266 SCHUCHERT— BLACK SHALE DEPOSITION. [May 7, 



To return to the Black Sea and its sediments, these are of 

 three categories: (i) from the shore to about 120 feet occur the 

 accumulations of sandy detritals; (2) from 120 to 600 feet is 

 found a gray-blue sticky ooze, often replete with small fragile shells, 

 mainly of Modiola ; and (3) in the greater depths the bottom is cov- 

 ered with (a) a tough, sticky, black ooze, with much precipitation 

 of iron sulphide, an abundance of diatoms and fragments of the 

 youngest stages of bivalves, all of which organisms are from the 

 plankton, and (b) the dark blue ooze poor in iron sulphide and 

 richer in the finest-grained CaC03, which in places forms thin 

 banks, and an abundance of pelagic diatoms. Zones i and 2 alone 

 have benthonic organisms, with the greatest abundance between 

 210 and 600 feet; the latter is the zone of Modiola phaseolina and a 

 great variety of bivalves and gastropods (68 species occur in the 

 shallower waters). 



The Kupferschiefer sea, like the Black Sea, had bottom waters 

 with about the average normal salt content, as proved by the typical 

 Zechstein invertebrates. However, because of the lack of oxygen 

 and the high content of sulphuretted hydrogen and COo an abun- 

 dant bottom life was impossible. That the top water of the Kupfer- 

 schiefer sea was also fresh is proved by the wide distribution of the 

 freshwater fishes in the sediments, the widely uniform spreading of 

 the thin zone of shale, and the presence of land plants and land 

 vertebrates. If all the water had been salty, the fine muds should 

 have been laid down in a narrow zone bordering the margin of the 

 sea, and this is not the case in the Kupferschiefer sea. The slow 

 decomposition of the organic remains (mainly the plankton) and 

 the lack of oxygen in the depths led further to the formation of the 

 bituminous content (from 6 to 20 per cent.). 



As the Black Sea goes down to 7,360 feet, the question must be 

 asked : What was the depth of the Kupferschiefer sea ? A positive 

 and exact answer can not be given, but the small thickness of the 

 shale over wide areas, combined with its intimate and variously 

 modified connection below with the Zechstein conglomerate and 

 above with the Zechstein dolomite, and its shallow-water life, show 

 that "it is a deposit of the shallowest and shallower seas." To 

 the reviewer, the depth seems to be well within that assigned the 



