Results of mineralogical and isotopic analyzes of sulfur and carbon in carbonate nodules and host bottom sediments and results of 14C measurement in carbonate nodules are reported. It is proved that the carbonate nodules formed 11-22 thousand years ago in anaerobic diagenesis of bottom sediments rich in organic matter. Isotopic light metabolic carbon dioxide was a source of carbonate for nodules. It formed during microbial degradation of organic matter of bottom sediments.

Supplement to: Lein, Alla Yu; Logvinenko, Nikolay V; Sulerzhitsky, Leopold D; Volkov, Igor I (1979): On the carbon source and age of diagenetic carbonate concretions from the Gulf of California. Litologiya i Poleznyye Iskopaemyye (Lithology and Mineral Resources), 14(1), 23-29