East Antarctic glacial history through microfossil analyses of the Pagodroma Group

University Of Nebraska-Lincoln, Lincoln NE

Investigators

Abstract

0089899 Harwood This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, supports a micropaleontological investigation of Pagodroma Group sediments to complement and enhance prior stratigraphic and paleoenvironmental studies of these Cenozoic glacial deposits of East Antarctica. Preliminary results indicate the presence of Oligocene (?), middle Miocene, upper Miocene and Pliocene-Pleistocene glaciomarine strata that have the potential to contribute significantly to our understanding of the past fluctuations in the extent and character of the East Antarctic Ice Sheet (EAIS). These strata were deposited in a glacial system involving EAIS drainage through the Lambert Glacier and repeated marine incursion and ice margin/grounding line retreat across a distance of more than 800 km. Paleontological and sedimentological information present within these strata have the potential to provide baseline climate information bearing on the history of the EAIS. The Pagodroma Group sequences will provide a Neogene record of glaciomarine deposition on the continental interior that will expand what is already known from drill cores and outcrops in the Dry Valley region and the Vestfold Hills. These deposits are dated biostratigraphically by the occurrence of in situ diatom and foraminifera assemblages that occur in laterally-continuous beds of diatomaceous marine mudstone within a sequence of diamictite. These fossils provide direct age correlation to Southern Ocean and Ross Sea biostratigraphic schemes. Open marine diatom production and in situ diatom sedimentation is noted in several deposits of the Pagodroma Group that are at least 300 km inland from the current coastline. This new research will focus on establishing the age of different deposits of the Pagodroma Group through the study of in situ and glacially reworked microfossil assemblages. This will aid in the reconstruction of a composite history of the EAIS-Lambert Glacier-Amery Basin-Prydz Bay system. Primary objectives of this proposal are: (1) to develop a temporal and spatial record of Neogene EAIS variability, and (2) to test hypotheses that predict future changes in the EAIS in response to elevated global temperatures with geologic data. In addition, biostratigraphical and paleoecological analyses can reveal sea-surface temperature, sea level and sea-ice conditions, among other environmental parameters at the time of deposition. The ability to date and interpret these paleoenvironmental conditions is improving steadily through continued study of Cenozoic Antarctic diatom-bearing deposits, yet much remains to be done. Analyses will be undertaken on 250 Pagodroma Group samples collected during the 1997/98 field season. Currently 116 samples are available from deposits on the Amery Oasis, which is 250 km inland from the modern coast; 5 samples from Mt Stinear, 500 km inland; and 84 samples from Mt Menzies, which is 600 km inland. The bulk of this project will be conducted by a post-doctoral scientist, who will continue to improve the biostratigraphic and paleoecological use of diatoms and further extend his education and experience in Cenozoic Antarctic diatom paleontology. Future stratigraphic drilling programs that are planned for the Antarctic shelf and margin by numerous international Antarctic programs will require the skills of several experienced diatom paleontologists to provide age and environmental control for recovered materials. In summary, this project will provide further experience and training for a postdoctoral researcher on important materials that will help to answer current questions about Neogene variability of the East Antarctic Ice Sheet and the likely response to elevated global temperatures in the future.