Brown, L. F. (Leonard Franklin), 1928-2011-08-052017-05-112011-08-052017-05-111987-12http://hdl.handle.net/2152/12906textHydrocarbon producing, deep-water Cisco sands along the Eastern Shelf were studied in the vicinity of Flowers "Canyon Sand" Field to develop a depositonal model explaining their origin, geometry, and style of deposition. Regional correlations and subsurface mapping indicate that producing sands were deposited within the Swastika lithogenetic unit, which contains a network of shelf-margin fluvial/deltaic, slope, and basin depositional systems deposited between transgressive Gunsight and Ivan Limestones. The sands are not "Canyon", but Virgilian in age. During Swastika time a wedge of sediments up to 1100 feet thick was deposited in the study area in response to westward progradation of shelf-margin deltas. Standard mapping techniques and detailed correlations using nearly 700 well logs and the examination of 3 cores indicate that this wedge can be divided into three principal systems: (1) a sand-dominated turbidite, basin and lower slope system, which constitutes the reservoir facies, (2) a shale-rich prodelta/slope system punctuated by slope channel filled gullies, and (3) a sand-dominated shelf-margin fluvial/deltaic system. Ten deltaic lobes, averaging 2 miles in diameter, were recognized. These lobes may have been deposited during a lowstand of sea level. Elongate/lobate geometry and rapid shifting of lobes indicate high depositional rates. Shelf-margin instabilities associated with deltas led to prodelta/slope slumping, gully formation, and generation of turbidity currents. Turbidity currents generated by the earliest deltas to breach the shelf break were of sufficient magnitude to erode a broad, shallow inner-fan valley at the base of the slope. This valley initially focused turbidity currrents onto a base-of-slope terrace, which was mapped on top of the Gunsight Limestone, and formed by differential compaction over a subjacent Canyon delta or carbonate buildup. Low gradients associated with this terrace gave rise to a sediment trap. Nearly all existing production in Flowers Field is established above this terrace. Turbidites deposited within this phase of Swastika evolution display characteristics of an elongate/radial type fan deposit. Continued deltaic progradation filled the inner-fan valley. Once this valley was breached, a network of small channels originating as gullies along slopes in front of the advancing Swastika delta system transported sediment down the slope to form an aggrading/prograding wedge of turbidite and volumetrically less significant grain flow deposits. This change in depositional style led to superposition of what is best classified as an elongate/debris apron type system over the earlier elongate/radial deposits. A critical conclusion is that no single channel developed into a large canyon feeder system, which resulted in facies relationships that differ from commonly accepted models calling on a prolonged point source. Given the importance of turbidite sands in many petroliferous basins, application of the delta-fed model to appropriate turbidite systems can improve exploration strategies.electronicengCopyright is held by the author. Presentation of this material on the Libraries' web site by University Libraries, The University of Texas at Austin was made possible under a limited license grant from the author who has retained all copyrights in the works.Turbidites--Texas--Stonewall CountySedimentary structures--Texas--Stonewall CountyGeology, Stratigraphic--PennsylvanianGeology--Texas--Stonewall County