Latest Cretaceous/Paleocene deep-sea ostracode fauna at IODP Site U1407 (western North Atlantic) with special reference to the Cretaceous/Paleogene boundary and the Latest Danian Event

- At the K/Pg boundary, fauna changed with a background-level extinction.
- During the Latest Danian Event (LDE), fauna changed without extinction.
- LDE fauna had low diversity and a dominant species resistant to corrosive water.
- After the Danian, export productivity rose and remained at a relatively high level.

During the Paleocene, the marine plankton community recovered its diversity after a severe diversity loss at the Cretaceous/Paleogene (K/Pg) boundary. In general, changes in Paleocene deep-sea ostracode faunas are poorly understood. It is still unclear how the deep-sea ostracode faunas changed during compelling events such as the K/Pg boundary (66.04 Ma) and the Latest Danian Event (LDE: ~ 62.18 Ma), a transient Paleocene warming event. In this report, we describe a study on the latest Cretaceous-Late Paleocene ostracodes from Integrated Ocean Drilling Program Site U1407, off Newfoundland, in the northwestern Atlantic. Thirty-six ostracode taxa were obtained from 202 discrete samples that were collected from the interval between 66.3 and 57.3 Ma. Near the K/Pg boundary, 8% (2 of 25) of the Maastrichtian taxa became extinct. The extinction rate is estimated to be at most 0.12 E MSY− 1, which is equal to extinction rate of 12% per one million years and is in the same range as the background-level extinction rate. Comparing the extinction rates between different ocean basins such as Maud Rise and Blake Nose, the ostracode extinction at the K/Pg boundary displays striking geographical heterogeneity. Between the Maastrichtian and Danian, the ostracode faunas change from a biofacies dominated by shallow bathyal taxa to one dominated by deep bathyal taxa. During the LDE, ostracode faunas display an increase in their benthic ostracode accumulation rates and taxonomic diversity as well as an increase in the relative abundance of Krithe crassicaudata simultaneously with a decline in carbonate content. A similar change is commonly documented in fauna from the northeastern Atlantic during the Paleocene-Eocene Thermal Maximum (PETM; 56.0 Ma). In contrast to the PETM fauna, an extinction event is not recognized. Near the Danian/Selandian boundary, the ostracodes show an increase in export productivity. After the Danian, the ostracodes form a community that appears to tolerate warm and acidified water. Export productivity remains high during the Selandian and Thanetian.