Berino Formation Explained

Berino Formation
Type:Formation
Period:middle Pennsylvanian
Prilithology:Limestone
Otherlithology:Shale
Namedfor:Berino, New Mexico
Namedby:L.A. Nelson
Year Ts:1940
Region:New Mexico
Country:United States
Coordinates:31.9667°N -106.525°W
Underlies:Bishop Cap Formation
Overlies:La Tuna Formation
Thickness:555feet

The Berino Formation is a geologic formation in the Franklin Mountains of southern New Mexico and western Texas. It preserves fossils dating back to the middle Pennsylvanian.[1]

Description

The unit consists mostly of fossiliferous limestone with some interbedded shale.[2] The shale is more abundant in the base of the formation, and the formation as a whole appears brown banded in outcrop. Beds are typically about 20feet thick, with a prominent massive limestone bed 70feet thick capping the formation.[1] The total thickness is 555feet. The unit lies on the La Tuna Formation and is overlain by the Bishop Cap Formation.[2]

The formation is interpreted as resulting from deposition of rhythmically alternating lime and clay in a shallow marine environment.[1]

Fossils

The Berino Formation contains abundant fossils, including ichnofossils. These include the fusulinid Fusulinella euryteines and brachiopods, corals, and bryozoa. Fragments of petrified wood are found at the base of the formation and are interpreted as remnants of tree trunks carried out to sea.[1]

History of investigation

The unit was designated the Berino Member of the Magdalena Group by L.A. Nelson in 1937.[3] Kues and Giles recommended discarding the Magdalena Group and raising the unit to formation rank in 2004.[4]

See also

Notes and References

  1. Harbour . R.L. . 1972 . Geology of the northern Franklin Mountains, Texas and New Mexico . U.S. Geological Survey Bulletin . 1298 . 10.3133/b1298. free .
  2. Nelson . L.A. . 1940 . Paleozoic stratigraphy of the Franklin Mountains, West Texas . American Association of Petroleum Geologists Bulletin . 24 . 1 . 157–172 . 10.1306/3D93319A-16B1-11D7-8645000102C1865D.
  3. Nelson . L.A. . 1937 . Gastropoda from the Pennsylvanian (Magdalena) of the Franklin Mountains of west Texas [abstract of thesis] . Colorado University Studies . 25 . 1 . 89–91.
  4. Encyclopedia: Kues . B.S. . Giles . K.A. . 2004 . The late Paleozoic Ancestral Rocky Mountain system in New Mexico . Mack . G.H. . Giles . K.A. . The geology of New Mexico. A geologic history (Special Volume 11) . New Mexico Geological Society . 98.