2002 Denver Annual Meeting (October 27-30, 2002)

Paper No. 4
Presentation Time: 8:55 AM


COWGILL, Eric and SIEH, Kerry, Division of Geological and Planetary Sciences, California Institute of Technology, MC 100-23, 1200 E. California Blvd, Pasadena, CA 91125, ecowgill@gps.caltech.edu

Ongoing convergence between the Arabian and Eurasian plates is accommodated by two different structural systems in the western and eastern halves of the Arabia-Eurasia collision. West of 41°E, convergence is absorbed by west-directed extrusion of the Anatolian block along the conjugate North and East Anatolian strike-slip faults. East of ~45°E, shortening is absorbed by the northwest-striking Zagros fold-thrust belt. However, it is not clear what structures link these two systems in the region bordered by the Black Sea, the Greater Caucasus, the Caspian Sean, and the Bitlis Suture. There are three key questions. 1) How do structures along the Bitlis suture in the southern part of the area link with active thrusts in the Greater Caucasus, 600 km to the north? 2) Does the North Anatolian fault link with the Main Recent fault in the Zagros via a northwest-striking zone of right-lateral transpressional deformation? 3) Are the instantaneous kinematics indicated by GPS and earthquake data equivalent to Pliocene-Quaternary deformation? To address these questions we are using ASTER data from the EOS satellite to identify the main structures in this region and find sites where Pliocene-Quaternary slip rates can be determined. ASTER data both provide regional stereo coverage with 15m pixel resolution and are readily available. We identify active structures by mapping geomorphic features such as disturbed drainages, scarps, tilted bedding, and folded or offset fluvial terraces or alluvial fans. Preliminary results from the southern margin of the Greater Caucasus indicate that the active thrust front is located ~40 km to the south of the topographic front. Along the thrust front Quaternary foreland strata of the Alazani basin are deformed by south-directed fault-propagation folds and a north-directed backthrust. An analogous structural style characterizes the northern margin of the Greater Caucasus ~20 km east of Grozny. These observations support a preliminary conclusion that the Greater Caucasus Mountains formed in part by deformation above crustal-scale ramp anticlines. This style is similar to that of the Tian Shan range of northwestern China. Ongoing work will determine how these thrusts link with structures along the Bitlis Suture to the south.