The ratio of sulphate to chlorine is always constant (viz. 0.13648) in ordinary pelagic water. But the writer found in several bays (Heda Bay, Mera Bay, Arari Bay, Uchiura Bay, Nakagi Inlet, Nagatsuro Inlet etc.) in Izu Peninsula the fact that the ratio (SO4″ : Cl′) deviated from the standard value and showed anomalies, because sulphate being consumed owing to the activity of sulphate-reducing bacteria existed in the water. If ventilation of sea water were free, anomaly could never occur. The stagnation of a bay can happen on account of geomorphological cause, such as existence of a submarine threshold in front of a bay or enclosed topography underneath the surf ace water.
If we should be able to gain certain relation between the anomaly and inorganic sulphur contained in bottom material, the study on sedimentary rock would be brought to light, so far as sedimentational environment (anaerobic condition) is concerned.