--> Abstract: Stratigraphy, Facies, and Environment of Deposition of the Yates Formation, North Ward Estes Field, Ward County, Texas, by R. D. Johnson and J. M. Mazzullo; #90950 (1996).

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Abstract: Stratigraphy, Facies, and Environment of Deposition of the Yates Formation, North Ward Estes Field, Ward County, Texas

Ronnie D. Johnson, James M. Mazzullo

The Artesia Group is an interbed sequence of sandstones, shales, carbonates and evaporites that was deposited in back reef and lagoonal settings of the Permian Basin during late Permian time. The environment of the carbonate and evaporites in this group are well established but questions about the origins of the clastics and the effects of sea level and sediment supply fluctuations on their accumulation persist. This study of cores, well logs, and petrophysical data of the Yates formation of the Artesia Group from North Ward Estes Field provides the opportunity to address these questions.

The Yates is composed of four clastic and one carbonate facies. Facies 1 consists of well-sorted fine sandstones and coarse siltstones that are non-fossiliferous and contain wavy parallel laminations. This facies is interpreted as an eolian erg deposit. Facies 2 consists of fine sandstones and coarse siltstones with clay drapes, flaser beds and no bioturbation which are interpreted as fan-delta plain deposits. Facies 3 consists of reddish brown fine sandstones with bioturbated and haloturbated structures that are interpreted as clastic-dominated sabkha deposits. Facies 4 consists of fining-upward beds with pebbles at their bases and clay laminations atop which are interpreted as, fluvial-channel deposits. Facies 5 consists of bioturbated carbonate mudstones that are interpreted as sha low marine deposits.

The deposition of Yates clastics began during a sea level lowstand and continued during a subsequent sea level rise. This is indicated by the sharp basal contact between the clastic-rich Yates and the carbonate-rich Upper Seven Rivers, and the thick anhydrite bed that marks the top of the Yates. In addition, there is evidence for cyclic deposition of the clastics and carbonates in the Yates that resulted from changes in sediment supply and the shifting of depocenters.

AAPG Search and Discovery Article #90950©1996 AAPG GCAGS 46th Annual Meeting, San Antonio, Texas