TEMPERATE CARBONATES ON A MODERN, LOW-ENERGY, ISOLATED RAMP - THE BALEARIC PLATFORM, SPAIN

This paper presents a depositional model for a temperate, low-energy c arbonate ramp based on descriptive studies of five areas around the Ba learic Islands of Mallorca and Menorca. This low-energy ramp differs s ignificantly from other present-day temperate carbonate platforms that are primarily high energy open shelves. It is characterized by the fo llowing lithofacies (from shore to basin): (1) lagoon, (2) barrier isl and, (3) shallow subtidal, (4) inner ramp, (5) middle ramp, and (6) di stal ramp. Subaqueous carbonate dunes are present near slope breaks of f Menorca and Cabrera, but they are not representative of the entire r amp. Balearic ramp sediments differ in composition, texture, biology, and degree of cementation from those on modern low-energy, tropical ra mps. Balearic ramp carbonates lack ooids and peloids, hermatypic coral buildups, and calcareous green algae (except in one restricted bay wh ere Halimeda is relatively common). Red algal sands and gravels extend to depths of up to 90 m, and are coarser than their strandplain-equiv alent lime sands, Skeletal allochems consist of the bryomol-rhodalgal association, marine cementation is rare, and the carbonate fraction of deep-water muds is mainly Mg-calcitic and calcitic in composition, Ar agonite is rare, Except for the red alga Peyssonnelia, which is compos ed of aragonite, it is neither a dominant skeletal constituent nor com mon as a cement. The Mediterranean Sea off Mallorca and Menorca is a l ow energy, temperate, oligotrophic, clear-water environment. The depos itional model for the region is an isolated platform configured as a h omoclinal ramp, Ancient counterparts of the Balearic ramp are present in the Neogene of the Mediterranean Tethys and the Paratethys, and tho ugh the constituents of fossil assemblages vary with time, the biota o f the Balearic ramp, such as bryozoans, red algae, echinoderms, and mo llusks, ranges from the Paleozoic Era to the present, Echinodermal bry omols passing to basinal muds on carbonate ramps are particularly char acteristic of the Early Carboniferous in North America and Europe. Thi s suggests that the Balearic Islands temperate ramp may be more repres entative of some ancient carbonate sequences than either temperate, hi gh-energy, open shelves or tropical ramps in the present oceans.