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Part 1 Supplementary Papers and Items |
Sub-Department of Quaternary Research, 5 Salisbury Villas, Station Road, Cambridge
OF THE age-determinations listed in this volume as Items, 38 relate to the Pleistocene. Material has been selected on the following basis. Items 367 to 373 comprise determinations of the age of sediment from deep-sea cores; they provide the experimental basis for the dating of the stage boundaries of the marine Pleistocene to about 400 000 years ago. All the evidence at present available suggests that at least the second half of the Pleistocene is represented by deep-sea deposits which can be divided into stages on the basis of the evidence for climatic change. In favourable circumstances successive climatic stages can be distinguished unambiguously on the basis of several independent criteria.
No core has as yet been designated as a type-section in which stages and their boundaries are defined. All the cores discussed here have, however, been divided into stages on the basis of oxygen-isotope analysis; there is good observational evidence that at least over the geographical region covered by the cores under discussion, stage boundaries defined on this basis are essentially synchronous. Theoretical considerations suggest that this is probably true globally. These stages have been designated ‘isotope stages’ (Shackleton, 1969), recognizing that the validity of this basis for defining stage boundaries is not affected by the detailed interpretation of the measurements (that is, it does not matter precisely to what extent they represent temperature changes, and to what extent they portray glacio-isotopic changes in the oceans.)
In view of the fact that climatic changes in the Pleistocene appear to
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This 250-word extract was created in the absence of an abstract.
