Coastal geology and revised stratigraphy of the Brega area, northeastern Libya

Abstract

While describing the geology of the Brega area, NE Libya, the Brega Sandstone Bed of Pliocene age was established as a new stratigraphic unit in this part of Libya (Kumar, 2014). New field data from the western regions of Brega especially along the Brega Area One beach provides some new significant geological information. New outcrops of the Brega Sandstone Bed and Ajdabiya Formation are described. A new hitherto unknown outcrop of beachrocks is also described. Based on these outcrops and their stratigraphic relationships, a new stratigraphy for the Brega area is proposed. The new outcrop of the Brega Sandstone Bed is much larger and is exposed along the sea coast. It is of grayish yellow to brown color and intensely bioturbated, and unlike the outcrops of this stratigraphic unit in the Brega Area Two, this outcrop shows distinct bedding planes that dip 15° to 20°E to ESE. A new outcrop of Pleistocene Ajdabiya Formation was observed in close vicinity of the newly observed outcrop of the Brega Sandstone Bed. There is an unconformable contact between the Ajdabiya Formation and underlying Brega Sandstone Bed. A new outcrop of beachrocks was observed on the southwestern end of the Brega Area One beach. These rocks are very hard, of gray to dark gray color, and are characterized by numerous circular to sub-circular holes of various diameter and depth; these are filled by floating crude oil that is derived from leakages and spills of crude oil pumped into ships for export from the Brega Port. These rocks are mostly unfossiliferous but at places, fossil corals and gastropods were noted. Presence of corals is problematic because there are no coral reefs offshore Braga or in the nearby waters of the Mediterranean Sea. It is possible that the fossil corals from Libya could have been eroded and transported by wind and water during the past and transported to the beaches of Brega. Ultimately, these corals along with calcareous beach sand were lithified by calcium carbonate and became parts of beachrocks. The gastropods found in the beachrocks are local shallow marine inhabitants, and they can be observed on the surface of the Brega Sandstone Bed as well as in the recent sediments.