Analytical Abstracts of Current 

 Literature. 



SUMMARY OF CURRENT PRE-CAMBRIAN NORTH 

 AMERICAN LITERATURE.^ 



Ells- gives a description of the Laurentian of the Ottawa district. A 

 reexamination of the Trembling Mountain section shows that, instead of its 

 being a continuous ascending series, there are no less than three anticlines 

 and their corresponding synclines, and the section is still further compli- 

 cated by faults of every considerable extent. But one limestone was found, 

 that of Trembling Lake, and this instead of being interstratified with 

 the orthoclase gneiss is in the form of a synclinal overlying this gneiss. 

 This limestone at no point was observed to be more than 50 feet in vertical 

 thickness. 



In the region between the anorthosite area and the Gatineau river the 

 limestone in nearly every case occupies well defined synclinals separated by 

 anticlinals of the underlying gneiss. In this area it has been found impos- 

 sible to trace any bands of limestone to any considerable distance con- 

 tinuously, the limestones being often local in their development, and lenticular 

 in form. 



In the limestone in certain places are masses of quartzose rock and crushed 

 gneiss, presenting the aspect of a true conglomerate. As to the thickness of 

 the gneiss, on the Rouge river, the most favorable place found for measure- 

 ment, the section gave a thickness of 10,000 feet beneath the limestone, if 

 there is no break, but this figure may not be accurate, as faults and repetitions 

 of strata may occur at several places. 



Intrusive within the gneiss and limestone are the anorthosite and syenite 

 masses of Grenville and Chatham, and other less conspicuous masses. No 

 less than six or seven clearly distinguished periods of intrusion can be recog- 

 nized. The augen gneiss of the Rouge river is probably also an intrusive. 



'Continued from Vol. I., p. 541. 



= The Laurentian of the Ottawa District, by R. W. Ells. Bull. Geol. Soc. of Am., 

 Vol. IV., pp. 349-360. 



109 



