HOW MUCH MASS MOVEMENT?
Oard (p. 91) attacks the validity of the glacial deposits of the Dwyka Group by claiming that abundant “non-glacial” mass flows are already known to be present in the group and that distinguishing glacial deposits from non-glacial mass flows is very uncertain. Specifically, Oard (p. 91) cites an example from Mexico in Humphrey (1956, p. 1323) and Newell (1957) of how a now-known non-glacial diamictite was earlier mistaken for a glacial deposit. According to Oard (p. 91), Humphrey (1956, p. 1323) and Newell (1957) show how mass flow deposits may be easily mistaken for glacial deposits. Nevertheless, more recent and detailed studies by Visser (1993), Cole (1991), and others demonstrate that the glacial and non-glacial deposits of the Dwyka and Ecca groups are distinguishable with careful laboratory and fieldwork. Oard (p. 91) also cites a number of references that indicate that the Dwyka Group contains many debris flow deposits. Oard implies that since much of the group is already consid
