Architecture of a Holocene Carbonate Beach-Bar Complex: Jabal Fuwairit, Northeast Qatar
Poppelreiter, Michael C.*1
(1) Shell Kuwait E&P, Shell, Kuwait City, Kuwait.
Qatar’s coasts are famous natural laboratories for carbonate research, especially for carbonate coastal spits. These thin, elongated bodies developed from the Holocene onwards along Qatar’s coast. One of these costal spits forms a superbly exposed cliff, the so-called Jabal Fuwairit, which is of Holocene age. This study provides insights in the architecture of the jabal as an example for such rather unusual carbonate depositional bodies. The jabal was logged; layer boundaries were walked out and sedimentological features were described. Initial results show that Jabal Fuwairit is made up of highly porous lime grainstone. Measured porosity ranges from 13-28%; permeability amounts to tens of milidarcy. The jabal consists of three major stratigraphic units. (1) The bottom layer, 10-100 cm thick, is a brick-red, cemented breccia. It is interpreted as gravel beach deposit. (2) Several bioturbated-stromatolitic pack- to grainstone layers extend above, 30-50 cm thick each. They are considered as lagoonal deposits. They are intercalated with, and vertically pass into low-angle cross-bedded grainstone. Layer (2) is interpreted as marine beach bar complex. These bars are intersected by erosive surfaces, 2-10 m wide and 30-80 cm thick filled with planar cross-bedded grainstone. These are interpreted as spill-over channels. (3) The upper layer consists of trough-cross-bedded grainstone, showing pin-stripe bedding. This layer is interpreted as a wind-blown dune deposit. Comparison to modern deposits along the Qatar coast shows many similarities to coastal spits. The sediment bodies stretch parallel to the coastline, oblique to the prevailing wind direction and behind a morphological extension of the coast. The jabal shows an elongated, thin morphology with a length-to-width ratio of > 1:10 at any given geographic position. Its tail end splits into three sub-parallel branches. These shows a characteristic landward deflection (hook shape) as is typical for spits. Thus Jabal Fuwairit is interpreted as a Holocene coastal spit. This paper provides an account of its 3-D architecture, thus providing insight into Qatar’s climatic and depositional history.
AAPG Search and Discovery Article #90141©2012, GEO-2012, 10th Middle East Geosciences Conference and Exhibition, 4-7 March 2012, Manama, Bahrain