Quaternary tufas of the western Potiguar Basin, Brazil: rapid xeromorphic adaptation and climate change inferred from sedimentology, paleobotany, and fossil diagenesis.

内容摘要

Quaternary tufa carbonates from Brazil's Potiguar Basin provide unique insights into the interplay of biogenic, hydrological, and climatic factors driving continental carbonate precipitation in tropical low-energy environments. This study systematically characterizes the depositional, taphonomic, and diagenetic features of the tufa deposits resulting from the dissolution of rocks from the Formação Jandaíra that overlie the lithotypes of the Formação Açu at the Quixeré locality (westernmost Potiguar Basin). We employed a multi-scalar analysis encompassing macroscopic description, petrographic thin-section analysis, scanning electron microscopy (SEM), paleobotanical analysis, and digital porosimetry. Paleobotanical analysis of leaf morphotypes quantifies a major climatic transition, from a humid tropical paleoenvironment that supported a mesophytic forest (MAT: 25.4-25.9 °C; MAP: 515-779 mm/year) to the modern xeromorphic Caatinga biome. This study indicates that the Quixeré tufas are high-resolution archives that concurrently record the sedimentological response to fluctuating depositional energy, the diagenetic pathways of continental carbonates, and the ecological turnover driven by late Quaternary aridification. The findings provide a model for interpreting tropical paleoenvironments and understanding the development of complex pore systems in heterogeneous carbonate successions.