Earth Sciences Seminar Series
Fall 2024
Friday October 18th
12:30PM
McHugh 301
Paleoclimatic Implications of Warmer Water Planktic Foraminifera in the Latest Oligocene to Early Pleistocene of the Ross Sea, Antarctica
R. Mark Leckie, University of Massachusetts Amherst
In collaboration with PhD student Samantha Bombard, and former MS student Julia Seidensteibn
Species of planktic foraminifera known from subtropical and temperate waters have been discovered in sediment cores collected from the Antarctic continental shelf. These sediments were deposited after the continent had glaciated to various extent over the past 25 million years. This raises questions about the nature of Antarctic ocean, climate, and ice sheet variability during past times of global warmth. The presence of warmer water planktic foraminifera on the Ross Sea continental shelf provides biotic evidence for polar amplification in Antarctica at times during the Neogene and early Quaternary, including the uppermost Oligocene-lower Miocene of DSDP Site 270, lowerto middle Miocene of IODP Site U1521, and Pliocene to lower Pleistocene IODP Site U1523.
At Site 270 and Site U1521 we note persistent occurrences of a presumed planktic foraminifer endemic to Antarctica(Antarcticella antarctica), as well as sporadic and rare species with wider biogeographic ranges, including Globoturborotalita druryi, Trilobatus trilobus, T. quadrilobatus, Dentoglobigerina globosa, Globigerinita glutinata, G. uvula, Turborotalita quinqueloba, Paragloborotalia siakensis, P. cf. pseudocontinuosa, Globorotaloides suteri, Tenuitella angustiumbilicata, and T. munda. At Site U1523, the presence of Globigerinoides ruber and Globoconella inflata in a single sample likely correlates with MIS G17 (~2.95 Ma). The last occurrence of temperate planktic foraminifera (Globigerina bulloides, G. falconensis) at Site U1523 was ~1.82 Ma, afterwhich time the Ross Sea became increasingly colder and isolated by the Antarctic Circumpolar Current (ACC).
The low abundance of these warmer water planktic foraminiferasuggests the species were likely not living in the Ross Sea, but rather were transported by ocean currents to the Ross Sea. Their presence may signal times when the Polar Front (PF) was closer to Antarctica, the sea surface temperature gradient across the PF was weaker, and/or when the ACC was weaker. The sporadic occurrences of warmer water planktic foraminifera suggest polar amplification in the Ross Sea at times during the early Miocene and MCO (Miocene Climatic Optimum ~16.9-14.7 Ma), andinterglacials of the MMCT (Middle Miocene Climate Transition ~14.7-13.8 Ma), Pliocene, and early Pleistocene.
For more information, contact: Christin Donnelly at christin.donnelly@uconn.edu