THE BLAKE-BAHAMA BASIN1

26. DINOFLAGELLATE AGE OF MIDDLE JURASSIC-EARLY CRETACEOUS SEDIMENTS INTHE BLAKE-BAHAMA BASIN1

Daniel Habib, Queens College of the City University of New York, Flushing, New Yorkand

Warren S. Drugg, Chevron Oil Field Research Company, LaHabra, California

ABSTRACT

Biostratigraphic datums of stratigraphically useful dinoflagellates are used to date the Jurassic-Cretaceous sequencein Hole 534A drilled by the Deep Sea Drilling Project. The investigated interval is dated middle Callovian through Vra-conian Albian in the 875-m-thick section represented by Cores 534A-127 to 534A-27. Dinoflagellates date the new, low-ermost, unnamed lithostratigraphic unit at Hole 534A as middle Callovian through Oxfordian, with basal Kimmeridgi-an sediments occurring in the approximate position of the boundary with the overlying Cat Gap Formation. The zonedCretaceous interval in Holes 534A and 391C in the Blake-Bahama Basin ranges from the late Berriasian through theVraconian.

A zonation is proposed for the stratotype and parastratotype sections of sediments deposited in the EuropeanTethys during the Neocomian (early Berriasian-late Hauterivian). It shows the same chronostratigraphic succession ofspecies common to the Tethys of both North Atlantic and Europe. On the basis of scanning electron micrographevidence, the epicystal tabulation of Druggidium apicopaucicum Habib is revised.

INTRODUCTION

The dinoflagellate stratigraphy of Hole 534A, drilledby the Deep Sea Drilling Project in the Blake-BahamaBasin, was studied in order to date the palyniferous Me-sozoic section. Site 534 is located near the center of theBlake-Bahama Basin, at 28°20.6'N, 75°22.9'W, 22 kmnortheast of Hole 391C (Benson, Sheridan et al., 1978)(Fig. 1). Drilling Hole 534A recovered a subseafloor sec-tion approximately 1667 m thick. The palynologicallyinvestigated interval is situated in the lower part of thesedimentary section. It is 875 m thick, and ranges fromthe stratigraphic level of Core 534A-27 at 764.5 m sub-bottom depth to that of Core 534A-127 at 1639.5 m. Thelowest part is basalt, from Cores 534A-127 (core catchersample) to 534A-130 at 1666.5 m. On the basis of thedinoflagellate evidence, the sedimentary section is datedas middle Callovian near the contact with the underlyingbasalt (Sample 534A-127-2, 33-35 cm) to Vraconian Al-bian at the top of the black clay sequence (534A-27-1,66-68 cm).

The lithostratigraphy is summarized from the com-prehensive description given in the Site 534 report (thisvolume). Habib (this volume) interprets the origin of theparticulate organic matter. Examination of the color ofpalynomorphs suggests that the organic matter near thebase of the section is thermally immature.

Four lithostratigraphic units were identified (Fig. 2).In descending stratigraphic order, these are the HatterasFormation, Blake-Bahama Formation, Cat Gap Forma-tion, and a lowermost, unnamed lithostratigraphic unitthat rests directly on the basalt.

Sheridan, R. E., Gradstein, F. M., et al., Init. Repts. DSDP, 76: Washington (U.S.Govt. Printing Office).

Figure 1. Location of Deep Sea Drilling Project Holes 534A and391C in the Blake-Bahama Basin and other sites referred to in thetext.

The Hatteras Formation is approximately 200 m thickand spans the interval from Core 534A-27 through Core534A-48. Four major lithologies are evident; these con-sist of an uppermost interbedded black-green noncal-careous clay lithology in Cores 534A-27 to 534A-30; acarbonaceous and lesser interbedded green claystone li-thology (534A-31 to 534A-39); yellowish, brownish, andreddish noncalcareous clays (534A-40 to 534A-42); and

623

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a lowermost transitional lithology of interbedded car-bonaceous clay and calcareous nannofossil claystones(534A-43 to 534A-48). The type locality of the HatterasFormation is at Site 105 (Fig. 1) in the western North At-lantic. The boundary between the Hatteras Formationand the underlying Blake-Bahama Formation is placedbetween Cores 534A-48 and 534A-49 in this chapter,

based on the uppermost occurrence, in Core 534A-49,of massive, graded bedding in the majority of the cal-careous claystones. The last appearance datum of Pho-berocysta neocomica (Gocht) in Core 534A-49 corre-lates the top of the Blake-Bahama Formation with itstop in Core 391C-14 from Hole 391C, located 22 km tothe southwest.

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The Blake-Bahama Formation has its type locality atHole 391C (Jansa, et al., 1979). In Hole 534A, it is 383m thick and consists of predominantly calcareous lithol-ogies ranging from the stratigraphic level of Core 534A-49 to within Core 534A-92. The upper part compriseslimestones with interbedded quartzose and calcareousturbiditic siltstones and sandstones in the stratigraphicinterval of Cores 534A-49 to 534A-64. The lower part of

the formation, from Cores 534A-65 to 534A-92, consistsof finely laminated nannofossil chalks and marls, bio-turbated chalks, and minor graded claystones, changingdownward to similar but somewhat more heterogeneouslithologies that are distinguished by burrowed lime-stones rather than chalks. The lowest part of the forma-tion is more uniform, and lacks the laminated characterof the lithologies above. It is typically burrowed and

625


contains stylolites. Reddish calcilutite laminae occur inCores 534A-84 and 534A-90.

The Cat Gap Formation occurs in the stratigraphicinterval from Core 534A-92 to within Core 534A-111(Site 534 report, this volume). It is 153 m thick. Twomajor lithologies occur. The upper, in Cores 534A-92 to534A-103, consists primarily of hematitic pale reddishcalcareous claystones that darken in color downward.The lower lithology is composed of greenish gray calcar-eous claystones and darker gray limestone turbidites.Jansa et al., (1979) designated the type locality of theCat Gap Formation at Site 105 in the western North At-lantic (Fig. 1).

The lowermost lithostratigraphic unit is 140 m thickand extends from Core 534A-111 to the base of the sedi-mentary section. It is the oldest unit thus far recoveredfrom the western North Atlantic. The uppermost lithol-ogy (Cores 534A-111 to 534A-117) consists of dark var-iegated claystones that are pale red to blackish red,greenish gray, olive black, and dark gray. The next low-er lithology, in Core 534A-117 to the top of Core 534A-120, is distinguished by gray limestones interbeddedwith variegated claystones. In the interval of Cores 534A-120 to 534A-125, the lithology consists of dark green ra-diolarian claystones and greenish gray limestones. Thelowermost lithology consist of greenish black calcareousnannofossil claystones and reddish brown nannofossilclaystones.

DINOFLAGELLATE STRATIGRAPHY

Distribution of PalynomorphsTable 1 lists the 151 samples that were studied. The

vast majority of these samples contain stratigraphicallyuseful dinoflagellate cysts, although their relative abun-dance varies in the various organic facies. Even in theless productive samples, a workable number of specieswas available from relatively few specimens. Seventeensamples are barren of palynomorphs, or contain speci-mens that are too poorly preserved for study. Thesesamples were taken from the Oxfordian, Kimmeridgian,and Albian black clay lithologies containing carbonizeddebris of the micrinitic facies; Tithonian and Berriasianred calcareous clay and calcareous nannofossil ooze li-thologies containing the micrinitic or poorly preservedxenomorphic facies; and Aptian red, yellow, or brownnoncalcareous clays containing the micrinitic facies (Ha-bib, this volume). The absence or poor preservation ofpalynomorphs in these samples is attributed to the relat-ed effects of sedimentation rate and diagenetic oxygendepletion.

Episodes of rapid supply of terrigenous organic mat-ter (pollen grains, larger fern spores, tracheal tissue, cel-lular cuticle) admixed with dinoflagellates and amor-phous (xenomorphic) debris occur in the middle Callo-vian and in intervals within Valanginian to early Albiansediments. Kimmeridgian black clay containing appreci-able carbonized trachael tissue is considered to representterrigenous organic matter that was oxidized in the bur-ied sediment environment. Each of these terrigenousevents is followed directly by an interval of abundant

Table 1. List of samples, Deep Sea Drilling Project,Hole 534A.

Sample Sample Sample(core-section, (core-section, (core-section,

interval in cm) interval in cm) interval in cm)

27-1,27-2,27-3,28-2,29-1,30-1,32-1.33-2,34-3,35-1,36-1,36-1,36-1,36-1,36-2,36-3,37-1,37-3,38-5,39-1,39-4,39-6,41-1,41-2,41-3,41-6,42-1,42-2,42-3,43-1,44-3,

, 66-68, 66-68, 66-68, 20-22, 14-16, 15-17, 21-24, 10-1222-24108-11020-2259-6162-6488-9088-90a

88-9025-2725-274-626-38a

46-480-242-44a

42-44a

42^t4a

42-4415-17a

15-17a

15-1792-9494-96

45-2, 34-3645-4,45-5',46-1,47-1,47-4,48-2,48-6,49-3,49-4,49-7,50-1,50-2,50-5,51-1,52-3,53-3,54-2,55-3,56-1,

78-806-868-7066-682-419-2119-2130-3230-3230-3250-5250-5250-5230-322-4128-13041-4311-1334-36

58-4, 59-6159-2, 30-3260-3, 76-7861-2, 73-7562-1, 41-4263-2, 38-4064-1, 70-7265-5, 40-4266-5, 81-8267-1, 131-13368-1, 39-4169-1, 50-5270-6, 30-3271-1, 29-3172-2, 34-3673-1, 125-12774-6, 54-5675-1, 43-4476-3, 10-1277-2, 43-4578-1, 104-10679-2, 55-5780-2, 27-2881-1, 61-6282-1, 53-5583-4, 90-91a

84-7, 0-285-5, 48-4986-1, 148-15087-6, 7-888-2, 107-10889-1, 81-8290-1, 24-2590-3, 52-5390-4, 30-3190-5, 49-5090-2, 0-190-4, 30-3191-1, 103-104a

91-2, 57-5891-3, 40-4191-4, 107-10892-2, 9-10a

93-2, 99-10094-4, 68-70a

95-4, 46-4796-2, 35-3699-3, 79-80100-2, 127-128101-4, 71-73

102-4, 68-70102-5, 78-80103-1, 95-96103,CCa

104-2, 59-61104,CCa

105-1, 17-18105-1, 95-98105-1, 110-111105-1, 126-127105-2, 53-54105-2, 92-94106-1, 3-4107-2, 98-100108-1, 23-25a

109,CCa

110,CCa

111-1,27-29112-1,69-71112-1, 108-110113-1, 0-2114-1, 22-24115-1, 73-74a

116-1,44-46116-1,76-78117-1, 9-10a

118-1, 5-7118-1, 100-102119-1, 120-121120-1, 31-33120-1, 43-45121-1, 8-10121-1, 46-48122-2, 68-70123-1, 90-92123-1, 94-94124-1, 8-10124-1, 54-56125-1, 13-14125-1, 64-66125-3, 144-146125-3, 146-147125-5, 88-89125-6, 91-92126-2, 63-65126-1, 74-77126-2, 23-26126-3, 74-75126-4, 93-95127-2, 33-35

a Sample is barren of palynomorphs.

xenomorphic debris associated with diversified dino-flagellates and pollen in the genus Classopollis.

Episodes containing relatively few palynomorphs thatconsist mainly of dinoflagellates occur through most ofthe Late Jurassic, and within the Hauterivian, Barremi-an, Aptian, and middle Albian to Vraconian. Pollengrains are very poorly represented in the Late Jurassicand are composed almost entirely of Classopollis, Exesi-pollenites, and bisaccate grains. These pollen genera arebetter represented in the Early Cretaceous intervals.

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Biostratigraphic Dating

Figure 2 shows the dinoflagellate stratigraphy pre-pared for Hole 534A. The stratigraphy is dated by cor-relation with the ammonite-zoned dinoflagellate stratig-raphy of corresponding European stratotype sectionsappearing in unpublished reports prepared by W. S.Drugg, and with the summary range chart of ammonite-dated dinoflagellates published by Raynaud (1978) forthe Jurassic. The Jurassic-Neocomian dinoflagellatestratigraphy at Site 534 (and elsewhere in the westernNorth Atlantic) shows close affinities with the Tethyanprovince of mediterranean Europe, not only with re-spect to stratigraphic ranges but also with the relativeabundance of certain fossils (e.g., Druggidium, Come-todinium). Bernoulli (1972) showed a comparable rela-tionship between the facies of the western North Atlan-tic and the European Tethys. Accordingly, the Tethyandefinition of the Kimmeridgian Stage is used, where theKimmeridgian/Tithonian boundary is placed at the baseof the Gravesia elegans ammonite zone.

The interval from middle Callovian (Core 534A-127)through early Berriasian (Core 534A-87) is dated on thebasis of the first appearance (FAD) and last appearance(LAD) datums of stratigraphically useful dinoflagellates.Study of additional sections of corresponding age in theNorth Atlantic may show that these fossils are useful fordefining biostratigraphic zones. The late Berriasian (Core534A-86) through Vraconian (534A-27) interval is datedon the basis of the North Atlantic zonation published byHabib (1977). The same zonal sequence occurring atother sites in the western North Atlantic is present atSite 534, except that the uppermost (early Cenomanian)part of the Spinidinium echinoideum Zone and the en-tire middle to late Cenomanian Trithyrodinium suspec-tum Zone were not found. The zonation of Hole 534Acorrelates precisely with that of Hole 391C (Habib,1978). At both sites in the Blake-Bahama Basin, the zo-nation ranges from late Berriasian to Vraconian.

All the zonal species in the Cretaceous zonation areillustrated by Habib (1976; 1978) and by Sverdlove andHabib (1974). The Deßandrea vestita and Deflandreaechinoidea Zones are renamed the Spinidinium vestitumand Spinidinium echinoideum zones, respectively. TheOdontochitina operculata Zone of Habib (1977) is aban-doned; its Phoberocysta neocomica Subzone is elevatedto the rank of zone and renamed the Odontochitina op-erculata Zone, and its Subtilisphaeraperlucida Subzoneis also elevated to the rank of zone. In none of thesechanges of name or zonal rank has the definition of theoriginal zones and subzones been modified.

A zonation is proposed for the Tethyan stratotypesections of the Neocomian (early Berriasian-late Hau-terivian) stages and is compared with the North AtlanticNeocomian zonation.

Jurassic-Berriasian (middle Callovian-early Berriasian)

CallovianThe interval ranging from Samples 534A-127-2, 33-

35 cm through 534A-122-2, 68-70 cm is dated middle

Callovian to late Callovian. Stephanelytron scarburgh-ense Sarjeant, emended Stover, Sarjeant, and Drugg ispresent in the former sample, which indicates that thissample is not older than middle Callovian. Stover et al.(1977) indicated that this species ranges from middleCallovian to Kimmeridgian, based on its stratigraphy inEuropean ammonite-dated sections. The last appear-ance of Wanaea indotata Drugg in the uppermost sam-ple of this interval indicates an age not younger than lateCallovian. Other stratigraphically useful species occur-ring in this interval are Scriniodinium dictyotum Cook-son and Eisenack, Stephanelytron redcliffense Sarjeant,emended Stover, Sarjeant, and Drugg, Pareodinia evit-tii (Pocock), Hystrichogonyaulax pectinigera (Gocht),Lithodinia jurassica Eisenack, Ctenidodinium ornatum(Eisenack), C. gochtii (Sarjeant) and C. norrisii (Po-cock). The occurrence of Scriniodinium dictyotum andStephanelytron redcliffense supports an age assignmentnot older than Callovian. P. evittii was observed in thelowermost sample only. C. gochtii and a closely relatedspecies that is characterized by intratabular ridges with-in septal plate boundaries (Pocock, 1972), C. norrisii,last appear in Sample 534A-124-1, 54-56 cm, which sug-gests that this stratigraphic level is not younger thanmiddle Callovian. Gonyaulacysta jurassica (Deflandre)first appears in the uppermost sample (534A-122-2, 68-70 cm). In the European sections, this species rangesdown through the Callovian.

The schizaeaceous fern spore Cicatricosisporites isrepresented by several species in the interval dated mid-dle Callovian. This occurrence is unusual, as the earliestappearance of this genus has been used to date sedi-ments in the Late Jurassic. However, it has been re-ported from the Callovian of North Africa by Reyre(1973), and Dorhofer (1979) has suggested that it mi-grated to higher latitudes during the Late Jurassic. Theoccurrence of these spores in appreciable amounts indeep-sea sediments is related to rapidly deposited ter-rigenous organic matter (Habib, 1978) and to proximityto a shoreline in the neritic facies.

OxfordianThe interval from Sample 534A-121-1, 46-48 cm

through Sample 534A-112-1, 69-71 cm is dated Ox-fordian. Polygonifera evittii Habib (1972) (= ? Sen-oniasphaera frisia Raynaud, 1978) first appears in thelowermost sample. In the European sections, this spe-cies ranges from earliest Oxfordian into the Berriasian.In Hole 534A, the stratigraphic ranges of P. evittii andWanaea indotata do not overlap. This places the Callo-vian/Oxfordian boundary between Samples 534A-122-2,68-70 cm and 534A-121-1, 46-48 cm. The interval fromCores 534A-121 through 534A-120 lies within the earlyOxfordian. Hystrichogonyaulax pectinigera and Litho-dinia jurassica last appear in Cores 534A-121 and 534A-120, respectively, which supports the basal Oxfordianage of this interval. In Hole 534A, Stephanelytron red-cliffense last appears in the early Oxfordian, in Sample534A-121-1, 8-10 cm. Systematophora sp. cf. 5. com-plicata Neale and Sarjeant is restricted to the Oxfordianin Hole 534A. Systematophora areolata Klement first

627


appears in Sample 534A-114-1, 22-24 cm, which indi-cates that this level is not older than middle Oxfordian.

Kimmeridgian

The interval from Samples 534A-111-1, 27-29 cmthrough 534A-105-1, 17-18 cm is dated Kimmeridgian.The Oxfordian/Kimmeridgian boundary is placed be-tween Samples 534A-112-1, 69-71 cm and 534A-111-1,27-29 cm, based on the first appearance of Occisucystabalia Gitmez in the latter sample. O. balia first appearsin sediments of the earliest Kimmeridgian in the ammo-nite-dated stratigraphy in Europe. Gonyaulacysta nuci-formis (Deflandre) first appears in the approximate po-sition of this boundary, in Sample 534A-112-1, 69-71cm. According to Raynaud (1978), G. nuciformis firstappears very close to the Oxfordian/Kimmeridgianboundary in the stratotype sections. G. jurassica has itslast stratigraphically persistent appearance in Sample534A-110,CC.

Samples from Cores 108 and 109 are either barren ofpalynomorphs in oxidized black clay (Habib, this vol-ume) or contain few dinoflagellates. Dinopterygium di-morphum (Ioannides, Stavrinos, and Downie) Druggoccurs in Sample 534A-107-2, 98-100 cm and rangesdiscontinuously to near the top of the Jurassic, in Sam-ple 534A-93-2, 99-100 cm. This species becomes strati-graphically persistent in the Kimmeridgian-Tithonian.Histiophora ornata Klement, a species that was de-scribed by Klement (1960) from the Kimmeridgian ofGermany, occurs in Samples 534A-106-1, 3-4 cm and534A-105-2, 92-94 cm. Egmontodinium polyplacophor-um Gitmez and Sarjeant first appears in Sample 534A-106-1, 3-4 cm as well, which is indicative of the Kim-meridgian to Tithonian. Stephanelytron scarburghenselast appears in Sample 534A-105-2, 92-94 cm, which in-dicates an age not younger than Kimmeridgian (Stover,et al., 1977).

Another dinoflagellate that is valuable for datingsediments not older than Kimmeridgian in the North At-lantic sections is the morphotype with a pentagonal out-line, attached operculum, and perforate antapical per-icyst assigned to Sirmiodinium grossii Alberti. S. grossiiwas described from the Early Cretaceous, and is knownto range into the Callovian in the European sections.However, in the Callovian and Oxfordian, trilobateforms occur together with the pentagonal, a phenome-non that was found in Greenland (Fensome, 1979), Al-aska, and in the European stratotype sections. In Hole534A, and at Sites 100 and 105, the pentagonal morpho-type is morphologically close to Senoniasphaera juras-sica Gitmez and Sarjeant, from which it is distinguishedby its perforate pericyst. In the North Atlantic, Sir-miodinium grossii (pentagonal) is restricted to the Kim-meridgian-Tithonian. It has not been found in Creta-ceous North Atlantic sediments thus far.

TithonianThe Tithonian is identified in the interval from Sam-

ples 534A-104-2, 59-61 cm through 534A-91-3, 40-41cm. The Kimmeridgian/Tithonian boundary is placed be-tween Samples 534A-1O5-1, 17-18 cm and 534A-104-2,

59-61 cm, based on the first appearance of Cometodi-nium whitei (Deflandre and Courteville) in the lattersample. Support for the position of this boundary isdrawn from the last appearance of Stephanelytron scar-burghense in Sample 534A-105-2, 92-94 cm. C. whitei isan Early Cretaceous species that is known to occur inthe Tithonian of France. It also occurs in the Late Ju-rassic at Site 105 (Habib, 1976), Hole 99A, and Site 100in the western North Atlantic. It is a valuable guide spe-cies in the North Atlantic stratigraphy, because it is oneof the few dinoflagellate fossils that are stratigraphicallypersistent through the poorly palyniferous interval acrossthe Jurassic/Cretaceous boundary. This species has notbeen observed in any Kimmeridgian or older sample inthe stratotype sections of England and France.

A number of species do not range younger than Ti-thonian at Hole 534A. These include Dinopterygiumdimorphum, Chytroeisphaeridia chytroeides (Sarjeant),Sentusidinium verrucosum (Sarjeant), Tubotuberella ap-atela (Cookson and Eisenack), Gonyaulacysta ambigu-ua (Deflandre), G. nuciformis, and Sirmiodinium gros-sii (pentagonal). The Cretaceous species Gonyaulacystahelicoidea (Eisenack and Cookson) first appears in Sam-ple 534A-93-2, 99-101 cm, but does not become strati-graphically persistent until Sample 534A-81-1, 61-62 cm.

Early BerriasianThe early Berriasian is identified in the interval from

Samples 534A-91-2, 57-58 cm through 534A-87-6, 7-8cm. This interval, and that ranging down to the base ofthe Blake-Bahama Formation across the Jurassic/Cre-taceous boundary, is poorly palyniferous and containsonly few stratigraphically persistent dinoflagellates. Theearliest Berriasian, in the lowermost sample, 534A-91-2,57-58 cm, is distinguished by the first stratigraphicallypersistent appearance of Prolixosphaeridium sp. cf. P.granulosum, which becomes stratigraphically persistentin the stratotype stages of the Neocomian, and in theNeocomian in Hole 534A. It is morphologically closeto, and possibly conspecific with, Prolixosphaeridiumgranulosum, which occurs in sediments of the Late Ju-rassic in Hole 534A. Other species are rare and scatteredin the early Berriasian in Hole 5 34A and do not becomestratigraphically persistent until the approximate posi-tion of the lower boundary of the Biorbifera johnew-ingii Zone. These include Phoberocysta neocomica(Gocht) and Tanyosphaeridium salpinx Norvick. Pareo-dinia dasy forma Wiggins was observed in one sample(534A-88-2, 107-108 cm).

Cretaceous Zonation

Biorbifera johnewingii Zone (Habib, 1977)Of the late Berriasian, this zone is based on the first

appearance datum of Biorbifera johnewingii Habib inSample 534A-86-1, 148-150 cm and extends up to Sam-ple 534A-82-1, 53-55 cm, directly below the first ap-pearance of Druggidium apicopaucicum Habib. Otherspecies that first appear in Hole 534A include Diacan-thum hollisteri Habib, Ctenidodinium elegantulum Mil-lioud, Pseudoceratium pelliferum Gocht, Hystrichodin-

628


ium voigtii (Alberti), Wallodinium krutzschii (Alberti),Cyclonephelium distinctum Deflandre and Cookson,and Dingodinium cerviculum Cookson and Eisenack.Several of these species, for example, Diacanthum hol-listeri and C. elegantulum, first appear earlier in the lateearly Berriasian in the Berrias stratotype section. Am-phorula metaelliptica Dodekova is restricted to this zonein the western North Atlantic and in the Berrias section.

Druggidium apicopaucicum Zone (Habib, 1977)This zone is distinguished by the first appearance of

D. apicopaucicum in Sample 534A-81-1, 61-62 up toSample 534A-76-3, 10-12 cm, directly below the Phylo-genetic appearance (PAD) of Druggidium deflandrei(Millioud). The age of the zone is Valanginian; the lowerboundary is earliest Valanginian, in the approximateposition of the Berriasian/Valanginian boundary, basedon correlation with the stratotype stratigraphy. Prisma-tocystis cylindrica Habib and Cleistosphaeridium poly-pes (Cookson and Eisenack) first appear in this zone inHole 534A. The Jurassic species Systematophora fasci-culigera last appears within this zone.

Druggidium deflandrei Zone (Habib, 1977)This zone is based on the Phylogenetic appearance of

D. deflandrei in Sample 534A-75-1, 43-44 cm up toSample 534A-64-1, 70-72 cm, immediately below thePhylogenetic appearance of Druggidium rhabdoreticu-latum Habib. The zone ranges from late Valanginian toHauterivian. Scriniodinium dictyotum last appears inthe late Valanginian of the stratotype sections, which sug-gests that the Valanginian/Hauterivian boundary liesimmediately above the last appearance of this species inSample 534A-73-1, 125-127 cm. Biorbifera johnewingiiand Diacanthum hollisteri last appear in Sample 534A-75-1, 43-44 cm, which supports dating the lower bound-ary late Valanginian.

Druggidium rhabdoreticulatum Zone (Habib, 1977)This zone is identified on the basis of the phylogenet-

ic appearance of D. rhabdoreticulatum in Sample 534A-63-2, 38-40 cm up to Sample 534A-62-1, 41-42 cm, im-mediately below the first appearance of Odontochitinaoperculata (Wetzel). This zone is thin in the westernNorth Atlantic but is geographically widespread. It wasnot found in the Neocomian stratotype sections. By itsstratigraphic position between the Druggidium deflan-drei and Odontochitina operculata zones, this zone isassigned to the Hauterivian.

Odontochitina operculata Zone (new name proposedfor Phoberocysta neocomica Subzone defined byHabib, 1978)

The Phoberocysta neocomica Subzone is elevated tothe status of Zone and is renamed the Odontochitinaoperculata Zone. Its definition remains the same (Ha-bib, 1978, p. 891). However, it is restricted relative tothe definition of the original Odontochitina operculataZone of Habib (1977), which is abandoned.

The interval of this zone is recognized from the firstappearance of O. operculata in Sample 534A-61-2, 73-75

cm to the last appearance of Phoberocysta neocomica(Gocht) in Sample 534A-49-4, 30-32 cm. The zone is ofthe late Hauterivian to the early Bedoulian (early earlyAptian). DeRenéville and Raynaud (1981) used thesetwo species to identify the Barremian in its stratotypesection. Although the greater thickness of this zone inHole 534A is of the Barremian, O. operculata is knownto first appear in the late Hauterivian Subsaynella sayniammonite zone, and P. neocomica occurs in the lowerpart of the Bedoulian (early Aptian) in the La Bédoulestratotype. Also, Millioud (1969) reported P. neocomicain the lower part of the Aptian in the Barremian strato-type section at Angles.

Subtilisphaera terrula (Davey), S. perlucida (Alberti),Cribroperidinium sepimentum Neale and Sarjeant, Spi-niferites! dentatus (Gocht), Coronifera oceanica Cook-son and Eisenack, and a smooth spherical adnate spe-cies in Kallosphaeridium sp. first appear near the lowerboundary. Druggidium apicopaucicum has its last strati-graphically persistent appearance in Sample 534A-61-2,73-75 cm. This species last appears in the late Hauter-ivian at other sites in the North Atlantic (Habib, 1977,p. 351; fig. 2) and in the stratotype sections; however,three specimens were observed in Sample 534A-49-7, 30-32 cm. Because of the large gap represented by the inter-val from Cores 534A-61 to 534A-49, the occurrence ofthis species in Core 534A-49 is anomalous and is consid-ered to be due to reworking. Chlamydophorella nyeiCookson and Eisenack first appears near the upperboundary of the Odontochitina operculata Zone.

Subtilisphaera perlucida Zone (Habib, 1978)This zone was originally described as a subzone (Ha-

bib, 1978); it is elevated to the status of zone. In Hole534A, it is represented by the interval from Sample 534A-49-3, 30-32 cm, immediately above the last appearanceof Phoberocysta neocomica, to Sample 534A-36-3, 88-90cm. Named after S. perlucida, which ranges from belowand through it, the zone ranges in age from Aptian toearly Albian. The Aptian/Albian boundary is placedwithin the zone immediately above the last appearanceof Druggidium deflandrei in Sample 534A-41-6, 42-44cm. Species that first appear in the lower part (Aptian)include Cassiculosphaeridia reticulata Davey and Hy-strichosphaeridium! arundum Eisenack and Cookson.

Samples from Core 534A-39 contain numerous speci-mens of the long-ranging species Cyclonephelium dis-tinctum Deflandre and Cookson. Included in this spe-cies is a tabulated morphotype that resembles Cyclo-nephelium tabulatum Davey and Verdier.

Spinidinium vestitum Zone (new name for Deflandreavestita Zone of Habib, 1977)

This zone is represented by the first appearance ofSpinidinium vestitum Brideaux (e.g., Sverdlove and Ha-bib, 1974, plate 1, figs. 7-12) in Sample 534A-36-1, 88-90 cm, up to Sample 534A-32-1, 21-24 cm. Its age ismiddle Albian (or late early Albian) to late Albian.

The Spinidinium vestitum Zone contains the oldesttricolpate angiosperm pollen taxa recovered in the west-ern North Atlantic. In Hole 534A, Retitricolpites geor-

629


gensis Brenner, R. magnificus Habib, R. sphaeroidesPierce, and Tricolpites minutus (Brenner) first appearnear the base of this zone. Psilatricolporites sp. (Habib,1978, plate 1, fig. 8) first appears in the upper part.

The dinoflagellate species Palaeohystrichophora in-fusorioides Deflandre first appears near the base of thiszone. Subtilisphaera pontismariae (Deflandre) first ap-pears very near the top (Sample 534A-32-1, 32-34 cm).5. terrula and S. perlucida last appear within the Spini-dinium vestitum Zone.

Spinidinium echinoideum Zone (new name forDeflandrea echinoidea Zone of Habib, 1977)

This zone is represented by the Phylogenetic appear-ance of Spinidinium echinoideum (Cookson and Eise-nack) Lentin and Williams, 1976. S. echinoideum (e.g.,Sverdlove and Habib, 1974, plate 1, figs. 1-6) first ap-pears in Sample 534A-3O-1, 15-17 cm and ranges to thetop of the investigated section in Sample 534A-27-1,66-68 cm.

In the North Atlantic, the Spinidinium echinoideumZone ranges from Vraconian Albian to early Cenoma-nian. In the Blake-Bahama Basin (Holes 534A and391C), however, the top of the zone was not observed.Its age in this area is considered to lie completely withinthe Vraconian on the basis of the occurrence of two spe-cies in the uppermost sample that terminate in the Vra-conian, S. vestitum and Hystrichosphaeridiuml arun-dum. At Holes 101A and 105, S. vestitum and H.I arun-dum last appear in sediments dated by planktonic fora-minifers (Luterbacher, 1972) as Vraconian Albian.

Litosphaeridium siphoniphorum (Cookson and Ei-senack), Epelidosphaeridia spinosa (Cookson andHughes), and Wallodinium inflatum Habib first appearat or near the base of the Spinidinium echinoideumZone.

NEOCOMIAN STRATOTYPE ZONATION

Figure 3 depicts the stratigraphy and zonation of se-lected dinoflagellate taxa in Tethyan ammonite-datedNeocomian stratotype and parastratotype sections. Theinvestigated sections are located in southeastern Franceand northwestern Switzerland. The sections in southeastFrance are as follows: Broyon (Ardèche), Tithonianthrough early late Berriasian; Berrias (Ardèche), lateTithonian through early Valanginian; Lacisterne (Hér-ault), late Berriasian through early Valanginian; Gines-tous-la Garenne (Hérault), late Berriasian through ear-ly Valanginian; Ginestous-les Oliviers (Hérault), latestBerriasian through basal Valanginian; Orpierre (Hautes-Alpes), latest Berriasian through early Hauterivian; LaCharce (Dròme), late Valanginian through early lateHauterivian; Route d'Angles (Basses-Alpes), late Hau-terivian; Sisteron (Basses-Alpes), late Hauterivianthrough early Aptian. Three sections from Switzerlandwere investigated. They are as follows: Valangin, latestBerriasian through early late Hauterivian; Hauterive,Hauterivian; Le Landeron, late early Hauterivianthrough late Hauterivian. All are in the Jura Moun-tains. Detailed geographic, lithologic, and biostrati-graphic information on these sections is presented byThierstein (1973), who sampled the French and Swiss

sections for the Chevron Oil Field Research Company.The Neocomian stratotype zonation is based on thestratigraphic succession of species appearing at the baseof the zone that it defines and names.

Phoberocysta neocomica ZoneDefinition. Interval from the first appearance of

Phoberocysta neocomica to the first appearance of Bi-orbifera johnewingii.

Age. Basal Berriasian through the ammonite B. pri-vasensis Subzone of the early late Berriasian.

Remarks. Muderongia simplex Alberti is a commonconstituent of this zone, although its first occurrence isin the late Kimmeridgian. Achomosphaera neptuni (Ei-senack) and Cyclonephelium distinctum Deflandre andCookson first appear in the middle part. Species thatappear stratigraphically near the top (early late Berriasi-an) include Ctenidodinium elegantulum Millioud, Dia-canthum hollisteri, Gonyaulacysta helicoidea (Eisenackand Cookson) Sarjeant, the tabulated Muderongia cf.M. simplex of Fisher and Riley (1980), Scriniodiniumcampanulum Gocht, and Tanyosphaeridium salpinx.Cometodinium whitei dominates some of the assem-blages in this zone. P. neocomica, itself, is infrequent inthe early parts of the zone and increases in frequencytoward the top; cf. Prolixosphaeridium granulosum be-comes stratigraphically persistent at the base.

Distribution. Present in southeast France (section atBerrias), the Phoberocysta neocomica Zone has thus farnot been identified in sections studied from the NorthAtlantic, presumably because of the poorly palyniferousinterval directly below the B. johnewingii Zone (Habib,1978). Williams (1975) and Bujak and Williams (1978)used a zone defined by P. neocomica to date the oldestNeocomian in wells drilled offshore southeastern Can-ada. Davey (1979) placed the lowest occurrence of thisspecies in the latest Berriasian, perhaps because of theabsence of the lower part of the Berriasian in the Spee-ton Clay of England.

Biorbifera johnewingii ZoneDefinition. Interval from the first appearance of

Biorbifera johnewingii to the first appearance of Drug-gidium apicopaucicum.

Age. Early late Berriasian (ammonite D. dalmasiSubzone) to the top of the Berriasian.

Remarks. Species that have their first occurrence atthe base of this zone include Hystrichodinium pulchrumDeflandre sensu stricto and Kleithriaspheridium fascia-tum Davey. Species commencing slightly above the baseinclude Heslertonia heslertonensis (Neale and Sarjeant),Oligosphaeridium complex (White), and Polysphaerid-ium warrenii Habib. There are several taxa that com-mence in the uppermost part of this zone. Notable amongthese are Aprobolocysta varigranosa Duxbury, Batiola-dinium gochtii (Alberti), and Pseudoceratium pellifer-um Gocht. Amphorula metaelliptica is restricted to theBiorbifera johnewingii Zone. Cometodinium whitei is acommon constituent in many samples.

Distribution. In southeast France B. johnewingii ispresent in the Berriasian of three of the sections studied(Lacisterne, Ginestous-la Garenne, Orpierre). It is also

630

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Figure 3. Ammonite-dated dinoflagellate stratigraphy and zonation of Neocomian stratotype and parastratotype sections.


present in the Berriasian of the Speeton Clay in En-gland, although as a rare constituent. B. johnewingii iswidespread in offshore southeastern Canada, and in theNorth Atlantic. It also occurs in the Neocomian of theSacramento Valley sequence of California (Habib andWarren, 1973).

Druggidium apicopaucicum ZoneDefinition. Interval from the first appearance of

Druggidium apicopaucicum to the Phylogenetic appear-ance of D. deflandrei.

Age. Earliest Valanginian (basal T. pertransiens Zone)through early late Valanginian (Saynoceras verrucosumZone).

Remarks. Prismatocystis cylindrica Habib, Muder-ongia extensiva Duxbury, and M. tomaszowensis Alber-ti appear at the base of this zone. Avellodinium falsi-ficum Duxbury starts just above the base of this zoneand Kleithriasphaeridium simplicispinum (Davey andWilliams) has its first appearance near the base. Discor-sia nanna (Davey) first appears near the top.

Distribution. In southeastern France Druggidiumapicopaucicum is present within this zone in the Orpi-erre and La Charce sections. The D. apicopaucicumZone is widely distributed in the North Atlantic, nearboth the eastern and western margins. The nominativespecies occurs rarely elsewhere in western Europe (e.g.,basal Valanginian of the Speeton Clay) or is absent.

Druggidium deflandrei ZoneDefinition. Interval from the first appearance of D.

deflandrei to the first appearance of Odontochitinaoperculata.

Age. Late Valanginian (Himantoceras trinodosumZone) to late Hauterivian (almost to the top of the Sub-say nella sayni Zone).

Remarks. A species making its first appearance at thebase of this zone is Dingodinium cerviculum. Speciesappearing in the lower part of this zone include Hy-strichodinium furcatum Alberti, Oligosphaeridium as-terigerum (Gocht), Batioladinium longicornutum (Al-berti), Gardodinium trabeculosum (Gocht) Alberti sen-su stricto, and Nelchinopsis kostromiensis (Vozzhen-nikova). Species occurring near the top of this zone in-clude Callaiosphaeridium asymmetricum (Deflandre andCourteville) sensu stricto, Hystrichosphaerina schinde-wolfii Alberti, Muderongia staurota Sarjeant, Protoel-lipsodinium spinosum Davey and Verdier, and Coroni-fera oceanica Cookson and Eisenack. Species becomingextinct in the basal part of this zone include Biorbiferajohnewingii, Diacanthum hollisteri, and Scriniodiniumdictyotum.

Distribution. The nominative species is present in thesections at Orpierre, La Charce, Route d'Angles, andSisteron in southeast France. It is also present as a rareelement in the Hauterivian of the Speeton Clay in En-gland. This zone is equivalent in age to the combinedDruggidium deflandrei-D. rhabdoreticulatum Zones ofthe North Atlantic (Fig. 2). In the western North Atlan-tic B. johnewingii, Diacanthum hollisteri and S. dictyo-

tum also disappear stratigraphically in the lower part ofthe Druggidium deflandrei Zone.

Odontochitina operculata ZoneDefinition. The lower boundary is defined by the first

appearance of Odontochitina operculata. The top of thezone is undefined because the stratotype study does notextend beyond latest Hauterivian.

Age. Late Hauterivian (near the top of the Subsay-nella sayni Zone) at the base.

Remarks. Aprobolocysta eilema Duxbury, Cribro-peridinium sepimentum Neale and Sarjeant, and Mu-derongia tetracantha (Gocht) have their lowest occur-rence at the base of this zone in the investigated type sec-tion. Druggidium apicopaucicum becomes extinct in thesame interval.

Distribution. O. operculata is present in sections atRoute d'Angles and Sisteron in southeast France; and itfirst occurs in the 5. gottschei Zone of the Speeton Clayof England. The stratigraphic level is the same as thefirst occurrence in southeast France. O. operculata is acosmopolitan species that has been reported as appear-ing at this approximate level in widely separated areas.Davey (1979) defined an Odontochitina operculata Zoneas beginning at the Hauterivian/Barremian boundaryin the Speeton Clay.

The North Atlantic zonation (Habib, 1977) was datedoriginally from the section recovered at Site 105, throughcomparison with Thierstein's nannofossil study (1975)of the Berriasian-Hauterivian interval in that sectionand with Luterbacher's report (1972) of Albian plank-tonic foraminifers. Subsequent study of the sectionfrom Hole 391C (Habib, 1978) yielded zonal fossils (e.g.Phoberocysta neocomicá), which permitted comparisonwith stratotype Neocomian-Aptian sections publishedby Millioud (1969).

Our investigation of Neocomian stratotype and am-monite-dated parastratotype sections shows that mostof the species used to zone and date the North Atlanticoccur in both areas, and provides evidence of preciseage determinations where it was previously lacking. Forexample, at both Site 105 and Hole 391C the lowerboundary of the Biorbifera johnewingii Zone was datedas undifferentiated Berriasian because of the paucity ofdinoflagellates in the interval directly above the Creta-ceous/Jurassic boundary dated by Thierstein (1975). Inthe European sections, B. johnewingii appears very closeto the boundary between the early and late Berriasian.We use this evidence to date the first occurrence of thisspecies in the North Atlantic as early late Berriasian.Support for this conclusion is drawn from Site 387 nan-nofossil data (Okada and Thierstein, 1979), which datethe interval containing the first appearance of B. johne-wingii as late Berriasian.

Species of Druggidium, for example, D. apicopauci-cum Habib and D. deflandrei (Millioud), also occur inboth areas of study and in corresponding chronostrati-graphic order. The base of the Druggidium apicopauci-cum Zone was dated early Valanginian in the North At-lantic, which is in general agreement with the earliest

632


Valanginian appearance of this species in the stratotypearea. Also, in both areas D. deflandrei appears in as-semblages dated late Valanginian.

The Druggidium rhabdoreticulatum Zone is wide-spread in the western North Atlantic, although its age isuncertain (Hauterivian or Barremian, according to Ha-bib, 1977) because of its absence in the investigated stra-totype sections. However, Davey (1979) reported thefirst appearance of D. rhabdoreticulatum in the SpeetonClay of England in Hauterivian assemblages, and in thesame stratigraphic order beneath the first appearance ofOdontochitina operculata. The Druggidium rhabdoreti-culatum Zone is retained for the North Atlantic becauseof its value in correlation; it occurs at such widely sep-arated localities as those of Sites 105, 387, and Hole391C (Fig. 1). It is assigned to the Hauterivian.

In the stratotype sections, O. operculata appears stra-tigraphically in sediments of the late Hauterivian (Fig.3), which allows a more precise age determination forthe base of the zone defined by this species than theHauterivian or Barremian originally proposed by Habib(1977). On the basis of the stratigraphy of Hole 391C,two subzones were distinguished in the Odontochitinaoperculata Zone: the lower Phoberocysta neocomicaSubzone and the higher Subtilisphaera perlucida Sub-zone. Habib (1978) defined the lower subzone as the in-terval from the first appearance of O. operculata to thelast appearance of P. neocomica. This subzone is nowrenamed the Odontochitina operculata Zone (sensustricto), as the name originally given (Odontochitina op-erculata Zone sensu Habib, 1977) is abandoned.

Less information is available for comparing the Ap-tian-Cenomanian zonation in the North Atlantic withEuropean stratotype sections. Davey and Verdier (1971;1974) described the dinoflagellate stratigraphy of thetype Albian and Aptian stages, but it contains relativelyfew species in common with the North Atlantic. In theNorth Atlantic, the Subtilisphaera perlucida Zone isconsidered to range from Aptian to early Albian in thestratigraphic interval containing S. perlucida from im-mediately above the last occurrence of P. neocomica tothe first appearance of Spinidinium vestitum Brideaux.Subtilisphaera perlucida occurs in both the La Bédouleand Gargas Aptian stratotype sections studied by Daveyand Verdier (1974), along with Dingodinium cerviculumCookson and Eisenack. In Hole 391C, D. cerviculum andDruggidium deflandrei range into the Subtilisphaeraperlucida Zone. The stratigraphic disappearance ofDingodinium cerviculum and Druggidium deflandrei isconsidered useful for dating sediments close to the Ap-tian/Albian boundary in the North Atlantic, becauseboth occur in intervals independently dated Aptian atseveral North Atlantic sites. For example, Dingodiniumcerviculum and Druggidium deflandrei occur (Habib,1972) in the eastern North Atlantic in an interval thatcalcareous nannofossil evidence indicates ranges fromearly to late Aptian (Roth and Thierstein, 1972; see alsoThierstein, 1973, fig. 23). In the stratotype stratigraphy,D. deflandrei last appears in the late Aptian at Gargasand Dingodinium cerviculum last appears in few speci-mens in the earliest Albian.

The Spinidinium vestitum Zone ranges from middleAlbian or late early Albian to Vraconian Albian, in thestratigraphic interval defined by Habib (1977) from thefirst appearance of the nominative species to the phy-logenetic appearance of Spindinium echinoideum. Theprecise age of the lower boundary of this zone is un-known; planktonic foraminiferal evidence at Site 105 (J.Sigal, personal communication, 1981) indicates the mid-dle or late early Albian. The upper boundary lies withinthe Vraconian Albian, on the basis of foraminiferal evi-dence at Site 105 and Hole 101A (Luterbacker, 1972).

The Spinidinium echinoideum and Trithyrodiniumsuspectum Zones of Habib (1977) range collectivelyfrom Vraconian Albian through the Cenomanian. Theboundary between the two zones was defined at Site 105by the first appearance of T. suspectum in the middleCenomanian. At Site 137 (Habib, 1972), T. suspectumfirst appears in a relatively thick section dated Ceno-manian.

AGE OF LITHOSTRATIGRAPHIC UNITS

Based on the ages provided from the dinoflagellatestratigraphy, the lowermost, unnamed lithostratigraph-ic unit (Section 534A-127-2 to Sample 534A-111-1, 7cm) ranges from middle Callovian to basal Kimmer-idgian. The middle Callovian/late Callovian boundaryis placed between Samples 534A-124-1, 54-56 cm and534A-124-1, 8-10 cm, on the basis of the last appear-ance of Ctenidodinium gochtii in the former sample.The Callovian/Oxfordian boundary lies in the darkgreen radiolarian claystones, between Samples 534A-122-2, 68-70 cm and 534A-121-1, 46-48 cm. The bound-ary is defined by the first appearance of Polygoniferaevittii in the latter sample. The Oxfordian/Kimmeridg-ian boundary lies very near the top of this unit, betweenSamples 534A-112-1, 69-71 cm and 534A-111-1, 27-29cm. It is defined by the first appearance of Occisucystabalia in the latter sample, approximately 20 cm belowthe lithologic boundary.

The lower green-gray interbedded calcareous clay-stone and limestone lithology of the Cat Gap Formation(Samples 534A-111-1, 7 cm to 534A-1O3-1, 107 cm) is al-most entirely Kimmeridgian. The Kimmeridgian/Tithon-ian boundary is placed very near the top of this unit,between Samples 534A-105-1, 17-18 cm and 534A-104-2,59-61 cm. The Tithonian age of the latter sample isrecognized by the occurrence of Cometodinium whitei.The base of this facies is earliest Kimmeridgian. Pre-viously, the oldest lithology of the Cat Gap Formationwas cored at Site 100 (Hollister et al., 1972). It was con-sidered to be Oxfordian or Callovian, because of theevidence provided by dinoflagellates (Habib, 1972; Jan-sa, et al., 1979). However, restudy of the lowermost sed-iment at this site (Core 100-10) reveals the presence ofDinopterygium dimorphum, Occisucysta evittii, and O.balia, which indicates an age not older than Kimmeridg-ian. This assemblage also contains the pentagonal mor-photype of Sirmiodinium grossii.

The upper grayish red calcareous claystone lithology(Samples 534A-103-1, 107 cm to 534A-92-2, 40 cm) ofthe Cat Gap Formation is Tithonian. In Hole 534A, the

633


A

4c

B

6c

7c

Figure 4. Druggidium apicopaucicum Habib presented in a schematic, Kofoid-style tabulation of the mi-crographs illustrated in Plate 3. A. Plate 3, Figure 3—tabulation of epicyst and cingulum. (Attachedopercular pieces are indicated by diagonal pattern.) B. Plate 3, Figures 1 and 2—enlarged view of pre-apical, apical, and anterior intercalary cluster of plates. (Dashed line vertically bisecting the first apicalplate indicates that in some specimens it is subdivided into two plates. Nearly square sixth and seventhplates of the cingulum are diagnostic of the genus.) (See Taxonomic Note section for an explanation ofsymbols.)

Tithonian is represented by a thicker section than thatindicated by calcareous nannofossils (Site 534 report,this volume), because of the stratigraphically lower po-sition of the Kimmeridgian/Tithonian boundary de-fined by dinoflagellates. The stratigraphic disparity ofthis boundary is evident at Site 105 as well. Thierstein(1976) placed the Kimmeridgian/Tithonian boundary be-tween Cores 105-34 and 105-35, based on the nannofos-sil evidence. Although the dinoflagellate stratigraphy ofthe Jurassic at Site 105 has not yet been restudied,Habib (1976) indicated that C. whitei ranges down toSample 105-35,CC. This indicates that the Kimmeridg-ian/Tithonian boundary at Site 105 is approximately 9m lower (e.g., between Cores 105-35 and 105-36) thanthat indicated by the nannofossils.

At Hole 534A the age of the Blake-Bahama Forma-tion ranges from Tithonian at the base, close to the Ju-rassic/Cretaceous boundary, to early Bedoulian Aptian,at the top of the turbiditic beds. The Jurassic/Creta-ceous boundary is placed between Samples 534A-91-3,40-41 cm and 534A-91-2, 57-58 cm, based on the firststratigraphically persistent appearance of Prolixosphae-ridium sp. in the latter sample. This boundary is ap-proximately 10 m higher than the boundary between theBlake-Bahama Formation and the underlying Cat GapFormation. The age of the upper boundary is based onthe last appearance of Phoberocysta neocomica in Sam-ple 534A-49-4, 30-32 cm. The turbiditic interval ofCores 534A-64 to 534A-49 ranges from the Hauterivianto early Bedoulian.

The Hatteras Formation ranges from early BedoulianAptian to Vraconian Albian. The interbedded transi-tional lithologies of Cores 534A-48 to 534A-43 are Ap-tian, as they are within the interval from the last ap-pearance of P. neocomica to the last appearance ofDruggidium deflandrei. The variegated claystone inter-val of Cores 534A-42 to 534A-40 is largely barren of pa-

lynomorphs. However, the occurrence of D. deflandreiin Sample 534A-41-6, 42-44 cm indicates that this strati-graphic level is not younger than the late Aptian. Thecarbonaceous clay lithology of Cores 534A-39 to 534A-32 is of early Albian to late Albian. The interval ofCores 534A-30 to 534A-27 is Vraconian Albian.

TAXONOMIC NOTE

Based on the scanning electron microscopy of type material inSample 105-24-1, 100-102 cm at Site 105 (Habib, 1973), the typespecies of Druggidium, D. apicopaucicum is shown (Plate 3; Fig. 4) tohave the cyst tabulation formula Pr., 4', 4a, 7" , 7c, 6 '" , lp, 1"" ,s + as, and the archeopyle formula 2P3»_4». The hypocystal tabula-tion and the tabulation of the cingulum remain the same as originallydescribed by Habib (1973). However, the epicystal tabulation is re-vised, based mainly on micrographs of the small cluster of plates nearthe apex.

The pre-apical plate is subcircular and contains a small plug at itscenter. The apical series consists of four plates, of which the fourth issmallest and most slender. The third apical plate is located dorsal ofthe pre-apical plate. The anterior intercalary series consists of fourtrapezoidal plates, all of which at least partially contact the thirdapical plate. The precingular series consists of seven plates. The firstand seventh precingular plates lie on either side of the anterior sulcalplate and are the most slender in the series. The archeopyle formsfrom the opening of the third and fourth precingular plates. The oper-cular pieces remain attached on the cyst in D. apicopaucicum, alongthe cingulum.

ACKNOWLEDGMENTS

R. J. Davey (Shell U. K. Exploration and Production Co., Lon-don) and H. L. Cousminer (U.S. Geological Survey, Washington)critically reviewed the manuscript. S. Hogg prepared the samples forstudy. M. Rafanelli typed the manuscript. C. Robertson and A. Jaro-szewski prepared the diagrams.

We are grateful to Chevron Oil Field Research Company for pro-viding time and facilities for this study. This study was supportedby a grant from the National Science Foundation, OCE-7913191, atQueens College.

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Plate 1. Dinoflagellate species with diagnostic datums in the Jurassic (magnifications not to scale; dimensions of each specimen specified inmicrometers). 1, 4. Sirmiodinium grossii Alberti (pentagonal morphotype) (note perforation near antapex), (1) 90 × 87 µm. Sample534A-106-1, 3-4 cm. (4) 98 × 90 µm. Sample 100-10-2, 145-147 cm at Site 100. 2. Occisucysta evittii (Dodekova). Note 2P archeopyle and lackof apical horn. 75 × 78 µm. Sample 534A-104-2, 59-61 cm. 3. Cometodinium whitei (Deflandre and Courteville). 80 × 75 µm. Sample534A-84-7, 0-2 cm. 5. Stephanelytron redcliffense Sarjeant, emended Stover, Sarjeant, and Drugg. 55 × 51 µm. Sample 534A-121-1, 8-10cm. 6. Dinopterygium dimorphum (Ioannides, Stavrinos, and Downie). 85 × 86 µm. Sample 534A-106-1, 3-4 cm. 7. Ctenidodinium norrisii(Pocock). Note faint penetabular ridges within plate boundaries. 87 × 109 µm. Sample 534A-124-1, 74-75 cm. 8. Occisucysta balia Gitmez.67 × 59 µm. Sample 534A-111-1, 27-29 cm. 9. Pareodinia evittii (Pocock). 52 × 40 µm. Sample 534A-127-2, 34-35 cm.

636


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Plate 2. Dinoflagellate and spore species with diagnostic datums in the Jurassic (magnifications not to scale; dimensions of each specimen specifiedin micrometers). 1-3. Polygonifera evittii Habib. Specimens from paratype material in Sample 100-10-2,145-147 cm at Site 100, (1) archeopylemargin reveals sulcal notch on ventral surface, ventral compression folds near antapical end of pericyst, 60 × 62 µm, (2) same specimen, dorsalview (characteristic, long compression fold in dorsal hypocyst)., (3) specimen with single opercular piece (tA) in place (long first apical plate ex-tends to sulcal region; apical horn is absent in this species; endocyst fills epicystal end of pericyst, leaving pericoels in the cingular and hypocystalareas [hypocavate]), 58 × 62 µm. 4. Scriniodinium dictyotum Cookson and Eisenack. Reticulate ectophragm. 105 × 63 µm. Sample534A-104-2, 59-61 cm. 5. Hystrichogonyaulaxpectinigera (Gocht). Epicavate specimen with spinate plate boundaries. 55 × 42 µm. Sample534A-127-2, 34-35 cm. 6. Egmontodinium polyplacophorum Gitmez and Sarjeant. 75 × 55 µm. Sample 534A-105-2, 92-94 cm. 7. Litho-dinia sp. 55 × 52 µm. Sample 534A-127-2, 34-35 cm. 8. Cicatricosisporites sp. Spore attributed to the schizaeaceous ferns. 75 × 72 µm. Sample534A-126-3, 13-17 cm. 9. Ctenidodinium ornatum (Eisenack). 85 × 85 µm. Sample 534A-121-1, 8-10 cm.

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Plate 3. Druggidium apicopaucicum Habib. Scanning electron micrographs of specimens from paratype material in Sample 105-24-1, 100-102 cmat Site 105. 1-2. Tabulation of ventral surface, (1) × 2900, (2) same specimen with enlarged view of epicystal plates, × 7000 (Tabulation of thisillustration is given in Fig. 4B in the text). 3. Apical view of epicyst (compare with Fig. 4A in the text). × 3000. 4. Ventral surface. Large an-tapical plate tapers towards antapex, where it abuts the antapical margin of the slender fourth postcingular plate. ×2700. Note the presence ofthe small acritarch Tabulimicrocystis tetragonis Habib and Knapp near the lower left-hand corner of the micrograph. 5. Dorsal view ofspecies, showing slender fourth postcingular plate. Attached opercular pieces of 2P archeopyle evident. ×2700. 6. Contact of antapical platewith third, fourth, and fifth postcingular plates. Note small, circular antapical perforation in this specimen. ×2700.

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