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153 MAGNETOSTRATIGRAPHY SUSCEPTIBILITY HIGH-RESOLUTION CORRELATION, U.S. AND SINAI PENINSULA, EGYPT

Magnetic Susceptibility Stratigraphic Methodologies

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B. ELLWOOD, A. KAFAFY, A. KASSAB, A. ABDELDAYEM, N. OBAIDALLA, R.W. HOWE AND P. SIKORA154

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MAGNETOSTRATIGRAPHY SUSCEPTIBILITY USED FOR HIGH-RESOLUTION

CORRELATION AMONG SANTONIAN (UPPER CRETACEOUS) MARINE

SEDIMENTARY SEQUENCES IN THE U.S. WESTERN INTERIOR SEAWAY

AND THE WESTERN SINAI PENINSULA, EGYPT

BROOKS B. ELLWOODDepartment of Geology and Geophysics, Louisiana State University,E235 Howe-Russell-Kniffen Geoscience Complex, Baton Rouge, Louisiana 70803, U.S.A.

e-mail: [email protected] KAFAFY

Geology Department, Faculty of Science, Tanta University, Tanta 31527, EgyptAHMED KASSAB

Geology Department, Faculty of Science, Assiut University, Assiut 71516, EgyptABDELAZIZ ABDELDAYEM

Geology Department, Faculty of Science, Tanta University, Tanta 31527, EgyptNAGEH OBAIDALLA

Geology Department, Faculty of Science, Assiut University, Assiut 71516, EgyptAND

RICHARD W. HOWE AND PAUL SIKORAEnergy & Geoscience Institute, 423 Wakara Way, Suite 300, Salt Lake City, Utah, 84108, U.S.A.

ABSTRACT: Magnetic susceptibility (MS) measurements of marine rocks provide an underutilized but powerful high-resolution tool instratigraphy. In ideal circumstances and when combined with other stratigraphic techniques, the method can yield resolution to 10,000years or less. This paper applies the MS method to solving a Cretaceous global correlation problem. Because of the active global processesthat drove significant evolutionary changes during this time, the Upper Cretaceous is important in Earth history. However, correlationsamong geological sequences are difficult, in part because Earth’s magnetic polarity was essentially non-varying from the Aptian to theSantonian. Here we present high-resolution correlations for Upper Cretaceous marine sedimentary successions spanning all or part of theSantonian Stage from the Western Interior Seaway (U.S.A.) and the Western Sinai Peninsula (Egypt). To do this we have integrated theresults of magnetic susceptibility (MS) measurements of unoriented samples from lithified marine rocks (in outcrop and from core) and

biostratigraphic data sets from these sequences. In this study a MS zonation for the Santonian Stage has been developed and graphiccomparison has been used for correlation. In the main, correlation between the U.S. and Egyptian sequences is excellent. Third order T/R cycles (> 100 kyr) observed in this high-resolution data set for the Santonian Stage indicate significant similarities between the U.S. and

Egyptian sections and allow correlation among sequences. We interpret these correlations to result from cyclicities caused by climate-controlled continental erosion and deposition of detrital components, mainly clay, in the marine realm. Second-order cycles (> 1 Myr) arealso observed in these data sets but show distinctive differences between the U.S. and Egyptian sequences. We interpret these second-orderdifferences to result from local synsedimentary tectonic controls on sediment erosion and deposition. Also observed are two distinct, short-term MS marker events that can be correlated globally.

KEY WORDS: Upper Cretaceous, Santonian, Egypt, Niobrara, global correlation, graphic comparison, magnetic susceptibility

Application of Modern Stratigraphic Techniques: Theory and Case HistoriesSEPM Special Publication No. 94, Copyright © 2010SEPM (Society for Sedimentary Geology), ISBN 978-1-56576-199-5, p. 155–166.

INTRODUCTION

One of the problems facing geologists working on lithifiedmarine rocks is our difficulty to correlate, with high precision,among geological sections. This is especially true when globalcorrelations are desired. Problems faced when using fossils for

high-resolution correlations include facies differences, evolu-tionary rates, and pseudo-extinctions. Isotopic dates are few,and the precision is much too coarse to achieve the high resolu-tion that is often desired. While geochemical or geophysicaltechniques may be useful for correlation, problems exist withthese techniques as well. For example, if the sequence of interestis proximal and there is no carbonate, oxygen isotope data frommarine tests are not feasible. In addition, weathering and low-temperature alteration effects can destroy the primary isotopic

signatures. Finally, many geochemical methods are expensiveand time consuming, negating the large number of data pointsthat are needed to characterize stratigraphic sequences ad-equately.

To deal with some of the problems associated with correla-tions, the geological community has been working to standardize

the geologic time scale (Gradstein et al., 2004). The decision wasmade to formally define stage boundaries as the geologic stan-dard and to do this by establishing a Global Boundary StratotypeSection and Point (GSSP) to define the beginning of each geologi-cal stage for the Phanerozoic (Cowie et al., 1986). The end of eachstage is defined by the beginning point of the stage that follows.Formal rules for the establishment of GSSPs have been adopted(Salvador, 1994). A compilation of the GSSPs established to dateas well as the supporting data can be found in The Geologic Time

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Scale 2004 (Gradstein et al., 2004). The work of the InternationalCommission on Stratigraphy also includes formal usage of mag-netic property measurements in stratigraphy (Salvador, 1994),including formally defining nomenclature for magnetostrati-graphic polarity and susceptibility.

Magnetostratigraphic methods can provide a useful andimportant correlation tool in this correlation and standardiza-tion effort, and magnetostratigraphy polarity, based on theremanent magnetization (RM) of rocks, is being routinely usedfor correlation in Cenozoic and Mesozoic rocks (Gradstein et al.,2004). However, polarity stratigraphy is not well developed forthe Paleozoic, in part because many of these rocks have beenremagnetized. In addition, RM methods are time consuming,expensive, and effectively limited to well consolidated materi-als that can be oriented, thus excluding cuttings and limiting theuse of highly friable sediments. In conjunction with biostratig-raphy, it is possible to get good MS resolution from a wide rangeof materials including cuttings, core, and friable outcrop mate-rials. In addition, remagnetization does not deleteriously affectthe MS resolution. This is because the MS, unlike remanence,does not significantly change even when the rocks are some-what weathered and/or reheated to moderate temperatures (in

some cases to > 350° C). This is illustrated by the reported MScorrelations among heated sections in Morocco (Ellwood et al.,

1999) that show a conodont alteration index (CAI) of > 4.0(Belka, 1991). Finally, the method is inexpensive, is fast, andrequires relatively small samples that are easy to collect, allow-ing large datasets to be gathered effectively.

In this paper we define a Santonian composite section basedon observed MS variations within multiple sections. Our ap-proach is to develop, within a single region, MS data sets todefine the MS characteristics of the Coniacian–Santonian andSantonian–Campanian stage boundaries and then to fill in therest of the Santonian using redundant overlapping sections.Finally, we use the MS composite section thus developed, in thiscase from the Late Cretaceous Western Interior Seaway of theUS, for comparison and correlation to an equivalent Santonian

sequence in the Western Sinai Peninsula region of Egypt. Com-parison of the two regions (Fig. 1) shows that they are located insimilar zones that were tectonically active during the LateCretaceous.

The study sequences cover, or partially cover, the SantonianStage and include the proposed GSSP for the base of the SantonianStage, located along Ten Mile Creek in Lancaster County, Texas,the proposed GSSP for the base of the Campanian Stage, locatedin the Lake Waxahachie Spillway near Waxahachie, Texas (Powell,1970), the USGS#1 Portland Well (Dean and Arthur, 1998), drilledin Portland, Colorado, and several Niobrara chalk sections (Hattin,1982) from Kansas (Fig. 1). All of these sequences have fair to goodlithostratigraphic and biostratigraphic control, and together withthe MS results it is readily demonstrated that correlation amongthese sequences is excellent.

METHODS

Magnetic Susceptibility (MS): General Comments

All mineral grains are “susceptible” to becoming magnetized inthe presence of a magnetic field, and MS is an indicator of thestrength of this transient magnetism within a material sample(Nagata, 1961). MS is very different from remanent magnetism(RM), the intrinsic magnetization that accounts for the magneticpolarity of materials. In marine sediments, MS is generally consid-ered to be an indicator of iron, ferromagnesian, or clay-mineralconcentration (Ellwood et al., 2000; Ellwood et al., this volume) and

can be measured quickly and easily on small samples. In the verylow inducing magnetic fields that are generally applied, MS islargely a function of the concentration and composition of themagnetizable material in a sample. Mathematically, MS is a tensorof the second rank (see Equation 1 and discussion below), andtherefore it has anisotropy (Nye, 1990). This means that the mea-sured MS in a sample will be different in different directions,depending upon the mineral distributions and grain morphology.The anisotropy of magnetic susceptibility (AMS) of most rock types has been well studied (Tarling and Hrouda, 1993). However,it is somewhat time consuming to measure and requires orientedsamples, as do RM studies. Bulk (initial) measurements of MS areoften performed without consideration of the AMS of samples, andfor most samples the MS error due to the anisotropy is small. TheAMS effect is further reduced when samples are crushed before theMS is measured, or where friable samples are broken up duringsampling. MS is much less susceptible to remagnetization than isthe RM in rocks and can be measured on small, irregular lithicfragments and on highly friable material that is difficult to samplefor either AMS or RM measurement.

Magnetizable materials in sediments include not only theferrimagnetic minerals such as the iron oxide minerals (e.g.,

magnetite and maghemite) and iron sulfides and iron sulfates(e.g., pyrrhotite and greigite) that can acquire an RM (required forreversal magnetostratigraphy), but also any other less magnetic,paramagnetic compounds. The important paramagnetic miner-als in marine sediments include the clays, particularly chlorite,smectite, and illite, ferromagnesian silicates such as biotite, tour-maline, pyroxene, and amphiboles, iron sulfides including pyriteand marcasite, iron carbonates such as siderite and ankerite, andother iron- and magnesium-bearing minerals (Ellwood et al.,1989; Ellwood et al., 2000).

In addition to the ferrimagnetic and paramagnetic grains inmarine sediments, calcite, quartz, and organic compounds can beabundant. These materials typically acquire a very weak negativeMS when placed in inducing magnetic fields; that is, their ac-quired MS is opposed to the low magnetic field that is applied.

The presence of these diamagnetic minerals reduces the MS in asample. Therefore factors such as changes in biological produc-tivity or organic-carbon accumulation rates may cause somevariability in MS values.

Low-field MS, as used in most reported studies (Nagata,1961), is defined as the ratio of the induced moment (Mi

or Ji

) tothe strength of an applied, very low-intensity magnetic field (H j),where:

Ji = χ ijH j (mass-specific) (1)

or

Mi = kijH j (volume-specific) (2)

In these expressions, MS in SI units is parameterized as k ,indicating that the measurement is relative to a one-cubic-metervolume (m3) and therefore is dimensionless; MS parameterized as χ indicates measurement relative to a mass of one kilogram, and isgiven in units of m3/kg. Both k and χ have anisotropy. Here, wereport MS without consideration of the AMS, and use MS tocharacterize this bulk (initial) low-field magnetic susceptibility.

Presentation of MS Data

For presentation purposes and inter-data-set comparisons, the bar-log format, similar to that previously established for presenta-tions of magnetic-polarity data, is used. These bar logs are accom-

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panied by both raw and smoothed MS data sets. Here, raw MS data,depicted by the dashed line in Figure 2, are smoothed using splines,the resultant curve being displayed as a solid curve in Figure 2.

Splines are used for smoothing to hold each data point at its properstratigraphic height. The following bar-log plotting convention isthen used; if the MS smoothed cyclic trends increase or decrease bya factor of two or more, and if the change is represented by two ormore data points, this change is assumed to be significant and thehighs and lows associated with these cycles are differentiated byfilled (high MS values) or open (low MS values) bar logs (shown atthe right in figures; e.g., Fig. 2). This method is best employed whenhigh-resolution data sets are being analyzed (large numbers of closely spaced samples) and helps negate variations associatedwith anomalous samples. Such anomalous variations may be dueto weathering effects, secondary alteration and metamorphism,longer-term trends due to factors such as eustasy (as opposed toshorter-term climate cycles), or event sequences such as impacts(Ellwood et al., 2003). In addition, variations in detrital input

between localities, or a change in detrital sediment source, isresolved by developing and comparing bar logs between differentlocalities. It is also recommended that MS data be represented inlog plots due to the range of MS values often encountered. How-ever, MS data variations in log plots for some ranges (for example,1–3 x 10-x versus 4–9 x 10-x) may appear to exhibit large variationsthat are just artifacts of the presentation style. Therefore, bar logshelp to reduce these ambiguities.

MS Measurements

All measurements reported herein were performed using thesusceptibility bridge at LSU. This bridge was built by Marshall

Williams and is a one-of-a-kind instrument. It is calibrated usingstandard salts for which values are reported in the Handbook of Physics and Chemistry and by Swartzendruber (1992). The LSU

bridge is our standard instrument because it is very sensitive, iseasy and fast to use, and the measurement coil is optimized forsmall samples. We report MS in terms of sample mass because itis much easier and faster to measure with high precision than isvolume (Ellwood et al., 1988b). Each sample is measured threetimes and the mean and standard deviation of these measure-ments is calculated. The mean of these measurements is reportedhere. We also performed a number of thermomagnetic suscepti-

bility measurements on selected samples using an AGICO KLY-3S instrument.

PREVIOUS WORK

Applications and Interpretations of Bulk (Initial) Low-Field Magnetic Susceptibility

MS variability from sample to sample results primarily fromchanges in the amount of iron, clay, and ferromagnesian constitu-ents. This variability in marine sedimentary sequences is bothprimary (produced during deposition) and secondary (resultingfrom alteration of the deposited sequence). The primary factorsresulting in variation are weathering, erosion, sediment accumu-lation rates, and biological productivity. These factors are tied toclimate, tectonic and volcanic processes, availability of nutrients,and local (relative) or regional (global) sea-level changes. Second-ary processes include pedogenesis, diagenesis, and within-sedi-ment redox effects driven by bacterial organisms (Ellwood et al.,1988a).

FIG. 1.—Middle Santonian Stage (Upper Cretaceous) continental reconstruction map showing locations of sample site from theWestern Interior Seaway, U.S. and Western Sinai, Egypt; C, Portland Core, Colorado; K, Niobrara Chalk localities, Kansas; Texasproposed GSSP; E, Western Sinai, Egypt. Map modified from Scotese (1998).

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Studies of Marine Sedimentary Sequences

Marine sediments are composed of terrigenous, detrital, andeolian components, and a biogenic component composed of thecarbonate and/or siliceous tests of marine organisms (Balsamand Beeson, 2003). There is also a component of sediment derivedfrom marine weathering processes, but this is generally minor.The MS signature of a marine sediment mainly represents contri-

butions from the terrigenous and biogenic components, and, because the biogenic component is only weakly diamagnetic, ingeneral the terrigenous component dominates the MS. Therefore,processes controlling the influx of terrigenous components intothe marine environment usually account for the MS variationsobserved in a sample. Thus, climate cycles that cause erosion andtransport of terrigenous material result in a cyclic signal in the MSrecorded in the deposited sediments. There are many factors thatcan modify this signature, but while the expected variations may

be reduced in magnitude, usually the character of the cyclesremains and can be extracted. Superimposed on these cyclicvariations are contributions from unique events, such as volcanic

eruptions or meteorite impacts, which may be of local, regional,or global significance.

Previous Results from Lithified Marine Sedimentary Rock Sequences

Following deposition, the ferrimagnetic grains that dominate

the magnetic properties in unlithified marine sediments arerapidly converted to paramagnetic phases, mainly by the actionof bacterial organisms (Karlin and Levi, 1985; Ellwood et al.,1988b). This process generally causes a decrease in magneticproperties in lithified samples. In general, however, this processdoes not remove the iron from the system, so that total ironcontent is conserved. New paramagnetic phases (mainly ironsulfides and carbonates) then contribute, along with the otherparamagnetic detrital components present such as clays and theremaining authigenic ferrimagnetic constituents, to the MS inlithified sediments. MS values for most marine limestone, marl-stone, shale, siltstone, and sandstone samples that we havemeasured range from ~ 1 x 10-9 to ~ 1 x 10-7 m3/kg (Ellwood et al.,2000). Shale and some marlstone have the greatest anisotropy,

but for most of these samples is small. For most limestone,

marlstone, siltstone, and sandstone samples the anisotropy isvery small. Shale and marlstone samples are friable, and mea-surement is generally on small broken fragments, further reduc-ing the anisotropy effect. Therefore, for most samples the errorintroduced by the AMS is minimal (see discussions in Tarling andHrouda, 1993).

Sea-Level and Climate Cycles and Other MS Variations

As described above, MS in lithified marine sedimentarysequences mainly records processes that control the influx of detrital and eolian grains into the marine environment. MSresults for almost all studies of marine sedimentary rocks gen-erally show many levels of cyclicity, with certain cycles inter-preted to result from climatically driven processes (Weedon et

al., 1999; Ellwood et al., 2001). Other cycles are very longer-termand are interpreted as resulting from transgressive–regressive(T/R) trends due to sea-level rise and fall associated witheustasy. As a general rule, especially in distal marine sequences,MS is observed to decrease during transgressive cycles (Ellwoodet al., 2006) due to detrital sediments being trapped in thenearshore during transgressions. However, there are distinctMS peaks that are correlated to maximum flooding surfaces(MFS), as well as to sudden influxes of detrital material intosedimentary basins by turbidity currents or other sediment sus-pensions. During regressions, when base level is lowered due tofalling sea level, erosion flushes detrital sediment into ocean

basins and increases the MS of basinal sediments. Thus T/Rcycles play an important role in creating some cyclic MS varia-tions observed.

The MagnetosusceptibilityEvent and Cyclostratigraphy (MSEC) Method

To describe the methods used and the broad range of physicalprocesses that produce MS trends, the term magnetosusceptibilityevent and cyclostratigraphy (MSEC) was coined by Crick et al.(1997). Results of MSEC work have shown that the MS is mineraldependent but may be independent of the macro-lithology. Re-working of sediments by ocean currents and the variable deposi-tion of clays can result in large MS changes in both limestone andshale, even though the lithology may appear to be relatively non-varying. In addition, while local subsidence may cause a litho-

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Magnetic Susceptibility (m3/kg)

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MS chron

Coniacian

Santonian Sa1

Sa2

Sa3

Sa4

CoZ

CoY

FIG. 2.—MS data from the proposed GSSP located on Ten MileCreek in Lancaster, Texas (T in Figure 1), for the Coniacian–Santonian boundary. Raw MS data are dashed; smootheddata using splines are represented by the solid curve; MSchrons (with labels) are presented as bar, logs and methods

are explained in text, where filled symbols represent higherMS values and open symbols are lower MS values; theConiacian–Santonian boundary location is indicated. MSchrons beginning with Co are Coniacian in age. MS chrons

beginning with Sa are Santonian in age. MS chron labels weredeveloped in conjunction with the data sets from Figures 2 to 5.

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logic change from shale to limestone or vice versa, the MS oftenremains relatively constant.

Our MSEC studies of Phanerozoic marine rock sequenceshave concentrated on GSSPs (as well as other related sections)that are currently being defined by the International Commis-sion on Stratigraphy (ICS). Today, more than half of the ~ 100GSSPs for the Phanerozoic have been formally defined. All of these boundaries are well studied, and much of the biostratig-raphy has been published. Most stage boundaries are defined

based on the first occurrence of a new fossil species, while a fewuse other criteria. For example, the Paleocene–Eocene GSSP inUpper Egypt near Luxor is defined by a negative carbon isotopeshift in the sequence exposed there and in most other Paleocene-Eocene sequences (Dupuis et al., 2003). MSEC results for Pale-ocene–Eocene boundary sections in Egypt (including the GSSP),Spain, and the U.S. are reported elsewhere in this volume(Ellwood et al., this volume).

SAMPLING AND RESULTS

Included here are results for Upper Cretaceous Santoniansamples from two localities in Texas, one locality in Colorado,

four localities in Kansas, and one locality in Egypt. In all sections,the MS data were smoothed using splines and MS chrons weredeveloped using the rules discussed above (in the section titledPresentation of MS Data).

Coniacian–Santonian GSSP Candidateat Ten Mile Creek, Lancaster, Texas

The MS of ~ 6 m of section (127 specimens) along Ten MileCreek in Lancaster, Texas, was measured (Fig. 2), with samples

being collected at 50 mm intervals. The lithologies in the sectionare interbedded limestone (chalk), marlstone, and claystone of the Austin Chalk Formation. The Coniacian–Santonian bound-ary was picked based on foraminifer and nannofossil eventsassociated with this boundary (Burnett, 1998).

Santonian–Campanian GSSP Candidateat Waxahachie Lake Spillway, Texas

Approximately 19 m of section (225 specimens) was sampledat the Waxahachie Lake Spillway and the MS measured (Fig. 3).The interval associated with the Santonian–Campanian bound-ary was sampled at 50 mm intervals , and the rest of the sectionwas sampled at approximately 0.1 m intervals. The lithologiescollected are mainly interbedded chalk and marlstone. The chrono-stratigraphic boundary lies just below the Austin Chalk–TaylorMarl contact , which is unconformable (Powell, 1970; Hancock,and Gale, 1996). The Santonian–Campanian boundary is pickedwithin the Austin Chalk, based upon the recommended bound-ary datum (i.e., the last appearance datum of the benthic crinoid

Marsupites testudinarius), as well as foraminifer and nannofossilevents associated with this boundary (Burnett, 1998; Hancock and Gale, 1996). The Waxahachie section is characterized bycommon to abundant recovery of both planktonic and benthonicforaminifera, and calcareous nannofossils with fair to good pres-ervation. Macrofossil debris, primarily inoceramid prisms andother mollusk shell fragments, is abundant throughout most of the section. Foraminifera generally indicate a warm Tethyanwater mass, with middle-neritic to outer-neritic paleobathym-etry for most of the section. However, an influx of a cool watermass and increase in organic flux with consequent decline in

benthic foraminifer diversity marks the upper part of the section.This paleoecologic change complicates planktonic foraminifer

biostratigraphy in that the stratigraphic range of some Tethyantaxa are truncated; e.g., the last stratigraphic datum (LAD) of Dicarinella asymmetrica occurs relatively low in the section and thefirst occurrence datum (FAD) of the Campanian genusGlobotruncanita is delayed until the base of the Taylor Shale,above a major unconformity marked by a phosphatic lag deposit.

Coniacian to Middle SantonianUSGS#1 Well at Portland, Colorado

Fifty meters of the USGS#1 Portland Core was sampled (N =204) and the MS measured (Fig. 4). Sampling interval was ~ 0.25m. The core covers the interval from the Coniacian–Santonian

boundary to the Middle Santonian (Dean and Arthur, 1998). Theprecise boundary location had some biostratigraphic uncertainty,so we used the MS signature from the Ten Mile Creek proposedGSSP (Fig. 2) to place the boundary in the Portland section.

Coniacian to CampanianComposite Niobrara Sequence from Kansas

MS data are reported (Fig. 5) from a composite of several well-studied localities (Hattin, 1982) of Niobrara Chalk in Kansas (K in

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Campanian

Santonian

Sa7

Sa8

Sa9

Sa10

Sa11

Sa12

Sa13

Sa14

Sa15

Ca1

Ca2

MS chron

Sa10Marker Event

Sa12

marker

FIG. 3.—MS data from the proposed GSSP located at Waxahachie,Texas (T in Figure 1), for the Santonian–Campanian bound-ary. Symbols and notations as in Figure 2. MS chrons begin-

ning with Ca are Campanian in age. There are two distinctmarker events in the data set, Sa 10 and Sa12, which can becorrelated among all overlapping sections.

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Figure 1). Sampling covered the interval from the Coniacian tothe Campanian (N = 494) at a sampling interval of 0.1 m. Sampledsections are from Hattin’s Localities 13, 19, 18, 23, and 20 andcover the entire Santonian Stage. The Coniacian–Santonian andSantonian–Campanian boundaries were picked on the basis of foraminifera and dinoflagellates (McIntire, personal communi-cation) and adjusted by comparison to the MS boundary datafrom the proposed Texas GSSPs (Figs. 2, 3) and with the USGS#1Portland Core (Fig. 4).

Coniacian to Campanian Sequencein the Western Sinai Peninsula, Egypt

MS data from measurements of mainly limestone and shalesamples (N = 279; sampling interval was ~ 0.1 m) from 28 m of section collected in Wadi Sudr, located in the western SinaiPeninsula, Egypt, are reported. The Coniacian and Santoniansequences in the Sinai Peninsula have been well studied andinclude the biostratigraphic record of calcareous nannofossils(Bauer et al., 2001). Integrated micro-biostratigraphy and macro-

biostratigraphy of the Coniacian–Santonian sequence of the south-western Sinai Peninsula, in particular, are from the work of Kassab and Ismael (1996) and Obaidalla and Kassab (2002). Herewe use ammonites and planktonic foraminifera to constrain the

Coniacian–Santonian and Santonian–Campanian boundary lo-cations, with slight adjustments based on the MS data from theU.S. Western Interior Seaway sections.

Thermomagnetic Measurements

Thermomagnetic susceptibility measurements were per-formed on a number of samples from the sampled sequences,including shale and chalk samples. This measurement involvesheating the sample from room temperature to 700° C whilemeasuring the MS as the temperature rises. Paramagnetic miner-als show a parabola-shaped MS decay during this process be-cause the MS in these samples is inversely proportional to tem-perature of measurement (Hrouda, 1994). Based on the standardswe have measured, ferrimagnetic minerals usually show anincrease in MS up to a point where the MS decays toward theCurie temperature of the minerals responsible for the MS. Formagnetite this temperature is ~ 580° C, and for maghemite it is ~610° C for most samples. Above 640° C, maghemite converts tohematite with a Curie point of ~ 680° C. During measurement,

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Sa10 marker event

Santonian

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CoY

CoZ

Sa1

Sa2Sa3

Sa4

Sa7

Sa8

Sa10

Sa11

Sa12

Sa13

Sa14

MS chron

Sa5

Sa6

Sa9

Sa12 marker event

FIG. 4.—MS data from the USGS#1 Portland Core, drilled inPortland, Colorado (C in Figure 1), covering the Coniacianinto the middle Santonian. Symbols and notations as in Figure2. Also given is the lithologic nomenclature for the core;Lower Shale, Middle Chalk, and M. Shale are lower unitswithin the Smokey Hill Chalk of the Niobrara Formation(Dean and Arthur, 1998). Note the Sa 10 and Sa12 marker

events that are also identified in the Niobrara and SinaiPeninsula data sets. Arrows indicate T/R cyclicities (see text).

L o c .

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Ca2

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Sa15

Sa14

Sa13

Sa12

Sa11

Sa10

Sa9Sa8

Sa7

Sa6

Sa5

Sa4

Sa3Sa2

Sa1

Sa12

marker

FIG. 5.—MS data from a composite of several well-studied locali-ties (Hattin, 1982) of Niobrara Chalk from Kansas (K in Figure1). From the Coniacian to the Campanian these sections arefrom Hattin’s Locations 13, 19, 18, 23, and 20, respectively, andcover the entire Santonian Stage. The Coniacian–Santonianand Santonian–Campanian boundaries are represented by

bold dashed lines, and were picked on the basis of foramin-

ifera and dinoflagellate (McIntire, personal communication)data and adjusted by comparison to the MS boundary datafrom the USGS#1 Portland Core (Fig. 4) and to the proposedTexas GSSPs (Figs. 2, 3; see text for a discussion). Symbols andnotations as in Figure 2. Note the Sa 10 and Sa12 markerevents. Arrows indicate T/R cyclicities (see text).

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some iron minerals are unstable at higher temperatures andchange chemically, often producing diagnostic peaks that resultfrom the formation of a ferrimagnetic phase during this change.This is an important result because these minerals usuallydenote a detrital or early diagenetic component (e.g., siderite)that is derived from alteration of ferrimagnetic phases duringdiagenesis.

Results of some of our thermomagnetic work are reported inFigure 6. In samples with the lowest MS values, a weak ferrimag-netic component dominates the MS, although a paramagneticcomponent is also significant. In most of the shale samples theparamagnetic component dominates, indicating a detrital compo-nent. In all of the samples there is a conversion at higher tempera-

tures of iron phases to ferrimagnetic iron phases. At temperatures beginning around 250° C there is a MS thermal conversion that, based on our work with standards, we attribute to the alteration of goethite, produced during weathering, to a more magnetic butunstable ferrimagnetic phase. The most distinctive change is theproduction of magnetite and maghemite from paramagnetic sider-ite, known to occur in the Austin Chalk (Ellwood et al., 1986;Ellwood et al., 1988a) but also seen in the Sinai Peninsula chalk, andfrom paramagnetic clay minerals. Weathered chalk samples usu-ally do not exhibit the distinctive siderite peak (Ellwood et al., 1986;Ellwood et al., 1989), indicating that the siderite has already beenoxidized and the maghemite produced as a result is responsible forthe tan discoloration of these samples.

FIG. 6.—Data on thermomagnetic susceptibility for chalk and shale samples from the Sinai Peninsula, Austin Chalk, Niobrara, andPortland core localities. These data are typical for marine chalk and shale samples and indicate a paramagnetic componentresponsible for the low-field MS reported in the shales, and a slight dominance of a ferrimagnetic component in the chalks. Thechalks are slightly weathered, and the oxidation of paramagnetic constituents like siderite may be responsible for theferrimagnetic dominance in these very low-MS samples. The peaks observed at 300–350° C result from the breakdown of goethitein slightly weathered samples; at higher temperatures > 400° C are mainly due to the breakdown of paramagnetic carbonates andclays to a ferrimagnetic phase (magnetite and maghemite).

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DISCUSSION

In most studies of marine rocks where stratigraphic correla-tion is attempted, there are many uncertainties. The most im-portant data set used is developed from biostratigraphic studiesthat can provide ambiguous results. Problems due to factorssuch as facies-dependent organisms, poor recovery, unrecog-nized unconformities, and Lazarus taxa make it important toemploy independent correlation methods in an effort to resolveuncertainties. MSEC is one such method that provides a robustdata set to evaluate and adjust correlations among geologicalsequences independently. It requires fair to good biostrati-graphic control to initially develop a chronostratigraphic frame-work where distinctive MS zones can be directly correlatedamong sections with high precision, even when biostratigraphicuncertainties or slight unconformities are known to exist withinsections.

An important aspect of the MSEC approach is to define a MScomposite reference section (MS CRS). Specifically, first we col-lect samples and measure the MS, in this case from the proposedGSSPs covering the Coniacian–Santonian boundary (Ten MileCreek section; Fig. 2) and the Santonian–Campanian boundary

(Waxahachie Spillway section; Fig. 3). Results from these AustinChalk sections showed low variability and similar overall MSmagnitudes. However, the smoothed data do show definable MShighs and lows from which we have built an MS chron zonation.From the Ten Mile Creek sequence (Fig. 2), we have identified MSchrons within the latest Coniacian that we have labeled CoX toCoZ. The boundary is placed at the top of CoZ, the last ConiacianMS chron. Within the Santonian we have identified MS chronsSa1 to Sa3, with Sa4 not fully defined.

The GSSP at the Waxahachie Spillway also exhibits distinctiveMS chrons for the Upper Santonian that we have labeled Sa7 toSa15 (Fig. 3). We place the boundary level within an MS chron thatextends into the Campanian, so given that this MS chron is alsothe first chron within the Campanian and defines the base of theCampanian, we have labeled it Ca1. We also see Ca2 in this data

set. The dashed line representing the boundary level indicatesthat there is some biostratigraphic uncertainty, but by compari-son to the Niobrara sequences that we have also sampled (Fig. 5)we believe that placement of the boundary at the level chosen is

justified. Note that there are two distinctive marker events in theWaxahachie sequence that correspond to MS chron Sa10 andSa12. These events are also seen in the Colorado core (Fig. 4), theNiobrara sequence (Fig. 5), and the Sinai Peninsula sequence (Fig.7), indicating that the event is global in character. We believe thatthe two distinctive Upper Santonian marker events result from acombination of synsedimentary tectonism and eustatic effects,and may be associated with the onset of the faunal extinctionsknown to occur in the Late Santonian (Barnes et al., 1996; Silvaand Sliter, 1999).

Following characterization of the bounding GSSPs, we chosethe Niobrara Chalk exposures (Fig. 5) to fill in the rest of theSantonian and to test placement of the boundary levels. MSchrons are consistent among these three sections, as are themarker events. An additional test is provided by the Portland,Colorado, USGS#1 Core data set (Fig. 4). Here, there is a reason-ably well-defined Coniacian–Santonian boundary interval (Burnsand Bralower, 1998) that is based on nannofossil assemblages,and the MS chron zonation is consistent with that observed for theTen Mile Creek GSSP (Fig. 2) and the Niobrara sequence (Fig. 5).The Sa10 and Sa12 marker events are well defined in the PortlandCore.

The last data set we present is that for the Santonian WadiSudr sequence, which we sampled in the western Sinai Peninsula,

Egypt (Fig. 7). The boundary intervals are defined mainly usingforaminifer and ammonite biostratigraphy, and these were thenadjusted slightly to conform to the MS chron positions defined forthe U.S. Western Interior sections. Note that both marker eventsSa10 and Sa12 are identified in the Sinai Peninsula data set.

Correlation Among Sections Using MS Graphic Comparison

The graphic correlation method, as initially introduced byShaw (1964), involves graphical comparison between a hypo-thetical composite section built from a standard reference section(CRS) as a starting point, and a time-equivalent section. Fossiltaxa common to both sections are plotted as points on the graph.A line of correlation (LOC) is placed by visual inspection of graphdata-point arrays and is drawn to separate distributions of first(FA) and last (LA) appearances of taxa. The LOC is positioned tomaintain an “economy of fit.” That is, the LOC acts to separate amaximum number of taxa FAs and LAs. Graphic correlation isdesigned so that, based on projection through the LOC, the firstand last appearances of fossil taxa can be extended into the CRS(Edwards, 1982).

Here, rather than using biostratigraphic FAs and LAs, wesubstitute the beginning and ending of MS chrons from our datasets, respectively. The CRS thus developed serves as an MS

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FIG. 7.—MS data from the Wadi Sudr section in the western SinaiPeninsula, Egypt (E in Figure 1), covering the entire Santonianstage. Symbols and notations as in Figure 2. The Coniacian–Santonian and Santonian–Campanian boundaries are repre-sented by dashed lines and identified based on foraminifer

biostratigraphy and adjusted based on the MSEC zonationfrom the proposed GSSPs (Figs. 2, 3). Note the Sa 10 and Sa12marker events. Also given is the lithology for the section: mrl

= marl; ls = limestone; cal/ss = calc-sandstone; sh = shale; bsh= black shale. Arrows indicate T/R cyclicities (see text).

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standard, which acts as a starting point for approximatechronologic correlations and for building a magnetosusceptibilitycomposite section (MS CRS). To do this for the Santonian Stage,we started by graphically comparing the Niobrara Chalk com-posite (Fig. 5) against the two proposed Texas GSSPs (Figs. 2, 3).These are then compared in Figure 8 by plotting MS chron basesand tops from the two sections and fitting LOC segments throughthe data. The gap in MS chrons between the Ten Mile Creek andWaxahachie Spillway sections, between Sa4 and Sa7, is filled byprojecting the bases and tops from these chrons from the Niobrarasequence (Fig. 5), through the LOC and into the CRS. This then

becomes the U.S. Western Interior Seaway Composite MS CRS.Sediment accumulation rates and changes in rates between sec-tions can be interpreted from LOC segments; this is discussedfurther in a section below. In Figure 8, LOC segments 1 and 2 areoriented at ~ 45° , with an offset caused by rapid sedimentationwithin Sa11 in the Niobrara Composite. Thickness of theSantonian interval of the Niobrara sedimentary sequence is ~ 40m, whereas the Austin chalk represented by the two GSSPs is ~20 m thick, approximately half that of the Niobrara sequence.Therefore, both LOCs in Figure 8 indicate a more or less steadyaccumulation rate in the Niobrara and Western Interior com-

posites, with Niobrara sediments accumulating twice as fast asare Austin Chalk sediments. The exception is the Sa11 intervalin the Niobrara sequence, which appears to have accumulated

four times faster in the Niobrara Chalk than in the Austin Chalk of equivalent age.

Following this construction of the MS CRS, we test the qualityof the data by comparing the MS chrons from the Portland

USGS#1 Core from Colorado against the MS CRS (Fig. 9). Thereis a striking similarity between the two data sets, resulting in asingle LOC segment fit to the plotted MS bases and tops. Theslight variations observed among data points are the result of small differences in sedimentation rate within and between indi-vidual MS chrons. The effect of smoothing the data creates arobust data set that is resistant to small variations in accumula-tion rate or unconformities and allows correlations in spite of these problems.

An offset in LOC segments is observed when the Niobraraand Texas sequences are compared, appearing in MS chron Sa11(Fig. 8). However, there is no corresponding offset when com-pared with the Portland, Colorado, site (Fig. 9). Given the similar-ity between the Texas and Colorado data sets, this suggests thatthe change is restricted to the Kansas data set during deposition

of the Niobrara sequences. We conclude that this increase in ratewas either the result of an erosional pulse from the east, which isunlikely because the area was tectonically stable, or was due toincreased productivity during that time at the site, thus locallythickening MS chron Sa11.

The final step in this process was to compare the U.S. WesternInterior Seaway MS CRS with the section collected at Wadi Sudrin the western Sinai Peninsula, Egypt (Fig. 7). The results arestrikingly similar to those results observed in Figure 8. Two well-defined LOC segments are separated by an offset representing aperiod of relatively high sediment accumulation rate in the SinaiWadi Sudr section (Fig. 10). LOC segments 1 and 2 indicatesimilar sedimentation rates between the U.S. Western Interior

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FIG. 8: Graphic correlation of the Niobrara Composite (Fig. 5)

against the two proposed Texas GSSPs, Ten Mile Creek (Fig.2) and Waxahachie Spillway (Fig. 3). To complete the compos-ite labeled as the U.S. Western Interior Seaway Composite(MS CS), MS chrons Sa5 and Sa6 were projected from theNiobrara Composite through the Line of Correlation (LOC)into the x axis. Axes are labeled with the MS chron logs andnotation. Niobrara Composite height in meters; the CS unitsare arbitrary (CSUs) and tied to the spacing from the twoGSSPs used in Figures 2 and 3. Filled squares representcorrelation points of corresponding chron boundaries be-tween the two sections. Solid line is the LOC segments fit to thedata. Open squares represent the projection points on the LOCof MS chrons Sa5 and Sa6. Angles: LOC 1 ≈ 45°; LOC 2 ≈ 45°.

FIG. 9.—Graphic correlation of the Portland USGS#1 core (Fig. 4)against the U.S. Western Interior Seaway Composite Section(MS CS) developed in Figure 8. Axes are labeled with the MSchron logs and notation. The USGS#1 core heights are given,and the MS CS units are arbitrary (CSUs) and tied to thespacing from the two GSSPs used in Figure 8. Note that thePortland core ends somewhere in chron Sa 14 and does notreach the Santonian–Campanian boundary. Filled squaresrepresent correlation points of corresponding chron bound-aries between the core and the MS CS. Solid line is the line of correlation (LOC) fit to the data. Angle: LOC 1 ≈ 38°.

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Seaway and the Sinai Peninsula during the Early and LateSantonian. In addition, both areas appear to have experiencedtransgressive events during the Early Santonian, as interpretedfrom falling MS values (transgression arrows in Figs. 4, 5, and 6).However, following MS chron Sa11, while the Sinai Peninsulaexperienced regression (Fig. 7), the U.S. Interior Seaways seemsto have been relatively stable, with only climate cycles driving MSchanges (Figs. 4, 5).

Interpretations of the MS data

In very general terms, the MS magnitudes are similar in all thesections collected, and with a couple of exceptions most of thesample sets show only slight variations within sections. Weinterpret this to mean that factors causing many of the MSvariations that are present in these data sets are relatively subtle.The Austin Chalk sections in Ten Mile Creek and in the WaxahachieSpillway in Texas show an MS character that is very uniform,with only subtle cyclicity that might be interpreted from the data(Figs. 2, 3). There is a suggestion that a very slight regressive eventcan be identified in the Ten Mile Creek data set, culminating in theSa4 MS chron. A similar sea-level rise can be inferred for the baseof the Waxahachie sequence, culminating in marker event Sa10.As one moves toward detrital sources and farther into the U.S.Western Interior Seaway, as represented by the location of theUSGS#1 Core from Portland, Colorado, near the active tectonicprovince to the west (Dean and Arthur, 1998), the changes aremore pronounced (Fig. 4). MS values in the Upper Coniacian are

similar to those from the proposed GSSPs in Texas, but during MSchron Sa2 a distinctive transgressive event develops that endswithin MS chron Sa7, having the lowest MS values in the se-quence. The Sa8 chron represents a recovery associated with aslight regressive event, followed by a zone of relatively stablecyclicity that contains important marker events Sa10 and Sa12.During Sa13, MS values increase slightly and then become essen-tially non-varying within MS chron Sa14.

The Niobrara Chalk sequence (Fig. 5) exhibits an MS charac-ter very similar to that of the USGS#1 Core data set, beginningwith a transgressive event in the Lower Santonian and a regres-sive recovery to marker Sa10 after which there is relatively stablecyclicity. Again, MS values in the Upper Coniacian are similar tothose observed in the proposed Texas GSSPs. The magnitude of the transgressive event culminating in Sa7 is similar to thatobserved in the USGS#1 Core.

Examination of the Sinai Peninsula MS data set (Fig. 7) showssome striking similarities to the Niobrara Chalk sequence as wellas some pronounced differences. It is the similarities that allowcorrelation between the U.S. Western Interior Seaway sectionsand the Sinai Peninsula and result in the MS chron characterexhibited. We believe that this is due to two factors: erosional

cyclicity driven by climate, and discrete erosional events thatwere caused by local, Late Cretaceous tectonic processes, whichwere very different between the western U.S. and eastern Egypt.The end result is that while there is clear MS similarity in theLower Santonian, where MS values fall in both areas (globally),this is followed by relative stability in the U.S. Western InteriorSeaway but by a significant regressive event in the Sinai Penin-sula region during the Middle–Late Santonian. This regressiveevent results in a lithologic change in Wadi Sudr from limestonesto shales, and the highest MS values we have observed in Santoniansamples. This change in the Sinai Peninsula, when contrastedagainst the U.S. Western Interior Seaway (Fig. 10), produces anoffset in the LOCs shown that starts with a high sedimentationrate pulse beginning in MS chron Sa8. This pulse ends with Sa10and is followed by a slow but steady regressive event for the end

of the Santonian Stage in Egypt.Relative Sediment Accumulation Rates

from Line of Correlation (LOC) Segments

In all three correlation comparisons presented here (Figs. 8, 9,and 10), the main sedimentation rate is similar among sequences.There are two main LOC segments in Figure 8 (LOC 1 and LOC2), both oriented at ~ 45° on the graph, indicating that depositionduring these intervals was essentially constant within the Niobraraand the U.S. Western Interior composites. Between these two linesegments is a brief offset that occurs during MS chron Sa11 andrepresents either a rapid increase in sediment accumulation atthat time in the Niobrara Chalk sequence (Fig. 4) relative to theWaxahachie Spillway section (Fig. 3) or a slight unconformity inthe Waxahachie data set. Sediment accumulation rate then re-turns to a constant value (represented by LOC 2 in Figure 8). ThePortland Core data set (Fig. 5) yields a straight-line correlation

between the sequences presented (LOC 1 in Figure 9), indicatingthat the change in sediment accumulation rate that is observed inMS chron Sa11 in the Niobrara Composite is not present in thePortland Core, or that there is a slight unconformity in both theWaxahachie and Portland Core sections at the same level.

Comparison between the U.S. Western Interior Seaway Com-posite (MS CRS) and the Western Sinai Peninsula section, Egypt,yields a surprising result (Fig. 10). There are two LOC segments,each of which show similar values (~ 40°). In addition, there is anoffset in Figure 10 between LOC segments that is similar in

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FIG. 10.—Graphic correlation of the western Sinai Peninsula,Egypt section (Fig. 6) against the U.S. Western Interior SeawayComposite (MS CS) developed from Fig. 8 (see text). Sinai axisis labeled with height in section (m) as well as with the MSchron logs and notation. The MS CS units are arbitrary (CSUs)and tied to the spacing from the two GSSPs used in Fig. 8.Filled squares represent correlation points of correspondingchron boundaries between the two sections. Solid line is theline of correlation (LOC) fit to the data. Angles: LOC 1 ≈ 40°;LOC 2 ≈ 40°.

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magnitude to that observed when contrasting the Niobrara andU.S. Western Interior Seaway Composite (Fig. 8), but different intime. The Sinai Peninsula offset begins with high accumulationrates in MS chron Sa8, relative to the MS CRS, and ends in MSchron Sa10 (Fig. 10). Then, during Sa11, an offset occurs in theNiobrara composite. Both offsets are produced by higher sedimentaccumulation rates in the respective Niobrara (chalk) and SinaiPeninsula (limestone) sections. While the high accumulation ratein Sa 11 is assumed to have resulted from a high-productivityspurt, it is observed only within Sa11. However, the Sinai Penin-sula jump appears to have lasted three times longer, from Sa8until Sa10, although in part this may be an artifact of condensa-tion of chron Sa9 in the U.S. Western Interior Seaway composite.Given that Sa8 in the Sinai Peninsula is recorded in an expandedlimestone sequence, we interpret the jump between LOC 1 and 2to reflect an increased in local productivity at that time.

CONCLUSIONS

Magnetic susceptibility (MS) data sets from three geologicalsections collected from the U.S. Western Interior Seaway have

been used to establish a composite magnetostratigraphy suscep-

tibility MS chron zonation (an MS CRS) for the Upper CretaceousSantonian Stage. These sections include a composite of theNiobrara Chalk in Kansas covering the entire Santonian Stage,and the proposed GSSPs in Texas that bound the Santonian Stage.A regional test of the correlation power of the method wasprovided by comparison to an independent sequence, the USGS#1Core from Portland, Colorado, also from the U.S. Western Inte-rior Seaway. The correspondence was excellent when the MSchron zonation is compared between sections (Figs. 8, 9). The MSCRS was then compared to an equivalent section collected in thewestern Sinai Peninsula, Egypt, at Wadi Sudr, and again thecorrespondence was excellent (Fig. 10). Evaluation and interpre-tation of the MS data from these sequences indicates that therewas a eustatic sea-level rise in the Early Santonian represented inthe Kansas, Colorado, and Egyptian sections sampled. However,

during the Mid-Late Santonian in the U.S. Western InteriorSections, the MS shows relatively stable cyclicity, while in Egyptthere was a regression event lasting into the Campanian. Thisdifference is attributed to local synsedimentary tectonic uplift inEgypt during the Middle to Late Santonian, with relative tectonicstability during the same interval in the U.S.

ACKNOWLEDGMENTS

This project was funded in part by a U.S. National ScienceFoundation–Egypt Joint Science and Technology Board grant toBBE and AMK, grant #OTH6-008-002. Paleontological analysis of the Waxahachie section, as well as sampling of the Niobraraoutcrops in Kansas, were funded by a grant from BP Americas,Inc. to PJS. Sue Ellwood and Stephen Benoist are gratefullyacknowledged for their help in sampling a number of thesesections.

REFERENCES

BALSAM , W.L., AND BEESON , J.P., 2003, Sea-floor sediment distribution in theGulf of Mexico: Deep-Sea Research I, v. 50, p. 1421–1444.

BARNES , C., HALLAM , A., KALJO , D., KAUFFMAN , E.G., AND WALLISER , O.H.,1996, Global event stratigraphy, in Walliser, O.H., ed., Global Eventsand Event Stratigraphy: Berlin, Springer-Verlag, p. 319–333.

BAUER , J., MARZOUK , A.M., STEUBER , T., AND KUSS , J., 2001, Lithostratigraphyand biostratigraphy of the Cenomanian–Santonian strata of Sinai,Egypt: Cretaceous Research, v. 22, p. 497–526.

BELKA , Z., 1991, Conodont colour alteration patterns in Devonian rocks of the eastern Anti-Atlas, Morocco: Journal of African Earth Sciences, v.12, p. 417–428.

BURNETT , J.A., 1998, Upper Cretaceous, in Brown, P.R., ed., CalcareousNannofossil Biostratigraphy: London, Chapman & Hall, p. 132–199.

BURNS , C.E., AND BRALOWER , T.J., 1998, Upper Cretaceous nannofossilassemblages across the Western Interior Seaway: implications for

the origins of lithologic cycles in the Greenhorn and NiobraraFormations, in Dean, W.E., and Arthur, M.A., eds., Stratigraphy andPaleoenvironments of the Cretaceous Western Interior Seaway,USA: SEPM, Concepts in Sedimentology and Paleontology no. 6, p.35–58.

COWIE , J.W., ZIEGLER , W., BOUCOT , A.J., BASSETT , M.G.,AND REMANE , J., 1986,Guidelines and Statutes of the International Commission on Stratig-raphy (ICS): Courier Forschungsinstitut Senckenberg, no. 83, p. 1–14.

CRICK , R.E., ELLWOOD , B.B., EL HASSANI , A., FEIST , R., AND HLADIL , J., 1997,Magneto Susceptibility event and cyclostratigraphy (MSEC) of theEifelian–Givetian GSSP and associated boundary sequences in NorthAfrica and Europe: Episodes, v. 20, p. 167–175.

DEAN , W.E., AND ARTHUR , M.A., 1998, Cretaceous Western Interior Seawaydrilling project: An overview, in Dean, W.E., and Arthur, M.A., eds.,Stratigraphy and Paleoenvironments of the Cretaceous Western Inte-

rior Seaway, USA: SEPM, Concepts in Sedimentology and Paleontol-ogy no. 6, p. 1–10.

DUPUIS , C., AUBRY , M., STEURBAUT , E., BERGGREN , W.A. , OUDA , K.,MAGIONCALDA , R., CRAMER , B.S., KENT , D.V., SPEIJER , R.P.,AND HEILMANN-CLAUSEN , C., 2003, The Dababiya Quarry Section: Lithostratigraphy,clay mineralogy, geochemistry and paleontology: Micropaleontol-ogy, v. 49, supplement 1, p. 41–59.

EDWARDS , L.E., 1982, Quantitative biostratigraphy: the method should suitthe data, in Cubitt, J.M., and Reyment, R.A., eds., Quantitative Strati-graphic Correlation: New York, John Wiley & Sons, p. 45–60.

ELLWOOD , B.B., BALSAM , W., BURKART , B., LONG , G.J., AND BUHL , M.L., 1986,Anomalous magnetic properties in rocks containing the mineralsiderite: Paleomagnetic implications: Journal of Geophysical Re-search, v. 91, p. 12,779 –12,790.

ELLWOOD , B.B., HROUDA , F., AND WAGNER , J.-J., 1988a, Symposia on mag-

netic fabrics: Introductory comments: Physics of the Earth and Plan-etary Interiors, v. 51, p. 249–252.ELLWOOD , B.B., CHRZANOWSKI , T.H., HROUDA , F., LONG , G.J., AND BUHL , M.L.,

1988b, Siderite formation in anoxic deep-sea sediments: a synergetic bacterially controlled process with important implications in paleo-magnetism: Geology, v. 16, p. 980–982.

ELLWOOD , B.B., BURKART , B., RAJESHWAR , K., DARWin, R.L., NEELEY , R.A.,MCCALL , A.B., LONG , G.J., BUHL , M.L., AND HICKCOX , C.W., 1989, Are theiron carbonate minerals, ankerite and ferroan dolomite, like siderite,important in paleomagnetism?: Journal of Geophysical Research, v.94, p. 7321–7331.

ELLWOOD , B.B., CRICK , R.E., AND EL HASSANI , A., 1999, The magneto-susceptibility event and cyclostratigraphy (MSEC) method used ingeological correlation of Devonian rocks from Anti-Atlas Morocco:American Association of Petroleum Geologists, Bulletin, v. 83, p.1119–1134.

ELLWOOD , B.B., CRICK , R.E., EL HASSANI , A., BENOIST , S., AND YOUNG , R., 2000,Magneto Susceptibility event and cyclostratigraphy (MSEC) in ma-rine rocks and the question of detrital input versus carbonate produc-tivity: Geology, v. 28, p. 1135–1138.

ELLWOOD , B.B., CRICK , R.E., GARCIA-ALCALDE FERNANDEZ , J.L., SOTO , F.M.,TRUYOLS-MASSONI , M., EL HASSANI , A., AND KOVAS , E.J., 2001, Globalcorrelation using magnetic susceptibility data from Lower Devonianrocks: Geology, v. 29, p. 583–586.

ELLWOOD , B.B., MACDONALD , W.D., WHEELER , C., AND BENOIST , S.L., 2003,The K–T boundary in Oman: identified using magnetic susceptibilityfield measurements with geochemical confirmation: Earth and Plan-etary Science Letters, v. 206, p. 529–540.

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ELLWOOD , B.B., GARCÍA-ALCALDE , J.L., EL HASSANI , A., HLADIL , J., SOTO ,F.M., TRUYÓLS-MASSONI , M., WEDDIGE , K., AND KOPTIKOVA , L., 2006,Stratigraphy of the Middle Devonian boundary: formal definition of the susceptibility magnetostratotype in Germany with comparisonsto sections in the Czech Republic, Morocco and Spain:Tectonophysics, v. 418, p. 31–49.

GRADSTEIN , F.M., OGG , J.G., AND SMITH , A.G., 2004, A Geologic Time Scale

2004: Cambridge, U.K., Cambridge University Press, 589 p.HANCOCK , J.M., AND GALE , A.S., 1996, The Campanian Stage, in Rawson,

P.F., Dhondt, A.V., Hancock, J.M., and Kennedy, W.J., eds., Proceed-ings of the Second International Symposium on Cretaceous StageBoundaries, Brussels, 1995: Institut Royal des Sciences Naturelles deBelgique, Bulletin, Sciences de la Terre, v. 66, supplement, p. 103–110.

HATTIN , D.E., 1982, Stratigraphy and Depositional Environment of SmokeyHill Chalk Member, Niobrara Chalk (Upper Cretaceous) of the typearea, western Kansas: Kansas Geological Survey, Bulletin 225, 108 p.

HROUDA , F., 1994, A technique for the measurement of thermal changes of magnetic susceptibility of weakly magnetic rocks by the CS-2 appa-ratus and the KLY-2 Kappabridge: Geophysical Journal Interna-tional, v. 118, p. 604–612.

KARLIN , R., AND LEVI , S., 1985, Geochemical and sedimentological controlof the magnetic properties of hemipelagic sediments: Journal of

Geophysical Research, v. 90, p. 10,373–10,392.KASSAB , A.S.,AND ISMAEL , M.M., 1996, Biostratigraphy of the Upper Creta-

ceous sequence of the Gebel Musabaa Salama area, southwest Sinai,Egypt: Arab Gulf Journal of Scientific Researches, v. 14 (1), p. 63–78.

NAGATA , T. , 1961, Rock Magnetism: Tokyo, Maruzen Company Ltd.,350 p.

NYE , J.F., 1990, Physical Properties of Crystals: New York, Oxford Univer-sity Press, 329 p.

OBAIDALLA , N.A., AND KASSAB , A.S., 2002, Integrated biostratigraphy of theConiacian–Santonian Sequence, southwestern Sinai, Egypt: Egyptian

Journal of Paleontology, v. 2, p. 85–104.POWELL , J.D., 1970, Summary of Upper Cretaceous stratigraphy: the Gulf

of Mexico Province: First Interamerican Micropaleontological Collo-quium, Field Trip Guidebook, Dallas, Texas, p. 9–36.

SALVADOR , A., ed., 1994, International Stratigraphic Guide: A Guide to

Stratigraphic Classification, Terminology, and Procedure, SecondEdition: International Union of Geological Sciences (IUGS) and theGeological Society of America (GSA) co-publishers, 214 p.

SCOTESE , C.R., 1998, PALEOMAP Animations: PALEOMAP Project, VideoDisk.

SHAW , A.B., 1964, Time in Stratigraphy: New York, McGraw Hill, 365 p.SILVA , I.P., AND SLITER , W.V., 1999, Cretaceous paleoceanography: Evi-

dence from planktonic foraminifer evolution, in Barrera, E., and Johnson, C.C., eds., Evolution of the Cretaceous Ocean–ClimateSystem: Geological Society of America, Special Paper 332, p. 301–328.

SWARTZENDRUBER , L.J., 1992, Properties, units and constants in magnetism: Journal of Magnetic Materials, v. 100, p. 573–575.

TARLING , D.H., AND HROUDA , F., 1993, The Magnetic Anisotropy of Rocks:London, Chapman & Hall, 217 p.

WEEDON , G.P., JENKYNS , H.C., COE , A.L., AND HESSELBO , S.P., 1999, Astro-nomical calibration of the Jurassic time-scale from cyclostratigraphyin British mudrock formations: Royal Astronomical Society (Lon-don), Philosophical Transactions, v. 357, p. 1787–1813.

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