Abundance of calcareous nannofossils across the K/T boundary at ODP Hole 113-690C (Table 1)

• Main Authors: Pospichal, James J, Wise, Sherwood W
• Format: Dataset
• Language: English
• Published: PANGAEA 1990
• Subjects: 113-690C; Acuturris scotus; Ahmuellerella octoradiata; Arkhangelskiella spp.; Biantholithus sparsus; Biscutum castrorum; Chiastozygus sp.; Cretarhabdus conicus; Cribrosphaerella daniae; Cribrosphaerella ehrenbergii; Cruciplacolithus primus; Cyclagelosphaera reinhardtii; DEPTH; sediment/rock; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Eiffellithus turriseiffelii; Epoch; Gartnerago spp.; Hornibrookina edwardsii; Joides Resolution; Kamptnerius magnificus; Lapideacassis sp.; Leg113; Markalius inversus; Micula decussata; Nannofossils; cretaceous; survivor; tertiary; Nannofossil zone; Neocrepidolithus spp.; Nephrolithus frequens; Ocean Drilling Program; ODP; Prediscosphaera cretacea; Prediscosphaera spinosa; Prediscosphaera stoveri; Sample code/label; Smear slide analysis; South Atlantic Ocean; Thoracosphaera spp.; Zygodiscus sigmoides; Antarc*; Antarctica; East Antarctica; Southern Ocean; Weddell Sea
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.746448; https://doi.org/10.1594/PANGAEA.746448

A biostratigraphically continuous, but intensely bioturbated, Cretaceous/Tertiary boundary sequence was cored during Ocean Drilling Program (ODP) Leg 113 on Maud Rise (65°S) in the Weddell Sea off East Antarctica. This interval is the first recovered by ODP/DSDP in the South Atlantic sector of the Southern Ocean and offers a unique opportunity to study the nannofossil sequences leading up to and beyond the terminal Cretaceous event at a high southern latitude. The K/T boundary lies just within Chron 29R and is placed at ODP Sample 113-690C-15X-4, 41.5 cm. An iridium anomaly was independently noted at about this level as well. Upper Maestrichtian-lower Paleocene sediments consist mostly of light-colored nannofossil chalks. Dark brown sediments at the base of the Danian (Zone CPla) are characterized by an increased clay content attributed to a drop in calcareous microplankton productivity following the terminal Cretaceous event. Although delineation of the boundary is hampered by intense bioturbation, the sharp color contrast between overlying clay-rich, dark brown chalks of the Tertiary and light cream colored chalks of the Cretaceous aids in the selection of the K/T horizon. Several dark colored burrows sampled at intervals as far as 1.3 m below the boundary and within the light colored Cretaceous chalk were found to contain up to 17% Tertiary nannofossils. Calcareous nannofossils from the boundary interval were divided into three groups for quantitative study. The three groups, "Cretaceous," "Tertiary," and "Survivor," exhibit a sequential change across the boundary with the Cretaceous forms giving way to a Survivor-dominated assemblage beginning at the boundary followed shortly thereafter by the appearance of the Tertiary taxa, Cruciplacolithus and Hornibrookina. The species, H. edwardsii, comprises nearly 50% of the assemblage just above the Zone CPla/CPlb boundary, an abundance not reported elsewhere at this level. Calculation of individual species abundances reveals several additional differences between ...