Eastern margin of the Ross Sea Rift in western Marie Byrd Land, Antarctica: Crustal structure and tectonic development

摘要: [1] The basement rock and structures of the Ross Sea rift are exposed in coastal western Marie Byrd Land (wMBL), West Antarctica. Thinned, extended continental crust forms wMBL eastern shelf, where faults control regional basin-and range-type topography at ∼20 km spacing. Onshore Ford Ranges Rockefeller Mountains wMBL, rocks consist Early Paleozoic metagreywacke migmatized equivalents, intruded by Devonian-Carboniferous Cretaceous granitoids. Marine geophysical profiles suggest that these geological formations continue offshore to west beneath Sea, covered glacial marine sediments. Airborne gravity radar soundings over indicate a thicker smoother inland north east northern Ranges. A migmatite complex near this transition, exhumed from mid crustal depths between 100–94 Ma, suggests profound discontinuity inboard limit crust, ∼300 northeast margin. Near limit, aeromagnetic mapping reveals an extensive region high amplitude anomalies ranges can be interpreted as sub ice volcanic province. Modeling data is 8–9 thinner than interior MBL (β = 1.35). Gravity modeling also outlines regions low-density (2300–2500 kg m−3) buried lighter surface. These bounded throughgoing east-west with vertical separation. possibly facies metagreywacke, or epizonal granites, felsic known moraines. features on land preserve record middle Late development rift. Thermochronology stratigraphy margin formed most extension occurred mid- time, before seafloor spreading initiated Campbell Plateau. The tectonic contrasts Transantarctic form margin, significant rift-flank relief developed Tertiary time.