40 Ar/ 39 Ar evidence for early deglaciation of the central Chilean Andes
Author(s) -
Singer Brad,
Hildreth Wes,
Vincze Yann
Publication year - 2000
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/1999gl011065
Subject(s) - deglaciation , geology , glacier , glacial period , northern hemisphere , climatology , westerlies , southern hemisphere , cryosphere , physical geography , orbital forcing , oceanography , sea ice , holocene , insolation , geomorphology , geography
Spatial variability of deglaciation and warming since the last glacial maximum is critical for relating hemispheric or regional climate‐forcing mechanisms to global orbitally‐induced insolation changes. Radiocarbon ages of moraines, ice cores, and deep sea sediments from the southern hemisphere suggest that initial warming and glacial recession began before 23,000 years ago, but that in latitudinal belts of concentrated precipitation, glaciers readvanced 18,000 and 13,000 years ago. 40 Ar/ 39 Ar dating of glaciated and unglaciated lava flows 2200 m in elevation at Laguna del Maule, central Chilean Andes, implies that at 36° S, the southern Andean ice cap retreated between 25,600±1,200 and 23,300±600 years ago and did not expand afterwards. These ages are reconciled if increased insolation ablated sea‐ice cover and mountain glaciers in the southern hemisphere 5,000 years before the northern, and if subsequently Laguna del Maule lay north of the westerly winds delivering moisture to more southerly (39–52° S) portions of the ice cap.