NEW STRUCTURAL, STRATIGRAPHIC, AND GEOCHRONOLOGIC CONSTRAINTS FROM NORTHEASTERN WASHINGTON WITH IMPLICATIONS FOR THE NEOPROTEROZOIC RIFTING OF RODINIA

The rifting of the hypothesized Proterozoic supercontinent, Rodinia, beginning ~800 million years ago, has been implicated as a causal factor for global mantle reorganization, initiation of global glaciation, and a second rise of oxygen levels. However, uncertainties in Rodinia’s geography and rift history hinder the rigorous evaluation of such causal links. Here we report new structural, stratigraphic, and geochronologic results from the Windermere Supergroup (Shedroof Conglomerate, Leola Volcanics, and Monk Formation) of eastern Washington state. New mapping and field observations highlight a previously unrecognized thrust fault and amend previous interpretations for locations of and displacements along syn-depositional structures. With a refined understanding of regional fault blocks, we present new stratigraphic findings including the varied eruptive dynamics of extensive Leola volcanics interfingering with diamictites and a subdivision of the Monk formation into upper and lower members. Finally, our U-Pb geochronologic data place radioisotopic tie points on the regional Neoproterozoic units, improving correlation of these units with others along the Cordilleran margin. With this record, we evaluate hypotheses of supercontinent breakup that are fundamental to our understanding of solid Earth-biosphere-climate interactions.