Stratigraphy
Lehman (1994) advocated a simplified stratigraphy of up to five geologic formations. The basal unit is the Santa Rosa Sandstone, a braided stream channel-related facies. The Santa Rosa is overlain by the Tecovas Formation, which is dominated by overbank (distal floodplain) deposits with lenses of channel-deposits. Minor lacustrine deposits are also occurring. The Trujillo Sandstone, channel-deposits, and Cooper Canyon Formation, overbank deposits with minor channel and lacustrine deposits, are separated from the Santa Rosa-Tecovas by an unconformity. In eastern New Mexico, the Redonda Formation overlies the Cooper Canyon Formation. The Redonda has gradational eastward transition into the upper Cooper Canyon Formation.
The Santa Rosa-Tecovas sequence has sediments made up of clasts derived from the north, northeast, and east of the Dockum, very similar to clasts found in the lower Chinle. However, the Trujillo-Cooper Canyon sequence’s sediments are derived from the Ouachita orogenic belts of the Marathon Uplift.
Read more about this topic: Dockum Group