Cool-Water Carbonate Ramps: A review.

Marine, cool-water carbonate ramps considered in terms of their defining features. Cool-water carbonate environments are dominated by open, skeletal debris-covered sea bottoms which support biological assemblages devoid of hermatypic corals, calcified green algae and non-skeletal grains. The growing body of modern literature deals mainly with Neogene to Recent examples, particularly from the Australia, New Zealand and Mediterranean regions. Nevertheless, many ancient examples have be recognised and without doubt many more, currently described as ‘tropical carbonates’, will also be found to be cool-water examples. It is now becoming clear that a distinction must be made between those deposits associated with macrotidal regimes (i.e. World ocean sites) and those associated with land locked water bodies such as the Mediterranean Sea. The principle difference between the two is not so much the diversity of biota but, more importantly, the minimal fair-weather reworking processes which characterise microtidal seas. This commonly allows colonisation and sediment preservation in the inner ramp zone. Biozones occupy much deeper water sites on open ocean ramps, particularly where ramps are storm-dominated. The correspondingly wider inner ramps in these World ocean sites generally become dominated by mass bioclastic reworking.