THE COEXISTENCE APPROACH - A METHOD FOR QUANTITATIVE RECONSTRUCTIONS OF TERTIARY TERRESTRIAL PALEOCLIMATE DATA USING PLANT FOSSILS

The coexistence approach is introduced as a method for quantitative te rrestrial palaeoclimate reconstructions in the Tertiary. It is based o n the assumption that Tertiary plant taxa have similar climatic requir ements to their nearest living relatives, The aim of the coexistence a pproach is to find for a given fossil flora and a given climate parame ter the climatic interval in which all nearest living relatives of the fossil flora call coexist. For this purpose we have developed a data base, CLIMBOT (containing for over 800 Tertiary plant taxa, the neares t living relatives and their climatic requirements) and an algorithm f or analysis; CLIMST. For all types of fossil floras the coexistence ap proach thus allows the rapid quantitative reconstruction of 10 differe nt climate parameters, including the mean annual temperature, temperat ure of the warmest month, temperature of the coldest month, mean annua l precipitation, maximum monthly precipitation, minimum monthly precip itation, precipitation of the warmest month, relative humidity, potent ial evaporation: as well as the ratio of mean annual precipitation ove r potential evaporation. The reliability and resolution of the coexist ence approach are tested with various techniques and proved to be reas onably good; for instance, the resolution with respect to the mean ann ual temperature can be up to l-C. Applications to various modern and f ossil floras are illustrated and the advantages and disadvantages of t he coexistence approach are discussed. (C) 1997 Elsevier Science B.V.