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Isotopic signatures present a wide range of values ( (− 5.53 to − 4.85).The geochemical data are compatible with an orogenic geodynamic environment.For example, originally only five third order sequences were recognized in the type Cincinnatian.
An early phase affecting graptolites, brachiopods, and trilobites occurred prior to the end of the Ordovician Period, before the major fall in .
In many areas the interval of glaciation was accompanied by the invasion of cool-water brachiopod fauna even into tropical latitudes, suggesting the onset of significant global cooling.
This chart represents a work in progress, and should be viewed as a hypothesis to be tested.
The original correlation charts were published in Holland and Patzkowsky (1996), with the Nashville Dome correlations added in Holland and Patzkowsky (1997, 1998). Paleozoic sequence stratigraphy: views from the North American craton.
If you have any comments or questions on these charts, send them to Steven Holland at [email protected] Geological Society of America Special Paper 306, Boulder.
We have numbered the third-order sequences sequentially, and prefix the numbers by the series in which the sequence starts.
This is likely due to high levels of carbon dioxide, which would then produce a greenhouse effect, warming the earth.
This climate change is a proposed reason for the mass extinction at the end of the Ordovician.
Initially, only these two periods existed, until 1979 when Charles Lapworth defined the Ordovician period as a period of it’s own based on fossil fauna that were different from both the Cambrian and the Silurian Period.