PALEOENVIRONMENTAL ANALYSIS OF MONTBROOK: AN UNUSUAL FOSSIL LOCALITY FROM THE LATE MIOCENE IN NORTHERN FLORIDA By MICHAEL JOSEPH ZIEGLER A THESIS PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE UNIVERSITY OF FLORIDA 2019 1 © 2019 Michael Joseph Ziegler 2 To Dorothy Helvak 3 ACKNOWLEDGMENTS I would like to formally thank all the enthusiastic volunteers of the Montbrook Fossil Site during the 2017-18 season for their interest and support during fieldwork. I thank Florida Geologic Survey staff for selflessly sharing resources and expertise. I thank my Thompson Earth System Institute: Moonshot Project 2019 Cohort lab group for assisting in the collection of research materials. Similarly, I thank my undergraduate researchers for preparing microfossils used in this study. I thank my graduate advisor and committee for pushing me to be a stronger researcher and communicator of science. With love, I thank my family for endless encouragement and laughter. 4 TABLE OF CONTENTS page ACKNOWLEDGMENTS ...............................................................................................................4 LIST OF TABLES ...........................................................................................................................7 LIST OF FIGURES .........................................................................................................................8 LIST OF ABBREVIATIONS ........................................................................................................10 ABSTRACT ...................................................................................................................................11 CHAPTER 1 MONTBROOK SITE INTRODUCTION ..............................................................................12 Research Inquiry .....................................................................................................................12 An Exceptional Miocene Locality ..........................................................................................13 Florida Platform During the Miocene .....................................................................................16 2 LITHOSTRATIGRAPHY AND FACIES MODELING .......................................................24 Regional Stratigraphic History ...............................................................................................24 Methods ..................................................................................................................................27 Microfacies Analysis .......................................................................................................27 Smear Slide Analysis .......................................................................................................28 Sediment Core Analysis ..................................................................................................30 Results .....................................................................................................................................31 Microfacies Analysis .......................................................................................................31 Rippled sand unit ......................................................................................................32 Massive fossiliferous gravel unit ..............................................................................33 Wavy cross laminated unit .......................................................................................35 Heterolithic flaser unit ..............................................................................................37 Smear Slide Analysis .......................................................................................................39 Sediment Core Analysis ..................................................................................................43 Discussion ...............................................................................................................................46 Smear Slide Analysis .......................................................................................................46 Micofacies Analysis ........................................................................................................51 Sediment Core Analysis ..................................................................................................55 Conclusions .............................................................................................................................58 3 ICHNOFOSSILS AND BIOTURBATION INDEX ..............................................................83 Methods ..................................................................................................................................84 Results .....................................................................................................................................86 Discussion ...............................................................................................................................87 5 Conclusions .............................................................................................................................90 APPENDIX A PALEOMAGNETISM ...........................................................................................................96 B EDUCATION, OUTREACH AND COLLABORATION ...................................................100 LIST OF REFERENCES .............................................................................................................103 BIOGRAPHICAL SKETCH .......................................................................................................114 6 LIST OF TABLES Table page 2-1 Summary of facies assignments in Montbrook outcrop.. ..................................................80 2-2 Summary of smear slide results with patterns of presence and absence of major sediment constituents.. .......................................................................................................81 3-1 Summary of BI analysis including percentage area of primary sediment structures (P.S.) and secondary sediment structures (S.S) with associated depth.. ............................95 7 LIST OF FIGURES Figure page 1-1 Map of the Montbrook Fossil Site in Florida. Levy County is subset to illustrate the location of Montbrook as an area of interest in north-central Florida ...............................20 1-2 Faunal reconstruction of Montbrook, October 28, 2019. Courtesy of Rachel Keeffe .......21 1-3 Age distribution of Miocene and Pliocene fossil localities in Florida ...............................22 1-4 Geologic map of Florida modified from Scott et al. (2001) with Neogene fossil localities. Subset illustrates prominent fossil localities in north-central Florida and their proximity to Montbrook. ...........................................................................................23 2-1 Geologic cross-section of Florida from Scott et al. (2001) featuring the north to south transect ...............................................................................................................................61 2-2 Montbrook fossil site overview highlighting the various areas of interest within and around the locality..............................................................................................................62 2-3 Representative outcrop and key geologic features observed from the lower step .............63 2-4 Representative outcrop and key geologic features observed from the upper step .............64 2-5 Correlated lithostratigraphic columns of upper and lower steps based on site description and microfacies analysis where depth is measured in centimeters from the surface ..........................................................................................................................65 2-6 Representative section of rippled sand unit (facies A) ......................................................66 2-7 Representative section of massive gravel unit (facies B) ..................................................67 2-8 Representative section of wavy cross laminate sand unit (facies C) .................................68 2-9 Representative section of heterolithic flaser unit (facies D) ..............................................69 2-10 Feldspar grains observed from smear slide samples in XPL .............................................70 2-11 Heavy mineral grains observed from smear slide samples in PPL ....................................70 2-12 Quartz grains with pyrite framboids observed from smear slide samples in PPL .............71 2-13 Palygorskite observed from smear slide sample in XPL ...................................................71 2-14 SEM images of artifacts that contain needle-like minerals inside their hollowed structures ............................................................................................................................72 2-15 SEM images of microfossils found in situ .........................................................................72 8 2-16 SEM images of preferentially sorted phosphatic-rich grains .............................................73 2-17 FGS sediment core 19731 drilled north of Montbrook ......................................................74 2-18 FGS sediment core 19732 drilled south of Montbrook .....................................................75 2-19 FGS