BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 2, pp. 225-242, PL. 8 FEBRUARY 26, 1891 



THE GEOTECTONIC AND PHYSIOGRAPHIC GEOLOGY OF 

 WESTERN ARKANSAS.^ 



/ BY ARTHUR WINSLOW. 



[Read before the Society August 19, 1890.) 



CONTENTS. 



Page. 



Introduction 225 



The Area discussed 225 



Historical Sketch 226 



Inception of the present Woi-k 226 



Age of the Rocks of Western Arkansas 227 



The Geotectonic Geology 228 



Character and Distribution of the Flexures 228 



Dates of Elevation and Folding 231 



Cause of Elevation and Folding 231 



The Physiographic Geology 234 



The general Surface 234 



Mountains 235 



Ridges and Mesas 235 



Valleys 238 



General Character 238 



Monoclinal Valleys 238 



Anticlinal Valleys 238 



Synclinal Valleys 239 



Valleys in horizontal Strata 239 



The Prairies of Western Arkansas 240 



The River System 241 



Introduction. 



The Area discussed. — The following pages refer chiefly to what is known 

 as the coal region of Arkansas. This is in an area situated in the western 

 part of the state, tributary to the Arkansas river. It extends from the Bos- 

 ton mountains on the north to beyond the Poteau and Petit Jean mountains 

 on the south, thus covering an area about 100 miles long in an east-and-west 

 direction by 50 miles broad in a uorth-and-south direction. 



* Published with the approval of Dr. John C. Branner, State Geologist of Arkansas. 



XXX IV— Bull. Geol. Soc. Am., Vol. 2, 1890. 



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