632 abstracts: geology 



cipally to the elucidation of the Tuscaloosa flora, which, as described 

 in the systematic chapter, embraces 151 species. The present treatment 

 is conservative, as a considerable number of additional forms repre- 

 sented in the collections by incomplete material have been left un- 

 characterized. _ R. W. StonE. 



GEOLOGY. — Water-power investigations and mining developments in 

 southeastern Alaska. G. H. Canfield, Theodore Chapin, and 

 R. M. OvERBECK. U. S. Geol. Survey Bull. 692-B. Pp. 94 

 (43-136), pis. 2. 1919. 



Contents : 



1. Water -power investigations in southeastern Alaska. George 

 H. Canfield. 



2. Mining developments in the Ketchikan district. Theodore 

 Chapin. 



3. Geology and mineral resources of the west coast oj Chichagof Island.. 

 R. M. OvERBECK. 



1. Consists of gaging station records. 



2. A brief note on mining in Ketchikan district in 19 17. 



3. The complex geology of the west coast of Chichagof Island is the 

 result largely of extensive intrusion, which has metamorphosed the 

 rocks cut by the intrusive bodies and has complicated their structure. 

 The geology of the island is discussed under the following heads: (i) 

 Undifferentiated metamorphic rocks; (2) graywacke; (3) igneous rocks ;. 

 (4) development of the topographic features. The rocks of the un- 

 differentiated metamorphic series are sheared conglomerate, limestone, 

 argillite, tuff, flow rock, and intrusive rock, and several types of schist. 

 No determinable fossils were found in these rocks; and although the 

 rocks constituting this series may be of different ages, they are probably 

 older than Jurassic or Lower Cretaceous. The graywacke series con- 

 sists of graywacke, of some slaty and argillaceous beds, and of a little 

 greenstone. The igneous rocks are both intrusive rocks and flow rocks. 

 Granite, quartz diorite, diorite, alaskite, aplite, hornblende gabbro,. 

 norite, greenstone, and possibly some andesite, are the types of rocks 

 represented. Quaternary deposits are practically absent, but the re- 

 sults of the action of the ice are remarkably well shown by the topo- 

 graphic features. Mines and prospects of gold, copper and nickel are 

 described. • R. W. StonE. 



