A Younger Dryas Icecap in the Equatorial Andes

• Published in: Quaternary Research
• Main Authors: Clapperton, Chalmers M., Hall, Minard, Mothes, Patricia, Hole, Malcolm J., Still, John W., Helmens, Karin F., Kuhry, Peter, Gemmell, Alastair M.D.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1997
• Subjects: General Earth and Planetary Sciences; Earth-Surface Processes; Arts and Humanities (miscellaneous); Ice cap; North Atlantic
• Online Access: http://dx.doi.org/10.1006/qres.1996.1861; http://api.elsevier.com/content/article/PII:S003358949691861X?httpAccept=text/xml; http://api.elsevier.com/content/article/PII:S003358949691861X?httpAccept=text/plain; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033589400038515

Abstract Morphologic and stratigraphic evidence shows that a late-glacial ice cap existed on part of the Eastern Cordillera of Ecuador (Lat. 0° 20′ S) on ground with a mean elevation of 4200 m where none exists now. An outlet glacier from an ca. 800 km 2 ice cap terminated at 3850 m altitude in the Papallacta valley on the eastern side of the plateau. Radiocarbon dates show that moraines formed by this advance were ice-free by 13,200 14 C yr B.P. Tephras and the age of organic deposits at the plateau edge indicate ice-free conditions before 11,800 14 C yr B.P. This interval was followed by the expansion of an ca. 140 km 2 ice cap that discharged glaciers into adjacent valleys where terminal moraines were built at 3950 m altitude. AMS and conventional radiocarbon dates from macrofossils, peat, and gyttja above and below till of the readvance indicate that the ice cap formed between ca. 11,000 and 10,000 14 C yr B.P. and was thus coeval with the European Younger Dryas event. The ice cap developed in response to a surface temperature cooling of at least 3°C in the tropical Andes, a finding that is consistent with a coupled equatorial/high latitude North Atlantic climate system operating at the late-glacial/Holocene transition. These results are further evidence that Younger Dryas cooling may have been a global event.