82 



STRUCTURAL GEOLOGY OF NORTH AMERICA 



Series 



Character 



Thickness, Feet 



Series 



Character 



Thickness, Feet 



Unconformity 

 Andesitic rocks, including breccia, with limestone matrix 

 and lava flows (in part with pillow structure), locally 

 interbedded with slate and other sediments 1400 plus 



Unconformity 

 Conglomerate, sandstone, and limestone; in the 

 Ketchikan district includes considerable black slate 

 in upper part 1600 plus or minus 



Unconformity 



Thick-bedded limestone; with common to abundant in- 

 tercalated layers of white chert 1000 



Conglomerate, limestone, sandstone, andesitic and ba- 

 saltic lava, tuff, and locally rhyolitic volcanic rocks 3000 plus or minus 



Unconformity 

 White massive limestone 100 plus 



Interbedded coarsely crystalline limestone and black 

 chert, overlain by interlayered dense gray quartzite 

 and cherty limestone; sparse conglomerate 1000 



Basalt, andesite (in part pillow lava), tuff, limestone, 



sandstone, slate, and conglomerate 1000 



Unconformity (?) 

 Limestone 600 plus 



Andesitic green to gray tuff (locally cherty) and gray- 

 wacke, with locally fine, conglomeratic layers, inter- 

 calated limestone, and a minor amount of andesitic 

 lava and breccia 2400 plus 



Andesitic lava (in part pillow lava), breccia, tuff, con- 

 glomerate and locally rhyolitic lava 2000 



Interbedded limestone, slate, chert, andesitic lava, 

 breccia, tuff, and locally conglomerate 



Conglomerate and graywacke-like sandstone, with lo- 

 cally interbedded limestone 2000 



Unconformity 



Green-gray graywacke with sparse conglomerate beds. 

 Interbedded red, green-gray, and gray graywacke, 

 like sandstone with small amount of shale 5000 plus 



Green-gray shale with intercalated red beds and thin- 

 layered fine-grained gray sandstone, shale, and 

 dense limestone 500 plus 



Jurassic 

 Upper Triassic 

 Permian 



Pennsylvanian (?) 

 Mississippian 



Upper Devonian 

 Middle Devonian 



Silurian 



Predominantly thick-bedded dense limestone; interca- 

 lated with thick beds of coarse conglomerate, thin- 

 layered limestone, nodular and shaly argillaceous 

 limestone and sandstone Ls, 3000; Congl. 1500 4500 plus or minus 



Andesite (in part pillow lava) and andesite porphyry 

 lava; conglomerate; with some associated gray- 

 wacke, tuff, breccia, and limestone 3000 plus or minus 



Unconformity (?) 

 Indurated graywacke with associated black slate and 



sparse conglomerate and limy sediments ? 



Unconformity (?) 



Indurated graywacke with associated black slate and 

 sparse conglomerate and limy beds; locally andesitic 

 pillow-lava and volcanic rocks ? 



Thin-layered black chert with black graptolitic slate part- 

 ings, graywacke, and locally andesitic volcanic rocks ? 



Greenstone schist with intercalated or interbedded 



limestone ? 



Limestone ? 



Schist with beds of limestone and slate ? 



Schist ? 



Middle 

 Ordovician 



Lower Ordovician 



Probably pre- 

 Ordovician to 

 Devonian Wales 

 group (meta- 

 morphic rocks) 



sippian formations. Thick-bedded chert and cherty tuff occur in the Mid- 

 dle Devonian, and white chert is common in the Upper Permian. 



Schists and gneisses are also common, and are the result principally of 

 permeating hot solutions attendant upon the emplacement and solidifica- 

 tion of the vast volume of magma in addition to orogenic stresses (Bud- 

 dington and Chapin, 1929). 



Northern British Columbia and the Yukon. The Geologic Map of 

 Canada summarizes what is known of the distribution of Paleozoic rocks 

 in northern British Columbia and the Yukon. Great areas are still marked 

 "Paleozoic, mainly sedimentary rocks," but other large areas are labeled 

 "Carboniferous and Permian sedimentary rocks." Geology and Economic 

 Minerals of Canada, 1947, summarizes the distribution as follows: 



During the Carboniferous and Permian periods apparendy nearly the 

 whole of the Western Cordilleran region (west of the Rocky Mountain trench) 

 lay beneath the sea, and great thicknesses of sedimentary and volcanic material 



