Oldest Dryas - Dating

Dating

The dates of this period are approximately 18,000-15,000 BP, from Roberts, 1998. A date from Kilkeel, Northern Ireland, extends the start of the period to as early as 19,000 BP. 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 14,650 BP 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.

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 19,000 BP, 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.