HR: 1330h
AN: T12A-0447    [PDF]
TI: Tectonic evolution of the Coulman High and Central Trough along the Ross Ice Shelf, Southwestern Ross Sea, Antarctica
AU: * Decesari, R C
EM: rdecesari@umail.ucsb.edu
AF: Dept. of Geological Sciences, 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
AU: Luyendyk, B P
EM: luyendyk@geol.ucsb.edu
AF: Dept. of Geological Sciences, University of California, Santa Barbara, Ca 93106 United States
AU: Bartek, L R
EM: bartek@email.unc.edu
AF: Dept. of Geological Sciences, University of North Carolina, Chapel Hill, NC 27599
AU: Diebold, J B
EM: johnd@ldeo.columbia.edu
AF: Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964 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
AB: In Cretaceous time, rifting of the New Zealand subcontinents from the Ross Sea Sector of Antarctica resulted in the formation of passive margins and widespread extension throughout the Ross Sea Embayment. This rifting event is thought to have produced widespread basin and range topography throughout the Ross Sea. More specifically, Cretaceous extension has been interpreted with confidence in the Eastern Basin of the Ross Sea but not in the western Ross Sea. In January of 2003, new geophysical data were collected on board RVIB Nathaniel B. Palmer cruise NBP03-01 along the Ross Ice Shelf front, Antarctica. The primary goal was to collect detailed grids of seismic data to select potential drill sites to further understand the glacial and tectonic history of the Ross Embayment. The survey sites were located in regions where large sections of the ice shelf have recently broken off, thus exposing previously covered and unexplored seafloor. Because the ice shelf is advancing at ~1 km/yr, drilling from the ice shelf into the survey area will be possible in 2 to 3 years. The C-19 survey site in the western Ross Sea was uncovered by the breaking off of the C-19 iceberg in March of 2002, and includes approximately 3600 km2. It spans from the Victoria Land Basin (VLB) immediately west of the survey site to the Coulman High, over the Central Trough and west onto the Central High. The multichannel seismic reflection data have been processed, for attenuation of multiples. The resulting stacks have been loaded and interpreted in 3D interactive software. The data collected from the survey site shows well-defined N-S trending normal separation faults. Regional correlation along several different paths from coreholes near Cape Roberts in the western Victoria Land Basin, have been made to the C-19 survey site. Although this correlation crosses many faults, it suggests that a ~23 Ma horizon is within a few hundred meters of the seafloor at the C-19 survey area. We interpret two unconformities below the ~23 Ma horizon. The first unconformity overlies gently tilted and faulted strata, which we interpret as early Oligocene in age. The second and deeper unconformity overlies tilted and highly disrupted or discontinuous strata, which we interpret as Cretaceous syn-rift deposits. Given the fact that we have correlated a Miocene horizon to the survey site, our interpretation of Cretaceous syn-rift strata and early to mid Cenozoic extension is permissible. Similar interpretations have been made in the Eastern Basin of the Ross Sea and are widely accepted. We propose these interpretations are not unique to either the Eastern Basin or the C-19 region. We suggest that highly disrupted Cretaceous syn-rift deposits overlain by gently tilted and faulted strata are characteristic of and occur across the entire Ross Sea.
DE: 1744 Tectonophysics
SC: Tectonophysics [T]
MN: 2003 Fall Meeting