Early Holocene charcoal accumulations in the Aktun Ha cenote: Evidence of fire used by the first settlers of the Yucatan Peninsula, Mexico

摘要

An integrative methodology, including controlled heating experiments, petrography, taphonomy, systematics of charcoal fragments, solid-state C-13 nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), and C-14 dating, are used to discriminate in situ (anthropogenic) versus transported charcoal accumulations in the Ancestors Chamber at the Aktun Ha cenote and its potential relationship with the initial settlement of the Yucatan Peninsula in Mexico. Rock heating experiments demonstrated changes in color, weight loss, and recrystallization fabrics under temperatures from 200 degrees C to 900 degrees C. At temperatures of up to 600 degrees C, calcite changed to portlandite. Taphonomic examination of the charcoal revealed that the fragments were not transported by water. Anatomical studies of the charcoal revealed the presence of species similar to modern examples used as fuel. The solid-state C-13 nuclear magnetic resonance (NMR) spectroscopy confirmed different aromatization degrees, and DSC provided information related to the hearth shape and combustion conditions throughout the thermal event. The C-14 ages determined on charcoal, 9,200 +/- 30 yr. BP (10,490-10,460 and 10,435-10,250 cal BP) and 9,440 +/- 30 yr. BP (10,740-10,585 cal BP), are similar to ages previously reported from Aktun Ha and are the oldest determined on charcoal that may have an association with human activity on the Yucatan Peninsula.