--> Abstract: Coniacian-Turonian Carbonates of the Miskar Field, Offshore Tunisia, by I. Knott, R. Moody, and R. Sandman; #90956 (1995).

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Abstract: Coniacian-Turonian Carbonates of the Miskar Field, Offshore Tunisia

Iain Knott, Richard Moody, Ross Sandman

The R1 and R1 Superior Carbonates of the Miskar Field, offshore Tunisia are of Coniacian-Turonian age. These ages are constrained by several biostratigraphic events including a rapid increase in ostracod diversity at the base of the overlying Aleg Formation and the occurrence of several diagnostic benthonic foraminifera including Rotalia algeriana. The indication is that the R1 and R1 Superior Carbonates are the lateral equivalents, in part, of the Douleb Formation which is a known reservoir, onshore Tunisia.

During the Coniacian-Turonian the area of the Miskar Field was subject to regional extension with the opening of several major North-South trending fractures. These culminate in the contemporaneous outpouring of submarine serpentinised volcanics during deposition of the R1 Superior/Aleg Formation.

The R1 lithologies are deposited in a shallow water regime and consist of rudist buildup and debraic carbonates overlain by lagoonal facies in the North with an increase in beach/sabkha facies to the South. The indication is for a shallowing upward sequence and a general progradation of lithofacies northwards across a tilted block.

In contrast the R1 Superior is indicative of a flooding event with relative sea-level changes reflected in variations of both lithofacies and biofacies. Overall the lithofacies are dominated by calcispheric/bioclastic wackestone-packstones probably deposited in a mid-platform setting.

The diagenetic history of the R1 is the more complex of the two carbonate sequences reflecting several phases of fluid movement through the constituent lithologies. Original depositional characteristics and subsequent diagenetic modification result in the development of highly variable reservoir properties.

AAPG Search and Discovery Article #90956©1995 AAPG International Convention and Exposition Meeting, Nice, France