Quaternary shelf-slope development in the northern Gulf of Alaska from combined geophysical and geomorphologic analysis

This dissertation follows the hybrid format as defined by the Office of Graduate Studies at the University of New Mexico. The three chapters defined herein were prepared as manuscripts to be submitted for publication in peer reviewed journals in the field of Earth sciences. A version of chapter 1 was published in Proceedings of the Integrated Ocean Drilling Program, 2017, Volume 41. Chapter 2 was submitted to Marine Geology in Feb 2020, and is under revision as of this date. A version of chapter 3 will be submitted to the Journal of Geophysical Research. In chapter 1, I was the lead researcher establishing a time-depth relationship for Integrated Ocean Drilling Program (IODP) Expedition 341 Southern Alaska Margin Sites U1420 and U1421 using high-resolution multichannel seismic, core, and logging data. Results from the core-log-seismic integration significantly contributed to Exp. 341 goals, particularly by providing a quantitative basis to relate borehole observations and regional seismic-stratigraphic interpretations, and led to publications where I was a contributing coauthor in journals including Earth and Planetary Science Letters, and Nature Communications. In Chapter 2 I led an investigation of how the drainage morphology in the northern Gulf of Alaska relates to glacial activity, faults, and large-scale mass movements. I present a multivariable spatial analysis applied to measurements of channel and feature cross-profile shapes, and in the text, the results are interpreted and evaluated with respect to major near-surface geologic features and existing geophysical data. This analysis highlights and quantifies the broad correspondence between ice sheet location and U-shaped features here, and reveals a more focused shape influence attributable to fault location and mass movements in comparison. In Chapter 3 the focus is on the Bering Trough and Pamplona Zone fold-thrust belt. I present models of velocity, porosity, and overpressure developed from the inversion of seismic refraction data and integration of IODP Expedition 341 core-log data. The distribution of overpressure in the Bering Trough region provides an example of climate-tectonic feedback where rapid syntectonic sedimentation in parts of the Pamplona Zone fold-thrust belt is linked to modulation of fault activity by mass redistribution, shelf-slope migration, and slope instability. The text discusses the results in terms of the structural-stratigraphic significance and the history of climate-driven mass redistribution. Together these works help elucidate the effectiveness of glaciomarine processes in forming and reforming the shelf-slope morphology, as well as provide greater detail into competition and cooperation among glaciomarine, climate, and tectonic processes

A multiproxy record of IODP Site 341-U1421

The uncertain response of marine terminating outlet glaciers to climate change at time scales beyond short-term observation limits models of future sea level rise. At temperate tidewater margins, abundant subglacial meltwater forms morainal banks (marine shoals) or ice-contact deltas that reduce water depth, stabilizing grounding lines and slowing or reversing glacial retreat. Here we present a radiocarbon-dated record from Integrated Ocean Drilling Program (IODP) Site U1421 that tracks the terminus of the largest Alaskan Cordilleran Ice Sheet outlet glacier during Last Glacial Maximum climate transitions. Sedimentation rates, ice-rafted debris, and microfossil and biogeochemical proxies, show repeated abrupt collapses and slow advances typical of the tidewater glacier cycle observed in modern systems. When global sea level rise exceeded the local rate of bank building, the cycle of readvances stopped leading to irreversible retreat. These results support theory that suggests sediment dynamics can control tidewater terminus position on an open shelf under temperate conditions delaying climate-driven retreat