A paleontological survey of a part of the Tesuque Formation near Chimaya, New Mexico, and a summary of the biostratigraphy of the Pojoaque Member (Middle Miocene, Late Barstovian)
Scott B. Aby, Gary S. Morgan, and Daniel J. Koning

Abstract:

 A recent paleontological survey north of Chimayó, NM, identified many new localities containing Miocene mammal fossils and one site containing freshwater(?) gastropods. All fossils were found within eight sections (T21N, R9E) at the southwest end of the survey area within the Pojoaque Member of the Tesuque Formation. The majority of the fossils were found within ~120 m stratigraphic interval containing the Pojoaque white ash zone, which to the south contains an ash that is 13.7 ± 0.18 Ma. Correlation of the Pojoaque white ash zone with the magnetic-polarity stratigraphy of Barghoorn, (1981), indicates an age range of 14.0-13.2 Ma for this ash zone. All fossils were found within sediments derived from Proterozoic metamorphic and Paleozoic sedimentary (sandstone, limestone, and shale) terrains to the northeast with minor and variable input of volcaniclastic material from the Latir vocanic field near Taos. Laterally adjacent and overlying sediments derived pri­marily from Proterozoic granite to the east are barren of fossil material. The fossil-bearing strata have been interpreted to rep­resent a basin-floor environment while the barren, granitic sediments are interpreted as a piedmont environment. Preferential fossilization may reflect either different diagenetic conditions in the lime-bearing sediments relative to the sediments derived primarily from Proterozoic sources or reflect some inherent difference in depositional environment. A compilation of published paleontological data along with our recent findings produces a summary of the known fauna of the Pojoaque Member of the Tesuque Formation. Approximately 65 species of mammals are currently known from the Pojoaque Member, which represents one of the most important samples of early late Barstovian (early middle Miocene) mammals in western North America.


Citation:

  1. Aby, Scott B.; Morgan, Gary S.; Koning, Daniel J., 2011, A paleontological survey of a part of the Tesuque Formation near Chimaya, New Mexico, and a summary of the biostratigraphy of the Pojoaque Member (Middle Miocene, Late Barstovian), in: Geology of the Tusas Mountains and Ojo Caliente Area, Koning, Daniel J.; Karlstrom, Karl E.; Kelley, Shari A.; Lueth, Virgil W.; Aby, Scott B., New Mexico Geological Society, Guidebook, 62nd Field Conference, pp. 347-358.

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