Aerial view of one of my many field locations in southwest Wyoming.

Research

Figure 1:  Basemap: Paleogeographic map (51 Ma) showing locations of principal Laramide uplifts, Eocene paleocatchment of the Greater Green River basin, Cheyenne belt, areas of evaporite accumulation, paleodrainage paths and sample localities for this study. Geologic map: Geologic map of field area showing path of Aspen paleo-River and detrital zircon sample locations by chronofacies.

Figure 1:

Basemap: Paleogeographic map (51 Ma) showing locations of principal Laramide uplifts, Eocene paleocatchment of the Greater Green River basin, Cheyenne belt, areas of evaporite accumulation, paleodrainage paths and sample localities for this study.
Geologic map: Geologic map of field area showing path of Aspen paleo-River and detrital zircon sample locations by chronofacies.

I recently earned a Master's Degree and am currently pursuing a PhD degree in geology at the University of Wisconsin. My research is focused on fluvial sedimentology, paleoclimate, geochronology and science communication-especially with visual media. My M.S. Thesis sought to track a paleo-river flowing out of central Colorado in the early Eocene (~55 Ma) and into southwestern Wyoming. At that time southwestern WY was covered by a large lake basin in many ways similar to the Great Salt Lake in Utah today. The significance of a drainage system from central CO into WY at this time, other than being really cool, is that in the early Eocene central CO was in fact an area of active volcanism. This is important because one of the most economically valuable minerals found in the Green River Formation (GRF) of southwest WY (deposited by Eocene Lake Gosuite) is sodium bicarbonate, or trona. We use sodium bicarbonate in a myriad of ways including everything from the production of glass to cleaning agents and cosmetics. Despite our industrial appreciate for the mineral, however, we're still unsure as to why we find it in the GRF in the first place. Specifically, we’re baffled by the source of alkalinity to the parent waters that were responsible for precipitating trona in the early Eocene.
My M.S. research offers a potential solution to this question. Namely, we hypothesize that a river system (the Aspen paleo-River) sourced in the volcanically active Colorado Mineral Belt (CMB) that flowed into southwest WY in the early Eocene could provide the requisite alkalinity for the formation of trona. To test this hypothesis, I employed detrital zircon analysis to ascertain the ages of the fluvial (river-deposited) sandstones found along the proposed flow-path of the Aspen paleo-River and along the periphery of the GRF lacustrine (lake-deposited) sediments in southwestern WY. By dating the age of individual zircon grains in the sands I can compare those ages to ages of potential source areas from which they may have originated—like the CMB. In combination with detrital zircon geochronology, I employed sandstone petrography and paleocurrent analysis to ultimately tell the story of the Apsen paleo-River.

Publications

Hammond, A. P., Carroll, A. R., Parrish, E. C., Smith, M. E., & Lowenstein, T. K. (2019). The Aspen paleoriver: Linking Eocene magmatism to the world’s largest Na-carbonate evaporite (Wyoming, USA). Geology. https://doi.org/10.1130/g46419.1

Aerial view of a km-scale syncline in SW Wyoming.

Aerial view of a km-scale syncline in SW Wyoming.