Author ORCID Identifier

https://orcid.org/0009-0008-2434-359X

Date Available

1-25-2024

Year of Publication

2024

Degree Name

Master of Science (MS)

Document Type

Master's Thesis

College

Arts and Sciences

Department/School/Program

Earth and Environmental Sciences (Geology)

First Advisor

Dr. Michael M. McGlue

Abstract

This study utilizes a recently acquired, high-resolution CHIRP seismic reflection dataset and a deepwater sediment core to analyze the recent stratigraphy of Jackson Lake (Wyoming, USA). The western shoreline of Jackson Lake is situated adjacent to the Teton fault, a down-to-the-east normal fault that produces the spectacular high topography of Grand Teton National Park. The sediments of Jackson Lake are underexplored and consequently, their value as indicators of hydroclimatic and tectonic changes is unknown. Here, the sedimentary fill of Jackson Lake is explored as a natural archive of environmental change, specifically in reference to the influence of human outlet engineering (dam installation) on the lake. This study developed new bathymetric, acoustic basement, isopach, and facies maps from seismic reflection profiles in order to illustrate the modern distribution of available accommodation, sedimentary depocenters, and features of the sublacustrine geomorphology. Major faults were mapped by identifying offset basement reflectors, and acoustic facies were characterized based on external geometry and internal characteristics of reflections. A major finding in the shallow seismic data were several prograding clinoforms; these features appear to reflect processes associated with lake level transgression due to installation of the dam, which resulted in the flooding of deltas. The northern axis of Jackson Lake displays high amplitude, parallel, semi-continuous lake floor reflections interpreted as flooded Snake River delta plain deposits, whereas low amplitude, continuous reflections in the basin center are interpreted to be hemipelagic lacustrine sediments. Evidence of glaciation is also present in the seismic dataset; mound-shaped acoustic geometries with limited penetration are interpreted as submerged drumlins or moraines. A short sediment core, dated with 210Pb, 137Cs, and 14C, serves as ground truth for the shallowest seismic reflectors in the basin’s primary depocenter, and provides initial insights into deepwater sedimentation rates. The geochronological data indicate that the core encompasses ~365 years from ~1654 to 2019 CE, and an acceleration in sediment accumulation may have resulted from dam installation. This research will help to guide future long sediment coring, which is needed in order to establish the long-term depositional history of the basin.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2024.17

Funding Information

This study was supported by the American Association for Petroleum Geologist in 2019.

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