干旱区生态环境知识资源中心(Arid): Inferring Hypogene Karst at Depth from the Patterns of Non-Tectonic Syncline Networks in Eocene Limestones, Western Desert, Egypt

Arid

DOI	10.3389/feart.2021.678565
	Inferring Hypogene Karst at Depth from the Patterns of Non-Tectonic Syncline Networks in Eocene Limestones, Western Desert, Egypt
	Tewksbury, Barbara J.; Tarabees, Elhamy A.; Welch, Robert M.; Mehrtens, Charlotte J.
通讯作者	Tewksbury, BJ (corresponding author), Hamilton Coll, Dept Geosci, Clinton, NY 13323 USA.
来源期刊	FRONTIERS IN EARTH SCIENCE
EISSN	2296-6463
出版年	2021
卷号	9
英文摘要	Indirect indicators are critically important for recognizing hypogene karst that is too deep-seated to have explorable hypogene caves. We have suggested in previous publications that an extensive network of non-tectonic synclines in otherwise flat-lying Eocene limestone in Egypt might be such an indirect indicator. We proposed that synclines formed by sag of limestone layers overlying a zone of hypogene karst that today remains deep below the surface and suggested that hypogene speleogenesis resulted from ascending aggressive fluids associated with crustal extension and magmatism in Egypt during Red Sea Rift initiation. Without hypogene caves to explore, however, we were unable to provide compelling evidence for hypogene karst processes. By doubling our mapping area from 4,000 to 8,000 km(2), a clear picture has emerged of patterns in the syncline network that provide compelling evidence for hypogene speleogenesis. Over this larger area, the network displays two distinct patterns: 1) synclines and ridges that outline polygons 700-2,000 m across, and 2) narrow N-S zones of synclines spaced 5-10 km apart, with WNW-ESE to NW-SE trending shallow synclines and ridges traversing the panels between N-S zones. The geometries suggest that the syncline network is controlled by two structural patterns in rocks underlying the limestones: 1) polygonal faults in underlying shales and 2) reactivated N-S, left-lateral basement faults that are largely blind at the current level of erosion. These structures served as conduits that conveyed fluids upward into the overlying Eocene limestones, triggering dissolution at depth and a pattern of sag above that was inherited from the nature and pattern of faults and fractures in rocks underlying the limestones. The unique patterns and characteristics of this network of synclines are applicable elsewhere as an indirect indicator of deep-seated hypogene karst. Our new data also strongly suggest that syncline formation spanned the time of crustal extension in Egypt associated with onset of Red Sea rifting similar to 23-22 Ma. Endogenic CO2 associated with mantle-derived basaltic magmas was likely a significant component of fluids, perhaps involving highly aggressive supercritical CO2. Mantle-derived C and He in modern Egyptian oasis water suggest that hypogene speleogenesis may still be locally active.
英文关键词	hypogene karst speleogenesis syncline remote sensing fluid flow Google Earth polygonal faults Riedel shears
类型	Article
语种	英语
开放获取类型	gold
收录类别	SCI-E
WOS记录号	WOS:000673158800001
WOS关键词	FAULT SYSTEM ; NILE VALLEY ; FLUID-FLOW ; RED-SEA ; STRATIGRAPHY ; NORTHERN ; ORIGIN ; EVOLUTION ; SEQUENCE ; FRACTURE
WOS类目	Geosciences, Multidisciplinary
WOS研究方向	Geology
资源类型	期刊论文
条目标识符	http://119.78.100.177/qdio/handle/2XILL650/363284
作者单位	[Tewksbury, Barbara J.] Hamilton Coll, Dept Geosci, Clinton, NY 13323 USA; [Tarabees, Elhamy A.] Damanhour Univ, Dept Geol, Damanhour, Egypt; [Welch, Robert M.] Harvard Univ, Dept Earth & Planetary Sci, 20 Oxford St, Cambridge, MA 02138 USA; [Mehrtens, Charlotte J.] Univ Vermont, Dept Geol, Burlington, VT USA
推荐引用方式 GB/T 7714	Tewksbury, Barbara J.,Tarabees, Elhamy A.,Welch, Robert M.,et al. Inferring Hypogene Karst at Depth from the Patterns of Non-Tectonic Syncline Networks in Eocene Limestones, Western Desert, Egypt[J],2021,9.
APA	Tewksbury, Barbara J.,Tarabees, Elhamy A.,Welch, Robert M.,&Mehrtens, Charlotte J..(2021).Inferring Hypogene Karst at Depth from the Patterns of Non-Tectonic Syncline Networks in Eocene Limestones, Western Desert, Egypt.FRONTIERS IN EARTH SCIENCE,9.
MLA	Tewksbury, Barbara J.,et al."Inferring Hypogene Karst at Depth from the Patterns of Non-Tectonic Syncline Networks in Eocene Limestones, Western Desert, Egypt".FRONTIERS IN EARTH SCIENCE 9(2021).