THE SALT DEPOSITS 200 
pre-Cambrian to Lower Carboniferous rocks, sank beneath the 
sea and was covered by beds laid down in the Upper Carbonifer- 
ous and Permian Sea. The earlier beds were ordinary marine 
deposits, which were followed by red shales and a dolomitic 
limestone (the Zechstein); their stunted fossils show that 
the connection between the sea of Central Germany and the 
outer ocean had been closed, so that the water had changed 
in composition, and the less adaptable animals and plants had 
perished. As the water evaporated salts were precipitated ; 
the series began at Stassfurt, in the centre of the basin, with 
a thick deposit of rock-salt interbedded with layers of 
anhydrite (CaSO,). These minerals occur in such regular 
alternation as to suggest precipitation by the annual change 
from winter to summer. The lower series of rock-salt and 
gypsum was succeeded by a bed containing potash and 
magnesium salts, so that the sea-water and the bittern were 
both evaporated. These very soluble salts were then covered 
with a layer of clay; the sea again submerged the area; 
a fresh layer of limestone was deposited, and was followed by 
a thick bed of anhydrite and a younger series of interbedded 
rock-salt and anhydrite. Above this series occurs a wide- 
spread sheet of massive rock-salt due to the redeposition of 
salt dissolved out of the underlying beds. Then followed 
another invasion of the sea, which deposited another layer 
of Zechstein and prevented the deposition of a second layer 
of potash salts. This upper limestone was covered by the 
red sandstones of the Bunter or Lower Trias, which were 
deposited under desert conditions on land. 
In other parts of the German salt basin the sequence of 
events was different. Thus towards the valley of the Werra 
River (Fig. 54 A) the primary rock-salt was not deposited, 
but a secondary rock-salt was formed, doubtless of material 
dissolved from the older beds, and the evaporation of occa- 
sional brine pools deposited patches of potash salts. Then 
followed two further layers of Zechstein and a widespread 
thick sheet of Bunter sandstone. The South Harz (C) and 
the Hanover district (B) show an intermediate condition, 
with the lower secondary rock-salt of the Werra basin in- 
tercalated between two great primary salt deposits as at 
Stassfurt (D). 
Iv