56. LITHOLOGIC FINDINGS OF DSDP LEG 42A, …

56. LITHOLOGIC FINDINGS OF DSDP LEG 42A, MEDITERRANEAN SEA

Robert B. Kidd,1 Daniel Bernoulli,2

Robert E. Garrison,3 Frank H. Fabricius,4 Frederic Mélières,5

ABSTRACT

This contribution records the most striking sedimentologicalfindings of Leg 42A and outlines the scope for further research onrecovered core materials. It emphasizes the use of comparativesedimentology as a tool in environmental interpretation and derivessupport for these interpretations from other lines of evidence, inparticular faunal analyses and geophysical studies.

Sedimentological analyses of the pre-Messinian sequences,extensively drilled for the first time during this cruise, show thatthey are typically of a basinal facies: pelagic to hemipelagicsediments with turbidites. Pre-Messinian water depths derived fromanalyses of benthic foraminifers and ostracodes confirm thesefindings. The sites, however, occupy substantially different tectonicsettings at the present day.

All of the depositional sequences drilled from the upper part ofthe Mediterranean evaporite formation, of Messinian age, canconfidently be referred to subaerial or shallow subaqueous environ-ments, although in the Ionian and Antalya basins these werereplaced in the late Messinian by an oligohaline "Lago Mare"facies.

Post-Messinian sequences are again typically basinal, hemipe-lagic, and frequently turbiditic and are similar to those recovered inpiston cores of Holocene and Pleistocene sediments. Sediments ofthis facies date from the Miocene/Pliocene boundary and faunalanalyses show that early Pliocene water depths were at least 1000-1500 meters.

A review of the clay mineralogical results shows the primaryinfluence of terrigenous sources and records the possible genesis ofcertain clay minerals in the desiccated environments of the Messin-ian. Sapropel layers are recognized to be more numerous thanpreviously thought and are shown to date back as far as the middleMiocene. Conversely, tephra layers are, somewhat unexpectedly,poorly represented in the recovered material. Considerable scoperemains for studies on both sapropel and tephra chronology. Acomplex history of sedimentation upon a volcanic Tyrrhenianseamount has been established and isotopic estimates of brecciacementation temperatures confirm that the seamount was in a deepwater environment in the early Pliocene.

Four of the authors (R.B.K., D.B., R.E.G., F.M.) feel that thenature of the Messinian evaporites—shallow subaqueous to subaer-ial deposits, sandwiched between typically basinal, hemipelagic,Burdigalian to Tortonian and Pliocene to Holocene sequences-together with corroborative evidence from geophysical studies,strongly supports the deep-basin desiccation hypothesis for theMediterranean during the late Miocene.

institute of Oceanographic Sciences, Wormley, Surrey, U.K.2 Geologisch-palàontologisches Institut, Universitat Basel, Switz-

erland.3Earth. Sciences Board, University of California, Santa Cruz,

California.4Institut für Geologic Technische Universitat, München, W. Ger

many.5Laboratoire de Géologie Dynamique, Université de Paris,

France.

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R. B. KIDD ET AL.

INTRODUCTION

Glomar Challenger returned to the MediterraneanSea in April and May of 1975 for Deep Sea DrillingProject Leg 42A, and drilled 10 holes at eight separatesites. Five years earlier, during Leg 13, 28 holes hadbeen drilled at 15 site locations (Figure 1). From theshipboard participants evolved a late Neogene andQuaternary stratigraphy for the Mediterranean deep-sea areas (Ryan, Hsü, et al, 1973). This immediatelyprovoked considerable debate concerning its paleoenvi-ronmental significance, because a Pliocene-Quaternarysedimentary sequence, similar in all respects to sedi-ments being deposited in modern deep-sea basins,directly overlies late Miocene (Messinian) evaporiterocks, which were comparable with those forming inthe subaerial and shallow water environments of thepresent-day Persian Gulf.

Two of the prime objectives of this second cruisewere to extend the stratigraphy of the deep basins tobefore the Messinian in order to establish paleoenvi-ronments prior to the evaporite deposition; and byincreased core recovery, to study in more detail envi-ronments during and after deposition of the evaporite.

Generalized sediment sequences drilled by Leg 42Aare shown in Figure 2. Site 372 on the Menorca marginand the composite section resulting from Sites 375 and376 on the Florence Rise are especially significant inthat we recovered material from the overlying Pliocenesediments, through the Messinian evaporite and intothe underlying pre-Messinian sediments.

The purpose of this contribution is to draw togetherthe more significant lithologic findings contributed bydrilling during Leg 42A. Discussion of the tectonichistory of the Mediterranean basins and of the genesisof the Messinian evaporite formation appear in themain synthesis chapter of this volume (Hsü et al., thisvolume). We record here the sedimentological findingsthat are detailed in the contributions to Part II of thisvolume. We stress some especially significant featuresand outline possible further research studies on thesediments. The Leg 42A cores are now stored at theDSDP East Coast Repository at Lamont-Doherty Geo-logical Observatory, New York.

When drilled sections are calibrated to seismicprofiles, a three-dimensional picture of the stratigraphyof a basin emerges. For the finer scale, however,scientists rely heavily upon comparative sedimentologyas a tool in interpreting the lithologies encountered.Sedimentologists aboard Glomar Challenger studycores up to 9.5 meters long, but these cores are notalways taken continuously (only 79 of the 150 Leg 42Acores are part of continuously cored sequences), andthey are only 6.5 cm in diameter. In order to build adetailed three-dimensional picture we rely heavily,therefore, upon comparison with land sections andsediments being deposited at the present time. Ourdescriptive terminology reflects this process. For exam-ple, the term "pelagic" when used for carbonatesediments means a fairly pure biogenic ooze which issimilar to those deposited in certain open sea regions at

the present time, "hemipelagic" sediments signifiesthose which have received a significant contribution ofland-derived sand, silt, and clay material. Because ofthe geography of the present-day Mediterranean sedi-ments of the latter type are particularly important.Neither term, however, is specific with respect to waterdepth at the site of deposition. We thus rely uponestimates of water depths from faunal assemblages forconfirmation, or otherwise, of environmental interpre-tations on the basis of comparative sedimentology.

We discuss the pre-Messinian, Messinian, and post-Messinian sediment sequences separately, and weemploy comparative sedimentology for environmentalanalysis and examine the faunal evidence in each case.We deal with the pre-Messinian sediments site by siteand in greatest detail, because no specific chapters aredevoted to them in this volume. The results of studiesof clay mineral assemblages is presented in a latersection, with emphasis placed on the sources of the finesediment fractions. Intercalations in the sediment se-quences, representing specific events in the history ofdeposition, are considered in succeeding sections de-voted to sapropel and tephra layers. Finally, we con-sider the effects of submarine volcanic activity on seafloor sediments, which resulted in the basaltic brecciasequence of Hole 373A on one of the Tyrrhenianseamounts.

PRE-MESSINIAN SEDIMENTS

Prior to the Leg 42A, hemipelagic and turbiditicsediments, interpreted as deep water sequences, wereknown to underlie the Mediterranean Evaporite For-mation at many places on land. However, these depos-its were in part violently folded during the Plioceneand the Quaternary, and even though the evaporitesare often sandwiched between hemipelagic and pelagicdeposits, the evidence for a deep basin in whichdesiccation occurred during the late Miocene was notaccepted as unequivocal (cf. Drooger, 1973). Thus therecovery of pre-evaporitic sediments in a postorogenic,extensional, and subsiding setting was of prime impor-tance for the establishment of the tectonic and deposi-tional environment in which the evaporite depositionoccurred.

Pre-evaporitic sediments had been drilled duringDSDP Leg 13 at Sites 121 and 126. At Site 121 in theAlboran Basin, 178 meters of hemipelagic marls, ofTortonian (Ryan, Hsü, et al., 1973) or pre-evaporiticMessinian (Montenat et al., 1975) age, with turbiditicsandstones, were encountered below a Miocene-Plio-cene unconformity. At Site 126, only a few meters ofSerravallian marls were recovered from a cleft in theMediterranean Ridge (Ryan, Hsü, et al, 1973). DuringLeg 42A pelagic, hemipelagic and turbiditic, pre-evaporitic, early to middle and late Miocene sedimentswere recovered at Sites 372, 375, and 377.

The Messinian evaporites and their underlying sedi-ments today occur in different tectonic settings. Thesequence drilled at Site 372 on the Menorca Rise wasdeposited along a rifted and down-faulted margin(Mauffret et al., 1973) which came into existence

1080

LITHOLOGIC FINDINGS, MEDITERRANEAN SEA

40°

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30fN10° 20° 40°E

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Figure 1. Index map showing Leg 42A sites in relation to those of Leg 13.

during the Oligocene and which has been subsidingever since (Biju-Duval et al., this volume; Wright, thisvolume). Sites 375-376 are on the Florence Rise, ayoung Pliocene-Pleistocene compressional belt (Biju-Duval et al., 1974). Finally, at Site 377 we redrilled alarger section of pre-evaporitic sediments near Site 126in the Mediterranean Ridge.

At all these three sites, the Mediterranean evaporiteformation overlies, either directly or unconformably,typical basinal, hemipelagic, pelagic, and turbiditicsediments. Two major fades were encountered: at Site372 there are homogeneous, intensely burrowed marlsand marlstones overlying dark colored marlstones tomudstones. At Site 375 a cyclic sequence of terrigenousturbidites was found overlying pelagic and hemipelagicmarls and limestones with minor intercalations ofredeposited pelagic carbonates. At Site 377, recoverywas very poor: here the middle to early Mioceneconsists of gray nannofossil marlstones underlain bydark gray flysch-like mudstones, siltstones, and sand-stones.

Facies and General Lithology

Site 372

Near Menorca, pre-Messinian sediments, extendingfrom below the evaporites of the Balearic AbyssalPlain, directly underlie Pliocene-Quaternary sedimentsor even outcrop. At Site 372, these sediments occurbelow a thin sequence of the upper evaporitic memberwhich pinches out towards the margin. They areseparated from the evaporites by an unconformitywhich represents a hiatus of 6 m.y. (see Site 372Report, this volume). The upper part of the sequence(lithologic Unit III, 199.5-468 m sub-bottom and lateBurdigalian to Serravallian in age) consists of light

bluish gray to greenish gray homogeneous nannofossilmarls, which gradually pass into more lithified lime-stones below. The sediment is intensely burrowedthroughout, with Planolites- (Figure 3), Zoophycos-and Chondrites-type burrows, which generally aretypically associated with fine-grained sediments ofdeeper waters (Ekdale, this volume). Resedimentationdoes not occur in these hemipelagic deposits, except forhighly contorted intervals (Cores 24-26) which mightrepresent submarine slumping. At about 470 meterssub-bottom, a pronounced break in sedimentationoccurs which corresponds to a seismic reflector. Fromlithologic Unit III to Unit IV (468-885 m sub-bottom,Burdigalian), the carbonate content drops from 65% to30% with a corresponding increase in detrital minerals.Near the base of Unit IV (Cores 44-46) a few intercala-tions of graded and laminated quartzose sandstone tosiltstone, lithic sandstone and silty limestone arepresent.

In both units, quartz, mica (illite), and chloritecorrelate well with one another indicating a terrigenousorigin for the non-carbonate fraction. Only near thebase of Unit III does an increase in the smectite contentand the presence of neomorphic clinoptilolite (Figure4) suggest derivation from volcanic material. More-over, in this interval considerable volcanic material isfound in the heavy mineral fraction. In Unit IV, appre-ciable amounts of Opal-CT (Jones and Segnit, 1971, adisordered interstratification of oc -cristobalite and oc-tridymite) is present. This is obviously derived frombiogenic silica, as it occurs as lepispheres lining moldsof radiolarians (Figure 5).

The pre-Messinian hemipelagic sediments of Site372 are similar to those deposited there today. Plank-tonic and benthic fauna and flora are fully openmarine and trace fossils are those typical for fine-

1081

R. B. KIDD ET AL.

grained sediments of deeper waters. Quantitative anal-ysis of the benthic communities by Wright (this vol-ume) shows an increase in water depth from approxi-mately 900 meters in the early Burdigalian to 1500meters at the end of the Serravallian.

These depths concur well with the depth ranges thatcan be inferred from the general lithology. A markedchange in depositional environment and rate of sedi-mentation obviously occurred between Units III and IVduring the late Burdigalian. Geophysical profiles showthat the Unit IV sediments were ponded between base-ment horsts towards the end of the early founderingstage of the margin, whereas Unit III sediments occur asa wedge burying the pre-existing relief.

Site 375

At Site 375, the pre-evaporitic Neogene sedimentsshow a typically cyclic development. They comprise400 meters of dark gray, flysch-like sediments ofTortonian age (Unit IV), overlying over 200 meters ofvariegated marlstone and claystone, which are inter-preted as distal turbidites, alternating with pelagicmarlstone to limestone and turbidites composed ofpelagic material only (Units VIII through XI, Burdigal-ian to Serravallian).

In Unit VII of this site the thickness of individualcycles varies from 10 cm to more than 1 meter. Thecycles typically start with fine terrigenous arenite tosiltite and have sharp lower boundaries (Figure 6).This grades upwards into homogeneous and structure-less marlstone overlain in turn by marlstone withsparse burrowing. The sandstones and siltstones areinterpreted as the "a-d" intervals of Bouma cycles(Bouma, 1962): the homogeneous marlstone as thefinest fraction transported by the turbidity current andthe burrowed marlstones as the top of the turbiditicmarlstone and/or the "normal" hemipelagic interval.Organic carbon-rich nannofossil marlstones ("sapro-pels") which occur, may also be partly redeposited, asis shown by distinctly graded and cross-laminatedexamples.

In Units VIII through XI, intercalations of gradedand laminated siltitεs occur only rarely. Here the cyclestarts with variegated or gray marlstones to claystoneswith a sharp lower boundary. These grade upwardsinto light colored, more calcareous and foram-richmarlstones and limestones. Typically the tops of thedarker layers are intensely burrowed from the top withlighter sediment piped down and older burrows bur-rowed again by younger and usually smaller ones(Figures 7 and 8). We interpret these cm- to dm-thickcycles as distal turbidites of terrigenous and hemipe-lagic material overlain by "normal" pelagic to hemipe-lagic sediment. In Unit X (Langhian), still anothertype of resedimented layer has been observed. Thiscomprises light gray to bluish white, hard, cementedlimestones which are composed entirely of tests ofplanktonic foraminifers and which often show pro-nounced size grading and low-angle current lamina-tions (see fig. 13 in Site 375/376 Report, this volume).The sedimentary structures of these pelagic turbidites

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1083

R. B. KIDD ET AL.

-35

Figure 3. Homogeneous greenish gray marl-stone with small Chondrites-fype and largePlanolites-fype burrows. Lithologic UnitIII, Langhian, Sample 372, 28-3, 30-40cm. Scale bar: 2 cm.

Figure 4. Neomorphically formed clinoptilolite crystals inforaminiferal shells. Unit HI, late Burdigalian, Sample372-33-3, 33 cm. SEM-micrographs. Scale bars: 5 µm.

are similar to those described from other deep-seasequences (Bernoulli, 1972; Cook et al, 1976; Hesse,1975).

The very close correlation between the pre-Messin-ian Neogene sediments at Site 375 and the KythreaGroup of northern Cyprus leaves no doubt that bothsequences have been deposited in the same deposi-tional basin (Baroz et al., this volume). On Cyprus thethicknesses of the individual formations of the KythreaGroup and the amount of terrigenous material de-crease from east to west, and hence toward Site 375.This is consistent with current directions during deposi-tion of this group in which the terrigenous elasticsindicate sediment transport from east to west (Weiler,1963). It appears that the Kythrea Group and itsequivalents at Site 375 were deposited in a narrowdeep east-northeast-trending trough between the Tau-rus Mountain to the north and the Troodos High to thesouth (cf. Weiler, 1970). Much of the terrigenousmaterial was derived from ophiolitic and volcanicterrains and apparently was brought into the basin bylarge rivers (the ancestral çeyhan and Seyhan rivers)which drained large ophiolitic areas of the Bitlis-Misisbelts. Terrigenous sandstones and siltstones containlithic fragments of mafic volcanics and some metamor-phic and carbonate rocks, mainly dolomite, quartz,plagioclase, amphibole, and biotite. Smectites are thedominant clay minerals, followed by chlorite andattapulgite with traces of illite and kaolinite. Othersources of sediments apparently were the ancestral,Oligocene-Miocene Pentadaktylos (Kyrenia) Range ofCyprus, from the flanks of which the turbidites contain-ing shallow water organisms of the Kythrea Groupwere derived, and the Troodos High, from whichissued turbidity currents that transported pelagic mate-rial only (Panagra Marls and Unit X Site 375, cf.Baroz et al., this volume).

The Kythrea Group and the Neogene sequence ofSite 375 coarsen upwards, but, during the Tortonian,water depth was still in excess of 1000 meters as shownby benthic foraminifers (Wright, this volume). Deposi-tion took place in a basin that was semireducing andepisodically was even stagnant, as is suggested by theabundance of organic matter and by the generally poorbenthic assemblages.

Site 377At Site 377 recovery was very poor. However, the

presence of middle to early Miocene nannofossilmarlstones and flysch-like lithic arenites indicates thatthis site was already in a basin prior to the salinitycrisis and the deformation of the Mediterranean Ridge.

DiagenesisAt Site 372 the pre-evaporitic sediments show a

general increase in induration and lithification withdepth. Seismic reflection data indicate a progressiveincrease in the density of the sediments downhole, andthe parallel decrease in water content represents adecrease in porosity. Compaction in the mudstone ofUnit IV is indicated by flattened burrows. In Unit III,SEM-micrographs show a gradual increase in over-growth on discoasters and on the distal shields ofplacoliths with depth. The results of preliminary iso-tope studies (McKenzie et al., this volume) indicate a

1084


Figure 5. Radiolarian mold lined by lepispheres of opal-CT. Unit IV, Burdigalian, Sample 372-36-5, 48-54 cm.SE-Micrographs. Scale bars: left 20 µm, right 2 µm.

down-hole depletion in the oxygen-18 content of thebulk carbonate, which is directly associated with theprogressive lithification of the sediment. This O18 shiftresults from the isotopic re-equilibration of the carbon-ate ions during cementation and recrystallization at

Further research on these pre-Messinian deep-seasediments should be directed toward analyses of theirlithification history through further SEM and isotopestudies. Identification of the sources of heavy and clayminerals would also be a fruitful line to follow, but westress that increased knowledge of related land sectionshigher temperatures, whereby the O18 value of the bulkcarbonate becomes progressively more negative withincreased burial depth while the pore waters take upthe released O18 (McKenzie et al., this volume).

At Site 375 a similar increase of induration andlithification with depth was observed; this is alsoparalleled by an increase in sonic velocity. As at Site372, the calcareous nannoplankton shows progressiveovergrowth by syntaxial calcite with depth. As well asdetrital (stoichiometric) dolomite, small neomorphi-cally formed (calcian) dolomite rhombs are present. InUnit X, hard limestone layers consisting exclusively ofredeposited planktonic foraminifers occur. These havebeen tightly cemented by syntaxial and blocky, usuallyferroan, calcite cements (Figure 9); rarely occurringcoccoliths in these layers show extensive overgrowth bysyntaxial calcite. Some of the hard cemented lime-stones in Unit X have faint, closely spaced solutionseams parallel to bedding which may represent theearliest stages of flaser-development. They also havestylolites which are oblique and perpendicular tobedding.

Conclusions and Further Research

Sedimentological analyses of the pre-Messinian se-quences at Sites 372, 375, and 377 suggest that theyare typically of a basinal facies: pelagic to hemipelagicsediments with turbidites, although they occupy sub-stantially different tectonic settings at the present day.Faunal analyses of benthic foraminifers (Wright, thisvolume), ostracodes (Benson, this volume), and tracefossils (Eckdale, this volume), confirm the lithologicinterpretations throughout. More specifically, theyshow that water depths at Site 375 prior to the salinity

-30

- 4 0

Figure 6. Terrigenous turbidite, overlying burrowed hemi-pelagic marlstone with a sharp erosional contact. Tur-bidite is graded and laminated fine lithic arenite tosiltite which passes upwards into homogeneous, darkgray turbiditic marl. Unit VII, Tortonian, Site 375,Section 4-3, Scale bar: 2 cm.

1085

R. B. KIDD ET AL.

-30

-40

to light gray pelagic to hemipelagic marhtone, rich inplanktonic foraminifers. The contact between the darkturbiditic and the light pelagic sediment is stronglymodified by Zoophycos-type burrows which are filledwith light sediment from above. At 31 to 32 cm, a thinintercalation of dark mudstone is present which ispartly replaced by light sediment infilling small Zoophy-cos-type burrows. The light pelagic sediment above ap-pears to be completely homogenized by burrowing.Unit IX, Serravallian, Site 375, Section 9-3. Scale bar:2 cm.

crisis (in the Tortonian) were at least 1000 meterswhile, despite a 6-m.y. hiatus, below the evaporites,Site 372 subsided to at least 1500 meters by Serraval-lian time (Wright, this volume).would be required. In fact we urge that further re-gional sedimentary studies, especially on Menorca andCyprus, be instigated in order to examine some of themore important tectonic implications raised by the

Figure 7. Characteristic cycle in Lithologic Unit IX, Site375. Dark gray turbiditic mudstone passes upwards in-

Figure 8. Typical example of distal pelagic turbidite,Unit X, Site 375. Laminae of light gray, calcisiltite com-posed of small, size-sorted planktonic foraminifers,alternating with and grading into red marhtone; burrowsare filled with calcisiltite and larger planktonic foram-inifers and are partly reburrowed. In the turbiditic marl-stone (upper part of photograph) larger planktonicforaminifers were introduced from the overlying lime-stone by burrowing. Unit X, Langhian, Sample 375-10-2, 93-98 cm, negative print from thin section. Scalebar: 5 cm.

1086

LITHOLOGIC FINDINGS, MEDITERANNEAN SEA

Figure 9. Foraminiferal lime grainstone (pelagic tur-bidite), composed entirely of planktonic foramin-ifers, partly with geopetal infill of micrite andcemented by syntaxial calcite. Unit X, Langhian,Sample 375-11-1, 125-130 cm, thin section, (A)parallel nicols, (B) crossed nicols. Scale bar:0.5 mm.

results from these drilled sections (see Hsü et al, thisvolume).

MESSINIAN EVAPORITES

Leg 42A recovered Messinian evaporitic rocks andsediments at eight locations: Sites 371, 372, 374, 375,376, and 378 (Figure 1). Bear in mind, however, that,from comparison with seismic profiles, sediments wererecovered only from the upper part of the Mediterra-nean evaporite formation. They only sample the upper70 or so meters of a formation which can be up to 2km thick. We continuously cored over 278 meters but,as is usual in such rocks, recovery was fragmentary andaveraged 34% in the individual cores. This recovery,however, is significantly better than on Leg 13 wherethe Messinian evaporites were sampled at seven sites,201 meters were continuously cored and recovery was24%.

Apart from fragmentary recovery, sedimentologicalanalysis is here even more seriously handicapped bythe small diameter of the cores than is the case forother rock types. Assessment of lateral continuity isparticularly important in the interpretation of evaporite

sequences (Dean et al., 1975; Von der Haar, 1976).Thus we relied heavily for comparison upon our exam-ination of the late Miocene evaporites of Sicily andSpain, and upon the observations of other workers inthese areas and elsewhere in the Mediterranean. Thesesequences are, for the most part, barren of microfossilswhich further limit our ability to check the paleoenvi-ronmental interpretations. On the other hand, consider-able information can be gleaned from comparisonsmade with modern analogues (Schreiber, 1974; Schrei-ber and Friedman, 1976) and this approach hasallowed us to identify paleoenvironments, at leasttentatively, for all the rock types recovered. Thesestudies are reported fully in Garrison et al., thisvolume).


The evaporite sequences are extremely diverse in thedrilled sections. Each site had a somewhat differentsuccession of rock types.

Site 371 has nodular anhydrite overlying dolomiticmudstone and is interpreted as part of a progradingsabkha cycle. Laminated gypsum, containing cross-bedding, ripple marls, and other indications of currentdeposition dominates at Site 372. This suggests thatthis gypsum may have been deposited on a veryshallow water evaporite flat that was periodicallyexposed. The sequence contrasts markedly with thecoarse selenitic gypsum at the bases of the holes drilledat Site 378. The latter was probably precipitated in ashallow body of water into which there were influxesof less saline water that caused the dissolution andreworking effects observed. A halite to marlstonesequence occurs at Site 374, and the upper part of thissequence contains several gypsum-dolomitic mudstonecycles. Coring at Sites 375 and 376 recovered a some-what similar Messinian sequence with halite at thebase, but rather thick dolomitic marlstone and clasticgypsum deposits dominate the upper part of thissuccession and indicate considerable reworking ofevaporites as well as probable deepening of the water.

The last Messinian sediments at Sites 374, 375, and376 are dolomitic marls and marlstones sometimesinterbedded with turbiditic arenite and siltites. Theseare the deposits of a standing body of water, markedlyless saline and possibly of considerable depth (the"Lago Mare" of Hsü et al., this volume).

The variability between sites summarized abovereflects the variability and complexity of depositionalenvironments in the Mediterranean region duringMessinian time. The evaporites at all the sites, however,share in common indications of deposition and diagen-esis in very shallow subaqueous to subaerial environ-ments.

Gypsum-Mudstone Cycles

Drilling at Site 374 recovered five cores whichpenetrated an apparently cyclically bedded sequence ofmudstones and gypsum, between sub-bottom depths406.5 and 425.5 meters (Figure 10). Despite onlypartial lecovery, we were able to construct an idealized

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R. B. KIDD ET AL.

three-member cycle and to examine in detail eachmember (cf. fig. 17 of Garrison et al., this volume).The cycles appear to record slight changes in waterlevel that caused periodic fluctuations betweensubaqueous and subaerial sedimentation. This site, inone of the deepest parts of the present Mediterranean,also contains algal stromatolites and algal filaments,which, because of the light dependence of these organ-isms, confirms our interpretations regarding waterdepths during this part of the Messinian (Awramik,this volume).

Laminated Gypsum

Laminated gypsum is conspicuous at Sites 372, 374,375, and 376 and appears to have several differentorigins. One variety formed through periodic redeposi-tion of clastic gypsum grains by currents. In anothertype, recrystallization of the redeposited gypsum grainsoccurred during early diagenesis and acted to accentu-ate inverse size grading of particles within the laminae.A third variant originated when vertical growth of

small selenite crystals up from the sediment-waterinterface was periodically interrupted by deposition ofclastic gypsum particles or carbonates (Figure 11).


Although lack of fossils and incomplete core recov-ery present problems of precise correlation betweenevaporite sections, we are able to demonstrate that,through comparative sedimentology, all these deposi-tional sequences from the upper part of the Mediterra-nean evaporite formation can confidently be referredto subaerial to shallow subaqueous environments. Inthe Ionian and Antalya basins such conditions weresucceeded by the late Messinian oligohaline "LagoMare."

The Leg 42A evaporites contain a number of fea-tures worthy of further investigation. Among these arelaminated gypsum, coarse recrystallization fabrics, ofdiagenetic or metamorphic origin at Sites 374 and 376,clastic gypsum at Site 376, and selenitic gypsum andgypsum dissolution breccias at Site 378.

CORE 16 CORE 17 CORE 18 CORE 19 CORE 20

SBD407 m

SBD411 m

SBD417 m

SBD418 m

SBD420 m

407.8

WavyBedded

toNodularGypsum84 cm (C)

Scale0

5

10 cm

412.2

CoarseGypsumVein,3 cm

417.5m

Gray Mudstonein part laminated,in part diatomaceous,with secondarygypsum crystals,94 cm (A)

WavyBeddedGypsum,22 cm (C)

Mudstone8 cm (A)WavyBeddedGypsum,18 cm (C)

LaminatedGypsum,7 cm (B)

Mudstone,12 cm (A)

419.3

oO°cO

<s.

GrayDolomiticMudstone,53 cm (A)

WavyBeddedGypsum13 cm (C)

LaminatedGypsum,46 cm(B)

LaminatedMudstone,deformed15 cm (A)

Note: Sub-bottom depths (SBD) obtained by plottingindividual sections from top of each cored interval.Letters in parenthesis, e.g. (A), indicate the memberwithin the ideal cycle.

LaminatedMudstone,deformed, 13 cm (A)

Wavy Bedded toNodular Gypsum (C),with a few thinintervals of laminatedgypsum (B)117 cm

421.3m

Figure 10. Gypsum-mudstone cycles recovered at Site 374 (SBD refers to sub-bottom depths).

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oOO

Figure 11. Photographs of laminated gypsum from Site 376 and from the Lapatza Formation, Cyprus (crossed nicols, scale bars: 500 µm). (A) Laminatedgypsum from the Lapatza Formation; elongated gypsum crystals were apparently reworked and redeposited by currents; many crystals are twinned and haveirregular grain boundaries as a result of diagnetic overgrowth. (B) Laminated gypsum from Site 376; somewhat like (A), but finer grained and containingfewer elongated crystals (376-20-1, 71-74*cm). (C) Laminated gypsum from Site 376; alternations of coarse- and fine-grained gypsum. Here a coarse layermade up of small euhedral selenite crystals was partly reworked so that the crystals now lie with their long axes more or less parallel to bedding, instead ofthe upright position characteristic of in situ growth (376-20-1, 61-64 cm).

Xoroon•nZσ

R. B. KIDD ET AL.

POST-MESSINIAN SEDIMENTS

As was the case with Leg 13, most of the Pliocene-Quaternary sections drilled during Leg 42A were"spot-cored." Again, only one post-Messinian se-quence was continuously cored. The 55 meters ofnannofossil marls with interbedded tephra and sapro-pel horizons at Site 376 now complement the 182-meter western Mediterranean section drilled at Site132. From comparison of these, together with the"spot-cores" from other sites, we conclude that wenow have representative sampling of most of sedimenttypes present in the post-Messinian deep-sea sections.


The post-Messinian sediments are nannofossil marlto marlstone which sometimes contain a greater terrig-enous content (calcareous muds) and are sometimesmore pure carbonates (tending towards calcareousoozes). Graded (and non-graded) sandy and silty bedsand laminae, volcanic tephra horizons, and sapropellayers are intercalated in these sediments.

Most of the sediments contain a moderate to highpercentage of calcium carbonate. The majority of thecalcite present is of organic origin derived from fora-minifers and coccoliths. Aragonite is generally rare,except within the turbiditic sequences at Site 374 wherearagonite, together with magnesium calcite, was prob-ably derived from shelf areas (Müller et al., thisvolume). In general, the dolomite content is low and,where it occurs, is probably of continental origin.

Sediments range in color from almost black, wheresapropel layers are intercalated, to shades of blue-grayto olive-gray. Bright beige to brown and reddish-colored intervals are intercalated in, or even dominate,the Quaternary sediments. These reddish hues indicatea high state of oxygenation of the sediment, and at theother extreme, the grayish and black colors suggest aless intense to total absence of oxygen, respectively(Sigl et al., this volume).

Bioturbation is common and has destroyed most ofthe primary sedimentary features, including stratifica-tion.

Turbidites

Intercalations of sand and coarse silt within theabove sediments have mineralogical and faunal com-positions which identify them as material displacedfrom shallower water areas. Most of the beds aregraded and can be linked to Bouma cycles (Bouma,1962) and are thus interpreted as turbidites. On theother hand, a significant number, especially at Site 371,which is on a basement knoll, are cross-laminated butnot graded. These are interpreted as turbiditic-typematerial which has been redeposited by bottom cur-rents linked to deep water circulation.

Turbiditic sequences are confined to the Quaternarypart of the central Ionian Sea sequence (Site 374). Theunderlying reason for this is variously interpreted as:

1) the expression of the geologically recent upliftof the Sicilian and Calabrian landmasses (K. J. Hsü,

personal communication); see later section for aninterpretation that would explain the observed claymineral assemblages.

2) the result of a significant steepening of theslopes of the basins since the beginning of the Quater-nary (Müller et al., this volume, who link the coarseturbidite material to a source on the African Shelf)-

3) an indication that only after the Pliocene werethe marginal basins sufficiently filled to allow bypass ofland-derived sediments into the central areas of themajor basins (Cita et al., this volume, who examinedthe geodynamic significance of Neogene sedimentationrates as determined by drilling on both Legs 13 and42A).

Pliocene-Pleistocene DiscontinuitiesLithologic evidence of local and minor stratigraphic

gaps was frequently found in the Pliocene-Quaternarysequences in the form of erosional surfaces, "hard-grounds" and omission surfaces. These reduced strati-graphic sections, which often include horizons withiron- and manganese-rich crusts and/or winnoweddebris, substantially lower the calculated sedimentationrates (Figure 12). Some, but not all, can be demon-strated paleontologically as hiatuses in deposition.Condensed sequences were identified at Site 373,where four of the six Pliocene foraminiferal zonesoccurred in a 1-meter interval; at Site 372 where thePliocene sequence is again condensed near its base;and at the continuously cored Site 376, where both theQuaternary and Pliocene are highly condensed. Thelocation of these reduced sections on topographic risessuggests that they resulted from the impingement ofcirculating water masses against upstanding features.


The post-Messinian sequences drilled during Leg42A are stikingly similar in lithology to open marinedeep basinal sections drilled elsewhere by GlomarChallenger. They are hemipelagic and frequently tur-biditic, as is the case for sediments cored in the modernMediterranean basins. Support for the view that thewhole Pliocene-Quaternary sequence was deposited inbasins comparable to those of the present day comesfrom analyses of water depths at which the openmarine benthic foraminifers and ostracodes lived. BothWright (this volume) and Benson (this volume) con-clude that sediments above the Miocene-Pliocene con-tact were deposited in water depths of at least 1000 to1500 meters. They note however that below 1500meters faunal differences can rarely be distinguished.On the other hand, seismic evidence (Biju-Duval et al.,this volume) and sedimentological studies on landsections (Fabricius et al., this volume) demonstrateconsiderable Pliocene-Quaternary subsidence, and thiswould be compatible with present depths in thesebasins, often in excess of 3000 meters. Because of thefragmentary record of the drilled Pliocene-Quaternarysediments, we suggest that further sedimentologicresearch be tied closely to studies on gravity and pistoncored material. The lithology of the Mediterranean

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Figure 12. Early Pliocene pelagic ooze with omis-sion surfaces (arrowed) from the Antalya Basin(Site 376, Section 5-5). Three biozones (MPL-2to MPL-4) spanning approximately 2 m.y.arerepresented in 1.5 meters of core. Sedimentationrates are thus as low as 0.1 cm/1000 yr.

sequences is more influenced by the recent geologicalhistory and climate of this inland sea than is thelithology of open ocean sequences. Consequently, theeffects of small-scale events should be more easilyidentifiable. We suggest that (1) a more accuratepicture of the small-scale geodynamic evolution of theMediterranean would emerge through further compari-son between the lithostratigraphy of cored and drilledsequences, (2) detailed studies of heavy and claymineral assemblages to identify sources, (3) increasedanalysis of the effects on Mediterranean sedimentdistribution of its water mass exchanges, and (4)investigations of intercalated sapropel and tephralayers (see below).

CLAY MINERALOGY

We made a concerted effort during Leg 42A toextensively sample for clay mineral analyses. Initiallythis was done to provide more detailed lithologicinterpretations, and ultimately produced considerableresults (see Mélières et al., Chamley et al , Chamleyand Giroud d'Argoud, all this volume) and the follow-ing represents an overview.

Balearic Basin

At Site 372 the clay mineralogy is dominated, fromthe lower Burdigalian (bottom of the hole) upwards bythe association of illite with chlorite; the relativeproportions of these minerals is constant throughoutthe penetrated section. This suggests their probableorigin in the Alpine orogenic belt. Poorly crystallizedsmectite appears in the uppermost Burdigalian and isinterpreted as characterizing calm sedimentary condi-tions (see below) during the Langhian and Serraval-lian. This smectite is probably derived, in part, fromillite. The clay mineralogy of the Messinian sedimentsis very similar to that of the pre-Messinian sediments,suggesting either that the former could be derived fromthe latter by reworking during the Messinian regres-sion, or that distant sources were still active during thisregression. Because the Messinian physiography isinterpreted as shallow subaqueous to subaerial, the firsthypothesis appears more probable. The Pliocene-Quat-ernary sediments are characteristically devoid of smec-tite, which suggests either a change in the nature of theterrigenous sources, or more likely, the existence ofrather active water circulation in the basin, whichprohibited the finest particles (the smectites) fromsettling out. The total lack of smectite in the Pliocene-Quaternary sediments at Site 371 seems to support thisconclusion. At both Balearic Basin sites no trace ofattapulgite was found.

At Site 371, kaolinite constitutes 20% of the claymineral assemblage in the Pliocene-Quaternary sedi-ments, whereas at Site 372 this mineral appears only astraces. This reflects the North African contribution tothe sediments in the southern part of the Balearic Basinsince kaolinite is preferentially generated in warmclimates. The inability of kaolinite to reach the central

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R. B. KIDD ET AL.

part of the basin in significant amounts seems toconfirm the suggestion above of rather active watercirculation during the Pliocene-Quaternary.

Ionian Basin

The clay mineralogy of the sediments drilled in thecentral part of the Ionian Basin is partly influenced,during the Pliocene, by attapulgite which is derivedfrom the North African platform (Chamley, 1971).This influence is not apparent (a) in the upper Messin-ian sediments, suggesting that the North African atta-pulgite was unable to reach the site because of thephysiography of the basin at this time, and (b) in theQuaternary sediments because the uplifted northernlandmasses of Sicily and Calabria began to supplyconsiderable amounts of terrigenous material devoid ofattapulgite during Quaternary time.

Levantine Basin

At Sites 375 and 376 (about 40 km west of Cyprus)the clay mineralogy is strongly dominated by smectite.These are thought to be derived from the ophiolites ofsouthern Turkey rather than from those of Cyprus, onthe basis of paleocurrent evidence (Weiler, 1963) andthe fact that the Troodos ophiolites are associated witha Neogene pelagic limestone sequence (Robertson andHudson, 1974). The prominence of smectite is sus-tained throughout the sedimentary column (Burdiga-lian to present), with an acme during the upperMessinian. This indicates that the clay mineral assem-blage is mostly derived from continental sources. Theconsiderable amount of smectite in the upper Messin-ian suggests that this mineral possibly developed partlyin the poorly drained soils of the Messinian landscape.

The above comparison between the three Mediterra-nean basins shows the primary influence of terrigenoussources on the clay mineralogy of the sediments.

At Sites 374 and 376, the mineralogy of the upperMessinian sediments is characterized by a higher chlo-rite content than is present elsewhere in the sedimen-tary sequences. From this we propose that the genesisof this magnesium-rich mineral may be the result of itsdevelopment, or at least its aggradation, in the magne-sium-rich environments of the Messinian (Chamley etal., this volume). The occurrence of attapulgite associ-ated with chlorite in the upper Messinian at Site 376seems to support this hypothesis, especially because theattapulgite, also a magnesium-rich mineral, occurs inlong and well-crystallized fibers. This suggestion, wethink, warrants further investigation, as does extendedresearch on other drilled sequences and on Neogeneand Quaternary land sections throughout the Mediter-ranean to identify sources from clay mineralogy.

SAPROPEL LAYERS

Prior to Leg 42A drilling, large numbers of discretedark colored layers of organic carbon-rich sedimenthad been identified in Quaternary eastern Mediterra-nean piston cores (Ryan, 1972; McCoy, 1974). Thesewere correlatable and were thought to be the sedimen-tary expression of periods of bottom water stagnationlinked to glacial phenomena. Leg 13 drilling pene-

trated some of these Pleistocene sapropel layers, butalso recovered one of late Pliocene age. Leg 42Arecovered over 150 separate layers and proved theirexistence dating back to the middle Miocene (Kidd etal., this volume).

On the basis of a definition which recognizes asapropel as a "discrete layer, greater than 1 cm inthickness, set in open marine pelagic sediment andcontaining greater than 2.0% organic carbon" (Kidd,et al., this volume), about two-thirds of the layers inthe Leg 42A cores were true sapropels, while theremainder were "sapropelic layers" (0.5% to 2.0%organic carbon). Detailed studies of individual layers(Sigl et al., this volume) reveal that organic carboncontents can reach 16% (Section 374-5-3), that theirintensity of color is primarily the result of monosulfideformation, which is itself linked to the percentage offinely dispersed organic matter, and that total carbon-ate content varies widely from nearly zero to 78%.

The extension of the record of Mediterranean sapro-pel stratigraphy back to the middle Miocene and, whilerecognizing the incompleteness of our drilling record inboth space and time, the development of tentativecorrelations back to the early Pliocene (Kidd et al., thisvolume) lead us to conclude that these stagnationevents cannot merely be linked to Pleistocene glacialphenomena. On the other hand, their apparent wide-spread distribution and wide range of depths involved,argue against the presence of an oxygen-minimumlayer (Arthur, 1976). Intermittent stagnation, resultingfrom stratification of the water column, appears tohave been caused by a number of interacting environ-mental factors. During the Pleistocene, the most signif-icant factors were indeed the glacial expansions butsimilar prime factors are as yet unidentified for thePliocene and middle Miocene epochs.

The scope for further research on the sapropelsrecovered through drilling is considerable. Most impor-tant would be studies aimed at their correlation, asmany of the large number of individual layers have notso far been sampled for detailed faunal and mineralog-ical analysis. Other studies aimed at identification ofthe environmental parameters that may have broughtabout the pre-Pleistocene stagnations are needed. Inparticular, substantially more information in isotopic,organic, and trace element geochemistry is desirable.

TEPHRA LAYERS

A number of volcanic ash (tephra) layers wereencountered during the Leg 42A drilling. Their inci-dence was surprisingly low in view of the large num-bers of tephra layers recognized from coring Quater-nary sediments. This is, of course, partly a result of theintermittent coring of the post-Messinian sequence.Tephra layers were naturally well represented in thePliocene-Pleistocene sediments at Site 373, which wasdrilled on a Tyrrhenian volcanic seamount. They werealso present in the Pleistocene at Site 376 and of Site378. To date no detailed petrological or geochemicalinvestigations of their volcanic glass or other mineralshave been attempted to link these to the tephra chro-nology established for sediment cores. Thus links to

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terrestrial volcanic activity are impossible at present.One layer at Site 376 does however appear correctableto a tephra at Site 125 (DSDP Leg 13) (Kidd et al.,this volume).

One problem which merits further study in DSDPmaterials is that of clay mineral diagenesis from vol-canic material. In spite of thorough investigation of theLeg 42A sequences, Chamley and Giroud d'Argoud(this volume) were unable to find any evidence oftransformation of volcanic glass into clay minerals.This is important because transformation of volcanicglass into smectites in subaqueous environments is stillwidely held to have occurred, despite the finding ofcompletely unweathered volcanic glass up to 3.8 m.y.old in sediments of the north-east Pacific (Scheidegger,1973) and experimental evidence on the solubility ofvolcanic glass reported in Heath (1974).

VOLCANIC BRECCIAS

Coring at Hole 373A penetrated the flank of aseamount in the Tyrrhenian Basin. The upper part ofthe basaltic sequence cored there included carbonate-cemented basaltic breccias with a complex history. Adetailed analysis of these breccias (Bernoulli et al., thisvolume) identifies the interclast carbonates as being ofthree types: pelagic limestones, diagenetic limestones,and void-filling sparry calcite cement. Each of thesecomponents is represented by two or more differentgenerations. The pelagic limestones are interpreted assediments that filtered down into interclast crevicesfrom the sea floor.

The diagenetic limestones apparently originatedthrough precipitation of small calcium carbonate crys-tals within the breccia, followed by current-inducedredeposition, most prominently within late-stage openfractures. Stable isotope compositions indicate that thecementation of these breccias and limestones occurredat low temperatures (6°C to 8°C) which would becharacteristic of the deep sea floor. This shows thatwater depths above this volcanic seamount were al-ready considerable in early Pliocene time.

SUMMARY

The pre-evaporitic sediments drilled at Sites 372,375, and 377 are typically basinal, pelagic to hemipe-lagic and turbiditic sediments, although today theyoccur in different tectonic settings: along a rifted anddown-faulted margin which began subsiding in theOligocene or early Miocene (Menorca Rise, Site 372);or in young compressional belts (the Florence Rise,Site 375, and the Mediterranean Ridge, Site 377).Faunal analyses also show that at Sites 375 and 372water depths prior to the Messinian evaporite deposi-tion exceeded 1000 to 1500 meters6. The sediments

deposited during the pre-Messinian Miocene at thesites are also similar in facies to the correspondingPleistocene to Recent deposits. Again, for the post-Messinian sediments, faunal analyses require the exis-tence of water depths in excess of 1000 to 1500 meterseven in the early Pliocene, and data from seismicprofiling and information derived from land sectionsgive evidence of further deepening through the Plio-cene-Quaternary, to the present-day depths.

Equilibrium conditions of deposition in these basins,both prior to and after the Messinian event, must havebeen roughly the same as at the present day. Periods ofnear-oceanic conditions when almost pure biogenicoozes were deposited occurred only after the earlyPliocene flooding of the Mediterranean Basins (Cita etal., this volume) and, to a minor extent, following theLanghian transgression in the eastern Mediterranean(Panagra Marls, Cyprus, and Site 375, lithologic Unit10).

The drilled Messinian evaporite sequences, whichare interpreted as having developed in shallowsubaqueous and subaerial environments, are conse-quently sandwiched between deep water marine sedi-mentary series. A slightly different succession wasdeveloped in the Ionian and Antalya basins where the"Lago Mare" environment was in existence in thelatest Messinian. Here the dolomitic sediments depos-ited in this oligohaline body of water are in apparentsedimentological continuity with the open marine sedi-ments of the Pliocene above. The faunal evidence, onthe other hand, is again of a vital change in ecologicalconditions at the Miocene/Pliocene contact.

We conclude, on the basis of sedimentological andenvironmental analyses, that the Mediterranean salin-ity crisis affected a series of individual basins whichvaried in their pre- and post-Messinian evolution.Some of these basins have obviously been deep sincethe early Miocene. Geophysical evidence confirms thisand shows that they have also been subsiding eversince that time (Biju-Duval et al., this volume; Ryan,1976). In some of the young compressional belts onland (Apennines, Calabria, Sicily, Crete) the evaporitesagain occur sandwiched between deep-water depositsand have been violently folded and uplifted duringsubsequent Pliocene to Recent orogenic movements.The Messinian event is recognized as having beenimposed upon deep basin topography and thus thelithologic findings of Leg 42A uphold the hypothesis(Ryan et al., 1973) of a late Miocene deep basindesiccation of the Mediterranean7. However, as notedby Hsü et al. (synthesis chapter, this volume), theoriginal concept proposed after Leg 13 must be refinedon the basis of the Leg 42A results. In addition,

6One of our number (F. Fabricius) disputes the evidence for deepbasins immediately prior to the late Miocene salinity crisis. Heemphasizes that only in the discontinuously cored Hole 375 were thedeep marine sediments below the Messinian of Tortonian age andthat the evaporites unconformably overlie Serravallian sediments atSites 372 and 377. He believes that the hiatuses could leave room forother interpretations of the tectonic history of the Mediterranean(Fabricius et al., this volume).

7F. Fabricius favors shallow environments for the Messinian butwithin basins that continually subsided and, linking his arguments toobservations on land in the Ionian Islands, he sees the Pliocene-Quaternary record as one of sedimentation in "starving basins"which sank at an average rate of 1 meter per thousand years(Fabricius et al., 1977). The other four authors consider that theweight of geophysical, geochemical, and biological evidence (Hsü etal., 1977) is overwhelmingly in support of their conclusion that deepbasins existed immediately prior to the salinity crisis.

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because of the numerous implications that this inter-pretation of the genesis of the Mediterranean evaporiteformation has for analogs present elsewhere in thegeologic record, we stress, throughout this contribution,areas where further research is of utmost importance.

ACKNOWLEDGMENTSWe thank Dr. Steve Calvert of I.O.S. for his critical review

of the manuscript and Dr. Roger Searle of I.O.S. and Dr.Charlotte Schreiber of Columbia University for their usefuldiscussions during its preparation.

REFERENCESArthur, M. A., 1976. The oxygen minimum: expansion,

intensification and relation to climate Abstract: JointInternational Oceanographic Assembly, Edinburgh, Scot-land, September 1976.

Bernoulli, D., 1972. North Atlantic and MediterraneanMesozoic facies, a comparison. In Hollister, C. D., Ewing,J. I., et al., Initial Reports of the Deep Sea DrillingProject, Volume 11: Washington (U. S. GovernmentPrinting Office), p. 801-871.

Biju-Duval, B., Letouzey, J., Montadert, L., Courrier, P.,Mugniot, J. F., and Sancho, J., 1974. Geology of theMediterranean Sea basins. In Burk, C. A. and Drake, C.L. (Eds.), The geology of continental margins: New York(Springer-Verlag), p. 695-721.

Bouma, A. H., 1962. Sedimentology of some flysch deposits:Amsterdam (Elsevier).

Chamley, H., 1971. Réchèrches sur la sedimentation argil-euse en Méditerranée: Sci. Géol. Strasbourg, Mem. 35.

Cook, H. E., Jenkyns, H. C, and Kelts, K. R., 1976.Redeposited sediments along the Line Islands, equatorialPacific. In Schlanger, S. O., Jackson, E. D., et al., InitialReports of the Deep Sea Drilling Project, Volume 33:Washington (U. S. Government Printing Office), p. 837-847.

Dean, W. E., Davies, G. R., and Anderson, R. Y., 1975.Sedimentological significance of nodular and laminatedanhydrite: Geology, v. 3, p. 367-372.

Drooger, C. W. (Ed.), 1973. Messinian events in the Mediter-ranean: Koninkl. Nederl. Akad. Wetensch., Amsterdam.

Garrison, R. E., Schreiber, B. C, Bernouilli, D., Fabricius, F.,Kidd, R. B., and Mélières, F., 1977. Sedimentary petrol-ogy and structures of Messinian Evaporites in the Mediter-ranean Sea, Leg 42A Deep Sea Drilling Project: thisvolume.

Heath, G. R., 1974. Dissolved silica and deep-sea sediments.In Hay, W. W. (Ed.), Studies in paleo-oceanography:Spec. Publ. Soc. Econ. Paleon-Miner. Tulsa, v. 20, p. 77-93.

Hesse, R., 1975. Turbiditic and non-turbiditic mudstones ofCretaceous flysch sections of the East Alps and otherbasins: Sedimentology, v. 22, p. 387-416.

Jones, J. B. and Segnit, E. R., 1971. The nature of opal. I.Nomenclature and constituent phases: J. Geol. Soc. Aus-tralia, v. 18, p. 57.

Mauffret, A., Fail, J. P., Montadert, L., Sancho, J., andWinnock, E., 1973. North-western Mediterranean sedi-mentary basin from seismic reflection profile: Am. Assoc.Petrol. Geol. Bull., v. 57, p. 2245-2262.

McCoy, F. W., Jr., 1974. Late Quaternary sedimentation inthe eastern Mediterranean Sea: Unpublished Ph.D. thesis,Harvard University, p. 149-170.

McKenzie, J., Bernoulli, D., and Garrison, R. E., 1977.Lithification of pelagic-hemipelagic sediments at Site 372:oxygen isotope alteration with diagenesis: this volume.

Montenat, C, Bizon, G., and Bizon, J. J., 1975. Rémarquessur le Néogène du forage JOIDES 121 en mer d'Alboran(Méditerranée occidentale): Soc. Geol. France Bull., v. 17,p. 45-51.

Robertson, A. H. F. and Hudson, J. D., 1974. Pelagicsediments in the Cretaceous and Tertiary history of theTroodos Massif, Cyprus. In Hsü, K. J., Jenkyns, H. C.(Eds.), Pelagic sediments: on land and under the sea:Spec. Publ. Int. Assoc. Sediment., v. 1, p. 403-436.

Ryan, W. B. F., 1972. Stratigraphy of late Quaternarysediments in the Eastern Mediterranean. In Stanley, D. J.(Ed.), The Mediterranean Sea: Strasbourg, Virginia(Dowder, Hutchinson and Ross).

, 1976. Quantitative evaluation of the depth ofthe western Mediterranean before, during and after thelate Miocene Salinity Crisis: Sedimentology, v. 23, no. 6.

Ryan, W. B. F., Hsü, K. J., et al., 1973. Initial Reports of theDeep Sea Drilling Project, Volume 13: Washington (U. S.Government Printing Office).

Scheidegger, K. F., 1973. Volcanic ash layers in deep-seasediments and their petrolpgical significance: EarthPlanet. Sci. Lett., v. 17, p. 397-407.

Schreiber, B. C, 1974. Upper Miocene (Messinian) evaporitedeposits of the Mediterranean and their depositionalenvironments: Ph.D. Thesis, Rensselaer Polytechnic Insti-tute.

Schreiber, B. C. and Friedman, G. M., 1976. Depositionalenvironments of Upper Miocene (Messinian) evaporites ofSicily as determined from analysis of intercalated carbon-ates: Sedimentology, v. 23, p. 729-760.

Von der Haar, S., 1976. Gypsum in sediments. In Fairbridge,R. W. (Ed.), Encyclopedia of sedimentology: New York(Reinhold Publishing Co.).

Weiler, Y., 1963. Some remarks on the Kythrea Flysch: Ann.Rept. Geol. Survey Cyprus, p. 53-56.

, 1970. Mode of occurrence of pelites in theKythrea Flysch Basin (Cyprus): J. Sediment Petrol, v. 40,p. 1255-1261.

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56. LITHOLOGIC FINDINGS OF DSDP LEG 42A, …