| Summary: | The denudational history along a transect across the western margin of the Lambert Graben, northern Prince Charles Mountains, East Antarctica, is quantified on the basis of thermal history modeling of apatite fission track data from four vertical profiles. Early Cretaceous paleogeothermal gradients estimated from the fission track data increase from ∼19°C km−1 ∼50 km west of the rift margin to ∼29°C km−1 within the immediate vicinity of the western master fault. Two discrete phases of enhanced denudation during the Phanerozoic are inferred for the western rift margin. The first occurred during the early Paleozoic, with minimum denudation of between 1.6 and 5.0 km, which is broadly coeval with initial rifting and the major period of Permo-Triassic sedimentation within the Lambert Graben. The formation of the graben was related to the formation of the ancestral Gamburtsev Mountains due to Variscan compression and substantial crustal thickening of the East Antarctic Craton. The second phase of denudation commenced in the Early Cretaceous, with estimated amounts ranging between 1.0 and 4.5 km, generally increasing toward the rift margin, with the maximum total denudation occurring ∼20 km west of the western master fault of the graben. The Early Cretaceous phase of denudation was probably related to tectonic reactivation of the earlier Permo-Triassic rift during the initial separation of the Indian and Antarctic sector of Gondwana.
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