Arid
DOI10.1130/0016-7606(1997)109<0043:GWSPWD>2.3.CO;2
Ground-water sapping processes, Western Desert, Egypt
Luo, W; Arvidson, RE; Sultan, M; Becker, R; Crombie, MK; Sturchio, N; ElAlfy, Z
来源期刊GEOLOGICAL SOCIETY OF AMERICA BULLETIN
ISSN0016-7606
EISSN1943-2674
出版年1997
卷号109期号:1页码:43-62
英文摘要

Depressions of the Western Desert of Egypt (specifically, Kharga, Farafra, and Kurkur regions) are mainly occupied by shales that are impermeable, but easily erodible by rainfall and runoff, whereas the surrounding plateaus are composed of limestones that are permeable and more resistant to fluvial erosion under semiarid to arid conditions. Scallop-shaped escarpment edges and stubby-looking channels that cut into the plateau units are suggestive of slumping of limestones by ground-water sapping at the limestone-shale interfaces, removal of slump blocks by weathering and fluvial erosion, and consequent scarp retreat. Spring-derived tufa deposits found near the limestone escarpments provide additional evidence for possible ground-water sapping during previous wet periods. A computer simulation model was developed to quantify the ground-water sapping processes, using a cellular automata algorithm with coupled surface runoff and ground-water flow for a permeable, resistant layer over an impermeable, friable unit. Erosion, deposition, slumping, and generation of spring-derived tufas were parametrically modeled. Simulations using geologically reasonable parameters demonstrate that relatively rapid erosion of the shales by surface runoff, ground-water sapping, and slumping of the limestones, and detailed control by hydraulic conductivity inhomogeneities associated with structures explain the depressions, escarpments, and associated landforms and deposits. Using episodic wet pulses, keyed by delta(18)O deep-sea core record, the model produced tufa ages that are statistically consistent with the observed U/Th tufa ages. This result supports the hypothesis that northeastern African wet periods occurred during interglacial maxima. The delta(18)O-forced model also replicates the decrease in fluvial and sapping activity over the past million years, as northeastern Africa became hyperarid. The model thus provides a promising predictive tool for studying long-term landform evolution that involves surface and subsurface processes and climatic change.


类型Article
语种英语
国家USA ; EGYPT
收录类别SCI-E
WOS记录号WOS:A1997WF33400003
WOS关键词EASTERN SAHARA ; MONSOON ; TOPOGRAPHY ; RAINFALL ; PLATEAU ; VALLEYS ; ORIGIN ; OASIS ; FLOW
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/2XILL650/134227
作者单位(1)WASHINGTON UNIV, DEPT EARTH & PLANETARY SCI, MCDONNELL CTR SPACE SCI, ST LOUIS, MO 63130 USA;(2)ARGONNE NATL LAB, ARGONNE, IL 60439 USA;(3)EGYPTIAN GEOL SURVEY & MIN AUTHOR, CAIRO, EGYPT
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GB/T 7714
Luo, W,Arvidson, RE,Sultan, M,et al. Ground-water sapping processes, Western Desert, Egypt[J],1997,109(1):43-62.
APA Luo, W.,Arvidson, RE.,Sultan, M.,Becker, R.,Crombie, MK.,...&ElAlfy, Z.(1997).Ground-water sapping processes, Western Desert, Egypt.GEOLOGICAL SOCIETY OF AMERICA BULLETIN,109(1),43-62.
MLA Luo, W,et al."Ground-water sapping processes, Western Desert, Egypt".GEOLOGICAL SOCIETY OF AMERICA BULLETIN 109.1(1997):43-62.
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