Confined, high-gradient slope channels in the Decie Ranch Member: a reinterpretation of Wolfcamp A deepwater deposition in the Lenox Hills of Brewster County, Texas

The Decie Ranch Member of the Skinner Ranch Formation (Wolfcamp A equivalent) in the Lenox Hills of Brewster County, Texas, is dominated by blocky and massive, sand- to pebble-sized calciclastic deposits with common bioclasts and mudstone rip-up clasts. It is reinterpreted to have been deposited in a confined, high-gradient slope channel system rather than a low gradient, unconfined basin-floor environment. Channel elements in the Decie Ranch Member are extremely thick for deepwater systems, ranging from 60 to 70 ft, placing them at the upper end of documented global channel dimensions. Because channel thickness commonly scales with slope gradient and erosional depth increases where gradients are steepest, these dimensions imply incision and deposition under high-energy conditions on a relatively steep slope. The coarse-grain size and thick-bedded character of the deposits further support this interpretation, reflecting flows capable of transporting large clasts. The channels in the Decie Ranch Member comprise a single channel complex which exhibits organized, laterally offset stacking of individual channels. This style of channel organization resembles the behavior typically attributed to leveed systems; however, key levee indicators are absent. No fining- or thinning-away trends of overbank facies are observed, or fine-grained channel tops are present, and successive channels do not overlap. These characteristics suggest that the system was located near or beyond the setting where excess mud is partitioned into levees. In mud-poor calciclastic settings, rapid loss of fines on steep slopes can prevent extensive levee construction, suggesting the location of avulsing channels was more likely influenced by negative topography created by underfilled channels rather than levee-controlled pathways. Although a large-scale erosional valley cannot be directly mapped in outcrop, its presence is inferred from the cumulative channel thickness and the narrow width of the complex. Collectively, these observations support interpretation of the Decie Ranch Member as a bypass-dominated, coarse-grained slope channel system formed under steep gradients, refining the depositional framework for mud-poor carbonate slopes and improving prediction of stratigraphic architecture in similar deepwater settings.