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Oldest Dryas


The Oldest Dryas was a climatic period, which occurred during the coldest stadial after the Weichselian glaciation in north Europe. In the Alps, the Oldest Dryas corresponds to the Gschnitz stadial of the Würm glaciation. The three “Dryas” periods (younger, older, oldest) are named for a marker species, Dryas octopetala, detected in core samples of glacial ice and peat bogs. The Oldest Dryas corresponds to pollen zone Ia.

The dates of this period are approximately 16,050-13,050 BC, from Roberts, 1998. A date from Kilkeel, Northern Ireland, extends the start of the period to as early as 17,050 BC. A strong sequence of C-14 dates derived from layered material in the Hauterive/Rouges-Terres excavations on the northwest shore of Lake Neuchâtel in Switzerland, 1992–1993, places the end of the Oldest Dryas at about 12,700 BC calibrated. The same date from Antarctica and the south China sea is 14,600 and 14,700, respectively, while a Greenland ice core indicates 14,500. David Miles refers to the Oldest Dryas as the last Heinrich event (H1), and dates it to between 16,500 and 14,500 years ago.

The ultimate standard to which all these dates are to be compared is the graph of the oxygen isotope ratio cycles, which gives change in isotope concentration on the y-axis versus time on the x-axis. The graph plots many events that are sharply defined, but others are not. The selection of a terminal point is sometimes partially arbitrary.

The end of the Oldest Dryas is sharply defined. The beginning is a long, gently sloping band, probably no earlier than 17,050 BC, but the date might be set later by approximately 1000 years. Data derived from isotope variation of nitrogen and argon trapped in Greenland ice gives a high-resolution date for the end of the oldest Dryas at the sharp temperature rise of 14.67 ky BP.


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