Offshore Wind-Dominated Shoreline Progradation in an Arid Environment: Examples from the Leeward Shoreline of Qatar (Khor Al-Adaid Area)
Strohmenger, Christian J.; Jameson, Jeremy
The southeastern, leeward coast of Qatar presents a unique example of arid shoreline sedimentation patterns dominated by sand dune fields blown into the sea. The observed sediment dynamics, geospatial data, and facies patterns are analogous to aeolian reservoir systems in ancient rocks, like the Permo-Carboniferous Unayzah Formation of the Middle East or the Permian Rotliegend Formation of Northwest Europe.
Oldest sediments exposed along the coastal plain are relicts of a Holocene sea-level highstand of approximately 2 to 4 meters above present day sea level. Erosional remnants of Holocene carbonate beaches and lagoons can be found up to 15km inland of the Qatar coastline. Unlike most coastal depositional systems, the 50km long southeast coastline at Khor Al-Adaid is sourced from onshore aeolian sand dune fields. Typically 5 to 10 meter high barchan and seif dunes predominate, reaching a maximum height of approximately 60m. The coast has prograded 5 to 15 kilometer during the Holocene.
In spite of their height and size, dunes are an ephemeral feature of the landscape. Most dune sand blows across the sabkha, building the coastline seaward. Only 1 to 2 meters of a dune are preserved on the wet portions of the sabkha environment (standing water, interdune ponds). Lightly cemented erosional remnants of dune toesets are composed of unidirectional cross-bedded, tabular foresets with flat tops. They extend up to several kilometers, passing laterally in parallel and wavy laminated gypsum cemented sand.
Khor Al-Adaid also consists of large shallow mesosaline lagoons with ebb and flood tidal-deltas, rimmed on their protected sides by kilometer-wide stromatolite flats. Lagoons consist of burrowed sands and seagrass.
Khor Al-Adaid sedimentation patterns reflect the interplay between sea level, physical and chemical depositional processes, and aeolian deflation. Giant sand dunes, the most obvious feature of the landscape, are migrating into the shallow lagoons and the sea, resulting in an intercalation of dune, intertidal, and lagoon facies along a coast with narrow or absent beaches. Understanding the interplay between these factors provides the basis for building more realistic geological models.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013