Laborcita Formation
The Laborcita Formation is a geologic formation in the Sacramento Mountains of New Mexico. It preserves fossils dating back to the late Pennsylvanian to early Permian.[1]
| Laborcita Formation Stratigraphic range: Pennsylvanian to Permian | |
|---|---|
| Type | Formation |
| Underlies | Abo Formation |
| Overlies | Holder Formation |
| Thickness | 400 feet (120 m) |
| Lithology | |
| Primary | Limestone, conglomerate, sandstone. shale |
| Location | |
| Coordinates | 33.011°N 105.941°W |
| Region | New Mexico |
| Country | United States |
| Type section | |
| Named for | Laborcita Canyon |
| Named by | Otté |
| Year defined | 1959 |
  Laborcita Formation (the United States)  Laborcita Formation (New Mexico) | |
Description
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]
Fossils
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]
History of investigation
The formation was first named by Otté in 1959 as part of his dissertation at the University of New Mexico.[1]
Footnotes
- Otté 1959
- Krainer et al. 2003
- Cross and Klosterman 1981
- Bowsher 1987
References
- 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).