A new approach to experimental charcoal analyses: lessons for the Cretaceous and other time periods

Earth’s climate has historically oscillated between climate states, with greenhouse climate periods offering valuable analogs for future climate projections. The Cretaceous period, characterized by high atmospheric CO ₂ levels and the absence of polar ice caps, provides insights into potential ecological responses to anthropogenic climate change. This study presents experimental data to inform the use of sedimentary charcoal as a paleofire and palaeoecological proxy during the Cretaceous, supplementing the limitations of traditional palynological and fossil perspectives. Our experimental analysis includes 23 broadly sampled plant taxa, focusing on charcoal morphological classifications and a novel set of the following morphometric parameters: aspect ratio (L:W), rectangularity, circularity, and feret diameter. Our results reveal significant differences in charcoal morphometrics at the tissue (e.g., leaf, petiole) and component (e.g., vein, blade) levels, challenging the assumption that larger plant tissues produce relatively uniform charcoal particles. This emphasizes the need for refined morphometric techniques that consider plant tissues as an assemblage of their respective components. Our findings provide a nuanced framework that will improve the accuracy of future charcoal-based paleofire and paleoecology studies, particularly in pre-Holocene contexts, aiding predictions of future ecological dynamics under changing climate conditions.