HAWKINS, LOCKATONG FORMATION OF THE TRIASSIC 165 



into the red argillites, where there arc neither carbon nor fossils, would 

 presumably indicate a gradual decrease in the amount of water present. 

 The growth of crystals within the sediments would seemingly require the 

 presence of a certain amount of moisture, although the quantity of water 

 may have been slight. 



Jones,^^ in describing the English estlieriae in particular, says : 



"The recent estheriae are found in fresh water, rarely in brackish water. 

 Guided by this fact, and taking for granted that our fossils were true estheriae, 

 and that estheriae always have had fresh-water habitats, we should suppose 

 that the deposits in which these fossils are found, free from any appearance of 

 having been drifted, must have been formed in rivers, lakes, or lagoons. . . . 

 The recent estheriae appear, as it were, suddenly, in pools and ditches of rain- 

 water, and are quickly developed in tanks or ponds dry even ten or eleven 

 months of the year. ... At all events, there is no necessity for supixjsing 

 them to have been marine ; but where they occur by themselves, or in company 

 only of fishes and plants (the association of remains of land-plants with the 

 estheriae is of frequent occurrence), they may be regarded as having lived and 

 died in fresh (or possibly brackish) water." 



All this goes to show that the waters where the estherige lived during 

 Lockatong time were not the waters of the sea, but were rather those of 

 inland playa lakes, such as have been described. Under these conditions, 

 part of the sediments were deposited where there was much organic mat- 

 ter. The carbon present, under the prevailing conditions of moisture 

 and soft sediments, speedily reduced the iron in those sediments to a low 

 state of oxidation, and the color of the mud became gray. Certain strata 

 of greenish argillites, whose color, as shown by chemical means, seems to be 

 due to iron silicate, occur at Ewing, Scudders Falls and elsewhere. These 

 layers are seamed with ramifying stringers of red mud which extend 

 downward from an overlying red bed for two feet or so into the green 

 sediments. This red material is evidently mud which has descended from 

 above, filling deep mud-cracks in the earlier material. The fact that such 

 exceedingly deep mud-cracks could form and remain open in these green 

 muds shows that they must have remained damp throughout for a long 

 time. This agrees with our hypothesis that organic matter in the moist 

 sediments had time to reduce the iron in them. Mud-cracks are common 

 in the red argillite layers in places, but so far as the writer has observed, 

 they never appear deep. This shows that the red mud had an opportu- 

 nity to dry quickly, and under such conditions any organic matter present 

 was oxidized and disappeared, so that iron in the ferric state remained, 

 giving a red color to the rock. The small residue of carbon remaining in 

 the gray layers is the macerated remnant left after the reduction of the 

 iron. 



" Op. cit., pp. 7-8. 



