Pollen and Spores from the Pre-Verne Cyclical Formation of the Saginaw Group, Grand Ledge, Michigan, U.S.A.

263-281http://deepblue.lib.umich.edu/bitstream/2027.42/48459/2/ID308.pd

Archaean microbiota from the Donimalai formation, Dharwar supergroup, India

Syngenetic microbial trichomes are recorded from a black chert band interlayered with the banded iron formation belonging to the > 2.6-Ga-old Sandur Schist Belt of the Dharwar sequence, Karnataka, India. The iron formation has interbeds of mafic pillow lava and tuffs. Although the fossil microbial community consists of highly biodegraded mats, some well-preserved structurally mineralized trichomes are also present. Electron microprobe analysis shows high percentage of SiO2 and P2O5 in the filaments and the presence of carbon along the margins of some filaments. Rare earth element and isotopic data indicate a higher oxygen concentration than hitherto considered for Archaean seawater. In the present context there is presumptive evidence to suggest that this oxygen was produced by the photosynthetic activity of microbial biocoenoses

Archaean stromatolites from the Chitradurga schist belt, Dharwar Craton, South India

Stromatolites have been found in the cherty dolomite member of the Vanivilas Formation of the Chitradurga Group belonging to > 2600 Ma old Archaean Dharwar Supergroup, South India. They occur in the Bhimasamudra, Marikanve and Dodguni areas of the Chitradurga schist belt. The stromatolites of the Bhimasamudra and Marikanve areas are described here for the first time. The stromatolites of Bhimasamudra consist of cylindrical and terete columns, as well as pseudocolumns with concave tops developed on a wavy base. Coalescence of columns and γ-type branching have been noticed. The Marikanve stromatolites are stratiform, often grading into pseudocolumnar and dome-shaped types. Naked stromatolite columns showing β-type and markedly divergent branching are found in the Dodguni area. The Bhimasamudra and Dodguni stromatolites probably developed in an intertidal environment and the Marikanve ones in a subtidal environment