Vertical Facies Successions
Ratcliffe lithofacies can be arranged in a vertical assemblage that depicts intertonguing of shallow shelf, restricted subtidal, peritidal, and supratidal facies associated with forward stepping, shallowing-upward paracycles. Ratcliffe reservoir beds in the study area include the Alexander and Flat Lake sub-intervals. Reservoir facies are incompletely to completely dolomitized mudstones and wackestones that occur in the middle and upper portions of paracycles. Forward stepping and vertical stacking of lithofacies controlled sediment accumulation and lateral distribution. Progradation of the Ratcliffe system was from east to west and sediment off-lapping produced facies belts that are laterally continuous along depositional strike. This ramp style of deposition characterizes the entire Ratcliffe.
In the project area, progradational facies belts crossed paleo-anticlines. Burrowed mudstones and wackestones became sites for selective dolomitization. Magnesium-rich brines which developed in overlying sabkha environments percolated through these restricted subtidal sediments producing porous, but generally low permeable reservoirs. Local fracturing which occurred during the Laramide Orogeny (Early Paleocene) enhanced these reservoirs