Upper Interval (bedrock surface): sedimentary-clast breccia with shaly matrix, clasts and blocks of Cretaceous shale and varied Paleozoic lithologies entrained in silty-sandy clay matrix; minor clasts/grains of Proterozoic “red clastics “ (mudstone/siltstone), crystalline basement rock, devitrified melt rock. Lower Interval (variably present, locally forms bedrock surface): overturned ejecta flap, breccias of Paleozoic lithologies and Proterozoic “red clastics” preserved in general inverted stratigraphic order. Breccias overlie down-dropped blocks (ring graben) of Cretaceous and Paleozoic strata in normal stratigraphic succession. Maximum thicknesses: upper shaly breccia up to 700 ft (210 m); lower interval approx. 1000 ft (300 m).