INTRUSIVE IGNEOUS BODIES 



305 



mational sheets. Sills are sheets intruded between parallel strata. 

 They have essentially the characters of dikes, except that they are 



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Confluence of Kettle 

 River and Rock Creek 



1 mile 



SCALE 



International Boundary 



Fig. 43. Diagrammatic map of a Tertiary "chonolith" of thombenporphyry 

 (crosses), cutting intensely folded Pal?eozoic sediments (broken 

 lines) and Tertiary sandstones and conglomerates (white) Kettle 

 River, British Columbia. (After Daly.) Late Tertiary lava caps 

 (dots) cover the porphyry in the north. The Tertiary sediments 

 are tilted and faulted, the intrusions occurring at the same time 

 or immediately after. 



botinded by parallel strata. Like dikes, they may be simple, mul- 

 tiple or composite. (Figs. 44, 45.) Interformational sheets differ 

 from sills in that they are intruded along a line of unconformity, 



Fig. 44. Section of an intrusive sheet or sill (s) and connecting dike (d). 



and that therefore the subjacent strata are not parallel to it, though 

 the superjacent ones are. 



