Direct dating of 3.5 Ga biogenic carbon in a microbial mat remnant, Singhbhum Craton, India
Abstract
Zircons interpreted to be of syn-volcanic origin recovered from the lower greenschist “black and white banded” Bhitardari chert, Eastern Iron Ore greenstone belt, Singhbhum craton, India, yield a 207 Pb/ 206 Pb zircon age of 3497 ± 5 Ma ( n = 4; MSWD = 1.2). This chert contains abundant carbonaceous matter (CM) that occurs in two textural modes: 1) ultrafine laminae distributed within the matrix and 2) graphite flakes in late quartz veins. Bulk δ 13 C CM of both modes in the Bhitardari chert yield a value of −30.9‰, which we interpret as reflecting a biogenic origin. This represents the documentation of a directly dated, CM-bearing, Paleoarchean rock with δ 13 C CM diagnostic of biologic activity. The observed isotopic compositions are consistent with the rise of relatively sophisticated metabolic mechanisms (e.g., Calvin cycle) by 3.5 Ga.
Fields of Study & Subjects
Paleontology and Stratigraphy of Fossils
Geological and Geochemical Analysis
Geochemistry and Elemental Analysis
Publication details
- Journal / source
- Proceedings of the National Academy of Sciences
- Publisher
- National Academy of Sciences
- Volume
- 123
- Issue
- 34
- Pages
- e2617912123–e2617912123
- Publication date
- 17 August 2026
- Language
- EN