phacolith

plural phacoliths

1. geographyA lens-shaped mass that occurs in an anticlinal crest or synclinal trough.

   This body is a phacolith intruded along the gneiss-schist boundary in the trough of a syncline that plunges 16° southeast.

   1947, Virgil Everett Barnes, Raymond Fillmore Dawson, George Ashworth Parkinson, Building Stones of Central Texas - Volume 19, page 21

   2 more examples

   This bedding forms a distinctive stratigraphic sequence that may be traced from phacolith to phacolith throughout an area of 1,200 square miles.

   1964, Geological Survey Professional Paper, volume 501, page A-81

   Corndon Hill, which lies east of Montgomery in Powys, Wales, is a circular phacolith made of Ordovician dolerite (Figure 5.3b).

   2007, Richard Huggett, Fundamentals of Geomorphology, page 120