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
30. Bouguer gravity map of Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems………………………………………... 71
31. Standard geologic models for correlation the magnetic and gravity field anomalies of Ohio a) Generalized crustal susceptibilities and densities in Ohio from Lucius and von Frese, 1988. b) Generalized lithologic correlation models between magnetic and gravity anomalies from von Frese et al., 1997…………………………………………………………... 77
32. General basement provinces (Grenville province and East Granite Rhyolite Province (EGRP), East Continent Rift Basin (ECRB), Tri-State Caldera (TSC), and Grenville Front Tectonic Zone (GFTZ)……………… 80
33. Possible interpretation of COCORP-OH1 and OH-2 seismic lines by Pratt et al., 1989…………………………………………………………………. 83
34. Ohio and adjacent states magnetic map…………………………………… 84
xi 35. The expected lateral ramp movement in central Ohio along the flanks of the anorthosite body (Steigerwalt, R., 2002)……………………………… 87
36. General crustal structure of southern Ohio………………………………... 90
xii CHAPTER I
INTRODUCTION
The nature of the Precambrian basement underlying Ohio is poorly constrained because of a lack of surface exposures and its great depth. These units are buried beneath younger Paleozoic rocks at depths ranging from ~700 m in western Ohio to more than
3,900 m in southeastern Ohio (Hansen, 1996). Much of what is known about these ancient units is derived from the petrology of sparsely scattered, basement-penetrating samples collected from oil and gas wells and other boreholes (Lucius and Von Frese,
1988). Indirect geophysical methods such as analysis of aeromagnetic and gravity data, reflection seismic data, and the study of the earthquake wave propagation have provided more general information regarding their spatial extent (Hansen, 1996). In 1984, the U.S.
Geological Survey, in cooperation with the Ohio Geological Survey, published gravity and aeromagnetic data for Ohio. Shortly thereafter (1987), an east-west deep seismic reflection profile was acquired across central Ohio as part of the nationwide COCORP
(Consortium for Continental Reflection Profiling) project. These data demonstrated that there is substantial complexity in the Precambrian basement structure of Ohio.
Several features have been identified in the geophysical data that give insights into the Precambrian tectonics of this region. Magnetic and gravity field anomalies located in south-central Ohio were interpreted to be associated with an anorthosite body that may
1 have been related to a paleo-rift system (Lucius and Von Frese, 1988). Steigerwalt
(2002) suggested that this plutonic body was positioned in the crust such that it may have acted as rigid body during a shallow east-west directed thrust event. Such compression may have created a means for lateral movement along the flanks of the pluton. Several other large-scale ramp systems associated with ancient collisional tectonic settings were identified in the COCORP data reported by Cullotta et al. (1990).
This study used existing magnetic, gravity and well-log data in combination with geologic and seismic information to enhance understanding of the lithology, structure and tectonic history of the Ohio basement. Nine, 2D magnetic and gravity quantitative models were developed to study the region surrounding the inferred anorthosite body in southern
Ohio. These models were used to define the major structural and lithological features of the crust of Ohio that were reflected in the magnetic and gravity signatures and that were consistent with the existing seismic models. Specifically, this study used magnetic and gravity models to explore the existence, spatial extent and nature of complex basement structures in the Precambrian basement.
2
CHAPTER II
GEOLOGY
1. Regional Geology
Much of the eastern midcontinent that forms the basement of Indiana, Kentucky,
Ohio and Pennsylvania is blanketed by a thick sequence of sub-horizontal Phanerozoic sedimentary rocks. It is underlain to the west by the granite-rhyolite province and by the
Grenville province to the east (Drahovzal et al., 1992). The ~11 km thick, eastern granite- rhyolite province formed between 1400 -1500 Ma and is composed mainly of rhyolite and epizonal and mesozonal granite plutons similar to those exposed in the St. Francois
Mountains of southeastern Missouri (Van Schmus et al., 1996; Drahovzal et al., 1992;
Bickford et al., 1986). The western part, the Grenville province, is composed of medium to high-grade metamorphic rocks (Lucius and von Frese, 1988).
The accepted tectonic history of the east midcontinent begins with formation of the granite-rhyolite province. It is thought to have formed from anatectic melting of preexisting Paleoproterozoic crust (Van Schmus et al., 1996). This development was followed by the Keweenawan rifting (The Midcontinent Rift) (1.05-1.3 Ga) along an area that extends more than 2000 km from northeast Kansas to Lake Superior, and then south to southeast Michigan (Figure 1) (Van Schmus et al., 1996; Cannon, 1994). The southeastern Michigan extension continues into western Ohio and Kentucky forming the
3
ovince, nCP = north Central Plains orogen, sCP -rhyolite province, K = Killarney region of Ontario, ustal in central North America. CB = Cheyenne granite-rhyolite province, WM = Wichita Mountains Figure 1: Paleoproterozoic and Mesoproterozoic cr belt, Mv = Mojave province, EGR eastern granite MCR = Midcontinent rift system, Mz Mazatzal pr southern Central Plains orogen, SGR = magmatic province, and Y = Yavapai province (Van Schmus et al., 1996).
4 East Continent Rift Basin (ECRB), Fort Wayne Rift (FWR), Flatrock subbasin, English
Graben (southern Indiana), and the South Indiana Graben (Stark, 1997; Atekwana, 1996;
Dickas et al., 1992). Basalt appeared to have flowed upward as erosion began to fill the
ECRB with clastic sediment. This deposit is known as the Middle Run Formation in western Ohio (Figure 2) (Atekwana, 1996; Dickas et al., 1992, Drahovzal et al. 1992).
The Middle Run Formation, which is a Precambrian age, extends about 160 km north- south and 48 km east-west from Putnam County, in northern Ohio, south to Jessamine
County, Kentucky, into west Fayette County, Indiana (Drahovzal et al. 1992, Potter et al.,
1991).
Keweenawan rifting was followed by a continent-continent collision between the east continent, Baltica, and North America between 990 and 880 Ma resulting in extensive crustal compression and development of the Grenville Mountains (Figure 1 and
2) (Drahovzal et al., 1992). Grenville rocks consist of east-dipping amphibolite- to granulite-grade metamorphic rocks, gneisses and anorthosite that underlie central to eastern Ohio. The 4000 km long Grenville Front is the boundary between the Grenville province and the older structural provinces to the west, the East Continent Rift Basin
(ECRB) and the east granite-rhyolite province (Figures 1 and 2) (Drahovzal et al., 1992).
The Grenville Front cuts north-south across the ECRB so that only the deeper parts of the basin and overthrusts of the east granite-rhyolite province remain today (Figure 2)
(Drahovzal et al., 1992). In east-central Ohio, the Coshocton zone is characterized as a west-dipping unit within the Grenville province that was interpreted to be a suture zone by Culotta et al., (1990) (Pratt, et al., 1989; Culotta et al., 1990; Shumaker and Wilson,
1996). This zone projects up dip toward the New York-Alabama magnetic lineament (one
5
jor arches and basins in Ohio. Insert Formation Middle Run map shows location of line section (Root and Onasch, 1999). Figure 2: Structure cross-section showing ma
6 of the prominent magnetic anomalies in eastern North America) that extends from north
Alabama through eastern Tennessee to central West Virginia (Culotta et al., 1990). In northwest Ohio, two faults zones, the Bowling Green fault and the Outlet fault, are interpreted to be related to the Grenville front by Root (1996) (Figure 3).
Before deposition of early Cambrian sediments, the area was deeply eroded removing the Grenville foreland basin and the Grenville Mountains (Drahovzal et al.,
1992; Stark, 1997). After this long period of erosion between 650-560 Ma, an extension associated with the opening of the Iapetus Oceans formed a series of half-graben faults within areas west and east of the Grenville front forming the Rough Creek Graben and the Rome Trough (Figure 3). However, the Rome Trough, south and east of Ohio, north
Kentucky, West Virginia and west Pennsylvania, was the site of accumulation of a thick sequence of Cambrian sediments. It has been the focus of attention in recent years because of its recently documented hydrocarbon potential (Harris and Baranoski, 1996).
Areas east of the Grenville front, near the East Continent Basin central Kentucky and western Ohio, remained stable during this time (Drahovzal et al., 1992; Stark, 1997;
Harris and Baranoski, 1996). The basal Cambrian rock unit in most of Ohio is the Mt.
Simon Sandstone (Figure 2 and Table 1). In eastern Ohio, carbonate deposition, primarily dolomite, formed the Rome Formation (Figure 2 and Table 2). Overlaying the Rome
Formation in east Ohio is the Canasaugua Formation, which consists of shale, siltstone, fine-grained sandstone, and limestone toward the south (Table 1) (Beardsley and Cable,
1983; Hansen, 1997).
The Iapetus Ocean basin, which formed during Cambrian age, began to close by
Ordovician time resulting from a collision between the North American (Laurentia) and
7
Figure 3: Index map of Ohio showing Precambrian terranes and major basement structures (Root, S., 1996)
8 Table 1: East and West Ohio sequence stratigraphy and maps showing the rocks outcrop in Ohio (Hansen, 1996, Winter 1997, Fall 1997, 1998, 2001; Harris and Baranoski, 1996; and UIC REPERMIT APPLICATION WELL NO.1 AND NO.2, ENVIROCRP PROJECT NO. 30-1488, 1991, prepared by: ENVIROCORP SERVIES & TECHNOLOGY, INC. SOUTH BEBD, INDIANA). 9
the European continents (Baltica) creating the Taconic orogeny (Shumaker and Wilson,
1996; Hansen, 1997). However, this orogeny is one of three tectonic orogenies during
Paleozoic time that assembled the east midcontinent basement. As the two plates collided, an extensive amount of uplifting and fracturing occurred within the edges of the continents, which now make up the Taconic Mountains in eastern New York (Frazier and
Schwimmer, 1987). As the mountains rose to the east, the western portion of the collision zone subsided and formed a deep-water foreland basin called the Appalachian Basin in eastern Ohio (Figure 2) (Shumaker and Wilson, 1996). The Cincinnati Arch, southwestern Ohio, was initiated by the Taconic Orogeny during the late Ordovician
(Figure 2). The axis of this arch is east of Cincinnati and continues northwest until it splits into the Findlay Arch to the north and the Kankakee Arch to the west. The broad area formed by these three arches is called the Indiana-Ohio platform (Root and Onasch,
1999). The upper part of Knox Dolomite is early Ordovician rock and overlain by the
Wells Creek Formation that underlies the Black River Group (Figure 2 and 4; Table 1).
This is overlain the Trenton Limestone and the Cincinnati Group (Table 1) (Hansen,
1997).
The Acadian orogeny, the second orogeny in the Paleozoic age, occurred during
Silurian and Devonian period when the Laurentia (North American continent) collided with a micro continent (Avalonia) in the Proto-Atlantic Ocean, which is also known as the Iapetus Ocean. This collision continued to create the Appalachian mountain chain, which was started during the Ordovician age by the Taconic orogeny (Shumaker and
Wilson, 1996; Hansen, 1998). Ohio was in tropical latitudes south of the equator and was covered with warm shallow seas during this period creating Silurian and Devonian rocks
10
Figure 4: General geologic map of Ohio (Department of Natural Resources, Division of geological Survey, created by Bob Taft, Samuel W. Speck, and Thomas M. Berg).
11 composed of limestone, dolomite, gypsum, anhydrite, and halite of the Cataract Group,
Clinton Group, Salina Group, and Ohio shale (Figure 2, 4 and Table 1) (Hansen, 1998).
Mississippian rocks reflect a sharp change in depositional environments in Ohio. As the Devonian-age Acadian highlands deltas to the east were eroded and then carried into the Ohio basin, they created muddy to sandy seas. Up to 300 m of strata that include
Bedford, Berea, Sunbury, and Cuyahoga formations were deposited (Figure 2, 4 and
Table 1) (Hansen, 2001). The third orogeny is the Allegheny orogeny, also named the
Appalachian, which occurred in Permian and ended the last phase of continent collisions of Laurussia (Proto- North America and Proto-Europe) with West Gondwana (Proto-
Africa and Proto-South America) (Shumaker and Wilson, 1996). As a result of these three orogenies, the Appalachian mountain chain was created to the east, and the area west of the collision zone bent and folded forming the Appalachian basin. In the Triassic and Jurassic Periods of the Mesozoic Era, North America and Africa began to pull apart.
This was the beginning of the modern Atlantic Ocean, which continues to expand even today as North America and Africa drift farther apart (Frazier and Schwimmer, 1987).
2. Magnetic and Gravity Anomaly Maps of Ohio
In 1984 the U.S. Geological Survey and the Ohio Geological Survey published surface gravity and aeromagnetic data of Ohio (Figures 5 and 6). These data have been used by several researchers to map lithological and structural features of the Ohio basement. For instance, in the gravity map (Figure 6), a gravity high that crosses northwest Ohio extends from southeastern Michigan into north-central Tennessee
(Drahovzal et al., 1992). This feature was named the East Continent Gravity High by
12
Bryan (1975) (Drahovzal et al., 1992). It is interpreted to be a rift system, named the East
Continent Rift System and the Fort Wayne rift (FWR), and assumed to be an extension of
the well-Known Keweenawan Rift System that was described by several researchers
(Lucius and von Frese, 1988; Drahovzal et al., 1992; von Frese et al., 1997; and Kim et
al., 2000). The East Continent Rift Basin, including the Middle Run Formation in western
Ohio, represents a structural basin feature that is related to the East Content Rift System
(ECRS). The ECRS is, in turn, an extension of the Keweenawan Rift System to the
north (Lucius and von Frese, 1988; Drahovzal et al., 1992; von Frese et al., 1997; and
Kim et al., 2000). However, since this feature does not have the same magnetic signature
as the Keweenawan Rift System, Richard et al., (1997) interpreted the feature to be younger than the GFTZ, forming either in the Eocambrian or Early Cambrian. Another well-delineated zone in the magnetic data (The north south heavy white line in Figure 5) was interpreted to be the Grenville Front Tectonic Zone (GFTZ) (Lucius and von Frese,
1988; Culotta et al., 1990; Drahovzal et al., 1992; Richard et al., 1997; von Frese et al.,
1997; and Kim et al., 2000), which is a transition zone between the East Granite-Rhyolite
Province (EGRP) to the west and the Grenville Province to the east of Ohio. It formed during the Grenville orogeny that now is defined by a 10 to 100 km wide zone of anomalies in the geophysical data.
Lucius and von Frese (1988) created five east-west magnetic and gravity traverses to explain anomalies observed in the data across Ohio. These models were followed by a spectral correlation study of magnetic and gravity anomalies of Ohio by von Frese et al.,
(1997). The positive magnetic and gravity anomalies in Seneca and Sandusky Counties to the north and in Butler County to the southwest of Ohio (Anomaly S and B in Figures 5
13
85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W 81°0'0"W 80°30'0"W
42°0'0"N Michigan Lake Erie 1400000
41°30'0"N 1200000 S 1,200,000 41°0'0"N
1000000
40°30'0"N Pennsylvania 800000 Indiana 800,000
40°0'0"N
600000 GFTZ
39°30'0"N 1600 B 1400 1200
1000
800 400000 A 600 400,000 39°0'0"N 400
200
0
-200
-400 200000 ® -600 West Virginia 38°30'0"N -800 025507510012.5 Kentucky -1000nT 1400000Kilometers 1600000 1800000 2000000 2200000 2400000nT
1,200,000 84°0'0"W1,600,000 83°30'0"W 83°0'0"W 2,000,000 2,400,000
Figure 5: Reduced-To-Pole (RTP) magnetic anomaly map of Ohio. S = Seneca Anomaly, B = Butler Anomaly, A = Anorthosite complex anomaly, and GFTZ = Grenville Front Tectonic Zone. Contour Interval (CI) = 100 nT
14
85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W 81°0'0"W 80°30'0"W -84.50 -84.00 -83.50 -83.00 -82.50 -82.00 -81.50 -81.00 -80.50
Michigan 42.00 42°0'0"N Lake Erie
41°30'0"N 41.50 S 1,200,000 41°0'0"N 41.00
40°30'0"N 40.50 Pennsylvania Indiana
800,000
40°0'0"N 40.00
FWR 15 10 5
0 39°30'0"N A -5 39.50 -10 B -15 -20 -25 -30 mgal -35 400,000 39°0'0"N -40 39.00 -45 -50 -55 -60 -65 ® -70 West Virginia 38°30'0"N 012.5 25 50 75 100 -75 38.5038°30'0"N Kentucky -80 Kilometers -85
85°0'0"W1,200,000 1,600,000 2,000,000 2,400,000
Figure 6: Bouguer gravity map of Ohio. S = Seneca Anomaly, B = Butler Anomaly, A = Anorthosite complex anomaly, and FWR = Fort Wayne Rift. (CI) = 5 mgal.
15 and 6) were interpreted to be caused by the presence of shallow mafic sources. In 1985, the Ohio Department of Natural Resources, Division of Geological Survey, drilled a test hole above the Seneca anomaly (anomaly S in Figure 5 and 6) that recovered ~20 m of gabbro core. This discovery validated the previous interpretations (Lucius and von Frese,
1988; Van Schmus et al., 1996). In south-central Ohio, correlating gravity and magnetic anomalies (Anomaly A in Figure 5 and 6) were interpreted by Lucius and von Frese,
(1988) to be an anorthosite body that formed in lower crust. Because of uplift and erosion during the Grenville orogeny, this body is now positioned at intermediate depth.
Kim et al., (2000) used spectral correlation theory to analyze terrain gravity effects and free-air gravity anomalies of Ohio in order to constrain crustal thickness models and to explore possible neotectonic scenarios of crustal evolution. Their results (Figure 7) illustrated that crustal thickness variations were consistent with a broad zone of thickened crust across the middle third of Ohio (Figure 7; white dashed line). Kim et al., (2000) suggested there were also crustal features possibly related to crustal rifting and thrusting
(Kim et al., 2000).
3. Wells and Lithology Distribution Maps
There are a total of 202 basement-penetrating wells in Ohio (as of 2004) as reported by the Ohio Department of Natural Resources, Division of Geological Survey.
Lithological descriptions of 113 of these wells (Figure 8 and Appendix A) were used to correlate and constrain magnetic and gravity data and models. Using these data, the
Precambrian basement in Ohio can be divided into east and west provinces of different lithology separated by a transition (see the north-south dashed lines in Figure 8). The
16
Figure 7: Thickness variation of the Precambrian crust of Ohio with superimposted Phanerozoic features and instrumentally determined earthquake epicenters. Thick, white dashed lines roughly delineated the inferred broad zone of thickened crust in the middle third of the state, with features possibly related to crustal rifting and thrusting (Kim, et al., 2000).
17 eastern province, eastern Ohio, contains mostly medium to high grade metamorphic rocks that include schist, amphibolite, gneiss, and granite gneiss. The granite gneiss was exposed mostly in north-central Ohio whereas most of eastern and southeastern Ohio contains amphibolite rocks (Figure 8). To the west, the basement contains igneous rocks such as granite and rhyolite rocks though several wells also contain mafic and intermediate composition rocks. The north-south transition zone between the east and west provinces is characterized by a mélange (Figure 8). The zone is spatially more than
100 km wide in northern Ohio decreasing in width to less than 50 km in central and southern Ohio. This zone is characterized by wells that penetrate more than 300 m of dolomitic marble in Fayette and Pickaway Counties central Ohio.
18
85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W 81°0'0"W 80°30'0"W -84.50-84.50-84.50 -84.00 -84.00 -84.00 -83.50 -83.50 -83.50 -83.00 -83.00 -83.00 -82.50 -82.50 -82.00 -82.00 -81.50 -81.50 -81.00 -81.00 -81.00 -80.50 -80.50 -80.50
42°0'0"N Michigan Lake Erie 42.0042.00
41°30'0"N 41.5041.50
1,200,000
41°0'0"N 41.0041.00 Pennsylvania Indiana
40°30'0"N 40.5040.50
800,000
40°0'0"N 40.0040.00
39°30'0"N 39.5039.50
Lithic arenite Mafic rocks Intermediate rocks 400,000 39°0'0"N 39.0039.0039°0'0"N ( Granite 39.00 ) Rhyolite Gneiss or granite gneiss ® Y Amphibolite S Schist, Hornfels, or marble 38°30'0"N 38.5038.50 025507510012.5 E Kentucky Wells penetrate basement Kilometers West Virginia (no sample or indeterment)
85°0'0"W1,200,000 1,600,000 83°30'0"W 82°30'0"W2,000,000 2,400,00081°0'0"W
Figure 8: Location and generalized interpreted lithologies for the Ohio basement wells in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems. Blue dashed lines approximate the transition zone between east and west lithologically difference provinces.
19 CHAPTER III
METHODOLOGY
1. Data Sets
1.1. Magnetic Data
The magnetic data used in this study were downloaded from the Ohio Department of Natural Resources, Division of Geological Survey website as digital data for the public via FTP files. These data were compiled from several sources by Thomas G. Hildenbrand and Robert P. Kucks of the U.S. Geological Survey to produce a series of magnetic anomaly maps of Ohio. These maps have been published in two releases (Hildenbrand and Kucks, 1984 and 1987). The downloaded data set contains East Central US, Reduced to North Pole (RTP), first vertical derivative, second vertical derivative magnetic data and magnitude of gradient of pseudo-gravity data. The RTP magnetic data (116528 records), which are reduced to north pole using inclination of 70o and declination of –4o in transforming parameters, were used in this study to produce RTP magnetic maps for qualitative interpretations and to provide data for 2D forward magnetic quantitative modeling.
20
1.2. Gravity Data
The gravity data set (6,591 records) used in this study is gridded data prepared from the complete Bouguer gravity anomaly data set for Ohio. These data were developed from a series of data sets including those of: Hittelman, A., D. Dater, R. Buhmann, and S.
Racey, 1994, Gravity CD-ROM and User’s Manual (1994 Edition); National Oceanic and
Atmospheric Administration, National Geophysical Data Center, Boulder, Colorado, by the Ohio Department of Natural resources, Division of Geological Survey. The data were downloaded from the Ohio Department of Natural Resources, Division of Geological
Survey website as a digital data from the public FTP files. This data set includes observed gravity, Free-air anomalies, and Bouguer anomalies of Ohio. The Bouguer anomaly data set, which is the residual value obtained after latitude correction, elevation correction
(including both free-air and Bouguer corrections) and terrain corrections, was used in this study to produce a Bouguer gravity map for qualitative interpretation and data for 2D forward quantitative modeling.
1.3. Wells and Lithologies Data
The Ohio Department of Natural Resources, Division of Geological Survey also offers computer-generated oil and gas well-spot maps and digital data files for more than
5,000 wells in Ohio. These data provide locations and some depths for wells that penetrate Phanerozoic formations and Precambrian surfaces in Ohio. Data for basement- penetrating wells were downloaded via FTP files from the Ohio Department of Natural
Resources, Division of Geological Survey website as a digital data. In addition, published
Precambrian lithology reports of Janssens, J. (1973), Lucius, J. (1985); Lucius and von
21
Frese, (1988); Shrake et al., (1990); and Von Frese et al., (1997) were used to constrain
the models.
2. Data Processing
2.1. Magnetic Data Processing
The reduced-to-pole (RTP) magnetic data set is accessible in Ohio State Plane NAD
27, south zone. These data were downloaded and gridded using Surfer™ software
(Golden Software series) using 29020 (Ohio State Plane NAD 27 unit) grid-interval
(~11.6 km) and the Kriging gridding method (Table 2). This gridding technique produced
a 134 square-km grid (in a total of 43 columns and 50 rows), which was used in creating
the RTP magnetic anomaly contour map using Surfer™ software. RTP magnetic contour
maps of Ohio were edited and modified with Ohio counties map using ArcMap (Figure
5). These maps were used for the qualitative interpretations and correlation with gravity
anomalies, wells and lithologies, and structure maps for better understanding of the
lithologic distribution, structure, and tectonic history of the Ohio basement rocks.
2.2. Bouguer Gravity Data Processing
The Bouguer Gravity data set was re-gridded using (0.089 degree) grid-interval (~
10 km) and Kriging gridding method by Surfer™ software (Table 3). These properties produced a grid data of 100 square-km grid size (in 50 columns and 44 rows), which was used in creating the Bouguer Gravity contour map of Ohio using Surfer™ software. The
Bouguer gravity anomaly contour maps (Figure 6) were edited and modified with the
Ohio counties map using ArcMap.
22
Table 2: Gridding geometries and Kriging parameters for the 29020 (Ohio State Plane NAD 27 unit (~11.6 km)) grid-interval.
Grid Line Geometry Minimum Maximum Spacing No. of lines X Direction 1333670 2552510 29020 43 Y Direction 148058 1573860 29020 50
Gridding Method: Kriging Options: Type Scale (C) Length (A) Component 1: Linear 63600 938000 Component 2: None - - Component 2: None
Nugget Effect: Error Variation 0 Micro Variation 0
Drift Type: No drift
Variation Anisotropy: Ratio 1 Angle 0
23
Table 3: Gridding geometries and Kriging parameters for the 0.089-degree (~ 10 km) grid-interval.
Grid Line Geometry Minimum Maximum Spacing No. of lines X Direction -84.8552 -80.4817 0.0892551 50 Y Direction 38.4038 42.2667 0.0898349 44
Gridding Method: Kriging Options: Type Scale (C) Length (A) Component 1: Linear 230 2.92 Component 2: None - - Component 2: None
Nugget Effect: Error Variation 0 Micro Variation 0
Drift Type: No drift
Variation Anisotropy: Ratio 1 Angle 0
24 2.3. Wells and Lithology Data Processing
A total of 202 records of wells that penetrate the Precambrian surface in Ohio
(Figure 8) were extracted from 5126 wells records using Excel software (Microsoft
Software series). The data were sorted (using the sorting option in Excel software) based
on the formations that the wells penetrated. These data provide well locations, including
counties and township, permit number, and some depths to the Precambrian surface in
Ohio. Well location data were all converted to the geographic coordinates system NAD27
using coordinates conversion software (CORPSCON for Windows Version 5.11.08),
which can be downloaded free of charge from the Ohio Department of Natural
Resources, Division of Geological Survey. Also, general Precambrian lithology descriptions, well penetration depths in the Ohio Precambrian surface, and some overall well depths were taken from Janssens, J., (1973); Lucius, J., (1985); Lucius and von
Frese, (1988); Shrake et al., (1990); and Von Frese et al., (1997) (Appendix A). The locations and general lithologies for available wells that penetrate the Precambrian in
Ohio are displayed in Figure 8. This map was used to support the magnetic and gravity qualitative interpretation and to identify some lithologies and depths for the 2D forward magnetic and gravity quantitative modeling.
3. The 2D Magnetic and Gravity Forward Quantitative Modeling
3.1. Introduction
Variations in structure and lithology of the crust are frequently reflected in magnetic and gravity anomalies (Lucius, J., 1985). Detailed structure and lithologies can therefore be constructed based on magnetic and gravity anomalies using 2D or 3D
25 modeling. Gravity and magnetic forward modeling software uses a simple idea to simulate the geologic sources for a complex system. The proposed shape and physical parameters for a subsurface body are entered in the model. Anomalies are calculated and then compared with observed magnetic and gravity anomalies. The model is manually iterated until there is an acceptable match (both numerically and geologically) between the synthetic and actual data. This was the process used in this study to model Ohio’s crust and upper mantle from the available RTP magnetic and Bouguer gravity data.
3.2. Preparing Magnetic and Gravity Data
Potent™ software, which is a magnetic and gravity 2D and 3D modeling software from Rockware software series, was used in this study to create the 2D magnetic and gravity models in southern Ohio. First, the Bouguer gravity data were converted from the geographic coordinate system (NAD27) to the Ohio state plane system NAD 27 using
CORPSCON software (and to be consistent with the RTP magnetic data). The two data sets, the RTP magnetic and the Bouguer gravity data, were gridded using Surfer™ at a 2 km grid interval (5020 NAD27 unit) in the X and Y directions using the Kriging method
(Table 4). This step over sampled the gravity data, but reduced the magnetic data grid to a more manageable database size. Data were saved as grid files (GRD format). The grid files were then imported by Surfer™ software using the Grid Node Editor and saved as
DAT files. The produced DAT files were ready to be imported into Potent™ software.
26
3.3. Magnetic and Gravity 2D Modeling
The 2 km grid-interval DAT files were imported using Potent™ software producing color RTP magnetic and Bouguer gravity maps of Ohio (Figures 9 and 10). RTP magnetic color maps were imported in ArcMap software and were overlain by a Bouguer gravity contour map to produce a magnetic-gravity map (Figure 11). These maps were used to facilitate the correlation process between anomalies in Ohio.
Nine east-west data profiles crossing the expected anorthosite complex in south- central Ohio and part of the East Continent Rift System were extracted (see profile locations on Figure 9). An ~32 km interval was selected between profiles with the profile descriptions starting at profile A in the north and ending in the south at profile I (Figures
9 and 10). The Select Profile option in Potent™ software was used to extract the data across these profiles. This data extraction option provided data in XY format (X is the east-west distance and Y is the magnetic or gravity anomaly values). Another option in the software reordered the data and allowed annotation of the lateral location. Potent™ then output the data in an XYZ file format. Each data file then consisted of a profile with
X values for the east-west locations, Y values for the north-south locations (constant for each profile), and Z values corresponding to magnetic or gravity anomaly values.
The nine XYZ format files, which contained data for the nine profiles, were imported and edited by Excel software producing a single data file. The data were re- gridded at an ~6 km grid-interval (15000 NAD27 unit) using the Kriging gridding method in Surfer™. The grid data were saved as a DAT file using the Grid Node Editor option in Surfer™ software. Then the 6-km-grid DAT file was imported using Potent™ software to produce color magnetic and gravity maps for southern Ohio (Figures 12 and
27
Table 4: Gridding geometries and Kriging parameters for the 5011 (Ohio State Plane NAD 27 unit) (~2 km) grid-interval.
Grid Line Geometry Minimum Maximum Spacing No. of lines X Direction 1333670 2552510 5011.6 239 Y Direction 232007 886319 5033.17 131
Gridding Method: Kriging Options: Type Scale (C) Length (A) Component 1: Linear 210 680000 Component 2: None - - Component 2: None
Nugget Effect: Error Variation 0 Micro Variation 0
Drift Type: No drift
Variation Anisotropy: Ratio 1 Angle 0
28 85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W Observed81°0'0"W 80°30'0"W - TMI
42°0'0"N Michigan Lake Erie Lake Erie
41°30'0"N
1,200,000
41°0'0"N
40°30'0"N A Pennsylvania Indiana B 800,000
40°0'0"N C D E 39°30'0"N F 2176 nT G 400,000 39°0'0"N H ® I 025507510012.5 West Virginia 38°30'0"N Kentucky WestbVirginia 38°30'0"N Kilometers -1333 nT
20000085°0'0"W1,200,000X(m) 16000001,600,000 20000002,000,000 24000002,400,000
Figure 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
85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W 81°0'0"WObserved80°30'0"W - Gz
42°0'0"N Michigan Lake Erie
41°30'0"N
1,200,000
41°0'0"N
40°30'0"N A Pennsylvania Indiana B 800,000 40°0'0"N C D
39°30'0"N E F 40 mgal
G 400,000 39°0'0"N H I ® I West Virginia 38°30'0"N 025507510012.5 38°30'0"N Kentucky Kilometers -40 mgal
20000085°0'0"W1,200,000X(m) 16000001,600,000 20000002,000,000 24000002,400,000
Figure 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
85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W Observed81°0'0"W 80°30'0"W - TMI -84.50 -84.00 -83.50 -83.00 -82.50 -82.00 -81.50 -81.00 -80.50
42°0'0"N Michigan Lake Erie 42.00
41°30'0"N 41.50
1,200,000
41°0'0"N 41.00
40°30'0"N 40.50 Pennsylvania Indiana
800,000
40°0'0"N 40.00
39°30'0"N Magnetic 39.50 2176 nT
400,000 Gravity 39°0'0"N 39.00 Max. Min. ® CI = 5 mgal 38°30'0"N 025507510012.5 38.5038°30'0"N Kentucky West Virginia Kilometers -1333 nT
2000001,200,000X(m) 16000001,600,000 20000002,000,000 24000002,400,000 Figure 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 13). These data were then subtracted from the original data (Figures 14 and 15) to ensure that nine profiles were sufficient to preserve significant features in the original data.
In the 2D modeling, geologically feasible polygons and cylindrical bodies were modeled for each profile. Concurrently, Potent™ software allowed creation of 2D and 3D models. This option allowed out-of-plane contributions to the selected profile even when the profile did not cross the body. Magnetic susceptibility, densities values and depths used to model the source bodies were consistent data from well logs (Appendix A) and previous seismic studies (Culotta et al., 1990; Pratt et al., 1989; Shrake et al.; a and b
1991; Richard et al., 1997; von Frese et al., 1997).
Lastly, outputs from the models were used to generate 2-D aerial-extent models for comparison with the original data. Model data were gridded in ~6 km interval using the
Kriging gridding method and then saved as DAT file using Surfer™ software. The DAT file was imported by Potent™ and used to produce calculated magnetic and gravity maps for southern Ohio (Figures 16 and 17). These data were then subtracted from the original data (shown in Figures 18 and 19). Discrepancies on the difference map were resolved by adjusting the model and repeating the procedure.
32
85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W Observed81°0'0"W 80°30'0"W - TMI
42°0'0"N Michigan Lake Erie
41°30'0"N
1,200,000
41°0'0"N
40°30'0"N Pennsylvania Indiana
800,000
40°0'0"N
39°30'0"N 2176 nT
400,000 39°0'0"N ® 38°30'0"N 025507510012.5 West Virginia 38°30'0"N Kentucky Kilometers -1333 nT
20000085°0'0"W1,200,000X(m) 16000001,600,000 20000002,000,000 24000002,400,000
Figure 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
85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W 81°0'0"WObserved80°30'0"W - Gz
42°0'0"N Michigan Lake Erie
41°30'0"N
1,200,000
41°0'0"N
40°30'0"N Pennsylvania Indiana 800,000
40°0'0"N
39°30'0"N
40 mgal
400,000 39°0'0"N ® West Virginia 38°30'0"N 025507510012.5 38°30'0"N Kentucky Kilometers -40 mgal
20000085°0'0"W1,200,000X(m) 16000001,600,000 20000002,000,000 24000002,400,000
Figure 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
85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W Observed81°0'0"W 80°30'0"W - TMI
42°0'0"N Michigan Lake Erie
41°30'0"N 41°30'0"N
1,200,000
41°0'0"N
40°30'0"N Pennsylvania Indiana
800,000
40°0'0"N
39°30'0"N 2176 nT
400,000 39°0'0"N ® 38°30'0"N 012.5 25 50 75 100 West Virginia Kentucky Kilometers -1333 nT
000 1,200,000X(m) 16000001,600,000 20000002,000,000 24000002,400,000 2800
Figure 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 85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W 81°0'0"WObserved80°30'0"W - Gz
42°0'0"N Michigan Lake Erie
41°30'0"N
1,200,000
41°0'0"N
40°30'0"N Pennsylvania Indiana
800,000
40°0'0"N
39°30'0"N 4058 mgal mgal
400,000 39°0'0"N
® West Virginia 38°30'0"N 025507510012.5 -37-40 mgal mgal 38°30'0"N Kentucky Kilometers
20000085°0'0"W1,200,000X(m) 16000001,600,000 20000002,000,000 24000002,400,000
Figure 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 85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W Observed81°0'0"W 80°30'0"W - HMI
42°0'0"N Michigan Lake Erie
41°30'0"N
1,200,000
41°0'0"N
40°30'0"N Pennsylvania Indiana
800,000
40°0'0"N
39°30'0"N 2176 nT
400,000 39°0'0"N
® West Virginia 38°30'0"N 025507510012.5 38°30'0"N Kentucky Kilometers -1333 nT
20000085°0'0"W1,200,000X(m) 16000001,600,000 20000002,000,000 24000002,400,000
Figure 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 85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W Observed81°0'0"W 80°30'0"W - Gxz
42°0'0"N Michigan Lake Erie
41°30'0"N
1,200,000
41°0'0"N
40°30'0"N Pennsylvania Indiana 800,000
40°0'0"N
39°30'0"N
40 mgal
400,000 39°0'0"N ® West Virginia 38°30'0"N 025507510012.5 Kentucky Kilometers -40 mgal
2000001,200,000X(m) 16000001,600,000 20000002,000,000 24000002,400,000
Figure 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
85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"WObserved81°0'0"W 80°30'0"W- TMI_dz
42°0'0"N Michigan
41°30'0"N
1,200,000
41°0'0"N
40°30'0"N Pennsylvania Indiana
800,000
40°0'0"N
39°30'0"N 2176 nT
400,000 39°0'0"N ® West Virginia 38°30'0"N 38°30'0"N 025507510012.5 Kentucky Kilometers -1333 nT
20000085°0'0"W1,200,000X(m) 16000001,600,000 20000002,000,000 24000002,400,000
Figure 18: Difference between calculated and measured magnetic field over the study area in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems.
39 85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W Observed81°0'0"W 80°30'0"W - Gyz
42°0'0"N Michigan Lake Erie
41°30'0"N
1,200,000
41°0'0"N
40°30'0"N Pennsylvania Indiana 800,000
40°0'0"N
39°30'0"N
40 mgal
400,000 39°0'0"N ® West Virginia 38°30'0"N 025507510012.5 Kentucky Kilometers -40 mgal
2000001,200,000X(m) 16000001,600,000 20000002,000,000 24000002,400,000
Figure 19: Difference between calculated and measured Bouguer gravity field over the study area in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems.
40 CHAPTER IV
DATA DESCRIPTION
Nine east-west statewide magnetic and gravity profiles were modeled for the study area (Figures 20-28 and Tables 5-13). In these figures, red lines represent the calculated magnetic and gravity fields from these models. Actual observations from the original data are represented by blue lines. The following results are presented geographically from north to south (Figures 9 and 10: lines labeled A-I) with each profile described from west to east. Descriptions of magnetic and density properties of various polygons embedded in the crust are reported as positive or negative contrasts relative to a magnetically and gravitationally homogeneous crust.
Gravity and magnetic data for the northern-most profile (profile A) were well modeled by a series of shallow bodies overlying two deeper bodies of varying properties
(Figure 20 and Table 5). On the west end of profile A, data were modeled in the shallow crust by five approximately 10 km thick polygons (Bodies 4, 13, 3, 5 and 11) of negative relative density and positive magnetic susceptibility contrasts. Shallow bodies produce the irregular positive magnetic anomalies of (~200 to 300 nT) observed in the data. A 35 km deep and 5 km thick positive magnetic contrast and high density material (polygon
12) was required to model the low frequency components in both sets of data. Farther east, shallow (2-10 km deep) and mid-crustal (10-30 km deep) negative magnetic and
41
1200.0 TMI (nT)
600.0
0.0
-600.0 T MI (nT) -1200.0
X 1500000 2000000 2500000
60.0 Gz (mgal)
40.0
20.0
0.0
-2 0 .0
-4 0 .0 z (m g a l) -6 0 .0
X 1 500000 2 000000 2 500000 4 13 6 17 2 7 8 9 10 14 0 3 5 11 23 1 29 19 22 33 30 Z(m) 12 26
-12500050 km Az = 90.0deg
0
50 km West-dipping Coshocton zone Anorthosite Sediment ary rocks East-dipping Grenville Mafic intrusion Upper Mantle Mafic or ultramafic intrusion Unaltered Ultramafic Felsic igneous rocks
Figure 20: East-West cross-section models for profile A, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line).
42 Table 5 : Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile A. Position (NAD 27) Depth to- Depth Δρ Expected Expected Strike Dip Plunge Δκ (SI) Top (km) Extent (km) 3 XY (g/cm ) ρ (g/cm3) κ (SI) 2540000 810000 -7.2 30.0 -180 40 0 0.00 0.0540 2.77 0.0563 1860000 810000 -2.0 20.0 0 30 0 -0.01 0.0450 2.77 0.0513 1400000 840000 -4.0 4.0 0 0 0 -0.03 0.0330 2.75 0.0393 1310000 839882 -0.5 8.0 0 0 0 -0.03 0.0000 2.75 0.0063 1440000 810000 -4.0 4.0 0 0 0 -0.02 0.0020 2.76 0.0083 1735000 839882 -1.0 20.0 0 -11 0 0.00 0.0330 2.78 0.0393 1885641 810000 -2.2 20.0 0 30 0 -0.01 0.0520 2.89 0.1149 1932938 810000 -2.0 20.0 0 30 0 -0.01 0.0530 2.77 0.0593 1990000 810000 -2.0 20.0 0 30 0 -0.01 0.0540 2.77 0.0603 2045000 810000 -2.0 20.0 0 30 0 0.00 0.0520 2.73 0.0583 1470000 880000 -4.0 4.0 0 0 0 -0.02 0.0290 2.76 0.0353 43 1630000 830000 -36.0 5.2 -180 0 0 0.20 0.0000 3.10 0.0629 1460000 810000 -0.5 3.6 0 0 0 -0.01 0.0000 2.77 0.0063 1810000 810000 -2.0 20.0 0 30 0 0.00 0.0410 2.78 0.0473 2075969 830000 -3.7 6.0 0 0 180 0.00 0.0600 2.78 0.0663 2208000 810000 -3.7 6.0 180 0 180 0.00 0.0570 2.73 0.0633 1616452 1048024 -3.7 8.0 0 0 0 -0.01 -0.0250 2.72 0.0379 2170000 1030000 -36.0 12.0 -90 0 0 0.12 0.0100 3.02 0.0729 1643894 810000 -12.5 16.0 -106 0 0 -0.05 -0.0090 2.85 0.0539 2450000 810000 -10.0 20.0 0 0 180 0.00 0.0350 2.78 0.0413 2240000 839882 -8.0 8.0 -180 40 180 0.00 0.0350 2.73 0.0413 density contrast materials (bodies 23 and 29) were required to model the lower magnetic and gravitational fields found there.
The central portion of profile A required a series of shallow, higher positive magnetic and higher density geologic field sources to model the data. Bodies 17, 2, 7, 8,
9 and 10 appeared to simulate an east dipping geologic source of positive susceptibility, 1 to 3 km deep, and 20 to 25 km thick. They presented a large positive magnetic anomaly
(~ 600 nT) with very small density contrasts (0.01 g/cm3) having very little effect on the gravity model. No deeper-seated materials were required to model the data in this portion of profile A.
The eastern end of profile A required shallow, intermediate and deep crustal bodies of varying geometries to model the data. High frequency magnetic signals in the data were modeled using several small, shallow polygons of high positive magnetic susceptibility contrast (Bodies 19, 22 and 33). Very high density material, deeply seated in the crust (body 26), which underlays bodies 19 and 22, was required to model the positive gravity anomaly found there. However, to better model the data, body 26 had to be located to the north of profile A beneath anomaly (III) northeastern Ohio (Figure 29 and 30) rather than directly beneath profile A. Farther east, a shallow, 4 km thick, negative density and low magnetic susceptibility contrast was required to model a negative gravity anomaly that decreased to the east. Bodies 30 and 1 appeared to simulate a west dipping (35o to 40o), 10 km deep, 30 km thick and positive magnetic susceptibility contrast feature. This feature presented high frequency, positive magnetic anomalies in the east end of profile A.
44
Gravity and magnetic data for profile B were well modeled by series of shallow, intermediate and deep bodies of varying magnetic and gravity properties (Figure 21 and
Table 6). On the west end of profile B, data were modeled in the shallow crust by four approximately 9 km thick polygons (Bodies 7, 17, 25 and 31) of negative density with low magnetic susceptibility in bodies 7 and 17, and relatively high magnetic susceptibility contrast in bodies 25 and 31. Farther to the east, a 10 km thick polygon
(Body 8) of negative density and negative magnetic susceptibility contrast was required to model the data. These shallow bodies produced a positive magnetic anomaly to the west and a negative magnetic anomaly over polygon 8. A group of three polygons
(Bodies 34, 35, and 20) of 32 km deep and 10 km thick positive density and low positive magnetic susceptibility contrast were required to model the low frequency gravity high in the area. Farther east, shallow (2-3 km deep) positive magnetic susceptibility contrast and very low positive density contrast geologic sources (Bodies 26 and 2) were required to model the data sets. They appeared to simulate an east dipping, high amplitude geologic source in the magnetic data and that displayed a lower amplitude signal in the gravity data set.
In the central portion of profile B, a shallow (6 km deep) positive density and negative magnetic susceptibility contrast polygon (Body 19) underlain by an intermediate
(20 km deep) structure (Body 23) of negative density and positive magnetic susceptibility contrast was required to produce non-correlating negative magnetic and gravity anomalies. Farther to the east, bodies 24 and 27 appeared to simulate an east dipping geologic source of positive magnetic susceptibility contrast, 3 to 4 km deep, and ~20 km thick. A 35 km deep and 10 km thick positive magnetic and high positive density contrast
45
1200.0 TMI (nT)
600.0
0.0
-600.0 T MI (nT) -1200.0
X 1500000 2000000 2500000 60.0 Gz (mgal) 40.0
20.0
0.0
-20.0
-40.0 z (mgal) -60.0
X 1500000 2000000 2500000 30 1 3 4 5 9 10 11 13 14 15 16 0 7 25 17 31 68 26 2 24 3327 30 1 3 4 5 9 10 11 12 13 14 15 16 18 19 21
23 33 27 Z(m) 34 20 32 35 Az = 90.0deg -12500050 km 0
50 km West-dipping Coshocton zone Anorthosite Sediment ary rocks East-dipping Grenville Mafic intrusion Upper Mantle Mafic or ultramafic intrusion Unaltered Ultramafic Felsic igneous rocks
Figure 21: East-West cross-section models for profile B, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line).
46 Table 6 : Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile B. Position (NAD 27) Depth to- Depth Expected Expected Body ID Strike Dip Plunge Δρ (g/cm3) Δκ (SI) XYTop (km) Extent (km) ρ (g/cm3) κ (SI) 1 2166000 800051 0.0 1.6 0 0 0 -0.02 0.0000 2.76 0.0063 2 1770000 799563 -2.5 8.0 0 10 0 0.00 0.0440 2.78 0.0503 3 2195000 800051 0.0 2.0 0 0 0 -0.02 0.0000 2.76 0.0063 4 2224000 800051 0.0 2.2 0 0 0 -0.02 0.0000 2.76 0.0063 5 2253000 800051 0.0 2.3 0 0 0 -0.02 0.0000 2.76 0.0063 6 1557576 800051 -0.5 4.0 0 3 0 0.00 0.0260 2.78 0.0323 7 1290000 800051 0.0 8.0 0 0 0 -0.05 0.0000 2.73 0.0063 8 1555000 800051 -0.5 8.0 0 0 0 -0.10 -0.0100 2.68 -0.0038 9 2282000 800051 0.0 2.5 0 0 0 -0.02 0.0000 2.76 0.0063 10 2311000 800051 0.0 2.6 0 0 0 -0.02 0.0000 2.76 0.0063 11 2340000 800051 0.0 2.8 0 0 0 -0.02 0.0000 2.76 0.0063 12 2368000 800051 0.0 3.0 0 0 0 -0.02 0.0000 2.76 0.0063 13 2397000 800051 0.0 3.1 0 0 0 -0.03 0.0000 2.75 0.0063
47 14 2426000 800051 0.0 4.8 0 0 0 -0.03 0.0000 2.75 0.0063 15 2455000 800051 0.0 4.8 0 0 0 -0.03 0.0000 2.75 0.0063 16 2484000 800051 0.0 4.8 0 0 0 -0.03 0.0000 2.75 0.0063 17 1390000 810000 0.0 2.0 0 0 0 -0.10 0.0000 2.68 0.0063 18 2513000 800051 0.0 3.4 0 0 0 -0.02 0.0000 2.76 0.0063 19 1920000 860000 -5.2 4.0 0 0 0 0.01 -0.0350 2.79 -0.0288 20 1661752 800051 -32.0 12.0 0 0 0 0.10 0.0980 3.00 0.3872 21 2580000 801127 -8.0 20.0 0 140 0 0.00 0.0460 2.78 0.0413 23 1960000 800000 -21.2 8.0 0 8 0 -0.08 0.0750 2.70 0.0813 24 2040000 750000 -2.5 20.0 0 19 0 0.00 0.0440 2.78 0.0503 25 1368000 800051 -2.0 16.0 0 0 0 -0.05 0.0260 2.73 0.0323 26 1680000 799563 -2.1 8.0 0 9 0 -0.08 0.0500 2.70 0.0563 27 2100000 800000 -4.0 20.0 0 19 0 0.00 0.0440 2.78 0.0503 30 2136646 799563 0.0 1.5 0 0 0 -0.02 0.0000 2.76 0.0063 31 1410000 800051 -2.0 16.0 0 0 0 -0.05 0.0260 2.73 0.0323 32 2170000 1030000 -32.0 12.0 -90 0 0 0.25 0.0100 3.15 0.2992 33 2090000 800051 -2.0 4.0 0 0 0 0.02 -0.0490 2.80 -0.0428 34 1367246 810000 -32.0 12.0 0 0 0 0.20 0.0030 3.10 0.2922 35 1613400 810000 -42.0 10.0 0 -180 0 0.21 0.0030 3.11 0.2922 was required to model the low frequency, positive gravity anomaly found there.
However, this source was the same source in profile A (Body 26), which was located to the north of profiles A and B beneath anomaly (III) in Figure 30.
The east end of profile B required shallow negative density and very low positive magnetic susceptibility contrast polygons (Bodies 30, 1, 3, 4, 5, 9, 10, 11, 13, 13, 14, 15,
16 and 18) to model the decreasing gravity anomaly to the east. Body 21 appeared to simulate a west dipping (35o to 40o), 10 km deep, 30 km thick and positive magnetic susceptibility contrast source that modeled the high frequency, positive magnetic anomaly.
The gravity and magnetic data for the third profile from north (Profile C) were also well modeled by shallow and deep bodies with presence of a large body in the mid- crustal depth (Figure 22 and Table 7). On the west end of profile C, data were modeled in shallow crust by four 5-10 km thick polygons (Bodies 27, 29, 21, 31 and 23) of negative density and variable magnetic susceptibility contrasts. Shallow bodies produced an inversely correlative positive magnetic anomaly and negative gravity anomaly. A body of high relative density materials, 15 to 20 km thick, located 30 to 35 km deep (Polygons
22, 24 and 26) was required to model the low frequency component in both sets of data.
The central portion of profile C required shallow depth, positive magnetic susceptibility and positive density contrast polygons (Bodies 19, 20, 25 and 8) and mid- crustal depth, high negative magnetic susceptibility and negative density contrast polygons (Bodies 6 and 2) to model the data. The shallow polygons produced directly correlative, high frequency positive magnetic and gravity anomalies. The large mid-
48
TMI (nT) 1200.0
600.0
0.0
-600.0 MI (nT) -1200.0
X 1 500000 2 000000 2 500000
60.0 Gz (mgal)
40.0
20.0
0.0
-20.0
-40.0 (m gal) -60.0
X 1500000 2000000 2500000
27 29 30 1 303 41 53 94 10 5 119 10 12 11 1312 13 14 14 1515 16 16 18 0 21 31 20 25 28 6 19 25 8 17 7 23 24 2 Z(m)
22 26 -12500050 km Az = 90.0deg
0
50 km West-dipping Coshocton zone Anorthosite Sediment ary rocks East-dipping Grenville Mafic intrusion Upper Mantle Mafic or ultramafic intrusion Unaltered Ultramafic Felsic igneous rocks
Figure 22: East-West cross-section models for profile C, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line).
49 Table 7: Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile C. Position (NAD 27) Depth to- Depth Expected Expected Body ID Strike Dip Plunge Δρ (g/cm3) Δκ (SI) XYTop (km) Extent (km) ρ (g/cm3) κ (SI) 1 2166000 700000 0.0 1.6 0 0 0 -0.02 0.0000 2.76 0.0063 2 1991998 466231 -22.8 16.0 -87 0 -8 -0.03 -0.0690 2.70 -0.0062 3 2195000 700000 0.0 2.0 0 0 0 -0.02 0.0000 2.76 0.0063 4 2224000 700000 0.0 2.2 0 0 0 -0.02 0.0000 2.76 0.0063 5 2253000 700000 0.0 2.3 0 0 0 -0.02 0.0000 2.76 0.0063 6 1863606 700000 -7.2 7.2 -90 0 -7 -0.03 -0.0690 2.75 -0.0628 7 2596778 717626 -7.8 30.0 0 145 0 0.00 0.0450 2.78 0.0413 8 2150000 657389 -8.9 12.0 0 0 0 0.02 0.0300 2.80 0.0363 9 2282000 700000 0.0 2.5 0 0 0 -0.02 0.0000 2.76 0.0063 10 2311000 700000 0.0 2.6 0 0 0 -0.02 0.0000 2.76 0.0063 11 2340000 700000 0.0 2.8 0 0 0 -0.02 0.0000 2.76 0.0063 12 2368000 700000 0.0 3.0 0 0 0 -0.02 0.0000 2.76 0.0063 13 2397000 700000 0.0 3.1 0 0 0 -0.02 0.0000 2.76 0.0063 50 14 2426000 700000 0.0 3.4 0 0 0 -0.02 0.0000 2.76 0.0063 15 2455000 700000 0.0 3.8 0 0 0 -0.02 0.0000 2.76 0.0063 16 2484000 700000 0.0 3.8 0 0 0 -0.02 0.0000 2.76 0.0063 17 2518164 717626 -7.1 30.0 0 145 0 0.00 0.0450 2.77 0.0463 18 2513000 700000 0.0 4.0 0 0 0 -0.02 0.0000 2.76 0.0063 19 1960754 700000 -6.5 10.0 0 0 0 0.03 0.0340 2.81 0.0403 20 2050000 810000 -2.0 12.0 0 0 0 0.01 0.0280 2.79 0.0343 21 1420000 840000 -2.0 8.0 0 0 0 -0.08 -0.0340 2.70 -0.0278 22 1600000 810000 -32.0 16.0 180 0 180 0.17 0.0070 3.47 0.0070 23 1560000 717626 -16.0 12.0 180 0 180 -0.02 0.0340 2.71 0.0969 24 1760000 720000 -20.0 12.0 0 0 0 0.18 0.0260 2.91 0.0889 25 2119000 800051 -4.0 4.8 0 0 0 0.02 0.0120 2.80 0.0183 26 1649587 739228 -32.0 16.0 0 0 180 0.25 -0.0430 3.55 -0.0430 27 1300000 730000 0.0 8.0 0 0 0 -0.03 0.0000 2.75 0.0063 28 1790000 717626 -8.0 24.0 0 0 0 0.00 -0.0610 2.78 -0.0548 29 1394235 730000 -0.2 4.0 0 0 0 -0.07 0.0000 2.71 0.0063 30 2137000 720000 0.0 0.8 0 0 0 -0.02 0.0000 2.76 0.0063 31 1810000 840000 -2.0 8.0 180 0 0 -0.08 -0.0340 2.70 -0.0278 crustal depth polygons used in this model also produced directly correlative, low frequency negative magnetic and gravity anomalies.
The eastern end of profile C required a series of shallow depth, low magnetic susceptibility contrast and negative density contrast polygons (Bodies 30, 1, 3, 4, 5, 9, 10,
11, 12, 13, 14, 15, 16 and 18). These polygons appeared to simulate a geologic structure that increased in thickness to the east and produced a decrease in the gravity anomaly to the east. The positive magnetic anomaly on the far eastern end of profile C required west dipping, 10 km deep and positive magnetic susceptibility contrast polygons (Body 17 and
7) to model the data.
Gravity and magnetic data for profile D were modeled by a series of shallow, intermediate and deep polygons (Figure 23 and Table 8). On the west end, the data were well modeled by two 8 km thick shallow polygons (Bodies 16 and 12) of low positive magnetic susceptibility and negative density contrasts and a 32 km deep polygon (Body
14) of high density contrast. Shallow bodies modeled high frequency components in the gravity data while the deeper body modeled the low frequency, positive gravity anomaly found there. Farther to east, a shallow polygon (Body 1) of high magnetic susceptibility and low negative density contrasts was modeled to overlay 30 and 34 km deep polygons
(Bodies 3 and 33) of high density and low positive magnetic susceptibility contrasts.
These polygons produced the non-correlative positive magnetic and gravity anomalies in the area.
The central portion of profile D required a mid-crustal depth, east dipping (~8o), high negative magnetic susceptibility and negative density contrast geologic source to
51
TMI (nT) 1200.0
600.0
0.0
-600.0 T MI (nT) -1200.0
X 1500000 2000000 2500000 60.0 Gz (mgal) 40.0
20.0
0.0
-20.0
-40.0 z (m g a l) -60.0
X 1500000 2000000 2500000
16 5 4 8 7 15 0 121 31 39 10 19 17 11 18 2 33 (m) 14 3
50 km00 Az = 90.0deg
0
50 km West-dipping Coshocton zone Anorthosite Sediment ary rocks East-dipping Grenville Mafic intrusion Upper Mantle Mafic or ultramafic intrusion Unaltered Ultramafic Felsic igneous rocks
Figure 23: East-West cross-section models for profile D, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line).
52 Table 8: Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile D.
Position (NAD 27) Depth to- Depth 3 Expected Expected Body ID Strike Dip Plunge Δρ (g/cm ) Δκ (SI) XYTop (km) Extent (km) ρ (g/cm3) κ (SI) 1 1660000 636932 -2.0 12.0 0 20 180 -0.01 0.0310 2.77 0.0373 2 1960000 640098 -16.0 12.0 -87 0 -8 -0.03 -0.0690 2.70 -0.0062 3 1727895 638873 -29.8 10.0 0 0 0 0.10 0.0000 3.00 0.0629 4 2231769 640098 0.0 4.0 -0.4 0 0 -0.01 0.0000 2.77 0.0063 5 2189441 640098 0.0 1.6 0 0 0 -0.01 0.0000 2.77 0.0063 7 2326876 640098 0.0 3.6 0 0 0 -0.02 0.0000 2.76 0.0063 8 2272904 640098 0.0 6.4 0 0 0 -0.01 0.0000 2.77 0.0063 10 1906541 640098 -6.9 6.0 -90 0 -8 -0.04 -0.0690 2.74 -0.0628 11 2390000 640098 -9.2 8.0 0 0 0 0.01 -0.0630 2.79 -0.0568 12 1650000 520000 -2.0 8.0 0 0 0 -0.05 0.0010 2.73 0.0073 14 1534666 780000 -32.0 8.0 0 0 0 0.18 -0.0060 3.08 0.0569 15 2406671 620000 0.0 4.0 0 0 0 -0.01 0.0100 2.77 0.0163 53 16 1480000 724507 0.0 8.0 0 0 0 -0.05 0.0070 2.73 0.0133 17 2280000 638873 -8.0 30.0 0 145 0 0.00 0.0450 2.75 0.0460 18 2530000 638873 -8.0 30.0 0 145 0 0.00 0.0450 2.75 0.0460 19 1956123 623929 -7.2 8.0 -90 0 -8 0.03 0.0690 2.81 0.0753 31 1848208 620000 -5.3 4.0 -90 0 -8 -0.03 -0.0690 2.75 -0.0628 33 1770000 640098 -24.0 16.0 0 0 0 0.20 0.0100 3.10 0.0729 39 2115602 620000 -4.0 12.0 0 0 0 0.03 -0.0200 2.81 -0.0138 model the data (Bodies 31, 10, 19 and 2). This source produced the directly correlative negative magnetic and gravity anomalies in the area.
The east end of profile D was modeled by a series of shallow and mid-crustal bodies. Shallow polygons (Bodies 5, 4, 8, 7 and 15) simulated a negative density and low magnetic susceptibility contrast source producing the negative gravity anomaly that decreased to east. Bodies 17 and 18 appeared to simulate a west dipping, 10 km deep, 30 km thick and positive magnetic susceptibility contrast source. This source created the high frequency, positive magnetic anomalies in eastern profile D. The negative magnetic anomaly in this portion was modeled by a 12 km deep and 8 km thick, negative magnetic susceptibility contrast polygon (Body 11).
The gravity and magnetic data for the fifth profile (Profile E) were modeled by a series of shallow, intermediate and deep polygons that produced high frequency magnetic and low frequency gravity anomalies (Figure 24 and Table 9). On west end, the data were modeled by two shallow polygons (Body 25 and 14) of contrasting magnetic susceptibility and density. Body 25 simulated a geologic source of positive density and magnetic susceptibility contrast producing co-located positive magnetic and gravity anomalies. Body 14 simulated a geologic source of negative density and magnetic susceptibility contrast producing spatially correlated, negative magnetic and gravity anomalies. Farther to east, the model required shallow and deep polygons to fit the data.
Shallow polygons (Body 23, 15, 16 and 3) appeared to simulate an east dipping, 2-3 km deep and ~15 km deep feature of high positive magnetic susceptibility contrast. This feature produced high frequency positive magnetic anomalies that appear in the area. The
32 km deep, 15 km thick and high positive density contrast polygon (Body 13) simulated
54
TMI (nT) 1200
600
0
-600 T MI (nT) -1200
X 1500000 2000000 2500000
60.0 Gz (mgal)
40.0
20.0
0.0
-20.0
-40.0 z (m g a l) -60.0
X 1500000 2000000 2500000 0 25 14 23 15 16 3 7 8 9 10 11 24 20 1 19 17 12 5 2 4 (m) 13
500 km00 Az = 90.0deg
0
50 km West-dipping Coshocton zone Anorthosite Sediment ary rocks East-dipping Grenville Mafic intrusion Upper Mantle Mafic or ultramafic intrusion Unaltered Ultramafic Felsic igneous rocks
Figure 24: East-West cross-section models for profile E, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line).
55 Table 9: Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile E. Position (NAD 27) Depth to- Depth Δρ Expected Expected Body ID Strike Dip Plunge Δκ (SI) XYTop (km) Extent (km) (g/cm3) ρ (g/cm3) κ (SI) 1 1942882 520000 -7.0 8.0 -90 0 -8 0.04 0.0600 2.82 0.0663 2 1960000 562254 -16.0 12.0 -87 0 -8 -0.03 -0.0690 2.70 -0.0062 3 1750000 557746 -2.0 4.0 0 15 180 0.00 0.0370 2.78 0.0433 4 2048451 623929 -20.8 1.6 0 10 0 -0.02 -0.0690 2.88 -0.0062 5 2380207 557746 -8.2 8.0 0 0 0 0.00 -0.0370 2.78 0.0300 7 2020000 557746 -0.8 16.0 -90 0 -8 0.00 0.0100 2.78 0.0163 8 2080000 557746 -3.8 4.0 0 0 0 0.03 0.0000 2.81 0.0063 9 2180000 557746 0.0 2.2 0 0 0 -0.01 0.0000 2.77 0.0063 10 2220000 557746 0.0 4.0 0 0 0 -0.03 0.0000 2.75 0.0063 11 2277000 557746 0.0 4.0 0 0 0 -0.03 0.0000 2.75 0.0063 12 2310000 557746 -8.0 30.0 0 145 0 0.00 0.0350 2.78 -0.0288
56 13 1739810 557746 -28.9 16.0 0 0 0 0.20 -0.0220 3.10 0.0409 14 1500000 557746 -0.3 24.0 180 0 0 -0.01 -0.0050 2.77 0.0013 15 1595000 557746 -1.6 4.0 0 4 0 0.01 0.0570 2.79 0.0633 16 1684336 557746 -1.3 4.0 0 3 0 0.00 0.0700 2.78 0.0763 17 2220000 557746 -8.0 30.0 0 145 0 0.00 0.0370 2.77 0.0433 19 1988090 557746 -9.2 8.0 -90 0 -8 -0.02 -0.0690 2.76 -0.0628 20 1879319 632212 -7.4 4.0 -90 0 -8 -0.03 -0.0690 2.75 -0.0628 23 1516000 557746 -1.2 4.0 0 15 0 0.04 0.0320 2.82 0.0383 24 2410000 623929 0.0 4.0 0 0 0 -0.02 0.0000 2.76 0.0063 25 1393094 530000 -3.6 20.0 -90 0 0 0.03 0.0170 2.81 0.0233 a high density geologic source producing the low frequency, positive gravity anomaly there.
The central portion of profile E displayed spatially correlated, high frequency positive magnetic and gravity anomalies superimposed upon low frequency negative magnetic and gravity anomalies (Area between 1,800,000 and 2,100,000). The high frequency positive anomalies required a shallow (~ 6 km deep) polygon of positive density and magnetic susceptibility contrast (Body 1). The low frequency, negative anomalies required mid-crustal depth, east dipping (~8o), 15-20 km thick, negative density and magnetic susceptibility contrast polygons (Bodies 20, 19, 2 and 4).
On eastern end of profile E, data were well modeled by a series of shallow bodies overlaying two deeper bodies of varying properties. Bodies 9, 10, 11 and 24 simulated a
2-3.5 km thick, negative density and low magnetic susceptibility contrast geologic source producing a negative gravity anomaly that decreased to east. Bodies 17 and 12 simulated a west dipping, positive magnetic susceptibility and lower density contrast geologic source. No deeper-seated sources were required to model the data in this portion.
Gravity and magnetic data for profile F were modeled by a series of shallow, intermediate and deep polygons (Figure 25 and Table 10). On the west end, the model required more complex properties and geometries to fit the data. The directly correlated positive magnetic and gravity anomalies were modeled by a shallow (4 km deep), 15 km thick, positive contrast magnetic susceptibility and density polygon (Body 23). Farther east, a shallow polygon of positive magnetic susceptibility and negative density contrast
(Body 14) overlays a deeper (10 km deep) body of negative magnetic susceptibility and density contrast (Body 8). The shallow body produced the low amplitude, positive
57
TMI (nT) 1200.0
600.0
0.0
-6 0 0 .0 T MI (nT) -1200.0
X 1500000 2000000 60.0 Gz (mgal) 40.0
20.0
0.0
-2 0 .0
-4 0 .0 z (m g a l) -6 0 .0
X 1500000 2000000
0 12 13 11 18 21 22 10 23 5 4 6 14 8 1 9 2 (m) 3 16 17
50 km000 Az = 90.0deg
0
50 km
West-dipping Coshocton zone Anorthosite Sediment ary rocks East-dipping Grenville Mafic intrusion Upper Mantle Mafic or ultramafic intrusion Unaltered Ultramafic Felsic igneous rocks
Figure 25: East-West cross-section models for profile F, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line).
58 Table 10: Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile F. Position (NAD 27) Depth to- Depth Expected Expected Body ID Strike Dip Plunge Δρ (g/cm3) Δκ (SI) XYTop (km) Extent (km) ρ (g/cm3) κ (SI) 1 1978374 512958 -10.9 4.8 -87 0 -8 -0.03 -0.0600 2.75 -0.0538 2 1960000 341408 -16.0 16.0 -87 0 -8 -0.01 -0.0590 2.72 0.0038 3 1695620 478872 -32.0 4.0 0 0 0 0.20 -0.0220 3.10 0.0409 4 1845284 512958 -5.6 3.2 -87 0 -8 -0.05 0.0000 2.73 0.0063 5 1700000 512958 -6.0 12.0 0 0 0 0.00 -0.0420 2.78 -0.0358 6 2160000 478872 -8.0 30.0 0 145 0 0.00 0.0330 2.77 0.0450 8 1510000 520000 -10.0 8.0 0 0 0 -0.03 -0.0070 2.75 -0.0008 9 2380000 478872 -8.0 25.0 0 145 0 0.00 0.0400 2.78 0.0470 10 2330000 512676 0.0 4.0 0 0 0 -0.04 0.0000 2.74 0.0063 11 1984681 512676 0.0 2.4 0 0 0 -0.03 0.0000 2.75 0.0063 12 1580000 478872 -1.6 4.0 0 28 0 0.00 0.0650 2.78 0.0713 13 1610000 530000 -1.6 4.0 0 5 0 0.00 0.0650 2.78 0.0713
59 14 1485000 440000 -4.0 6.0 0 0 -180 -0.02 0.0250 2.76 0.0313 16 1711993 380000 -36.0 4.0 0 0 0 0.20 0.0000 3.10 0.0629 17 2012394 512676 -36.3 12.0 0 7 0 0.06 0.0000 2.96 0.0629 18 2110000 512958 0.0 2.8 0 0 0 -0.05 -0.0070 2.73 -0.0008 21 2190000 512958 0.0 4.0 0 0 0 -0.05 -0.0070 2.73 -0.0008 22 2260000 520000 0.0 6.0 0 0 0 -0.05 -0.0070 2.73 -0.0008 23 1385000 530000 -3.6 20.0 -90 0 0 0.03 0.0170 2.81 0.0233 magnetic anomaly, yet contributed with body 8 in producing the negative gravity
anomaly that appeared in the area. Farther to east, the high frequency, positive magnetic
anomalies in the data required shallow, east dipping and positive magnetic susceptibility
polygons (Bodies 12 and 13) to simulate the data.
The central portion of this profile displayed a non-correlative medium frequency,
negative magnetic anomaly and a low frequency, positive gravity anomaly. The negative
magnetic anomaly required a shallow (5 km deep), 12 km thick polygon of positive
magnetic susceptibility (Body 5). The positive gravity anomaly required deep (~32 km
deep), 8 km thick source of high positive density contrast (Bodies 3 and 16). Farther east,
directly correlative negative magnetic and gravity anomalies required a large, east
dipping (8o), 15 km thick source of negative magnetic susceptibility and density contrasts
(Bodies 4, 1, and 2) to produce the required signals.
Data in eastern end of profile F were modeled by a series of shallow bodies of
negative density and low positive magnetic susceptibility contrasts that increased in
thickness to the east (Bodies 11, 18, 21, 22 and 10). These geologic sources mimicked the
negative gravity anomaly that decreases to the east. The positive magnetic anomaly in
this portion of the profile required a west dipping source of ~10 km deep, 15-25 km thick
and positive magnetic susceptibility contrast (Body 9 and 6).
Gravity and magnetic anomalies for profile G required multiple source depths and
properties to model the data (Figure 26 and Table 11). On the west end, the model
required thick, shallow sources of negative density and magnetic susceptibility contrast
(Bodies 13 and 15). Such sources produced the required negative gravity (~ -20 mgal)
and magnetic anomalies. Within this area, a medium frequency, positive magnetic
60
TMI (nT) 1200.0
600.0
0.0
-600.0 T MI (nT) -1200.0
X 1500000 2000000 60.0 Gz (mgal)
40.0
20.0
0.0
-20.0
-40.0 z (mgal) -60.0
X 1500000 2000000
13 15 4 16 6 7 0 17 12 18 10 8 1 3 5 2 11 (m) 14 21
50 0km00 Az = 90.0deg
0
50 km West-dipping Coshocton zone Anorthosite Sediment ary rocks East-dipping Grenville Mafic intrusion Upper Mantle Mafic or ultramafic intrusion Unaltered Ultramafic Felsic igneous rocks
Figure 26: East-West cross-section models for profile G, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line).
61 Table 11: Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile G. Position (NAD 27) Depth to- Depth Expected Expected Body ID Strike Dip Plunge Δρ (g/cm3) Δκ (SI) XYTop (km) Extent (km) ρ (g/cm3) κ (SI) 1 1930000 401127 -10.0 6.0 -90 0 -8 -0.02 -0.0690 2.76 -0.0628 2 1960000 360563 -16.0 12.8 -87 0 -8 -0.02 -0.0690 2.71 -0.0062 3 2280000 400000 -8.0 30.0 0 145 0 0.00 0.0470 2.77 0.0480 4 1605000 406197 -1.6 20.0 0.2 90 180 0.00 0.0820 2.78 0.0883 5 1810000 396312 -12.0 20.0 0 59 0 0.00 -0.0150 2.78 -0.0088 6 2140000 405070 0.0 4.8 0 0 0 -0.02 0.0000 2.76 0.0063 7 2240000 405070 0.0 5.2 0 0 0 -0.03 0.0000 2.75 0.0063 8 2190000 406197 -5.6 2.0 0 0 0 -0.05 -0.0010 2.73 0.0053 10 1740000 397603 -2.8 20.0 0 -31 0 0.00 0.0650 2.78 0.0713 11 2077000 405070 -16.0 5.6 0.2 10 0 -0.05 -0.0690 2.68 -0.0062 12 1640510 406197 -2.4 20.0 0 -29 0 0.00 0.0610 2.78 0.0673 13 1390000 406197 0.0 20.0 0 0 0 -0.01 -0.0120 2.77 -0.0058 62 14 1734850 406197 -33.3 8.0 0 0 0 0.20 0.0000 3.10 0.0629 15 1540000 406197 0.0 12.0 0 0 0 -0.02 -0.0100 2.76 -0.0038 16 2060000 405070 -0.7 2.0 0 0 0 -0.02 0.0000 2.76 0.0063 17 1480000 360563 -4.0 12.0 0.2 0 0 0.00 0.0190 2.78 0.0253 18 1670000 406197 -2.9 12.0 0 0 0 0.02 -0.0580 2.80 -0.0518 21 1973947 406197 -31.1 4.0 0 8 0 0.08 -0.0180 2.98 0.0449 anomaly required a shallow (~ 3km deep), 10 km thick and positive magnetic susceptibility source (Body 17).
The central portion of this profile had high frequency, positive and negative magnetic anomalies and a low frequency, positive gravity anomaly. The magnetic anomalies required shallow, east dipping, 20 km thick, both positive and negative magnetic susceptibility contrast polygons (Bodies 4, 12, 18, 10 and 5). A 32 km deep, 10 km thick, high amplitude positive density contrast (Body 14) was required to model the low frequency, gravity anomaly found there.
The eastern part of profile G required shallow and intermediate depth sources to model the data. Large, intermediate depth, 15 km thick, negative density and magnetic susceptibility contrast sources (Bodies 1and 2) were required to model the correlating negative magnetic and gravity anomaly. Farther to east, shallow, 2 to 4 km thick and negative density polygons (Bodies 16, 6, 7 and 8) were required to model the negative gravity found there. Continuing east, the data required a west dipping, 10 km deep, 30 km thick and positive magnetic susceptibility contrast polygon (Body 3) to model the high frequency, positive magnetic anomaly found there.
Gravity and magnetic data along profile H were modeled by a series of shallow, intermediate and deep bodies of varying properties (Figure 27 and Table 12). On western part of this profile, data were modeled by shallow, thick bodies (Bodies 12 and 13) of negative density and magnetic susceptibility contrasts. Those bodies produced the negative magnetic and gravity anomalies found in this region. Farther east, shallow depth, 15 km thick, positive density and magnetic susceptibility contrast polygons
63
TMI (nT) 1200.0
600.0
0.0
-6 0 0 .0 T MI (nT) -1200.0
X 1500000 2000000
60.0 Gz (mgal)
40.0
20.0
0.0
-2 0 .0
-4 0 .0 z (m g a l) -6 0 .0
X 1500000 2000000
0 11 16 24 6 14 15 2319 25 21 22 20 1213 5 18 3 1 2 Z(m) 10 17 8
-12500050 km Az = 90.0deg
0
50 km West-dipping Coshocton zone Anorthosite Sediment ary rocks East-dipping Grenville Mafic intrusion Upper Mantle Mafic or ultramafic intrusion Unaltered Ultramafic Felsic igneous rocks
Figure 27: East-West cross-section models for profile H, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line).
64 Table 12: Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile H. Position (NAD 27) Depth to- Depth Δρ Expected Expected Body ID Strike Dip Plunge Δκ (SI) XYTop (km) Extent (km) (g/cm3) ρ (g/cm3) κ (SI) 1 1941418 520000 -7.8 6.0 -90 0 -8 -0.02 -0.0690 2.76 -0.0628 2 1960000 319437 -16.0 12.0 -87 0 -8 -0.02 -0.0690 2.71 -0.0062 3 1734647 381972 -6.3 12.4 0 0 0 -0.02 -0.0560 2.76 -0.0498 5 1660228 321690 -6.3 12.0 0 0 0 0.03 -0.0690 2.81 -0.0628 6 1740000 320563 -2.0 4.0 0 29 180 0.00 0.0640 2.78 0.0703 8 1780000 310000 -38.0 4.0 0 0 0 0.20 0.0400 3.10 0.1029 10 1761071 252000 -25.1 12.0 0 0 0 0.10 0.0400 3.00 0.1029 11 1568027 321690 -1.5 2.0 0 0 0 0.00 0.0250 2.78 0.0313 12 1540000 319437 -4.0 14.0 0 0 0 -0.02 -0.0070 2.76 -0.0008 13 1550000 320563 -4.0 11.2 0 0 0 0.02 -0.0040 2.80 0.0023 14 1810000 252000 -2.0 4.0 0 29 180 0.00 0.0620 2.78 0.0683 15 1970000 360000 -2.0 6.0 0 0 0 0.03 0.0000 2.81 0.0063 65 16 1641000 279000 -1.6 12.0 0 0 0 0.05 0.0090 2.83 0.0153 17 1940000 317183 -26.7 8.0 0 8 0 0.08 0.0240 2.98 0.0869 18 1695112 319437 -6.3 12.0 0 0 0 -0.02 -0.0540 2.76 -0.0478 19 2028000 319437 0.0 2.2 0 0 0 -0.02 0.0000 2.76 0.0063 20 2197465 320563 0.0 7.6 0 0 0 -0.02 0.0000 2.76 0.0063 21 2091296 268000 0.0 2.4 0 0 0 -0.02 0.0000 2.76 0.0063 22 2152000 279000 0.0 3.2 0 0 0 -0.02 0.0000 2.76 0.0063 23 2010000 252000 -2.0 4.0 0 32 180 0.00 0.0350 2.78 0.0413 24 1660000 252000 -2.0 4.0 0 5 0 0.00 0.0400 2.78 0.0463 25 2040000 252000 -4.0 4.0 0 12 180 0.00 0.0290 2.78 0.0353 (Bodies 16 and 5) were required to model the positive magnetic and gravity anomalies in the area.
The central portion of profile H had high frequency, positive magnetic anomalies and low to medium frequency, positive gravity anomalies. Several 2 km deep, 10 to 15 km thick and positive magnetic susceptibility contrast polygons (Bodies 24, 6 and 14) were required to model the high frequency, positive magnetic anomalies. These overlay
10 km deep and 10 km thick, negative density contrast polygons (Bodies 18 and 3) that were required to model the medium frequency, negative gravity anomaly. Deeply buried in crust (30 km deep), 15 km thick and high positive density contrast sources (Bodies 10 and 8) were required to model the low frequency, positive gravity anomaly found there.
Farther east, co-located negative magnetic and gravity anomalies were modeled at intermediate depth by 20 km thick, negative magnetic susceptibility and density contrast polygons (Bodies 1 and 2).
Data on the eastern end of profile H were well modeled by a series of shallow sources that increased in thickness to east. Bodies 19, 21, 22 and 20 appeared to simulate a negative density contrast, 2 to 4 km thick, geologic source that produced the negative gravity anomaly in the area. These overlay an east dipping, 3 km deep, 5 to 8 km thick and positive magnetic susceptibility contrast geologic source reproducing the high frequency, positive magnetic anomalies in the data.
Gravity and magnetic data for the southern-most profile (Profile I) were well modeled by a series of shallow bodies overlaying two deeper bodies of varying properties
(Figure 28 and Table 13). On west end of profile I, data were modeled in the shallow crust a 20 km thick material (Body 16) of positive density and high positive magnetic
66 susceptibility contrasts. Farther east, the negative magnetic and gravity anomalies required a shallow, 10 km thick polygon (Body 12) of negative density and magnetic susceptibility contrasts.
The central portion of profile I was characterized by high frequency, positive magnetic anomalies and a low frequency, positive gravity anomaly. A series of east dipping, shallow (2 to 4 km deep), 20 km thick and positive magnetic susceptibility contrast polygons (Bodies 3, 1and 2) were required to model the high frequency, positive magnetic anomalies. The low frequency gravity anomaly in this profile was simulated using a deeply buried material of high positive density and magnetic contrasts (Bodies 9 and 17).
The east end of this profile was best modeled by a series of west dipping polygons
(Bodies 6 and 7) that were 10 km deep, 20-30 km thick and positive magnetic susceptibility contrast. These bodies produced the high frequency, positive magnetic anomalies needed to match the data.
67
1200.0 TMI (nT)
600.0
0.0
-600.0 T MI (nT) -1200.0
X 1750000 2000000 60.0 Gz (mgal) 40.0
20.0
0.0
-20.0
-40.0 z (mgal) -60.0
X 1750000 2000000 0 16 12 3 1 2 4 6 7
Z(m) 9 17
550000 km Az = 90.0deg
0
50 km West-dipping Coshocton zone Anorthosite Sediment ary rocks East-dipping Grenville Mafic intrusion Upper Mantle Mafic or ultramafic intrusion Unaltered Ultramafic Felsic igneous rocks
Figure 28: East-West cross-section models for profile I, showing the comparison between observed anomalies (blue line) and calculated anomalies (red line).
68 Table 13: Bodies’ locations, depths, and the expected rocks’ densities and susceptibility for profile I. Position (NAD 27) Depth to- Depth Δρ Expected Expected Body ID Strike Dip Plunge Δκ (SI) XYTop (km) Extent (km) (g/cm3) ρ (g/cm3) κ (SI) 1 1779291 235929 -2.6 20.0 0 28 180 0.00 0.0800 2.78 0.0863 2 1816791 235929 -3.7 20.0 0 28 180 0.00 0.0560 2.78 0.0623 3 1746478 235929 -2.6 20.0 0 28 180 0.00 0.0560 2.78 0.0623 4 1940000 235929 -8.0 20.0 0 145 0 0.00 0.0560 2.78 0.0623 6 2010000 235929 -6.0 30.0 0 145 0 0.00 0.0560 2.78 0.0623 7 2050000 235929 -6.0 30.0 0 145 0 0.00 0.0440 2.78 0.0503 9 1791178 235929 -32.0 4.0 0 0 180 0.15 0.0800 3.05 0.1429 12 1676357 235929 -2.0 8.0 0 0 0 -0.01 -0.0310 2.77 -0.0248 16 1630116 235929 -1.6 16.0 0 0 0 0.02 0.0650 2.80 0.0713 17 1942740 235929 -32.0 4.0 180 0 180 0.15 0.0650 3.05 0.1279 69
85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W 81°0'0"W 80°30'0"W
42°0'0"N Michigan Lake Erie 1400000
41°30'0"N II 1200000 1,200,000
41°0'0"N .I. III 1000000
40°30'0"N Pennsylvania 800000 Indiana 800,000
40°0'0"N IV .V VII 600000
39°30'0"N VI 1600 1400
1200
1000
800 400000 600 400,000 39°0'0"N 400
200
0
-200
-400 200000 ® -600 West Virginia 38°30'0"N -800 025507510012.5 Kentucky -1000nT 1400000Kilometers 1600000 1800000 2000000 2200000 2400000nT
1,200,000 84°0'0"W1,600,000 83°30'0"W 83°0'0"W 2,000,000 2,400,000
Figure 29: Reduced-To-Pole (RTP) magnetic anomaly map of Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates system. Weight dashed lines illustrate main anomalies areas that were used in correlation with gravity map. Contour Interval (CI) = 100 nT
70 85°0'0"W 84°30'0"W 84°0'0"W 83°30'0"W 83°0'0"W 82°30'0"W 82°0'0"W 81°30'0"W 81°0'0"W 80°30'0"W -84.50 -84.00 -83.50 -83.00 -82.50 -82.00 -81.50 -81.00 -80.50
Michigan 42.00 42°0'0"N Lake Erie
41°30'0"N 41.50
II 1,200,000
41°0'0"N .I 41.00 III
40°30'0"N 40.50 Pennsylvania Indiana
800,000
40°0'0"N 40.00
15 VI 10 5 0 39°30'0"N -5 39.50 VII -10 -15 IV -20 -25 -30 mgal -35 400,000 39°0'0"N -40 39.00 -45 -50 -55 -60 -65 ® -70 West Virginia 38°30'0"N 012.5 25 50 75 100 -75 38.5038°30'0"N Kentucky -80 Kilometers V V -85
85°0'0"W1,200,000 1,600,000 2,000,000 2,400,000
Figure 30: Bouguer gravity map of Ohio in Geographic NAD27, and Ohio State Plane NAD27 coordinates systems. Weight dashed lines illustrate main anomalies areas that were used in correlation with gravity map. Contour Interval (CI) = 5 mgal.
71 CHAPTER V
INTERPRETATION
The two dimensional gravity and magnetic models discussed here were interpreted in a fashion consistent with known lithologies for the region. The negative gravity anomalies on the western ends of profiles A, B, C, and D (Figures 20, 21, 22 and 23) are interpreted to be a thick sequence of sedimentary rocks related to the ECRB. As indicated by the modeling and by drill logs, there should be up to 8 km of sediments with densities of ~2.73 g/cm3. However, in these models, the expected ECRB is underlain by the EGRP, which in general causes the negative magnetic anomalies in western Ohio. Importantly, the high gravity anomalies in this area are interpreted to be high-density geologic sources at 30-35 km depth. They are interpreted to be associated to the Fort Wayne Rift System that trends northwest-southeast from northern Indiana.
To the north (in profile A of Figure 20), the low magnetic and gravity anomalies generated by body 29 contribute to the regional gravity and magnetic low (shown in
Figure 29 and 30-anomly I). This body is interpreted to be a portion of a thick granite terrain, which is interpreted to have been separated by the rifting event and overlain by the ECRB.
These data appear to model two major suture zones. The 2-4 km deep and ~15o to
35o east dipping bodies in the western and central portions of the profiles (Figures 20
72 through 28) are interpreted to be associated with the east dipping Grenville province.
However, the far western ends of these bodies create a higher-frequency and larger amplitude signal interpreted to be associated with the Grenville Front Tectonic Zone.
Bodies 26 and 32 in profiles A and B respectively (Figures 20 and 21) are interpreted to be high-density materials that are part of the upper mantle. These are overlain by a thin crust, ~35 km thick, beneath Wayne County northeastern Ohio. The west dipping features that appear in the east portions of profiles A through I are interpreted to be the Coshocton zone. This feature extends from mid- to lower crustal depth at a 35o to 40o westward dip.
The west ends of profile B through H (Figures 21 to 27) are characterized by gravity anomalies that decrease in gravitational intensity to the east. The anomalies are interpreted to be a thick sequence of Phanerozoic sedimentary rocks that increase in thickness (1 to 4 km) to the east of Ohio. These sediments comprise the well-known
Appalachian basin.
On the western ends of profiles B and C (Figure 21 and 22), the positive magnetic and negative gravity anomalies, which were modeled by bodies 25 and 31 in profile B and body 23 in profile C, are interpreted to be intermediate composition extrusive rocks.
In profiles C through H (Figures 22 to 27), the large cylindrical sources that reflect well- correlated negative magnetic and gravity anomalies are interpreted to be the anorthositic pluton, which was first suggested by Lucius and von Frese (1988). It is modeled here as an east dipping (~8o), 10 to 15 km deep terrain 15 to 25 km thick. The western boundary of this pluton is characterized by high magnetic and gravity anomalies. These anomalies are interpreted to be associated with the east dipping Grenville province underlain by the
Fort Wayne Rift materials. The northern boundary of this pluton is characterized by a
73 high magnetic anomaly that is thought to be the east dipping Grenville province. On the western end of profile E and F, in Butler County in southwestern Ohio (Figures 24 and
25), the magnetic and gravity highs (that were modeled by bodies 25 and 23 respectively) are interpreted to be a cylindrical shape mafic batholith ~4 km deep and ~15 km thick within the EGRP.
74
CHAPTER VI
DISCUSSION
Magnetic anomalies are derived from geological sources that exhibit lateral contrasts in magnetization with respect to the area lithology or from structural variations.
Commonly, sedimentary rocks have low magnetization and rocks lose their magnetization property at the Curie point isothermal (500o to 550o). Hence, magnetic anomalies sources in Ohio, in general, reflect magnetic variation of the crystalline basement rocks due to their lithologic and structural variation (Lucius J., 1985; Lucius and von Frese, 1988; von Frese et al., 1997)
The gravity anomaly sources in Ohio modeled here appear to be related to lateral density variations that occur within the sedimentary rock column, crystalline basement rocks, and the mantle (Lucius J., 1985). The Ohio Bouguer gravity anomaly (Figure 30) shows anomalies that attributed to lithological and/or structural variation within Ohio crust and upper mantel that were modeled here.
Forward modeling is inherently imprecise because observed data can be modeled by an infinite set of parameters. Such models are better constrained when both magnetic and gravity data are simultaneously inverted. In the 2D magnetic and gravity modeling discussed here, geologically consistent polygonal and cylindrical bodies were developed to model the data for each profile and to quantitatively represent the geologic source for the magnetic and gravity anomalies. Models’ sizes and depths were controlled by
75 magnetic and gravity amplitude, wavelength, core data, and seismic information.
Magnetic susceptibility and densities values for shallow sources were geologically reasonable and constrained using data from basement penetrating well logs (Appendix
A). The magnetic susceptibility and density contrast for deeper sources that were not penetrated by wells were calculated using average crust and upper mantle susceptibilities and densities (Figure 31).
The expected EGRP and ECRB in western Ohio are characterized by negative and positive susceptibility and negative density contrasts respectively. The susceptibility and density contrast of the ECRB range from 0 to 0.007 SI and -0.1 to –0.01 g/cm3 respectively. The susceptibility and density contrast of the EGRP range from -0.034 to –
0.01 SI and -0.08 to -0.01 g/cm3 respectively. The ECRB and the EGRP contribute to each others gravity anomalies but can be distinguished based on the magnetic parameters.
In general, the ECRB thickness varies from 2 to 8 km thick. The expected rifting in western and south-central Ohio is characterized by deep (28 to 35 km deep) and high positive density contrast sources that range from 0.15 to 0.2 g/cm3. The magnetic susceptibility contrasts of these sources vary based on their depth. They are positive susceptibility contrasts (0.04 to 0.08 SI) in depths less than 30-33 km and lose their susceptibility at depths greater than 33 km deep.
The modeled anorthosite complex south-central Ohio is characterized by negative susceptibility contrast (-0.069 SI), negative density contrast (-0.02 g/cm3), and mid- crustal depth. This 8o east dipping unit appears to be best modeled with varying thickness. Also, the well-known Grenville province in the area is characterized by east dipping (15o to 35o) sources of positive susceptibility contrast (0.035 to 0.55 SI) and very
76
a) SUSCEPTIBILITY DENSITYDENSIT 3 (SI) (g/cm ) 0 0 2.75 – 2.80 0.0050 – 0.0075 10 10
2.70 – 2.75
20 20
0.0503 – 0.0754 th in Kilometers 2.80 – 3.00 p 30 30
De
40 0.0 3.30 40
Gravity b) Minima Intermediate Maxima + + + + + + + + + + ------+ Sedimentary + ------+ + + Rocks + + + - - - Unaltered - - - - Anorthosite Zones Limestone - Ultramafics - - - of Granitization Marble ------Minima + + + Granite + + + ------+ + + Quartzite + + ------+++++++++ ------
Granite (Magnetite rich) Gneiss Amphipolite netic Felsic Extrusive Metavolcanics
g Schist Granodiorite Granulites
Ma Syenite
Intermediate
------+ + + + + + + + + +
------Ultramafic - - - Trachyte - - - - Intrusion Intermediate Diorite + + + + + + + + + + Extrusive Mafic Extrusive Mafic Intrusion
Maxima ------+ + + + + + + + + + ------Norite Floored ------Anorthosite
Figure 31: Standard geologic models for correlation the magnetic and gravity field anomalies of Ohio. a) Generalized crustal susceptibilities and densities in Ohio from Lucius and von Frese, 1988. b) Generalized lithologic correlation models between magnetic and gravity anomalies from von Frese et al., 1997.
77 low density contrast in most cases. The west end of the Grenville province is the
Grenville Front Tectonic Zone, which is characterized by higher magnetic susceptibility
than the western Grenville province. The sedimentary column in eastern Ohio (forming
the Appalachian basin) increases in thickness from 1 km thick central Ohio to ~4 km to
the east. It characterized in the models by negative density contrast (-0.02 to –0.03 g/cm3) and very low magnetic contrast.
Previous studies of this region (including magnetic, gravity, well logs, and seismic) have resulted in structural models and images of the crust and the upper mantle beneath
Ohio. Regionally, the ECRB has been modeled as a feature extending from northwestern
Ohio to central Kentucky, westward across Indiana, and eastward beneath the Grenville
Front Tectonic Zone (Drahovzal et al., 1992; Stark, 1997; Dean and Baranoski, 2002). It is interpreted to be an extension of the middle Proterozoic (Keweenawan) Midcontinent
Rift System (MRS) (Drahovzal et al., 1992; Stark, 1997; Dean and Baranoski, 2002).
Boreholes that penetrate the sediments have been used to suggest that it was deposited during middle Proterozoic time in western Ohio as evidenced by the existence of a lithic arenite sequence referred to as the Middle Run Formation (Shrake, 1991a; Shrake, et al.,
1991b). A total of 582 m of continuous core and a 12.8-km seismic traverse across
Warren County western Ohio showed that the middle Run Formation is part of a sedimentary sequence within the ECRB having a depth of at least 5200 m (Shrake,
1991a; Shrake, et al., 1991b). However, because of the lack of consistency between the
ECRB and the associated basin with the Midcontinent (Keweenawan) Rift System in magnetic and gravity data, the ECRB is also suggested to be deposited after the Grenville orogeny and before the Mount Simon deposition (Richard, et al., 1997).
78
The East Granite Rhyolite Province (EGRP) in western Ohio contains 1480 Ma of
rhyolite to dacitic volcanic rock and chemically similar epizonal plutons that extends
from Ohio to the Texas Panhandle (Bickford et al., 1986; Van Schmus et al., 1996).
Based on the COCORP seismic lines across the midcontinent, the EGRP forms a layered reflector that underlies the Phanerozoic sedimentary rocks of southern Illinois, Indiana, and western Ohio and reaches thicknesses of 11 km (Figure 32) (Pratt et al., 1989;
Hauser, E., 1993; Culotta et al., 1990). Also, Lucius, J., (1985); Lucius and von Frese,
(1988); von Frese et al., (1997) attributed the low-intensity and long-wavelength magnetic and gravity anomalies western Ohio to an extensive granitic terrane (Anomalies
I and IV in figures 29 and 30). Lithology data (Figure 8 and appendix A) illustrate that the western part of Ohio is floored by mostly granite and rhyolite rocks. The low gravity anomaly (Anomaly I in Figure 30, body 29 in profile A), which corresponds a broad area of low magnetic gradients and amplitude, is also interpreted to be an extensive granitic terrain by Lucius, J., (1985). It is not clear if this terrain is related to the felsic central province, which named by the East Granite Rhyolite Province (EGRP) (Figure 32)
(Lucius, J., 1985). However, several later studies of the eastern end of the EGRP suggest overthrusting by the Grenville Front in western Ohio (Figure 32) (Pratt et al., 1989;
Culotta et al., 1990; Hauser, E., 1993; Dean and Baranoski, 2002).
The Fort Wayne Rift Zone that crosses and cuts the ECRB and the EGRP in western and southern Ohio was interpreted by several researchers (Lucius, J.,1985);
Lucius and von Frese, 1988; Drahovzal et al., 1992; von Frese et al., 1997) to be non- magnetic and high-density materials in the lower and middle crust that related to the well- known Midcontinent (Keweenawan) Rift System. Magnetic and gravity models and wells
79
85°0'0"W 84°0'0"W 83°0'0"W 82°0'0"W 81°0'0"W
42°0'0"N Lake Erie Michigan Lake Erie
( Ottawa Lake Ashtabula Fulton Lucas Erie Williams 41°30'0"N Ottawa Geauga ( Cuyahoga Wood Sandusky Erie Defiance Henry Trumbull Lorain 1,200,000 ( Portage Paulding Seneca Huron Medina Summit 41°0'0"N Putnam Hancock Mahoning
( Van Wert Wyandot Crawford Ashland Wayne Stark Allen Richland Columbiana Pennsylvania
Indiana (
Hardin( Auglaize Marion Holmes Carroll
40°30'0"N Mercer Morrow
( COCORP OH1 ( Tuscarawas Logan Knox Jefferson Shelby Union Delaware Coshocton Harrison COCORP OH2 800,000 Darke Champaign( Licking Miami Guernsey Belmont 40°0'0"N (1) Franklin Muskingum 40°0'0"N Clark ( Madison (3) Preble Montgomery Fairfield Perry Noble
(2) Greene Monroe (
( Pickaway Morgan
Fayette ( ( Hocking 39°30'0"N Washington Butler Warren Clinton
Ross Athens ( ( Vinton Hamilton Highland ECRB Meigs
Pike TSC 400,000 ( Clermont( 39°0'0"N Jackson Brown GFTZ ( Adams Scioto Gallia ( West Virginia Seismic line ® CONSORTIUM seismic line (1) Lawrence ARMCO seismic line (2) 012.5 25 50 75 100 (4) 38°30'0"N WRITE STATE seismic line (3) 38°30'0"N Kilometers Kentucky KD seismic lines (4)
1,200,000 1,600,000 2,000,000 2,400,000
Figure 32: General basement provinces (Grenville province and East Granite Rhyolite Province (EGRP), East Continent Rift Basin ECRB), Tri-State Caldera (TSC), and Grenville Front Tectonic Zone (GFTZ).
80 data that were used to locate this feature suggest that gabbroic melt from the mantle could
account for the high-density contrast and be the reason that the magnetic signature is not
clear (Lucius, J., 1985; Lucius and von Frese, 1988). In central and southern Ohio, the rift
zone also is interpreted to be overthrusted by the Grenville province (Dean and
Baranoski, 2002).
The east dipping Grenville province is a well-delineated feature in magnetic and
seismic data and has been extensively studied (Figure 29, anomaly-V). It is composed of
high to medium-grade metamorphic rocks that cause higher-frequency and higher-
amplitude signals in the data than those of the EGRP in western Ohio (Lucius, J., 1985;
Lucius and von Frese, 1988; Culotta et al., 1990; Drahovzal et al., 1992; von Frese et al.,
1997). The transition zone between the two provinces, which is the west end of the
Grenville Province, is named by the Grenville Front Tectonic Zone (GFTZ). It is also a
well-delineated north-south trend of high-amplitude magnetic anomalies (Lucius, J.,
1985; Lucius and von Frese, 1988; Culotta et al., 1990; Drahovzal et al., 1992; von Frese
et al., 1997). East of the GFTZ, Seismic reflection data along the COCORP line OH-1
imaged a 50-km wide, east dipping zone of reflectors, penetrating 25 km depth (Figure
33) (Pratt et al., 1989; Culotta et al., 1990; Hauser, E., 1993). Immediately west of the tectonic zone, an ~14o east-dipping ramp-flat is interpreted to thrust over the EGRP
(Hauser, E., 1993).
The west-dipping Coshocton zone in eastern Ohio is well imaged by the COCORP
OH-2 seismic line. Pratt et al. (1989) interpreted this zone as marking a region of
pervasive ductile deformation in the middle and lower crust of 80 km or more in width
(Figure 33). They also suggested that this zone might mark a major collision zone.
81
However, the west-dipping zone may not sub crop beneath the Phanerozoic sedimentary rocks, rather it could be overlain and truncated by later Grenville northwest-directed thrust at shallow levels (Pratt et al., 1989). Such an interpretation suggests that the crustal fabric developed in response to subduction or subsequent closure during the Grenville event (Pratt et al., 1989).
A later study by Culotta et al. (1990) correlated the west-dipping feature in eastern
Ohio, via geopotential lineaments, with a similarly oriented structure to the northeast and southwest. The Coshocton zone magnetic signature can be traced and correlated with one of the most prominent magnetic anomalies in eastern North America called the New
York-Alabama anomaly (Amish anomaly), which extends from north Alabama through eastern Tennessee to central West Virginia and along central Pennsylvania and eastern
New York (Figure 34) (Culotta et al., 1990). A similar amplitude and frequency magnetic anomaly that extends northward along the Ohio-West Virginia border into western
Pennsylvania can also be attributed to the same feature (Culotta et al., 1990). However, this anomaly marks the east edge of a crustal block with west dipping tectonic fabric that extends across eastern Ohio (Culotta et al., 1990).
The expected sedimentary column in eastern Ohio is part of the Appalachian basin that overlies the Grenville province in western Ohio. A cross section constructed from wells penetrating basement in Indiana, Ohio, and West Virginia shows that the sedimentary rocks in eastern Ohio are up to 4000 m thick (Root and Onasch, 1999). Also, the deep crustal seismic cross section interpreted from COCORP OH-1 and OH-2, showed that the sedimentary column increases from 0.5 s travel time central Ohio up to
~2 s eastern Ohio (Pratt et al., 1989). However, there are few wells that penetrate
82
0 5 20 10 15 West Virginia Ohio E 1000 Appalachian Basin Appalachian MOHO ? 500 COCORP-OH2 W mic lines by Pratt et al.(1989) VP 100VP E 2000 2500 MOHO ? MOHO ? on of COCORP-OH1 and OH-2 seis 1500 GFTZ COCORP-OH1 Figure 33: Possible interpretati Granite-Rhyolite Province Granite-Rhyolite W Province Grenville Granite-Rhyolite ? Granite-Rhyolite Ohio VP 100VP 500 1000
0
5 20 S e c o n d 10 15 s Indiana 83
Grenville Front Tectonic Zone Coshoct on Zone
Figure 34: Ohio and adjacent states magnetic map. Solid white lines: Seismic lines; GF: Grenville Front; CZ: Coshocton Zone; NY-AL: New York- Alabama lineament; AA: Amish Anomaly. Modified from (Committee for the Magnetic Map of North America, 1987; Steigerwalt R., 2002).
84 basement rocks in southeastern Ohio, thus limiting the interpretation. A total of 3500 m of Phanerozoic sediment have been penetrated by well in Noble County in eastern Ohio.
In Columbiana County of northeast of Ohio, ~3000 m of sediments has been confirmed by wells that samples metamorphic rocks of the Grenville province.
The intermediate composition extrusive rocks purported to underlie western Ohio, were interpreted by Lucius and von Frese, (1988) and von Frese et al., (1997) to be a geologic body 2-5 km deep and ~12 km thick. Lucius, J., (1985) suggested this source to be mostly trachyte porphyry based on the exposing of trachyte porphyry rocks in two wells east of the source anomalies in Miami and Shelby Counties (Figure 8).
Anorthosite rocks occur in the Grenville province and can be associated with either a positive or negative magnetic anomalies depending on whether the rocks are floored by mafic rocks or not (Lucius, J., 1985). In Ohio, the expected anorthosite complex appears as negative magnetic and gravity anomalies that extend from central to southern Ohio
(Figures 29 and 30, anomaly-VI). Lucius and von Frese, (1988), von Frese et al., (1997) suggested that this mass is located at upper to middle-level crustal depth. Also, they suggested that it may have formed in the lower crust, but, because of uplift and erosion during the Grenville orogeny, it is now positioned at intermediate depth. However, there is no direct evidence of such a lithology to support this interpretation with the exception of gneiss rocks of high plagioclase content found in two deep wells in Jackson County southern Ohio, and anorthosite rocks in a deep well in Kentucky (Lucius, J., 1985; Lucius and von Frese, 1988). Seismic data southern Ohio (line KD-4) (Figure 32), were used to suggest that this plutonic body is positioned within the crust of Ohio (Steigerwalt, 2002).
It was suggested that this body may have acted as rigid body during a shallow west
85 directed thrust event creating a means for lateral movement along the flanks of the pluton
(Figure 35) (Steigerwalt, 2002).
The interpreted mafic batholith in Butler County was first suggested by Lucius, J.,
(1985) when it was modeled as a 2-4 km-deep and 10-20 km-thick unit by Lucius and von Frese, (1988) and von Frese et al., (1997). Deep wells near this feature that exposed volcanic rocks support this interpretation (Figure 8). However, the occurrence of mafic rocks in western Ohio, in general, may be related to crustal rifting and/or thrusting events
(von Frese et al., 1997).
86
Anorthosite Seismic lines
Figure 35: The expected lateral ramp movement in central Ohio along the flanks of the anorthosite body (Steigerwalt, R., 2002)
87 CHAPTER VII
CONCLUSION
This gravity and magnetic data modeling study resulted in nine east-west cross- sections in southern Ohio that model crust and upper mantle lithology and structure
(Figure 20 through 28). These cross-sections displayed the well-known Grenville province, the east-dipping Grenville Front Tectonic Zone, the west-dipping Coshocton zone, the Phanerozoic sediments cover, the EGRP and variations in crustal thickness beneath southern Ohio.
A large anorthosite pluton was modeled to be positioned in the upper to middle- crust within the Grenville province (Figure 36). The models inferred that the feature has an 8o east dip. Also, this pluton is surrounded by high amplitude magnetic anomalies that were modeled and interpreted to be associated with the east-dipping Grenville Front and the west-dipping Coshocton zone. In addition, the cross-sections provided support for the contention that the Fort Wayne Rift was over thrust by the Grenville Front in central and southern Ohio. The expected mafic rocks that floored the anorthosite body as suggested by Lucius and von Frese (1988) can be modeled and interpreted to be a deep source of materials with a high relative density. These materials could be rift-related material that is associated with the Fort Wayne Rift System. In eastern Ohio, the crust is modeled as having a broad area of west-dipping (35o to 40o) structures that were previously
88 interpreted by Pratt et al. (1989) and Culotta et al. (1990). This zone (the Coshocton zone) was modeled at mid-crust depth extending into to lower crustal depth (Figure 36).
These results demonstrate that the structural complexity of the Precambrian basement beneath Ohio is more widespread than previously considered.
89 a) 85°0'0"W 84°0'0"W 83°0'0"W 82°0'0"W 81°0'0"W
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1400000.00® 1600000.00 1800000.00 2000000.00 2200000.00 2400000.00r 2600000.00 West Virginia 38°30'0"N c 38°30'0"N 012.5 25 50 75 100 Kentucky 30 Kilometers km b) 1,200,000 84°0'0"W1,600,000 2,000,000 2,400,000 profile A 0
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West-dipping Coshocton zone
50 km East-dipping Grenville Figure 36: General structure of southern Ohio. a) thickness variation of the crust, the expected anorthosite body, the east dipping Grenville Front Tectonic Zone (GFTZ) and the west dipping Coshocton zone (CZ). b) cross-sections along profile A, E and I showing the extent of expected major structure and lithology. 90 REFERENCES
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Bickford, M., Van Schmus, W., and Zietz, I., 1986, Proterozoic history of the midcontinent region of North America: Geology, v. 14, pp. 492-496.
Cannon, W., 1994, Closing of the midcontinent rift----A far-field effect of Grenville compression: Geology, v. 22, pp. 155-158.
Castle, J., 2001, Appalachian basin stratigraphic response to convergent-margin structural evaluation: Basin Research, v. 13, pp. 397-418.
Culotta, R., Pratt, T., and Oliver, J., 1990, A tale of two sutures: COCORP’s deep seismic surveys of the Grenville province in the eastern U.S. midcontinent: Geology, v. 18, pp. 646-649.
Dean, S., Baranoski, M., July 22, 2002, A look at western Ohio’s Precambrian tectonic setting: Oil & Gas Journal, pp. 34-37.
Dean, S., and Baranoski, M., July 29, 2002, Deeper study of Precambrian warranted in western Ohio: Oil & Gas Journal, pp. 37-39.
Dickas, A., Mndrey, Jr. M., Ojakangas, R., and Shrake, D., 1992, a possible southeastern extension of the midcontinent rift system located in Ohio: Tectonic, v. 11, NO. 6, pp. 1406-1414.
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91
Forsyth, D., Milkereit, B., Davidson, A., Hanmer, S., Hutchinson, D., Hinze, W., and Mereu, R., 1994, Seismic images of a tectonic subdivision of the Grenville Orogen beneath lakes Ontario and Erie: Canadian Journal of Earth Science, v. 31, pp. 229-242.
Gordon, M., and Hempton, M., 1986, Collision-induced rifting: The Grenville orogeny and the Keweenawan rift of North America: Tectonophysics 127, pp. 1-25.
Green, A., Milkereit, B., Davidson, A., Spencer, C., Hutchinson, D., Lee, M., Agena, W., Behrendt, J., and Hinze, W, 1988, Crustal structure of the Grenville front and adjacent terranes: Geology, v. 16, pp. 788-792.
Hauser, E., 1993, Grenville foreland thrust belt hidden beneath the eastern U.S. midcontinent: Geology, v. 21, pp. 61-64.
Kim, J., von Frese, R., and Kim, H., 2000, Crustal modeling from spectrally correlated free-air and terrain gravity data—A case study of Ohio: Geophysics, v. 65, NO. 4, pp. 1057-1069.
Lucius, J. E., 1985, Crustal geology of Ohio inferred from aeromagnetic and gravity anomaly analysis: M.Sc. Thesis (unpubl.), The Ohio State University.
Lucius, J., and von Frese, R., 1988, Aeromagnetic and gravity anomaly constraints on the crustal geology of Ohio: Geological Society of America Bulletin, v. 100, pp. 104-116.
Milkereit, B., Forsyth, D., Green, A., Davidson, A., Hanmer, S., Hutchinson, D., Hinze, W., and Mereu, R., 1992, Seismic images of a Grenville terrane boundary: Geology, v. 20, pp. 1027-1030.
Pratt, R., Culotta, R., Hauser, E., Nelson, D., Brown, L., Kaufman, S., and Oliver, J., 1989, Major Proterozoic basement features of the eastern midcontinent of North revealed by recent COCORP profiling: Geology, v. 17, pp. 505-509.
Potter, P., Richard, B., Wolf, P., and Sitler, G., 1991, Pre-Mount Simon basin under the Cincinnati Arch: Geology, v. 19, pp. 139-142.
Richard, B., Wolfe, P., and Potter, P., 1997, Pre-Mount Simon basin of western Ohio: Geological Society of America, Special Paper 312.
Root, S., 1989, Basement control of structure in the Gettysburg rift basin, Pennsylvania and Maryland: Tectonophysics 166, pp. 281-292.
92 Root, S., 1996, Recurrent basement faulting and basin evaluation, West Virginia and Ohio: The Burning Spring-Cambridge fault zone: Geological Society of America, Special Paper 308, pp. 127-137.
Root, S., and Onasch, C., 1999, Structure and tectonic evaluation of the transitional region between the central Appalachian foreland and interior cratonic basins: Tectonophysics 305, pp. 205-223.
Schmus, W., Bickford, M., and Turek, A., 1996, Proterozoic geology of the east-central midcontinent basement: Geological Society of America, Special Paper 308, pp. 7-32.
Shrake, D., 1991a, The middle run formation: A subsurface stratigraphic unit in southwestern Ohio: Ohio Journal of Science, v. 91, NO. 1, pp. 49-55.
Shrake, D., Carlton, R., Wickstrom, L., Potter, P., Richard, B., Wolfe, P., and Sitler, G., 1991b, Pre-Mount Simon basin under the Cincinnati Arch: Geology, v. 19, pp. 139-142.
Shumaker, R., and Wilson, T., 1996, Basement structure of the Appalachian foreland in West Virginia: Its style and effect on sedimentation: Geological Society of America, Special Paper 308, pp. 139-155.
Steigerwalt, R., (2002), New Evidence for Shallow Lateral Movement Within the Grenville Province: Implication for Basin Development: a Master thesis, The University of Akron.
Stark, T., 1997, The east continent rift complex: Evidence and conclusion: Geological Society of America, Special Paper 312, pp. 253-266.
Von Frese, R., Jones, M., Kim, J., and Li, W., 1997, Spectral correlation of magnetic and gravity anomalies of Ohio: Geophysics, v. 62, NO. 1, pp.365-380.
93 APPENDIX
94 APPENDIX A List of wells penetrate Precambrian surface in Ohio and available depths and lithologies of the Precambrian rocks. COUNTY TOWNSHIP WELL LOCATION PERMIT PC DEPTH LITHOLOGY DESCRIPTION Lat. Long. NO. TOP (ft) IN PC (ft)
Adams BRATTON 39.0320 83.4033 12 Adams FRANKLIN 39.0487 83.3650 11 3865 Adams JEFFERSON 38.7825 83.3346 4 3769 21 Quartiz monzonite Adams JEFFERSON 38.8258 83.2927 5 3772 57 Granite Allen SHAWNEE 40.7146 84.1366 71 3142 30 Granite Allen SHAWNEE 40.7100 84.1340 Lithic areanite Allen SHAWNEE 40.7188 84.1332 84 3148 22 Granite
95 Allen SPENCER 40.7710 84.3818 60 3186 20 Granite Allen SPENCER 40.7645 84.3786 64 Ashland RUGGLES 41.0136 82.3928 3938 Ashtabula ASHTABULA 41.9078 80.7324 40010 5972 Ashtabula DENMARK 41.7183 80.6826 3948 Ashtabula MORGAN 41.7084 80.8237 286 6606 53 Granite gneiss Ashtabula NEW LYME 41.6131 80.7829 1847 7108 Granite gneiss Ashtabula NEW LYME 41.6036 80.7885 2038 7127 Granite gneiss Ashtabula NEW LYME 41.6169 80.7798 2272 7120 Ashtabula PIERPONT 41.7564 80.6099 193 6892 1 Amphibolite Ashtabula TRUMBULL 41.6990 80.9372 191 6740 10 Granite gneiss Auglize ST. MARYS 40.5038 84.3939 71 2960 107 Silicified rock Brown STERLING 39.0555 83.9546 6 Butler LEMON 39.4861 84.3562 4 3236 60 Rhyolite prophyry, lithic arenite Clark HARMONY 39.8875 83.5949 3 3535 35 Diorite COUNTY TOWNSHIP WELL LOCATION PERMIT PC DEPTH LITHOLOGY DESCRIPTION Lat. Long. NO. TOP (ft) IN PC (ft)
Clark MADISON 39.7894 83.6763 40004 3419 1228 Arkose or grawacke Clark PLEASANT 39.9656 83.5848 2 3620 14-24 Gabbro Clermont STONELICK 39.1451 84.1571 3 3345 125 Andesite Clinton WAYNE 39.3805 83.6147 2 3390 67 Diorite Clinton WAYNE 39.3817 83.6233 5 3210 49 Amphibolite Clinton WAYNE 39.4133 83.6754 7 3460 2 Amphibolite Clinton WILSON 39.5267 83.7016 10 3554 Columniana HANOVER 40.7862 80.8704 648 10200 42 Metamorphic Coshocton FRANKLIN 40.1936 81.8522 3462 7585 Coshocton JEFFERSON 40.3234 82.0021 2053 6964 6 Quartiz-monzonite gneiss Coshocton KEENE 40.3694 81.8336 4118 7296 Crawford CHATFIELD 40.9101 82.8837 50 3410 3 Monzonite 96 Crawford CHATFIELD 40.9101 82.8837 50 Crawford LYKENS 40.9181 83.0635 44 3781 4 Granite Crawford LYKENS 40.9181 83.0635 44 Cuyahoga CITY OF CLEVELAND 41.4645 81.6859 821 5750 51 Amphibolite Cuyahoga MAYFIELD 41.5476 81.4519 1625 Defiance MARK 41.3242 84.5939 28 Delware BROWN 40.3529 82.9878 242 3990 45 Gneissic granite Delware GENOA 40.1552 82.8835 269 4053 18 Granite gneiss Delware KINGSTON 40.3280 82.9157 356 Delware ORANGE 40.1505 83.0290 1 3845 446 Granite gneiss Delware OXFORD 40.3953 82.9328 9 4000 26 Granite gneiss Delware PORTER 40.3448 82.7564 270 4685 15 Plagioclase gneiss Delware RADNOR 40.3699 83.1558 22 3420 1 COUNTY TOWNSHIP WELL LOCATION PERMIT PC DEPTH LITHOLOGY DESCRIPTION Lat. Long. NO. TOP (ft) IN PC (ft)
Delware THOMPSON 40.3513 83.2256 322 Delware TRENTON 40.2616 82.7698 354 Delware TRENTON 40.2441 82.8032 358 Delware TROY 40.3431 83.0600 329 Erie FLORENCE 41.3024 82.3986 7 4400 24 Granite gneiss Erie FLORENCE 41.3043 82.3505 11 4455 8 Quartiz-monzonite gneiss Erie FLORENCE 41.3115 82.3516 19 4449 16 Quartiz-Feldspar gneiss Erie KELLEYS ISLAND 41.6073 82.7235 171 Fairfield CLEAR CREEK 39.5661 82.7571 1266 Fayette CONCORD 39.4580 83.5107 2 3340 150 Amphibolite Fayette CONCORD 39.4580 83.5107 2 3340
97 Fayette JASPER 39.5876 83.5801 4 3380 30 Trachyte potphyry Fayette JASPER 39.5876 83.5801 4 3332 Fayette MADISON 39.6785 83.2907 9 3498 Granite Fayette MARION 39.5801 83.3766 11 3240 Granite Fayette UNION 39.4978 83.4174 1 3545 1162 Dolomitic marble calcsilicate hornfels, amphibolite, pyeroxene hornfeles, granite pegmatite Fayette UNION 39.4978 83.4174 1 3548 Fayette WAYNE 39.4296 83.3546 10 3666 Granite Franklin FRANKLIN 39.9886 83.0824 14 3606 16 Gneissic granite Fulton SWAN CREEK 41.5438 83.9322 49 3560 140 Granite with hornfelse Guernsey ADAMS 40.0368 81.7205 782 8331 271 Amphibolit, top 10 ft are granite gneiss Hancock AMANDA 40.9367 83.5127 140 2795 2 Granite gneiss or schist COUNTY TOWNSHIP WELL LOCATION PERMIT PC DEPTH LITHOLOGY DESCRIPTION Lat. Long. NO. TOP (ft) IN PC (ft)
Hancock JACKSON 40.9855 83.6393 152 2795 12 Granite, highly altered Hancock MARION 1583 2770 210 Gneissic granite Hancock UNION 40.9369 83.7687 139 3008 9 Granite Hardin DUDLEY 40.6412 83.4842 79 Hardin JACKSON 40.7505 83.5282 74 2840 Hardin JACKSON 40.7472 83.5404 133 Hardin MARION 41.0693 83.5920 47158 Henry HARRISON 41.3581 84.0275 36 3425 55 Granite Henry RICHFIELD 41.3300 83.9592 137 Highland FAIRFIELD 39.3724 83.5535 1 3515 1 Metamorphics Highland FAIRFIELD 39.3160 83.5213 7 3573 37 Monzonite Hocking STARR 39.3985 82.3894 1222 6470 25 Granite gneiss 98 Holmes KILLBUCK 40.4637 81.9893 5070 Holmes KILLBUCK 40.4603 81.9760 5231 Huron PERU 41.2070 82.6688 11 3901 350 Biotite schist, granite gneiss Jackson FRANKLIN 38.9658 82.5925 76 6230 90 Plagioclase gneiss, amphibolite Jackson FRANKLIN 38.9458 82.6694 79 5993 1 Granitic Jackson FRANKLIN 39.0087 82.6386 102 5984 Jackson HAMILTON 38.8753 82.7437 78 5575 106 Andesine-biotite gneiss Knox HILLIAR 40.2803 82.7282 1604 4773 27 Granite gneiss Knox MILFORD 40.3256 82.5646 1468 5340 30 Syenite at top, amphibolite below Knox MILLER 40.3102 82.5363 3915 Knox MILLER 40.2967 82.4755 4064 Knox PIKE 40.5196 82.3871 1413 5715 30 Granite gneiss Lake PAINESVILLE 41.7498 81.2668 661 COUNTY TOWNSHIP WELL LOCATION PERMIT PC DEPTH LITHOLOGY DESCRIPTION Lat. Long. NO. TOP (ft) IN PC (ft)
Lake PERRY 41.7506 81.1569 142 6065 10 Chlorite schist, diorite gneiss Lake PERRY 41.7455 81.1626 280 6096 Lawrence SYMMES 38.7313 82.4839 174 6950 Licking HARTFORD 40.2332 82.7157 2057 4910 5 Granite gneiss Licking LIMA 39.9779 82.7395 2252 4789 13 Amphipolite or schist Licking MARY ANN 40.1564 82.3216 1826 5980 11 Gneissic granite Licking PERRY 40.1394 82.2143 4792 6215 Logan MCARTHUR 40.4561 83.7717 18 3253 109 Rhyolite Logan RUSH CREEK 40.4157 83.6159 96 Lorain HENRIETTA 41.2893 82.3209 794 4570 20 Granite gneiss Lucas HARDING 41.6179 83.8189 60 3623 292 Granite gneiss and graphite schist Madison FAIRFIELD 39.8686 83.3209 3 3617 14 Granite 99 Madison RANGE 39.7306 83.4302 7 Marion BIG ISLAND 40.5865 83.2537 168 Marion BIG ISLAND 40.5872 83.2294 174 Marion BIG ISLAND 40.5882 83.2546 176 Marion CLARIDON 40.5812 83.0030 8 3665 10 Hornb;ende gneiss Marion CLARIDON 40.5664 83.0510 49 3449 3 Marion GRAND 40.6446 83.3415 167 Marion MONTGOMERY 40.6148 83.4190 85 Marion MONTGOMERY 40.5990 83.3750 173 Medina GRANGER 41.1772 81.7392 1201 6640 88 Granite gneiss Medina HINCKLEY 41.2289 81.7027 1143 6580 460 Granitic gneiss Medina HOMER 41.0394 82.1671 1819 5648 10 Mercer CENTER 40.6316 84.5162 141 3150 15 Rhyolite COUNTY TOWNSHIP WELL LOCATION PERMIT PC DEPTH LITHOLOGY DESCRIPTION Lat. Long. NO. TOP (ft) IN PC (ft)
Miami LOST CREEK 40.0651 84.0854 3 3256 257 Trachyte-latite porphyry Miami WASHINGTON 40.1785 84.3157 1 3282 126 Granite, lithic arenite Morrow BENNINGTON 40.3566 82.8223 1388 4445 5 Granite gneiss Morrow CANAAN 40.5702 82.9120 12 4002 98 Granite gneiss Morrow CANAAN 40.5883 82.9509 2550 3875 1 Granite gneiss Morrow CONGRESS 40.6054 82.7234 4043 Morrow PERRY 40.5700 82.6835 3737 Morrow PERU 40.3941 82.8705 1681 4195 20 Granite gneiss or graphite Morrow TROY 40.6905 82.6815 47 4870 20 Diorite gneiss Morrow WESTFIELD 40.4365 82.9242 33 4009 39 Granite gneiss Muskingum MADISON 40.1210 81.9562 7076 7373
100 Noble ELK 39.6110 81.3475 1278 11415 27 Amphibolite Paulding JACKSON 41.1220 84.4815 13 3392 Perry JACKSON 39.7180 82.3012 6595 6302 Pickaway JACKSON 39.6592 83.0911 4 3685 45 Granite gneiss Pickaway MONROE 39.6803 83.1799 2 3145 110 35 ft dolomitic marble, gabbro or pyroxene hornfelse Pickaway MUHLENBERG 39.6733 83.1240 20 3803 Granite Pickaway PICKAWAY 39.5311 82.9623 6 4148 12 Weathered biotite gneiss Pickaway PICKAWAY 39.5414 82.9245 24 4310 Pike NEWTON 39.0280 83.1285 89 Portage DEERFIELD 41.0353 81.0698 2860 8720 Putnam LIBERTY 41.0954 84.0895 31 3250 127 Granite, lithic arenite Richland MADISON 40.7792 82.5190 448 5061 20 Granite gneiss Richland WASHINGTON 40.6884 82.4808 431 5495 8 Granite gneiss COUNTY TOWNSHIP WELL LOCATION PERMIT PC DEPTH LITHOLOGY DESCRIPTION Lat. Long. NO. TOP (ft) IN PC (ft)
Ross BUCKSKIN 39.3863 83.3113 21 3870 Ross CONCORD 39.4310 83.2983 9 3845 17 Granite gneiss Sandusky BALLVILLE 41.2609 83.1825 126 2615 62 Granite Sandusky MADISON 41.3722 83.3419 146 2756 3 Granite Sandusky RICE 41.4407 83.0558 1 2701 95 Granite Sandusky RILEY 41.3712 82.9814 210 2932 1 Sandusky RILEY 41.3711 82.9834 224 2930 Sandusky RILEY 41.3683 82.9806 225 2890 Sandusky RILEY 41.3687 82.9770 226 2905 Sandusky RILEY 41.3714 82.9824 235 2936 Sandusky RILEY 41.3733 82.9854 238 2930 Granite
101 Sandusky TOWNSEND 41.3542 82.9128 77 3092 31 Granite gneiss Sandusky WASHINGTON 41.4356 83.2803 117 2706 9 Amphibolite with granite above and below Sandusky WOODVILLE 41.4377 83.3165 147 2755 30 Biotite hornblend gneiss Sandusky WOODVILLE 41.4129 83.3709 40158 (D-1) 2667 155 Granite, amphybolite Scioto GREEN 38.5913 82.8209 212 5580 37 Amphybolite Scioto GREEN 38.5910 82.8215 252 Scioto GREEN 38.5923 82.8207 40033 Scioto RARDEN 38.9887 83.2377 257 4382 Seneca ADAMS 41.1815 83.0567 128 3140 34 Seneca CLINTON 41.1580 83.1845 212 Seneca CLINTON 41.1524 83.1836 216 2762 Seneca CLINTON 41.1533 83.1835 244 Seneca HOPEWELL 41.1600 83.2554 213 2610 COUNTY TOWNSHIP WELL LOCATION PERMIT PC DEPTH LITHOLOGY DESCRIPTION Lat. Long. NO. TOP (ft) IN PC (ft)
Seneca HOPEWELL 41.1657 83.2494 214 2460 Seneca LIBERTY 41.1684 83.2443 218 2425 Seneca LIBERTY 41.2265 83.2048 40840 Seneca PLEASANT 41.1904 83.1862 211 2750 Seneca PLEASANT 41.1920 83.1394 40890 2900 35 Granite Seneca PLEASANT 41.1920 83.1394 40890 Shelby PERRY 40.3109 84.0874 12 3140 125 Trachyte porphyry Shelby PERRY 40.2711 84.0598 103 Shelby SALEM 40.3599 84.0934 13 3287 73 Rhyolite Summit NORTHAMPTON 41.1685 81.5333 907 7150 Union DOVER 40.2489 83.2769 67
102 Union DOVER 40.2274 83.2655 69 Union DOVER 40.2257 83.2756 74 Union UNION 40.1211 83.4380 2 3348 7 Granite top half, schist below Union WASHINGTON 40.4654 83.4033 13 2985 4 Amphybolite Van Wert JENNINGS 40.7572 84.3996 44 3214 28 Warren 39.5658 84.1142 DGS 2627 1600 582 Lithic areanite Wayne CHIPPEWA 40.9318 81.7202 71 6904 15 Granite gneiss Wayne WAYNE 40.8605 81.9057 1419 6710 187 Amphybolite Williams ST. JOSEPH 41.4632 84.7496 34 3910 227 Andesite Wood CENTER 41.3483 83.6435 229 2710 55 Granite gneiss or granite Wood CENTER 41.4186 83.5992 237 2800 27 Granite Wood LIBERTY 41.2548 83.6636 231 2760 10 Granite Wood LIBERTY 41.2548 83.6636 231 Wood LIBERTY 41.3421 83.6818 423 COUNTY TOWNSHIP WELL LOCATION PERMIT PC DEPTH LITHOLOGY DESCRIPTION Lat. Long. NO. TOP (ft) IN PC (ft)
Wood LIBERTY 41.3272 83.6724 432 Wood LIBERTY 41.3141 83.6579 40438 2884 43 Granite gneiss Wood MIDDLETON 41.4610 83.7112 239 2800 25 Granitic gneiss or granite Wood PLAIN 236 2775 15 Granite gneiss or schist Wood PLAIN 41.4285 83.6613 236 Wyandot CRAWFORD 40.9593 83.4145 72 2800 7 Granite Wyandot EDEN 40.8952 83.1211 211 3240 20 Monzonite Wyandot JACKSON 40.7437 83.4216 40610 Granite Wyandot MIFFLIN 40.7875 83.3345 174 2860 40 Quartz-monzonite gneiss Wyandot SALEM 40.8184 83.4132 173 2857 13 Amphybolite 103