HR: 1340h
AN: T43A-1085    [Abstracts]
TI: Coseismic growth of sedimentary basins along the Yammouneh strike-slip fault (Lebanon)
AU: Nemer, T
EM: nemert@missouri.edu
AF: Department of Geological Sciences, 101 Geology Building University of Missouri, Columbia, MO 65211, United States
AU: * Gomez, F
EM: fgomez@missouri.edu
AF: Department of Geological Sciences, 101 Geology Building University of Missouri, Columbia, MO 65211, United States
AU: Al Haddad, S
EM: sharbel.alhaddad@gmail.com
AF: Department of Geology, American University of Beirut, Beirut, 00000, Lebanon
AU: Tabet, C
EM: ctabet@cnrs.edu.lb
AF: LNCSR, Lebanese National Council for Scientific Research, Beirut, 00000, Lebanon
AB: The left-lateral Yammouneh fault is the main active branch of the Dead Sea Fault System (DSFS) within the Lebanese restraining bend. Despite the overall transpressional setting, a series of sedimentary basins have developed along the trace of the Yammouneh fault. Consequently, paleoseismic studies within these basins provide an opportunity to study the processes of co-seismic growth of the basins, as well as elucidate earthquake behaviour of the fault, in general. The active fault trace along a 51-km length of the Yammouneh fault was delineated as relatively young surface ruptures and fault scarps that affect Holocene deposits, with intermittent offset geomorphic markers. A detailed field investigation focused on the rhombohedral Yammouneh basin, an actively evolving example of pull-apart basins that is obliquely cut by the active fault. Three-dimensional correlation and analysis of palaeoseismic investigations exposed a composite shear zone with a total subsidence that exceeds 2 m over the past approximately 7300 years. Stratigraphic and geochronological constraints suggest the occurrences of at least four large seismic events during that period, with the last event being coeval with 240-441 AD. Our results suggest a subsidence rate due to faulting of about 0.15 mm/yr within the Yammouneh pull-apart basin and a total throw across the Yammouneh fault of about 200 m across the basin. Comparing the present-day slip rate and the size of the Yammouneh basin suggests an apparently young age for of 1.0 – 1.6 Myr. A palinspastic reconstruction suggests that the pull-apart opening of the Yammouneh basin may have been followed by a possible 10 degree -clockwise rotation that could have had a major role on the basin's subsequent evolution in terms of localized extension, confined compression, change in the stress field, and fault migration. These results permit revisiting competing conceptual models for development of strike-slip pull-apart basins.
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8002 Continental neotectonics (8107)
DE: 8036 Paleoseismology (7221)
DE: 8111 Continental tectonics: strike-slip and transform
SC: Tectonophysics [T]
MN: 2007 Fall Meeting