摘要
An attempt has been made to document Microbially Induced Sedimentary Structure(MISS)from siliciclastic strata of the Nithar and Badalgarh Formations,Paleoproterozoic Raialo and Alwar groups of rocks in the Bayana Basin of NW India.Whereas in the Badalgarh Formation MISS are documented from shallow marine foreshore-upper shoreface succession,in the Nithar Formation,the features are recorded from fluvial deposits where the river system attained local stagnation.Unlike the dominant description of Precambrian shallow-marine MISS from sub-tidal settings,the present description highlights MISS from foreshore-upper shoreface deposits of the Badalgarh coastline.MISS are documented from field study(bedding surface)and are further proved by microscope study of thin sections.The bedding surface features include wrinkle marks,palimpsest ripple,patchy ripple,gas dome structure,desiccation cracks,and erosional remains,whereas under microscope,wavy crinkly microbial laminae with frayed edges,trapping of fine detritus in microbial filaments,flying paper effect and disseminations/clots of pyrite,in association,are documented.The biogenicity of the crinkly laminae is further checked by Raman Spectroscopy.The documented microbial structures are grouped under three categories,namely mat growth and stabilization,mat destruction,and mat burial.The Badalgarh coastline records shallowing-upward normal regressive depositional trend.In conjunction with earlier descriptions of MISS from Paleoproterzoic and Neoproterozoic successions of central and western India,the present study from northwest India establishes an overwhelming microbial influence on Precambrian siliciclastic sedimentation in Indian basins.
基金
CSIR for funding in the form of fellowship
financial support from the Institute of Eminence (IOE)
