Publication Date:
2007-10-08
Description:
The pre-1980s literature on modern carbonates was biased toward tropical examples because non-tropical carbonates had not been studied extensively. Though non-tropical carbonates have received considerable attention in the past decade, the variety of low-energy, temperate ramp examples in the literature is limited. In contrast, examples of modern and ancient low-energy, tropical ramps are well represented. They are characterized by a gradual change from calcarenites updip to calcilutites downdip, by a photozoan biota, abundant non-skeletal aragonitic grains, such as ooids and peloids, and by widespread and rapid marine cementation. The Balearic Platform in the western Mediterranean is an isolated, low-energy, temperate ramp. This paper describes the Balearic ramp bathymetry, environmental regimes and depositional facies, which include (from the shoreline seaward): coastal lagoons, beach--dune complexes, inner-ramp seagrass meadows with mixed terrigenous--foraminiferal--molluscan muddy calcarenites, middle-ramp bryozoan--rhodalgal facies and outer ramp clastic--carbonate muds. Biotic and textural characteristics vary with depth, with hydrological conditions and with environmental factors, such as temperature, salinity, light and nutrients. Seagrasses extend across the inner and part of the middle ramp, where the grasses offer shelter to a variety organisms, including epibionts, molluscs, bryozoans, echinoderms and red algae. Most of the beach and dune sediments consist of bioclasts derived from the communities that thrive in the seagrass meadows, but the greatest volume of skeletal carbonates is produced as bryozoan, rhodalgal and molluscan gravels that occur as patchy blankets, primarily on the middle ramp. The Balearic Platform is characterized by an oligotrophic, clear water, microtidal environment. The dominant biota of the Balearic ramp -- bryozoans, red algae, echinoderms and molluscs -- is common in other non-tropical modern environments as well as in ancient temperate settings. This fact, combined with the absence of aragonitic non-skeletal grains, abundant marine cements and photozoans other than red algae, establishes the modern Balearic ramp as a model for comparison with low-energy, non-tropical ramps in the global rock record.
