636 



SCIENCE 



[N. S. Vol. XXIX. No. 746 



The well-known trap sheets which form one of 

 the most salient geologic features of the north 

 shore of Lake Superior, are usually regarded as 

 intrusive in origin and of the nature of lacoolitic 

 sills. In the basin of Lake Nipigon, lying north 

 of Lake Superior, on the Laurentian peneplain, 

 the trap sheets are found to rest either directly 

 upon the Archean rocks or upon small outliers of 

 the sediments, often many miles distant from the 

 main areas of similar age. The traps are known 

 to rest unconformably upon at least five difi'erent 

 earlier formations. This unconformity can be ex- 

 plained by attributing to the fluid traps the ability 

 to insinuate themselves, in an extremely intricate 

 manner and over a very large area, between over- 

 lying sediments and underlying crystallines, here 

 and there masses of the sediments remaining so 

 firmly attached to the bed on which they rested 

 that the traps flowed over and around them, cut- 

 ting across the beds. 



While many of the trap sheets along the north 

 shore of Lake Superior are undoubtedly laccolitic 

 sills, still the writer is inclined to believe that 

 the balance of evidence shows that these sills are 

 conflned largely to the areas \mderlain by sedi- 

 ments of later date than the Archean. A simpler 

 explanation, and one that appeals to the writer 

 as more reasonable, of the relations known to 

 exist between these trap sheets and the imder- 

 lying rocks in the Nipigon basin, is that, at least 

 along the line of the escarpments which mark the 

 boundary between the sediments and the Archean 

 areas to the north and out upon the old land 

 itself, the same traps flowed over an eroded sur- 

 face of subaerial origin. 



Incidentally there is strong, though not con- 

 clusive, evidence for considering that these flows 

 might be even of post-Cretaceous age. 



This paper was discussed by Professors A. W. 

 Grabau, A. W. G. Wilson, A. C. Lane and A. F. 

 Foerste. 



Then was read: 



Reconnaissance in Arizona and Western New 



Mexico along the Santa FS Railroad: N. H. 



Daeton, Washington, D. C. 



The reconnaissance was made for the purpose 

 of ascertaining the prospects for deep wells to 

 supply water to the railroad and settlements along 

 its line. The region examined was from ten to 

 forty miles wide and in this area the principal 

 structural and stratigraphic features of forma- 

 tions from Cambrian to Cretaceous were deter- 

 mined. 



This was followed by the reading of: 



Geologic Studies in the Alaska Peninsula: Wal- 

 lace W. Atwood. (Introduced by A. H. 

 Brooks.) 



Detailed work was done in the vicinity of Chig- 

 nik, Balboa and Herendeen bays and on the 

 Island of Unga. The Balboa-Herendeen Bay dis- 

 trict was selected as a type area in the peninsula, 

 and detailed studies were pursued in the hope of 

 working out a key to the general geologic condi- 

 tions of this portion of Alaska. 



The formations exposed include the Upper 

 Jurassic, Lower and Upper Cretaceous, marine 

 and freshwater Eocene, Miocene, possibly some 

 Pliocene, Pleistocene and recent Kenai plants 

 were found associated with marine invertebrate 

 shells of Upper Eocene age. 



Vast quantities of igneous rocks have been 

 intruded into the sedimentary series, and overly- 

 ing a portion of the area there are volcanic tuffs 

 and basic flows of post-Miocene age. 



Coal occurs in the Upper Cretaceous and Eocene. 

 Gold and copper prospects were examined at sev- 

 eral localities. 

 Then was presented: 



Present Knowledge of the Oklahoma Red Beds: 

 Chaeles N. GtouLD, Norman, Okla. 

 After this was read: 



The Fauna of the Fern Qlen Formation: Stuabt 



Wellee, Chicago, 111. 



The Fern Glen formation is typically developed 

 in St. Louis and Jefferson counties, Missouri, and 

 Monroe County, Illinois. It lies at the summit 

 of the Kinderhook group and consists of beds of 

 red calcareous shales and red limestones, with a 

 maximum thickness of about forty feet. The 

 upper beds are more greenish in color and merge 

 gradually into the superjacent Burlington lime- 

 stone. The fauna is distinctly a member of the 

 southern group of Kinderhook faunas and con- 

 sists for the most part of corals, crinoids and 

 braohiopods, with a few blastoids, molluscs and 

 trilobites. Many of the species are undescribed, 

 although more or less closely related to known 

 forms in other Kinderhook faunas or in the Bur- 

 lington limestone. The correlation of the fauna 

 is with those of the basal Knobstone shales of 

 Kentucky, the St. Joe marble of Arkansas and the 

 Lake Valley beds of New Mexico. 



The paper was discussed by Professors Charles 

 Schuchert, Stuart Weller and E. O. Ulrich. 



The next two papers were read by title: 



Age and Geologic Relations of the Sankaty Beds, 

 Nantucket: W. O. Cbosby, Boston, Mass. 



J 



