(Table 1) Distribution of Lower Cretaceous calcareous nannofossils at DSDP Hole 93-603B

• Main Authors: Covington, J Mitchener, Wise, Sherwood W
• Format: Dataset
• Language: English
• Published: PANGAEA 1987
• Subjects: 93-603B; Assipetra infracretacea; Axopodorhabdus dietzmannii; Biscutum sp.; Braarudosphaera discula; Braarudosphaera regularis; Calcicalathina oblongata; Chiastozygus litterarius; Chiastozygus striatus; Chiastozygus tenuis; Conusphaera mexicana; Corollithion achylosum; Corollithion acutum; Corollithion conicus; Corollithion ellipticum; Cretarhabdus crenulatus; Cretarhabdus sp.; Cruciellipsis cuvillieri; Cruciplacolithus hayi; Cyclagelosphaera deflandrei; Cyclagelosphaera margerelii; Deep Sea Drilling Project; DEPTH; sediment/rock; Diadorhombus rectus; Diazomatolithus lehmanii; Diloma placinum; Diloma primitivum; Discorhabdus biradiatus; Discorhabdus ignotus; DRILL; Drilling/drill rig; DSDP; DSDP/ODP/IODP sample designation; Eiffellithus sp.; Ethmorhabdus hauterivianus; Glaukolithus diplogrammus; Glomar Challenger; Grantarhabdus coronadventis; Grantarhabdus meddii; Haqius circumradiatus; Hayesites irregularis; Leg93; Lithologic unit/sequence; Lithology/composition/facies; Lithraphidites alatus ssp. magnus; Lithraphidites carniolensis; Manivitella pemmatoidea; Manivitella sp.; Micrantholithus hoschulzii; North Atlantic
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.788888; https://doi.org/10.1594/PANGAEA.788888

Upper Berriasian to lower Aptian calcareous nannofossil assemblages have been studied from a siliciclastic deep-sea fan complex and a subjacent limestone sequence drilled beneath the lower continental rise in the western North American Basin, 270 miles (435 km) off Cape Hatteras, North Carolina (USA). Sharp lithologic facies changes and reworking by turbidites complicate the biostratigraphic interpretation, but provide an excellent opportunity to better distinguish "nearshore" from open-ocean nannofossil species, and to investigate the introduction of neritic taxa into the deep-see environment, a phenomenon that appears to have been widespread within the circum-North Atlantic during Neocomian times. Well-preserved assemblages in dark, carbonaceous claystones were probably displaced from the oxygen minimum zone along the upper slope or outer shelf. Neritic, continental margin species prevalent in this facies include the holococcolith Zebrashapka vanhintei n. gen., n. sp., Lithraphidites alatus magnus n. spp., Pickelhaube furtiva n. gen., and a host of nannoconids and micrantholiths. A qualitative evaluation of widely used guide fossils suggests that the triad of proposed markers for the base of Roth's Zone NC3 make their first appearances in the following (ascending) order: Diadorhombus rectus, TUbodiscus verenae, Calcicalathina oblongata. Of these, we chose the nominative species for the zone, T. verenae, to mark its base and to approximate the Berriasian/Valangian boundary. Cyclagelosphaera deflandrei is strongly affected by diagenesis and is therefore not a reliable index species for the base of Zone NC4 near the Valanginian/Hauterivian boundary (the last occurrence of T. verenae is also not suitable there). In addition, Lithraphidites bollii, a form apparently confined to the low latitudes of the Tethyan region, was absent at the more temperate Site 603 and not available as a subzonal marker for the upper Hautervian-lower Barremian (mid-NC4 and mid-NC5, respectively). Cruciellipsis cuvillieri, however, ...