Warm Waters, Carbonates and Evaporites

Abstract

Amongst the major lithologies present within the Devonian assemblage (figure 2.1, page 21) there is a remarkable swing in the proportion of the car-bonates present. An all-time low in the Lower Devonian is wed by an increase to about 10 per cent. Mixed carbonate and clastic deposition, however, rose from about 20 per cent to over 30 per cent during the same time. The increase appears to be largely at the expense of marine clastics. The change, accompanied by diversification of the marine faunas, was in keeping with world geographical changes. In this chapter we briefly survey some aspects of carbonate and evaporite deposition and their distribution within, and their importance for, the Devonian world (see figure 8.7).