Accretion, trapping and binding of sediment in archean stromatolites - Morphological expression of the antiquity of life

This paper reviews and discusses Archean stromatolite occurrences and their modes of growth in the context of sedimentary facies. Modes of sediment accretion and trapping and binding of sedimentary grains, together with the resulting morphology of stromatolites and microbial mats in the Archean are analysed, in order to show existing interaction between the growth patterns, morphology and facies association. Architectural elements of sediment arrangement in Archean stromatolites, together with the dependence of stromatolite distribution and morphology on sedimentary facies changes, clearly argue for a biological origin of stromatolitic lamination preserved in Archean cherts and carbonates. The observed sediment behaviour of laminae accretion and sediment precipitation, trapping and binding cannot be explained by abiogenic carbonate or silica precipitation from saturated solutions. The time-dependent, increasing complexity of stromatolitic structures in the Archean is an additional strong argument for biologic impact on stromatolite formation. Therefore, biogenic stromatolites and microbial mats were undoubtfully present at 3.5 Ga and occupied an increasingly wide range of sedimentary environments during the Archean.