Direct Dating Links 3.5-Billion-Year-Old Life Signs to Their Rock
A study on a carbon-rich chert from India's Singhbhum Craton directly ties biosignatures to a precise age: uranium–lead dating of zircon crystals embedded in the rock centers the deposit at about 3.497 billion years ago, with four of eight zircons yielding consistent ages around 3.5 Ga. Complementary Raman spectroscopy and carbon-isotope analysis show a laminated carbon layer with isotopic signatures indicative of ancient biology, supporting the interpretation of a microbial mat preserved in a volcanically active, iron- and silica-rich early Earth environment. The findings provide robust, embedded dating for ancient life and are published in PNAS 2026.
