Ground-water sapping processes, Western Desert, Egypt

Journal Article · Wed Jan 01 00:00:00 EST 1997 · 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]

---

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, Vol. 109, Issue 1; Other Information: PBD: Jan 1997
• Country of Publication: United States
• Language: English

Related Subjects

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