Laborcita Formation

The formation is composed mostly of marine beds[1] consisting of alternating cycles of limestone and siliclastic sedimentary beds[2] with a thickness of about 400 feet (120 m) at the type section. It is exposed only in a small area of the northernmost Sacramento Mountains, and transitions to mostly continental red mudstones some 1,000 feet (300 m) thick before abruptly pinching out to the southeast.[1] The formation lies on the Holder Formation[2] and is overlain by the Abo Formation.[1]

The formation is interpreted as cyclic sequences of terrestrial and shallow marine carbonates deposited on a narrow shelf lying between the Pedernal uplift to the east and the Orogrande basin to the west.[1][2] Cycles are generally transgressive, with basal conglomerate giving way to increasingly fine sandstone, siltstone, and shale and finally limestone. Corresponding regressive sequences are very poorly developed.[2]

The limestone beds of the formation are highly fossiliferous,[1] containing bioclastic remains from all the main late Paleozoic shallow marine biotic groups.[2] Fusilinids are present that are characteristic of the latest Pennsylvanian and earliest Permian.[1] The uppermost beds contain algal bioherms 35–60 feet (11–18 m) thick.[1][3][4] Microfossils of the formation include the cyanobacteria such as Girvanella, calcivertellid foraminiferans, and phylloid algae such as Eugonophyllum.[2]

The formation was first named by Otté in 1959 as part of his dissertation at the University of New Mexico.[1]

• List of fossiliferous stratigraphic units in New Mexico
• Paleontology in New Mexico

• Bowsher, Arthur L. (1987). "Paleozoic reef complexes of the Sacramento Mountains, New Mexico". Rocky Mountain Section of the Geological Society of America: 447–450. doi:10.1130/0-8137-5402-X.447.
• Cross, T. A.; Klosterman, M. J. (1981). "Autecology and Development of a Stromatolitic-Bound Phylloid Algal Bioherm, Laborcita Formation (Lower Permian), Sacramento Mountains, New Mexico, U.S.A.". Phanerozoic Stromatolites: 45–59. doi:10.1007/978-3-642-67913-1_6.
• Krainer, Karl; Vachard, Daniel; Lucas, Spencer G. (March 2003). "Microfacies and microfossil assemblages (smaller foraminifera, algae, pseudoalgae) of the Hueco Group and Laborcita Formation (upper Pennsylvanian-lower Permian), south-central New Mexico, USA". Rivista Italiana di Paleontologia e Stratigrafia. 109 (1): 3–36. Retrieved 5 August 2020.
• Otté, C. Jr. (1959). "Late Pennsylvanian and Early Permian stratigraphy of the northern Sacramento Mountains, Otero County. New Mexico". New Mexico Bureau of Mines and Mineral Resources Bulletin. 5Q (1).