Proliferation of MISS-forming microbial mats after the late Neoproterozoic glaciations: Evidence from the Kimberley region, NW Australia

Abstract

A total of 20 morphological types of microbially induced sedimentary structures (MISS) are recognized from the late Neoproterozoic tillite-bearing successions of the Kimberley, northwestern Australia which include alpha-petees, triradiate cracks, multidirectional linear ridges, millimeter ripples, erosional remnants and pockets and so on. Of these, triradiate cracks, multidirectional linear ridges, and millimeter ripples are reported for the first time from the Neoproterozoic worldwide. Most Kimberley MISS are morphologically comparable with their ancient and present-day counterparts whose biogenicity have been well demonstrated.In the Kimberley, during the interglacial period MISS have colonization preference to relatively coarse sandy substrates (Ranford Formation) and their abundance decreased towards the younger strata (Throssell Shale). In contrast, MISS abundance increased from the older strata (Yurabi Formation) towards the younger strata (Flat Rock Formation) during the postglacial period. However, overall, both MISS abundance and bedding plane coverage percentage increased from the Marinoan-younger Marinoan/Gaskiers interglacial successions to younger Marinoan/Gaskiers postglacial successions, indicating a proliferation of microbial mats after the younger Marinoan/Gaskiers glaciation. The increase of microbial mats could have ameliorated marine biogeochemical conditions and ecosystems, and thus laid the foundation for the rise of Ediacaran biota in Australian basins.