Tectonic Setting of Neoproterozoic Environmental Change

The breakup of Rodinia and the emplacement of LIPs at low-latitude has long been portrayed as the tectonic context of Neoprotoerozic climate change.  The interaction of plumes with continental crust may lead not only to changes in weatherability and CO2 consumption, but also to perturbations in the chemical composition of the ocean, including oxidant and nutrient loads, and also to changes in volatile inputs to the atmosphere.  Thus, the construction of a high-resolution tectonic record is necessary to really understand potential links between tectonics and environmental change.  Our geological mapping of Neoproterozoic and Paleozoic strata up and down the Cordillera from Arctic Alaska to southern California has also allowed us to reassess the tectonic evolution of the western margin of Laurentia (which occupied central Rodinia). It has been variously suggested that the basal Windemere Supergroup or the Mackenzie Mountains Supergroup (MMSG) record the rifting of Rodinia.  In Macdonald et al. [30] we demonstrate that the MMSG and correlative strata were accommodated by extension exclusively on the NW margin of Laurentia, and suggest that subsidence was related to the passing of the core of Rodinia (Australia-South China-Laurentia-Siberia) over a long-lived plume, which subsequently produced the Gairdner-Gubei-Gunbarrel-Franklin LIPs. We are currently working with colleagues on a new model for the subsequent tectonic evolution of Rodinia that is consistent with thermal subsidence models.