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Gravity and mechanical study of the Great Bend in the Mexia-Talco Fault Zone, Texas

1971; American Geophysical Union; Volume: 76; Issue: 11 Linguagem: Inglês

10.1029/jb076i011p02690

2156-2202

Gary W. Crosby,

earthquake and tectonic studies

The Mexia-Talco fault zone is one segment of a structural zone that forms the northern rim of the Gulf of Mexico basin. A gross graben structure is commonly developed in the belt of en echelon faults; thus, the zone is an extensional feature. In northeast Texas the Mexia-Talco zone bends abruptly by 75° in Hunt County, in an area largely covered by Holocene fluviatile deposits. The near-surface position of individual faults is weakly expressed in the gravity field. The faults apparently maintain their trends into the great bend and in an alternate fashion mutually terminate against fault members of the opposite trend; however, because of the en echelon arrangement in the two segments of the zone that meet at the bend, the change in the trend of individual fault strikes is less than half that of the zone as a whole. The zone coincides with a broad ‘step’ anomaly wherein gravity increases 6.8 mgal relatively abruptly from the southeast to the north and west sides of the zone. Model computations suggest that the Jurassic Louann salt thins from a thickness of 350 meters on the Gulfward side to zero within the zone. The geometry of individual faults and the zone as a whole is compatible with an extensional mechanical scheme wherein Mesozoic and Tertiary sediments were translated passively a short distance basinward, facilitated by long-duration salt flowage.