A Quarterly Publication of the Division of Geological Survey 1999, No. 1 THE GEOLOGY OF OHIO—THE DEVONIAN by Michael C. Hansen he Devonian Period was an important epi- sode in the history of the Earth. For the first time, the land surface began to show a notice- T Siberia able hint of green from terrestrial plant life, which evolved from simple, ground-hugging forms early China in the period to great trees late in the period. Con- Laurentia current with the proliferation of forests, vertebrates (North America) began their first tentative forays out of the water. The warm, tropical seas accumulated limy sedi- Baltica Australia ments that would become economically important Ohio deposits of limestone, and the organic remains of countless organisms that flourished in Devonian marine waters became a source of hydrocarbons. During this 48-million-year span, beginning about Africa 408 million years ago and ending about 360 million years ago, Ohio was just south of the Equator and Antarctica experienced a warm, tropical climate. South America India The Devonian System was named in 1839 by Continental configuration during Devonian time. Modified from C. R. Scotese and others (1979, Roderick Murchison and Adam Sedgwick for a Paleozoic base maps, Journal of Geology, v. 87, fig. 24). series of greatly disturbed sedimentary rocks that lay between the Silurian and the Carboniferous rocks in Britain. Corals found in thin marine beds in single, small, lens-shaped outcrop in a now-re- these rocks in Devonshire, England, were deter- claimed quarry in Lucas County, west of Toledo. mined by paleontologist William Lonsdale to be This dark-gray shale was exposed in a highwall in intermediate between those of the Silurian and the France Stone Company’s Holland Quarry when those of the Carboniferous; therefore, Murchison it was discovered by J. Ernest Carman of The Ohio and Sedgwick proposed a new geologic system State University during the course of mapping named after the province where the corals were Lucas County for the Survey in the 1920’s. This obtained. Most of the Devonian rocks in Britain shale would have been given no more than cursory consist of a thick series of reddish sandstones, attention by Carman or other geologists were it not shales, and conglomerates that collectively were for the suite of remarkable fossils it contained. named the Old Red Sandstone. The Old Red Sand- Particularly noteworthy were the remains of two stone was made famous by Hugh Miller, a self- species of primitive, jawless, armored fishes, an educated Scottish quarryman who collected and arthrodire, and an acanthodian. The specimens of studied fossil fishes from these rocks. Miller’s 1841 jawless fishes are the only ones of this type known book, The Old Red Sandstone, is a classic in geology. from Ohio. In addition to fishes, the Holland Quarry Shale produced fossils of eurypterids, other inver- DEVONIAN ROCKS IN OHIO tebrates, and plants. The fishes, eurypterids, and the stratigraphy of the deposit were described in a Devonian rocks crop out in two areas in Ohio. series of papers published by the Chicago Field They are best exposed in a 20-mile-wide, north- Museum of Natural History in the early 1960’s. south-oriented belt in the central part of the state. The fossils determined the age and gave clues At its northern terminus, the outcrop belt narrows to the environment of deposition of the Holland and swings eastward along the southern shore of Quarry Shale. It is interpreted to have been a brack- Lake Erie. These rocks dip and thicken southeast- ish-water embayment that may have been con- ward into the Appalachian Basin and are present in nected to the sea to the northwest in the Michigan the subsurface of eastern Ohio. An arcuate belt of Basin. Much of Ohio, to the south and west, was Devonian rocks is present in northwestern Ohio, above sea level and not accumulating sediment. although there are few exposures of these rocks The Holland Quarry Shale, therefore, is so far the because of a thick mantle of glacial sediment. These only known deposit of Lower Devonian rocks ex- rocks dip northwestward into the Michigan Basin. posed in the state. However, the sea was present in A small area of Devonian rock crops out on the southeastern Ohio, on the edge of the Appalachian Bellefontaine Outlier (see Ohio Geology, Winter 1991) Basin, during Early Devonian time as recorded by in Logan and Champaign Counties. the presence in the subsurface of the Helderberg With one exception, all of the outcropping Formation, the Oriskany Sandstone, and the Bois Devonian rocks in the state are of Middle or Late Blanc Formation. Devonian age. The exception is the Holland Quarry By Middle Devonian time the warm, shallow Shale, a Lower Devonian unit known only from a seas once again spread across the state and limy continued on page 3 1999, No. 1 2 From The State Geologist... Thomas M. Berg MOVING CONFIDENTLY TOWARD THE NEW MILLENNIUM—A NEW DIRECTOR FOR THE DEPARTMENT OF NATURAL RESOURCES Thomas M. Berg, Division Governor Bob Taft has appointed Dr. Samuel W. Speck as Director of the Department of Natural Chief and State Geologist Resources. Dr. Speck, originally from Canton, Ohio, brings an outstanding background to ODNR, which is about to celebrate its 50th anniversary. He is a graduate of Muskingum College in New Concord, Ohio, and received his doctoral degree in government from Harvard University. He served the citizens of Ohio in the state legislature—in the House from 1971 to 1976 and in the Senate from 1977 to 1983. Most recently, Dr. Speck has been President of Muskingum College for the past 11 years. When he was appointed to his new position, Dr. Speck said, “I care deeply for the natural resources and I was deeply involved with these areas while I was in the Legislature. This position offers a wonderful opportunity to serve the region in an important new way while I’m also supporting the governor and his vision for Ohio.” Sam Speck also has had experience with the federal government, serving as Associate Director of the Federal Emergency Management Agency A quarterly publication of the (FEMA) under President Reagan. While at FEMA, he was head emissary to NATO’s Senior Civil Emergency Planning Council, was one of the U.S. representatives to the U.N. Vienna Conference on Chernobyl, and Ohio Department of Natural Resources served on the Board of Governors of the American Red Cross. Importantly for the Division of Geological Division of Geological Survey 4383 Fountain Square Drive Survey, Dr. Speck is very interested in the science of geology. He grew up on an Ohio farm and had an avid Columbus, Ohio 43224-1362 interest in geology. His first article ever published was in Rocks and Minerals magazine when he was in eighth 614-265-6576 grade; it was about crystals collected in northern Michigan. The Ohio Geological Survey looks forward to 614-447-1918 (FAX) working under Sam Speck’s direction. The next four years will be exciting times for ODNR as we move into e-mail: [email protected] the new millennium. At the same time that we welcome Samuel W. Speck to the Department of Natural Resources, we bid World Wide Web: http:// fond farewell to Donald C. Anderson, who served as ODNR Director during Governor Voinovich’s second www.dnr.state.oh.us/odnr/geo_survey/ term. Don was an outstanding Director and embraced a culture of honesty, respect, and trust in ODNR that Ohio Geology is a free publication. To will surely continue as his legacy. The Department accomplished many successes during his administration, become a subscriber please contact the Division of Geological Survey at the including funding of the Ohio Coastal Management Program, setting of strategic priorities for the Depart- above address, phone numbers, or e-mail. ment, and moving aggressively ahead with a broad spectrum of state-park and natural-resource infrastruc- ture projects under the NatureWorks program. Don Anderson has accepted an administrative position in the Ohio Department of Mental Health. We thank him for his dedication to ODNR and wish him well in his Editor: Michael C. Hansen Layout/Design: Lisa Van Doren continued service to Ohioans. Administration/State Geologist 614-265-6988 Geologic Records Center Division Employee of the Year 614-265-6576 or 614-265-6585 Bedrock Geology Mapping Group Michael R. Lester, Data Systems Coordinator lem solving, and the opportunity to teach com- 614-265-6473 for the Division, was named the Employee of the puter skills. Cartography & Editing Group Year for 1998 at the annual Christmas luncheon. His efforts have not gone unnoticed or unap- 614-265-6593 Nominations for this award are submitted by em- preciated by the staff, and it is a small reward to Coal Geology Group ployees and the selection is made by a committee recognize these contributions by the Employee of 614-265-6594 representing various groups of the Survey. the Year award. Mike lives in Reynoldsburg with Environmental & Surficial Mike came to the Survey in 1984 after receiv- his wife and three children. He enjoys golf and is an Geology Group ing a B.S. degree in visual communications tech- avid Monopoly player. 614-265-6599 nology from Bowling Green State University. He Industrial Minerals Group began work as a cartographer and was involved in 614-265-6602 all aspects of map and publication production. In Lake Erie Geology Group 1994, as the Survey began to become intensively 419-626-4296 419-626-8767 (FAX) computerized, especially in digital cartography, Mike moved into the newly created position of Petroleum Geology Group 614-265-6598 Data Systems Coordinator.