4 Recent Advances in Quaternary Geology and Geomorphology

Sunday, 31 October 2010
8:00 AM - 12:00 PM
Hall E

WERE BOLIDE IMPACTS IN ANTARCTICA RESPONSIBLE FOR THE APPARENT LOSS OF THE WAIS AT THE MID-BRUNHES EVENT/MIS 11 STAGE?

Paper number: 4-8
Program: Technical Sessions
Time: 9:45 AM – 10:00 AM

Authors

Abstract

Three different groups recently reported a significant meteoritic event in Antarctica ca.481-434 kyr. Two reports arose from 2 deep ice cores, Core Fuji and Dome C Core, in which were found dust layers of extraterrestrial material ≈ 100,000 times above normal. Distance between the cores is several thousand kilometers. The third group reports a significant occurrence of ablation debris in the Transantarctic Mountains indistinguishable from the anomalous extraterrestrial particles in the cores and of the same age. The distance between this area and the cores is ≈ 3000km. These authors conclude the ablation debris is paired with the ca. 481 kyr old material found at Dome C and Dome Fuji, the spread in distances calling for meteorite impacts of significant size. These discoveries corroborate earlier and more recent geophysical inferences that Antarctica may have been subjected to multiple impacts. The earlier (1960s) inference arose from a gravity profile over Wilkes Land that was characteristic of known impact sites. Later geophysical surveys show a dominant cluster of negative free air gravity anomalies all across Antarctica: the continental-oceanic boundary, the Transantarctic Mountains, the Ross Embayment. This required modifying the earlier suggestion of one impact to that of multiple impacts, supported by craterform features inferred from radiosounding, aeromagnetics, etc. Additional support arises from sea floor cores just off Antarctica and elsewhere.

The timing, 481ky, is at the mid-Brunhes event, the onset of MIS 11 which replaced a heavy glacial with a sudden unusually long, warm interglacial interval, NOT associated with an early CO2 peak. MIS 11 has been characterized by overall warm seasurface temperatures in high Southern latitudes (not the northern latitudes), strong thermohaline circulation, major disruption in biota and a major marine transgression (sea levels > 20m above present). A number of workers call for the sudden collapse of a major ice sheet, i.e., WAIS, to explain the unusual characteristics of MIS 11 which apparently cannot be attributed to Milankovitch mechanisms. A possible initiator, then, of MIS11 is the disruption and dislodgement of the Antarctic Ice Sheets by major bolide impacts. The potential risk to humanity of bolide impacts in Antarctica is a call for more research on the issue.