Application of Tandem Accelerator Mass-Spectrometer Dating to Late Pleistocene-Holocene Sediments of the East Antarctic Continental Shelf

Abstract

Glacial recession from the Antarctic continental shelf is recorded by glacial-marine diamictons, sands, and overlying siliceous oozes. In order to clarify the chronology for this sequence, use was made of the University of Arizona tandem accelerator mass-spectrometer (TAMS) for 14C dating. Small samples of benthic and planktonic foraminifera were selectively removed from diamictons, graded sands, and surface sediments which were recovered from the Wilkes Land continental shelf and slope, East Antarctica. Organic carbon was also utilized as a source for TAMS dating of the siliceous oozes and muds. Uncorrected ages varied from 14,260 ± 140 to 3230 ± 200 yr B.P. Carbon fixed by phytoplankton and foraminifera is strongly influenced by old, glacial-derived CO2. Thus, reservoir corrections of up to 5500 yr are needed for the 14C dates. Iceberg turbation reworks foraminifera so that dates from resulting deposits (diamictons) are interpreted as maximum ages. The consistency of corrected ages from the shelf, along with the sedimentologic interpretation, suggests a rather recent recession, perhaps mid-Holocene for this portion of the East Antarctic ice sheet. Further application of the TAMS method should help clarify other problems concerning the late Quaternary glacial history of Antarctica.

Sediment distribution and sedimentary processes across the Antarctic Wilkes Land margin during the Quaternary

“…(3) The Quaternary is not entirely representative of glacial sedimentation during earlier times. That said, the fact that during the Pleistocene the ice sheet advanced to the outermost shelf, as reported in: previous studies on sediment cores (Milam and Anderson, 1981;Anderson et al, 1983;Domack et al, 1985;Domack et al, 1989), as evidenced by dating of the shelf cores in this and previous studies (Domack et al, 1989), and as implied by the erosion of all previously deposited and preserved topset strata (Fig. 4), suggests that at least the most recent foreset strata (i.e.…”

“…), only two studies were directed at understanding sedimentation across the margin, from the continental shelf to the lower continental rise (Payne and Conolly, 1972;Hampton et al, 1987a, b). Other sedimentological studies on this margin focused mainly on understanding the sediment distribution and processes on the shelf and the slope (Milam and Anderson, 1981;Anderson et al, 1983;Dunbar et al, 1985;Domack et al, 1989). In the two studies conducted across the margin, comparisons of coeval sedimentation and sedimentary processes during recent glacial/interglacial periods was difficult to establish because the lack of age control in sediment cores, though some level of correlation across the rise and abyssal plain was possible (Payne and Conolly, 1972).…”

Holocene Chronology for the Unconsolidated Sediments at Hole 740A: Prydz Bay, East Antarctica

“…The Amery Depression is typical of most shelf troughs along the East Antarctic margin in that it lies seaward of major glacier drainage systems and occupies an erosional depression between crystalline basement rock and sedimentary sequences of prerift, synrift, and/or glacial affinities. Though numerous basins of similar character can be found along the East Antarctic margin, the Amery is one of only two that have been investigated with respect to Holocene sediment accumulations; the other is the Mertz-Ninnis Trough, which was discussed by Domack et al (1989).…”

Recent advances in understanding Antarctic climate evolution

“…Radiocarbon dating of Antarctic marine sediments is plagued by a variety of difficulties, including variable water column carbon reservoir ages and sedimentary reworking that results in the mixing of older and younger materials (Domack et al 1989, Berkman & Forman 1996, van Beek et al 2002. However, independent estimates of reservoir age corrections are becoming available (Van Beek et al 2002) as are palaeomagnetic intensity age determinations for the deglacial interval (Brachfeld et al 2003) that serve to improve our ability to estimate the timing of key events on the Antarctic shelf during deglaciation.…”

“…e Domack et al (2001), Dunbar et al (2002), interpolated age of base of laminated biogenic unit. f Domack et al (1989), based on many cores, corrected for surface ages. g Calibrated calendar year ages are derived through calibration using CALIB 4.2 and 5.0 (Stuiver et al 2005).…”