Reviews 



Lockatong Formation of the Triassic of New Jersey and Pennsyl- 

 vania. By A. C. Hawkins. Annals N.Y. Acad. Sci., XXIII. 

 145-76, Plate 1, January 27, 1914. 

 The Lockatong formation is the middle member of the Newark 

 series of the Triassic, extending from a point just west of Phoenixville, 

 Pennsylvania, to Princeton, New Jersey. The rocks of the formation 

 are dense, fine-grained, massive argillites, with some shales. The forma- 

 tion as a whole has a decidedly lens-like character. On the basis of the 

 general structure, lithologic character, and type of fossils, which include 

 estheriae, fish-scales, ostracods, and plant remains, it is concluded that 

 the sediments were laid down near the center of an inland basin. The 

 particles of the argillite are for the most part cemented by silica, which 

 renders the formation very hard and a pronounced ridge-maker. The 

 color of the beds is due to iron in various states of oxidation. The 

 boundaries of the Lockatong are very uncertain, owing to the fact that 

 it passes by a series of transitional dovetailing strata into the other 

 formations of the Newark. Since part or all of the Lockatong may be 

 contemporaneous with portions of the Stockton and Brunswick forma- 

 tions elsewhere, it seems that as a definite geological time unit the 

 Lockatong is valueless. There are three principal joint directions in the 

 Lockatong formation, the most important of which is remarkably con- 

 stant, and extends into the borders of a diabase mass near Rocky Hill, 

 which is interpreted as an extension of the Palisade sill. Titanium 

 minerals, brookite and ilmenite, are found in this major joint series, 

 apparently far removed from the diabase. Analcite and barite also 

 occur. That these minerals are derived from the igneous rocks is indi- 

 cated by similar occurrences in New Jersey elsewhere. Parts of the 

 Lockatong argillite are very well adapted for commercial use. 



R. C. M. 



Geological Map of Tennessee. Compiled by Olaf P. Jenkins, 



A. H. Purdue, State Geologist. 



This map represents Archean, Cambrian, Ordovician, Silurian, 



Devonian, Mississippian, Pennsylvanian, Cretaceous (Upper), Eocene, 



Pleistocene, and Recent formations. Few states have so wide a range 



206 



