Quaternary paleoenvironments based on pedogenic, sedimentary and karstic processes in the coastal geosystems of Cozumel Island, Mexico

Abstract

The Quaternary carbonatic deposits of the Cozumel Island are mainly reefs and calcarenites in which karstic features, red clayey paleosols and layers of calcretes provide a record of terrestrial paleoenvironments still poorly explored. A main section, Cantera Payo, and three complementary sections: Cantera Transversal, Aerolito and Chempita were studied. Besides field work, micromorphology, physicochemical and mineralogical analyses of soils and calcretes were done. C and O stable isotope analysis was also conducted in calcretes. The cyclicity of sedimentary, karstic and pedogenetic processes was established. The chronological frame was obtained through the correlation dated calcretes and coral samples from Yucatan Peninsula, with ages ranging between ∼Marine Isotope Stage (MIS) 7 to MIS 1. Two paleo-karstic surfaces were identified, labeled as PK1 (older) and PK2 (younger). The PK1 surface showed multi-face karst features as collapse breccias, dissolution pits and pipes, and karstic pockets filled with lithified brown and red paleosols. The red paleosols exhibited abundant redoximorphic features. Clay mineralogy in paleosols and modern soil is similar, with vermiculite and minerals of the kaolinite group. We interpret they are the result of moderate weathering under a seasonal tropical climate like that of present-day conditions. PK1 is capped by a calcrete layer, whose age probably corresponds to the Marine Isotope Stage (MIS) 6 (164 a 135 ka). Therefore, the host rock and the karstification and pedogenetic processes should occur before (probable during MIS 7) The stable carbon isotope composition of this calcrete has a mean δ13C value of −10.40 ‰ that suggests the presence of a C3 plant cover. During the MIS 5, poorly cemented calcarenites accumulated in the island related to the sea level rise during this interglacial stage. This calcarenite level has less developed karstification and pedogenetic processes. Another laminar calcrete with root traces and septal alveolar structure is found on top of the studied sections formed in the MIS 5 and the transition to MIS 4. Its δ13C value ranges between −9.40 ‰ and − 10.27 ‰ also related to a C3 plant cover. In the period between MIS 4 and MIS 1, karst development and pedogenesis is observed on the island, evidenced by the formation of caves and reddish-brown soils.