Kentucky Geological Survey James C. Cobb, State Geologist and Director MAP AND CHART 200 UNIVERSITY OF , LEXINGTON Kentucky Landscapes Through Geologic Time XII, 2011 Daniel I. Carey

Introduction The Period Since Kentucky was covered by shallow The MississippianEarly Period 356 Ma Many types of lived in Kentucky during the ; some had teeth for We now unders tand that the ’s crust is broken up into a number of tropical seas du ring most of the Ordovician capturing swimming and others had teeth especially adapted for crushing and During most of the Ordovician, Kentucky was covered by shallow, tropical seas Period (Figs. 6–7), the found in Sea Floor eating shellfish such as , clams, , and (Fig. 23). plates, some of continental size, and that these plates have been moving— (Fig. 4). , dolomites, and were formed at this time. The oldest rocks Kentucky's Ordovician rocks are marine (sea- Spreading Ridge centimeters a —throughout geologic history, driven by the internal heat exposed at the surface in Kentucky are the hard limestones of the Camp Nelson dwelling) . Common Ordovician bryozoan crinoid, Culmicrinus horn PANTHALASSIC Ural Mts. Kazakstania of the earth. This movement creates our mountain chains, earthquakes, (Middle Ordovician age) (Fig. 5), found along the gorge in fossils found in Kentucky include (of North crinoid, crinoid, central Kentucky between Boonesboro and Frankfort. Older rocks are present in the Rhopocrinus geologic faults, and volcanoes. The theory of (from the Greek, the Porifera), corals (phylum ), , PALEO- South China Rhopocrinus subsurface, but can be seen only in drill cuttings and cores acquired from oil and gas tektonikos: pertaining to building) attemp ts to describe the process and helps bryozoans, brachiopods (Fig. 8), , snails straight TETHYS large drilling and mineral exploration. Later in Ordovician time, the seas became relative ly EURAMERICA OCEAN crinoid (phylum ), clams (phylum Pelecy- shelled explain the of Kentucky. shallow, indicated by mud and in the . When the waters were clear and stem poda), -like animals (phylum Cephalo- Kentucky Appalachian Malaya bryozoan, Mts. Variscan Mts. The geologic story of the rocks that form Kentucky’s landscape began a half warm, a profusion of flourished, particularly brachiopods and . poda), crinoids (of the class Echinodermata), Arabia billion ago when the area was covered by water. Deposits of sand, silt, These became the rich beds that have attracted amateur and professional crinoid, and ostracodes and . Straight-shelled Pulaskicrinus t ec oj paleontologists to the beds, rocky hillsides, and roadcuts of the Bluegrass r P AP clay, and lime muds in shallow seas, deltas, swamps, and river systems (squid-like cephalopods), shown in M O LE PA e, tes crinoid, Region. co brachiopods . S R C. Figure 9(a), are common fossils in the Bluegrass 00 accumulated over the next 250 million years, layer upon layer. As each layer 20 © Camptocrinus, was covered by another, the sediments were compressed and solidified Region. Some have been found that are nearly Ancient Landmass enrolled assorted Ancient landmass 4 feet long. A fully preserved 450-million-year- Figure 6. Ordovician life. Illustration by Stephen F. Greb, Modern Landmass crinoids (lithified) into the sedimentary rocks that we see today. Clay became PANTHALASSIC OCEAN Kentucky Geological Survey, © 1995. Modern landmass , North China old crinoid is shown in Figure 9(b). Zone (triangles point in the directionSubduction of subduction) zone (triangles point in the mudstone and shale, loose sands and silt became and siltstone, direction of subduction) shell fragments and lime oozes became limestone and dolomite, gravels Sea Floor Spreading Ridge 12,084 sq. mi. (29.9%) Australia Figure 19. The Mississippian world, 325 to 360 million years ago. Four-legged fenestrate became conglomerates, and peat swamps became . The ages of rocks in Kazakstania evolved in swamps near the equator. Modified from Scotese (2003); used with permission. bryozoan each region, together with a synopsis of the development of life during each Equator North America Siberia Antarctica Mississippian rocks are exposed at the surface in the Mississippian Plateaus (Pennyroyal or Figure 21. Mississippian sea life. Illustration by Stephen F. Greb, period, are shown in Figure 1. PALEO-TETHYS Kentucky OCEAN Pennyrile) Region and occur below the surface in both of the coal fields. Mississippian rocks are Kentucky Geological Survey, ©1995. Fossil photos by Rick Schrantz, India Kentucky Paleontological Society; used with permission. Million Where Rocks South absent in the . millions rocks at the IAPETUS China Africa South During most of the Mississippian, Kentucky was covered by shallow tropical seas (Fig. 19). of OCEAN Years Appearsurface at the South GONDWANA America years America Changing depositional environments led to different types of rocks being deposite d throughout the Figure 9. (a) Nautiloids and (b) Crinoid. Photos by Rick Schrantz, Kentucky Paleontological Society; used with Era Er Life* PerioPeriod Agoago Surfacein Kentucky in Kentucky New England Mississippian (Fig. 20). Black shale continued to be deposited briefly during the Early Mississippian and Nova Scotia Sahara Desert permission. (c) Colonies of cyanobacteria formed like this one from the Ordovician. Cyanobacteria, modern 2 Ancient landmass still living today, photosynthesized for billions of years to give us the -rich atmosphere in which life flourishes. Period, but soon gave way to a great influx of muds, silts, and sands brought in by rivers and Modern landmass 23 Photo by Brandon Nuttall, Kentucky Geological Survey. from uplands many miles to the northeast that were deposited as a great delta. Peculiar markings on abundant Subduction zone (triangles point in the direction of subduction) some slabs of siltstone are indications of water currents and sea-bottom life. (Age of Seafloor spreading ridge 7,399 sq. mi. (18.3%) When seas cleared during the middle part of the Mississippian, great thicknesses of limestone Mammals) 65

Cenozoic Figure 4. The Ordovician world, 440 to 500 million years ago. The end of the Ordovician were deposited in the warm, shallow waters. Many caves have developed in these limestones during Figure 23. Mississippian teeth, 330 million years old. oldest flowering was one of the coldest times in earth history. Modified from Scotese (2003); used with the past 5 million years. This area is now known as one of the world’s most famous (cave- Photos by Rick Schrantz, Kentucky Paleontological Society; abundant permission. bearing) regions and is home to the world’s longest cave , Cave. used with permission. 140 Periodically, during the latter part of the Mississippian, tidal deltas and low coastal plains covered large parts of Kentucky. Coastal environments alternated with periods when the sea inundated the Figure 22. A Mississippian embolomere, (Age of oldest an early . Illustration by

Dinosaurs) region. abundant dinosaurs Most of the Mississippian rocks found in Kentucky are marine, so many of the fossils in them are Stephen F. Greb, Kentucky Geological Kentucky missing in Survey, ©1995. oldest dinosaurs and mammals 210 (Fig. 21). Common Mississippian fossils found in Kentucky include corals, bryozoans, brac hiopods, trilobites, snails, clams, cephalopods, crinoids and blastoids, teeth, and of trilobites and ostracodes and conodonts. other marine animals 250 When there was dry land in the form of low coastal plains, land plants and animals lived. Land Figure 20. Interbedded siltstone, sail-backed, mammel-like limestone, and shale of the 350- 290 Figure 8. A 440-million-year-old plants such as seed , true ferns, scale , and calamite trees grew in these coastal areas. coal swamps, abundant and were probably numerous on land. lived in estuarie s and ox-bow lakes, million-year-old Fort Payne Forma- fossil found in Bath County. The brachiopod is tion along Ky. 61 in Cumberland insects; first reptiles the Kentucky state fossil. Photo by Rick Schrantz, 325 but only one amphibian fossil has been found in Kentucky (in 1995). Called an embolomere (Fig. 22), County. The depositional environ- Kentucky Paleontological Society; used with per- it was about 5 feet long, had a long, streamlined body, and probably lived most of the time in water ment changed throughout the Mississippian mission. crinoids Figure 7. A cephalopod chases trilobites in the Ordovician sea. and ate fish and other small amphibians and reptiles. It was found in Mississippian on the Mississippian, producing a variety 360 Figure 5. The 450-million-year-old Camp Nelson Limestone along the Kentucky River Illustration by Stephen F. Greb, Kentucky Geological Survey, margin of the Western Kentucky Coal Field. of limestones, dolomites, shales, oldest amphibians Palisades in Fayette County was formed from fine lime mud deposits in clear, shallow ©1995. siltstones, and sandstones. seas similar to those of the present- Bahamas.

(Age of 410 oldest land plants Invertebrates)

Paleozoic and animals 440 edge of the water. Grasses, seed ferns, ferns, scale trees, calamite trees, and cordaite trees The Pennsylvanian Period grew in these luxuriant (Fig. 26). During times of heavy rainfall, thick accumula- brachiopods and trilobites Ordovician Pennsylvanian rocks are both marine and nonmarine, the latter predominating. tions of debris (peat) were deposited. Vegetation of all sorts fell into the water and was buried under blankets of deltaic clays, silts, and sands (Fig. 27). Clay sealed the 500 The Silurian Period Although all of Kentucky was probably covered by Pennsylvanian sediments at one time, * extinctions occur has completely removed Pennsylvanian rocks from all areas but the Eastern and vegetation from oxygen, preventing decay. The process was repeated many times. The at Period boundaries Western Kentucky Coal Fields. weight of sediments over long geologic time compressed the buried vegetation into the beneath numerous coal beds in Kentucky's two coal fields.

the surface During the Pennsylvanian, often called the Coal Age, parts of Kentucky were covered in Kentucky PANTHALASSIC OCEAN 570 North China intermittently by shallow seas (Fig. 24). Marine waters advanced and receded many times. When the rose, which it did periodically, it covered the coastal peats and The was warm, and extensive forests grew in great coastal swamps (Fig. 25) at the created large inland muddy seas. During these times, which lasted for many thousands of Figure 1. The geologic ages of Kentucky Siberia Kazakstania years, many types of marine s and vertebrates lived in Kentucky (Fig. 28). Malaya Late Carboniferous 306 Ma Barentsia Common Pennsylvanian marine fossils found in Kentucky include corals, brachiopods, With the exception of a few instances (in Crittenden and Elliott Counties) where deep- Equator North America PALEO-TETHYS trilobites, snails, clams, cephalopods, crinoids, fish teeth, and ostracodes and conodonts. seated igneous (solidified volcanic ) rocks have been pushed to the surface, the Baltica OCEAN Australia Siberia Laurentia Kazakstania bedrock of Kentucky consists entirely of sedimentary rocks. Tectonic forces and erosion South Kentucky North America Ural Mts. have bent, folded, and carved those sedimenta ry rocks into distinctive regions (Figs. 2–3). Avalonia China Mexico India PANTHALASSIC OCEAN North China 89° 88° 87° 86° 85° 84° 83° 82° RHEIC Antarctica t Kentucky comes up for EXPLANATION c je ro OCEAN P Figure 11. The very fine-grained, dense Laurel Dolomite along the Bluegrass Hartz Mts. Arabia P ° Quaternary; 2 million years ago–present day; clay, sand, and gravel 39° A PANGEA 39 OM air near the equator E Equator 0 40 mi AL PALEO-TETHYS , P se Quaternary and Neogene; 1–5 million years ago; gravel and sand te Appalachian N BOONE co Parkway was formed on the Silurian beneath warm, clear waters. Ancestral R. S 0 50 km C.


CAMPBELL 0 Paleogene; 30–60 million years ago; clay and sand O IH O GONDWANA 20 scale © Rockies Meseta South China Paleogene and Cretaceous; 60–70 million years ago; sand and clay B Africa horn GALLATIN PENDLETON River BRACKEN Ancient landmass Florida colonial Ouachita Mauretanide Mts. Cretaceous; 85–95 million years ago; gravel and sand CARROLL GRANT corals MASON Mts. Permian; 245–290 million years ago; igneous intrusions TRIMBLE corals OWEN ROBERT- GREENUP Modern landmass A SON LEWIS Pennsylvanian; 290–325 million years ago; shale, sandstone, and coal HARRISON N HENRY FLEMING t Subduction zone (triangles point in the ec OLDHAM BOYD oj Mississippian; 325–360 million years ago; shale, limestone, and sandstone A Arabia Pr CARTER South Africa P NICHOLAS A M I SCOTT direction of subduction) EO AL Devonian; 360–410 million years ago; shale and limestone SHELBY America , P D ROWAN W TSE se FRANKLIN ote N BOURBON BATH Sc Australia R. ELLIOTT VIR GINI A C. I 0 Silurian; 410–440 million years ago; dolomite and shale MONTGOMERY 00 JEFFERSON LAWRENCE GONDWANA India © 2 FAYETTE 38° Ordovician; 440–510 million years ago; limestone, dolomite, and shale SPENCER CLARK 38° ANDERSON 690 sq. mi. (1.7%) Ancient Landmass BULLITT WOODFORD Figure 26. Plant fossils from the Eastern Kentucky Coal Field (350 million years old). Left, horse- Cambrian; 510–570 million years ago; MEADE MENIFEE A Ancient landmass Antarctica MORGAN dolomite, sandstone, and shale (shown in NELSON JESSAMINE Modern Landmass HANCOCK MERCER POWELL JOHNSON MARTIN Figure 10. The Silurian world, 410 to 440 million years ago. When sediments Modern landmass tail plant, . Right, seed . Photos by Rick Schrantz, Kentucky Paleontological Society; cross section only) BRECKINRIDGE HARDIN WASHINGTON ; more than 570 million HENDERSON ESTILL WOLFE Subduction Zone (triangles point in the DAVIESS MADISON MAGOFFIN Subduction zone (triangles point in the used with permission. FLOYD that formed the Silurian rocks were deposited 425 million years ago, the seabed years ago; igneous and metamorphic BOYLE GARRARD LEE bryozoan direction of subduction) UNION MARION direction of subduction) rocks, and sandstone (shown in cross BREATHITT PIKE section only) WEBSTER that was Kentucky contained , (sea ), worms, , River McLEAN LARUE Sea Floor Spreading Ridge JACKSON OWSLEY Faults S CRITTENDEN GRAYSON LINCOLN KNOTT and early fish. reefs expanded and land plants began to colonize the barren 12,076 sq. mi. (29.9%) O I OHIO HART TAYLOR CASEY I N HOPKINS ROCKCASTLE PERRY I L L bryozoans LIVINGSTON BUTLER Ohio MUHLENBERG . Modified from Scotese (2003); used with permission. crinoids CLAY Figure 24. The Pennsylvanian world, 290 to 325 million years ago. Vast coal swamps EDMONSON GREEN PULASKI LETCHER LAUREL Figure 27. The Four Corners CALDWELL LESLIE 37° BALLARD McCRACKEN ADAIR 37° RUSSELL formed along the equ ator. Modified from Scotese (2003); used with permission. LYON WARREN BARREN METCALFE Formation along Ky. 7 in SIM IRUOS KNOX TRIGG WHITLEY A CARLISLE MARSHALL CHRISTIAN HARLAN Morgan County has alter- . CUMBERLAND Silurian rocks are exposed at the surface in the , which R TODD LOGAN WAYNE i GRAVES ALLEN Figure 12. Layers of greenish-gray shale p CLINTON BELL sip HICKMAN SIMPSON MONROE McCREARY nating bands of sandstones issis M CALLOWAY rings the Bluegrass Region. Silurian rocks are absent in the Bluegrass, but and dolomite alternate in the Silurian FULTON T E N N B and siltstones (light) and E S S E E occur below the surface in other parts of Kentucky. During most of the rocks along Interstate 64 in Bath County. 89° 88° 87° 86° 85° 84° 83° 82° shales and (dark), Shales were deposited in shallow, muddy Silurian, Kentucky was covered by shallow tropical seas (Fig. 10). Silurian revealing the changing seas, and dolomites formed when seas seas were commonly warm and clear (Fig. 11), although the presence of depositional environment— were clearer and deeper. A Basin Appalachian Basin A (Eastern Kentucky Coal some shale beds suggests that muddy conditions prevailed at times shallow seas, deltas, river (Western Kentucky Coal Arch

Kentucky River System Fault Field) Lexington Fault Lexington System Embayment Field) Rough Creek Fault System Tabb Fault Fault Tabb System (Fig. 12). Fluctuations in the supply of eroded material probably account brachiopods deposits, swamps—during for the shale units between the units; the source of sediments the Pennsylvanian. for that shale was from the east. trilobites Cross sections are diagrammatic; Figure 13. Silurian life. Illustration by Stephen F. Greb, Appalachian Basin not to scale B (Eastern Kentucky Coal B Silurian dolomite and limestone are composed largely of whole and Field) Mountain Overthrust Fault Kentucky Geological Survey, ©1995. Lexington Fault System Cincinnati Arch Kentucky River Fault System fragmented skeletons of animals that lived in the sea. These remains were deposited near where they lived. Numerous corals and brachiopods can be found in the Silurian limestones and dolomites. Figure 2. General . All Silurian fossils are marine invertebrates (Fig. 13). Common Silurian Figure 28. The 18-inch jawbone fossils in Kentucky include corals (Fig. 14(a)), bryozoans, brachiopods, of a shark (Edustus) that swam The Landscape of Kentucky trilobites (Fig. 14(b)), snails, clams, cephalopods, crinoids, and ostracodes in the sea above Kentucky 300 Figure 25. Peat-forming swamps, also known as mires, formed over Kentucky during million years ago was found pre- Kentucky’s natural regions, scenic geologic features, and fossil-fuel, mineral, and and conodonts. served in the shale above a coal During the Silurian Period, gentle folding began, creating the the Pennsylvanian. The coal beds are the remains of these swampy landscapes. This groundwater resources are directly related to the underlying rocks. Most of the areas reconstruction shows a dominated by a mixture of lycopsid—nonseed-bearing— seam in Webster County. Photo underlain by sandstone, primarily the Eastern and Western Kentucky Coal Fields, are Cincinnati Arch. This upwarping raised part of the land above sea level trees (front right, also with juvenile ), tree ferns (left, with mantles of prop by Stephen F. Greb, Kentucky Geological Survey. either hilly or mountainous, because sandstones resist weathering and erosion more than and temporarily separated two major geologic basins. extending out from the trunks), seed ferns (center, trees with crow n of frond-like ), and —extinct early horsetails (right side, rear foreground, with branches in other types. Caves, sinkholes, sinking creeks, large springs, and other features MAP AND CHART associated with underground drainage are found in the limestone terrains typical of the 25 whorls). The forest is open and includes many vines and low-growing plants. Painting by Mary Parrish, courtesy of Smithsonian Institution; used with permission. Pennyroyal (Mississippian Plateaus) and the Bluegrass Regions. The Region (), which is part of a large that extends to the Figure 14. (a) , the chain coral, is common in some Silurian rocks in Kentucky. (b) The 420-million-year- , is the youngest geologic region in Kentucky, covered by unconsolidated old remains of a Silurian trilobite, found near Bardstown, are beautifully preserved by crystalline sand, silt, clay, and gravel. dolomite. Photos by Rick Schrantz, Kentucky Paleontological Society; used with permission. The Cretaceous PeriodAsian-Alaskan The K/TPaleogene/Neogene Boundary 66 Ma Periods land bridge 94 Ma Alaska Alaska OCEAN Ohio North Eurasia America River Rocky North S S G R A North U E Mts. China . B L Kentucky America

N Kentucky R BELT E South T Fossil bones of giant arthrodires (Fig. 18), sharks, and other fish have been found in the U E O L China 0 40 mi A NORTH Chixulub H T The Devonian Period KentuckyGulf of S Devonian rocks in the Knobs Region. Some giant arthrodires, with sharp cutting beaks, grew 0 50 km N Early Devonian 390 Ma Mexico Impact E ATLANTIC Indochina OCEAN I N N E R M Site scale BLUEGRASS REGION P R to more than 20 feet in length and fed on sharks. PACIFIC B L U E – A Equator PACIFIC C Arabia T H E K N O B S S OCEAN EDEN G R A S S E Proto- E A S T E R N The most commonly found plant fossils in the Devonian black shales of Kentucky are M OCEAN Africa U Equator South Greater L East Caribbean D R America India THE KNOBS Siberia silicified logs (called Callixylon) of the seed-fern tree, . Several silicified fossil logs Africa A Paci c

U Sea G K E N T U C K Y North China South Rise INDIAN W E S T E R N H S from these shales in Kentucky are on display at the Smithsonian Institution in Washington, River H America IL Caledonide Mts. SOUTH OCEAN L E FLUORSPAR L Madagascar t K E N T U C K Y South China D.C. Rarely, foliage from these and other plants is found in Devonian shale s. ec j DISTRICT T L C O A L F I E L D ro I Kazakstania Malaya ATLANTIC P P N A V India t OM E ec LE S oj A Pr , P Ohio M P se C O A L F I E L D T North America One of the most famous fossil coral outcrops in the world is at the Falls of the Ohio near A OCEAN ote P OM . Sc T E Australia . R R AL C A SOUTH , P 00 C O se 20 Australia ote © S Equator Sc P R. E C. Louisville. Many solitary and colonial coral fossils can be seen in the rocks exposed in this 0 00 ATLANTIC © 2 Ancient Landmass r S e S EURAMERICA G v Antarctica i U N protected area. Access to the outcrop is best on the Indiana side of the (through the Antarctica Modern Landmass R M I S S I S S I P P I I A MOUNTAIN (Laurentia & Kentucky Australia Ancient Landmass Ancient landmass i R E p D R P T MT. Baltica) p I P P I N G S A Southern Ancient landmass Subduction Zone (triangles point in the si L Modern Landmass sis P Falls of the Ohio State Park), although the exposures are actually in Kentucky. Modern landmass Mis E M B AY M E N T M I S P I A N Europe direction of subduction) S I S S I P PINE Modern landmass modified from A.K. Lobeck Arabia Subduction Zone (triangles point in the Subduction zone (triangles point in the CUMBERLAND Northern India direction of subduction) Appalachians ct Subduction zone (triangles point in the Seadirection Floor Spreading of subduction) Ridge je ro Antarctica P AP direction of subduction) Figure 3. Physiographic regions of Kentucky. OM RHEIC OCEAN LE A , P ) e 93 sq. mi. (0.2% GONDWANA tes Seaoor spreading ridge co . S 103 sq. mi. (0.25%) . R Sea oor spreading ridge Africa 0 C 200 Sea Floor Spreading Ridge Stream erosion has been the predominant geologic force sculpting and modifying the © large horn Ancient Landmass South America Figure 29. The Cretaceous world, 65 to 140 million years ago. India separated from Figure 31. The Paleogene/Neogene world, 2 to 65 million years ago. The 10-mile-wide Ancient landmass coral Kentucky landscape since the close of the Era 250 million years ago. Younger Modern Landmass Madagascar and raced north on a collision course with Eurasia during the Cretaceous. impact at Chicxulub 65 million years ago caused climate changes thought to have killed the Modern landmass rocks were eroded from the crest of the Cincinnati Arch (a major upwarp, or arching of Subduction Zone (triangles point in the Modified from Scotese (2003); used with permission. dinosaurs and many other forms of life. Modified from Scotese (2003); used with permission. Subductiondirection of subduction) zone (triangles point in the direction of subduction) the rock strata, extending from the Cincinnati, Ohio, area through the central Bluegrass Sea Floor Spreading Ridge Seafloor spreading ridge Deposition of marine and fresh- to brackish-water sediments continued in the Jackson Region toward Nashville, Tenn.), leaving older Ordovician rocks exposed at the surface 334 sq. mi. (0.8%) A series of uplifts ended the Paleozoic Era in Kentucky. Seas receded and the arthrodire Purchase Region during Paleogene/Neogene time (Fig. 31). Distribution of deposits indicates of the Bluegrass Region. Away from the Bluegrass, the rocks are progressively younger. Figure 15. The Devonian world, 360 to 410 million years ago. By the Devonian, the Early land became dry for a long period. Much of Kentucky’s landscape is a product of fish that the area was near the northern limit of the Mississippi Embayment. Parts of the The softer or weaker rocks eroded faster than harder, more resistant ones. Thus, we see Paleozoic were closing, forming a to a called Pangea. erosion that began at that time. Two hundred million years of geologic history crinoid embayment must have been swampy, because thin beds of lignite and carbonaceous clays escarpments such as Muldraughs Hill (Knobs area), the Dripping Springs Escarpment Pangea contained most of the continental crust, from which the present continents are are missing in Kentucky, including the Middle and Late Permian, Triassic, derived. Freshwater fish were able to migrate from the southern hemisphere continents to occur in the western half of the eight-county Jackson Purchase Region. at the outer edge of the Mississippian Plateaus, and the escarpments at the edges of the Jurassic, and most of the Cretaceous Periods. Eastern and Western Kentuc ky Coal Fields. For more about the landscape of Kentucky, North America and Europe. Forests grew for the t time in the equatorial regions of Arctic . Modified from Scotese (2003); used with permission. During the latter part of the Cretaceous, the Gulf of Mexico inundated much see Carey and Hounshell (2008). of the southern (Fig. 29). A long bay extende d north from the Gulf, The Quaternary Period Glaciations during the Qua ternary (1.8 million to 10,000 years ago) (Fig. 32) played only an colonial covering all of the Jackson Purchase Region and adjacent parts of the Mississip- indirect role in the geologic , compared to the extensively glaciated states Upwarping of the Cincinnati Arch continued during the first part of the coral pian Plateaus with sands, clays, and gravels (Fig. 30). These geologic deposits are Learn More horn a marked contrast to the underlying hard Paleozoic rocks because to this day of Illinois, Ohio, and Indiana. The southern margin of the continental ice sheet reached Devonian Period, evidenced by the absence of outcrops of rocks of Early coral Kentucky only in the vicinity of Covington. It did, however, affect the course of the Ohio River Carey, D.I., 2008, A brief : kgs.uky.edu/kgsweb/download/ Devonian age in central Kentucky. The Cincinnati Arch has been a most of the Cretaceous sediments remain unconsolidated and soft. geology/EARTHHISTORY.ZIP [accessed 3/18/2011]. upstream from Cincinnati and at Louisville, and gla cial meltwaters from the north filled its significant feature in the determination of rock-outcrop patterns and armored valley with deposits of sand and gravel. The ice sheet or floodwaters from the melting Carey, D.I., 2009, Kentucky river basin maps: kgs.uky.edu/kgsweb/download/ Figure 18. A large armored fish (arthro- regional topography in the state. snail temporarily obstructed the flow of some north-flowing streams such as the Licking, Kentucky, water/basins.htm [accessed 3/18/2011]. Devonian rocks are exposed at the surface in the Knobs Region, which dire) swims among assorted corals and smaller fish in the Devonian sea. Illus- Salt, and Green Rivers, causing local drainage modifications and leaving remnants of Carey, D.I., and Hounshell, T.D., 2008, Kentucky terrain: Kentucky Geological Survey, rings the Bluegrass Region. Devonian rocks are absent in the Bluegrass, ser. 12, Map and Chart 187, scale 1:750,000. colonial finger coral horn corals tration by Stephen F. Greb, Kentucky slackwaterLast Glacial or lake-bottom Maximum sediments 18,000 years various ago distances upstream. but occur below the surface in other areas of Kentucky. During most of the Geological Survey, ©1995. Carey, D.I., Hounshell, T.D., and Kiefer, J.D., 2008, Geologic hazards in Kentucky: Figure 17. Life in the Devonian sea. Illustration by Stephen Greenland Devonian, Kentucky was covered by shallow tropical seas (Fig. 15), F. Greb, Kentucky Geological Survey, ©1995. Kentucky Geological Survey, ser. 12, Map and Chart 185, 1 sheet. Ural Siberia although some lands may have been dry at times in what became central Mts. Europe Kentucky Geological Survey, 2001, Physiographic diagram of Kentucky: 1 sheet. Rocky North North Kentucky. During the latte r part of the Devonian, deep seas covered Mts. America China McDowell, R.C., 1986, The geology of Kentucky—A text to accompany the geologic map of NORTH Iran Kentucky, and the water was poorly oxygenated at depth. Dark, organic- Kentucky ATLANTIC Tibet South Kentucky: U.S. Geological Survey Profe ssional Paper 1151-H, 76 p. Arabia India China rich muds were deposited during the Late Devonian, producing the Figure 16. Devonian PACIFIC OCEAN Gulf of Indochina McGrain, P., 1983, The geologic story of Kentucky: Kentucky Geological Survey, Devonian black shales in Kentucky (Fig. 16), which contain oil and are a along Ky. OCEAN Mexico Africa Equator ser. 11, Special Publication 8, 74 p. potential source for a variety of fossil fuels. Much of the oil and gas found 559 in eastern Fleming Scotese, C.R., 2003, Paleogeographic maps, PALEOMAP project: www.scotese.com County. The shale was South CENTRAL in Kentucky originally came from these Devonian black shales. America SOUTH INDIAN [accessed 3/11/2011]. formed in low-oxygen ATLANTIC South OCEAN All the Devonian rocks found in Kentucky are marine; consequently, all (anaerobic) seas that Mts. Africa Twenhofel, W.H., 1931, The building of Kentucky: Kentucky Geological Survey, ser. 6, OCEAN Madagascar Australia the fossils are marine invertebrates and vertebrates (Fig. 17). Common preserved the organic t ec oj v. 37, 230 p. Pr

AP matter in the sediments. M Devonian fossils found in Kentucky include sponges, corals, bryozoans, O LE PA e, tes Sco R. The shale is dark gray to C.

000 brachiopods, trilobites, snails, clams, cephalopods, crinoids, and © 2 black, weathers medium Ancient Landmass ostracodes and conodonts. ModernAncient Landmass landmass Acknowledgments gray to light brown, and Antarctica Probably the most common fossils found in Kentucky are the SubductionModern Zone landmass (triangles point in the Thanks to Rick Schrantz, Kentucky Paleontological Society, and Stephen F. Greb, is highly carbonaceous, Figure 30. Contrasting colors of reddish-brown Neogene gravel stored in a pit of directionSubduction of subduction) zone (triangles point in the stromatoporoids. They are sponges that form mounds 2 to direction of subduction) Kentucky Geological Survey, for illustrations and photos. Thanks to William Andrews, containing enough whitish-gray Cretaceous gravel in Livingston County. Photo by Paul Potter, University Sea Floor Spreading Ridge 3 feet across on the seafloor. They still exist today in moderately deep organic matter to burn. Sea oor spreading ridge Brandon Nuttall, and Meg Smath, Kentucky Geological Survey, for constructive reviews. of Cincinnati; used with permission. 7,626 sq. mi. (18.9%) water. Devonian stromatoporoids can be seen at the Falls of the Ohio near Thanks to Terry Hounshell and Collie Rulo, Kentucky Geological Survey, for artistic Figure 32. The world during the last , 18,000 years ago. Modified from Louisville. enhancement. Scotese (2003); used with permission.