HAWKINS, LOCKATONG FORMATION OF THE TRIAS8IC 159 



poraiy lakes. A region of freshly deposited, unconsolidated muds, on 

 which lakes could exist for any length of time, must have had a level 

 surface throughout its extent, or else drainage would have been developed 

 and the lakes would have been quickly destroyed. The region may have 

 stood but little above sea level, or, what is more likely, a ridge of harder 

 rocks, perhaps some distance away, blocked drainage at the outlet of the 

 basin. The estherise and ostracods are known to be fresh water, or pos- 

 sibly brackish water, forms. Hence the waters in which the Triassic 

 fishes thrived during the same period must have been fresh, or possibly 

 brackish, as the fish scales are found with the other forms mentioned, at 

 Wycombe and elsewhere. This would appear to have some bearing on the 

 problem of the state of the waters in which the same species of fishes 

 lived, at Boonton and Sunderland. The aspect of the whole body of the 

 Lockatong sediments is that of a mass of fine-grained muds, carried down 

 from the higher crystalline uplands surrounding a structural trough, 

 which had been but incompletely filled by the quickly accumulated sedi- 

 ments of the Stockton series. The continued filling-in by these fine 

 materials formed a mud-flat upon which pools of water (playa lakes) 

 gathered, and in time dried up again, leaving large numbers of well 

 formed sun-cracks, and occasional ripple-marked layers, together with 

 the remains of living forms, above described. 



The thin limestone layers encountered at and near Princeton may have 

 been deposited as a chemical precipitate, or may be the product of cal- 

 careous animal remains. Xo fossils were found in these layers. It has 

 been suggested that this limestone might be similar in origin to the desert 

 limestone crusts of Africa and the Bad Lands, which are produced by the 

 evaporation of ground waters brought to the surface by capillary attrac- 

 tion. The Lockatong limestones, however, occur in the midst of black 

 shales which usually carry organic remains. Other thin limestones, which 

 contain abundant Estheria shells and fragments, may have been formed 

 by solution of the Esthena shells themselves. 



Throughout the study of these rocks, nothing has been found in them 

 that would in any measure offer proof of a volcanic origin. Xo coarse 

 material resembling bombs are to be seen in the field, and no trace of 

 anything resembling volcanic ash was observed in the thin sections. In 

 Connecticut, abundant volcanic deposits of the above sorts have been 

 noted in the Trias and described by Emerson and by Davis, but there ap- 

 pears to be a scarcit}^ of such phenomena in the Xew Jersey-J*ennsylvania 

 area. There seems to have been no volcanic activity in this latter sec- 

 tion until long after the Lockatong sediments were deposited and buried 

 under an accumulation of perhaps several thousand feet of the overlving 



