HAWKINS, LOCKATONG FORMATION OF THE TRIASSIC 161 



well exposed along the valley of Lockatong Creek, Hunterdon Co., X. J., 

 which is the type section. 



N. H. Darton and H. B. Kiimmel, in their reports accompanying the 

 recent geologic folios (Trenton and Philadelphia Folios), repeatedly 

 emphasize the presence of wide transition zones on the horders of the 

 Lockatong. For instance, on pages 7 and 8 of the Pliiladelphia Folio, 

 Darton says : 



"These three formations (the Stockton, Lockatong, and Brunswick) are not 

 sharply separated by abrupt changes of materials, but usually merge through 

 beds of passage which appear to vary somewhat in thickness and possibly also 

 in stratigraphic position in different areas." 



Poor definition of the boundaries of the Lockatong series is typical on 

 account of the pronounced interdigitation with the formations above and 

 below, which has been the cause of some uncertainty in mapping those 

 boundaries. Its boundaries are rarely if ever definite planes, but are 

 zones of transition from one formation to the other, by alternation of 

 beds. It seems plain, therefore, that a portion of the Lockatong beds 

 that lie along its lower margin are really as closely related to the Stock- 

 ton formation as to the Lockatong, while several hundred feet of beds, 

 more or less, in its upper portion, might just as reasonably be classed 

 with the Brunswick. The presence of abundant ripple marks and mud- 

 cracks in the transition beds, as at Lockatong Creek, emphasize the evi- 

 dence of rapidly varying conditions. Along the strike the Lockatong 

 seems to pass into the other sediments, its typical argillites being there 

 represented by rocks of a different nature. The conclusion of H. B. 

 Kummel,^^ with regard to that portion of the Lockatong series which 

 occurs in New Jersey, would therefore appear to be equally true of the 

 area of Lockatong rocks as a whole. In discussing the absence of the 

 argillites in the general area north of Princeton, he says : 



"The most probable explanation for the absence of these beds is, therefore, 

 that the conditions favoring their formation did not prevail in the northern 

 part of the basin ; that here the red shales and sandstones were deposited con- 

 temporaneously with the argillites and flagstones of the southwest, and that, 

 could we trace the latter from the point near Princeton, where they begin to 

 disappear beneath the Pensauken and Cretaceous deposits, we would find all 

 the steps in their transition to the soft red shales. It follows from this that 

 the term Lockatong. when used apart from the particular rocks to which it was 

 first applied, represents certain conditions of sedimentation, which resulted in 

 the deposition of hard shales, flags, and argillites, and not a definite time- 

 period." 



" Ann. Kept. Stale Ceol. N. T.. 1897. p. 41. 



