Biogeography of Campanian-Maastrichtian Calcareous Plankton in the Region of the Southern Ocean: Paleogeographic and Paleoclimatic Implications

• Main Authors: Huber, Brian T., Watkins, David K.
• Format: Text
• Language: unknown
• Published: DigitalCommons@University of Nebraska - Lincoln 1992
• Subjects: Earth Sciences; Antarctic; Southern Ocean; The Antarctic; Antarctic Peninsula; Austral; Pacific; Indian; New Zealand; Maud Rise; Antarc*; Antarctica; Planktonic foraminifera
• Online Access: https://digitalcommons.unl.edu/geosciencefacpub/242; https://digitalcommons.unl.edu/context/geosciencefacpub/article/1243/viewcontent/Watkins_1992_ARS_Biogeography_of_Campanian_Maastrichtian_Calcareous_Pankton.pdf

Analysis of biogeographic distribution patterns among Campanian-Maastrichtian calcareous nannoplankton and planktonic foraminifera from the southern high latitudes provides insight to changes in circum-Antarctic climate and surface circulation surface routes. Both microfossil groups are similarly characterized in the early Campanian by low-diversity, cosmopolitan species with few or no austral provincial taxa. This changes by late Campanian-early Maastrichtian time as austral species diversified and began to dominate the high-latitude assemblages. Maximum diversity of austral provincial taxa occurs during the late Campanian among the planktonic foraminifera and in the early Maastrichtian among the calcareous nannoplankton. Climatic cooling is considered the cause for the decline from 53 nannofossil species during the early Maastrichtian to 20 species toward the end of the Maastrichtian as well as the equatorward shifts of the nannofossil Nephrolithus frequens and the planktonic foraminifer Abathomphalus mayaroensis during the late Maastrichtian. On the other hand, the poleward migrations of the planktonic foraminifer Pseudotextularia elegans and the nannofossil Watznaueria barnesae less than 500,000 years before the Cretaceous/Tertiary extinction event correspond with a negative δ18O excursion observed at Maud Rise Site 690, suggesting that these species shifts were caused by a brief high-latitude warming event. The high degree of provinciality among the late Campanian-early Maastrichtian calcareous plankton reflects segregation of a cool, high-latitude water mass from warmer, subtropical surface waters. A long-term climatic cooling and paleogeographic changes related to the breakup of the southern Gondwana continents are considered the major factors that caused the paleocirculation and biogeographic changes. Seafloor spreading and subsidence between Antarctica, Australia, and New Zealand, northward drift of South America from the Antarctic Peninsula, and a global rise in sea level during the middle Campanian ...