[from :Palaeogeography, Palaeoclimatology, Palaeoecology, 134, 61-86]

The coexistence approach - a method for quantitative reconstructions
	of Tertiary terrestrial palaeoclimate data using plant fossils
	Volker Mosbruggera and Torsten Utescherb
	aInstitut für Geologie und Paläontologie der Universität Tübingen,
	72119 Tübingen, FRG
	bInstitut für Geologie, Nussallee 8, 53115 Bonn, FRG


The coexistence approach is introduced as an efficient and reliable method for quantitative terrestrial palaeoclimate reconstructions in the Tertiary. It is based on the assumption that Tertiary plant taxa have similar climatic requirements as their nearest living relatives. The aim of the coexistence approach is to find for a given fossil flora and a given climate parameter the climatic interval, in which all nearest living relatives of the fossil flora can coexist. For this purpose we have developed a databank CLIMBOT (containing for over 800 Tertiary plant taxa the nearest living relatives and their climatic requirements) and an algorithm for analysis CLIMST. For all types of fossil floras the coexistence approach thus allows the rapid quantitative reconstruction of 10 different climate parameters, including the mean annual temperature, temperature of the warmest month, temperature of the coldest month, mean annual precipitation, maximum monthly precipitation, minimum monthly precipitation, precipitation of the warmest month, relative humidity, potential evaporation, as well as the ratio of mean annual precipitation over potential evaporation. The reliability and resolution of the coexistence approach are tested with various techniques and proved to be very good; for instance, the resolution with respect to the mean annual temperature can be up to 1mC. Applications to various modern and fossil floras are illustrated and the advantages and disadvantages of the coexistence approach are discussed.