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DETRITAL-ZIRCON GEOCHRONOLOGIC PROVENANCE ANALYSES THAT TEST AND EXPAND THE EAST SIBERIA - WEST LAURENTIA RODINIA RECONSTRUCTION

by MacLean, John Stuart

Abstract (Summary)
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.
Bibliographical Information:

Advisor:James W. Sears

School:The University of Montana

School Location:USA - Montana

Source Type:Master's Thesis

Keywords:geology

ISBN:

Date of Publication:07/12/2007

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