Handbook of Paleontology 361 



Upper Devonian of about 5800 to 9700 feet (mostly red 

 shales, coarse sandstones and conglomerates). In 

 Maryland the Lower Devonian has a greater thickness, 

 the Middle and Upper Devonian less. Devonian deposits 

 in the interior are very thin compared to those in the 

 east. About 50 feet of Middle Devonian limestone and 

 shales are represented at Louisville, Ky. In the south- 

 ern Mississippian valley and Oklahoma the deposits rep- 

 resent, for the most part, Lower and early Middle De- 

 vonian and here also the deposits are thin (less than 250 

 feet). Western Ontario, Canada, shows a thickness of 

 something over 500 feet of deposits, mostly shales, but 

 the thickest accumulations in the median part of North 

 America, thicker than in Ontario, are found in Michi- 

 gan, particularly about Alpena, where they represent the 

 Middle and Upper Devonian. Devonian deposits in the 

 Cordilleran area are mostly limestones and in Nevada 

 have a thickness of 4000 to 8000 feet (limestones and 

 calcareous shales), though most sections in this area are 

 comparatively thin in the United States. In the MacKen- 

 sie valley about 1000 feet (nearly one-half limestone) 

 were deposited and exposures show about 600 feet of 

 limestone in southeastern Alaska. 



Throughout the Devonian and especially in the Upper 

 Devonian igneous activity occurred in the New England 

 states and the Maritime Provinces of Canada in con- 

 nection with the Acadian Disturbance which was per- 

 haps a forerunner of the later revolution which formed 

 the Appalachian mountains. The volcanic cones are 

 eroded away and only the deeper seated volcanic rocks 

 remain. Mount Royal at Montreal is one of these. Be- 

 sides the volcanic extrusions, igneous intrusions (grani- 



