Collaborative Research: Neotectonic Structure of Terror Rift, Western Ross Sea

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This award, provided by the Antarctic Geology and Geophysics Program of the Office of Polar Programs, provides funds for a study to investigate the tectonic development of the southwestern Ross Sea region. Displacements between East and West Antarctica have long been proposed based on global plate circuits, apparent hot spot motions, interpretations of seafloor magnetic anomalies, paleomagnetism, and on geologic grounds. Such motions require plate boundaries crossing Antarctica, yet these boundaries have never been explicitly defined. This project will attempt to delineate the late Cenozoic - active boundary between East and West Antarctica along the Terror Rift in the western Ross Sea, where young structures have been identified, continuity between active extension and intracontinental structures can be established, and where accessibility via ship will allow new key data sets to be acquired. We will use multi-source marine and airborne geophysical data to map the fault patterns and volcanic structure along the eastern margin of the Terror Rift. The orientations of volcanic fissures and seamount alignments on the seafloor will be mapped using multibeam bathymetry. The volcanic alignments will show the regional extension or shear directions across the Terror Rift and the orientations of associated crustal stresses. Swath bathymetry and single channel seismic data will be used to document neotectonic fault patterns and the eastern limit of recent faulting. Delineation of neotectonic fault patterns will demonstrate whether the eastern margin of the Terror Rift forms a continuous boundary and whether the rift itself can be linked with postulated strike-slip faults in the northwestern Ross Sea. Seafloor findings from this project will be combined with fault kinematic and stress field determinations from the surrounding volcanic islands and the Transantarctic Mountains. The integrated results will test the propositions that the eastern boundary of the Terror Rift forms the limit of the major, late Cenozoic -active structures through the Ross Sea and that Terror Rift kinematics involve dextral transtension linked to the right-lateral strike-slip faulting to the north. These results will help constrain the kinematic and dynamic links between the West Antarctic rift system and Southern Ocean structures and any related motions between East and West Antarctica. In the first year, a collaborative structural analysis of existing multichannel and single channel seismic profiles and aeromagnetic data over the Terror Rift will be conducted. The location of volcanic vents or fissures and any fault scarps on the sea floor will be identified and a preliminary interpretation of the age and kinematics of deformation in the Terror Rift will be produced. Late in the second year, a one-month cruise on RVIB N.B. Palmer will carry out multibeam bathymetric and sidescan sonar mapping of selected portions of the seafloor of Terror Rift. Gravity, magnetics, seismic reflection and Bathy2000 3.5 kHz sub-bottom profile data will also be collected across the rift. In the third year, we will use these multisource data to map the orientations and forms of volcanic bodies and the extent and geometry of neotectonic faulting associated with the Terror Rift. The project will: 1) complete a map of neotectonic faults and volcanic structures in the Terror Rift; 2) interpret the structural pattern to derive the motions and stresses associated with development of the rift; 3) compare Terror Rift structures with faults and lineaments mapped in the Transantarctic Mountains to improve age constraints on the structures; and 4) integrate the late Cenozoic structural interpretations from the western Ross Sea with Southern Ocean plate boundary kinematics.