The Bromide Formation is a

geological 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 expo ...

in Oklahoma, USA. It is well known for its diverse

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the s ...

and

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the ...

fossil 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 ...

fauna Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is ''flora'', and for fungi, it is '' funga''. Flora, fauna, funga and other forms of life are collectively referred to as ''biota''. Zoo ...

Location

The Bromide Formation crops out in the Arbuckle and

Wichita Mountains The Wichita Mountains are located in the southwestern portion of the U.S. state of Oklahoma. It is the principal relief system in the Southern Oklahoma Aulacogen, being the result of a failed continental rift. The mountains are a northwest-southe ...

and in the

Criner Hills Criner is a surname. Notable people with the surname include: * Jim Criner (born 1940), American football player and coach * Juron Criner (born 1989), American football player * Laurence Criner (fl. 1926-1950), American actor * Mark Criner (born 19 ...

of Southern Oklahoma. It appears at the surface in particular within Carter, Johnston,

Murray Murray may refer to: Businesses * Murray (bicycle company), an American manufacturer of low-cost bicycles * Murrays, an Australian bus company * Murray International Trust, a Scottish investment trust * D. & W. Murray Limited, an Australian whole ...

and Pontotoc counties (34.0° N, 97.0° W).

Stratigraphy

The Bromide Formation is the uppermost part of the Simpson Group, and originates from the

Upper Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. Th ...

(early

Sandbian The Sandbian is the first stage of the Upper Ordovician. It follows the Darriwilian and is succeeded by the Katian. Its lower boundary is defined as the first appearance datum of the graptolite species '' Nemagraptus gracilis'' around million ye ...

). This mostly

carbonate A carbonate is a salt of carbonic acid (H2CO3), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word ''carbonate'' may also refer to a carbonate ester, an organic compound containing the carbonat ...

succession is divided into the Mountain Lake and overlying Pooleville members. Although it primarily consists of

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

, limestone interbedded with

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especia ...

, and

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates ...

, also occur. The Bromide Formation is a shallow water

marine sediment Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles have their origins in soil and rocks and have been transported from the land to the sea, mai ...

.Bauer, J.A. Conodonts from the Bromide Formation (Middle Ordovician), South-Central Oklahoma. Journal of Paleontology 68-2 (1994). Much of the Mountain Lake Member comprises meter-scale, deep ramp cycles that overlie a lowstand systems tract of sandstones and sandy crinoidal

grainstone Under the Dunham classification (Dunham, 1962) system of limestones, a grainstone is defined as a grain-supported carbonate rock that contains less than 1% mud-grade material. This definition has recently been clarified as ''a carbonate-dominat ...

s. 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.

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.

Origin

The Bromide Formation was deposited in a shallow, storm-dominated

epeiric sea An inland sea (also known as an epeiric sea or an epicontinental sea) is a continental body of water which is very large and is either completely surrounded by dry land or connected to an ocean by a river, strait, or "arm of the sea". An inland s ...

that extended over part of the

Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, althoug ...

continent A continent is any of several large landmasses. Generally identified by convention rather than any strict criteria, up to seven geographical regions are commonly regarded as continents. Ordered from largest in area to smallest, these seven ...

, in what is today Southern Oklahoma. The sea spread into an area that sunk into a

rift In geology, a rift is a linear zone where the lithosphere is being pulled apart and is an example of extensional tectonics. Typical rift features are a central linear downfaulted depression, called a graben, or more commonly a half-grabe ...

, that ultimately did not endure, a so-called

aulacogen An aulacogen is a failed arm of a triple junction. Aulacogens are a part of plate tectonics where oceanic and continental crust is continuously being created, destroyed, and rearranged on the Earth’s surface. Specifically, aulacogens are a rift ...

. 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 Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cry ...

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 Globally, sea levels are rising due to human-caused climate change. Between 1901 and 2018, the globally averaged sea level rose by , or 1–2 mm per year on average.IPCC, 2019Summary for Policymakers InIPCC Special Report on the Ocean and Cryo ...

(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 A sabkha ( ar, سبخة) is a coastal, supratidal mudflat or sandflat in which evaporite-saline minerals accumulate as the result of semiarid to arid climate. Sabkhas are gradational between land and intertidal zone within restricted coastal p ...

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.

Green algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ( Embryophytes) have emerged deep in the Charophyte alg ...

*''Ischadites iowensis''Amsden, T.W. Catalogue of Fossils from the Middle and Upper Ordovician of Oklahoma. Oklahoma Geological Survey, Circular 43. 1957

Sponges Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate throug ...

*''Dierespongia palla''

Corals Corals are marine invertebrates within the class Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secre ...

*''Saffordophyllum deckeri'' *''Tetradium oklahomense'' *''Tetradium spicululatum''

Graptolites Graptolites are a group of colonial animals, members of the subclass Graptolithina within the class Pterobranchia. These filter-feeding organisms are known chiefly from fossils found from the Middle Cambrian (Miaolingian, Wuliuan) through the L ...

*''Dicellograptus gurlei'' *''Dictyonema francesiae'' *''Dictyonema rockcrossingensis'' *''Diplograptus (Amplexograptus) maxwelli''

Lampshells

*''Acanthocrania erecta'' (mountain lake member?) *''Acanthocrania oklahomensis'' (pooleville member) *''Acanthocrania subquadrata'' (mountain lake member) *''Ancistorhyncha costata'' (corbin branche member)Fossil collection of Geological Enterprises, Ardmore, OK, USA *''Ancistorhyncha globularis'' (pooleville member) *''Athelelasma oklahomense'' (mountain lake member) *''Bellimurina compressa'' (mountain lake member) *''Bellimurina subquadrata'' (mountain lake member) *''Camerella anteroplicata'' (pooleville member) *''Camerella oklahomensis'' (pooleville member) *''Chaulistomella crassa'' (mountain lake member) *''Chaulistomella magna'' ''Dinorthis subquadrata'' ''Valcourea magna''(pooleville member) *''Chaulistomella mira'' (mountain lake member) *''Chaulistomella mundula'' (mountain lake member) *''Chaulistomella nitens'' (mountain lake member) *''Chaulistomella obesa'' (mountain lake member) *''Cliftonia occidentalis'' *''Craniops tenuis'' (pooleville member) *''Cyclospira parva'' (pooleville member) *''Dactylogonia sculpturata parva'' (mountain lake member) *''Dactylogonia subaequicostellata'' (mountain lake member) *''Doleroides compressus'' (mountain lake member) *''Doleroides oklahomensis'' (pooleville member) *''Ectenoglossa cf. sculpta'' (pooleville member) *''Fascifera dalmanelloidea'' (mountain lake member) *''Glossella liumbona'' (pooleville member) *''Glyptorthis costellata'' (pooleville member) *''Glyptorthis crenulata'' (pooleville member) *''Glyptorthis obesa'' (mountain lake member) *''Glyptorthis uncinata'' (mountain lake member) *''Hesperorthis crinerensis'' (mountain lake member) *''Hesperorthis sulcata'' (pooleville member) *'' Lingulella galba'' (mountain lake member) *''Lingulella cf. glypta'' (pooleville member) *''Lingulasma oklahomense'' (pooleville member) *''Macrocoelia bella'' (mountain lake member) *''Mimella extensa'' (mountain lake member) *''Mimella subquadrata'' (mountain lake member) *''Multicostella sulcata'' (mountain lake member) *''Murinella partita'' (mountain lake member) *''Onychoplecia tenuis'' (mountain lake member) *''Oepikina sp.'' *''Oepikina expatiata'' (mountain lake member) *''Oepikina extensa'' (pooleville member) *''Oepikina formosa'' (pooleville member) *''Oepikina gregaria'' (mountain lake member) *''Orbiculoidea eximia'' (pooleville member) *''Orthis tricrenata'' *''Oxoplecia filosa'' (mountain lake member) *''Oxoplecia gouldi'' (pooleville member) *''Oxoplecia occidentalis'' *''Pachyclossa biconvexa'' (pooleville member) *''Paurorthis macrodeltoidea'' (pooleville member) *''Petrocrania sp.'' (mountain lake member) *''Petrocrania inflata'' (pooleville member) *''cf. Philhedra sp.'' (mountain lake member) *''Platymena cf. bellatula'' (pooleville member) *''Plectorthis symmetrica'' *''Protozyga costata'' (pooleville member) *''Protozyga elongata'' (mountain lake member) *''Protozyga loeblichi'' (pooleville member) *''Protozyga magnicostata'' (mountain lake member) *''Pseudolingula imperfecta'' *''Oepikina minnesotensis'' ''Rafinesquina minnesotensis''ref name="Amsden"/> *''Rostricellula sp.'' (pooleville member) *''Rostricellula cuneata'' (mountain lake member) *''Rostricellula parva'' (pooleville member) *''Rostricellula transversa'' (pooleville member) *''Schizambon perspinosum'' (mountain lake member) *''Skenidoides oklahomensis'' (mountain lake member) *''Sowerbyella sp.'' (mountain lake member) *''Sowerbyella indistincta'' (mountain lake member) *''Sowerbyella plicatifera'' (mountain lake member) *''Sowerbyella variabilis'' (pooleville member) *''Sowerbyella vulgata'' (mountain lake member) *''Sowerbyites hami'' (pooleville member) *''Sowerbyites lamellosus'' (mountain lake member) *''Spirifer perlamellosus'' *''Strophomena costellata'' (pooleville member) *''Strophomena crinerensis'' (pooleville member) *''Strophomena oklahomensis'' (pooleville member) *''Valcourea transversa'' (mountain lake member)

Moss animals

*''Anolotichia deckeri'' *''Anolotichia impolita'' *''Anolotichia spinulifera'' *''Atactoporella bellula'' *''Batostoma chapparsi'' *''Batostoma cumingsi'' *''Batostoma winchelli'' *''Dekayella praenuntia'' echinata *''Eridotrypa abrupta'' *''Fistulipora cf. bassleri'' *'' Hallopora dubia'' *''Hallopora macrostoma'' *''Hallopora pachymura'' *''Hemiphragma irrasum'' *''Hemiphragma pulchrum'' *''Heterotrypa taffi'' *''Homotrypa callitoecha'' *''Homotrypa multitabulata'' *''Homotrypa sagittata''

*''Homotrypa ulrichi'' *''Mesotrypa favosa'' *''Mesotrypa tubulifera'' *''Monticuliporella croneisi'' *''Monticuliporella peculiaris'' *''Monticuliporella shideleri'' *''Nicholsonella irregularis'' *''Nicholsonella laminata'' *''Nicholsonella moniliformis'' *''Pachydictya bromidensis'' *''Prasopora fritzae'' *''Stromatotrypa frondosa''

Arthropods Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, oft ...

Trilobites Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the ...

*''Amphilichas subpunctatus''Shaw, F.C. Simpson Group (Middle Ordovician) Trilobites of Oklahoma. Journal of Paleontology 48-5, Memoir 6, Part II (1974

/ref> *''Apianurus sp.'' *''Bumastoides milleri'' *'' Bumastus sp.'' *''Calliops armatus'' *''Calliops divaricatus'' *''Calyptaulax annulata'' (Mountain Lake Member) *''Ceratocephala graffhami'' *'' Ceraurus ruidus'' ''Eoceraurus trapezoidalis''ref name="Shaw"/> *''Cybeloides sp.'' *''Dolichoharpes reticulata'' ''procliva''ref name="Shaw"/> *''Estoniops? divaricatus'' *''Failleana sp.'' *''Frencrinuroides capitonis'' ''Encrinuroides capitonis''ref name="Shaw"/> *''Harpillaenus sp.'' *'' Illaenus americanus'' *''Isoteloides sp.'' *'' Isotelus gigas'' *'' Lonchodomas mcgeheei'' *''Nanillaenus punctatus'' *''Otarion sp.'' *''Pandaspinapyga salsa'' *''Pliomerops canadensis'' (Mountain Lake Member) *''Probolichas sp.'' *''

Remopleurides ''Remopleurides'' is an extinct genus of trilobites. References External links''Remopleurides''at the Paleobiology Database Remopleurididae Asaphida genera Ordovician trilobites of North America Ordovician trilobites of Asia Ordovic ...

sp.'' *''

Sphaerocoryphe ''Sphaerocoryphe'' is a genus of trilobite that lived from the middle Ordovician to the Silurian. Its fossils have been found in Australia, Europe, and North America. Both ''Sphaerocoryphe'' and '' Hemisphaerocoryphe'' had a characteristically ...

sp.'' *''Thaleops jaanussoni'' (Mountain Lake Member) *''Vogdesia bromidensis'' Shaw 1974 (Esker 1964) ''Homotelus bromidensis''(Mountain Lake Member)

Clam shrimps

*''Bromidella reticulata'' *''Bythocypris cylindrica'' *''Cryptophyllus oboloides'' *''Dicranella bicornis'' *''Eridoconcha magna'' *''Eridoconcha simpsoni'' *''Eurychilina reticulata'' *''Eurychilina ventrosa'' *''Halliella labiosa'' *''Krausella arcuata'' *''Leperditella cf. deckeri'' *''Leperditella inflata'' *''Primitiopsis bassleri'' *''Schmidtella umbonata'' *''Ulrichia initialis''

Molluscs Mollusca is the second-largest phylum of invertebrate animals after the Arthropoda, the members of which are known as molluscs or mollusks (). Around 85,000 extant species of molluscs are recognized. The number of fossil species is esti ...

*''Helicotoma umbilicata'' *''Liospira vitruvia'' *''Aristerella nitidula''

Echinoderms An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the ...

Sea urchins and sand dollars

*''Bromidechinus rimaporus'' (Pooleville Member)

Edrioasteroids

*''Cyathocystus oklahomae''

Cystoids

*''Amygdalocystites tribranchiatus'' *''Anthracocrinus primitivus'' *''Cheirocrinus ardmorensis'' *''Cheirocrinus cf. loeblichi'' *''Echinoencrinites cf. ornatus'' *''Enoploura cf. papillata'' *''Eumorphocystus multiporata'' *''Glyptocytites loeblichae'' *''Glyptocytites logani'' *''Hesperocystus deckeri'' *''Myeinocytites natus'' *''Oklahomacystus tribranchiatus'' *''Pararchaeocrinus decoratus'' *''Platycystites bassleri'' *''Platycystites bromidensis'' *''Platycystites cristatus'' *''Platycystites fimbratus'' *''Platycystites levatus'' *''Pleurocytites watkinsi'' *''Quadrocystis graffhami'' *''Synclairocytis angulatus'' *''Synclairocytis sulphurensis'' *''Tanaocystis watkinsi'' *''Traskocrinus sp.''

Sea lilies Crinoids are marine animals that make up the class Crinoidea. Crinoids that are attached to the sea bottom by a stalk in their adult form are commonly called sea lilies, while the unstalked forms are called feather stars or comatulids, which ar ...

*''Annulocrinus ramifer''Brower, J.C. Calceocrinoids from the Bromide Formation (Middle Ordovician) of Southern Oklahoma. Oklahoma Geological Survey, Circular 78 (197

/ref> *''Archaeocrinus subovalis'' *''Calceocrinus longifrons'' *''Carabocrinus treadwelli'' *''Euptychocrinus skopaios'' *''Hybocrinus crinerensis'' *''Hybocrinus nitidus'' *''Hybocrinus pyxidatus'' *''Palaeocrinus hudsoni'' *''Paracremacrinus laticardinalis''

Chordata, Chordates

Teeth of jawless fish (conodonts)

*'' Ansella crassa'' Bauer 1994 *''Ansella nevadensis'' (Ethington and Schumacher) *''

Baltoniodus ''Baltoniodus'' is an extinct genus of conodonts. Use in stratigraphy The base of the Dapingian, the third stage of the Middle Ordovician, is defined as the first appearance of ''Baltoniodus triangularis''. The Whiterock Stage refers mainly t ...

gerdae'' (Bergström) *'' Bryantodina aequalis'' Bauer 1994 *'' Cahabagnathus sweeti (Bergström) *'' Cardiodus abbreviatus'' *''Cardiodus densus'' *''Cardiodus robustus'' *''

Cordylodus ''Cordylodus'' is an extinct genus of conodonts in the family of Cordylodontidae. Use in stratigraphy It is suggested that ''Cordylodus andresi'' can be a marker of the Cambrian Stage 10. Distribution Fossils of ''Cordylodus'' have been ...

sp.'' *'' Curtognatus sp.'' *''Curtognatus cordiformis'' *''Curtognatus coronata'' *''Curtognatus limitaris'' *'' Eoplacognathus elongatus'' (Bergström) *'' Erismodus typus'' Branson and Mehl *''cf. Leptochirognatus sp.'' *'' Leptochirognatus extensa'' *''cf. Microcoelodus sp.'' *'' Microcoelodus asymmetricus'' *''Microcoelodus inornatus'' *''Microcoelodus intermedius'' *''Microcoelodus minutidentatus'' *''Microcoelodus typuis'' *'' Oneotodus? ovatus'' (Stauffer) *'' Oistodus suberectus'' *'' Pharagmodus ambiguus'' Bauer 1994 *''Phragmodus flexuosus'' *'' Plectodina edentula'' Bauer 1994 *'' Polycaulodus bidentatus'' *''Polycaulodus tridentatus'' *'' Staufferella falcata'' (Stauffer) *'' Trichognatus obtusa'' *''Trucherognatus distorta'' *''Trucherognatus irregularis'' *'' Walliserodus declivis'' Bauer 1994

References

{{Reflist Ordovician System of North America Ordovician geology of Oklahoma Geologic formations of Oklahoma Paleontology in Oklahoma Ordovician southern paleotropical deposits