Chemical weathering proxies: An assessment of their robustness to reconstruct Paleozoic climate conditions

Abstract

Several chemical weathering proxies for siliciclastic sedimentary deposits have been proposed over the last fifty years. However, only a few studies have evaluated their robustness for paleoclimate interpretation. Here, we compile published geochemical data for the Early Cambrian to Late Permian to statistically assess the robustness of weathering intensity proxies, as well as to account for biases that may affect the paleoclimatic interpretations. A principal components analysis (PCA) was conducted to assess the reliability of 15 chemical weathering proxies, considering paleoclimate categories inferred for each sedimentary succession. We test the consistency of our PCA model with independent datasets of Permian sedimentary rocks and modern soils. The distribution of paleoclimate categories follows a trend on the PC-1 axis, from arid conditions on the positive side to humid climates on the negative side. Modern soil samples show a similar distribution on the PC-1 axis, corroborating the interpretation that the first dimension of PCA in paleorecords is linked to chemical weathering intensity. Therefore, we suggest that all proxies represented by the PC-1 axis are suitable for chemical weathering intensity reconstructions, and, consequently, paleoclimate interpretations. However, it is necessary to consider other controlling factors that can affect the chemical weathering signal in deep-time siliciclastic sedimentary deposits, such as provenance, hydraulic sorting, diageneses, and recycling.