Burial and exhumation of the Eisenhower Range, Transantarctic Mountains, based on thermochronological, sedimentary rock maturity and petrographic constraints

Abstract

The Eisenhower Range is a N–S trending mountain range in the Transantarctic Mountains (TAM) adjacent to the NW Ross Sea Embayment. New AFT and apatite (U–Th–Sm)/He (AHe) data from vertical basement profiles supplemented by paleotemperature and pressure estimates derived from Beacon sandstones provide new quantitative results on regional burial evolution and first regional constraints on basin inversion and exhumation processes. AFT ages between 32±2 and 259±18Ma and AHe ages of 37±3–173±16Ma correlate positively with sample elevations. Thermal history modeling of these data and complementary thermal indications detect heating of the paleosurface on the Eisenhower Range to temperatures ≥80°C subsequent to Ferrar magmatism, and constrain Late Eocene rapid cooling. Regression of modeled paleotemperatures against sample elevations refers to a high Jurassic (~45°C/km) and a moderate Cretaceous–Eocene (28±8°C/km) geothermal gradient. The texture of Beacon sandstones supports strong mechanical compaction that requires a higher overburden than preserved in the stratigraphic record. Modeled paleotemperatures and pressures suggest basement burial that increases from Late Jurassic (0.7–1.1km) to Eocene (1.8–2.1km). The overburden comprises 0.7–1.1km cumulative Beacon/Ferrar rocks and 0.7–1.4km of post-Ferrar sediments. Rapid cooling of the whole sample suite between ~35 and 30Ma implies fast erosion of the post-Ferrar sediments and (re-) exposure of underlying magmatic rocks. Subsequent differential sample cooling to present-day surface temperature infers ongoing exhumation by glacial incision enhanced by isostatic response to basin inversion. Decreasing amounts of exhumation from the coast (>3km) toward the interior (1.5–2.2km) point to backstepping incision along the fault controlled Priestley Glacier. Substantial exhumation of the Eisenhower Range since the Late Eocene is hence triggered by both tectonic and climatic factors, superimposed by considerable lithological influence during the initial exhumation stage.