Geology and Natural History. 477 



II. Geology and Natural History. 



1. United States Geological Survey. — The following publica- 

 tions have been recently issued : 



Folio No. 102. Indiana Folio, Pennsylvania ; by George B. 

 Richardson. The Indiana quadrangle is made up of Carbonifer- 

 ous strata nearly all belonging to the Pennsylvanian series and 

 containing workable beds of coal (Freeport). The two charac- 

 teristic plains of the Allegheny Plateaus are almost unrecogni- 

 zable in this part of Pennsylvania. The geologist will note the 

 omission of structure sections. 



No. 103. Nampa Folio, Idaho-Oregon ; by Waldemae Llnd- 

 gren and N. F. Drake. The geological map of the Nampa 

 quadrangle shows wide areas of dissected Tertiary lake beds 

 together with extensive Quaternary gravels and recent flood 

 plains. Tertiary basalt and rhyolite and Quaternary basalt occupy 

 smaller areas. The lake beds of the Payette and Idaho forma- 

 tions once covered the whole district and this folio is in particu- 

 lar a study of the geographical conditions during the formation 

 and partial destruction of beds of sand, gravel and clay with a 

 thickness of 200 to 1000 feet. The characteristics of stream beds 

 in arid regions are well shown by the Payette, Boise and Snake 

 rivers. 



No. 104. Silver City Folio, Idaho ; by Waldemae Lindgren 

 and N. F. Drake. With the exception of Cretaceous ? granite, 

 the formations represented on the Silver City quadrangle are 

 Eocene, Pliocene and Quaternary. An early Tertiary epoch of 

 erosion was followed by outbursts of rhyolite and basalt and the 

 deposition of the Payette lake beds to a thickness of 2000 feet. 

 A short period of erosion enabled the streams to cut to their 

 present levels. The Idaho formation was deposited in the waters 

 of a shallow lake during Pliocene time. The Snake River Can- 

 yon was cut during Miocene. Glassy basalts form the highest 

 Tertiary beds and may have extended into the Quaternary. Ter- 

 races show the gradually deepening channel of the Snake River. 

 The ore deposits at Silver City are fissure veins of post-Eocene 

 age and cut through granite, rhyolite and basalt. Opals occur in 

 vesicular cavities in the rhyolite and basalts. 



No. 105. Patoka Folio, Indiana-Illinois ; by Myron L. Fuller 

 and Frederick G. Clapp. Carboniferous strata of the Pennsyl- 

 vanian series containing minor veins of coal are exposed in a 

 small portion of the Patoka quadrangle. The most prominent 

 and widespread formations are the glacial drift and the Wabash 

 flood plains. The Illinoian stage is represented by an extensive 

 series of lake deposits, gravel plains and ridges, and till sheets. 

 The Iowan stage is represented by marl loess, while of the Wis- 

 consin stage there remain small areas of dunes and terraces. The 

 mineral resources of this region are coals and clays. Much valu- 

 able land has been reclaimed by draining and diking. 



Bulletin No. 225. Contributions to Economic Geology, 1903. 



