Crustal structure and rift flank uplift of the Adare Trough, Antarctica

摘要: The Adare Trough, located 100 km northeast of Cape Adare, Antarctica, represents the extinct third arm a Tertiary spreading ridge between East and West Antarctica. It is characterized by pronounced asymmetric rift flanks elevated up to over 2 above trough's basement, accompanied large positive mantle Bouguer anomaly. On basis recently acquired seismic reflection ship gravity data, we invert anomalies from Trough obtain an unexpectedly oceanic crustal thickness maximum 9–10.5 underneath ridge. A regional residual basement depth anomaly 1 2.5 in amplitude characterizes ocean crust offshore Victoria Land Balleny Islands north Iselin Bank. observations models indicate that mid/late episode slow Antarctica was associated with thermal increasing toward indicates this may have increased through time during episode. This scenario supported convection model, which formation strengthening major negative upper density southwest Pacific last 50 million years. total amount post-26 Ma extension normal faulting about 7.5 km, anomalously thick lithospheric effective elastic (EET) 3.5 5 km. corresponds age 3 years based on boundary layer model supports formed soon after ceased, confined relatively weak lithosphere crust. There little evidence for subsequent structural activity trough area available indicating part Antarctic Rift system became largely inactive early Miocene, exception minor reactivation visible data as offsets end Pliocene.