Evidence for Upper Cretaceous seismites in the Abu Tartur area, Western Desert, Egypt

Upper Cretaceous tidal-flat sediments of the Abu Tartur region, Western Desert of Egypt, contain a variety of softsediment deformation structures (SSDSs) in the Mut Member of the Quseir Formation and the overlying Duwi Formation. Here, we document recognition of a set of SSDSs characterized by complex morphology and large size. The SSDS include: 1) water-escape structures, 2) minor recumbent, chevron, and slump folds, 3) synsedimentary minor faults, 4) neptunian dykes, 5) regular ball-and-pillow structures, flattened pseudo-nodules, and load casts, 6) syn-sedimentary undulations, 7) fractures and joints, 8) sand injectites, and 9) autoclastic breccia and brecciated siderite clasts. The dimensions of the SSDSs range from a few centimeters to several decimeters. Both extensional and contractional forces appear to have been involved in development of these structures. A detailed analysis of facies relationships, combined with consistent orientations of SSDSs and the regional tectonics of the target area suggests earthquakes as the triggering mechanism for sediment deformation and large-scale mass failure. The deformed strata are consistent with most of the well-known criteria of typical seismites. Thus, syn-sedimentary liquefaction was identified as the primary driving force in most of the observed deformation horizons for these Upper Cretaceous SSDSs in the Abu Tartur area.

Automated summary

The Upper Cretaceous tidal-flat sediments in the Abu Tartur region of the Western Desert of Egypt contain a variety of complex and large softsediment deformation structures (SSDSs). These structures, including water-escape structures, folds, faults, and others, were likely triggered by earthquakes and syn-sedimentary liquefaction. The recognition of these structures provides insight into the geological history and tectonic activity of the area.