The Pleistocene

In the years leading up to 1840 the widespread erratics in Alpine and northern Europe were interpreted as deposits of former extensive ice. In 1837 the term Drill came to be used for the widespread sands, gravels and boulder clays newly thought to have been deposited from floating ice. Lyell proposed the Pleistocene Period in 1839 to accommodate this ice age and to post-dale his already established Pliocene. Pliocene was the last period in the Tertiary Era, thus there was room for a post-Pliocene Quaternary division - so named by Morlot in 1854. Quaternary was different from Pleistocene in that it also contained Lyell's original 'Recent', later named Holocciw by the IGC in 1885.

The Pliocene-Pleistocene boundary

An attempt to standardize the initial Pleistocene boundary was made at the IGC in London in 1948 when it was realized that an objective reference in a stratotype near or at the base of Calabrian strata (a stage introduced by Gignoux in 1910) in Italy would be appropriate. The Pliocene-Pleistocene boundary stratotype should be one of the marine sections preserved on land in southern Italy.

Estimates of its age have ranged from 0.6 to 4 Ma (Haq, Bcrggren & Van Couvering 1977). Correlation using palcontological criteria proved difficult. The initial Calabrian boundary was thought to be marked by the first appearance of both Arctica islandica and H valine a ballica (Sibrava 1978) but Ruggieri (INQUA publication in 1979) showed that the latter appears slightly later. Futhermore, Ruggieri argued for the suppression of Calabrian and replacement by Santernian along with a revision of the rest of the sequence, various sections in southern Italy have competed for the position of stereotype. On the basis of calcareous plankton at Le Castella and Santa Maria di Catanzaro as well as of deep-sea sediments, Haq etal (1977) correlated the boundary with the top of or slightly above the Olduvai magnetostratigraphic event at 1.6 Ma.

Division of the Pleistocene Epoch

It seems that no formal decisions have yet been made, but also that an official scheme of stages may not be far off. Competing bipartite and tripartite schemes have been in informal use and it now seems that a tripartite scheme is likely to be favored.

Questionnaire:

• Explain about the Pleistocene