K-T boundary in DSDP Holes 62-465 and 74-527 (Table 2)

• Main Author: Henriksson, Anders S
• Format: Dataset
• Language: English
• Published: PANGAEA 1996
• Subjects: 62-465; 74-527; Age; relative; Comment; Deep Sea Drilling Project; DEPTH; sediment/rock; DRILL; Drilling/drill rig; DSDP; DSDP/ODP/IODP sample designation; Event label; Glomar Challenger; Leg62; Leg74; North Pacific/CONT RISE; Sample code/label; South Atlantic; Pacific; South Atlantic Ocean
• Online Access: https://doi.pangaea.de/10.1594/PANGAEA.754539; https://doi.org/10.1594/PANGAEA.754539

The global extinctions linked to the Cretaceous-Tertiary (K-T) boundary severely affected marine pelagic organisms. The K-T boundary intervals at Deep Sea Drilling Project (DSDP) Site 527 (Leg 74) in the South Atlantic Ocean and Site 465 (Leg 62) in the Pacific Ocean were studied for changes in calcareous nannofossil assemblages from the late Maastrichtian to the early Paleocene. The sections analysed cover 180 kyr of the terminal Cretaceous and 200 kyr of the earliest Tertiary. Absolute and relative abundances of calcareous nannoplankton were calculated for both the entire flora and for individual species. No decrease in the number of species occurs towards the K-T boundary; relative and absolute abundances of different species are fairly stable throughout the terminal 180 kyr of the Cretaceous. At the K-T boundary the calcareous nannoflora shows a drastic and instantaneous decrease in absolute abundance. Typical Cretaceous species became extinct at the K-T boundary, but are present in the lowermost Tertiary as a result of bioturbation and reworking of the sediments. Very few species survived the K-T boundary. The species that occur sporadically in extremely low numbers in the Cretaceous, exhibit stable relative and absolute abundances through the lower Tertiary. Evolving Tertiary species appeared at the boundary and vary only moderately in absolute abundance through the lowermost Paleocene. The productivity of calcareous nannoplankton is determined here as the nannofossil accumulation rate (NFAR), which is suggested as an estimate of surface-water primary productivity. The terminal Cretaceous NFAR values were high and stable. At the K-T boundary the calcareous nannoflora suffered a 70-150-fold decrease in NFAR, indicating a catastrophic event. The Tertiary NFAR values remained low and fairly constant through the first 200 kyr. The productivity of calcareous nanno- plankton in the earliest Tertiary was dominated by the calcareous dinoflagellate Thoracosphaera sp.