Article: Ecological succession in intraformational hardground formation

A review of discontinuity hardgrounds shows that an ecological succession can be recognized accompanying the gradual increase in lithification. The burrowing, boring, and encrusting biota is divided into five groups: soft to firm substrate burrowers, animals that penetrate firm or cemented substrates, borers restricted to cemented substrates, non-restricted encrusters on firm to cemented substrates, and encrusters restricted to cemented substrates. The type of ecological succession present depends on the lithology, and four types of hardground are recognized reflecting differences in lithification potential: calcarenite, calcirudite, calcilutite with very low clay content, and calcilutite with about 2% clay.