Pre-Mesozoic Ice Ages: Their Bearing on Understanding the Climate System



It is a pleasure to read a book that summarizes a well-respected scientist's lifetime experience with a subject. In this particular case the subject involves pre-Mesozoic glaciations, and the author, John Crowell, has played a key role over the last few decades in both fundamental research and synthesizing our understanding of this interesting and important topic.

Crowell's book, which is a monograph in the true sense of the word, summarizes in considerable detail the various types of geologic evidence for glaciations in the Late Paleozoic (256–338 Ma), Late Devonian-Early Carboniferous (353–363 Ma), Late Ordovician-Early Silurian (429–445 Ma), Early Cambrian/Neoproterozoic (∼520–950 Ma), Early Proterozoic (2200–2400 Ma), and the earliest glaciation recognized so far, in the Archean of South Africa (∼2950 Ma). There is also a brief but valuable discussion of the nature of evidence for cooling in the Cretaceous.