Local and regional tectonic control on sedimentology and stratigraphy in a strike-slip basin: Miocene Temblor Formation of the Coalinga area, California, USA

Sedimentological study of the Lower to Middle Miocene Temblor Formation in the Coalinga area of the San Joaquin basin (California, USA) provides new results applicable to understanding patterns of sedimentation and stratigraphic architecture in strike-slip basins along tectonically active margins. Detailed investigation of surface outcrops on the Coalinga anticline is integrated with description of cores from an adjacent oil field. This approach yields information on lateral variability of facies as well as vertical sequences, which contributes to deciphering the facies geometry and stratigraphic pattern. Five facies tracts are identified in the Temblor Formation (in ascending order): incised valley, estuarine, tide- to wavedominated shoreline, diatomite, and subtidal. The vertical succession of facies tracts represents overall relative rise in sea level punctuated by episodes of non-deposition and exposure. Sediment accommodation was produced initially by incision of topography into the underlying Kreyenhagen Shale during relative sea-level fall and lowstand. Incised valley and estuarine facies tracts were deposited during subsequent rise in sea level. As additional accommodation was created by tectonic subsidence, tide-to wave-dominated, diatomite, and subtidal facies tracts were deposited. Periods of relative sea-level fall produced depositional hiatuses, some of which are overlain by distinctive shell-lag beds. The Temblor Formation represents deposition in an area influenced by along-strike tectonic variability associated with transform motion between the Pacific and North American plates. Stratigraphic study suggests that subsidence and uplift related to the transform boundary played a key role in deposition of the formation. Stratigraphic variations reflect the combination of basinal subsidence caused by regional extension and local uplift related to plate movement along the San Andreas transform zone. It is likely that strata deposited along other transform boundaries record similar tectonic effects. (C) 2002 Elsevier Science B.V. All rights reserved.