The Vertical Sabkha Sequence at Mussafah Channel, Abu Dhabi, United Arab Emirates

Christian J. Strohmenger¹*, Abdulla Al-Mansoori¹, Omar Al-Jeelani¹, Ali Al-Shamry¹, Ismail Al-Hosani¹, Hesham Shebl², and Khalil Al-Mehsin^3
1ADCO
²ZADCO
³ADNOC
*[email protected]

Studies of recent sediments can add greatly to our interpretation of features observed in core and outcrops deposited many millions of years ago. The Mussafah Channel is a man-made shipping canal cut perpendicular to the coastline, located to the southwest of the city of Abu Dhabi, and is ideal for studying costal depositional processes. The canal wall reveals a few meters of horizontally stratified Holocene sabkha and inter-tidal to shallow subtidal lagoonal sediments that vary significantly along its depositional strike direction and overlie Pleistocene dune deposits. Superb exposure of classic sabkha anhydrite occurs as highly contorted, enterolithic discontinuous bands. Sedimentology, petrography, x-ray diffraction and radiocarbon age dating analyses carried out along the vertical sabkha sequence show the following results: (1) uncemented, non-bedded calcareous sandstone: reworked aeolianite (ca 26,000 years BP - YBP); (2) uncemented cross-bedded to non-bedded calcareous sandstone: aeolianite/reworked aeolianite (ca 23,000 YBP); (3) crinkly-laminated microbial mat: inter-tidal deposits (ca 6,200 YBP); (4) fine-grained, grey-greenish interval with root marks, laterally grading into fine- to coarse-grained intervals with iron-stained, cross-bedded Cerithid-rich beds: lagoonal and tidal-channel deposits (ca 6,200 YBP); (5) cemented Cerithid- and bivalve-rich beds (hardgrounds): discontinuous, lithified channel lag deposits (ca 5,700 YBP); (6) cross-bedded, Cerithid-rich, bioclastic beds, grading laterally into intervals displaying gypsum rosettes and nodular to enterolithic anhydrite and microbial laminated carbonates: longshore beach bars and spits (ca 5,000 YBP). The sabkha sequence at Mussafah Channel represents the post-glacial Flandrian transgression resulting in the reworking of the Pleistocene aeolian dunes and the deposition of inter-tidal to shallow subtidal carbonate sediments. During the subsequent sea-level fall, these carbonates were overprinted (replaced) by gypsum and anhydrite. The observed lateral facies variations reflect primary reservoir quality variations, an important aspect to be considered for geological facies and reservoir quality modeling.

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain