(Figure 2) Distribution of planktonic foraminifera in the upper Paleocene of DSDP Hole 93-605

• Main Authors: Nederbragt, Alexandra J, von Hinte, J E
• Format: Dataset
• Language: English
• Published: PANGAEA 1987
• Subjects: 93-605; Acarinina mckannai; Acarinina soldadoensis; Deep Sea Drilling Project; DEPTH; sediment/rock; DRILL; Drilling/drill rig; DSDP; DSDP/ODP/IODP sample designation; Foraminifera; benthic; Glomar Challenger; Leg93; Morozovella acuta; Morozovella aequa; Morozovella angulata; Morozovella occlusa; Morozovella pusilla; North Atlantic; Planorotalites chapmani; Planorotalites pseudomenardii; Radiolarians abundance; Sample code/label; Subbotina primitiva; Subbotina triloculinoides; Subbotina velascoensis; Planktonic foraminifera
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.250715; https://doi.org/10.1594/PANGAEA.250715

Good faunal preservation in the upper part of the Planorotatites pseudomenardii Zone at Deep Sea Drilling Project Site 605, northwestern Atlantic, allows a biometric analysis of the upper Paleocene planktonic foraminiferal species Planorotatites pseudomenardii (Belli), a keeled species that probably developed from a middle Paleocene unkeeled Planorotalites form. Multivariate analysis shows a consistent separation of all Planorotatites specimens into two groups, which are differentiated by the presence or absence of a complete keel; other variables are only of minor importance. The keeled group coincides with P. pseudomenardii. We recognize only one unkeeled species, Planorotalites chapmani (Parr), with Planorotalites ehrenbergi (Bolli), Planorotalites imitata (Subbotina), Planorotalites planoconica (Subbotina), Planorotalites troelseni (Loeblich and Tappan), and Planorotalites hausbergensis (Gohrbrandt) as junior synonyms. P. chapmani ranges from the middle Paleocene to at least the top of the upper Paleocene. The morphology of P. pseudomenardii does not change significantly, and although the frequency of Planorotalites is variable, the proportion of P. pseudomenardii to all Planorotalites varies only slightly around 65% in the upper two-thirds of its range at Site 605. However, in the top 1.5 m of its range the proportion of P. pseudomenardii decreases; in the same section, all Planorotalites specimens show a reduction in the size of their tests, suggesting that a temporary change in environmental conditions led to the exit of P. pseudomenardii\ in Magnetozone C24R at Site 605—apparently higher than expected from current standard zonations. Unkeeled Planorotalites, in contrast to R. pseudomenardii, persisted and regained normal size. The entry of P. pseudomenardii at Site 605 cannot be described in the same detail because of low frequencies of Planorotalites specimens and an erratic distribution of P. pseudomenardii in the lower part of its range. Many of the washed residues of the samples from these sediments ...