Biostratigraphy and petrography of upper Paleozoic rocks of Sierra Las Pintas, northern Baja California

• Published in: Journal of South American earth sciences 2018-07, Vol.84, p.160-171
• Main Authors: Navas-Parejo, Pilar, Lara-Peña, R. Aaron, Torres-Martínez, Miguel Angel, Martini, Michelangelo
• Format: Article
• Language: English
• Subjects: Early Permian; Late Pennsylvanian; Pelmatozoan; Southwestern Laurentia
• ISSN: 0895-9811; 1873-0647
• DOI: 10.1016/j.jsames.2018.03.010

A transported crinoid fauna is herein described for the first time in the Paleozoic succession cropping out in the Sierra Las Pintas, northern Baja California, northwestern Mexico. The fossil association includes Heterostelechus texanus Moore and Jeffords, Preptopremnum laeve? Moore and Jeffords, and Mooreanteris perforatus Moore and Jeffords, which indicates a Middle Pennsylvanian-early Permian time-averaged age. The studied area corresponds with the northernmost outcrop of definitely late Paleozoic deep-water facies in northwestern Mexico and the southern United States. Petrographic analyses indicate that the studied metasandstones were primarily derived from high-grade metamorphic rocks and from a shallow-water platform environment dominated by crinoid meadows. These results allow the correlation of the studied metasedimentary rocks with the Carboniferous Rancho Nuevo Formation of the Sonora allochthon, which crops out in central Sonora. The Sonora allochthon includes an Early Ordovician-Late Pennsylvanian sedimentary succession that was deposited in the oceanic basin located south of the Laurentian craton. Therefore, upper Paleozoic metasedimentary rocks of the Sierra Las Pintas were deposited along the same continental margin of Laurentia as those rocks in the Sonora allochthon, and were mostly derived from metamorphic rocks of the continental craton and by the typical Carboniferous encrinites, which characterize the shallow-water rocks of central and northern Sonora. •First Late Pennsylvanian-early Permian crinoids from the Sierra Las Pintas area, Baja California.•Sierra Las Pintas is the northernmost outcrop of late Paleozoic deep-water facies in Mexico.•Metasandstones were derived from the continental shelf and cratonic platform with abundant crinoids.•The analyzed rocks correlate with the Carboniferous Rancho Nuevo Fm of central Sonora.