Elucidating Geomorphometric Controls on Gulf of Mexico Minibasin Morphology

Minibasins are basins which subside into allochthonous or autochthonous salt bodies through the coevolution of depositional and halokinetic processes. In order to attain a greater understanding of the controls upon minibasin morphology, a series of 9 metrics were developed to quantify the morphologies of minibasins found within the northern Gulf of Mexico intraslope, via the application of geomorphometric and spatial point process analysis. Geomorphometric analysis revealed a positive two-term power series relationship between the first eccentricity and rugosity of the planform minibasin crestline geometries, by which increases in the eccentricity of a minibasin induce increases in rugosity. Furthermore, non-parametric ordinal association, conducted in the form of Spearman's rank-order correlation, revealed several significant relationships between the metrics. This includes the inverse control exerted by the divergence of the topographic minima (representative of the current subsidence maxima) from the minibasin centroid upon both the eccentricity and the volume encapsulated within the minibasin, as a result of the orientation of the current growth vector of the minibasin being in a state of unalignment with the time averaged long-term growth vector. This, in turn, works to increase the relative dimensions of the minor semi-axis of the minibasin, thereby decreasing the eccentricity, while also decreasing the volume of the minibasin due to the non-nadir alignment of the growth vector, which in turn decreases the magnitude of vertical subsidence. Moreover, it was divulged that minibasins proximal to the shelf edge exhibited relatively deeper surficial subsidence depths due to increases in the sediment supply as a result of proximity to the upstream sediment source. It was further revealed that increasing the centroidal dispersion of the minibasins results in increases in the volume of the resultant minibasins due to the decreased halokinetic influence exerted on the central minibasin by its neighbouring minibasins. Analysis of spatial point processes in the form of unweighted K-function cluster analysis moreover revealed significant dispersion between the centroids of the minibasins at distances under 17 km, which is postulated to be a product of the rheological properties of the underlying salt.