Lake Valley Limestone
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Lake Valley Limestone
The Lake Valley Limestone is a geologic formation widely exposed in southwestern New Mexico. It preserves fossils dating back to the lower to middle Mississippian. Description The Lake Valley Limestone consists of gray cherty limestone with thin shale beds. It overlies the Caballero Formation and is overlain by Pennsylvanian beds. The total thickness is . Members of the formation, in ascending stratigraphic order, are the Andrecito, Alamogordo, Nunn, Tierra Blanca, Arcente, and Dona Ana Members. Fossils The formation contains abundant crinoids as well as corals and brachiopods. The Andrecito and Alamogordo Members contain foraminifers characteristic of the Kinderhookian (lower Tournasian) while the foraminifers of the Tierra Blanca Member are Osagean (upper Tournasian to lower Visean). The formation is notable for the presence of well-developed bioherms. History of investigation The formation was first named by E.D. Cope in 1882 for exposures at Lake Valley, Sierra Count ...
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Formation (stratigraphy)
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 exposed in a geographical region (the stratigraphic column). It is the fundamental unit of lithostratigraphy, the study of strata or rock layers. A formation must be large enough that it can be mapped at the surface or traced in the subsurface. Formations are otherwise not defined by the thickness (geology), thickness of their rock strata, which can vary widely. They are usually, but not universally, tabular in form. They may consist of a single lithology (rock type), or of alternating beds of two or more lithologies, or even a heterogeneous mixture of lithologies, so long as this distinguishes them from adjacent bodies of rock. The concept of a geologic formation goes back to the beginnings of modern scientific geology. The term was used by ...
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Brachiopod
Brachiopods (), phylum (biology), phylum Brachiopoda, are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection. Two major categories are traditionally recognized, articulate and inarticulate brachiopods. The word "articulate" is used to describe the tooth-and-groove structures of the valve-hinge which is present in the articulate group, and absent from the inarticulate group. This is the leading diagnostic skeletal feature, by which the two main groups can be readily distinguished as fossils. Articulate brachiopods have toothed hinges and simple, vertically oriented opening and closing muscles. Conversely, inarticulate brachiopods have weak, untoothed hinges and a more complex system of vertical and oblique (diagonal) muscles used to keep the two valves aligned. In many brachio ...
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List Of Fossiliferous Stratigraphic Units In New Mexico
This article contains a list of fossil-bearing stratigraphic units in the state of New Mexico, New Mexico, U.S. Sites See also * Paleontology in New Mexico References

* {{DEFAULTSORT:Fossiliferous stratigraphic units in New Mexico Fossiliferous stratigraphic units of the United States, New Mexico Paleontology in New Mexico, Stratigraphic units Stratigraphy of New Mexico New Mexico geography-related lists United States geology-related lists ...
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Mogollon-Datil Volcanic Field
The Mogollon-Datil volcanic field is a large () silicic volcanic field in western New Mexico (Mogollon Mountains-Datil, New Mexico). It is a part of an extensive Eocene to Oligocene volcanic event which includes the San Juan volcanic field in southwestern Colorado, the Trans-Pecos Volcanic Field, Trans-Pecos volcanic field in west Texas and north central Mexico, the Boot Heel volcanic field in the bootheel of southwestern New Mexico and adjacent areas of Arizona and Mexico; and the vast volcanic field of the Sierra Madre Occidental of western Mexico. The Mogollon-Datil volcanic field was formed in "four discrete pulses representing synchronized activity of two separate cauldron complexes". Geologic history The volcanic activity of the Mogollon-Datil began near present-day Las Cruces, New Mexico about 36.2 million years ago (mya) with the eruption of the Cueva Tuff from the Organ Caldera. Activity spread to the northwest to the Mogollon caldera by 34.0 mya, and this first pulse o ...
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Porphyry (geology)
Porphyry ( ) is any of various granites or igneous rocks with coarse-grained crystals such as feldspar or quartz dispersed in a fine-grained silicate-rich, generally aphanitic matrix or groundmass. In its non-geologic, traditional use, the term ''porphyry'' usually refers to the purple-red form of this stone, valued for its appearance, but other colours of decorative porphyry are also used such as "green", "black" and "grey". The term ''porphyry'' is from the Ancient Greek (), meaning " purple". Purple was the colour of royalty, and the Roman "imperial porphyry" was a deep purple igneous rock with large crystals of plagioclase. Some authors claimed the rock was the hardest known in antiquity. Thus porphyry was prized for monuments and building projects in Imperial Rome and thereafter. Subsequently, the name was given to any igneous rocks with large crystals. The adjective ''porphyritic'' now refers to a certain texture of igneous rock regardless of its chemical and miner ...
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Monzonite
Monzonite is an igneous intrusive rock, formed by slow cooling of underground magma that has a moderate silica content and is enriched in alkali metal oxides. Monzonite is composed mostly of plagioclase and alkali feldspar. Syenodiorite is an obsolescent term for monzonite or for monzodiorite.Le Maitre, R.W., ''Igneous Rocks: A Classification and Glossary of Terms'' Cambridge University Press, 2nd ed, pp. 113 Larvikite is a particular form of monzonite. Description Monzonite is a coarse-grained ( phaneritic) igneous rock. Such rocks are classified by their relative percentages of quartz, plagioclase, alkali feldspar, and feldspathoid (the QAPF classification). Monzonite is defined as rock having less than 5% quartz in its QAPF fraction and in which alkali feldspar makes up between 35% and 65% of the total feldspar content. If quartz constitutes greater than 5% of the QAPF fraction, the rock is termed a quartz monzonite, while if feldspathoids are present as up to 10% of ...
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Bromargyrite
Bromyrite or bromargyrite is a natural mineral form of silver bromide found mainly in Mexico and Chile. Hardness is 1.5 to 2. Related are chlorargyrite and iodyrite. It was first described in 1859 for an occurrence in Plateros, Zacatecas, Mexico where it occurred in a silver deposit as an oxidation product of primary ore minerals. It occurs in arid environments along with native silver, iodargyrite and smithsonite along with iron and manganese oxide minerals. References

Bromides Silver minerals Halide minerals Cubic minerals Minerals in space group 225 {{Halide-mineral-stub ...
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Chlorargyrite
Chlorargyrite is the mineral form of silver chloride (AgCl). Chlorargyrite occurs as a secondary mineral phase in the oxidation of silver mineral deposits. It crystallizes in the isometric–hexoctahedral crystal class. Typically massive to columnar in occurrence it also has been found as colorless to variably yellow cubic crystals. The color changes to brown or purple on exposure to light. It is quite soft with a Mohs hardness of 1 to 2 and dense with a specific gravity of 5.55. It is also known as cerargyrite and, when weathered by desert air, as horn silver. Bromian chlorargyrite (or embolite) is also common. Chlorargyrite is water-insoluble. It occurs associated with native silver, cerussite, iodargyrite, atacamite, malachite, jarosite and various iron–manganese oxides. It was first described in 1875 for occurrences in the Broken Hill district, New South Wales, Australia. The rich Bridal Chamber deposit at Lake Valley, Sierra County, New Mexico was almost pure chlorargyr ...
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Argentite
In mineralogy, argentite () is cubic silver sulfide (Ag2S), which can only exist at temperatures above , , or . When it cools to ordinary temperatures it turns into its monoclinic polymorph, acanthite. The International Mineralogical Association has decided to reject argentite as a proper mineral. The name "argentite" sometimes also refers to pseudomorphs of argentite: specimens of acanthite which still display some of the outward signs of the cubic crystal form, even though their actual crystal structure is monoclinic due to the lower temperature. This form of acanthite is occasionally found as uneven cubes and octahedra, but more often as dendritic or earthy masses, with a blackish lead-grey color and metallic luster. Argentite belongs to the galena group. Cleavage, which is so prominent a feature in galena, here presents only in traces. The mineral is perfectly sectile and has a shining streak; hardness 2.5, specific gravity is 7.2–7.4. It occurs in mineral veins, and w ...
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Silver
Silver is a chemical element; it has Symbol (chemistry), symbol Ag () and atomic number 47. A soft, whitish-gray, lustrous transition metal, it exhibits the highest electrical conductivity, thermal conductivity, and reflectivity of any metal. Silver is found in the Earth's crust in the pure, free elemental form ("native metal, native silver"), as an alloy with gold and other metals, and in minerals such as argentite and chlorargyrite. Most silver is produced as a byproduct of copper, gold, lead, and zinc Refining (metallurgy), refining. Silver has long been valued as a precious metal. Silver metal is used in many bullion coins, sometimes bimetallism, alongside gold: while it is more abundant than gold, it is much less abundant as a native metal. Its purity is typically measured on a per-mille basis; a 94%-pure alloy is described as "0.940 fine". As one of the seven metals of antiquity, silver has had an enduring role in most human cultures. Other than in currency and as an in ...
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Lake Valley, Sierra County, New Mexico
Lake Valley was a silver-mining town in Sierra County, New Mexico, Sierra County, U.S. state of New Mexico. The 'heyday' of the town was from 1881 to 1893. The last resident departed in 1994. The present day ghost town is deserted. Access The townsite of Lake Valley is partly privately owned, and partly owned by the U.S. Bureau of Land Management, which has restricted access to the old buildings to daylight hours, to prevent vandalism. There is a self-guided walking tour for visitors. The town is closed to the public on Tuesdays and Wednesdays. History A rancher found the Lake Valley silver deposits in Sierra County in 1876. Two years later he sold his claims to an engineer, who began mining. The deposits are bedded ''Manto ore deposits, manto''-type deposits in Lake Valley Limestone, Paleozoic limestone. The mines produced well for a few years after miners tunneled into a silver-lined cavity they named the "bridal chamber" that alone yielded 2.5 million troy ounces (78 to ...
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Bioherm
A reef knoll is a landform that comprises an immense pile of calcareous material that had previously accumulated on an ancient sea floor. Reef knolls are geological remnants of reefs and other organic concentrations of calcareous organisms. Reef knolls are often fossil-rich, with prehistoric corals, sponges, calcareous algae, and other reef-builders contributing to a large portion of the structure's volume. This density of skeletal material allows the structure to withstand sea currents and stand freely. Reef knolls can be divided into bioherms and biostromes. A bioherm is a landform of organic sedimentary rock enclosed or surrounded by rock of different origin. A biostrome is a distinctly bedded or broadly lenticular sedimentary rock landform. Krumbein additionally used these terms to distinguish different shapes of stromatolites: "Distinctly bedded, widely extensive, blanketlike build-ups are biostromes. Nodular, biscuit-like, dome-shaped or columnar stromatolites are also referre ...
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