* Astronomy

Title: Origin of the Timor Sea Late Eocene-Pre-Miocene Strewn Crater Field
Authors: J.D. Gorter and A.Y. Glikson

Since the majority of extraterrestrial impacts impinge on oceanic regimes, the identification of buried submarine impact structures from geophysical data, including 3D reflection seismic profiles, constitutes an essential step in unravelling the terrestrial impact record.
However, the method suffers from severe difficulties inherent in the limitations on the amount of drilling and thus the on tests of candidate geophysical features and potential impact structures.
In the Timor Sea, north Bonaparte Gulf, Deep sea drilling and seismic reflection data encounter an at least 350 m-thick PGE-rich radioactive carbonate breccia lens at Fohn-1 exploration well (Gorter and Glikson, 2000).
The data are interpreted in terms of a buried 4.8 km-diameter impact crater of late Eocene to pre-Miocene age. The crater displays the classic elements of impact structures, including a central uplift and ring syncline. The presence in the breccia of redeposited Campanian and Maastrichtian microfossils suggests rebound of strata from levels deeper than 1250 m below the pre-Langhian unconformity. Morphometric modelling suggests an original transient crater depth at least 1400 m deep, consistent with the excavation of Cretaceous strata. Stratigraphic and palaeontological evidence suggests that the impact occurred between 38 and 24 Ma. The breccia contains altered glass components enriched in the inert platinum group elements (PGE) (Ir, Ru) by factors of 5-12 above the values of common sediments. The more mobile PGE (Os, Pt, Pd) show a wide scatter and terrestrial-type values.

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North Bonaparte Basin

Latitude:  12°15'21.49"S, Longitude:  128°32'1.33"E