Abstract
New Wenlock-Ludlow (Silurian) (super 87) Sr/ (super 86) Sr data and a revised Silurian Sr curve; implications for the Silurian timescale
Abstracts with programs - Geological Society of America, Vol.41(7), p.421
Geological Society of America, 2009 annual meeting
10/2009
Abstract
Recalibrations of the Silurian numerical timescale and improvements to global chronostratigraphic correlation over the past two decades have altered the shape of the Silurian (super 87) Sr/ (super 86) Sr curve significantly. Previously published Silurian Sr composites have shown a generally monotonic increase in the (super 87) Sr/ (super 86) Sr curve throughout the Silurian, however, the current numerical timescale for the Silurian produces a major positive inflection point at the onset of the Ludlow Epoch. Here, we show new biostratigraphically well-constrained brachiopod (super 87) Sr/ (super 86) Sr values from Gotland, Sweden, that confirm the presence of an early Ludlow positive inflection from a single chronostratigraphically well-constrained region. It is tempting to suggest that the inflection toward more radiogenic (super 87) Sr/ (super 86) Sr values near the onset of the Ludlow was the result of increased weathering of old sialic strata during the accretion of Laurentia, Avalonia, and Baltica into the Old Red Continent, however, the present Silurian numerical timescale requires that interpretations of the Silurian (super 87) Sr/ (super 86) Sr curve remain provisional. At present only a handful of radiometric age determinations exist for the Silurian that pass modern analytical scrutiny and are sufficiently chronostratigraphically controlled by biostratigraphy, chemostratigraphy, or any other chronostratigraphic tool. In order to produce a Silurian timescale without an inflection at the onset of the Ludlow, a >12 Myr-long Ludlow Epoch would be required. As currently recognized by the International Commission on Stratigraphy, the Ludlow Epoch is 4.2 Myr-long and the Silurian Period has a total duration of only 27.7 Myr. Therefore, the present data indicate that either the duration of the Ludlow is substantially too short and the Ludlow Epoch accounts for nearly half of the Silurian Period, or that global tectonic and climatic changes combined to produce a significant positive inflection in the Silurian (super 87) Sr/ (super 86) Sr curve that resulted in a positive rate of change in Silurian (super 87) Sr/ (super 86) Sr values more that twice as rapid as the Cenozoic (super 87) Sr/ (super 86) Sr rise.
Details
- Title: Subtitle
- New Wenlock-Ludlow (Silurian) (super 87) Sr/ (super 86) Sr data and a revised Silurian Sr curve; implications for the Silurian timescale
- Creators
- Bradley D Cramer - Ohio State University, School of Earth Sciences, Division of Earth Sciences Columbus, OH USA United StatesAxel MunneckeD. I SchofieldMatthew R SaltzmanKarsten Haase
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.41(7), p.421
- Conference
- Geological Society of America, 2009 annual meeting
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, 2009 annual meeting
- Language
- English
- Date published
- 10/2009
- Academic Unit
- Earth and Environmental Sciences; International Programs; Office Of The Provost
- Record Identifier
- 9984240780202771
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