Biogenically induced bedded chert formation in the alkaline palaeo-lake of the Green River Formation.

ABSTRACT: Rhythmically bedded cherts are observed in both pelagic marine and lacustrine deposits, but the formation mechanism in the latter remains highly uncertain. Our study of alternating chert-dolomite beds in the Eocene Green River Formation, Utah, USA reveals dense accumulations of organic-matter spheres (30-50 μm diameter) of probable algal cyst origin in the chert layers, and centennial- to millennial-scale periodicities in chert layer deposition. A positive correlation between the degree of degradation of the organic spheres and Si distribution implies decomposition of algal organic matter lead to precipitation of lacustrine chert. As both alkalinity and dissolved silica were likely high in the palaeo-lake waters of the Green River Formation, we hypothesize that decomposition of algal organ

SUBMITTER: Kuma R 

PROVIDER: S-EPMC6848130 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature