14 DEPARTMENT OF THE INTERIOR 



2 GEORGE V., A. 1912 



masses of basalts and andesites. Younger than any of these formations is an 

 alkaline suite of extrusive and intrusive masses. These intrusions include dikes 

 and irregular injected bodies (chonoliths). Rhomb-porphyry and pulaskite por- 

 phyry are the intrusive types. A less crystalline rhomb-porphyry, alkaline 

 trachyte, and 'shackanite,' an analcitic lava, are the extrusive types. Various 

 pre-Tertiary intrusives are also described. 



Chapter XVI. — The Okanagan Composite Batholith extends from the 

 eastern slope of Osoyoos Lake valley to the Pasayten river, where it is covered 

 by unconformable Cretaceous rocks forming the Pasayten series. The com- 

 ponent batholiths and stocks, with their country-rocks, are described. The 

 whole body is by far the largest continuous mass of plutonic rock in the 

 Boundary belt. The petrographic types represented have wide range of com- 

 position, and the dates of eruption vary from late Paleozoic to the late Tertiary 

 or the Pleistocene. A general idea of the order of eruption and nature of the 

 different bodies may be quickly obtained by an inspection of the general table 

 of contents under ' Chapter XVI '. The reader is also directed to the summary 

 at the end of the chapter itself. 



Chapter XVII. — The Hozomeen range forms a distinct geological province, 

 being principally made up of an extremely thick geosynclinal mass, the Pasayten 

 scries. Its arkose, conglomerate, sandstone, and shale were deposited in a 

 local, rapidly deepening downwarp of Cretaceous date. An important deposit of 

 cudesitic breccia forms the basal member of the series and lies on the eroded 

 surface of the Remmel batholith at the Pasayten river. The Cretaceous rocks 

 are fossiliferous at various horizons. They compose a faulted and otherwise 

 deformed monocline with westward dips steepening toward the west. At Light- 

 ning creek canyon a great fault brings the youngest Cretaceous beds into contact 

 with the much older Hozomeen series, which is tentatively correlated with the 

 Anarchist, Attwood, Pend D'Oreille, and Cache Creek series. 



Intrusive bodies with the relations of stocks, dikes, and chonoliths cut the 

 Pasayten series. Special attention is paid to the Castle Peak granodiorite stock, 

 since its structural relations are clearer than those of any other great intrusive 

 mass in the Boundary belt. The evidences of its downward enlargement and of 

 its having replaced or absorbed the Cretaceous sediments are believed to be 

 clear. 



Chapter XVIII. — West of the Skagit river, which is located on another 

 master fault, the Hozomeen series is again represented in small patches. On 

 the Pacific slope of the Skagit range a thick body of argillite, sandstone, and 

 limestone, with a heavy mass of interbedded volcanics, is fossiliferous (upper 

 Carboniferous) and under the name Chilliwack series is correlated with the 

 Hozomeen series. So far as known, these are the oldest rocks locally developed 

 in the Skagit range. Fossiliferous Triassic argillite, included in the Cultus 

 formation, was found near Cultus lake. A thick mass of sandstone, etc., to the 

 southward is called the Tamihy series. It is unfossiliferous as yet, but on lith- 

 ological grounds is correlated with the Cretaceous Pasayten series farther east. 



