The Arid Shallow Subtidal to Supratidal Environment: A Case Study from the Abu Dhabi Sabkha (United Arab Emirates)

Christian J. Strohmenger¹, Abdulla Al-Mansoori¹, Omar Al-Jeelani¹, Ismail Al-Hosani¹, Ali Al-Shamry¹, Hesham Shebl², Khalil Al-Mehsin³, and Salem Al-Baker^1
1ADCO, Abu Dhabi, United Arab Emirates
²ZADCO, Abu Dhabi, United Arab Emirates
³ADNOC, Abu Dhabi, United Arab Emirates

Shallow subtidal to supratidal carbonate successions, deposited under arid conditions along the Abu Dhabi coastline vary in two important aspects from carbonates of the same environments deposited under humid conditions (e.g. the Bahamas):

The occurrence of supratidal evaporites (gypsum, anhydrite, and halite).

The restriction of the microbial mat to the intertidal zone (in humid settings microbial mats dominate the supratidal zone).

Along the Abu Dhabi coastline a vertical and lateral sabkha sequence were studied at Mussafah industrial channel and in the vicinity of Al-Qanatir Island, respectively. The vertical sabkha sequence of the channel cut shows reworked Pleistocene carbonate-rich aeolian sandstones (radiocarbon age: ca 23,000 years before present) being overlain by a well developed microbial mat (radiocarbon age: ca 6,200 years before present) which is overlain by lagoonal, tidal-channel, and beach bar deposits that are partly to completely overprinted by gypsum and anhydrite. The lateral sabkha sequence displays classic examples of supratidal (upper, middle, and lower sabkha), intertidal (microbial mat) and lowermost intertidal to shallow subtidal (lagoon) facies belts. Radiocarbon ages of the analyzed subsurface hardgrounds and microbial mats range between ca 3,500 and ca 900 years before present; thereby supporting the seaward progradation of the facies belts since the last Flandrian sea-level highstand.

The distribution of radiocarbon ages indicates a complex stratigraphic history in which chronostratigraphic time lines clearly cross-cut depositional facies and diagenetic boundaries. If the horizontal dimensions of facies belts are less than the typical well spacing, the use of modern analogs, together with seismic and production data help to construct more realistic geologic and simulation models of subsurface reservoirs.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas