The NSS Bulletin - ISSN 1090-6924
Volume 41 Number 3: 102-104 - July 1979

A publication of the National Speleological Society

U-Series Dating of Speleothems and A-Glacial Chronology for Western North America
Russell S. Harmon


230Th/234U ages for calcite speleothems from four alpine karst areas of western North America cluster into four disinct groups. Attributing periods of speleothem deposition to interglacial or interstadial episodes and vice-versa, times of warm climate in western North America are observed at about 320,000 to 280,000 years BP, 220,000 to 180,00 years BP, 155,000 to 99,000 years BP, and from 10,000 years BP to the present.

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