Isotopic age dating

Posted by / 18-Jun-2017 20:45

Isotopic age dating

GSSPs are generally, but not always, based on paleontological changes.

The proposed section for the Pleistocene is the North Greenland Ice Core Project ice core (75°06′N 42°18′W) (Svensson et al. The Global Boundary Stratotype Section and Point for the start of the Pleistocene is in a reference section at Vrica, 4 kilometers south of Crotone in Calabria, southern Italy, a location whose exact dating has recently been confirmed by analysis of strontium and oxygen isotopes, as well as by planktonic foraminifera.

It is estimated that, at maximum glacial extent, 30 percent of the Earth's surface was covered by ice.

In addition, a zone of permafrost stretched southward from the edge of the glacial sheet, a few hundred kilometers in North America, and several hundred in Eurasia.

Glaciers existed in the mountains of Ethiopia and to the west in the Atlas mountains.

In the northern hemisphere, many glaciers fused into one.

The Pleistocene has been dated from 1.806 million (±5,000 years) to 11,550 years before present (Lourens et al.

The continuous climatic history from the Pliocene into the Pleistocene and Holocene was one reason for the International Commission on Stratigraphy to propose discontinuance of the use of the term "Quaternary." This proposal was strongly objected to by the International Union for Quaternary Research (INQUA).

The Cordilleran ice sheet covered the North American northwest; the east was covered by the Laurentide.

The Fenno-Scandian ice sheet rested on north Europe, including Great Britain; the Alpine ice sheet on the Alps.

The International Commission on Stratigraphy (a body of the International Union of Geological Sciences) is in agreement with the time period for the Pleistocene, but has not yet confirmed a Global Boundary Stratotype Section and Point (GSSP) for the Pleistocene/Holocene boundary.

A GSSP is an internationally agreed upon section of the geologic strata that serves as the reference section for a particular boundary on the geologic time scale.

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The epoch was intended to cover the recent period of repeated glaciations; however, the start was set too late and some early cooling and glaciation are now believed to be in the Gelasian stage at end of the Pliocene.