Magnetostratigraphic correlation and dating of West Texas and New Mexico Late Permian strata
Maureen B. Steiner
Ochoan formations in west Texas-New Mexico have been investigated magnetostratigraphically for the purpose of obtaining age information. The locally-named Dewey Lake Formation has been studied in two areas of northwest Texas and in southeastern New Mexico. The subjacent Alibates and Rustler formations also are being investigated in these areas. Data from the Magenta Dolomite Member of the Rustler Formation near Carlsbad, NM, indicate three magnetic polarity intervals, contained within 11 m of dolomitic strata. Only preliminary Magenta data are available at present; nevertheless, four stratigraphic sections in the member consistently indicate the three polarity intervals. Additionally and surprisingly, reliable paleomagnetic data have been obtained from the Castile Formation. The reconnaissance data show a relatively strong remanent magnetization which is stable to thermal demagnetization procedures. A probable reversed polarity Late Permian magnetization was obtained. Within the Dewey Lake Formation of west Texas, magnetostratigraphy shows that relative thickness of enclosed volcanic ash beds is not a reliable correlation tool; ash beds of similar thickness located 120 km apart lie in different magnetic polarity intervals . Magnetostratigraphy has shown that the 0.6 m ash layer at Dickens, TX, corresponds to a 0.02 m ash layer (the upper of two) at Caprock Canyons State Park. Magnetostratigraphy also demonstrates that fully one-half of the Dewey Lake Formation present in northwest Texas (Caprock Canyons) has been removed by pre-Late Triassic erosion in the more southerly localities. Late Permian, rather than Triassic, paleopoles are obtained from the Dewey Lake beds. The data of this study suggest a correlation of the Magenta Dolomite with the lower exposed portion of the Alibates strata of northwest Texas (Caprock Canyons State Park). A Late and Middle Permian magnetostratigraphic time scale is derived by combining all available magnetostratigraphic studies. The Dewey Lake-Alibates/Rustler magnetostratigraphic sequences correlate well with the global magnetic polarity pattern and suggest that the Alibates/Rustler strata may be latest Capitanian in age and that the Dewey Lake (Quartermaster) strata were deposited in the Wujiapingian and early Changsingian Stages of the Late Permian.
- Steiner, Maureen B., 2001, Magnetostratigraphic correlation and dating of West Texas and New Mexico Late Permian strata, in: Geology of the Llano Estacado, Lucas, Spencer G.; Ulmer-Scholle, Dana S., New Mexico Geological Society, Guidebook, 52nd Field Conference, pp. 59-68.