STATE OF OHIO DEPARTMENT OF NATURAL RESOURCES DIVISION OF GEOLOGICAL SURVEY Horace R. Coli ins, Chief LIBRARJ BUREAU OF GEOLOGY TALLAHASSEE, FLORIDA Report of Investigations No. 100 SILURIAN ROCKS IN THE SUBSURFACE OF NORTHWESTERN OHIO by Adriaan Janssens Columbus 1977 SCIENTIFIC AND TECHNICAL STAFF 8DNRDEPARTMENT OF OF THE NATURAL RESOURCES DIVISION OF GEOLOGICAL SURVEY ADMINISTRATION Horace R. Collins, MS, State Geologist and Division Chief Richard A. Struble, PhD, Geologist and Assistant Chief William J. Buschman, Jr., BS, Administrative Geologist Barbara J. Adams, Office Manager REGIONAL GEOLOGY SUBSURFACE GEOLOGY Robert G. Van Horn, MS, Geologist and Section Head Adriaan Janssens, PhD, Geologist and Section Head Richard W. Carlton, PhD, Geologist Charles R. Grapes II, BS, Geologist Michael L. Couchot, MS, Geologist Frank L. Majchszak, MS, Geologist Douglas L. Crowell, MS, Geologist James Wooten, Geology Technician Richard M. DeLong, MS, Geologist Garry E. Yates, Geology Technician Michael C. Hansen, MS, Geologist Linda C. Gearheart, Clerk Dennis N. Hull, MS, Geologist Brenda L. Rinderle, Office Machine Operator Michele L. Risser, BA , Geologist Joel D. Vormelker, MS, Geologist LAKE ERIE GEOCHEMISTRY LABORATORY Charles H. Carter, PhD, Geologist and Section Head D. Joe Benson, PhD, Geologist David A. Stith, MS, Geologist and Section Head Donald E. Guy, Jr., BA, Geologist George Botoman, MS, Geologist Dale L. Liebenthal, Boat Captain Norman F. Knapp, PhD, Chemist Thomas J. Feldkamp, BS, Geology Technician E. Lorraine Thomas, Laboratory Technician Marjorie L. VanVooren, Typist TECHNICAL PUBLICATIONS Jean Simmons Brown, MS, Geologist/Editor and Section Head Cartography Philip J. Celnar, BFA, Cartography Supervisor R. Anne Berry, BFA, Cartographer James A. Brown, Cartographer Donald R. Camburn, Cartographer Photocopy Composition Jean M. Lesher, Printing Technician Donna M. Swartz, Technical Typist Public Service Madge R. Fitak, BS, Geologist Pauline Smyth, MS, Geologist Beverly A. Leffler, Typist Billie Wilder, Clerk Technical Editing Merrianne Hackathorn, MS, Geologist/Assistant Editor STATE OF OHIO DEPARTMENT OF NATURAL RESOURCES DIVISION OF GEOLOGICAL SURVEY Horace R. Coll ins, Chief R BUREAU F OLOG» TALLAH ~r, S , FLORIDA Report of Investigations No. 100 SILURIAN ROCKS IN THE SUBSURFACE OF NORTHWESTERN OHIO by Adriaan Janssens . OHIO GEOLOGICAL SURVEY LIBRARY lt B~4 oT Columbus 1977 GEOLOGY SERVES OHIO ~ Photocopy composer: Donna M. Swartz (Appendix A - Jean M. Lesher) Cartographers: James A. Brown and Donald R. Camburn CONTENTS Page Page Abstract .................................. 1 C unit ............................... 25 Introduction .............................. 1 D unit ............................... 25 Regional setting ............................ 2 E unit ............................. · · · 25 Previous work ............................. 4 F unit ..................... · .. · · · · · · · · 25 Stratigraphy ............................... 8 G unit ............................... 25 Sub-Lockport rocks ....................... 8 Salina Group in western part of the report area .. 25 Cataract Group ......................... 8 Greenfield Dolomite .................... 25 Brassfield Formation .................... 8 Tymochtee Dolomite ................... 26 Cabot Head Formation .................. 9 Undifferentiated Salina dolomite .......... 26 Dayton Formation ....................... 9 Bass Islands Dolomite ...................... 27 Rochester Formation ..................... 12 Bass Islands Dolomite in the subsurface ....... 27 Undifferentiated sub-Lockport rocks ......... 12 Bass Islands Dolomite in outcrop ............ 29 Unconformities ......................... 12 Areas in which Lockport-Salina contact is anom- Lockport Group {Lockport Dolomite) ......... 15 alous . 30 Gasport Dolomite ....................... 18 Ottawa, Sandusky, Seneca, and Crawford Coun- Goat Island Dolomite ..................... 18 ties . 30 Guelph Dolomite and undifferentiated Lockport Lucas County . 34 Dolomite ........................... 18 Counties adjacent to Ohio-Indiana line . 35 Salina Group ............................. 23 Discussion . 3 5 Salina Group in Erie, Huron, and Richland Coun- Gypsum occurrences . 36 ties ................................ 23 References cited . 38 A unit ............................... 23 Appendix A-Summary of well data ............ 40, 41 B unit ............................... 25 Appendix B-Sample descriptions . 52 FIGURES 1. Stratigraphic column of the Silurian rocks of Dolomite in Townsend Township, Huron northwestern Ohio . 2 County . 21 2. Silurian bedrock geology of northwestern Ohio . 3 16. Thickness of the Lockport Group {Lockport 3. Locations of wells used in this study and Dolomite) . 22 structure on top of the Rochester Forma- 17. Representative nuclear log of the Salina Group in tion . in pocket Huron County . 23 4. Thickness of sub-Lockport Silurian rocks . 7 18. Correlation of representative nuclear logs of 5. Generalized cross section of sub-Lockport strata . 9 Silurian rocks in Fulton and Erie Counties . 24 6. Generalized boundaries of sub-Lockport Silurian 19. Areal extent of probably bedded anhydrite in the rocks . 10 Salina B unit west of the Findlay Arch . 26 7. Thickness of the Brassfield Formation . 11 20. Areal extent of anhydrite and anhydritic dolo- 8. Relationship between the sub-Lockport Silurian mite in the Salina C unit west of the Findlay rocks of the central Kentucky outcrop and Arch . 27 Adams County, Ohio, and those of the eastern 21. Pre-Devonian geology of northwestern Ohio . 28 part of the report area . 12 22. Postulated pre-Devonian outcrop of Salina G 9. Log cross section of the Cataract Group and anhydrite in eastern Portage Township and Dayton Formation through central Ohio . 13 western Catawba Island Township, Ottawa 10. Thickness of the Dayton Formation . 14 County . 29 11. Western limit of the Salina A, anhydrite, areas of 23. Thickness of supra-Goat Island chert-bearing Lockport outcrop, and areas in which Lockport dolomite in the Lockport Dolomite . 31 lithology is found in Salina rocks . 16 24. Cross sections of Lockport and Salina rocks . 33 12. Thickness of the Gasport Dolomite . 17 25. Areal extent of biostromal and biohermal 13. Thickness of the Goat Island Dolomite . 19 "Greenfield" dolomite . 3 5 14. Thickness of "representative" Guelph {bio- 26. Area where the Salina B unit may contain hermal? facies) in part of Townsend Township, economic deposits of gypsum . 37 Huron County . 20 27. Area where the Salina F unit may contain 15. Log cross section of carbonate bank in Guelph economic deposits of gypsum . 37 iii SILURIAN ROCKS IN THE SUBSURFACE OF NORTHWESTERN OHIO by Adriaan Janssens ABSTRACT The Silurian rocks in the subsurface of northwestern Ohio have oldest unit exposed at the surface in numerous quarries, where it been studied in the area from Erie County in the east to the Indiana consists of coarsely crystalline vuggy gray and white dolomite which line in the west and as far south as latitude 40° 45' N. The complete in the eastern part of the study area is overlain by and in facies stratigraphic succession consists, in ascending order, of the Cataract relationship with microcrystalline brown dolomite. The thickness of Group (Brassfield Formation and Cabot Head Formation), Dayton the Lockport in areas where the unit is overlain by a normal Salina Formation (expanded name), Rochester Formation, Lockport Group section ranges from 89 feet to about 200 feet. (Gasport Dolomite, Goat Island Dolomite, and Guelph Dolomite) or The contact of the Lockport with the Salina Group is considered Lockport Dolomite, Salina Group (units A through G in the east; regionally conformable, although there are a few wells and quarry Greenfield Dolomite, Tymochtee Dolomite, and undifferentiated sections where the contact is apparently disconformable. dolomite in the west), and Bass Islands Dolomite. The evaporites of the Salina Group of eastern Ohio extend into The Brassfield Formation is 25 to 65 feet thick and consists of the eastern tier of counties of the report area; for these rocks the largely dolomitized coarse-grained limestone that in its lower part in Salina nomenclature of eastern Ohio is used. The group consists, in the eastern half of the area is chert bearing, glauconitic, and silty. ascending order, of units A through G. In this area the salt beds are The formation grades into the overlying Cabot Head Formation, replaced by bedded anhydrite. The Salina Group is about 600 feet which is 60 to 115 feet thick where it can be differentiated and thick and is overlain by the Bass Islands Dolomite, a microcrystalline consists of interbedded green and reddish-brown shale and dolo- brown and gray dolomite that has an average thickness of 55 feet in mitized partly hematitic coarse-grained limestone. The Brassfield and the extreme northeastern part of the report area. To the west the Cabot Head are in facies relationship with the "Clinton" sandstone formation has been removed by post-Silurian, pre-Middle Devonian and shale of eastern Ohio. In the eastern part of the area the Cabot erosion. Head is overlain with sharp contact by the Dayton Formation, which In the western part of the report area the basal Salina unit is the is 5 to 57 feet thick and made up of two thin dolomitized limestone Greenfield Dolomite, a stromatolitic brown dolomite ranging in members that locally are separated from each other by as much as 15 thickness from 30 to 97 feet. It is overlain by the Tymochtee