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The San Gabriel Basin is a Pliocene—Pieistocene Transverse Ranges structure bounded by the San Gabriel Mountains on the north, the San Jose and Puente Hills on the east, and the Repetto and Montebello Hills on the west. A basement boundary between gneissoid rocks of San Gabriel Mountains aspect and Peninsular Ranges rocks strikes east across the basin and connects with the San Jose fault. This boundary may represent the eastward continuation of the Canton fault, a middle Miocene precursor of the San Gabriel fault system with up to 30 km of right slip. Canton fault displacement is largely canceled by ∼22.5 km of left slip on a precursor to the Raymond fault such that an Oligocene dacite in the San Jose Hills and clasts derived from it show little evidence of large horizontal displacement between the San Gabriel Mountains and Puente Hills. Clockwise rotation in the middle Miocene probably influenced the distribution of lateral slip. The fill in the northeast-trending Pliocene—Pleistocene San Gabriel Basin is a basal shallow-marine sequence overlain by the nonmarine Duarte Conglomerate, in contrast to the deep-water Fernando Formation of the Los Angeles Basin. The paleoslope trends south in the direction of the Repetto and Puente Hills, evidence that uplift of these hills postdated deposition. The triangular San Gabriel Basin is currently a stable block bounded by the right-slip, northwest-striking East Montebello fault on the west and the left-slip(?), northeast-striking Walnut Creek fault on the east. Farther east, the San Jose and Puente Hills are underlain by an east-trending active fold belt, including the San Jose reverse fault and anticline, the Walnut anticline, and the Puente Hills anticline adjacent to the right-lateral Whittier fault. The East Montebello fault is bounded on the west by the Elysian Park anticlinorium, a fold belt in downtown Los Angeles. The left-slip Holocene Raymond fault joins the Sierra Madre reverse fault at its segment boundary marked by the Clamshell-Sawpit fault. The triangular stable block between east-trending fold belts is bounded on the south by the Puente Hills blind thrust and on the north by the Sierra Madre fault, documenting north-south Quaternary convergence. East-west extension is also indicated, although not confirmed by geodetic measurements. [ABSTRACT FROM AUTHOR]

As in many continental margins, Mesozoic rifting in the Gulf of Mexico trended subparallel to older tectonic structures created by opening and closure of a prior ocean basin. Unlike the situation in most other margins, however, extension in the Gulf of Mexico did not involve widespread reactivation of these older tectonic features. This difference may be related to the unusual facts that (1) the antecedent passive continental margin was a transform rather than a rift margin and (2) the prior orogeny did not substantially thicken the crust. In order to characterize the interaction between Mesozoic rifting and prior tectonic events, two geophysical transects were constructed across the central Gulf of Mexico coastal plain and continental shelf. The transects show that the early Paleozoic passive continental margin buried beneath the late Paleozoic Ouachita orogen was little affected by compressional tectonism or Mesozoic extension during opening of the Gulf of Mexico. The thickness of the crust on this ancient margin decreases from 35 km to 10 km over a distance of only 50 km, consistent with previous interpretations that this was a transform margin. The Ouachita fold-and-thrust belt is shown to be a thin-skinned doubly vergent orogen that formed above a well-preserved southward-dipping subduction system. Relict Cambrian oceanic crust may exist beneath the southern part of the orogen, but its presence is not required by the data. The thin crust and shallow mantle in the Ouachita suture created a zone of relatively high strength that acted as a barrier to Mesozoic extension, which is restricted to regions south of the orogen. Extension was initially distributed over a broad area that included the Mississippi Interior Salt Basin and regions south of the Wiggins Arch. Extension became progressively more focused south of the Wiggins Arch with time, culminating in the onset of seafloor spreading beneath the modern continental rise. Mesozoic extension factors are β = 1.4-1.9 beneath the Mississippi Interior Salt Basin, β ≈ 2.9 immediately south of the Wiggins Arch, and β ≈ 4 adjacent to the oldest oceanic crust in the central Gulf of Mexico. Keywords: Gulf of Mexico; North America; rifting; Ouachita orogeny; gravity profiles. [ABSTRACT FROM AUTHOR]

Examines the association of backarc and arc-related tectonic units in California. Influence of alkalic and arc-related magnetic processes to backarc basin; Initiation of the Franciscan subduction; Formation of the Round Mountain serpentine melange.

Presents the results of a study on the distribution of fluid pressure, the origin of cement and vein minerals that inhibit fluid flow, and the mechanisms for fluid migration and fluid-pressure generation within the northeastern part of Cook Inlet basin in Alaska. Tectonics of upper Cook Inlet basin; Lithology of tertiary and upper mesozoic sedimentary rocks.

Presents the results of a study which examined the origin and age of the Manila high and associated sunklands in the Big Lake basin of northern Arkansas' New Madrid seismic zone. Stratigraphy; Topography; Deformation chronology of the Manila high and Big Lake basin; Position of the Little River.

Proposes a model for progressive arcward contraction of the fore-arc basin in the Rumsey Hills region, southwestern Sacramento Valley, beginning in Cretaceous and continuing episodically through Cenozoic time. Seismic reflection data used to develop the forward model; Major tectonic and depositional events; Stratigraphic and structural relationships.