Cyclo- nephelium group and terrestrial particles towards the K / T boundary, as well as the low species diversity, point to a strong terrestrial influence and a regressive episode leading up to the boundary.

Oxygen isotope studies of the K / T boundary section on the Sinai border, Israel, reveal evidence of several horizons of fresh-water cal- cite growth, mainly on planktonic foraminifera, associated with hiatuses in the faunal record. This suggests lo~v salinity water influx at the K / T boundary. Planktic foraminifera population studies at the boundary (Keller et al., in press) suggest an erosional hiatus at the base of P0 and the extensive reworking of both planktic foraminifera and calcareous nanno-

PLATE IV

1. Apteodinium australiense (Deflandre and Cookson, 1955 ) Williams, 1978, 400 ×, sample 60. 2. Kenleyia cf. K. nuda De Coninck, 1969, 1200x, sample 47. 3. Kenleyia leptocerata, Cookson and Eisenack, 1965, 800 ×, sample 61. 4. Tanyosphaeridium magdalium (Drugg, 1967) Heisecke, 1970, 500×, sample 50. 5. Glaphyrocysta perforata Hultberg and Malmgren in Hultberg, 1985, 800 X, sample 65. 6. Cyclapophysis monmouthensis, Benson, 1976, 500×, sample 50. 7. Spiniferites ramosus (Ehrenberg, 1838 ) Loeblich and Loeblich, 1966, 500 X, sample 49. 8. Cyclonephelium castelcasiense Corradini, 1973, 500 ×, sample 49. 9. Exochosphaeridium bifidum (Clarke and Verdier, 1967) Clarke et al., 1968, 800X, sample 45.

218

PLATE V

Y. ESHET ET AL

~ , ~!i ̧ ~

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fossils, in concert with the raised amounts of terrestrial organic particles. These support the indication of low sea level and erosion at the boundary.

Phase II, mostly in planktic foraminifera zone P 1 a, contains a gradual upward increase in dinocyst abundance and diversity. Together with the decrease in terrestrial particles, it points to a smaller terrestrial influence and, probably, a transgressional trend in this phase. The dominance of Spiniferites indicates shelf environments. Increase in productivity toward the top of Phase II might be indicated by the gradual increase in the Senegalinium group and other peridinioid dinocysts. It is reflected by the gradual increase in Total Organic Car- bon (TOC - - see Fig. 6). Phase II is concurrent with the evolutionary expansion of the foraminifer Parvularugoglobigerina eugubina.

Phase III, the lower part of zone Plb, is characterized by a notable decrease in dinocyst abundance and variety, in concert with increase in terrestrial particles. This led us to suggest the beginning of a regressive episode at the end of this phase, about 1 m above the KIT boundary. The transition from Phase II to Phase III is marked by a notable increase of Thoracosphaera specimens and a drop in Car- bon isotopes. These indications suggest a great ecological stress at this horizon. Similar conclusions were reached by Brinkhuis and Za- chariasse (1988) in the K / T boundary of E1 Kef.

Planktic foraminifera studies (Keller et al., 1990) show another hiatus, at the P l a / P l b boundary, where opportunistic species (e.g. Guembelitria) are common.

Phases IV and V represent a transgressive episode which is marked by a gradual upward

increase in dinocysts (although in Phase IV, most of them cannot be identified properly to a species or genus level due to degradation), associated with a decrease in terrestrial particles. Possible higher productivity in the marine environment in Phase V (planktic foraminifera zone P lc and lower part of NP2 nannofossil Zone) is suggested by the notable increase in specimen number and species diversity of the Senegalinium group, and the equivalent decrease in the Spiniferites group. The high productivity is also suggested by the predominance of amorphous organic debris in phases IV and V. These phases mark the second reestablishment step of marine conditions suitable for the development of planktic foraminifers and dinocysts, and the first one for the calcareous nannoplankton after the K / T boundary.

Figure 3 presents a tentative paleoenvironmental interpretation as reflected by the composition of organic matter and calcareous nannofossils in the Hor Hahar section. It suggests a significant lowering of sea level at the K / T boundary, associated with increase in terrestrial influence and the occurrence of dinocysts such as Cyclonephelium, and other members of the Cyclonephelium group, that characterize stressed nearshore shallow environments. The same palynologic phenomenon was reported from the K / T boundary in E1 Kef, where Brinkhuis and Zachariasse (1988) suggested that this sea-level fall led to a great decrease in productivity due to changes in marine circula- tion, ultimately causing collapse of the marine ecosystem.

Above the K / T boundary, dinocysts assemblages, and the decrease in terrestrial particles, point to a transgressive-regressive cycle (pa-

PLATE V

1. Cordosphaeridium sp., 800 X, sample 47. 2, 5, 7, 8. Palaeocystodinium sp. A., sample 83: 2. 800X; 5.500×; 7. 800X, 8. 1000×. 3. Pervosphaeridium truncigerum (Deflandre, 1937)Yun, 1981, 800X, sample 61. 4. Palaeocystodinium sp. A complex, 250 ×, sample 82. 6. Palaeocystodinium australinum (Cookson, 1965 ) Lentin and Williams, 1976, 800 X, sample 50.

220

PLATE VI

Y. ESHET ET AL


lynologic Phases II and III) and the beginning of another cycle (Phases IV and V). Similar cycles were also found in the E1 Kef section (Brinkhuis and Zachariasse, 1988 ).

Total organic carbon and carbon isotopes

The Hor Hahar section was studied for its calcium carbonate and total organic carbon (TOC) content, and for stable carbon isotopes values. Results are plotted in Fig. 6. The following trends can be observed in this figure:

(1) Carbon isotopes from the Hor Hahar section show a gradual depletion in 813C across the K /T boundary interval, from 1.0 to 0.4%o vr. PDB. There is no significant change at the boundary itself, since most of the material present just above the boundary is reworked from the Maastrichtian. The steepest portion of the gradual depletion curve is about 1 m above the K / T boundary, at the P I a /P 1 b sub- zonal boundary, and the first occurrence of Biantholithus sparsus, where ~13C values drop from 0.4 to -0.3%0 (top of palynologic phase II ). The gradual depletion in 813C is unique to Hor Hahar. In other sections in Israel, e.g. Ein Mor, elsewhere in the Zin valley (Magaritz et al., 1985 ) the decrease is much steeper across the boundary itself. In this respect the Hor Ha- har section represents more continuous depo- sition across the boundary, despite hiatuses and reworking common in the Negev (Keller et al., in press).

Low TOC values are found about 1 m above the boundary, pointing to low productivity.

This horizon coincides with the greatest decrease in dinocyst abundance and variety, and a thoracosphaerid acme, all typical of harsh ecological conditions (Figs. 3 and 5). These data suggest that the greatest ecological crisis occurred, not at the K / T boundary (as desig- nated by the foraminiferids), but about 1 m above it.

(2) The lowest values of ~I3C occur near the top of the section (6.0 m), close to the base of P 1 c Zone. They can be correlated with the c$13C minima at the Sinai border section. These minima which occur several hundred thou- sand years after the K / T bioevent, reflect the conditions at which the marine environments responded to a change in the carbon cycle be- fore the faunal recovery.

(3) The calcium carbonate curve (Fig. 6) expresses the lithological changes in the section, from light marls, poor in organic matter, in the Ghareb Formation to black marly clays, richer in organic matter, in the Taqiye Forma- tion. There is a correlation between CaCO3 and c~ 13C, showing that CaCO3 is also productivity- related.

Inter-relationships between phytoplanktonic groups

Calcareous nannofossils and dinocysts are the major phytoplankton groups preserved in the studied section. We here compare these two groups, dwelling in the same parts of the marine ecosystem, with respect to their responses

PLATE VI

1. Spiniferites complex, 380×, sample 44. 2. Typical palynofacies for the latest Maastrichtian, close to the K/T boundary; Note tracheid and abundant Cyclone-

phelium spp., 250x, sample 65. 3. Terresytrial plant-cuticles, 380 X, sample 40. 4. ? fungal cell, 500X, sample 62. 5. Oxidized organic matter, 250X, sample 83. 6. Lejeuncysta sp., 800×, sample 47. 7. Woody tracheid, 400 X, sample 62. 8. Terrestril vascular tissue, 600X, sample 62.

2 2 2 v. ESHET ET AL.

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Fig. 6. TOC, stable carbon isotopes, a n d CaCO3 content in the Hor Hahar section. Note low TOC and ~ 3 C values about 1 m above the K / T boundary (top of Phase II) . The dashed line represents results obtained from a nearby section, several meters from the present one.

to ecological changes, as well as their mutual relationships (Fig. 3 ).

The latest Maastrichtian is characterized by a Micula decussata ooze. This interval contains only one common dinocysts species, the Palaeocystodinium sp. A. The monospecific

phenomena in both phytoplankton groups suggest stressed environments at the end of the Maastrichtian, prior to the extinction at the K / T boundary. Further study of"Micula ooze" intervals is needed to better understand the stressed environments apparently common at

224 Y. ESHET ET AL.

the end of the Maastrichtian. Of special interest is the occurrence of the

calcareous-walled dinoflagellate Thoracos- phaera. The stratigraphic distribution of Thor- acosphaera in the section shows two peaks: the lower one occurs at the K / T boundary at the base of NP1 zone (planktic foraminifera zone P0). It coincides with the top of palynologic Phase I, where proximity to land is suggested by the palynomorph and foraminifer assemblages. Another prominent peak is recorded immediately above sample 43 (base of palynologic Phase III, P I a /P l b boundary and FO of B. sparsus), where dinocysts decline rapidly and a second regressive phase after the K /T boundary is noted, supported by a notable drop in ~ 13 C values.

Comparison of the calcareous and the organic-walled dinoflagellates shows that in the Hor Hahar section, the two groups are inversely related, i.e. that when one group flourishes, the other becomes scarce. Thoracos- phaera seems to be more tolerant to harsh ecological conditions in the studied section than the organic-walled dinoflagellates; in Hor Hahar, it flourishes in environments lacking organic-walled dinoflagellates and other phytoplanktonic groups.

In a preliminary study (Moshkovitz and Eshet, 1989), it was found that at the Hor Ha- har section, dinocysts become gradually more scarce toward the K /T boundary. They become abundant in all samples some 15 cm above the K / T boundary. The rate of restored conditions for the planktic foraminiferids after the K / T crisis in various places (e.g. DSDP holes 356, 384, 577A, Zumaya, Caravaca and El Kef ) is reported to be quicker than that for the calcareous nannoplankton (Smit and Romein, 1985). This is also found in the Hor Hahar section (Fig. 3 ).

Conclusions

( I ) The K/T boundary in the Hor Hahar section is located a few cm below the first dark

marly clays of the Taqiye Formation, in layers that carry poorly preserved small foraminifers probably related to the P0 Zone. Higher, the presence of foraminiferids, including P. eugubina (FO at level 2.43 cm height) and calcareous nannofossils allow recognition of the P 1 a, P lb, and P lc planktic foraminifera Zones, and the correlatable NPI and NP2 nannofossil Zones.

(2) The classification of palynomorphs into five environmentally-significant groups en- ables the recognition of five palynological phases that represent the environmental devel- opments from the latest Maastrichtian to the Early Paleocene.

( 3 ) The latest Maastrichian is characterized by an abundance ("ooze') of the nannofossil Micula decussata and the occurrence of the organic-walled dinocyst Palaeocysodinium sp. A. These monospecific phenomena reflect the harsh conditions that existed at the end of the Cretaceous. A shallowing trend towards the K /T boundary is indicated by the increasing number of specimens of the Cyclonephelium group.

(4) A peak of a regressional episode at the K /T boundary is indicated by the increase in reworked elements (terrestrial organic particles, foraminifers and calcareous nannofossils) and by the decrease in the number of planktic foraminifers. Harsh conditions at the boundary are reflected by an bundance of the calcareous walled dinoflagellate Thoracosphaera.

(5) A transgressional trend in the first meter above the K / T boundary (samples 61-43 ) is indicated by the increase in abundance and species diversity of dinocysts and decrease in terrestrial organic particles. This episode is concurrent with the first evolutionary expansion of the Tertiary planktic foraminifera.

(6) A marked ecological crisis is observed at the end of the transgressional episode, about 1 m above the K / T bounary (above sample 43 ). This is indicated by a strong increase in abundance of Thoracosphaera, and a notable drop


in ~ 3C and TOC values that suggest a decrease in the rate of productivity. Decrease in dinocysts and increase in terrestrial organic particles, and foraminiferal evidence for hiatus, suggest a regressional episode that followed the ecological crisis. The regression begins in sample 42 and continues to a height of about 1.5 m the K / T boundary (until sample 31 ).

(7) Above sample 31, there is evidence for the beginning of a new transgressional episode, characterized by a gradual increase in abundance and species-diversity or organic-walled dinocysts. The gradual increase in the Senegal- inium group suggests high productivity, associated with predominance of amorphous organic debris. This phase marks the first sign of reestablishment of calcareous nannoplankton after the K / T boundary extinction.

(8) The abundances of the calcareous-walled dinoflagellate Thoracosphaera and the organic-walled dinoflagellates, which both uti- lize the upper part of the ocean water-column, are found to be inversely related. In the section where the Thoracosphaera flourishes, the organic-walled dinocysts are scarce.

(9) The long-term gradual depletion of the ~13C values across the K / T boundary interval seems to represent more or less continuous de- position in the Hor Hahar section, despite hiatuses common in the Negev.

(10) Based on magnetostratigraphy, the rate of sedimentation along the section from the FO of P. eugubina to the base of C 29 N is esti- mated to be 1 cm per 1000 years.

Acknowledgements

This report summarizes project No. 22020 of the Ministry of Energy and Infrastructure to S. Moshkovitz and Y. Eshet. Part of it was supported by a grant from the U.S. National Sci- ence Foundation to D. Habib, EAR-8903522.

We are grateful to our collegues at the Geo- logical Survey of Israel: B. Katz and I. Perath for text editing, T. Beer for laboratory assis- tance, Y. Levi for Photography, and A. Pe'er

for graphic work. H. Brinkhuis, W.A. Brug- man (University of Utrecht, The Nether- lands) and G.L. Williams (Atlantic Geosci- ence Centere, Nova Scotia) provided useful comments on the manuscript.

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