Compaction in Limestones: A Reappraisal

An important outcome of recent research on carbonate diagenesis has been the increasing realization that compaction may be as important as cementation in the lithification of carbonate sediments. Absence of compaction-deformation features should no longer be relied upon as unique evidence against compaction in limestones. The paucity of such features arises from the fact that the load-bearing capacity of allochems (grains) is hardly exceeded in the normal course of lithification of carbonate sediments. Their load-bearing capacity seems to have been exceeded only in the presence of rigid bodies (nodules) or surfaces (hardgrounds or ernersion surfaces). Wherever this prerequisite is met, compaction-deformation may be set into motion in the adjacent sediments, irrespective of their environments of deposition.

So far as the mud-supported carbonate sediments are concerned, they may undergo autolithification entirely through solution-reprecipitation without the benefit of subaerial exposure. In the case of grain-supported carbonates too, there are indications that an appreciable amount of their cement may be derived from elsewhere in adjacent rocks undergoing deeper burial diagenesis within the same basin. While burial diagenesis seems normal, subaerial diagenesis is exceptional for carbonate sediments, other than those of the nearshore areas.