Ground-water sapping processes, Western Desert, Egypt

Journal Article · Tue Dec 31 23:00:00 EST 1996 · Geological Society of America, Bulletin

DOI:https://doi.org/10.1130/0016-7606(1997)109<0043:GWSPWD>2.3.CO;2· OSTI ID:460056

Luo, W; Arvidson, R E; Sultan, M; Becker, R; Crombie, M K ^[1]; Sturchio, N ^[2]; Alfy, Z E ^[3]

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1. Washington Univ., St. Louis, MO (United States)
2. Argonne National Lab., IL (United States)
3. Egyptian Geological Survey and Mining Authority, Cairo (Egypt)

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.

• OSTI ID: 460056
• Journal Information: Geological Society of America, Bulletin, Journal Name: Geological Society of America, Bulletin Journal Issue: 1 Vol. 109; ISSN BUGMAF; ISSN 0016-7606
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
99 GENERAL AND MISCELLANEOUS
AGE ESTIMATION
ALGORITHMS
ARID LANDS
COMPUTERIZED SIMULATION
DESERTS
EGYPTIAN ARAB REPUBLIC
EROSION
GEOLOGY
GROUND WATER
LANDSAT SATELLITES
MULTISPECTRAL PHOTOGRAPHY
NUMERICAL DATA
REMOTE SENSING
RUNOFF
SIMULATION
THORIUM
TOMOGRAPHY
URANIUM