174 Marine Microbiology 



the interface between water and mud. Tliiobact. tJiioparum has 

 only been found in the zone where sulfur may be precipitated 

 (6). 



EPIGENETIC ORIGIN (Fig. 2) 

 Shor-su (Usbekian SSR) is an example of an epigenetic 

 sulfur bed, the H^S of which originates from an oilfield in the 

 neighborhood ( 12 ) . The microbiological conditions have been 

 studied by Ivanov (3). Desulfurizers live in the saltwater of the 

 oilfield; they produce 0.2 mg/L H-S daily. The rHi-value of the 

 oilwater is about eight to ten. Within the open anticline, ground- 

 water and HoS-containing oilwater are transported by gas-pres- 

 sure of the oilfield. Near the surface, the ascending water has 

 contact with oxygen-containing surfacewater. Here, at a rHa of 

 twelve to sixteen, Thiobact. tJiioparum lives in great numbers. 

 About 50 per cent of H^S and sulfides, dissolved in water, are 

 oxidized to sulfur, and the part of oxidation by Thiobact. thio- 

 pannn is about 20 per cent; the rest is chemical oxidation. During 

 diagenesis, colloidal and fine-crystallized sulfur are transformed 

 to coarse-crystallized sulfur: 



Formation of Ca sulfide 



T>, • r. If • *• CaS04-2H20^CaS 



During Desuliurication 



Solution of Colloidal 2 CaS + 2H20^Ca(OH), + Ca(HS) = 



and Fine-crystallized 



Sulfur Ca(HS), + 4 S^CaSs + H-S 



Accumulation of Coarse- 

 crystallized Sulfur and CaSj -+- CO, + H.O-^CaCOa -f 4 S + H^S 

 of Calcium Carbonate 



= 25 Zone of sulfur oxidation 

 .^ by Th. thlooxldons 



rH2 = l2-16 



"^ Zone of H S-oxidotlon to 

 ^^'rH =10 »"""•■ by Th. thioparum 



Zone of 

 desulfuricotion 



Fig. 2. Epigenetic sulfur beds of Shor-su (scheme), 



