Terrestrial paleoclimate proxies based on paleosols have proliferated over the past two decades. The results of this study provide a much-needed test of the numerous paleoclimate proxies by crosschecking of the results provided by minerals within a single basin and, in some instances, a single paleosol profile. In addition, the results of this study should provide information that help to determine which geochemical proxies are least likely to survive into the geological record. To that end, this research documents the pedogenic and post-pedogenic history of the minerals contained within paleosols, determines which geochemical proxies of paleoclimate are most likely to be retained in spite of burial, and which of these provide a robust and quantitative record of Late Triassic paleoclimate in the Ischigualasto basin of southern Pangea.
This research is directed by two main objectives: (1)Documentation of the mineralogical composition, stable isotopic composition, and 40Ar-39Ar ages of minerals contained within paleosols in order to delineate the temporal framework of mineral crystallization and the utility of a particular mineral as a proxy of paleoenvironment. The minerals of interest include phyllosilicates, oxyhydroxides and carbonates, as these are common pedogenic minerals and are abundant within the geological record. (2) To reconstruct the evolution of Late Triassic atmospheric PCO2 from multiple mineralogical proxies and elucidate any robust trends between changing atmospheric green house gas concentrations and other paleoclimate parameters such as paleotemperature and paleoprecipitation.
Paleoclimate studies of 'deep-time' geologic records provide compelling evidence for repeated, abrupt intervals of global warming or cooling, and transitions between extreme climate states. Many of these climate events triggered significant biotic turnover and led to wholesale changes in biogeochemical cycling. Moreover, recent developments have fueled a debate over the validity of the pCO2-climate paradigm over the past half billion years. These issues parallel the climate change debate of concern at present, thus highlighting the need to fully understand Earth's climate system and its variability. The development of marine and terrestrial paleoclimate archives at equal spatial and temporal resolution is critical to documenting the global nature of such large-scale environmental perturbations, and to characterizing the full range of Earth climate-system dynamics. In total, the importance of this research transcends any one place or time (i.e., Late Triassic of Argentina), because this study provides a better understanding of just how useful paleosols may be for paleoclimate reconstructions in general.
