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Fluid History of the Sideling Hill Syncline, Hancock County, Maryland

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Fluid History of the Sideling Hill Syncline, Hancock County, Maryland FLUID HISTORY OF THE SIDELING HILL SYNCLINE, HANCOCK COUNTY, MARYLAND William J. Lacek A Thesis Submitted to the Graduate College of Bowling Green State University in Partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August 2015 Committee: John Farver, Advisor, Charles Onasch, Margaret Yacobucci ii ABSTRACT John Farver, Advisor Fluid inclusion microthermometry was employed to determine the fluid history of the Sideling Hill syncline in Maryland with respect to its deformation history. The syncline is unique in the region in that it preserves the youngest rocks (Mississippian) in the Valley and Ridge Province and is the easternmost exposure of Mississippian rocks in this portion of the Central Appalachians. Two types of fluid inclusions were prominent in vein quartz: CH4-rich and two-phase aqueous with the former comprising about 60% of the inclusions observed. The presence of the two fluids in inclusions that appear to be coeval indicates that the migrating fluid was a CH4- saturated aqueous brine that was trapped immiscibly as separate CH4-rich and two-phase aqueous inclusions. Cross cutting relations show that at least two generations of veins formed during deformation. Similarities in chemistry of the inclusions in the different vein generations suggests that a single fluid was present during deformation. Older veins were found to have formed at depths of at least 5 km while younger veins formed at minimum depths of 9 km. Overburden for older veins is attributed to emplacement of the North Mountain Thrust (NMT) sheet (~6 km thick). The thickness of the Alleghanian clastic wedge is calculated to be ~2.5 km in the Appalachian Plateau which accounts for most of the remaining overburden in younger veins. Due to the sediment load imposed by the NMT it is likely that the clastic wedge was thicker at Sideling Hill, with this increased thickness accounting for the remaining 0.5 km. iii ACKNOWLEDGEMENTS I would not have been able to complete my thesis were it not for the support of my family, advisor, committee members and friends. First I want to acknowledge my advisor Dr. John Farver for his support and patience as well as keeping me on track throughout my research as well as comic relief when needed. I would also like to thank Dr. Charles Onasch who provided great insight into the subject of my research and assistance when problems occurred. Dr. Margaret Yacobucci who provided assistance with the historical aspect of my research and critiques of my research. I would like to thank Dr. David Matchen and Dr. Joe Allen as well as Lisa Karnes, Vickie Hart, and Dr. Rodney Klein for their encouragement to pursue a graduate degree in geology. I would like to express my gratitude to my family who provided endless encouragement and support as well as the friends that I made during the time that I was at BGSU who provided entertainment during the difficult times and a were always willing to chat for a few minutes. Lastly I want to thank my loving wife Monica who always encouraged me to keep moving forward and provided endless support. iv TABLE OF CONTENTS Page INTRODUCTION….................................................................................................................... 1 CHAPTER I BACKGROUND..................................................................................................... 3 Stratigraphy....................................................................................................................... 3 Lithostratigraphy and Hydrostratigraphy.......................................................................... 4 Patterson Creek Anticline Fluid History........................................................................... 5 Pre-Folding Conditions and Fluid History............................................................ 6 Syn-Folding Fluid History.................................................................................... 6 Post-Folding Fluid History................................................................................... 8 Structural Features........................................................................................................... 8 Thrust Sheets................................................................................................................... 9 Depositional Environments and Tectonic History.......................................................... 10 Alleghanian Clastic Wedge............................................................................................ 10 Conodont Alteration....................................................................................................... 11 Fluid Inclusions.............................................................................................................. 11 CHAPTER II METHODS.......................................................................................................... 14 Samples.......................................................................................................................... 14 Fluid Inclusions.............................................................................................................. 14 CH4-Rich Inclusions........................................................................................... 14 Two-Phase Aqueous Inclusions.......................................................................... 15 CO2 Rich inclusions........................................................................................... 15 Single-Phase Aqueous Inclusions...................................................................... 16 v Fluid Inclusions Microthermometry................................................................................ 16 Uncertainty in Analysis of Fluid Inclusions.................................................................... 17 Pressure and Temperature at Trapping............................................................................ 18 Th Isochore Intersection Method......................................................................... 18 ThH Isochore Method........................................................................................... 19 Geothermal Gradient Method............................................................................. 19 CHAPTER III RESULTS........................................................................................................... 21 Vein Relations................................................................................................................. 21 Older Veins.......................................................................................................... 21 Younger Veins...................................................................................................... 21 Fluid Inclusions............................................................................................................... 22 CH4-Rich Inclusions............................................................................................ 23 Two-Phase Aqueous Inclusions........................................................................... 23 CO2 Rich Inclusions............................................................................................ 24 Single-Phase Inclusions...................................................................................... 25 CHAPTER IV DISCUSSION.................................................................................................... 26 Fluid Migrations............................................................................................................. 26 Conditions of Entrapment and Determination of Overburden....................................... 26 Comparison to Castles (2010) and Evans and Battles (2012)........................................ 27 CHAPTER V CONCLUSIONS................................................................................................. 29 REFERENCES........................................................................................................................... 31 APPENDIX A MICORTHERMOMETRIC DATA.................................................................... 60 APPENDIX B HISTOGRAMS.................................................................................................. 70 vi LIST OF FIGURES Figure Page 1 Geology of Maryland with accompanying cross-section............................................... 31 2 Geology of Washington County, Maryland.................................................................... 32 3 Stratigraphic section of central Appalachians................................................................ 33 4 Examples of fluid inclusion types.................................................................................. 34 5 Example of pressure determined using ThH isochore method........................................ 35 6 Example of pressure determined using geothermal gradient method............................ 36 7 Example of pressure determined using Th isochore intersection method...................... 37 8 Locations of sample collection...................................................................................... 38 9 Relative age of veins in sample WP-05-1...................................................................... 39 10 Relative age of veins within sample WP-05-2............................................................... 40 11 Relative age of veins in sample TH-26.......................................................................... 41
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