Carbonate lithofacies as paleolatitude indicators: problems and limitations

Detailed study of Miocene carbonates in the Mediterranean region and their analogues on modern carbonate shelves (in the Mediterranean Sea, Brazil and other areas) reveals at least three major types of carbonate platform lithofacies in addition to the classic tropical coral reef (chlorozoan) lithofacies: (a) chloralgal lithofacies, similar to the chlorozoan, but without hermatypic corals; (b) rhodalgal lithofacies, characterized by abundant encrusting coralline algae; and (c) molechfor lithofacies, consisting of benthic foraminifers, molluscs, echinoids, bryozoans and barnacles. These carbonate lithofacies present complex distribution patterns seemingly related primarily to latitude and depth that control water temperature, although other factors (e.g., water circulation, river discharge, suspended sediment) controlling water salinity and temperature, nutrient content, light penetration, etc., also play important roles. Chloralgal and rhodalgal lithofacies can be considered two transitional terms between the two end-members: the chlorozoan lithofacies, which characterizes shallow tropical shelves; and the molechfor lithofacies, which characterizes colder and/or deeper areas. Detailed textural and sequential analysis are required for satisfactory interpretation of these lithofacies in ancient rocks.