In situ U-Pb dating and Sr isotropic fingerprinting of Quilon Limestone, Kerala Basin, India: constraints on Miocene carbonate deposition and paleogeography

Abstract

This study provides the first direct in situ U-Pb age for the Quilon Limestone in the Kerala Basin, integrating carbonate-cement geochronology with in situ ⁸⁷ Sr/ ⁸⁶ Sr isotope data. Laser ablation inductively coupled plasma mass spectrometry analyses yield a consistent lower-intercept age of 17.6 ± 1.3 Ma, placing deposition within the Early Miocene (Burdigalian). Slightly radiogenic Sr signatures indicate minor siliciclastic input during carbonate precipitation. The combined isotopic framework suggests short-lived carbonate deposition under reduced terrigenous influx and supports correlation with contemporaneous Sri Lankan carbonate platforms, reflecting Early Miocene sea-level fluctuations and regional paleogeographic connectivity.