부산대학교 도서관

This article briefly outlines the geology of aquatic deposits in the Ma‘an desert, which consist of semi-consolidated gypsum layers intercalated by semi-consolidated sandstones, siltstones and mudstones with stromatolitic structures. They were deposited in a periodic river, called the Tawil River, and after that in a pond environment. The Tawil River is incised into the chalky limestone (Um Rijam Chert Limestone Formation, Eocene) and was filled later with cross-bedded sand. In the shallower parts, the river bed sediments dried out and mud cracks have been formed. Muddy deposits of the pond had been penetrated by plant roots, which traces are still quite clearly visible in some places. When the ponds dried out, salts started to precipitate forming crusts of gypsum and halides. Halides became washed away again by the next flood while gypsum remained in solid form. The outcrops are overlain by a recent soil covered by eroded chert fragments of the Um Rijam Chert Limestone Formation. The area has been influenced by tectonic events which can be made responsible for the preservation or disappearance of the river deposits. The Tawil River surrounding and the subsequent ponds had also served for ancient humans as a settlement ground and the hunting area.