Deepwater Sediment Facies and Sole Marks of the Numidian Flysch, Algeria

Abstract

The sedimentology of the Numidian Flysch (Upper Oligocene) of the Ouarsenis Mountains, Northwest Algeria, is presented here for the first time. The outcrops of the Foret des Cedres section comprise thick and very-thick bedded sandstones as the dominant facies. They are interbedded with more minor mudstones. Five distinct facies have been identified including: (1) massive sandstone, (2) normally-graded sandstone, (3) parallel-laminated sandstone, (4) siltstone, and (5) mudstone. The range of the observed bedding and facies characteristics can be interpreted as resulting from deepwater gravity flow processes. Many sole marks are present on the bases of the overturned sandstone beds including groove casts, flute marks, gutter casts, longitudinal ridge and furrow marks, mud ripples, and frondescent marks. A new type of flute-mark structure is documented here for the first time on the base of medium-grained sandstone beds. These features are designated as curved flute marks. It is suggested that they result from the flow interaction with an obstacle or irregular relief on the seafloor in the path of a strong turbidity current. Similar features have been generated in laboratory simulations by Dzulynski [4].