The Hayner Ranch Formation is a

geologic formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

found near the San Diego Mountains of

New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...

. It is estimated to have been deposited during the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

Description

The Hayner Ranch Formation consists of about of red to tan

volcaniclastic Volcaniclastics are geologic materials composed of broken fragments (clasts) of volcanic rock. These encompass all clastic volcanic materials, regardless of what process fragmented the rock, how it was subsequently transported, what environment it ...

conglomerate,

mudstone Mudstone, a type of mudrock, is a fine-grained sedimentary rock whose original constituents were clays or muds. Mudstone is distinguished from ''shale'' by its lack of fissility.Blatt, H., and R.J. Tracy, 1996, ''Petrology.'' New York, New York, ...

, and

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

. It is the lowest formation of the Santa Fe Group in the San Diego Mountains area, overlying older volcanic rock of the Spears Group. The formation fills paleovalleys eroded in the underlying volcanic beds. The formation is particularly well exposed in a

half graben A half-graben is a geological structure bounded by a fault along one side of its boundaries, unlike a full graben where a depressed block of land is bordered by parallel faults. Rift and fault structure A rift is a region where the lithosphere ...

between the East and West Selden Hills; in Selden Canyon to the west; at its

type section In geology, a stratotype or type section is the physical location or outcrop of a particular reference exposure of a stratigraphic sequence or stratigraphic boundary. If the stratigraphic unit is layered, it is called a stratotype, whereas the ...

in the Tonuco Uplift; and in the Rincon Hills to the north, where it is coarser (including boulder conglomerates) and partially silicified. The formation is interpreted as

stream A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a strea ...

and

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...

deposits near the axis of a broad

closed basin Closed may refer to: Mathematics * Closure (mathematics), a set, along with operations, for which applying those operations on members always results in a member of the set * Closed set, a set which contains all its limit points * Closed interval, ...

. The narrow (12 km) half graben is tilted to the northeast and has its

footwall In geology, a fault is a planar fracture or discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movements. Large faults within Earth's crust result from the action of plate tectonic f ...

on the

Caballo Mountains The Caballo Mountains, (Spanish: "horse") are a mountain range located in Sierra and Doña Ana Counties, New Mexico, United States. The range is located east of the Rio Grande and Caballo Lake, and west of the Jornada del Muerto; the south of ...

block, where displacement was about . Study of the formation and others in the area support at least four episodes of block faulting starting 35 million years ago, almost all along faults trending north–south. The formation records the unroofing of the Caballo Mountains. Clasts in the lower part of the formation are derived from the underlying Spears Group and those higher in the formation from the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

Palm Park and Love Ranch Formations. However, clasts from the

Doña Ana Mountains The Doña Ana Mountains are a mountain range in Doña Ana County, New Mexico. The highest elevation in the range is Doña Ana Peak at , at . Description The Doña Ana Mountains are a small, rugged mountain range in the desert a few kilometers n ...

are absent from the formation, showing that these mountains had not yet been unroofed during deposition of the formation. The formation has been studied as a model for the critical early stages of

diagenesis Diagenesis () is the process of physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a role as sedi ...

of continental red beds of

Pennsylvanian Pennsylvanian may refer to: * A person or thing from Pennsylvania * Pennsylvanian (geology) The Pennsylvanian ( , also known as Upper Carboniferous or Late Carboniferous) is, on the International Commission on Stratigraphy, ICS geologic timesc ...

Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...

age. and as a model for diagenesis in the Santa Fe Group.

History of investigation

The formation was first defined by Seager ''et al.'' in 1971, and assigned to the Santa Fe Group.

Footnotes

References

* * * * * * * {{cite journal , last1=Walker , first1=Theodore R. , last2=Waugh , first2=Brian , last3=Grone , first3=Anthony J. , title=Diagenesis in first-cycle desert alluvium of Cenozoic age, southwestern United States and northwestern Mexico , journal=GSA Bulletin , date=1 January 1978 , volume=89 , issue=1 , pages=19–32 , doi=10.1130/0016-7606(1978)89<19:DIFDAO>2.0.CO;2, bibcode=1978GSAB...89...19W Neogene formations of New Mexico Conglomerate formations of the United States Mudstone formations of the United States Sandstone formations of the United States