​David Moecher (Fulbright Ireland Scholar 2022, Universtiy of Kentucky) will talk on "The Great Reach of the Hot, Giant, Long-Lived Grenville Orogen: Its Influence on the Neoproterozoic to Phanerozoic Clastic Sedimentary Record of Laurentia and Amazonia".

Abstract: The Grenville orogen, formed during assembly of Rodinia, is described as one of Earth’s largest, longest-lived, and hottest orogens. The subsequent exhumation and erosion of the Grenville, starting ca. 1.0 Ga and lasting to ca. 0.6 Ga, generated a clastic wedge deposited by a pancontinental river system that covered Laurentia – the “Great Grenvillian Sedimentation Event” (GGSE) of Rainbird et al. (2012). The clastic wedge was subsequently eroded by the end of the Neoproterozoic during formation of the “Great Unconformity” across Laurentia. The Grenvillian sediments were recycled through multiple Phanerozoic orogenies and by a second pancontinental river system during formation of Pangea. Amazonia is widely proposed as the continent that collided with southeastern Laurentia during the Grenville orogeny and may have experienced ‘spillover’ of sediment derived from the Laurentian Grenville. A new detrital zircon U-Pb dataset from southwestern Brazil, in tandem with published detrital zircon data for Neoproterozoic to modern Amazonian clastic systems, indicates the absence of significant Laurentian Grenville input to Amazonia, i.e., there was no GGSE in Amazonia. Some aspects of the detrital zircon record in Amazonia are consistent with Laurentian input.