The Ediacaran volcanosedimentary succession of Gabal Abu Had, North Eastern Desert, Egypt: geological study, facies anal
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ORIGINAL PAPER
The Ediacaran volcanosedimentary succession of Gabal Abu Had, North Eastern Desert, Egypt: geological study, facies analyses, and depositional setting Khaled El-Gameel 1 Received: 28 September 2017 / Accepted: 9 April 2018 / Published online: 23 April 2018 # Saudi Society for Geosciences 2018
Abstract Gabal Abu Had is an exposure of a volcanosedimentary succession in the North Eastern Desert Basement Complex. This succession includes intercalation of two major rock units, which are Dokhan Volcanics and Hammamat Group with different styles of formation, deposition environments, and genesis. Gabal Abu Had succession (GHS) is a northward dipping, c. 700-mthick volcanosedimentary succession that rests on metavolcanic and old granitoid rocks with erosion unconformity. The lower part of GHS is dominated by volcaniclastic mass flow deposits and andesitic lava with interbedded gravely sandstone, whereas the upper sequence is composed of pyroclastic flow deposits including welded to no welded ignimbrite intercalated with gravely sandstone and massive clast-support conglomerate toward the top. Facies analysis study of GHS presented eight lithofacies types, which grouped into five lithofacies associations. The GHS basin started with effusive eruption of silica-poor volcanic center, which produced andesitic lava. A part of lava underwent hyaloclastic fragmentation due to the presence of fluvial water in places producing the volcaniclastic mass flow deposits. Later, an explosive silica-rich volcanic center affected the GHS basin and created the pyroclastic plain deposits (ignimbrite and bedded tuff). The fluvial braided river is still in action since the first eruption, producing gravely sandstone, which is intercalated with the volcanic sequence. The upper GHS is characterized by thick, massive, and clast-supported conglomerate (well rounded clasts up to 100 cm) of alluvial fan facies. Several silica-rich and silica-poor subvolcanic intrusions were emplaced in the GHS. The GHS development displays a cycle from low- to high-energy sedimentation under humid climatic conditions, in addition to extension and down faulting of basin shoulders. In comparison with Gabal El Urf, located to the north of GHS and was studied by El-Gameel (2010), the GHS is a lava-rich succession rather than Gabal El Urf succession which is mainly pyroclastic rich. Keywords Gabal Abu Had . Hammamat Group . Dokhan Volcanics . Facies analysis . Egypt
Introduction The Arabian Nubian Shield (ANS) forms the northern part of the East African Orogen that evolved during the Neoproterozoic (870–530 Ma). It is a juvenile continental crust that was formed by accretion of island arc terranes (Bentor 1985; Stern 1994, 2002; Abdelsalam and Stern 1996; Stein and Goldstein 1996; Jarrar et al. 2003; Stoeser and Frost 2006), and is bounded to the east and west by older
* Khaled El-Gameel [email protected] 1
Geology Department, Faculty of Science, Menofia University, Shibin El Kom, Egypt
crust (Stacey and Stoeser 1983; Stacey and Hedge 1984; Sultan
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