From Newsgroup: sci.bio.paleontology

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2008GC002149


Abstract

[1] New details on the east Antarctic gravity field from the Gravity
Recovery and Climate Experiment (GRACE) mission reveal a prominent
positive free-air gravity anomaly over a roughly 500-km diameter
subglacial basin centered on (70-#S, 120-#E) in north central Wilkes Land. This regional inverse correlation between topography and gravity is quantitatively consistent with thinned crust from a giant meteorite
impact underlain by an isostatically disturbed mantle plug. The inferred impact crater is nearly three times the size of the Chicxulub crater and presumably formed before the Cretaceous formation of the east Antarctic
coast that cuts the projected ring faults. It extensively thinned and disrupted the Wilkes Land crust where the Kerguelen hot spot and
Gondwana rifting developed but left the adjacent Australian block
relatively undisturbed. The micrometeorite and fossil evidence suggests
that the impact may have occurred at the beginning of the greatest
extinction of life on Earth at re+260 Ma when the Siberian Traps were effectively antipodal to it. Antipodal volcanism is common to large
impact craters of the Moon and Mars and may also account for the
antipodal relationships of essentially half of the Earth's large igneous provinces and hot spots. Thus, the impact may have triggered the rCLGreat DyingrCY at the end of the Permian and contributed to the development of
the hot spot that produced the Siberian Traps and now may underlie
Iceland. The glacial ice up to a few kilometers thick that has covered
the crater for the past 30rCo40 Ma poses formidable difficulties to
sampling the subglacial geology. Thus, the most expedient and viable
test of the prospective crater is to survey it for relevant airborne
gravity and magnetic anomalies.

....

3. Discussion

[23] Our analysis suggests that the terrain and GRACE gravity data can
be explained by the crustal effects of a giant impact in Wilkes Land. Unfortunately, the geological details of the inferred impact site are completely masked by a few kilometers of overlying glacial ice. However, possible impact evidence has been reported from the Permian-Triassic
boundary beds at Graphite Peak in the central Transantarctic Mountains
(TAM). This evidence includes small chondritic meteorite fragments [Basu
et al., 2003], fullerenes with extraterrestrial noble gas abundances and isotope ratios [Poreda and Becker, 2003], and a faint iridium anomaly [Retallack et al., 1998]. The strength of this evidence has been debated [e.g., Collinson et al., 2006] and obviously limited by the apparent
absence of a source crater. However, the putative crater clearly may be
a source of the Graphite Peak data and thus may yield new insights on a possible late Permian impact origin for the great mass extinction. In
view of its potential geological significance, we investigate below
additional constraints on the possible crustal properties and evolution
of the inferred Wilkes Land impact.
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