292 BIOSEDIMENTS AND BIOFILMS Figure 12 Scanning electron microphotographs of microfossil like structures that were produced abiologically in the laboratory These ‘biomorphs’ display many complex characteristics that mimic structures of biological origin Photographs courtesy of Stephen Hyde, Australian National University Figure 13 Putative microfossil from the Apex Chert, Pilbara region, Western Australia Such structures have been interpreted as the fossilized remains of bacteria that flourished around 3.5 billion years ago Photograph courtesy of J W Schopf from the 2.5 Ga Ghaap Plateau Dolomite in South Africa and the 2.1–1.8 Ga Gunflint Formation in western Ontario, Canada These microfossils display coccoid (roughly spherical), septate filamentous, unbranched tubular, and budding bacteria-like structures (Figure 3) Biomarkers Biomarkers are biologically formed (biosynthesized) organic molecules that can be attributed to a specific biological origin They possess molecular structures and isotopic characteristics that enable them to be distinguished from abiogenic organic compounds that