The onset of northern hemisphere glaciation is commonly placed at 2 to 15 Ma. Here, by studying sediment records from an ODP core from the north Atlantic we demonstrate that ice must have been at least transiently present in the northern hemisphere back into the Eocene. We find evidence for ice rafted debris throughout the sedimentary section studied, most dramatically in the form of the dropstone photographed above.
Online [publisher]: http://dx.doi.org/10.1016/j.epsl.2007.09.045
Reference: Tripati, Aradhna K., Robert A. Eagle, Andrew Morton, Julian A. Dowdeswell, Katie L. Atkinson, Yannick Bahé, Caroline F. Dawber, Emma Khadun, Ruth M.H. Shaw, Oliver Shorttle, Lavaniya Thanabalasundaram. Evidence for glaciation in the Northern Hemisphere back to 44 Ma from ice-rafted debris in the Greenland Sea. Earth and Planetary Science Letters 265, no. 1 (2008): 112-122.