CONTEKTS 405 



I'ase 

 Laramie basiu 449 



East side of Laramie uiouutaiiis 450 



Correlation 450 



Colorado formation 45O 



Occurrence and general relations 450 



Benton formation 45I 



Niobrara formation 451 



Wind River-Owl Creek region 452 



North Platte basin to Rock river 453 



Laramie basin 455 



East side of Laramie mountains 456 



Fossils 457 



Montana formation 458 



Occurrence and general relations 458 



Wind River basin 459 



Laramie basin 459 



East of Laramie mountains 461 



Fossils 461 



Tertiary system 463 



Geologic history 463 



In general 463 



Early Paleozoic conditions 464 



Cambrian sea ; . . 464 



Ordovician submergence 464 



Suurian-Devonian hiatus , 464 



Carboniferous sea 465 



Red gypsiferous sediments 465 



Jurassic to Cretaceous seas 466 



Early Tertiary mountain growth 468 



Oligocene to Pliocene deposition 468 



(quaternary conditions 46D 



Introductory 



During ])()rtions of the summers of 1905 to 1907 I made a recoimais- 

 sanee of tlie geology of parts of central Wyoming, extending from the 

 Colorado state line southwest of Laramie to the Wind Elver moimtains 

 northwest of Lander. Detailed geologic maps were made of much of the 

 region lying east of longitude 107° and south of latitude 43°, and the 

 Laramie and Sherman quadrangles of the U. S. Geological Survey were 

 prepared for folio pulilication. In the western portion of the area T was 

 assisted by ]\rr E. G. Woodruff, and most of the data in the region south- 

 west of Laramie and Cheyenne were obtained for me by i\rr C. E. Siel)en- 

 thal. The work was a continuation soutliward of my explorations in the 



