Evidence of the hypsithermal verified using the racemization rate constant of amino acids: An estimation of paleo-ground temperatures

The kinetics of a racemization reaction for aspartic acid in boreal terrestrial sediment core samples was investigated in detail to determine the rate constant (k(ASP)) and the difference of the paleo-ground temperatures. The Arrhenius plot between the rate constant (k(ASP)) and the literature data of corresponding temperatures is defined as Log k(ASP) = 16.1 - 5820/T where T is the absolute temperature (K). From the beginning of the Holocene, estimated annual ground temperatures increased to reach the warmest period, after which a slight decrease was observed. The present findings are geologically consistent with the global transgression period called "the Hypsithermal".