Chemosynthesis; an alternate hypothesis for Carboniferous biotas in bryozoan/microbial mounds, Newfoundland, Canada
Chemosynthesis; an alternate hypothesis for Carboniferous biotas in bryozoan/microbial mounds, Newfoundland, Canada (in Chemosynthesis; geological processes and products, Benoit Beauchamp (convener) and Peter H. von Bitter (convener))
Palaios (August 1992) 7 (4): 466-484
Fossil tubes, stressed high-abundance low-diversity faunas, and abundant, low-temperature, hydrothermal mineralization occur in Lower Carboniferous bryozoan/microbial carbonate mounds in southwestern Newfoundland, Canada. These occurrences, set in a rift-valley setting that was tectonically active during the Carboniferous, were previously regarded as marginal marine deposits laid down in subtidal, schizohaline environments adjacent to a rocky shoreline. We suggest that they may, instead, have formed by chemosynthetic processes at low temperature marine vents at a depth of 100 m, or greater. In this explanation venting on the Carboniferous ocean floor caused biological "oases", carbonate mounds, sulphide and sulphate mineralization, as well as possible hydrocarbon formation. This hypothesis explains the location and character of the unusually well-preserved biota, the carbonate mounds containing many indications of microbial activity and the pervasive mineralization in the mounds. It addresses the lack of evidence in the mounds for higher energy and is consistent with the characteristics of the laterally correlative carbonate laminites. The discovery of identical fossil tubes in southern New Brunswick and the presence of Pb-Zn-Fe mineralization in similar carbonate mounds at the same stratigraphic level in Nova Scotia and southern New Brunswick suggest that this hypothesis may be tested throughout Atlantic Canada.