| 释义 |
ˈundermass Geol.
[under-1 5 c.]
An older, deformed body of rock overlain by younger, undeformed strata.
1942O. D. von Engeln Geomorphol. ix. 168 The geomorphic significance of the abrupt, commonly marked in kind, transition between the materials above and below a plane of angular unconformity is indicated by the introduction of the terms cover mass and undermass. 1956D. L. Linton Sheffield ii. 35 We..interpret it as the product of the cycle(s) of erosion which stripped away the presumed chalk cover, removed some hundreds of feet of the undermass, and saw the first group of adjustments of the superimposed streams to the underlying structures. 1966[see plate tectonics s.v. plate n. 21]. |