Coastal Plain Depositional Systems of the “Trias Carbonate” in the Berkine Basin, Algeria

The Trias Carbonate overlying the TAGI is present in the Berkine Basin and comprises mainly dolomitic shales, with interbedded dolomite layers. The interval is essentially non-reservoir, although thin channel sandstones (often oil stained) are occasionally encountered. Some fluvial terrigenous input is still important at this stage, with the influence of sea level fluctuations and probably regional tectonic events. Sandstones are fine to medium-grained and very thin in the central part of Berkine Basin (where marine conditions are dominant), but they may become thicker to the south of the basin (Turner et al., 2001). Based on core analysis, these sands are interpreted as high sinuosity fluvial/estuarine channels cutting a coastal plain. The purpose of this study is to identify vertical changes in facies, depositional environments and their distribution, sequence stratigraphy and relative sea level controls (Sabaou, 2003). Correlation of the stratigraphic successions with the regional sequence stratigraphic framework, based on 120 wells (Turner et al., 2001), shows that the vertical change in coastal plain character can be related to relatively high-frequency base level cycles that are expressed as transgressive-regressive marine cycles in downdip areas.