Abstract
A number of glacial moraines are distributed from the eastern margin of the Torres del Paine drainage basin to near the present margin of the Patagonian Ice Fields, together with a set of regionally continuous lacustrine terraces related to glacial fluctuations. The geomorphology, supported by lake sediment evidence, indicates the existence of a single proglacial paleolake in this area, here referred to as the Great Tehuelche Paleolake. This concept helps to clarify the chronology of glacial events and leads to a better understanding of the evolution of the hydrologic system in the Torres del Paine area. Glacial advances previously referred to as A, B and C occurred during the Last Glacial Maximum and fed the Great Tehuelche Paleolake with meltwater, allowing it to reach its maximum extension. The discovery of thrombolites at Laguna Amarga suggests that the drainage of the paleolake towards the ultima Esperanza Fjord took place at 7,113 Cal. yr BP, after the melting of an ice barrier that existed during the earlier glacial advance. This gave rise to the development of a complex fluvio-lacustrine hydrologic system that persists to the present day.
Highlights
Milankovitch (1930) was the first to calculate the combined influence of the eccentricity (100,000 and 413,000 yr cycles), obliquity (41,000 yrs) and precession of the equinoxes (23,000 yrs) on the amount of solar heat recorded at different latitudes during the last million years
A number of glacial moraines are distributed from the eastern margin of the Torres del Paine drainage basin to near the present margin of the Patagonian Ice Fields, together with a set of regionally continuous lacustrine terraces related to glacial fluctuations
In ice cores obtained from Antarctica (EPICA, 2004) and Greenland (North Greenland Ice Core Project, 2004) it is possible to observe these cycles as predicted by the orbital theory
Summary
Milankovitch (1930) was the first to calculate the combined influence of the eccentricity (100,000 and 413,000 yr cycles), obliquity (41,000 yrs) and precession of the equinoxes (23,000 yrs) on the amount of solar heat recorded at different latitudes during the last million years. Studies of stable oxygen isotopes of foraminifers preserved in sediment samples from the Indian Ocean suggest that climatic variations causing the retreat of the ice caps and a rising of sea level are supported by the orbital theory of Milankovitch (Imbrie et al, 1984). In the ice cores short, irregular and abrupt interglacial stadia that cannot be explained by the orbital theory are recorded. These short stadia are of almost the same magnitude as those related to glacial or interglacial periods at a 100,000 yr scale, but represent intervals of only hundreds of years (Dansgaard et al, 1993)
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