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Full-Text Articles in Geology
Ediacaran Ocean Redox Evolution, Swapan Kumar Sahoo
Ediacaran Ocean Redox Evolution, Swapan Kumar Sahoo
UNLV Theses, Dissertations, Professional Papers, and Capstones
The relative role that environmental versus intrinsic biological factors played in
shaping the history of life on Earth is a fundamental but unanswered question in the
natural sciences. Most famously, it has been heavily debated if the emergence and
diversification of early animals during the Ediacaran Period (ca. 635–541 Ma) was tied to
a rise in atmospheric-oceanic oxygen levels. Temporally discontinuous geochemical data and patchy fossil record in literature are inadequate to chart the Ediacaran redox history and its causal relationship with the biotic evolution. My PhD study aims for a multiproxy geochemical record within a well-established stratigraphic framework of …
Carbon Isotope Variations Associated With A Middle Ordovician Karstic Unconformity, Patricia Suzanne Williams
Carbon Isotope Variations Associated With A Middle Ordovician Karstic Unconformity, Patricia Suzanne Williams
UNLV Theses, Dissertations, Professional Papers, and Capstones
Large negative carbon isotope (δ13C) excursions have been documented from late Neoproterozoic-Paleozoic successions. These δ13C excursions have been widely used for regional and global stratigraphic correlation, particularly in strata with limited paleontological and radiometric age controls. Recent studies, however, argued that some negative δ13C excursions from stratigraphic record may have been resulted from meteoric/burial diagenesis, which commonly shifts both carbon and oxygen isotopes toward lower values. Testing the diagenetic origin of δ13C excursions in stratigraphic successions without independent stratigraphic framework has been difficult because it evolves into circular arguments about stratigraphic completeness …