Marcou's Geological Map of the United States. 385 



The extensive coal-fields of Puget Sound and the Coast of 

 Oregon are represented as Upper Carboniferous or of the true 

 coal-period. All the evidence which can be procured concerning 

 the age of these deposits shows them to be Tertiary. The re- 

 semblance of the sandstone found w r ith the coal to that of San 

 Francisco, and the presence of Pectens in it has been noticed in 

 published reports. Observations by Prof J. S. Newberry reported 

 since the publication of the map show that these coal-deposits 

 are undoubtedly Tertiary/' 5 " 



In the region of the Wind Eiver mountains, a range called 

 the Black Hills, extending northeast of the Platte, has found a 

 place in most of our maps. We find the geological structure of 

 this range indicated on the map, as granitic and carboniferous, 

 while on another map published in Gotha, it is represented as com- 

 posed of cupriferous trap. A recent exploration of that region 

 by Lieut. G. K. Warren, IT. S. A., shows that this range is purely 

 imaginary arid should not appear on the maps north of the 

 Platte. 



According to the map, the region of the South Pass is occu- 

 pied by a belt of cupriferous trap, extending over at least two 

 degrees of longitude, and in a northeast and southwest direction, 

 with the same trend as Keweenaw point and Isle Eoyale, Lake 

 Superior. There is no record of any such outcrops as this in 

 any of the reports of explorers who have visited that region. 

 Fremont, Stansbury and others, found horizontal sedimentary 

 formations resting on granitic rocks, f 



The Wind Kiver range, which according to Col. Fremont and 

 his collection, is granitic and metamorphic, trending north-west- 

 erly, is not represented on the map. Fremont's peak, however, 

 the highest peak of the range, and described by Fremont as 

 composed of granite, gneiss, sjrenite, and syenitic gneiss, is rep- 

 resented as a volcano. The Eaton Mountains are also colored as 

 volcanic ; in Abert's Eeport they are described as sedimentary, 

 and coal-plants were obtained there and figured in the report.^ 



These, however, are but inconsiderable errors when compared 

 with the representation of the geological age of the strata form- 

 ing the broad table lands on each side of the great central chain 

 of mountains. These are represented as Jurassic above and Tri- 

 assic below. The Jurassic forms a conspicuous feature on the 

 map and includes the Llano Estacado, and all the table-lands 

 from the Missouri to the Eio Grande. It is surrounded by a 



* Proceedings of the American Association for tbe Advancement of Science, 

 Albany, 1856. 



f See the descriptions of the collections by Prof. James Hall, and report of Col. 

 J. C. Fremont, p. 295. 



\ Report of an Examination of New Mexico, by Lieut. J. W. Abert, IT. S. 

 Top. Engineers, 1848 



SECOND SERIES, VOL. XXII, NO. 66. — NOV., 1856. 

 49 



