Distribution of benthic foraminifera in lower Cretaceous sediments of the Cuvuer Abyssal Plain in the Indian Ocean

Analysis of 66 samples from DSDP Site 263 (Cores 263-4R-4 to 263-29R-4) reveals a unique faunal composition with a predominance of agglutinated taxa, many of them previously unrecorded from any other DSDP and ODP Indian Ocean sites. A total of 66 agglutinated and 31 calcareous taxa are documented and five new species are described: Hippocrepina gracilis n.sp., "Textuluriopsis" elegans n.sp., Aaptotoichus challengeri n.sp., "Gaudryinopsis" pseudobettenstaedti n.sp. and "Gaudryina" cuvierensis n.sp. Three assemblages are recognized based on changes in the composition of dominant taxa and occurrences of stratigraphically important species: (1) a high-diversity Valanginian to Barremian Bulbobaculites-Recurvoides Assemblage (Cores 263-29R to - 18R), comprised of numerous elongate agglutinated forms, rare nodosariids, and variable numbers of tubes and ammodiscids; (2) a moderately diverse Aptian to Albian Rhizammina-Ammodiscus-Glomospira Assemblage (Cores 263-18R to -7R) with highly fluctuating numbers of the nominate taxa and Haplophragmoides, Trochammina, Verneuilinoides spp., and Verneuilina howchini; (3) a very low diversity Albian or younger Assemblage (Cores 263-6R to -4R) containing sparse agglutinated foraminifera, rare nodosariids and rotaliids. We interpret the assemblages as shelf to lower slope and consider them to reflect a deepening palaeobathymetry as the Cuvier margin subsided after the initial breakup of East Gondwana during the Valanginian. Our interpretation is in sharp contrast with initial palaeodepth estimates of less than 100 m, as well as with original chronostratigraphic interpretations based on foraminifera and nannofossils which correlated the base of the recovered interval with the Aptian. The absence of many cosmoplitan forms, despite high diversity suggests strong faunal differentiation in the Austral realm or endemisn within the Cuvier Basin during the Early Cretaceous.

Occurrence and estimated abundance of planktonic foraminifers at DSDP Leg 85 holes

Tropical planktonic foraminifers occur throughout the sequences at all sites of Leg 85, and the standard planktonic foraminiferal zonation of Blow (1969) is applicable to most of the recovered sequences. However, the abundance and state of preservation of foraminifers decline markedly in certain intervals because of the effects of dissolution. Although siliceous microfossils studied on this leg indicate recovery of nearly complete records for the Pleistocene to Oligocene interval, the planktonic foraminiferal biostratigraphy is interrupted by strongly dissolved sections at all sites. Particularly, faunas assignable to Zone N7 (early Miocene) and Zone N15-16 (early late Miocene) are almost totally unrecognizable throughout the eastern equatorial Pacific. Well-preserved and diverse planktonic foraminifers occur in the lower middle Miocene, where the evolutionary developments of Orbulina universa d'Orbigny and Globorotalia fohsi Cushman and Ellisor are well represented. The Orbulina first appearance datum is observed to be nearly coincident with the last occurrence level of the diatom Annellus californicus Tempère, thus .establishing an age of 15 Ma for this datum by using the paleomagnetic calibration of the diatom datum. Moderately well-preserved late Eocene planktonic foraminifers occur in the carbonate sediments immediately overlying the basalt basement at Sites 573 and 574. The Eocene-Oligocene faunal transition, however, is masked at both sites by an intercalation of metalliferous layers containing no planktonic foraminifers.

Mesozoic radiolarians of ODP Holes 129-800A and 129-801B

Rich radiolarian faunas were obtained continuously from Middle Jurassic to Lower Cretaceous radiolarite sequences at Sites 800 and 801, drilled during Ocean Drilling Program Leg 129 in the western Pacific. Occurrences of 90 taxa are presented in tables for these sites. Seven radiolarian zones, Dibolachras tytthopora, Cecrops septemporatus, Pseudodictyomitra carpatica, Pseudodictyomitra primitiva, Cinguloturris carpatica, Stylocapsa spiralis, and Tricolocapsa conexa in descending order, were recognized in this interval. The radiolarite sequences of Sites 800 and 801 encompass approximately the Berriasian to Hauterivian (or to Barremian) and the Bathonian/Callovian to Valanginian ages, respectively. At Site 801, a hiatus of early Oxfordian was identified.

Calcareous nannoplankton of DSDP Leg 43 holes

During Leg 43, six holes (Sites 382-387) were drilled in the western part of the North Atlantic Ocean; locations of sites are shown in Figure 1. Lower Cretaceous to Quaternary calcareous nannofossils were found in 127 of 189 cores recovered during the leg. The ages and zonal assignments of these fossiliferous cores based upon light-microscopical observation are given in Table 1. An almost continuous succession of nannofossil assemblages of the lower Maestrichtian to upper Paleocene is present at Site 384. A detailed investigation was conducted on samples at this site, and the evolution of approximately 50 species is documented through almost the entire Paleocene epoch.