The Trinidad Sandstone is a geologic formation in northeastern New Mexico and southeastern Colorado . It was formed during the Campanian Age of the Cretaceous Period and contains fossils.
6-590: The Trinidad Formation consists of a massive fine- to very fine-grained arkosic sandstone some 70–300 feet (21–91 m) in thickness. It rests conformably on the Pierre Shale and is in turn conformably overlain by the Vermejo Formation . The formation is interpreted as shore deposits marking the final regression of the Western Interior Seaway from northeastern New Mexico. It is correlative with
12-488: A sand). These sediments must be deposited rapidly and/or in a cold or arid environment such that the feldspar does not undergo significant chemical weathering and decomposition; therefore arkose is designated a texturally immature sedimentary rock. Arkose is often associated with conglomerate deposits sourced from granitic terrain and is often found above unconformities in the immediate vicinity of granite terrains. The central Australian inselberg Uluru (Ayers Rock)
18-476: Is typically grey to reddish in colour. The sand grains making up an arkose may range from fine to very coarse, but tend toward the coarser end of the scale. Fossils are rare in arkose, due to the depositional processes that form it, although bedding is frequently visible. Arkose is generally formed from the weathering of feldspar-rich igneous or metamorphic , most commonly granitic, rocks , which are primarily composed of quartz and feldspar (called ' grus ' as
24-773: The Fox Hills Sandstone and the Pictured Cliffs Sandstone . The formation contains trace fossils of Ophiomorpha and, in a few locations, Diplocraterion . "Ladders" of Diplocraterion are over 1 meter (3.3 ft) long in the lower part of the formation at Cerrososo Canyon. There is potential for natural gas extraction from the Trinidad Sandstone. The gas originates in interbedded coal formations. The beds making up this unit were originally included in Hayden 's Raton Hills group in 1869. The name, Trinidad,
30-403: The potential precursor of arkose. Quartz is commonly the dominant mineral component, and some mica is often present. Apart from the mineral content, rock fragments may also be a significant component. Arkose usually contains small amounts of calcite cement, which causes it to effervesce (fizz) slightly in dilute hydrochloric acid ; sometimes the cement also contains iron oxide . Arkose
36-407: Was first applied by R.C. Hills in 1899, and W.T. Lee (1917) further refined the definition to include only Hills' "Upper Trinidad". Arkosic Arkose ( / ˈ ɑːr k oʊ s , - k oʊ z / ) or arkosic sandstone is a detrital sedimentary rock , specifically a type of sandstone containing at least 25% feldspar . Arkosic sand is sand that is similarly rich in feldspar, and thus
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