Microbial cements in Holocene beachrocks of South Andaman Island, Bay of Bengal

Holocene beachrocks from the South Andaman Islands, India exhibit early cementation, which was greatly influenced by microbial activity. Studies suggest that microbes (fungi and bacteria) play an important and active role in carbonate beachrock cementation. The microbial cement occurs as needle-fibre growth, fungal filaments and relating borings and calcispheres; however the needle-fibre cement is most abundant. The needle-fibre cement forms dense patchy meshwork on the allochems and occurs either as single or paired microrods. At places, the needles also show rhombic overgrowths. The morphological variations of the microbial cement in the beachrock highlight the immense scope for studies in this less-understood branch of geology carbonate geomicrobiology.