Paleo- and environmental magnetic studies of Late Cenozoic estuarine, lacustrine, and terrestrial sediments

Clifford William Heil, University of Rhode Island

Abstract

Magnetic studies of sedimentary records provide an opportunity to characterize both anthropogenic and naturally-induced climate change and place these changes in a temporal framework in order to understand the timing of these changes and potential forcing mechanisms. The focus of this dissertation is the use of paleomagnetism and environmental magnetism in different environments (estuarine, lacustrine, and terrestrial), that span thousands to millions of years, to characterize changes in depositional environment overtime, identify the mechanisms responsible for those changes, constrain them within the geologic time scale, and ultimately relate those changes to regional and/or global climate. ^ The Chesapeake Bay is a drowned river valley estuary formed by the flooding of the Susquehanna River and adjacent coastal plains during post-glacial sea-level rise. The magnetic properties of several cores from the axial channel and shallow flanks record the inundation process by identifying changes in erosion and deposition. In addition to these natural changes, European settlement within the watershed and adjacent coastline increased sedimentation in the bay by exposing surface and subsurface soils to erosion through deforestation and cultivation. ^ A paleo- and environmental magnetic record from Bear Lake (Idaho-Utah) details changes in the hydrological balance of the lake over several glacial and interglacial cycles. Millennial-scale variations in the abundance of Fe-oxides (similar in timing to North Atlantic Dansgaard-Oeschger oscillations) suggest a relationship between the size of the Laurentide ice sheet, the position of the polar jet stream, and glacial advances in the Uinta Mountains. ^ The magnetic record from Gorina Quarry of the Buenos Aires Province of Argentina shows a series pedogenic complexes formed during several periods of soil formation and loess deposition. Variations in the amount of goethite and hematite, in conjunction with the amount of ultrafine-grained magnetic minerals, indicate different soil forming regimes relating to moisture availability. Based on a magnetic reversal stratigraphy, the environmental magnetic record indicates relatively and conditions between 1.1-1.9 Ma with an increase in available moisture between 0.5-1.1 Ma and the onset of soil gleying after 0.5 Ma. ^

Subject Area

Geology

Recommended Citation

Clifford William Heil, "Paleo- and environmental magnetic studies of Late Cenozoic estuarine, lacustrine, and terrestrial sediments" (2008). Dissertations and Master's Theses (Campus Access). Paper AAI3314457.
http://digitalcommons.uri.edu/dissertations/AAI3314457

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