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.

ordovician dating-58

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.