DOCSLIB.ORG

Paleomagnetic Investigation of Igneous Rocks Deformed by the Keweenaw Fault in the Northwestern Keweenaw Peninsula

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Paleomagnetic Investigation of Igneous Rocks Deformed by the Keweenaw Fault in the Northwestern Keweenaw Peninsula Michigan Technological University Digital Commons @ Michigan Tech Dissertations, Master's Theses and Master's Reports 2019 PALEOMAGNETIC INVESTIGATION OF IGNEOUS ROCKS DEFORMED BY THE KEWEENAW FAULT IN THE NORTHWESTERN KEWEENAW PENINSULA. Daniel Trekas Michigan Technological University, [email protected] Copyright 2019 Daniel Trekas Recommended Citation Trekas, Daniel, "PALEOMAGNETIC INVESTIGATION OF IGNEOUS ROCKS DEFORMED BY THE KEWEENAW FAULT IN THE NORTHWESTERN KEWEENAW PENINSULA.", Open Access Master's Thesis, Michigan Technological University, 2019. https://doi.org/10.37099/mtu.dc.etdr/939 Follow this and additional works at: https://digitalcommons.mtu.edu/etdr Part of the Geology Commons, and the Geophysics and Seismology Commons PALEOMAGNETIC INVESTIGATION OF IGNEOUS ROCKS DEFORMED BY THE KEWEENAW FAULT IN THE NORTHWESTERN KEWEENAW PENINSULA. By Daniel B. Trekas A THESIS Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE In Geophysics MICHIGAN TECHNOLOGICAL UNIVERSITY 2019 © 2019 Daniel B. Trekas This thesis has been approved in partial fulfillment of the requirements for the Degree of MASTER OF SCIENCE in Geophysics. Department of Geological and Mining Engineering and Sciences Thesis Advisor: Aleksey Smirnov Committee Member: Chad Deering Committee Member: James DeGraff Department Chair: John Gierke Table of Contents 1.0 Introduction ..................................................................................................................1 1.1 Midcontinent Rift System ...................................................................................................... 1 1.2. The Portage Lake Volcanics ................................................................................................. 6 1.3. Site Descriptions ................................................................................................................... 9 2.0 Methods .......................................................................................................................13 2.1 Sample Collection ................................................................................................................ 13 2.2 Thermal Demagnetization .................................................................................................... 15 2.3 Thermomagnetic Analyses ................................................................................................... 18 2.4 Magnetic Hysteresis Analyses ............................................................................................. 19 3.0 Results .........................................................................................................................22 3.1 Paleomagnetism ................................................................................................................... 22 3.2 Thermomagnetic Analyses ................................................................................................... 41 3.3 Magnetic Hysteresis Analyses ............................................................................................. 47 4.0 Discussion....................................................................................................................52 5.0 Conclusion ..................................................................................................................58 References .........................................................................................................................59 ii List of Figures Figure 1. Map of the Midcontinent Rift ..............................................................................1 Figure 2. Map of the Lake Superior Basin ..........................................................................3 Figure 3. Cross-section of the Lake Superior Basin ...........................................................5 Figure 4. Map of Sample Locations ..................................................................................10 Figure 5. PM01-08 and PM11 sample Outcrop Images ....................................................12 Figure 6. Pomeroy Orienting Fixture with Brunton Compass ..........................................14 Figure 7. 2G Enterprise 760-R SRM .................................................................................15 Figure 8. ASC TD-48SC Thermal Specimen Demagnetizer ............................................16 Figure 9. Example of Demagnetization Behavior .............................................................17 Figure 10. AGICO MFK1-FA Kappabridge .....................................................................19 Figure 11. MicroMag Model 2900 AGM .........................................................................20 Figure 12. Example of a Magnetic Hysteresis Loop .........................................................22 Figure 13. Equal Area and Vector Plot PM01 ..................................................................31 Figure 14. Equal Area and Vector Plot PM02 ..................................................................32 Figure 15. Equal Area and Vector Plot PM03 ..................................................................33 Figure 16. Equal Area and Vector Plot PM04 ..................................................................34 Figure 17. Equal Area and Vector Plot PM05 ..................................................................35 Figure 18. Equal Area and Vector Plot PM09 ..................................................................36 Figure 19. Equal Area and Vector Plot PM10 ..................................................................37 Figure 20. Equal Area and Vector Plot PM11 ..................................................................38 Figure 21. Equal Area and Vector Plot PM06 ..................................................................40 iii Figure 22. Equal Area and Vector Plot PM07 ..................................................................40 Figure 23. Equal Area and Vector Plot PM08 ..................................................................41 Figure 24. Thermal Demagnetization Curves PM01-PM04 .............................................45 Figure 25. Thermal Demagnetization Curves PM05 & PM09-PM11 ..............................46 Figure 26. Thermal Demagnetization Curves PM06 & PM07 .........................................47 Figure 27. Magnetic Hysteresis Loops PM01-PM04 ........................................................48 Figure 28. Magnetic Hysteresis Loops PM05-PM07 & PM11 .........................................49 Figure 29. Backfield Demagnetization Plots PM01-04 ....................................................50 Figure 30. Backfield Demagnetization Plots PM05-07 & PM11 .....................................51 Figure 31. Day Plot of Hysteresis Data PM01-PM07 & PM11 ........................................52 Figure 32. Equal-area Plot with a Summary of Paleomagnetic Results ...........................55 Figure 33. Site-mean Paleomagnetic Directions for Sites PM02 and PM09, Browning, and Beske-Diehl (1987), and from Kulakov (2014) ..........................................................56 iv List of Tables Table 1. Previous Paleomagnetic Data for the PLV............................................................8 Table 2. PM01-PM11 Site Coordinates and Summary .....................................................11 Table 3. Site PM01 Summary ...........................................................................................23 Table 4. Site PM02 Summary ...........................................................................................24 Table 5. Site PM03 Summary ...........................................................................................25 Table 6. Site PM04 Summary ...........................................................................................26 Table 7. Site PM05 Summary ...........................................................................................26 Table 8. Site PM06 Summary ...........................................................................................27 Table 9. Site PM07 Summary ...........................................................................................27 Table 10. Site PM08 Summary .........................................................................................28 Table 11. Site PM09 Summary. ........................................................................................28 Table 12. Site PM10 Summary .........................................................................................29 Table 13. Site PM11 Summary .........................................................................................29 Table 14. PM01-PM11 Result Summary ..........................................................................54 v Acknowledgments I would like to thank my advisor Aleksey Smirnov and committee members Chad Deering and James DeGraff for all there help and advice throughout my research. I would like to thank all those who helped me with my research. All those who have helped me with lab work: Katie Bristol, Marine Foucher, Sonia Jin, and Adren Rigdon All those who have helped me with sample collection: Graham Hubbell, Elisa Piispa, Leonid Surovitckii, and Colin Tyrrell Property owners of sample sites for allowing me to sample: Chuck Brumleve, Hal Baldauf, Gina Nicholas, Frank Nicholas, and The Keweenaw Community Forest Company Lastly, I would like to thank my friends and family for all the support during my education and research. vi Abstract
Load more

Recommended publications
  • Strike and Dip Refer to the Orientation Or Attitude of a Geologic Feature. The
    Name__________________________________ 89.325 – Geology for Engineers Faults, Folds, Outcrop Patterns and Geologic Maps I. Properties of Earth Materials When rocks are subjected to differential stress the resulting build-up in strain can cause deformation. Depending on the material properties the result can either be elastic deformation which can ultimately lead to the breaking of the rock material (faults) or ductile deformation which can lead to the development of folds. In this exercise we will look at the various types of deformation and how geologists use geologic maps to understand this deformation. II. Strike and Dip Strike and dip refer to the orientation or attitude of a geologic feature. The strike line of a bed, fault, or other planar feature, is a line representing the intersection of that feature with a horizontal plane. On a geologic map, this is represented with a short straight line segment oriented parallel to the strike line. Strike (or strike angle) can be given as either a quadrant compass bearing of the strike line (N25°E for example) or in terms of east or west of true north or south, a single three digit number representing the azimuth, where the lower number is usually given (where the example of N25°E would simply be 025), or the azimuth number followed by the degree sign (example of N25°E would be 025°). The dip gives the steepest angle of descent of a tilted bed or feature relative to a horizontal plane, and is given by the number (0°-90°) as well as a letter (N, S, E, W) with rough direction in which the bed is dipping.
    [Show full text]
  • FM 5-410 Chapter 2
    FM 5-410 CHAPTER 2 Structural Geology Structural geology describes the form, pat- secondary structural features. These secon- tern, origin, and internal structure of rock dary features include folds, faults, joints, and and soil masses. Tectonics, a closely related schistosity. These features can be identified field, deals with structural features on a and m appeal in the field through site inves- larger regional, continental, or global scale. tigation and from remote imagery. Figure 2-1, page 2-2, shows the major plates of the earth’s crust. These plates continually Section I. Structural Features undergo movement as shown by the arrows. in Sedimentary Rocks Figure 2-2, page 2-3, is a more detailed repre- sentation of plate tectonic theory. Molten material rises to the earth’s surface at BEDDING PLANES midoceanic ridges, forcing the oceanic plates Structural features are most readily recog- to diverge. These plates, in turn, collide with nized in the sedimentary rocks. They are adjacent plates, which may or may not be of normally deposited in more or less regular similar density. If the two colliding plates are horizontal layers that accumulate on top of of approximately equal density, the plates each other in an orderly sequence. Individual will crumple, forming mountain range along deposits within the sequence are separated the convergent zone. If, on the other hand, by planar contact surfaces called bedding one of the plates is more dense than the other, planes (see Figure 1-7, page 1-9). Bedding it will be subducted, or forced below, the planes are of great importance to military en- lighter plate, creating an oceanic trench along gineers.
    [Show full text]
  • Semester -3 Civil Engineering
    CIVIL ENGINEERING SEMESTER -3 CIVIL ENGINEERING Year of MECHANICS OF CATEGORY L T P CREDIT CET201 Introduction SOLIDS PCC 3 1 0 4 2019 Preamble: Mechanics of solids is one of the foundation courses in the study of structural systems. The course provides the fundamental concepts of mechanics of deformable bodies and helps students to develop their analytical and problem solving skills. The course introduces students to the various internal effects induced in structural members as well as their deformations due to different types of loading. After this course students will be able to determine the stress, strain and deformation of loaded structural elements. Prerequisite: EST 100 Engineering Mechanics Course Outcomes: After the completion of the course the student will be able to Prescribed Course Description of Course Outcome Outcome learning level Recall the fundamental terms and theorems associated with CO1 Remembering mechanics of linear elastic deformable bodies. Explain the behavior and response of various structural CO2 Understanding elements under various loading conditions. Apply the principles of solid mechanics to calculate internal stresses/strains, stress resultants and strain energies in CO3 Applying structural elements subjected to axial/transverse loadsand bending/twisting moments. Choose appropriate principles or formula to find the elastic CO4 constants of materials making use of the information Applying available. Perform stress transformations, identify principal planes/ CO5 stresses and maximum shear stress at a point
    [Show full text]
  • Regional Gravity Investigation of the Eastern Portion of the Northern Peninsula of Michigan
    REGIONAL GRAVITY INVESTIGATION OF THE EASTERN PORTION OF THE NORTHERN PENINSULA OF MICHIGAN By Erdogan Oray A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Geology 1971 PLEASE NOTE: Some pages may have indistinct print. Filmed as received. University Microfilms, A Xerox Education Company ABSTRACT REGIONAL GRAVITY INVESTIGATION OF THE EASTERN PORTION OF THE NORTHERN PENINSULA OF MICHIGAN By Erdogan Oray A regional gravity investigation was conducted to delineate the Precambrian features of the eastern portion of the Northern Peninsula of Michigan in relation to the tectonic framework of the Lake Superior region and the Southern Peninsula of Michigan. During the survey, an area of 12,000 square miles in the Northern Peninsula of Michigan was covered by a total of 1,003 gravity stations. An additional 851 gravity stations previously observed in the Southern Peninsula of Michigan, Beaver Island, northern Lake Huron, northern Lake Michigan and Sault Ste. Marie area of Canada were used to establish the regional gravity pattern. The Bouguer Gravity Anomaly Map with the aid of a Double Fourier Series Residual Gravity Map indicates that the eastern portion of the Northern Peninsula is associated with two major linear positive gra­ vity anomalies. One of these anomalies trends south from Whitefish Point on the south shore of Lake Superior and is associated with ba­ salts upthrown into a horst within the eastern limb of the Lake Sup­ erior syncline. This anomaly is correlated with the Middle Keweenawan Erdogan Oray volcanics outcropping on Mamainse Point, Ontario.
    [Show full text]
  • The Mylonite Issue 16 November 2008
    INSIDE • News from the Chair • Special Announcements • Faculty • Alumni The Newsletter of the Geological Sciences Dept. Calif. State Polytechnic University Pomona, Calif. The Mylonite Issue 16 November 2008 NEWS FROM THE CHAIR NOTE FROM THE CHAIR 2008 Spending was severely curtailed. The Mylonite Once again, greetings to each and every one of was one of those “non-essential” items. It was only you! This will be the last letter I write to you all as Chair through collective Department persistence, the immense of the Geological Sciences Department. It is time for a help of Ms. Mary Jo Gruca, the College’s Development change in leadership, new ideas and new approaches. I Director, and the University’s Office of Advancement will end my tenure as Chair at the commencement of the were we able to send the Mylonite out to all of you. It spring quarter of 2009. At that time, Dr. Jon Nourse will was no easy task. take over the responsibilities. It has been a true pleasure All faculty searches within the College of and a privilege to have served you all for so long. Science were cancelled. Geology had already begun Reflecting back on this past year, there is no doubt it was advertising and was receiving applications when our my most difficult year as Chair. The report below is far search for a Sedimentary Geologist was ended. As of from up beat and only peripherally related to my this writing, the Sedimentary Geology position remains stepping down as chair. vacant and there is no faculty search underway.
    [Show full text]
  • The End of Midcontinent Rift Magmatism and the Paleogeography of Laurentia
    THEMED ISSUE: Tectonics at the Micro- to Macroscale: Contributions in Honor of the University of Michigan Structure-Tectonics Research Group of Ben van der Pluijm and Rob Van der Voo The end of Midcontinent Rift magmatism and the paleogeography of Laurentia Luke M. Fairchild1, Nicholas L. Swanson-Hysell1, Jahandar Ramezani2, Courtney J. Sprain1, and Samuel A. Bowring2 1DEPARTMENT OF EARTH AND PLANETARY SCIENCE, UNIVERSITY OF CALIFORNIA, BERKELEY, CALIFORNIA 94720, USA 2DEPARTMENT OF EARTH, ATMOSPHERIC AND PLANETARY SCIENCES, MASSACHUSETTS INSTITUTE OF TECHNOLOGY, CAMBRIDGE, MASSACHUSETTS 02139, USA ABSTRACT Paleomagnetism of the North American Midcontinent Rift provides a robust paleogeographic record of Laurentia (cratonic North America) from ca. 1110 to 1070 Ma, revealing rapid equatorward motion of the continent throughout rift magmatism. Existing age and paleomagnetic constraints on the youngest rift volcanic and sedimentary rocks have been interpreted to record a slowdown of this motion as rifting waned. We present new paleomagnetic and geochronologic data from the ca. 1090–1083 Ma “late-stage” rift volcanic rocks exposed as the Lake Shore Traps (Michigan), the Schroeder-Lutsen basalts (Minnesota), and the Michipicoten Island Formation (Ontario). The paleomagnetic data allow for the development of paleomagnetic poles for the Schroeder-Lutsen basalts (187.8°E, 27.1°N; A95 = 3.0°, N = 50) and the Michipicoten Island Formation (174.7°E, 17.0°N; A95 = 4.4°, N = 23). Temporal constraints on late-stage paleomagnetic poles are provided by high-precision, 206Pb-238U zircon dates from a Lake Shore Traps andesite (1085.57 ± 0.25 Ma; 2σ internal errors), a Michipicoten Island Formation tuff (1084.35 ± 0.20 Ma) and rhyolite (1083.52 ± 0.23 Ma), and a Silver Bay aplitic dike from the Beaver Bay Complex (1091.61 ± 0.14 Ma), which is overlain by the Schroeder-Lutsen basalt flows.
    [Show full text]
  • PLANE DIP and STRIKE, LINEATION PLUNGE and TREND, STRUCTURAL MEASURMENT CONVENTIONS, the BRUNTON COMPASS, FIELD BOOK, and NJGS FMS
    PLANE DIP and STRIKE, LINEATION PLUNGE and TREND, STRUCTURAL MEASURMENT CONVENTIONS, THE BRUNTON COMPASS, FIELD BOOK, and NJGS FMS The word azimuth stems from an Arabic word meaning "direction“, and means an angular measurement in a spherical coordinate system. In structural geology, we primarily deal with land navigation and directional readings on two-dimensional maps of the Earth surface, and azimuth commonly refers to incremental measures in a circular (0- 360 °) and horizontal reference frame relative to land surface. Sources: Lisle, R. J., 2004, Geological Structures and Maps, A Practical Guide, Third edition http://www.geo.utexas.edu/courses/420k/PDF_files/Brunton_Compass_09.pdf http://en.wikipedia.org/wiki/Azimuth http://en.wikipedia.org/wiki/Brunton_compass FLASH DRIVE/Rider/PDFs/Holcombe_conv_and_meas.pdf http://www.state.nj.us/dep/njgs/geodata/fmsdoc/fmsuser.htm Brunton Pocket Transit Rider Structural Geology 310 2012 GCHERMAN 1 PlanePlane DipDip andand LinearLinear PlungePlunge horizontal dddooo Dip = dddooo Bedding and other geological layers and planes that are not horizontal are said to dip. The dip is the slope of a geological surface. There are two aspects to the dip of a plane: (a) the direction of dip , which is the compass direction towards which the plane slopes; and (b) the angle of dip , which is the angle that the plane makes with a horizontal plane (Fig. 2.3). The direction of dip can be visualized as the direction in which water would flow if poured onto the plane. The angle of dip is an angle between 0 ° (for horizontal planes) and 90 ° (for vertical planes). To record the dip of a plane all that is needed are two numbers; the angle of dip followed by the direction (or azimuth) of dip, e.g.
    [Show full text]
  • MIDCONTINENT RIFT SYSTEM BIBLIOGRAPHY by Steven A
    MIDCONTINENT RIFT SYSTEM BIBLIOGRAPHY By Steven A. Hauck December 1995 Technical Report NRRI/TR-95/33 Funded by the Natural Resources Research Institute In Preparation for the 1995 International Geological Correlation Program Project 336 Field Conference in Duluth, MN Natural Resources Research Institute University of Minnesota, Duluth 5013 Miller Trunk Highway Duluth, MN 55811-1442 TABLE OF CONTENTS INTRODUCTION ................................................... 1 THE DATABASE .............................................. 1 Use of the PAPYRUS Retriever Program (Diskette) .............. 3 Updates, Questions, Comments, Etc. ......................... 3 ACKNOWLEDGEMENTS ....................................... 4 MIDCONTINENT RIFT SYSTEM BIBLIOGRAPHY ......................... 5 AUTHOR INDEX ................................................. 191 KEYWORD INDEX ................................................ 216 i This page left blank intentionally. ii INTRODUCTION The co-chairs of the IGCP Project 336 field conference on the Midcontinent Rift System felt that a comprehensive bibliography of articles relating to a wide variety of subjects would be beneficial to individuals interested in, or working on, the Midcontinent Rift System. There are 2,543 references (>4.2 MB) included on the diskette at the back of this volume. PAPYRUS Bibliography System software by Research Software Design of Portland, Oregon, USA, was used in compiling the database. A retriever program (v. 7.0.011) for the database was provided by Research Software Design for use with the database. The retriever program allows the user to use the database without altering the contents of the database. However, the database can be used, changed, or augmented with a complete version of the program (ordering information can be found in the readme file). The retriever program allows the user to search the database and print from the database. The diskette contains compressed data files.
    [Show full text]
  • USBR Engineering Geology Field Manual Volume 1 Chapter 6
    Chapter 6 GEOLOGIC MAPPING AND DOCUMENTATION Geologic mapping is defined as the examination of natural and manmade exposures of rock or uncon- solidated materials, the systematic recording of geologic data from these exposures, and the analysis and inter- pretation of these data in two- or three-dimensional format (maps, cross sections, and perspective [block] diagrams). The maps and cross sections generated from these data: (1) serve as a record of the location of factual data; (2) present a graphic picture of the conceptual model of the study area based on the available factual data; and (3) serve as tools for solving three-dimensional problems related to the design, construction, and/or maintenance of engineered structures or site characteri- zation. This chapter presents guidelines for the collection and documentation of surface and subsurface geologic field data for use in the design, specifications, construc-tion, or maintenance of engineered structures and site characterization studies. Responsibilities of the Engineering Geologist An engineering geologist defines, evaluates, and docu- ments site-specific geologic conditions relating to the design, construction, maintenance, and remediation of engineered structures or other sites. This responsibility also may include more regionally based geologic studies, such as materials investigations or regional reconnais- sance mapping. An engineering geologist engaged in geologic mapping is responsible for: • Recognizing the key geologic conditions in a study area that will or could significantly affect hazardous and toxic waste sites or a proposed or existing structure; FIELD MANUAL • Integrating all the available, pertinent geologic data into a rational, interpretive, three-dimensional conceptual model of the study area and presenting this conceptual model to design and construction engineers, other geologists, hydrologists, site managers, and contractors in a form that can be understood.
    [Show full text]
  • Computer-Based Data Acquisition and Visualization Systems in Field Geology
    Computer-based data acquisition and visualization systems in fi eld geology: Results from 12 years of experimentation and future potential Terry L. Pavlis, Richard Langford, Jose Hurtado, and Laura Serpa Department of Geological Sciences, University of Texas at El Paso, El Paso, Texas 79968, USA ABSTRACT attributing is limited to critical information tem (GPS) receivers, digital cameras, recording with all objects carrying a special “note” fi eld compass inclinometers, compass-inclinometer Paper-based geologic mapping is now for input of nonstandard information. We devices that log data and position, and laser archaic, and it is essential that geologists suggest that when fi eld GIS systems become rangefi nders allow us to do things that were transition out of paper-based fi eld work and the norm, fi eld geology should enjoy a revo- impossible only a decade ago. This technology embrace new fi eld geographic information lution both in the attitude of the fi eld geolo- allows new approaches to obtaining, organizing, system (GIS) technology. Based on ~12 yr gist toward his or her data and the ability to and distributing data in all fi eld sciences. This of experience with using handheld comput- address problems using the fi eld information. technology will undoubtedly lead to major new ers and a variety of fi eld GIS software, we However, fi eld geologists will need to adjust advances in fi eld geology, and hopefully revital- have developed a working model for using to the changing technology, and many long- ize this foundation of the geosciences. fi eld GIS systems. Currently this system uses established fi eld paradigms should be reeval- In this paper we explore this issue of changing software products from ESRI (Environmen- uated.
    [Show full text]
  • Western Upper Peninsula Planning & Development Regional Commission
    Western Upper Peninsula Planning & Development Regional Commission th 400 Quincy St., 8 Floor, Hancock, MI 49930 906-482-7205 [email protected] News Release Release Date: September 30, 2020 Media Contact: Rachael Pressley, Assistant Regional Planner 906.482.7205 ext. 116 [email protected] Keweenaw County Hazard Mitigation Plan available for review The Keweenaw County Office of Emergency Measures and the Western Upper Peninsula Planning and Development Region (WUPPDR) have recently made updates to the Keweenaw County Hazard Mitigation Plan. Hazard mitigation is any action taken before, during or after a disaster to eliminate or reduce the risk to human life and property from natural, technological, or human-related hazards. The plan’s purpose is to identify hazard risks throughout the county and to become better prepared for them. The draft of the Keweenaw County 2020-2025 Hazard Mitigation Plan Update will be available through October 30, 2020 for public review and comment prior to plan adoption by all local governments at regular meetings. A formal public hearing will also be held at a County Board meeting to be announced. Copies of the plan draft will be available at WUPPDR (400 Quincy St.) in Hancock and at the Keweenaw County Clerk’s Office (5095 4th St.) in Eagle River, and; online at www.wuppdr.org. Written comments will be considered by WUPPDR in cooperation with Keweenaw County and local governments, as appropriate. Comments must be received by October 30, 2020 and may be mailed to WUPPDR, 400 Quincy St., 8th Floor, Hancock, MI 49930 or emailed to Rachael Pressley, Assistant Regional Planner, at [email protected].
    [Show full text]
  • OFR 07 03.Pdf
    OPEN-FILE REPORT 07-03 VIRGINIA DIVISION OF GEOLOGY AND MINERAL RESOURCES OPEN-FILE REPORT 07-03 SUMMARY OF THE GEOLOGY OF THE BON AIR QUADRANGLE: A SUPPLEMENT TO THE GEOLOGIC MAP OF THE BON AIR QUADRANGLE, VIRGINIA Mark W. Carter, C. R. Berquist, Jr., and Heather A. Bleick a A B s C D COMMONWEALTH OF VIRGINIA DEPARTMENT OF MINES, MINERALS AND ENERGY DIVISION OF GEOLOGY AND MINERAL RESOURCES Edward E. Erb, State Geologist CHARLOTTESVILLE, VIRGINIA 2008 VIRGINIA DIVISION OF GEOLOGY AND MINERAL RESOURCES COVER PHOTOS. Xenoliths and schlieren in Petersburg Granite. A – Biotite-muscovite granitic gneiss. A dashed line marks strong foliation in the rock. Edge of Brunton compass is about 3 inches (7.6 centimeters) long. Outcrop coordinates – 37.54853°N, 77.69229°W, NAD 27. B – Amphibolite xenolith (marked by an “a”) in layered granite gneiss phase of the Petersburg Granite. Faint layering can be seen in granite between hammerhead and xenolith. Hammer is approximately 15 inches (38 centimeters) long. Outcrop coordinates – 37.5050°N, 77.5893 °W, NAD 27. C – Foliation in amphibolite xenolith (marked by a dashed line). Hammerhead is about 8 inches (20 centimeters) long. Outcrop coordinates – 37.5229°N, 77.5790°W, NAD 27. D – Schlieren (marked by an “s”) in foliated granite phase of the Petersburg Granite. Schleiren are oriented parallel to the foliation in the granite. Field of view in photograph is about 2 feet by 3 feet (0.6 meter by 0.9 meter). Outcrop coordinates – 37.5147°N, 77.5352°W, NAD 27. OPEN-FILE REPORT 07-03 VIRGINIA DIVISION OF GEOLOGY AND MINERAL RESOURCES OPEN-FILE REPORT 07-03 SUMMARY OF THE GEOLOGY OF THE BON AIR QUADRANGLE: A SUPPLEMENT TO THE GEOLOGIC MAP OF THE BON AIR QUADRANGLE, VIRGINIA Mark W.
    [Show full text]