Версия от 04:09, 12 февраля 2024; EducationBot(обсуждение | вклад)(Новая страница: «{{Английская Википедия/Панель перехода}} {{Short description|Geological formation in Oklahoma, U.S.}} {{Lead too short|date=April 2021}} {{Infobox rockunit | image = Homotelus bromidensis fossil trilobites (Bromide Formation, Middle Ordovician; Criner Hills, southeastern Carter County, southern Oklahoma, USA) 4 (15402497771).jpg | period = Upper Ordovician | age = early Sandbian 461–458{{fossil range|461|458| Myo|earliest=...»)
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The Bromide Formation is the uppermost part of the Simpson Group, and originates from the Upper Ordovician (early Sandbian). This mostly carbonate succession is divided into the Mountain Lake and overlying Pooleville members.[1] Although it primarily consists of limestone, limestone interbedded with shale, and sandstone, also occur.[4] The Bromide Formation is a shallow water marine sediment.[5]
Much of the Mountain Lake Member comprises meter-scale, deep ramp cycles that overlie a lowstand systems tract of sandstones and sandy crinoidal grainstones. Cycle tops are starved surfaces with irregular, mineralized hardgrounds. The Pooleville Member consists of an early highstand interval of shallow subtidal carbonates and late highstand peritidal carbonates (Corbin Ranch Submember). Down-ramp, the Pooleville is represented largely by centimeter-thick shales and interbedded lime mudstones.[1]
Economic use
The Bromide Formation has been a source of oil and gas, with exploration slightly north of the area where the formation is exposed.
Файл:Bromide Formation panorama.jpg4×2½ cm of fossil sea floor, from the Bromide Formation. The dark brownish thallus to the left is the green algae Ischadites iowensis, on top of it and to the top of the picture is the pygidium and back part of the thorax of the Corynexochid trilobite Nanillaenus punctatus, to the right is the cephalon of the Harpetid trilobite Dolichoharpes reticulata
Origin
The Bromide Formation was deposited in a shallow, storm-dominated epeiric sea that extended over part of the Laurentiacontinent, in what is today Southern Oklahoma. The sea spread into an area that sunk into a rift, that ultimately did not endure, a so-called aulacogen. Lying approximately at 30° Southern latitude, a low-land desert bordered much of the shallow sea from where well-rounded quartz sand blew in. This now represents the sandstone at the base of the Bromide Formation. Eventually, sea level rise caused by subsidence drowned the borderlands cutting off the supply of sand, and now the shales and limestones of the Middle Bromide (upper Mountain Lake Member) accumulated on a broad ramp. Gradually – primarily echinoderm – skeletons build up a carbonate shelf. Further eustatic sea level rise (transgression) cut off the supply of virtually all sediments from land, and remains of carbonate-producing organisms began filling the basin. This now forms the limestone of the upper Bromide (Pooleville Member). Finally, a drop in sea level (regression) exposed the entire platform, and became a broad, nearly featureless, hot, semi-arid sabkha.[6]
Fossils
Fossils have been found in the Bromide Formation of green algae, sponges, corals, graptolites, lampshells, moss animals, trilobites, clam shrimps, molluscs, several groups of echinoderms, and teeth of jawless fish. The animals we know from the fossil record from many well-known locations (including the Bromide Formation) can be viewed at a website that several paleontological institutions contributed to.[7]
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↑Amsden, T.W. Upper Bromide Formation and Viola Group (Middle and Upper Ordovician in Eastern Oklahoma). Part I – Welling-Fite-Corbin-Ranch-Strata. Oklahoma Geological Survey. Bulletin 132 (1983)[1]
↑Viola Limestone and Bromide Formation. Mineral Resources On-Line Spatial Data. U.S. Geological Survey [2]
↑Longman, M.W. Deposition of the Bromide Formation, Arbuckle Mountains, Oklahoma: Ontogeny of an Ancient Carbonate Shelf. Oklahoma City Geological Society Volume, pp. 268-285 (1982).[3]
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↑Smith, A.B. and J.J. Savill. Bromidechinus, a new Ordovician echinozoan (Echinodermata), and its bearing on the early history of echinoids. Transactions of the Royal Society of Edinburgh: Earth Sciences 92, pp. 137-147 (2001)
