CORE Metadata, citation and similar papers at core.ac.uk
Provided by KnowledgeBank at OSU
GEOLOGIC STRUCTURE OF NEAR-SURFACE ROCKS IN WESTERN OHIO1
STANLEY E. NORRIS U.S. Geological Survey, Water Resources Division, Columbus, Ohio 4-3212 ABSTRACT After completion of the work in north- NORMS, STANLEY E. Geologic struc- west Ohio, the water-resources investiga- ture of near-surface rocks in western tion was extended into the southwest and Ohio. Ohio J. Sci. 75(5): 225, 1975. central parts of the State, where 53 addi- A geologic structure map on the tional wells were drilled and logged. Silurian-Age Lockport Dolomite in west- Data from these wells, supplemented by ern Ohio is presented. The map, com- data from a nearly equal number of com- piled from recently published ground mercial oil and gas well logs and the logs water reports, is expected to be useful in of about 10 municipal and industrial a variety of geologic applications. wells, were used to construct a similar structure contour map essentially cover- In 1970 the Ohio Department of Na- ing the remainder of the area of occur- tural Resources, in cooperation with the rence of the limestone and dolomite de- U.S. Geological Survey, completed an posits in western Ohio (see Norris and investigation of the limestone and dolo- Fidler, 1973, rig. 2). mite aquifers in an area of about 9,000 The maps in previous reports, showing square miles (23,310 square kilometers) in in considerable detail the geologic struc- northwestern Ohio. The main part of ture of the near-surface rocks in western the investigation involved the drilling, Ohio, proved useful in defining the aqui- testing, and geophysical logging of ap- fer framework and determining the avail- proximately 80 exploratory wells, ranging ability of ground water in a large region in depth from about 200 feet to more than where limestone and dolomite aquifers 400 feet (61 to 122 meters). Thirty-five are important sources of water supply. municipal and industrial water wells also They should be of value also to those were logged. The logging program con- concerned with geologic problems not sisted of making natural gamma, single- associated with water-resources evalua- point resistance, self-potential, and cali- tion. To further enhance the utility of per logs, using portable, hand-operated the maps, they are combined in the pres- equipment. Early in the investigation ent report into one map covering the it became evident that the geophysical entire area studied in western Ohio. logs, especially the natural gamma logs, The new map (fig. 1) presents a brief provided a basis for identifying the description of the principal carbonate- carbonate-rock units and determining the rock units and structural features in position of the contact between the western Ohio, chiefly abstracted from Silurian-Age Lockport Dolomite and the the above-referenced reports. The reader overlying Silurian rocks (Norris and is referred to those reports, and references Fidler, 1969). A structure contour map cited therein, for more complete informa- on the top of the Lockport Dolomite was tion on the carbonate rocks and an ex- constructed, based on the data from the planation of how the geophysical logs water well logs, plus a few scattered con- were interpreted. trol points determined directly from quarry exposures, and agumented with STRATIGRAPHY data from approximately 85 natural gamma logs of oil and gas wells made Silurian-age carbonate rocks consisting by commercial logging companies (see chiefly of the Lockport Dolomite and the Norris and Fidler, 1971, fig. 2). overlying Bass Islands Group (chiefly dolomite) underlie most of the relatively Manuscript received March 26, 1975, revised flat terrain of western Ohio, where they August 21, 1975 (#75-19). crop out or lie beneath glacial deposits 226 STANLEY E. NORRIS Vol. 75
INDEX MAP Or OHIO
EXPLANATION
Area underlain principally by the Bass Islands Group. Generally covered by glacial drift, bedrock is exposed at scattered locations.
Area underlain by the Lockport Dolomite, the Bass Islands Group having been removed by erosion. (Highly generalized in Adams and Highland Counties)
Area in which the Lockport Dolomite has been removed by erosion Bedrock, generally covered by glacial drift, is principally Ordovican shale.
Contact
Structure contour Showing altitude of top of Lockport Dolomite. Contour interval 100 feet; (30 metres); datum is mean sea level.
Exposed contact of Niagara Group with overlying Bass Island Group.
State test well and number
o Municipal or industrial well
D Oil or gas well
Trace of sections shown on figures 6 and 7 in NORRIS AND FIDLER, 1973 (SEE REFERENCES)
FIGURE 1. Structure contours on the Lockport Dolomite in western Ohio. No. 5 GEOLOGIC STRUCTURE, WESTERN OHIO having a wide range in thickness. Locally east from the Illinois and Michigan in parts of Logan and Champaign Coun- basins on the west and northwest. As ties and more generally in counties in the indicated by contours in figure 1, the central part of the State, the Bass Islands axis of the Cincinnati arch in western Group is overlain by Middle Devonian Ohio extends from southwest to north- limestone (Columbus and Delaware lime- east, from Cincinnati approximately stones) and shale. In the northwest through Dayton, Bellefontaine, and Ken- corner of the State, in Williams, Fulton, ton to a point near the western end of and parts of Defiance and Henry Coun- Lake Erie. The carbonate beds arc ties, carbonate rocks arc too deeply nearly flat lying on the top of the arch, buried by glacial deposits and the Ohio for example in Logan County and south- Shale of Late Devonian age to be a com- cast Hardin County, and dip away at mon source of water to wells. low angles on both flanks. In the north- The Loekport is an exceptionally pure, west part of the study area, the dip of light-gray to white, finely to coarsely the Loekport Dolomite on the west side crystalline dolomite, typically occurring of the arch is to the north and northwest in beds ranging in thickness from about at 5 to 10 feet per mile (1 to 2 m/km). 1 to 5 feet (0.3 to 1.5 m). Locally, it On the east side of the arch, the dip of grades into reeflike masses, with little or the Loekport Dolomite is somewhat no discernible bedding. The change from steeper, about 25 feet per mile (4.7m/km) normal bedding to the reeflike phase is along a line extending from east-central accompanied by a large increase in Champaign County into Franklin thickness; it is believed that reefs char- County. acterize the unit wherever it is more than Associated with the western flank of about 100 (30 m) thick. the Cincinnati arch in Hancock, Wood, The overlying Bass Islands Group in and Lucas Counties is the north-trending Ohio consists generally of a thinly bedded, Bowling Green fault and monocline, the brown-to-drab, crystalline-to-granular, approximate position of which is shown argillaceous dolomite. The Bass Islands on the map. Evidence obtained in this group includes, in ascending order, the investigation is insufficient to define ac- Greenfield Dolomite, Tymochtee Forma- curately the position and magnitude of tion, Put-in-Bay Dolomite, and Raisin the fault. The relatively few control River Dolomite. These dolomite units points shown on figure 1 in the immediate are generally distinguishable from one vicinity of the fault were useful chiefly in another on the outcrop; however, there is making minor changes in its position, the much variation in Hthology from place to general location of which is that de- place. Carman (1927, p. 485) states scribed by Stout (1941, p. 15-16). Stout that although rocks fitting the general traced the location of the fault southward description of the Bass Islands Group from Michigan to Hardin County on the can be found in all the constituent units, basis of data from oil and gas wells. The "each member also has one or more other fault is downthrown on the west side; types of stone within it. There are the maximum displacement, according zones of massive permeable dolomite, of to Stout (1941, p. 16), is about 200 feet evenly bedded nonlaminated dolomite, of (61 m) in the vicinity of Bowling Green, brecciated dolomite, of dolomitic shale, in Wood County. The Bowling Green of limestone, and of gypsum." fault is known to be exposed at only one place in western Ohio near a quarry in STRUCTURE the vicinity of Waterville, in southern The consolidated rocks were raised by Lucas County. According to J. E. tectonic forces to form the broad, low Carman (1948), north of the Waterville Cincinnati arch, a major structural fea- quarry the rocks along the extenstion of ture of the mid-continent region. Ex- the Bowling Green fault are no longer tending northward from the Nashville displaced relative to one another, but dome area in Tennessee to a terminus in become a steeply dipping monocline. southern Ontario, the Cincinnati arch Erosion reduced the consolidated rocks separates the Appalachian basin on the along the top of the arch to a generally 228 STANLEY E. NORRIS Vol 75 even plain, exposing progressively older part of the State the carbonate rocks, rocks in a southwesterly direction. The including Devonian-age units, are be- carbonate beds were removed by erosion lieved to reach a maximum thickness of in the southwestern quarter of the State 800 to 900 feet (244 to 275 m). in an area of approximately 3,700 square Structural relief along the crest of the miles (9,583 km2), leaving exposed, or arch is in part a depositional feature re- thinly covered by glacial drift, a thick sulting from an increase in the thickness sequence of thinly bedded shale and shaly of the Lockport Dolomite where reefs limestone strata of Ordovician age (see occur. Typically 180 to 200 feet (55 to 61 m thick in northwest Ohio, the Lock- Peripheral to this area of Ordovician port Dolomite thickens markedly near rocks—and to a relatively narrow strip the northern end of the arch where underlain by older Silurian rocks, chiefly Sparling (1965, p. 236) reported the the Brassfield Limestone—the Lockport thickness to be more than 400 feet (122 Dolomite constitutes the bedrock in an m) in a quarry test hole in Ottawa irregular band, underlying approximately County. The unit thins southeastward, 4,000 square miles (10, 360 km2) in all or beneath a thickening cover of younger parts of 17 counties. The outcrop band rocks, to about 65 feet (20 m) near Lon- is narrowest in the southern part of the don, in Madison County, where the top study area, near the Ohio River in cen- of the unit at the site of State test well tral Adams County, and widest in the CP-30, occurs at a depth of 261 feet western part of the study area, where it is (80 m). found throughout virtually all of Darke, Mercer, and Shelby Counties and sig- LITERATURE CITED Carman, J. E. 1927. The Monroe division of nificant parts of adjacent counties. The rocks in Ohio. Jour. Geology 35: 481-50G. Lockport Dolomite is also exposed or 1948. A study of the geology of Lucas thinly covered by glacial drift, along the County and the lime-dolomite belt. Ohio crest of the arch in the northern part of Adacemy of Science, Annual Field Com. in Geology, p. G (mimco.). the area, chiefly in Hancock, Seneca, Norris, S. E., and R. E.Fidler. 1909. Corre- Wood, Ottawa, and Sandusky Counties. lation of carbonate rock units in northwest Adjacent to the outcrop area of the Ohio by natural gamma logging, In Geo- logical Survey Research 1969. U.S. Geol. Lockport Dolomite, the Bass Islands Survey Prof. Paper 650-B, B158-B1G1. Group, a wedge-shaped sequence of car- 1971. Availability of ground water bonate beds, constitutes the bedrock in from limestone and dolomite aquifers in most of the remainder of western Ohio northwest Ohio and its relation to geologic in an area of about 8,200 square miles structure, In Geological Survey Research 2 1971. U.S. Geol. Survey Prof. Paper 750-B, (21,238 km ). p. B229-B235. The carbonate beds as a whole thicken 1973. Availability of ground water on both sides of the arch in the direction from limestone and dolomite aquifers in southwest Ohio and the relation of water of dip. The aggregate thickness of the quality to the regional flow system. U.S. entire carbonate sequence ranges from Geol. Survey Water Resources invest. 17-73. near zero at the outcrop in western Ohio Sparling, D. R. 1965. Geology of Ottawa to (about) 600 feet (183 m) at Columbus, County, Ohio. Ohio State Univ., unpub. where it includes approximately 130 feet Ph.D. thesis. 265 p. Stout, Wilber. 1941. Dolomites and lime- (40 m) of Devonian-age Columbus and stones of western Ohio. Ohio Geol. Survey Delaware limestones. In the northwest Bull. 42, 4th ser., 468 p.