August 13, 2020 “Luncheon” Webinar- Dr. Ryan Sincavage

The long and winding road: A synopsis of the Miocene-present interactions of the Brahmaputra River with climate and tectonics

Dr. Ryan Sincavage, Assistant Professor, Geology Department, Radford University, Radford, VA.

The Ganges-Brahmaputra delta in Bangladesh is the world’s largest, and is home to the world’s most densely populated nation. Understanding the dynamics of this delta is crucial to the lives and livelihoods of the people living in the region, as they are at risk of inundation from both monsoonal rainfall and sea-level rise on its low-lying coast, seismic hazards from a complex tectonic setting, subsidence from coastal land use modifications and groundwater extraction, and natural arsenic sources in their water supply. Recent investigations of this source-to-sink system across spatial and temporal scales have yielded important insights into the autogenic and allogenic drivers of this extraordinary system. While sometimes confounding, the behavior of the river has been revealed through detailed stratigraphic study, analysis of sediment cores both onshore and offshore, multi-channel seismic surveys, geochemical and detrital tracers of provenance, and simple numerical modeling. Highlights from research efforts over the past half-decade are presented here, with an emphasis on the linkages between tectonics, climate, and fluvial system behavior. Stratigraphic mapping coupled with thermal modeling of sediments in the Indo-Burman Ranges reveal the location of the ancestral Brahmaputra River in the Miocene-Pliocene, before a major avulsion around the rising Shillong Massif, driven by the advancing deformation front of the fold and thrust belt. Weakening monsoon conditions and relatively modest sea-level falls present a hydrologic conundrum: how did an underfit Brahmaputra River create the massive paleovalley floor observed in stratigraphy and seismic data? Megafloods sourced from the Tsangpo Gorge are shown to be capable of shaping the incipient topography on which the delta continues to deposit its sediments. The influence of these scours is evident through major avulsions in the mid-Holocene, when the river avoided the low-lying Sylhet Basin in spite of its tectonic favorability. When the river did attempt to fill this basin with sediments, their dispersion in terms of grain size is found to be predictable using a simple mass extraction model, with remarkable consistency with mass balance approaches across a spectrum of depositional settings worldwide. This region truly is a land of superlatives, and the Ganges-Brahmaputra delta represents an outstanding natural laboratory for coupled tectonic/climate drivers of fluvial system behavior, with implications for carbon storage and global climate change.   

Dr. Ryan Sincavage
Assistant Professor (4th year)
Geology Department
Radford University
Radford, VA, USA

Main research focus: interactions of climate, tectonics, and fluvial system dynamics on river system behavior- what makes rivers go where they go? Specifically, I have been working in southeast Asia on the Ganges-Brahmaputra delta system, the world’s largest. Recent work on the delta includes a Holocene history of river path selection (Basin Research, Sincavage et al., 2018), influence of Holocene megaflood events on stratigraphic architecture (GSA Bulletin, Pickering et al., 2018), mass extraction in a mid-Holocene lobe of the Brahmaputra River (Journal of Geophysical Research-Earth Surface, Sincavage et al., 2019), shallow crustal structure and implications for seismic hazards in the Indo-Burman Ranges (Earth and Planetary Science Letters, Betka et al., 2019), and Miocene-Pliocene paleogeography and provenance of the ancestral Brahmaputra River (Journal of Sedimentary Geology, Sincavage et al., in press). Other research areas include ongoing work in outlet valleys of the Northern Patagonian Ice Field, including novel geochronology methods and Holocene history of glacial lake outburst floods (GLOFs).

Education and experience:
·         Originally from upstate NY (Endicott NY- birthplace of IBM)
·         Undergraduate geology degree from Penn State
·         Masters degree in geology from University of Colorado Boulder (seismic stratigraphy of deepwater Gulf of Mexico)
·         PhD in earth and environmental engineering, Vanderbilt University (Holocene stratigraphy of the Ganges-Brahmaputra delta in Bangladesh)
·         5 years experience in oil and gas industry (geophysicist- seismic data acquisition and processing, Schlumberger)
·         4 years experience in environmental consulting (unexploded ordnance detection, soil and groundwater monitoring, Parsons)
·         5 years as non-tenured instructor at University of Colorado Denver
·         4 years as a lecturer at University of Colorado Boulder
·         4th year as an assistant professor at Radford University
·         3rd year as lecturer for South Dakota School of Mines and Technology summer field camps

Other fun facts:
·         Former part-time ski instructor at Loveland Ski Area in Colorado
·         Trumpet player- performed in the Tournament of Roses parade with the Penn State Marching Blue Band
·         Occasional home brewer (not as often as I would like these days!)
·         10-time marathon finisher