--> Tempestite Sedimentation: An Example from the Del Rio Formation of West Texas, Brian E. Lock, Robert W. Butler, and Roark T. Franklund, #90093 (2009)

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Tempestite Sedimentation: 

An Example from the Del Rio Formation of West Texas
 

Brian E. Lock, Robert W. Butler, and Roark T. Franklund
 

Department of Geology, University of Louisiana at Lafayette, P.O. Box 44530, Lafayette, Louisiana  70504

 

ABSTRACT

 

The Del Rio Formation (Cenomanian) consists primarily of shales, with sparse limestones and sandstones.  Many of the limestones are composed almost entirely of winnowed concentrations of the oysters that are abundant in the shales.  The infrequent but strong current action responsible for the winnowing is interpreted as related to storm events, primarily because of the characteristics of the sandstones.  The sandstones are commonly graded, with oyster shell concentrations at the base and with distinctive sole marks (prod, short grooves, and other tool marks) and, in some cases, display convolute lamination at the top.  In many respects, these beds resemble turbidites, but associated features indicate that these are storm deposits (“tempestites”).  Some beds show textbook examples of hummocky cross-stratification at several scales, gutter casts are found in some localities, and the absence of flute casts are all suggestive of tempestites rather than turbidites.  Paleontological and paleogeographic data indicate relatively shallow waters at this time, and the associated microbial mat structures (Kinneyia sp.) are known primarily from tempestite-dominated sediments elsewhere in the geologic record.  The abundance of oysters and agglutinating forams as the main elements of the fauna are consistent with influx of significant freshwater run-off during and after heavy storms, while the sandstones may result from storm surge relaxation allowing water to flow back seaward, carrying sand from nearby shorelines.

 

Lock, B. E., R. W. Butler, and R. T. Franklund, 2009, Tempestite sedimentation:  An example from the Del Rio Formation of West Texas:  Gulf Coast Association of Geological Societies Transactions, v. 59, p. 463-476.

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AAPG Search and Discover Article #90093 © 2009 GCAGS 59th Annual Meeting, Shreveport, Louisiana