 After an examination of laminated varve sequences, Muschitiello and Wohlfarth found that the environmental changes that define the beginning of the Younger Dryas are diachronous in their time of occurrence according to latitude.According to the changes, the Younger Dryas occurred as early as AROUND 12,900–13,100 calendar years ago along latitude 56–54°N.Further north, they found that the changes occurred at roughly 12,600–12,750 calendar years ago.