2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM
Paper No. 209-5
Presentation Time: 3:05 PM-3:20 PM

Is An Orbitally Tuned Paleozoic Timescale Achievable?

CRAMER, Bradley D., School of Earth Sciences, Division of Geological Sciences, The Ohio State University, 125 S. Oval Mall, Columbus, OH 43210, cramer.70@osu.edu, MEYERS, Stephen R., Geological Sciences, University of North Carolina at Chapel Hill, 213 Mitchell Hall, CB # 3315, Chapel Hill, NC 27599-3315, MUNNECKE, Axel, GeoZentrum Nordbayern, Fachgruppe Paläoumwelt, Universität Erlangen, Loewenichstrasse 28, Erlangen, D-91054, Germany, and JEPPSSON, Lennart, Department of Geology, GeoBiosphere Science Centre, Lund University, Sölvegatan 12, Lund, SE-223-62, Sweden

Astrochronology has revolutionized Cenozoic chronostratigraphy, and is gradually being applied to older parts of the geologic timescale, however there are a number of substantial challenges that have limited the utility of this method for refining Paleozoic chronostratigraphy. First, the lack of deep-sea cores containing Paleozoic strata makes intercontinental correlation and global chronostratigraphy significantly more complicated than working in younger eras. Paleontological endemism, an incomplete epicontinental record, regional biological and lithological terminology (“state-line faults”), and a lack of integration between fields have all hindered Paleozoic efforts towards high-resolution chronostratigraphy. Second, the lack of sufficient radiometric data to reliably calibrate observed stratigraphic rhythms to temporal periods has served as a major obstacle to the development of accurate orbital time scales.

Detailed biostratigraphic and carbon isotopic data amassed from European and North American study sites demonstrates that high-resolution global correlations are now clearly within reach for portions of the Silurian. In addition, the recent development of an inverse method for quantitative identification and calibration of orbital signals preserved in the rock record (Average Spectral Misfit, or ASM) overcomes the second major challenge of insufficient radiometric data. Here we present the results of ASM analysis of a high-resolution δ13Ccarb data set from the Silurian Visby Formation in Gotland (Sweden) that captures the onset of the early Sheinwoodian (Ireviken) positive carbon isotope excursion. Our analysis indicates that the null hypothesis (no orbital signal) can be rejected with a high degree of confidence (<0.2% probability) and provides the first segment of an orbitally-tuned Silurian timescale demonstrating that, although difficult and replete with challenges unique to the era, an orbitally-tuned Paleozoic timescale is indeed achievable.

2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM
General Information for this Meeting
Session No. 209
The Astronomically Forced Sedimentary Record: From Geologic Time Scales to Lunar-Tidal History
George R. Brown Convention Center: 361DE
1:30 PM-5:30 PM, Monday, 6 October 2008

Geological Society of America Abstracts with Programs, Vol. 40, No. 6, p. 283

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