Kinematic modelling of the West Antarctic Rift System, Ross Sea, Antarctica

In this study, we investigate the thermo-mechanical controls on the formati on of the Ross Sea basin (Antarctica) and the uplift of the adjacent Transa ntarctic Mountains (TAM) rift shoulder, which started in the Late Cretaceou s and continued until the present time. Quantitative forward modelling has been performed along three 700 to 800 h-m long East-West offshore profiles, extended inland to the front of the TAM. The modelling is constrained by a n extensive database of multichannel seismic (MCS), refraction seismic, Oce an Bottom Seismographs (OBS), and gravity data. MCS data is tied to well st ratigraphy from DSDP leg 28, CIROS-1 and MSTSS-1. Quantitative estimates of uplift of the TAM are provided by previous work on apatite fission track a nalysis. We incorporate the finite strength of the lithosphere in basin formation mo dels using the concept of the level of necking. Lateral variations of necki ng level and associated bulk rheological properties (with necking levels ra nging from 15 km in the northernmost, to 20 km in the central and 23 km to the southernmost profiles) are required to explain the observed crustal geo metries. High values of effective elastic thickness (more than 30 km) and p re-rift lithospheric thicknesses (220-230 km), indicating a cold lithospher e in a pre-rift cratonic setting, are consistent with elevation of the rift shoulder. The western ports of the profiles appear to have unusually high stretching values without the development of oceanic crust. Inferred average values of stretching factors vary from 2.3 to 2.8, equivalent with extension in the Ross Sea of 115% to 140%. The modelling result for the uplift of the TAM pr edicts a late Cretaceous tectonic uplift of about 1.5 to 2.0 km, and a Ceno zoic uplift of about 1.3 km restricted to southern Victoria Land. (C) 1999 Elsevier Science B.V. All rights reserved.