The St. Clair Limestone is a geologic unit in Arkansas, and Oklahoma. It is classified as a Geologic Member in Indiana and Missouri. It dates back to the Middle of Silurian period. It is high density, high magnesium dolomitic limestone. It was originally classified as a marble in Oklahoma due to the fact that it would hold a high polish, hence Marble City. It is sold in slabs and as tiles, in a similar manner as marble would be. This unit has many economic uses in Arkansas and Oklahoma. It is used as a construction material, manufacture of quicklime, and manganese deposits are mined as well. The St Clair is designated as a member of the Bainbridge Group in the State of Indiana. In Illinois, Missouri, Arkansas and Oklahoma it is part of the Hunton Megagroup. The St. Clair is the Basal member of the Niagaran Series, making it part of the Tippecanoe sequence. Throughout most of the Southern extent the unit is roughly 10 to 20' thick. Moving northward it thickens to approximately 80 to 100' thick in the Illinois Basin. At its northernmost reaches where it grades in to the Joliet and Racine Formations it is about 150' thick.
Appearance The St. Clair is composed of course calcite grains to fine grains. It may contain partings of claystone or Mudstone. It can range in color from light-gray to chocolate brown, or even or purplish-black. Beds of pink crinoid remains are also found with in this unit, mostly toward the base.
Physical characteristics
Imperial MetricAbsorption by weightASTM C970.5%0.5%DensityASTM C97168 lb/ft32 691.10 kg/m3Compressive strengthASTM C17015 889Psi109.55MPaModulus of ruptureASTM C99972Psi6.70MPa
Paleofauna
Brachiopods Source:
Ancillotoechia A. marginata Antirhynchonella A. thomasi Atrypa Atrypina A. erugata Boucotides B. barrandei Brachymimulus B. americanus B. elongatus Cymostrophia Dicamaropsis D. parva Dicoelosia D. bilobella
Dolrorthis D. nanella Eospirifer E. acutolineatus acutolineatus E. acutolineatus pentagonus Hircinisca H. havliceki Homoeospirella H. costatula arkansana H. pygmaea Howellella H. splendens Kozlowskiellina K. vaningeni Leangella L. (Opikella) dissiticostella Leptaena
Lissostrophia Meristina M. clairensis Nanospira N. clairensis Nucleospira N. raritas Onychotreta O. angustata O. lenta O. (Eilotreta) miseri O. multiplicata O. (Lissotreta) plicata Orthostrophella O. clairensis Oxoplecia O. infrequens
Parastrophinella P. lepida Placotriplesia P. juvenis P. praecipta Plectatrypa P. arctoimbricata Plectodonta Plicocyrtia P. arkansana Resserella Shaleria Streptis S. glomerata Virginiata V. arkansana
Conodonts Source:
Acodus A. inornatus A. unicostatus Ambalodus A. triangularis Belodella B. flexa Belodina B. inclinata Carniodus C. carnulus C. carnus Cordylodus C. delicatus C. flexuosus
Distacodus D. mehli D. posterocostatus> D. procerus Distomodus D. kentuckyensis Drepanodus D. homocurvatus Hadrognathus H. staurognathoides Hindeodella H. equidentata Ligonodina L. egregia L. silurica
Neoprioniodus N. costatus N. excavatus N. multiformis N. subcarnus Oistodus O. inclinatus Ozarkodina O. gaertneri O. inclinata O. media O. ziegleri Paltodus P. multicostatus P. trigonius
Panderodus P. gracilis P. simplex P. unicostatus Plectospathodus P. extensus Pterospathodus P. amorphognathoides Spathognathodus S. ranuliformis S. rhenanus S. wolfordi Trichonodella T. brassfieldensis T. carinata T. exacta T. variflexa
Trilobites Source:
Ananaspis Balizoma Cheirurus C. phollikodes C. prolixus Cornuporoetus C. kyphora Dalmanites D. howelli D. ptyktorhion
Decoroproetus D. anaglyptus D. corycoeus Deiphon D. longifrons Delops Diacalymene D. altirostris Encrinurus E. egani
Eophacops E. fontana Harpidella H. butorus H. spinulocervix Lepidoproetus L. (Dipharangus) xeo Proetidae Proetus P. vaningeni
Radnoria Raphiophorus R. niagarensis Sphaerexochus S. glaber Staurocephalus S. lagena S. oarion Sthenarocalymene S. scutula Tropidocoryphinae
References