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15 N values. This clearly demonstrates that the data are inherently unreliable as a function of the analytical approach. Although the underlying mechanisms require further research, it is clear the biases represented here across a range of terrestrial and aquatic, modern and ancient or

As a contribution to data for reconstructing the climatic changes on a S-N transect from Antarctica to Bolivia, a glacial-geological study is presented that focuses on the Rio Mendoza valley of the central Andes of Argentina. This valley contains the Cerro Aconcagua (6959 m), the highest peak in the Western Hemisphere. In the Rio Mendoza valley, five Pleistocene drifts and one Holocene drift were distinguished by multiple relative-age criteria. U-series ages of travertine layers and fission-track on glass ages of three tephra layers permit a preliminary chronology. Also, an estimate of the magnitude of the Pleistocene snowline depression was obtained, contributing paleoclimatic information. The moraine sequence in the Argentine flank was compared with that studied by Caviedes (1972) along the Rio Aconcagua on the Chilean side of the Andes. In addition, the Pleistocene glacial sequence in the Rio Mendoza valley was correlated preliminarily with that studied by Espizua (1998) along the Rio Grande valley in the southwest of the Mendoza Province.