4(34 PROCEEDINGS OF COLUMBUS MEETING. 



1 foot. A well developed cleavage-foliation runs parallel to tin' side on which the block rests. In 

 .1.1 and A' A' a. nearly straight secondary banding follows this direction. At BD this banding is 

 completely replaced by a crumpled transverse banding, showing the present position of the origi- 

 nal st rati Heat ion plane. At CC the course of a crumpled quartz lens can be followed parallel to that 

 of the crumpled banding. 



In discussing the paper Dr. J. E. Wolff remarked — 



There is a similar example on a large scale in the rnetamorphic conglomerate 

 series at East Clarendon, near Rutland, Vermont. The rock has a vertical hand- 

 ing and foliation, and the hands, being of different mineral composition, might be 

 taken for stratification, were there not present occasional bands of pebbles with an 

 undulating horizontal course which indicate the original stratification, while the 

 individual pebbles have their major axes turned so as to lie in the plane of vertical 

 banding and are somewhat stretched in that plane. 



The next paper was read by Professor C. \Y. Hall : 



PALEOZOIC FORMATIONS OF SOUTHEASTERN MINNESOTA. 



BY ('. \V. HALL AMI F. \V. SARDESOX. 



In discussing the paper \V J McGee remarked — 



There is some confusion in the nomenclature of the scries of upper Cambrian 

 and basal Silurian strata so admirably described by the authors of this communi- 

 cation. While there tire local and inconstant unconformities, the series as a whole 

 is a continuous one connecting the Cambrian and Silurian. This series is relatively 

 complex in Minnesota and still more complex in Wisconsin, hut relatively simple 

 in Iowa; and in the areas of complex structure, divisions have been discriminated 

 that are lost in the areas of simple structure. Moreover, Owen's name " Lower 

 Magnesian " has become misleading since his correlative term " Upper Magnesian " 

 (including the Niagara and Galena and by implication the intervening Maquoketa) 

 has been dropped from geologic language and literature. Partly for these reasons. 

 the Iowa representative of Owen's "Lower Magnesian," which corresponds to 

 living's a Main Body of Limestone," has been called Oneota limestone from the 

 river on which the formation is typically developed.* 



Professor Hall replied : 



While a certain degree of confusion attaches to the use of Owen's term "Lower 

 Magnesian" for the rocks in question, that confusion disappears when the first 

 element in the name is dropped. "Magnesian" is at the same time a convenient 

 name and possesses the advantages of accurately describing the lithologic and 

 chemical characters of the great mass of dolomite to which it is applied, and of 

 closely corresponding to the original designation which has taken an established 

 place in geologic literature. Indeed the word has become so well fixed in the 

 northwest that we can use it with ease, notwithstanding the advances already 

 made in our knowledge of the rocks included under it. It is the intention of the 

 authors to continue their studies of these strata, discussed in barest outline in the 



*lltli Ann. Rep. U S. Geological Survey, 1892, p. 332. 



