Tuesday, 28 August 2007
2.PS-34
Denudation and uplift of the Mawson Escarpment (eastern Lambert Graben, Antarctica) as indicated by apatite fission track data and geomorphological observation
Frank Lisker, FB 5 - Dept. of Earth Sciences, University of Bremen, PF 330440, Bremen, Germany, Helen Gibson, The Loop Geologic, 33 Bamfield Street, Sandringham, VIC 3191, Australia, Christopher J.L. Wilson, School of Earth Sciences, The University of Melbourne, VIC 3010, Australia, and Andreas Laeufer, Referat Polargeologie, Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover, Germany.
Analysis of three vertical profiles from the southern Mawson Escarpment (Lambert Graben,) reveals apatite fission track (AFT) ages ranging from 102±20 to 287±23 Ma and mean lengths of 12.2 to 13.0 µm. Quantitative thermal histories derived from these data consistently indicate onset of slow cooling below 110°C began sometime prior to 300 Ma, and a second stage of rapid cooling from paleotemperatures up to ≤100°C to surface temperatures occurred in the Late Cretaceous – Paleocene. The first cooling phase refers to Carboniferous – Jurassic basement denudation up to up to 5 km associated with the initial rifting of the Lambert Graben. The presence of the ancient East Antarctic Erosion Surface and rapid Late Cretaceous – Paleocene cooling request a second denudational episode during which up to 4.5 km of sedimentary cover rocks were removed, and that is likely linked to the Cretaceous Gondwana breakup between Antarctica and India.