Age of the Guatemala breccias around the Cretaceous-Tertiary boundary: relationships with the asteroid impact on the Yucatan

Abstract The upper part of the near K/T boundary limestone breccia deposits which crop out in Guatemala near 16 °N contains impact remains: altered glass spherules (tektites) and elevated concentrations of iridium. This suggests that these deposits could result from the impact of the K/T boundary asteroid on the Yucatan. However, their matrix contains foraminifers of the Eugubina Zone and calcareous nannofossils of the CP1a Zone, an association characterizing Early (but not the earliest) Danian. This unusual assemblage of K/T and Danian components suggests that the upper part of the breccia was reworked several thousands of years after the K/T event.