Abstract
Glacio-eustatic influence on the carbon cycle; chemostratigraphy of cyclothems in the Atokan, Arrow Canyon, Nevada, USA
Abstracts with programs - Geological Society of America, Vol.36(5), p.376
Geological Society of America, 2004 annual meeting
11/2004
Abstract
Previous carbon isotope stratigraphy done on Pennsylvanian-aged rocks has shown a noisy, non-trending delta (super 13) C signal that contrasted sharply with the slightly older Mississippian-aged rocks that showed trends and even excursions. At higher resolution, however, carbon isotope stratigraphy from the Atokan-aged (Pennsylvanian) sequence of carbonates in Arrow Canyon, Nevada shows a pattern that tracks the lithologic sequence. The lithologic pattern, a repetitive, shallowing-upward sequence, is a result of the glacially driven rise and fall of sea level that was occurring repeatedly at the time. The sequence is typified by a deep-water heterozoan faunal association followed by photozoan faunal associations displaying more shoreward lithologies upward in each cycle. The repetition of this type of sequence follows a periodicity calculated to be very close to the estimated length of the obliquity signal of Milankovitch cyclicity during the Mid-Pennsylvanian time. The carbon isotopes (delta (super 13) C) show a shift from deep to shallow water of approximately 1 % (VPDB), but as much as 1.45 %. The lightest isotopic values are recorded in the deepest water and progressively become heavier as the water shallows above the depositional surface in each cycle. For example, in one shallowing-upward cycle the deepest water lithology, a nodular wackestone, recorded a delta (super 13) C value of 2.50 %, shifting gradually through the cycle to record a value of 3.95 % in a lagoonal wackestone. There are several factors that contribute to the values seen through the cycles. One factor is the local circulation patterns inherent of being in shallow water on a very wide platform, as these rocks were when deposited. Another factor is the global carbon cycle. Lastly, orbital variation clearly plays a role in driving our delta (super 13) C values.
Details
- Title: Subtitle
- Glacio-eustatic influence on the carbon cycle; chemostratigraphy of cyclothems in the Atokan, Arrow Canyon, Nevada, USA
- Creators
- Kate E Tierney - Ohio State University, Department of Geological Sciences Columbus, OH USA United StatesMatthew R Saltzman
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.36(5), p.376
- Conference
- Geological Society of America, 2004 annual meeting
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, 2004 annual meeting
- Language
- English
- Date published
- 11/2004
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240794902771
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