HR: 15:25h
AN: T53E-08    [Abstracts]
TI: A Model for Cretaceous and Tertiary Extension of the Ross Sea, Antarctica.
AU: * Decesari, R C
EM: rdecesari@umail.ucsb.edu
AF: Department of Earth Sciences, University of California, Santa Barbara, Ca 93106 United States
AU: * Decesari, R C
EM: rdecesari@umail.ucsb.edu
AF: Institute for Crustal Studies, University of California, Santa Barbara, Ca 93106 United States
AU: Wilson, D S
EM: dwilson@geol.ucsb.edu
AF: Department of Earth Sciences, University of California, Santa Barbara, Ca 93106 United States
AU: Wilson, D S
EM: dwilson@geol.ucsb.edu
AF: Institute for Crustal Studies, University of California, Santa Barbara, Ca 93106 United States
AU: Faulkner, M
EM: Michael.Faulkner@shell.com
AF: Shell International Exploration and Production B.V., Kesslerpark 1, Rijswijk (ZH), 2288 GS Netherlands
AU: Luyendyk, B P
EM: luyendyk@geol.ucsb.edu
AF: Department of Earth Sciences, University of California, Santa Barbara, Ca 93106 United States
AU: Luyendyk, B P
EM: luyendyk@geol.ucsb.edu
AF: Institute for Crustal Studies, University of California, Santa Barbara, Ca 93106 United States
AU: Sorlien, C C
EM: chris@crustal.ucsb.edu
AF: Institute for Crustal Studies, University of California, Santa Barbara, Ca 93106 United States
AB: The timing and magnitude of Ross Sea extension has remained largely problematic. Outstanding questions include, did Tertiary extension of the Victoria Land Basin (VLB) affect the Central and Eastern Basins, why is there so much Oligocene RSS-2 in the Ross Sea basins, and what accounts for the necessary accommodation space? We computed a 1-D backstripped subsidence model for the Central Trough and Eastern Basin to infer periods of extension. Unit thicknesses were obtained from interpreted MCS depth sections in the deepest part of the basins for the analysis. Stratigraphic units were decompacted and tectonic subsidence calculated. Estimated corrections for paleobathymetry and eustatic sea level changes were applied. Our results support two extensional episodes throughout the Ross Sea, a Cretaceous episode and an early Tertiary episode. Cretaceous extension occurred at a stretching factor of ~2 and Tertiary extension occurred at ~1.5 to 2 in the Central Trough and portions of the Eastern Basin at this time. Tertiary stretching factors in the VLB were 2 to 3. All extension was completed by the first deposition of RSS-2 above unconformity RSU6 (~30 Ma). If Oligocene strata were deposited during extension, syn-rift characteristics are expected. However, these strata are not faulted or deformed in the central and eastern Ross Sea. Tertiary extension was likely simultaneous with seafloor spreading along the Eocene Adare Trough (43-26 Ma) northwest of the Ross Sea. Approximately 180 km of east-west extension due to this spreading could have extended Ross Sea basins. The VLB is 130 to 150 km wide, requiring that remaining Adare Trough extension is accommodated elsewhere, possibly in the Central Trough and the Eastern Basin. An alternative model with only Cretaceous extension east of the VLB, limiting Tertiary extension only to the VLB [Karner et al, 2005 EPSL], requires that most thermal subsidence throughout the Ross Sea predates Oligocene sedimentation. This timing requires that Oligocene unconformity RSU6 formed many of hundreds of meters below sea level, implying that RSU6 is not a wave-cut feature and that other processes, such as glaciation or sea level changes, formed the unconformity. We intend to expand our 1-D model into a 2-D model and apply decompaction corrections and subsidence calculations to a grid of the Ross Sea in order to determine how all the basins respond in 2-D.
DE: 8105 Continental margins: divergent (1212, 8124)
DE: 8109 Continental tectonics: extensional (0905)
DE: 8175 Tectonics and landscape evolution
SC: Tectonophysics [T]
MN: Fall Meeting 2005