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. |
