Muleshoe Mound revisited

Muleshoe Mound in the Sacramento Mountains of New Mexico has long been praised as an exceptional 3D exposure of a classic Waulsortian mud mound (i.e., a deep water, organic, carbonate mud-dominated buildup restricted to the Lower Carboniferous period). Waulsortian mud mounds are important hydrocarbon reservoirs and are thought to fill the biohermal evolutionary gap following the collapse of the Upper Devonian stromatoporoid/microbialite/tabulate coral buildups and the rise of phylloid algal buildups in the Upper Carboniferous. In the mid-1990s an idea was put forward that Muleshoe wasn’t an organic buildup, but a mounded stack of mostly calciclastic sediments deposited primarily by various types of gravity flows into deep water. At the time the idea was rejected, deemed heresy by the carbonate community and its scientific documentation buried in the gray literature of a New Mexico Geological Society fieldtrip guidebook.

Revisited here are the fundamental sedimentary attributes of Muleshoe Mound interpreted within a modern sedimentological framework that establish the mound was built up primarily by downslope laminar and turbulent gravity-driven flows with additional potential modification by drift/contour currents that are hybrid processes not previously recognized. The relevance of these findings is the important implications for the sedimentologic processes active on Lower Carboniferous epeiric sea carbonate ramps, which lack modern analogs.