Some Problems Concerning the Late Quaternary History of the Southern Chilean Lake District and New Zealand

Abstract

Few regions are better suited to glacial chronology and related studies than Southern Chile and New Zealand because of their wealthy occurrence of glacial deposits, marine terraces, tephras, loess deposits and associated materials available for chronological study. This paper gives a short review of problems in these regions that are closely related to the studies of the Japanese Quaternary.
The fluctuations in the Chilean piedmont glaciers during the Last Major Glaciation seem to have kept closely in step with those of the New Zealand glaciers. Two major periods of glacial advance are simultaneously recorded in both regions. In the early stade, glaciers reached their maximum extent mostly before 45, 000 YBP, although the exact ages have not yet been determined. After a long interstade with intercalations representing a minor readvance, the late stade followed, to be ended by a readvance culminating at about 20, 000 YBP. The fact that the maximum advance of glaciers in both regions occurred in the early stade of the last Glaciation probably resulting in maximum lowering of the sea level, should be significant for interpreting the following topics of Late Quaternary in Japan: 1) Occurrence of the older moraines at somewhat lower altitudes than the younger ones at several places in the Japanese high mountains. 2) Formation of a land bridge between the Japanese islands and the continent more than 30, 000 years ago estimated from archeological data.
Climatically-controlled terraces are clearly defined in the high latitudes of each region where fluctuations in the glaciers greatly affected the river regimes. In contrast, it is suggested that river terraces of climatogenic origin decrease in occurrence in the relatively lower latitudes since Japan lacked any extensive cover of glaciers in the Ice Ages.
Tephrochronology plays an important role in Quaternay studies both in the North Island of New Zealand and in Southern Chile. The widespread Late Quaternary tephras of New Zealand are mostly rhyolitic in composition, but those of Chile are less numerous due to the broad development of andesitic or basaltic types.