--> ABSTRACT: Quantitative Analysis of a Transpressional System, El Biod Arch, Ghadames Basin, Algeria, by Steven R. Moore, Robert W. Krantz, Kaci Akkache, and Mohamed Messaoudi; #91019 (1996)
[First Hit]

Datapages, Inc.Print this page

Quantitative Analysis of a Transpressional Previous HitSystemNext Hit, El Biod Arch, Ghadames Basin, Algeria

Steven R. Moore, Robert W. Krantz, Kaci Akkache, and Mohamed Messaoudi

Previous HitTrapNext Hit definition within the northern extension of the Hassi Touareg - Rhourde El Baguel fault zone in the western Ghadames Basin of Algeria is difficult due to complex Previous HitstructuralNext Hit geometries. The fault zone consists of a narrow Previous HitsystemNext Hit of discontinuous, locally en echelon faults. Although north-trending to the south, the zone curves to a northeast trend to the north. Reserves associated with the southern portion of the Previous HitsystemNext Hit total 1500 MMBOR and 2 TCFG.

Several lines of evidence support a strike-slip component of motion for the northern segment. Horizontal slickensides have been described in cores taken from wells within the fault trend. Fracture patterns measured from logs taken within the NE-SW fault trend show clusters expected for right-lateral Reidel shears. Although complicated by an evaporite sequence at mid-level in the stratigraphic section, we interpret downward converging faults imaged on recent 2D seismic as positive flower profiles. Map patterns are also interpreted as right-lateral, recognizing that the 2D grid cannot resolve all of the Previous HitstructuralNext Hit complexity.

To confirm the component of strike-slip fault displacement, we applied a new quantitative method relating map view Previous HitstructuralNext Hit orientations to the shear magnitude, the degree of convergence or divergence, and the magnitudes of horizontal and vertical strains. Strike-slip to convergence ratios ranging from 2:1 to 3:1 were measured in the study area. Higher ratios (10:1) measured above the salt may indicate a detachment.

These ratios also fit the regional tectonic pattern: to the south, where the fault zone trends due north, Previous HitstructuralNext Hit geometries support dip-slip inversion indicative of east-west shortening. Applying the same shortening vector to the northeast-trending part of the zone suggests oblique right-lateral motion, with a strike-slip to convergence ratio of 2:1. Horizontal shortening measured from seismic near Hassi Touareg combined with the above ratios indicates 1 to 2 kilometers of strike-slip motion occurred in the study area. The quantitative agreement of the different approaches supports the oblique strike-slip interpretation as well as the detailed Previous HitstructuralTop interpretation within the fault zone.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California