Deep-Sea Deposition in Density-Stratified Cratonic Basin, Bell Canyon Formation (Permian), Delaware Basin, Texas-New Mexico: ABSTRACT

Abstract

Sand and silt of the Bell Canyon Formation were deposited in a euxinic, deep-water, density-stratified basin. Laminated silt formed by suspension deposition from density interflows which moved along thermohaline interfaces; silty sand was deposited by bottom-hugging density underflows in submarine channels. The geometry of sandstone bodies is controlled by the configuration of nearly parallel, erosional channels oriented at high angles to the basin margin which range from less than 0.5 km to more than 8 km in width, 1 m to greater than 35 m in depth, and extend more than 70 km basinward. Channel erosion and sediment transport are interpreted to have resulted from long-lived density underflows which had many irregular fluctuations in flow strength. The flows may have origi ated as saline water was flushed from evaporitic shelf lagoons during storm ebb flow. The channels differ from modern and ancient submarine-fan channels attributed to turbidity-current processes in several ways, including: (1) the lack of radial or branching distributary-channel pattern; (2) few proximal to distal changes in grain size, bed thickness, and sedimentary structures; (3) the presence of abundant large-scale cross-stratification; (4) the lack of graded beds and Bouma sequences; and (5) the absence of clay-size detritus, levee, or overbank deposits. More than 100 oil and gas fields produce from the Bell Canyon Formation in west Texas and southeast New Mexico. Most reservoirs in the northern Delaware basin are stratigraphic-hydrodynamic traps which occur where deep sandstone-filled channels are incised into less permeable interchannel siltstone. Similar types of elongate, basinal, sandstone bodies confined to linear channels might be expected in other cratonic basins where there is a high potential for density stratification of basin waters and the generation of saline density currents. End_of_Article - Last_Page 553------------