Hydrogeologic significance of depositional systems and facies in Lower Cretaceous sandstones, north-central Texas
The Lower Cretaceous Hosston and Hensel Sandstones are important sources of ground water in North-Central Texas. Delineation of major depositional systems and their component facies within these formations provides a method for predicting the quantity, movement, and chemical composition of water in the aquifers. The Hosston and Hensel Sandstones were deposited during minor reversals of marine transgression onto the Texas craton by Comanchean (Lower Cretaceous) seas. A net sandstone map of the Hosston Formation shows two major depositional trends: (l) a dip-oriented (west-east) meanderbelt fluvial system, strongly influenced in the west by relief on the underlying Wichita paleoplain, which supplied sediment to (2) a strike-oriented (north-south) high-destructive, wave-dominated delta system overlying the Ouachita foldbelt in the east. The Hensel deposits prograded eastward across the relatively featureless upper surface of the Pearsall Formation, forming two depositional systems similar to those of the Hosston. The meanderbelt sandstone facies of the fluvial systems and the coastal barrier facies of the delta systems are thick, laterally persistent sandstone bodies capable of supplying greater amounts of ground water than the flood basin, lagoon-marsh- embayment, or prodelta-shelf facies, which are composed principally of mudstone and siltstone. Regional ground-water movement in both formations is to the southeast with hydraulic gradients of 10 to 15 feet per mile (2 to 3 meters/kilometers).Transmissivity averages 8,000 gallons per day per foot (1.2 liters/second/meter) in the Hosston and 5,000 gallons per day per foot (0.7 liters/second/meter) in the Hensel. Hydrochemical facies of water in the Hosston and Hensel Sandstones coincide with the principal lithogenetic facies of the two depositional systems. Ground water is dominantly of the calcium magnesium bicarbonate type in the fluvial system but changes downdip to sodium sulfate and sodium bicarbonate types in the delta systems, indicating a change in conditions of chemical equilibrium.