Comparison of Foraminiferal, Coccolithophorid, and Radiolarian Paleotemperature Equations: Assemblage Coherency and Estimate Concordancy

The Imbrie-Kipp method of paleotemperature estimation is rigorously tested by comparing Atlantic temperature equations independently derived from the microfossils of three biotic groups: the Foraminifera, Coccolithophorida, and Radiolaria. This method consists of two steps: factor analysis of the modern sea-bed data of the individual groups which resolves discrete biogeographic assemblages and regression analysis of the modern assemblage data with observed sea-surface temperature data to obtain paleotemperature equations. Assemblage biogeography shows a simple subdivision into warm (low latitude) and cold (high latitude) for all biotic groups. Between biotic groups there is greater similarity among high-latitude assemblages than low-latitude ones. Correlating the assemblage data with observed sea-surface temperatures to produce temperature distribution patterns shows differences of less than 2°C in their optimum and critical temperatures. Regression analysis produced accurate temperature equations for each biotic group, all with standard errors of estimate of less than or equal to 2°C. Multiple correlation coefficients were all greater than 0.970. Applying these equations to two multiple biotic data sets (the modern and ice-age sea-bed data) and comparing their temperature estimates using the standard error pooled, shows over 87% concordancy for both data sets. Unlike the modern data, the discordancy among temperature estimates of the ice-age data shows a distinct geographic distribution; its cause is believed to be oceanographic, a difference in the water-mass structure between the modern and ice-age ocean.