Fluvial/tidal interaction at the southern Tethyan strandline during Triassic Mukheiris times in central Jordan

Abstract

The Triassic (Anisian) Mukheiris Formation is exposed along the northeastern margins of the Dead Sea area, and encompasses all those sediments preserved between the Triassic Hisban and Iraq al Amir formations. It attains a thickness of at least 108 m, and comprises two subdivisions defined here: a lower tidal unit and an upper fluvial unit. The presence of fossiliferous limestones and marlstones in the lower member, and the presence of thin, rhythmic tidal bedding, flaser bedding and oscillation ripple marks suggests deposition in a tidally influenced shallow water, marine environment. The erosively based, fining-upward cycles of non-fossiliferous, unidirectional cross-bedded quartz arenites, and paucity of siltstones and mudstones in the lower part of the fluvial unit indicate that deposition occurred within a braided mixed load fluvial system. The increased proportion of fines ratio in the upper part suggests a change to a more meandering fluvial system. The spatial and temporal arrangement of tidal/fluvial facies during Mukheiris times may be related to fluctuations of the Tethyan strandline due to fluctuations in relative sea level and the development of alternating transgressive and regressive events.