HR: 1340h
AN: V23C-1563    [Abstracts]
TI: Implications for Mesozoic to Modern Tectonic Deformation in Sub-basins Along the East Gobi Fault Zone, Southern Mongolia
AU: * Heumann, M J
EM: Heumann@earth.utah.edu
AF: Dept. of Geology & Geophisics, University of Utah, 135 S. 1460 E., WBB Room 719, Salt Lake City, UT 84112, United States
AU: Johnson, C L
EM: cari.johnson@utah.edu
AF: Dept. of Geology & Geophisics, University of Utah, 135 S. 1460 E., WBB Room 719, Salt Lake City, UT 84112, United States
AU: Webb, L E
EM: lewebb@syr.edu
AF: Dept. of Earth Sciences, Syracuse University, 204 Heroy Geology Laboratory, Syracuse, NY 13244, United States
AU: Taylor, J P
EM: jtaylo03@syr.edu
AF: Dept. of Earth Sciences, Syracuse University, 204 Heroy Geology Laboratory, Syracuse, NY 13244, United States
AB: This study presents preliminary results of ongoing sedimentary basin analysis for late Mesozoic rift sub-basins (Unegt and Zuunbayan) along the East Gobi Fault Zone (EGFZ), southeastern Mongolia. A better understanding of deformational events recorded in the pre-, syn-, and post-rift sedimentary units of these sub-basins is required to place the Mesozoic and Cenozoic (the focus of this study) histories of the region within the larger context of Central Asian tectonics. Fault generation maps produced from proprietary 2-D seismic reflection surveys, coupled with recent field studies, suggest localized partitioning of deformation throughout the basins with time, often focusing along basin-bounding faults. Reinterpretation of available seismic data highlights areas north (e.g., Har Hotol locality) of the main North Zuunbayan strike-slip fault (the NZB fault), which show a strikingly different deformational character than those south of the NZB fault (e.g., Tavan Har locality). The presence of preexisting thrust-faults in Paleozoic basement blocks beneath the Unegt sub-basin suggests that basement architecture may be the main control in regional Mesozoic-Recent deformation as well as rift basin architecture. For example, the Unegt sub-basin is broad and relatively shallow, while the Zuunbayan is half as wide but considerably deeper along the zones of greatest subsidence. North of the main NZB fault, deformation above the mid-Cretaceous unconformity is apparently focused along a NE-trending, basin-bounding thrust-fault that places Paleozoic basement on top of Upper Cretaceous post-rift strata and potentially Tertiary units.. In contrast, south of the main NZB fault, fault activity above the mid-Cretaceous unconformity is more common and is suggested here to represent the main zone of deformation following Late Cretaceous sediment deposition. Furthermore, Paleozoic basement features may influence and localize continued (modern) deformation along the main axis of the EGFZ. Ongoing deformation in the EGFZ is evidenced by recent fault scarps that cut and deform Upper Cretaceous strata of the Bayanshire Formation, the overlying Tertiary (?) strata, as well as modern alluvium. Recent fault activity was identified in this study at multiple localities along > 200 km of the EGFZ Many of these structures have been correlated to subsurface faults that offset the mid-Cretaceous unconformity in the seismic data. Further study of such young features is crucial for making accurate estimates of total Mesozoic and Cenozoic sinistral off- set along the EGFZ.
DE: 3025 Marine seismics (0935, 7294)
DE: 8000 STRUCTURAL GEOLOGY
DE: 8100 TECTONOPHYSICS
DE: 8169 Sedimentary basin processes
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2007 Fall Meeting