Statistical Characterization of a Confined Submarine Fan System: the Pennsylvanian Lower Atoka Formation, Ouachita Mountains, USA

Abstract:

Our knowledge of submarine fan deposits has historically relied heavily on qualitative field and subsurface observations and interpretations, but recent statistical analyses have been insightful to enhance the understanding of submarine fan sub-environments, the degree of confinement, stratigraphic patterns, and potential control factors. In this study, we integrate and develop a suite of statistical methods (Hurst Statistics / rescaled range analysis, bed thickness frequency distribution analysis, Markov Chains, and time-series analysis) to better understand a synorogenic submarine fan system deposited at a foreland basin setting – the Pennsylvanian lower Atoka formation in the Ouachita Mountains, United States. The results of the Hurst and bed thickness analyses corroborate qualitative interpretations that (1) the lower Atoka is lobe-dominated, and (2) the southeastern (wedge-top) portion of the system is more strongly confined than the northern (foredeep) portion . The Markov and time-series analyses reveal the prevalence (~50%) of stratigraphic orderliness, the nature of cyclicity, and the potential intrinsic and extrinsic controls on the sandstone recurrence cycles, which are otherwise difficult to distinguish qualitatively. The results of this study demonstrate that these integrated statistical methods can be utilized to quantify uncertainty in depositional interpretations of outcrops with limited exposures or 1D subsurface dataset.