Primary and secondary faulting in the Najd fault system, Kingdom of Saudi Arabia
Open-File Report
79-1661
By: John McMahon Moore
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Abstract
The Najd fault system is a major transcurrent (strike-slip) fault system of Proterozoic age in the Arabian Shield. The system is a braided complex of parallel and curved en echelon faults. Complex arrays of secondary structures including strike-slip, oblique-slip, thrust, and normal faults, together with folds and dike swarms, are associated with some major faults, particularly near their terminations. The secondary structures indicate that compressional and extensional and dilational conditions existed synchronously in different parts of the fault zone. The outcrop traces of faults and syntectonic dikes have been used to interpret the configuration of principal compressive stresses during formation of parts of the secondary fracture systems. Second-order deformation was a series of separate events in a complex episodic faulting history. Comparison with model studies indicates that master faults extended in length in stages and periodically developed arrays of secondary structures. Propagation of the major faults took place along splay trajectories, which inter-connected to form a subparallel sheeted and braided zone. Interpretation of the aeromagnetic maps indicates that the Najd system is broader at depth than the outcropping fault complex, and that more continuous structures underlie arrays of faults at surface. The fault pattern is mechanically explicable in terms of simple shear between rigid blocks beneath the exposed structures.
Suggested Citation
Moore, J.M., 1979, Primary and secondary faulting in the Najd fault system, Kingdom of Saudi Arabia: U.S. Geological Survey Open-File Report 79-1661, i, 26 p. ;28 cm., https://doi.org/10.3133/ofr791661.
ISSN: 2331-1258 (online)
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Primary and secondary faulting in the Najd fault system, Kingdom of Saudi Arabia |
| Series title | Open-File Report |
| Series number | 79-1661 |
| DOI | 10.3133/ofr791661 |
| Year Published | 1979 |
| Language | ENGLISH |
| Publisher | U.S. Geological Survey, |
| Description | i, 26 p. ;28 cm. |