Inferring Hypogene Karst at Depth from the Patterns of Non-Tectonic Syncline Networks in Eocene Limestones, Western Desert, Egypt
نویسندگان
چکیده
Indirect indicators are critically important for recognizing hypogene karst that is too deep-seated to have explorable caves. We suggested in previous publications an extensive network of non-tectonic synclines otherwise flat-lying Eocene limestone Egypt might be such indirect indicator. proposed formed by sag layers overlying a zone today remains deep below the surface and speleogenesis resulted from ascending aggressive fluids associated with crustal extension magmatism during Red Sea Rift initiation. Without caves explore, however, we were unable provide compelling evidence processes. By doubling our mapping area 4,000 8,000 km 2 , clear picture has emerged patterns syncline speleogenesis. Over this larger area, displays two distinct patterns: 1) ridges outline polygons 700–2,000 m across, 2) narrow N–S zones spaced 5–10 apart, WNW–ESE NW–SE trending shallow traversing panels between zones. The geometries suggest controlled structural rocks underlying limestones: polygonal faults shales reactivated N–S, left-lateral basement largely blind at current level erosion. These structures served as conduits conveyed upward into limestones, triggering dissolution depth pattern above was inherited nature fractures limestones. unique characteristics applicable elsewhere indicator karst. Our new data also strongly formation spanned time onset rifting ∼23–22 Ma. Endogenic CO mantle-derived basaltic magmas likely significant component fluids, perhaps involving highly supercritical . Mantle-derived C He modern Egyptian oasis water may still locally active.
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ژورنال
عنوان ژورنال: Frontiers in Earth Science
سال: 2021
ISSN: ['2296-6463']
DOI: https://doi.org/10.3389/feart.2021.678565