B. C. Canyon Field, Howard County, Texas: An Ancient Analogy to Modern Tropical Tower Karst Terrains

Abstract

Late in the early deposition of sediments in Canyon field, a series of glacio-eustatically controlled sea level lowstands resulted in a carbonate buildup seaward of the Horseshoe Atoll in Howard County, Texas. The resulting satellite reef tract consists of fringing boundstone; high-energy shelf grainstones; lower energy shelf packstones and wackestones; and thin, highstand, black shales and mudstones. The original extent and thickness of deposits were extensively modified during karstification coincident with successive sea level lowstands. The resulting paleotopographic landforms appear to be similar to tower karst features of Puerto Rico. During the beginning of each sea level highstand, the paleoterrain was modified by erosion. The basinal foreshelf conglomerates resulting from initial highstand erosion contain dipping strata that commonly can be detected by the dipmeter tool. The mechanism for the formation of these strata may be depositional or the result of diagenetic alteration of the rock fabric in the burial environment. Using dipmeter data, an uneconomic producer has been offset by one of the better producing wells in the field.