Bajocian-Bathonian (Middle Jurassic) sea-level changes in northeastern Egypt: Synthesis and further implications

Abstract

The global eustatic developments can benefit significantly from properly acquired regional information. Summarizing the available interpretations of the relative sea-level changes from two areas in northeastern Egypt, namely Gebel Maghara and Khashm El-Galala, allows better understanding of the Middle Jurassic sea-level changes. It is established that the Bajocian-Bathonian relative sea-level changes in these areas were coherent. The magnitude of changes was lower in the Bajocian than in the Bathonian. Significant sea-level rises occurred at the Bajocian-Bathonian and middle-late Bathonian transitions, and there was a clear tendency toward sea-level rise throughout the studied time interval. This evidence favors one of the two alternative global eustatic reconstructions that implies “stable” position of the shoreline in the Bajocian and general tendency to eustatic rise throughout the Jurassic. The tectonic regime of northeastern Egypt in the Middle Jurassic provided for strong eustatic control of the relative sea-level changes. The possible influence of hotspot activity is questionable. Filling the accommodation space with materials derived from the eroded continent may explain some sea-level falls that are regionally documented.