GeoFacts No. 23 OHIO DEPARTMENT OF NATURAL RESOURCES • DIVISION OF GEOLOGICAL SURVEY A BRIEF SUMMARY OF THE GEOLOGIC HISTORY OF OHIO GEOLOGIC PERIOD1 SETTING LIFE FORMS ROCK TYPES ECONOMIC PRODUCTS (million years ago) Quaternary Two-thirds of Ohio was covered • many large mammals • glacial till, clay, silt, sand, • common clay products (clay) 2.6 mya–Present by mile-thick ice during glacial such as mastodons, gravel • material for road construction periods. mammoths, giant bea- • form the surface sedi- and cement (sand, gravel) vers, and ground sloths, ments in northern and • Sand and gravel are also im- as well as modern plants western Ohio portant aquifers and animals, including humans Mesozoic & Tertiary Ohio was above sea level, and • no known record, but 251–2.6 mya weathering erosion and nonde- dinosaurs probably position prevailed. roamed Ohio during the Mesozoic Permian During early Permian time, • sparse freshwater fossils • sandstone, shale, fresh- • crushed stone (limestone) 299–251 mya southeastern Ohio was a coastal- such as snails, clams, water limestone, coal • electric power (coal) plain swamp. Ohio lay about 5° fi shes • form the surface rocks in north of the Equator. The swamp • marine fossils rare southeasternmost Ohio eventually was fi lled by infl ux • sparse land fossils in- of deltaic sand and mud. Later clude plants, amphib- Permian time was characterized ians, reptiles by uplift and erosion. Pennsylvanian Ohio in Pennsylvanian time was • land plants abundant • sandstone, conglomer- • building stone, crushed stone 318–299 mya a relatively flat coastal-plain • terrestrial and freshwa- ate, shale, clay, limestone, for construction and industrial swamp in equatorial latitudes. ter life included amphib- coal, fl int, ironstone uses such as glass manufactur- Fluctuations in sea level resulted ians, reptiles, freshwater • form the surface rocks in ing, oil and gas (sandstone) in alternating terrestrial, freshwa- clams eastern Ohio • crushed stone for construction ter, and marine deposits. • marine life included and cement (limestone) crinoids, snails, cepha- • pottery and common clay lopods, brachiopods, products (shale, clay) fi shes • electric power (coal) • trilobites rare • during the 1800s Ohio was a major iron-producing state Mississippian During latest Devonian and early • brachiopods, clams, cri- • sandstone, siltstone, • building stone, crushed stone 359–318 mya Mississippian time, dark organic noids, fi shes conglomerate, shale, for construction and industrial muds gave way to fl uvial and • land plants increasingly limestone uses, oil and gas (sandstone) deltaic silts and sands. Ohio lay in abundant • form the surface rocks in • crushed stone for construction equatorial latitudes. During late northwestern and east- and cement (limestone) Mississippian time, a shallow sea central Ohio • common clay products (shale) deposited limy sediments. Dur- • Ohio has been a major producer ing latest Mississippian time the of building stone from the Mis- seas retreated, leaving a sparse sissippian Berea Sandstone for rock record. over 150 years Devonian Most of Ohio was dry land during • coral reefs, bryozoans, • limestone, dolomite, • crushed stone for construction 416–359 mya early Devonian time, although brachiopods, trilobites, shale, sandstone and cement, aglime (limestone the sea still covered eastern Ohio. cephalopods, clams, cri- • form the surface rocks & dolomite) Ohio was in equatorial latitudes. noids, ostracodes in northwestern Ohio, • synfuels and natural gas (shale, During Middle Devonian time, • fi rst major appearance of through central Ohio, sandstone, limestone) warm, shallow seas deposited sharks and bony fi shes and along the Lake Erie limy sediments. Layers of muddy during Middle Devonian shore sediments and some volcanic ash • true land plants appear during late Middle Devonian time signaled renewed volcanic activity and mountain building east of Ohio. During late Devo- nian time, the Ohio sea became stagnant; circulation was poor, and the water was generally anoxic (lacking oxygen). Thick layers of black, organic-rich, uranium-bearing mud were de- posited in these “stinking seas.” continued ➮ GEOLOGIC PERIOD1 SETTING LIFE FORMS ROCK TYPES ECONOMIC PRODUCTS (million years ago) Silurian At the beginning of Silurian • coral reefs abundant, also • limestone, dolomite, • crushed stone for construc- 443–416 mya time, Ohio was dry land subject echinoderms, clams, bra- shale, gypsum tion and cement, aglime, oil to erosion. Then warm, shallow chiopods, cephalopods • form the surface rocks in and gas (limestone, dolomite, seas returned. Ohio lay 20° south western Ohio sandstone) of the Equator. Middle Silurian • salt and sandstone (east- • road salt (salt) seas were deeper and covered ern Ohio) present in the • wallboard (gypsum) Ohio; reef environments were subsurface common. Late Silurian seas were shallower and formed evaporite (salt-bearing) basins in northern Ohio. Ordovician A warm, shallow sea (deeper • bryozoans abundant, • limestone, shale • crushed stone (limestone) 488–443 mya in eastern Ohio) similar to the also brachiopods, cepha- • form the surface rocks in • oil and gas (limestone, shale) Bahamas covered Ohio, which lopods, trilobites, horn southwestern Ohio • in 1884 the fi rst giant U.S. oil lay 20° south of the Equator. The corals, snails, clams, • dolomite in subsurface fi eld was discovered in Ordo- western part of Ohio, at times, echinoderms, graptolites vician rocks in northwestern emerged as low muddy islands. • Ohio is world famous for Ohio Limy sediments were dominant. its fossiliferous Ordovi- • limestone in the Cincinnati Volcanic activity and mountain cian rocks in the Cincin- area formerly was a source of building to the east of Ohio pro- nati area building stone duced periodic layers of ash over the entire state and muddy deltaic sediments in eastern Ohio. The sea deepened during later Or- dovician time, covering all of the state. At the close of Ordovician time, continental glaciation in the southern hemisphere lowered sea level and the seas retreated. Cambrian Marine seas gradually fl ooded • marine life abundant, but • sandstone, shale, do- • oil and gas (sandstone, do- 542–488 mya the Precambrian land surface and few fossils known from lomite lomite) covered Ohio by late Cambrian Ohio because knowledge • present in subsurface time, initially depositing sands, is limited to core samples only then silts, muds, and limy muds. • trilobites reached their Ohio lay 10° south of the Equa- peak diversity during tor. Toward the end of Cambrian the late Cambrian time, limy sediments accumu- lated in a shallow marine sea in an arid climate. Precambrian Between 1.4 and 990 million years • none known from Ohio • igneous, metamorphic, • no current production 4.6 billion–542 mya ago, volcanic activity, crustal rift- • algae and lower inver- and metasedimentary ing, and fi lling of basins formed tebrates found in areas rocks by rifting took place. Between other than Ohio • present only at great 990 and 880 million years ago, depths—2,500 to 13,000 a mountain range formed in feet beneath the surface eastern Ohio. Between 880 and 544 million years ago, these mountains were eroded, reduc- ing the landscape to a gently rolling surface. 1Time assignments are based on U.S. Geological Survey Fact Sheet 2010-3059, Division of Geologic Time—Major Chronostratigraphic and Geochronologic Units, 2010, available at <http://pubs.usgs.gov/fs/2010/3059/>. • This GeoFacts compiled by staff of Division of Geological Survey • Revised June 2014 • paper The Division of Geological Survey GeoFacts Series is available on the World Wide Web: www.OhioGeology.com recycled STATE OF OHIO OF NATURAL RESOURCES OHIO DEPARTMENT GEOLOGICAL SURVEY DIVISION OF.