Western Michigan University ScholarWorks at WMU Master's Theses Graduate College 8-1985 A Seismic Study of an Impact Feature in Cass County, Michigan Mancheol Suh Follow this and additional works at: https://scholarworks.wmich.edu/masters_theses Part of the Geology Commons Recommended Citation Suh, Mancheol, "A Seismic Study of an Impact Feature in Cass County, Michigan" (1985). Master's Theses. 1444. https://scholarworks.wmich.edu/masters_theses/1444 This Masters Thesis-Open Access is brought to you for free and open access by the Graduate College at ScholarWorks at WMU. It has been accepted for inclusion in Master's Theses by an authorized administrator of ScholarWorks at WMU. For more information, please contact [email protected]. A SEISMIC STUDY OP AN IMPACT FEATURE IN CASS COUNTY, MICHIGAN by Mancheol Suh A Thesis Submitted to the Faculty of The Graduate College in partial fulfillment of the requirements for the Degree of Master of Science Department of Geology Western Michigan University Kalamazoo/Michigan August 1985 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. A SEISMIC STUDY OP AN IMPACT FEATURE IN CASS COUNTY, MICHIGAN Mancheol Suh, M.S. Western Michigan University, 1985 A geophysical investigation, including a seismic study, of the subsurface structure of the Calvin-28 oil field, Cass County, Michigan, indicates that the structure's origin may be related to an impact event. The structural closures in the time structure maps and drilling results both show a central uplift. The fault system in the Trempealeau Formation shows a structure similar to other proven astroblemes. Undisturbed layers just beneath the central uplift also provide evidence of an impact structure. The result of mathematical modeling of the central .uplift under the assumption that the structure is an impact structure corresponds well with the drilling results. Therefore it may reasonable to accept the impact origin for the Cass County structure. The impact event occurred on the Utica shale of the Late Ordovician age. The diameter of the original crater was at least 2 kilometers. The mass of the meteorite was about 9 x 104 tons. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. ACKNOWLEDGEMENTS The author appreciates Dr. Gerry Clarkson of Western Michigan University for his suggestions and support during this research. He is also deeply grateful to Dr. W. Thomas Straw and Dr. William Harrison of Western Michigan University for their critiques of the manuscript during its preparation. He is also thankful to Mr. Robert Mannes and Mr. Ward Kelner of Mannes Oil Corp. and Mr. Douglas Daniels of the Michigan Department of Natural Resources for providing geological and geophysical information and for the permission to use their data in this thesis. Special thanks are extended to Mr. Moon Kim, Mr. Jongwook Lee, Miss Sandra K. Barnick, Mr. Saiful B. Baharom, and Mr. Russell G. Leviska for their help in field work and to Mr. Tom Thibeault for his help in field work and correcting the manuscript. Further thanks are extended to the Department of Geology of Western Michigan University for providing the GEOPRO 8012A seismograph, to the Academic Computer Center of Western Michigan University for providing computer time and to The Graduate College of Western Michigan University for funding the research. ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Finally, he also would like to express his deepest appreciation and thanks to his wife Kyong-sook for her help in drawing the figures and taking good care of him and his daughter Jee-Eun. Mancheol Suh iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. INFORMATION TO USERS This reproduction was made from a copy of a document sent to us for microfilming. While the most advanced technology has been used to photograph and reproduce this document, the quality of the reproduction is heavily dependent upon the quality of the material submitted. The following explanation of techniques is provided to help clarify markings or notations which may appear on this reproduction. 1.The sign or “target” for pages apparently lacking from the document photographed is “Missing Page(s)”. If it was possible to obtain the missing page(s) or section, they are spliced into the film along with adjacent pages. 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Dissertation contains pages with print at a slant, filmed as received_________ _ 16. Other________________________ ______________________________________________ University Microfilms International Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Repr o t e * w9h permlssion of the copyr|gh, owner; pumer reproduction ^ ^ TABLE OP CONTENTS ACKNOWLEDGEMENT ......................................... ii LIST OF TABLES ............................................... vi LIST OP FIGURES .............................. vii LIST OF PLATES .................. ix CHAPTER I. INTRODUCTION Objective ........................ 1 Location ............................ 3 Approach .............................................. 4 II. GEOLOGY ................................................. 7 III. GEOPHYSICAL EXPLORATION Gravity and magnetic survey ................ 11 Seismic survey ....................................... 14 IV. GENERAL ASPECTS OF AN IMPACT SITE Impact sites ......................................... 22 Geophysical characteristics of astroblemes ....... 27 Mathematical consideration of meteorites .......... 28 V. INTERPRETATION Geological results .......... 33 Gravity and magnetic results ........................ 38 Seismic results ................... 39 Mathematical modeling for isostatic uplift ...... 47 iv Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS CONTINUED CHAPTER Consideration of the meteorite .......... 49 VI. MODEL FOR FORMATION OF THE CASS COUNTY STRUCTURE ___ 51 VII. CONCLUSIONS ............ 53 BIBLIOGRAPHY....... 56 v Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OP TABLES 1. Stratigraphic Succession of the Study Area .......... 9 2. Meteorite Energy and Mass for Six North America Meteorite Craters ...... 32 vi Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. LIST OP FIGURES 1. Location Hap of the Study Area................. 5 2. Location Map of Drill Holes and Seismic Lines. ... 6 3. Basement Province Map of the Southern Peninsula of Michigan