Sedimentological evolution and diagenesis of lower Eocene limestones, the Sinn El-Kaddab Plateau, the southern extent of the Tethys Sea in Egypt

Abstract

This article describes a 135-m-thick sequence collection from the lower Eocene limestones of the Dungul Formation that caps the Sinn El-Kaddab Plateau in the Kurkur area. A sedimentological evolution model of these limestones has been constructed for the first time primarily based totally on lithology, microfacies analysis, SEM microscopy, and EDAX microchemical analyses. This carbonate sequence has been subdivided into three shallowing-upward facies. The hemipelagic facies at the base is dominated by foraminiferal wackestone, unconformably overlain by shallow offshore facies dominated by larger benthic foraminiferal grainstone and packstone, and capped by middle ramp facies dominated by bioclastic grainstone and packstone. These facies are analog of the Eocene facies of the Tethys Sea that had been formerly defined from Libya, Tunisia, Spain, and Kirkuk oil field in Iraq. Results suggest deposition in a basin characterized by oscillation in relief, in response to tectonic uplifting coupled with eustatic sea fluctuations associated with and the Syrian arching system. The limestones exhibit four successive diagenetic stages. The first stage is early marine diagenesis with the formation of micrite rim cement and preferential micritization of some skeletal grains. The second stage is shallow burial diagenesis, compaction, drusy calcite cement, and silicification. The third stage is meteoric diagenesis, the formation of isopachous calcite rim cement, dissolution and formation of blocky cement. The fourth stage is vadose diagenesis which includes karstification and ferrugination with iron oxy-hydroxides impregnation.