phacolith Geol.
(ˈfækəʊlɪθ)
[Alteration of prec.: see -lith.]
An intrusive mass of igneous rocks situated between consecutive strata at the top of an anticline or the bottom of a syncline.
| 1910 Lake & Rastall Text-bk. Geol. xiii. 225 These long narrow intrusions are called by Mr. Harker phacolites (more correctly phacoliths). 1947 S. J. Shand Study of Rocks (ed. 2) ii. 16 The phacolith might be described as a saddle-shaped laccolith;..but there is this important difference between a laccolith and a phacolith that the former is the cause of the folding of its country rocks while the latter is a consequence of folding. [Ed. 1 (1931): phacolite, laccolite.] 1971 B. W. Sparks Rocks & Relief iii. 93 Laccoliths are approximately circular, but phacoliths are not, except in the rare case of their being formed in a dome. Usually they are elongated in the direction of the axes of the folds. 1977 A. Hallam Planet Earth 68 Phacoliths are curved sill-like intrusions emplaced in the crests and troughs of folded rocks. |