[1] The GPS-derived velocity field (1988)(1989)(1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) for the zone of interaction of the Arabian, African (Nubian, Somalian), and Eurasian plates indicates counterclockwise rotation of a broad area of the Earth's surface including the Arabian plate, adjacent parts of the Zagros and central Iran, Turkey, and the Aegean/Peloponnesus relative to Eurasia at rates in the range of 20-30 mm/yr. This relatively rapid motion occurs within the framework of the slow-moving ($5 mm/yr relative motions) Eurasian, Nubian, and Somalian plates. The circulatory pattern of motion increases in rate toward the Hellenic trench system. We develop an elastic block model to constrain present-day plate motions (relative Euler vectors), regional deformation within the interplate zone, and slip rates for major faults. Substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below $1-2 mm/yr, including central and eastern Anatolia (Turkey), the southwestern Aegean/Peloponnesus, the Lesser Caucasus, and Central Iran. Geodetic slip rates for major block-bounding structures are mostly comparable to geologic rates estimated for the most recent geological period ($3-5 Myr). We find that the convergence of Arabia with Eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the Caucasus and Zagros mountain belts around the periphery of the collision zone. In addition, we find that the principal boundary between the westerly moving Anatolian plate and Arabia (East Anatolian fault) is presently characterized by pure left-lateral strike slip with no fault-normal convergence. This implies that ''extrusion'' is not presently inducing westward motion of Anatolia. On the basis of the observed kinematics, we hypothesize that deformation in the AfricaArabia-Eurasia collision zone is driven in large part by rollback of the subducting African lithosphere beneath the Hellenic and Cyprus trenches aided by slab pull on the southeastern side of the subducting Arabian plate along the Makran subduction zone.

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Surface features of quartz grains on the Al-Haymah and Moushij beaches of the coastal area in the southern Red Sea of Yemen were analyzed by a scanning electron microscope (SEM) to deduce the provenance and depositional environment of sediments. The microtextures on quartz grains were classified into mechanical, chemical, and mechanical/chemical origins. The quartz grains from the two beach areas were rounded to subrounded in shape. Rounded quartz grains with a combination of bulbous and broken edges indicated a recycled provenance. Mechanical features such as V-shaped marks and straight and curved scratches revealed the combination of fluvial and high-energy subaqueous beach environments, whereas aeolian grains are mainly marked by crescentic percussion marks, elongated depressions, and upturned plates. Chemical features such as solution pits, silica globules, trapped diatoms, and adhering particles in quartz grains indicated a diagenetic environment and silica re-precipitation in a coastal environment. In general, the microtextures identified on quartz grains reveal that sediments are influenced by wind, fluvial, and subaqueous marine environments and are derived from nearby and distal sources.