Bibliographic Citation
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| DOI | http://dx.doi.org/10.1130/0016-7606(1997)109<0043:GWSPWD>2.3.CO;2 |
| Title | Ground-water sapping processes, Western Desert, Egypt |
| Creator/Author | Luo, W. ; Arvidson, R.E. ; Sultan, M. ; Becker, R. ; Crombie, M.K. [Washington Univ., St. Louis, MO (United States)] ; Sturchio, N. [Argonne National Lab., IL (United States)] ; Alfy, Z.E. [Egyptian Geological Survey and Mining Authority, Cairo (Egypt)] |
| Publication Date | 1997 Jan 01 |
| OSTI Identifier | OSTI ID: 460056 |
| Other Number(s) | Journal ID: BUGMAF; ISSN 0016-7606; Other: CNN: Grant NASAG 1358; TRN: TRN: 97:002634-040 |
| Resource Type | Journal Article |
| Resource Relation | Journal Name: Geological Society of America, Bulletin; Journal Volume: 109; Journal Issue: 1; Other Information: PBD: Jan 1997 |
| Subject | 58 GEOSCIENCES ;54 ENVIRONMENTAL SCIENCES ;99 MATHEMATICS, COMPUTERS, INFORMATION SCIENCE, MANAGEMENT, LAW, MISCELLANEOUS; GROUND WATER; REMOTE SENSING; DESERTS; EROSION; SIMULATION; GEOLOGY; ARID LANDS; MULTISPECTRAL PHOTOGRAPHY; ALGORITHMS; AGE ESTIMATION; COMPUTERIZED SIMULATION; TOMOGRAPHY; RUNOFF; URANIUM; THORIUM; LANDSAT SATELLITES; NUMERICAL DATA; EGYPTIAN ARAB REPUBLIC |
| Description/Abstract | 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. 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}{sup 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. This {delta}{sup 18}O-forced model also replicates the decrease in fluvial and sapping activity over the past million years. 65 refs., 21 figs., 2 tabs. |
| Country of Publication | United States |
| Language | English |
| Format | Medium: X; Size: pp. 43-62 |
| System Entry Date | 2009 Dec 16 |
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