Analysis of the Sheik 'Abd el-Qurna Landslide, Luxor, Egypt
Briget DoyleCollege of Charleston
Location
Continent: Africa
Country: Egypt
State/Province:
City/Town: Luxor
UTM coordinates and datum: WGS 1984 UTM Zone 36N
Setting
Climate Setting: Arid
Tectonic setting: Intracratonic Basin
Type: Process, Stratigraphy, Chronology
Click the images for a full-sized view.
Show Figure 1 caption
Hide
Description
Although the Theban Necropolis, near Luxor, Egypt, (Figure 1) is best known as the burial site of the kings, queens and nobles of Pharonic Egypt, it is also the site of several paleo-landslides. The largest of these landslides that has been identified is the complex bedrock mega-landslide of Sheik 'Abd el-Qurna (Figure 2). The hill known as Sheik 'Abd el-Qurna is both the location of the Tombs of the Nobles and the remains of a very large slump-block slide originating in the Theban Hills to the northwest (Figure 3). The Sheik 'Abd el-Qurna landslide is the result of slumping and translational block sliding of a large limestone block of the Thebes Formation, which overlays the weak Esna Shale. Failure of overlying competent bedrock underlain by weak or poorly indurated shale is a common mode of bedrock landslide failure around the world (Watkins, et al, 2007; Watkins and Rogers, 2005).
Slumps are a type of landslide typified by a curved failure surface, an arcuate headscarp, and back-rotation of the slide material toward the source area. The Sheik 'Abd el-Qurna slump block consists of a conglomerate cap, a portion of the middle member of the Thebes Formation, and the lower member of the Thebes Formation, all of which have experienced significant back-rotation toward the Theban Hills. The landslide is based in the upper portion of the Esna Shale. At the time of the failure, it is likely that the Nile River eroded both the Thebes and Esna Formations between Sheik 'Abd el-Qurna and the modern Nile River floodplain, attaining a local base level at the top of the well-lithified Tarawan Formation. The shales of the Esna Formation were preferentially eroded because they are softer and more friable than the limestones of the overlying Thebes Formation. Significant undercutting of the cliff face into the Esna Formation occurred on the outside of the meander. As undercutting proceeded, the overlying Thebes lost structural support and slumped down onto the paleo-Nile flood plain. The base of the Sheik 'Abd el-Qurna is marked by the distal end of a slump fault that is nearly horizontal under the hill.
Sheik 'Abd el-Qurna is a complex bedrock slump that moved in at least two episodes, as suggested by kinematic models of the landslide. The lower portion of the failure surface of the landslide is at the top of the Esna Shale, at an elevation of 150 m, and propagates upward through the overlying Thebes Formation (Figure 4a). During the first episode of movement, the overlying lower and middle members of the Thebes Formation underwent approximately 195 m of vertical displacement before movement stopped. At this point, the lower and middle members of the Thebes Formation had undergone back-rotation of approximately 16°, based on the kinematic model and balanced cross-sections (Figure 4b). In the time between the episodes of movement, a paleosol varying between 30 and 70 cm thick developed on the surface of the slump block. The paleosol was subsequently buried by alluvial fan and debris flow deposits that consolidated to form the conglomerate that now caps Sheik 'Abd el-Qurna. The source of the fan deposits is most likely the source of the landslide, in the Theban Hills.
At some time during or after the deposition of the conglomerate, the slump began to move again, eventually reaching its present location on the paleo-floodplain of the Nile River. This episodic movement is recorded in the dips of the members of the Thebes Formation as well as the dips of the paleosol and conglomerate. The Lower and Middle Members of the Thebes Formation have a strike of N 65o E and dip about 50o NW. The paleosol and conglomerate have the same strike, but dip only 15o NW (Figure 4c), suggesting their formation occurred during a pause in the movement of the slide, or contemporaneous with very slow movement of the slump.
Associated References:
- Doliber, S., Fronabarger, A.K., Doyle, B.C., in preparation. Analysis of the Sheik 'Abd el-Qurna Landslide, Theban Necropolis, Luxor, Egypt.
- Watkins, C. and Rogers, J.D, 2005. Analysis of Composite Bedrock Megalandslides in the Colorado River Corridor, Arizona. Association of Engineering Geologists, Program with Abstracts, 2005 Annual Meeting.
- Watkins, C., Rogers, J.D., and Warme, J., 2007. Reconstruction of Composite Landslides in Flat-Lying Sedimentary Strata Using Graphical Methods. Geological Society of America, Program with Abstracts, 2007 Annual Meeting.