Sedimentary 7 A Chlorites

Rohrlich, et al.. 1969 Gaertner and Schellmann, 1965 Leclalre, 1968 Giresse and Odin, 1973) at fairly shallow depths ( 80 meters). These reactions take place under saline or estuarine conditions. The transformation of sediment into berthierine is apparently progressive the initial sedimentary material found in shell tests becomes gradually transformed into a single phase, 7 chlorite structure. 

One aspect of sedimentary 7 8 chlorite formation which is particularly interesting is the fact that these minerals are never found forming at depths greater than 80 meters in recent sediments. Porrenga (1967b) thinks that they are characteristic of tropical sediments and their formation is thus temperature dependent. This appears invalid since they are known to form in recent sediments in a Scottish loch (Rohrlich, e al.. 1969). Nevertheless there does seem to be a bathymetric control on their occurrence. This is probably not a pressure effect but more likely some sort of factor related to organic activity in the sediments which is controlled by the biotic factors of sea depth, temperature, nutrients, etc. 

In addition to proper biotic factors, it appears that the oxidation state of the iron in the sediment is critical to the formation of sedimentary 7 8 chlorites these conditions are more reducing than those which form glauconites (Porrenga, 1967b Leclaire, 1968). As is the case for 

This has been seen in interstitial waters of marine sediments (Brooks, 

The change between 7 and 14 8 has been noted to occur at incipient 

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