Before The Present Research Articles

Geochronology of the Deglacial and Neothermal Ages

This is a review of the chronologies based on varved (annually laminated) sediments and a revision of the estimates of the gaps in the varve data. A Finno-Swedish chronology by Gerard De Geer, Ragner Liden, and Matti Sauramo covers the last 11,600 years. It is based on 650 historical years (A.D. 1300-1950), 380 interpolated years (A.D. 920-1300), and the rest on postglacial and glacial varves. The Salpausselka or Younger Dryas age is dated at 10810-10150 B.P. (before the present, 1950). The marked temperature rise which caused the departure of the ice from Salpausselka II in the Finnish year + 1 or 10150 B.P. is taken as the beginning of the Neothermal (European Postglacial) age. The North American chronology ends during the ice oscillations at Cochrane, south of James Bay. These are correlated with the comparably located Nyland and Salpausselka halts in southern Finland. Thus the drainage of Lake Ojibway and varve Timiskaming no. 2025 are dated at about 11300 B.P., and the Cochrane oscillations at 11300-...