2-D MODELING OF SOUTHERN OHIO BASED ON MAGNETIC FIELD INTENSITY, GRAVITY FILED INTENSITY AND WELL LOG DATA A Thesis Presented to The Graduate Faculty of The University of Akron In Partial Fulfillment of the Requirements for the Degree Master of Science Hussein M. Harbi December, 2005 ABSTRACT Results of magnetic and gravity data forward modeling, combined with existing well-log data, geologic information and seismic data provide new insights into the structural complexity of the Precambrian basement beneath southern Ohio. These results support previous hypotheses regarding the spatial extent of the Grenville Front Tectonic Zone (GFTZ). The set of nine modeled profiles also provide greater evidence that the GFTZ consists of a 25-35 km wide zone of east dipping structures in the Precambrian basement extending from mid- to southern Ohio. A previously identified anorthosite body is modeled at mid- to upper-crustal depths, but having an approximately 8o eastward dip. Farther east, the previously identified, west-dipping Coshocton zone is modeled as a set of structures that deepen to the west from mid- to lower crustal depths beneath east- central Ohio. The modeling further supports the contention that the Coshocton zone is associated with the New York-Alabama magnetic lineament. iii ACKNOWLEDGEMENTS I thank the Ohio Department of Natural Resources, Division of Geological Survey for their efforts in making the magnetic, gravity and wells data sets available. I would also like to acknowledge Dr. LaVerne Friberg and Dr. David McConnell for their helpful comments and reviews of this manuscript. I’d especially like to thank my advisor Dr. David Steer, for his encouragement and high expectations. I would like to acknowledge King Abdulaziz University, The Saudi Arabia cultural mission in the US and the department of geology in the University of Akron for their support. Also, I would like to express my gratitude to my wife, family and friends for their support and assistance. iv TABLE OF CONTENTS Page LIST OF TABLES …………………………………………………………… vii LIST OF FIGURES …………………………………………………………… ix CHAPTER I. INTRODUCTION………………………………………………………….. 1 II. GEOLOGY…………………………………………………………………. 3 1. Regional Geology…………………………………………………. 3 2. Magnetic and Gravity Anomaly Maps of Ohio…………………… 12 3. Wells and Lithology Distribution Maps…………………………... 16 III. METHODOLOGY…………………………………………………………. 20 1. Data Sets…………………………………………………………... 20 1.1. Magnetic Data…………………………………….……... 20 1.2. Gravity Data……………………………………………... 21 1.3. Wells and Lithologies Data……………………………… 21 2. Data Processing……………………………………………………. 22 2.1. Magnetic Data Processing……………………………….. 22 2.2. Bouguer Gravity Data Processing……………………….. 22 2.3. Wells and Lithology Data Processing…………………… 25 v 3. The 2D Magnetic and Gravity Forward Quantitative Modeling….. 25 3.1. Introduction……………………………………………… 25 3.2. Preparing Magnetic and Gravity Data…………………... 26 3.3. Magnetic and Gravity 2D Modeling…………………….. 27 IV. DATA DESCRIPTION…………………………………………………….. 41 V. INTERPRETATION……………………………………………………….. 72 VI. DISCUSSION………………………………………………………………. 75 VII. CONCLUSION…………………………………………………………….. 88 REFERENCES ………………………………………………………………… 91 APPENDIX ……………………………………………………………….... 94 vi LIST OF TABLES Table Page 1. East and West Ohio sequence stratigraphy and maps showing the rocks outcrop in Ohio……………………………………………………………. 9 2. Gridding geometries and Kriging parameters for the 29020 (Ohio State Plane NAD 27 unit (~11.6 km)) grid-interval……………………………... 23 3. Gridding geometries and Kriging parameters for the 0.089-degree (~ 10 km) grid-interval…………………………………………………………... 24 4. Gridding geometries and Kriging parameters for the 5011 (Ohio State Plane NAD 27 unit (~2 km)) grid-interval………………………………… 28 5. Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile A………………………………………………… 43 6. Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile B………………………………………………… 47 7. Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile C………………………………………………… 50 8. Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile D………………………………………………… 53 9. Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile E…………………………………………………. 56 10. Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile F…………………………………………………. 59 11. Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile G………………………………………………… 62 12. Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile H………………………………………………… 65 vii 13. Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile I………………………………………………….. 69 viii LIST OF FIGURES Figure Page 1. Paleoproterozoic and Mesoproterozoic crustal in central North America………………………………………………………………….… 4 2. Structure cross-section showing major arches and basins in Ohio………... 6 3. Index map of Ohio showing Precambrian terranes and major basement structures…………………………………………………………………... 8 4. General geologic map of Ohio…………………………………………….. 11 5. Reduced-To-Pole (RTP) magnetic anomaly map of Ohio…………….…... 14 6. Bouguer gravity map of Ohio……………………………………………... 15 7. Thickness variation of the Precambrian crust of Ohio with superimposted Phanerozoic features and instrumentally determined earthquake epicenters………………………………………………………………….. 17 8. Location and generalized interpreted lithologies for the Ohio basement wells in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems…………………………………………………………………….. 19 9. RTP magnetic color map of Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems, shows the location of the nine east- west profiles modeled by the present study……………………………….. 29 10. Bouguer gravity map of Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems shows the location of the nine east- west profiles modeled by the present study……………………………… 30 11. Reduced-to-pole magnetic anomaly (color map) overlaid by Bouguer gravity map (contour map) in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems………………………………………………. 31 ix 12. RTP magnetic color map of Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems created from extracted observed data over the east-west profiles………………………………………………… 33 13. Bouguer gravity map of southern Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems created from the extracted data from the 2 km-grid Bouguer gravity data over the east-west profiles…….. 34 14. Difference between observed magnetic data and the extracted-data over the east-west profiles in southern Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems………………………………… 35 15. Difference between observed gravity data and the extracted-data over the east-west profiles in southern Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems………………………………….. 36 16. Calculated RTP magnetic image of southern Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems, created from the calculated magnetic field over the east-west profiles……………………... 37 17. Calculated Bouguer gravity map of southern Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems created from the calculated Bouguer anomalies over the east-west profiles………………... 38 18. Difference between calculated and measured magnetic field over the study area in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems……………………………………………………….. 39 19. Difference between calculated and measured Bouguer gravity field over the study area in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems……………………………………………………….. 40 20. East-West cross-section models for profile A, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line)………………………………………………………………………... 42 21. East-West cross-section models for profile B, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line)………………………………………………………... 46 22. East-West cross-section models for profile C, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line)……………………………………………………….……………….. 49 x 23. East-West cross-section models for profile D, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line)………………………………………………………………………... 52 24. East-West cross-section models for profile E, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line)……………………………………………………………………….. 55 25. East-West cross-section models for profile F, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line)………………………………………………………………………... 58 26. East-West cross-section models for profile G, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line)………………………………………………………………………... 61 27. East-West cross-section models for profile H, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line)………………………………………………………………………... 64 28. East-West cross-section models for profile I, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line)………………………………………………………………………... 68 29. Reduced-To-Pole (RTP) magnetic anomaly map of Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates system………………. 70