--> Abstract: Tectonic Controls on the Sequence Stratigraphic Framework of a Forearc Strike-Slip Basin, Baja California (Mexico), by C. Busby, W. R. Morris, and L. Blikra; #90928 (1999).

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Abstract: Tectonic Controls on the Sequence Stratigraphic Framework of a Forearc Strike-Slip Basin, Baja California (Mexico)

BUSBY, CATHY1, WILLIAM R. MORRIS2, and LARS BLIKRA3
1Department of Geological Sciences, University of California, Santa Barbara, CA 93106
2Arco Exploration, and Research, 2300 West Plano Parkway, Plano TX, 75075
3Norwegian Geological Survey, Seksjon for Losmassekartlegging, Leiv Eirikssons vei 39, N-7040 Trondheim, Norway

The Rosario embayment of the Peninsular Ranges forearc basin complex provides the most areally extensive (3600 km3), three-dimensional, continuous exposure of undisrupted Cretaceous to Paleocene strata anywhere in California or Mexico. Coastal and inland exposures are so good that sedimentation units as thin as a few meters can be mapped continuously for distance of ten kilometers or more, while sediment packages tens of meters thick outcrop continuously for distances of tens of kilometers. Post-depositional faults in this basin are very few, with offsets of tens of meters or less. Basin-wide and extrabasinal correlations are aided by good foraminiferal and nannofossil yields, locally abundant macrofossils, and magnetostratigraphic data.

The Rosario Embayment forms an end-member type of basin: it is a strike slip basin, which is known to be the most tectonically active type of basin. Evidence of this activity includes “porpoising” of the Rosario basin from nonmarine to bathyal marine water depths twice during the Campanian alone. Subsidence was extremely nonuniform, involving tilting, and folding and reverse faulting, and normal faulting. Therefore, if any of the standard sequence stratigraphic models can be applied to this extremely active basin, they can probably be applied to just about any basin! Departures from standard models include: (1) formation of a submarine canyon during marine transgression; (2) inititation of turbidite deposition during a relative sea level rise; and (3) control of seismicity, rather than sea-level fluctuation, on catastrophic sedimentation in a coastal incised valley at the K/T boundary. Like other catastrophic boundary deposits in the Gulf of Mexico-Caribbean-Atlantic ocean region, these may have been triggered by meteorite impact.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas