Deep circulation change linked to HEINRICH Event 1 and Younger Dryas in a middepth North Atlantic Core


  • Lloyd D. Keigwin,

  • Scott J. Lehman


A core from the Mid-Atlantic Ridge at 43.5°N and ∼3 km water depth shows distinct evidence of the deglacial events known as Heinrich event 1 (probably the marine equivalent of Oldest Dryas cooling in Europe) and the Younger Dryas. The Heinrich event, dated at three levels to between 14.3 and 15.0 ka, is marked by a minimum in foraminifera per gram, by maxima in rates of sedimentation, ice rafted debris per gram, and relative abundance of N. pachyderma (s.), and by a δ18O minimum in planktonic foraminifera. The Younger Dryas event is marked by peak abundance of N. pachyderma (s.) and a planktonic δ18O maximum. Benthic foraminiferal δ13C reaches minimum values during both the Heinrich event and the Younger Dryas. Our data indicate pronounced changes in surface water properties were coupled with reduced production of North Atlantic Deep Water at each of these times.