Charcoal morphotypes and potential fuel types from a Mexican lake during MIS 5a and MIS 3

Charcoal particles vary in size and form, but they can preserve morphological characteristics used to infer the type of vegetation being burnt. To deduce potential fuel and fire type, we reconstructed local fire activity analyzing macrocharcoal morphologies and pollen data of the sediment core CHA08-V from Lake Chalco from the sub-stage MIS 5a to MIS 3, with CHAR data and Z-Score analysis. We identified the following fuel types: i) wood, characterized by blocky and quadrilateral morphologies with solid, foliated or striated surface textures; ii) grass, represented by rectangular-porous and rectangular-latticed morphologies; and iii) herbs, characterized by long-thin filaments and polygonal porous particles. Arboreal pollen components were associated to wood morphotypes whereas non-arboreal pollen related to herbs and grass morphotypes, indicating that variation in vegetation composition was important regulating factor determining fire types in the Basin of Mexico. This study provides the first long-term record of charcoal morphotypes for Mexico region to emphasize the importance of charcoal morphotypes analyses to complement paleoenvironmental interpretation of past fire regimes.