Probability of moraine survival in a succession of glacial advances

Emplacement of glacial moraines normally results in obliteration of any older moraines deposited by less extensive glacial advances, a process we call “obliterative overlap.” A probability analysis of the likely impact of obliterative overlap on the completeness of the glacial record assumes that moraines were deposited at various distances from their glacial source areas randomly over time. Assuming randomness and obliterative overlap, after 10 glacial episodes, the most likely number of surviving moraines is only three. The record of the Pleistocene is in agreement with the probability analysis: the 10 glaciations during the past 0.9 m.y. inferred from the deep-sea record resulted in moraine sequences in which only two or three different-aged moraine belts can generally be distinguished.