ABSTRACT

Grain fabric studies were conducted on channel and levee sandstones within an exposed submarine fan channel-levee complex from the Permian Brushy Canyon Formation of the Delaware Basin in west Texas-New Mexico, using anisotropy of isothermal remanent magnetization (IRMA). This study is the first of its kind that has tested the hypothesis of an angular deviation in the grain orientation from a channel and its corresponding levee deposit. This method of rock magnetic measurements reflect a sedimentary fabric when the long axes of grains are oriented parallel to bedding and are coherently aligned along flow direction and the short axes are perpendicular to bedding. The study has been done on samples spread over a lateral distance of thirteen meters across a channel margin. The results indicate a high angular deviation of approximately 80° between the mean grain alignments within the channel and the proximal levee deposits. The grains in the channel sandstones are aligned approximately east-west and those within the levee deposits are aligned north-south due to deviations in the paelocurrent direction of the depositing flows. The deviation in the grain-alignment is attributed to the overbanking of gravity flows from within the confines of the channel and dispersal laterally outward. The results of this study have important implications for preferential fluid flow pathways in deep water reservoirs.