The Palm Park 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 ...

in southern

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 preserves

fossils A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

dating back to 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 ...

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 formation consists of reddish

clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks by ...

sediments Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

, including some beds of boulder conglomerate with individual boulders up to in diameter. The red color is attributed to a

source Source may refer to: Research * Historical document * Historical source * Source (intelligence) or sub source, typically a confidential provider of non open-source intelligence * Source (journalism), a person, publication, publishing institute ...

in the

Abo Formation The Abo Formation is a geologic formation in New Mexico. It contains fossils characteristic of the Cisuralian epoch of the Permian period. Description The Abo Formation consists of fluvial redbed mudstones and sandstones, including river channel ...

. The upper beds contains considerable

latite Latite is an igneous, volcanic rock, with aphanitic- aphyric to aphyric-porphyritic texture. It is the volcanic equivalent of monzonite. Its mineral assemblage is usually alkali feldspar and plagioclase in approximately equal amounts. Quartz is ...

andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...

breccia Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix. The word has its origins in the Italian language ...

interbedded with

tuffaceous Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...

claystone Mudrocks are a class of fine-grained siliciclastic sedimentary rocks. The varying types of mudrocks include siltstone, claystone, mudstone and shale. Most of the particles of which the stone is composed are less than and are too small to ...

and

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

. The Palm Park Formation rests gradationally on the Love Ranch Formation, is

unconformably An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval o ...

overlain by the Bell Top Formation,

Rincon Valley Formation The Rincon Valley Formation is a Formation (geology), geologic formation found in the Rincon Valley (New Mexico), Rincon Valley of New Mexico. It preserves fossils dating back to the Miocene Epoch (geology), epoch and records a time when the val ...

, or Santa Fe Group, and has a thickness of about . The original age estimate, based on radiometric ages of

intrusions In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of Intrusive rock, intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety o ...

and interbedded flows, ranged from 42 to 51 million years. More recent high-precision U-Pb dating gives an age of 45.0±0.7 Ma for an ash fall

tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...

in the lower part of the formation in the

Robledo Mountains The Robledo Mountains are a mountain range in Doña Ana County, New Mexico, just northwest of Las Cruces. They are an uplifted block of Paleozoic rocks on the west side of the Rio Grande Rift. The range was named for Pedro Robledo, who died o ...

and an age of 39.6±0.5 Ma for an ash fall tuff in the upper part of the formation in the Sierra de las Uvas. The interbedded ash fall tuffs and

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 ...

beds of the formation are interpreted as volcanic activity after the end of Laramide mountain building but before the opening of the

Rio Grande Rift The Rio Grande rift is a north-trending continental rift zone. It separates the Colorado Plateau in the west from the interior of the North American craton on the east. The rift extends from central Colorado in the north to the state of Chihuah ...

. At this time, the remnants of the Farallon Plate began to sink into the deep mantle and hot mantle rock rose to take their place, triggering the Mid-Tertiary ignimbrite flare-up.

Fossils

The Palm Park Formation contains hot-water

stromatolite Stromatolites ( ) or stromatoliths () are layered Sedimentary rock, sedimentary formation of rocks, formations (microbialite) that are created mainly by Photosynthesis, photosynthetic microorganisms such as cyanobacteria, sulfate-reducing micr ...

s. Stable oxygen isotope measurements show that the fine layers (laminae) making up the stromatolites were deposited seasonally, with the sparry (coarsely crystalline) layers deposited in the spring and summer, and the micritic (fine-grained) layers deposited in the fall and winter. This suggests that laminae in more ancient stromatolites are also seasonal in nature. The formation also contains Eocene fossil

vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

Chadronian The Chadronian is a North American Land Mammal Age typically set from around 37,000,000 to 33,700,000 years BP, a period of . The Chadronian is preceded by the Duchesnean and followed by the Orellan NALMA stages. Relative to global geological c ...

age. These are found in deeply weathered

beds of the middle and upper part of the formation that are interbedded with plant- and

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

-bearing

travertine Travertine ( ) is a form of terrestrial limestone deposited around mineral springs, especially hot springs. It often has a fibrous or concentric appearance and exists in white, tan, cream-colored, and rusty varieties. It is formed by a process ...

s, and most are also badly weathered. However, they include shell fragments of the tortoise '' Stylemys'', jaw fragments of ''

Hyaenodon ''Hyaenodon'' ("hyena-tooth") is an Extinction (biology), extinct genus of Carnivore, carnivorous Placentalia, placental mammals from extinct tribe Hyaenodontini within extinct subfamily Hyaenodontinae (in extinct Family (biology), family Hyaenod ...

horriblis'', tooth fragments likely of ''

Hyracodon ''Hyracodon'' ('hyrax tooth') is an extinct genus of perissodactyl mammal. It was a lightly built, pony-like mammal of about 1.5 m (5 ft) long. ''Hyracodons skull was large in comparison to the rest of the body. ''Hyracodon's'' dentiti ...

'', and a partial skeleton of a protoceratid.

Economic geology

Barite Baryte, barite or barytes ( or ) is a mineral consisting of barium sulfate (Ba S O4). Baryte is generally white or colorless, and is the main source of the element barium. The ''baryte group'' consists of baryte, celestine (strontium sulfate), ...

galena Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver. Galena is one of the most abundant and widely distributed sulfide minerals. It crysta ...

manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...

deposits are present in the Palm Park Formation in the Rincon basin. These had produced 10,520 tons of barite and 1529 tons of 27%-40% manganese ore by 1998. The formation also contains

gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate Hydrate, dihydrate, with the chemical formula . It is widely mined and is used as a fertilizer and as the main constituent in many forms of plaster, drywall and blackboard or sidewalk ...

and travertine, but not in economic amounts for the 1998 market.

History of investigation

The formation was first named by V.C. Kelley and

Caswell Silver Caswell Silver (June 25, 1916 – October 18, 1988) was an American geologist and entrepreneur who was President of Sundance Oil Company from 1960 to 1984. In addition to the business of oil and gas exploration, he was active in the American Assoc ...

in 1952 for exposures in Palm Park, southeast of Caballo. Because no complete section exists, a type locality was designated instead of a

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 ...

. Steven M. Cather and his coinvestigators assigned the Palm Park Formation to the Spears Group in 1994.

Footnotes

References

* * * * * * * * * * {{cite journal , last1=Seager , first1=William R. , last2=Mack , first2=Greg H. , last3=Raimonde , first3=Michael S. , last4=Ryan , first4=Ronald G. , year=1986 , title=Laramide basement-cored uplift and basins in south-central New Mexico , journal=New Mexico Geological Society Field Conference Series , volume=37 , pages=123–130 , url=https://nmgs.nmt.edu/publications/guidebooks/downloads/37/37_p0123_p0130.pdf , accessdate=26 August 2020 Paleogene formations of New Mexico Conglomerate formations of the United States Siltstone formations of the United States

Description

Fossils

Economic geology

History of investigation

See also

Footnotes

References