THE HEINRICH AND DANSGAARD-OESCHGER CLIMATIC EVENTS DURING MARINE ISOTOPIC STAGE 3: SEARCHING FOR APPROPRIATE TIMES FOR HUMAN COLONIZATION OF THE AMERICAS

RABASSA, J. O.; PONCE, J.F.

QUATERNARY INTERNATIONAL

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2013 vol. 299 p. 94 - 105

1040-6182

Marine Isotope Stage 3 (MIS 3) was an interstadial stage, a relatively warm climatic period which developed roughly between 60-50 and 30 cal. ka B.P. Several very cold periods, known as Heinrich (H) events, developed during MIS 3, as a result of partial collapse of the North American ice sheet margins, with formation of huge amounts of icebergs which, after melting in more temperate latitudes, would have inundated the North Atlantic Ocean with low salinity waters which would have impeded the reach of the Gulf Stream to the North Atlantic Ocean. Several paleoclimatic moments with relatively warmer conditions, known as the Dansgaard-Oeschger (D-O) events, took place in between the Heinrich events, during MIS 3. These H and D-O cycles would have been very short (perhaps even only around 1 ky each in some cases) and very intense, with mean annual temperatures of ca. 5-8 ºC higher than those active at the Last Glacial Maximum (LGM; ca. 24 cal. ka B.P.). Even though climate was warmer, total melting of the ice sheets did not take place; thus, global sea level was still low enough to allow the persistence of the Beringia land bridge between Siberia and North America, without any interruptions throughout the entire MIS 3. The aim of this paper is to present paleoclimatic and paleogeographic information about MIS 3 and to discuss the most favorable chronology for human displacement through Beringia. At these times, there would have been no coalescence between the Laurentide and Cordilleran ice sheets, thus both the hinterland path from Beringia southwards and the coastal route would have been open and enjoying moderate climate ecosystems, and thus available for humans. In this case, it is now possible to suggest possible moments for human penetration in North America, perhaps between ca. 50 to 28 cal. ka B.P, during one or more D-O events (sometime between D-O 14 and D-O 3 events) throughout MIS 3. Human colonization of the Americas following other routes rather than that of Siberia-Beringia, if they existed, is not taken into consideration in this paper.