Late Pleistocene-Holocene Evolution Of Faulting In The Sea Of Marmara Pull-Apart (North Anatolian Fault)
Abstract
The Sea of Marmara is a crustal-scale pull-apart basin that formed by the transtensional step-over of the North Anatolian fault (NAF) in the west. Smaller fault steps bound three deep basins (Cinarcik, Central and Tekirdag basins from east to west) which alternate within the larger the Sea of Marmara pull-apart combining strike-slip and normal faulting. Clear morphologic evidence of recent faulting activity was found along several submarine segments of the NAF during the MARMARASCARPS cruise in 2002. To characterize the Quaternary evolution of faulting in the deep basins, and to study the geometry of these scarps we incorporate several high resolution marine data from this cruise together with complementary data from other Marmara cruises. The sediment fill in the basins record the evolution of the activity of the normal faults. Sedimentation rates and vertical components of slip are estimated and discussed from 3.5 kHz chirp profiles which are correlated with deep seismic reflection profiles. Combined high-resolution bathymetry (30 m-resolution, 1 m vertical accuracy) and ultra-high resolution microbathymetry data (0.5 m-resolution, 0.1 m vertical accuracy) reveal well-preserved sea-floor ruptures associated with recent large earthquakes (1912 Ganos Ms 7.4; 1963 Cinarcik Ms 6.4 and 1999 Izmit Mw 7.4). The submarine fault scarps have different proportion of strike-slip and normal faulting, consistent with the pull-apart structure. The nested morphology of normal faults at the edges of the pull-apart structure contains evidence for cumulative scarps that result from vertical slip associated with many earthquakes. They must be accounted for by vertical motion across faults with large normal component. The stratigraphy of the larger scarps is determined with 3.5 kHz seismic profiles and 14C dated cores, which document precisely their evolution during the last 20 kyr. Their morphology results from accumulation of slip under competing tectonic, erosion and sedimentation processes which subject to climatic change. They appear to have emerged progressively after the occurrence of catastrophic sedimentary events associated with the late Pleistocene-Holocene deglaciation. Sedimentation rates are fast (1-3mm/yr), but they do not keep up with even faster fault rates and associated subsidence that create the 1200-m-deep bathymetric troughs in the Sea of Marmara. The normal faulting throw rates are particularly fast (up to 6mm/yr) at pull-apart margins. These rates are consistent with the high rates of strike slip and pull-apart extension deduced for the north Marmara fault system at a larger scale. The total structural relief in Marmara appears to have formed under uniform tectonic and morphological processes over the last 3 to 6 Myrs.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFM.T13C1883U
- Keywords:
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- 3045 MARINE GEOLOGY AND GEOPHYSICS / Seafloor morphology;
- geology;
- and geophysics;
- 8175 TECTONOPHYSICS / Tectonics and landscape evolution