CONTROLS ON MODERN CARBONATE SEDIMENTATION ON WARM-TEMPERATURE TO ARCTIC COASTS, SHELVES AND SEAMOUNTS IN THE NORTHERN-HEMISPHERE - IMPLICATIONS FOR FOSSIL COUNTERPARTS

In contrast to the well studied tropical carbonate environments, inter est in non-tropical carbonate deposition was rather low until the basi c ideas of the FORAMOL-concept were outlined by LEES & BULLER (1972). In the following two decades studies on non-tropical carbonate setting s evolved as a new and exciting branch of carbonate sedimentology (see NELSON 1988). This is archieved in a great number of publications dea ling on temperate carbonate deposits from numerous coastal and open sh elf settings on both hemispheres. The existence of wide extended carbo nate depositional systems and even reefal frameworks in Subarctic and Arctic seas which are in focus by our research group made it possible to study modem non-tropical carbonate settings along a latitudinal tra nsect from the warm-temperate Mediterranean Sea to the cold Nordic Sea s. Because of increasing seasonality in environmental conditions towar ds high latitudes, the major controls in biogenic carbonate production can be more clearly addressed in these areas. After the initiation of the priority program ''Global and regional controlling processes of b iogenic sedimentation - evolution of reefs'' by the German Science Fou ndation four years ago, a set of modern case studies were comparativel y analysed specifically with regard to their principle controlling pro cesses: (1) Modern and Holocene coralline algal reefs and rhodolith pa vements formed in wave-protected shallow waters along the coast of the Brittany and northern Norway. Their fine-tuned interaction with herbi vores resulted in the development of widespread but low-diverse, slowl y growing coralline algal frameworks: with high competitive value agai nst the rapid-growing phaeophytic communities. (2) The Mediterranean C ladocora caespitosa-banks provide an instructive example of non-tropic al hermatypic coral framework construction out of the subtropical-trop ical coral reef belt. (3) The geometry and environmental controls of s everal kilometer long coral reefs formed by the azooxanthellate Lophel ia pertusa and Madrepora oculata are studied in more than 250 m water depth in mid and northern Norway. (4) Modern BRYOMOL-sediments are wid ely distributed on non-tropical deeper shelf settings. The formational processes converting bryozoan-thickets into huge piles of sand and gr avel dunes are recently studied on the outer shelves off northern Brit tany and off northern Norway. (5) Arctic sponge-bryozoan buildups on t he seamount Vesterisbank in the Greenland Sea and (6) balanid-dominate d open shelf carbonates on the Spitsbergen Bank form the Arctic endmem bers of modern FORAMOL-deposits. Seasonal ice-edge phytoplankton bloom s and efficient mechanisms of pelagic-benthic food transfer characteri ze these depositional settings. Fossil counterparts of each of these m odern case studies are discussed in context with their paleoceanograph ic and environmental settings.