Carbon isotope stratigraphy of early Eocene hyperthermals in the Bighorn Basin, Wyoming, USA: analogues for modern anthropogenic carbon emissions

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Title Carbon isotope stratigraphy of early Eocene hyperthermals in the Bighorn Basin, Wyoming, USA: analogues for modern anthropogenic carbon emissions
Publication Type thesis
School or College College of Mines & Earth Sciences
Department Geology & Geophysics
Author Maibauer, Bianca Jean
Date 2013-12
Description Paleoclimate records indicate that the early Cenozoic Era was punctuated by several abrupt, transient hyperthermal events, most notably the Paleocene-Eocene Thermal Maximum (PETM, ca. 55.5 Ma) and the Eocene Thermal Maximum 2 (ETM2, ca. 53.6 Ma). These abrupt warming events occur coeval to a significant perturbation to the global carbon cycle. Although the timing and magnitude of these ancient hyperthermal events were similar to projected future changes associated with anthropogenic carbon emissions, the application of these events as analogues to anthropogenic global change is complicated by widely divergent interpretations of the rate, patterns, and sources of carbon release. Recently drilled scientific cores that span these hyperthermals were collected at three terrestrial sites from the Bighorn Basin, Wyoming, USA. Pedogenic carbonate isotope data from the Gilmore Hill (GMH) site exhibit relatively stable background δ13C and δ18O values over a host of multicolored floodplain lithologies but lack the expected >2‰ shift of the ETM2 carbon isotope excursion (CIE). Bulk sedimentary organic matter at Basin Substation (BSN) reveals a dramatic decrease in total organic carbon (TOC) preservation through the estimated PETM interval while δ13C values are variable and lack the expected >2‰ PETM CIE. High-resolution carbon isotope data from Polecat Bench (PCB) pedogenic carbonate show that the PETM is characterized by a sustained >5‰ negative CIE, and the onset of this event is characterized by two massive releases of between 600 and 10,000 gigatons of carbon (Gt C), each occurring in one thousand years or less. We hypothesize that the ETM2 interval is located within poorly cemented, highly weathered sands that characterize the upper 25 m of core at GMH and may represent a climatic response to the warming event. The variability and lack of discernible CIE in our BSN δ13C record suggests that additional external mechanisms, such as water stress or organic matter source, likely impacted the preserved TOC. The PCB record, however, shows volatile behavior in Earth's carbon cycle leading up to initiation of the PETM and indicates that the PETM is a strong analogue to current and future carbon cycle perturbation in both magnitude and rate of change.
Type Text
Publisher University of Utah
Subject Carbon isotopes, Paleocene-Eocene thermal maximum; Pedogenic carbonate; Soil organic matter
Dissertation Institution University of Utah
Dissertation Name Master of Science in Geology
Language eng
Rights Management Copyright © Bianca Jean Maibauer 2013
Format application/pdf
Format Medium application/pdf
Format Extent 3,960,122 Bytes
Identifier etd3/id/3480
ARK ark:/87278/s6rv3wzd
Setname ir_etd
ID 197034
Reference URL https://collections.lib.utah.edu/ark:/87278/s6rv3wzd
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