HR: 1340h
AN: H43D-0528    [Abstracts]
TI: Insight on watershed development along the actively uplifting Mount Lebanon range (Lebanon) from marine and fluvial terraces
AU: * Lepley, S
EM: swlyqf@mizzou.edu
AF: Dept. Geological Sciences, 101 Geology Bldg. University of Missouri, Columbia, MO 65211 United States
AU: Gomez, F
EM: fgomez@missouri.edu
AF: Dept. Geological Sciences, 101 Geology Bldg. University of Missouri, Columbia, MO 65211 United States
AU: Nader, F
EM: fadi.nader@aub.edu.lb
AF: Dept. of Geology, American University of Beirut, Beirut, 00000 Lebanon
AB: Active uplift in the Mt. Lebanon range results from regional transpression along a ~200-km-long restraining bend within the Dead Sea fault system. Thus, the resultant landscape is characterized by the combined influences of tectonic, eustatic, and climatic controls. Marine terraces in northern Mt. Lebanon range provide significant constraints on regional uplift and, consequently, base level control on watershed development. Detailed geologic mapping reveals at least six coastal terrace levels between the cities of Tripoli and Batroun in northern Lebanon, ranging in elevation from 5 m to 113 m above sea level. The marine terraces are primarily abrasional platforms with little to no sediment cover. However, at certain locations, the terraces comprise of a thick (up to 20 m towards the coast) sedimentary cover that are the result of episodic periods of cut and fill into older Pliocene deposits. The majority of these sediments are well-rounded, cobble-size clasts of limestone cemented by a calcite matrix with occasional clasts of basalt and marine fossils. Travertine formations, fossil remnants, and limestone clasts are available to constrain ages on terrace formations and, in turn, coastal uplift rates. Correlation of terrace heights with Pleistocene sea level variations suggests an average, regional uplift rate of 0.3 m/ka. Fluvial terraces in the northern Mt. Lebanon allow reconstruction of longitudinal profiles that grade into base levels represented by the corresponding marine terraces. Hence, this correlation constrains the ages of fluvial terraces and consequently permits estimates of fluvial erosion. Temporal variations in fluvial transport capacity are suggested by episodic aggradation of massive boulder-size clasts of basalt and dolomite that originate over 20 km upstream. Furthermore, knickpoints in the present-day drainage also appear to correlate with the former base levels. Hence, the retreat of these knickpoints permits assessing the lag time in the response of the fluvial system to base level changes.
DE: 1815 Erosion
DE: 1824 Geomorphology: general (1625)
DE: 1825 Geomorphology: fluvial (1625)
DE: 1879 Watershed
SC: Hydrology [H]
MN: Fall Meeting 2005