Geology of the Brega area and the ichnofauna of the ‘Brega Sandstone Bed’ (Pliocene), Libya

Abstract

The sandstone outcrops in the Brega Area Two are designated as ‘Brega Sandstone Bed’ on the basis of the lithological similarities and stratigraphy of the region surrounding Brega. The ‘Brega Sandstone Bed’ is considered to be equivalent to the lower part of the Member V of the Sahabi Formation of the Pliocene age. The thinly bedded greyish to greenish sandstone interbedded with gravel and pebble beds exposed at the ‘Sea cliff section’ represents the upper part of Member V of the Sahabi Formation. Outcrops of Pleistocene-cemented marine dunes belong to the Ajdabiya Formation and are seen as patches of marine dunes of various shapes, lengths and heights that run parallel to the modern day Mediterranean Sea coastline. The Holocene sediments around Brega include coastal and inland sand dunes and sand sheets mixed with millions of 'beach balls'. The ichnofaunal assemblage of the ‘Brega Sandstone Bed’ is dominated by various types of vertical, oblique and horizontal burrows that are branched and unbranched. They are dominated by ichnogenera Ophiomorpha and Skolithos. The ichnocoenose dominated by these two ichnogenera belong to the marine soft ground Skolithos ichnofacies. Lithology of the ‘Brega Sandstone Bed’ and its ichnocoenose indicate a shallow marine, intertidal to shallow subtidal, moderate to high energy depositional environments.