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Detrital-Zircon Geochronologic Provenance Analyses That Test and Expand the East Siberia - West Laurentia Rodinia Reconstruction

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Detrital-Zircon Geochronologic Provenance Analyses That Test and Expand the East Siberia - West Laurentia Rodinia Reconstruction University of Montana ScholarWorks at University of Montana Graduate Student Theses, Dissertations, & Professional Papers Graduate School 2007 DETRITAL-ZIRCON GEOCHRONOLOGIC PROVENANCE ANALYSES THAT TEST AND EXPAND THE EAST SIBERIA - WEST LAURENTIA RODINIA RECONSTRUCTION John Stuart MacLean The University of Montana Follow this and additional works at: https://scholarworks.umt.edu/etd Let us know how access to this document benefits ou.y Recommended Citation MacLean, John Stuart, "DETRITAL-ZIRCON GEOCHRONOLOGIC PROVENANCE ANALYSES THAT TEST AND EXPAND THE EAST SIBERIA - WEST LAURENTIA RODINIA RECONSTRUCTION" (2007). Graduate Student Theses, Dissertations, & Professional Papers. 1216. https://scholarworks.umt.edu/etd/1216 This Dissertation is brought to you for free and open access by the Graduate School at ScholarWorks at University of Montana. It has been accepted for inclusion in Graduate Student Theses, Dissertations, & Professional Papers by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. DETRITAL-ZIRCON GEOCHRONOLOGIC PROVENANCE ANALYSES THAT TEST AND EXPAND THE EAST SIBERIA – WEST LAURENTIA RODINIA RECONSTRUCTION By John Stuart MacLean Bachelor of Science in Geology, Furman University, Greenville, SC, 2001 Master of Science in Geology, Syracuse University, Syracuse, NY, 2004 Dissertation presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Geosciences The University of Montana Missoula, MT Spring, 2007 Approved by: Dr. David A. Strobel, Dean Graduate School Dr. James W. Sears, Chair Department of Geosciences Dr. Julie A. Baldwin Department of Geosciences Dr. Kevin R. Chamberlain Department of Geology and Geophysics, University of Wyoming Dr. David B. Friend Department of Physics and Astronomy Dr. Marc S. Hendrix Department of Geosciences MacLean, John, Ph.D., Spring 2007 Geosciences Detrital-zircon geochronologic provenance analyses that test and expand the East Siberia – West Laurentia Rodinia reconstruction Chairperson: Dr. James W. Sears Laurentia’s position in the Neoproterozoic supercontinent Rodinia is a topic of continuing debate. Several reconstructions involving Laurentia and Siberia have been proposed, including the east Siberia-west Laurentia connection. The east Siberia-west Laurentia Rodinia reconstruction includes lithostratigraphic correlations of conjugate rift miogeocline sediments located in SE Siberia and SW Laurentia. To constrain provenance relationships and to quantitatively test correlations, we determined detrital- zircon age spectra from samples from the Sette Daban Range of SE Siberia and the Death Valley and White-Inyo regions of SW Laurentia using SHRIMP and LAICPMS. Data indicate that several Siberian samples contain zircons correlative with Laurentian sources, and several Laurentian samples contain zircons correlative with Siberian sources. The results not only strengthen correlations between the two successions, they also lead to a new tectono-sedimentary evolution model of the restored region. The new model involves thickening of the crust during the southern Laurentian Grenville orogeny, crustal flexure resulting in a foreland basin, and extension sub-perpendicular to the Grenville front resulting in extensional basins within the foreland basin on both cratons. Sediments were transported from the Grenville Orogen across the margin between the two cratons and were preserved in the extensional basins. The Grenville source for SE Siberian sediments was cut off in the latest Proterozoic due to successful continental rifting. Grenville sediments were cut off from SW Laurentia in the latest Proterozoic- Middle Cambrian either due to the development of an impediment between the orogen and the basin, or due to the transgression of the Cambrian Sea from the east. Petrographic analyses corroborate the new tectono-sedimentary model. My research resulted in other avenues of thought that were not anticipated from the outset. For example, I present a comparison of the age-equivalency of SHRIMP and LAICPMS detrital-zircon analyses obtained by analyzing the same zircon grains with both instruments. Also, I show that a possible extension of the East Siberia – West Laurentia connection could be the Anti-Atlas region of Morocco, based on trilobite evidence and detrital-zircon provenance information. Finally, I demonstrate two ways to involve K-12 students in geoscience research. ii ACKNOWLEDGMENTS Foremost, I thank my wife, Michelle Kotler, for encouraging and supporting me through this process. She inspired me to pursue science with excitement, not just awareness, and she continues to make my life more interesting than I could have ever hoped for. I also thank my entire family for instilling in me a work capacity necessary for such an endeavor as pursuing this degree, and for supporting and loving me constantly. I shouldn’t leave out the dogs in my life, The Great Jane, Merlin “Bubba” Kotler, the late Richard Parker (RP) and the late Mr. Wayne. And Macky, I’ll never forget that you were perfect. It is a lonelier world without you. I thank the Missoula ultimate community for providing a much-needed escape from reality. I will always cherish memories of the Mental Toss Flycoons realizing our goals in the Fall of 2006. I thank my graduate committee and those who influenced my academic experience. Julie Baldwin, Marc Hendrix, and Don Hyndman were available and willing to help whenever needed. Kevin Chamberlain was especially generous with his time, effort, and funding regarding the geochronology aspects of this research. David Friend also generously gave his time to serve on a project somewhat out of his expertise. Carol Brewer, Paul Alaback, and the rest of the ECOS community were instrumental in my development as a science educator. Finally, I thank Jim Sears. Besides my father, no man has ever positively influenced my life more than Jim. Least importantly, he has shown me new ways to think about how the world works. Most importantly, he has been an example of a husband, father, colleague, and friend that I will always strive to emulate. iii PREFACE The SE Siberian taiga and the SW North American desert represent vastly different environments on opposite sides of the world, yet they may have been joined during Precambrian time. Researchers agree that the Proterozoic supercontinent Rodinia broke up during latest Proterozoic to Cambrian time. However, the positions of the continents within Rodinia are debated. In particular, much disagreement has focused on which continent was opposite the western margin of proto-North America (Laurentia). Likewise, researchers have proposed several models of Siberia’s position relative to Laurentia. Sears and Price (1978, 2003) have been the strongest proponents of juxtaposing E Siberia and W Laurentia in the Rodinia reconstruction. Their model is based on several lines of evidence, including the fit of the continents when structurally restored to their Proterozoic nature, numerous magmatic and orogenic belts that seamlessly cross the proposed margin between the two continents, supportive paleomagnetic data, and correlative conjugate rift miogeocline sediments. The details of the reconstruction are described in Chapters 1 and 2 in greater detail. The focus of my research has concerned the Proterozoic-Cambrian miogeoclinal sedimentary correlations between the Sette Daban region, SE Siberia, and the Great Basin region, SW North America. In a field excursion to SE Siberia during the summer before my program began, Sears and his colleagues identified numerous lithostratigraphic similarities between Siberian sedimentary rocks and their correlatives observed in the White-Inyo, Death Valley, and Grand Canyon regions. My research involved quantitatively testing these comparisons with detrital-zircon geochronology analyses using Sensitive High Resolution Ion Microprobe (SHRIMP) and Laser Ablation Inductively Coupled Plasma (LAICPMS) techniques. In Chapter 1, I report the results of these tests, finding that Siberian samples contain zircons from Laurentian sources, and that Laurentian samples contain zircons from Siberian sources. iv By accepting that East Siberia and West Laurentia were likely connected during Proterozoic time, further interpretations involving regional tectonic and sedimentation histories can be made by incorporating both continents’ geologic evidence. In Chapter 2, I consider samples collected from Siberia and Laurentia, analyzed by several independent detrital-zircon geochronology laboratories, and reported in the literature over the past ten years. The result is a new tectono-sedimentary model that proposes that the Grenville orogen supplied sediment to the SE Siberia – SW Laurentia region during the Proterozoic, and that subsequently both SE Siberia and SW Laurentia were cut off from the Grenville sediment supply during latest Proterozoic – Middle Cambrian time. In Chapter 3, I add petrographic support to this model and provide an example of how to involve K-12 students in authentic scientific research. Chapter 4 summarizes the detrital-zircon data supporting the E Siberia – W Laurentia connection and introduces compelling paleontology evidence for Cambrian proximity of the two continents. An unanticipated result of the research postulates a possible addition of the Anti-Atlas region of Morocco to the East Siberia – West Laurentia reconstruction, discussed in Chapter 5. Placing the Anti-Atlas region close to the E Siberia – W Laurentia
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