Flocculent layers and bacterial mats in the mudstone interbeds of the Primary Lower Gypsum unit (Tertiary Piedmont basin, NW Italy): Archives of palaeoenvironmental changes during the Messinian salinity crisis

Abstract

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Potential Fossilized Sulfide-Oxidizing Bacteria in the Upper Miocene Sulfur-Bearing Limestones From the Lorca Basin (SE Spain): Paleoenvironmental Implications

“…Filamentous and rod-shaped morphologies similar to those found in Lorca are a common feature of carbonate (Schreiber, 1978; Guido et al, 2007; Oliveri et al, 2010; Ziegenbalg et al, 2010; Dela Pierre et al, 2012, 2014; Natalicchio et al, 2013; Caruso et al, 2015; García-Veigas et al, 2015; Perri et al, 2017) and gypsum (Vai and Ricci Lucchi, 1977; Panieri et al, 2010; Schopf et al, 2012; Dela Pierre et al, 2015) layers deposited in the Mediterranean region during the late Miocene. Their origin is, however, controversial, since they have been attributed to both fecal pellets (Schreiber, 1978; Guido et al, 2007; Natalicchio et al, 2013; García-Veigas et al, 2015), algae (Vai and Ricci Lucchi, 1977) and remains of prokaryotes such as cyanobacteria (Rouchy and Monty, 1981, 2000; Martin et al, 1984; Panieri et al, 2010) and sulfide-oxidizing bacteria (Oliveri et al, 2010; Schopf et al, 2012; Dela Pierre et al, 2012, 2014, 2015; Perri et al, 2017). To shed light on the origin of these enigmatic microstructures, and especially on the affiliation of the putative microbial fossils, two requirements must be preliminary discussed: (1) the distinction between fecal pellets and the supposed prokaryotic microfossils; (2) the validation of the criteria proving the biogenicity of microbial fossils (Schopf and Walter, 1983; Buick, 1990; Cady, 2001; Cady et al, 2003; Schopf et al, 2005; Westall, 2008; Summons et al, 2011).…”

“…Another common feature of the upper Miocene limestones is the almost completely absence of macrofossils, which is believed to result from harsh environmental conditions (e.g., hypersalinity, anoxia) lethal for most eukaryotes (e.g., Bellanca et al, 2001; Blanc-Valleron et al, 2002). In contrast, these rocks are typified by peculiar assemblages of filamentous, circular and rod-shaped microstructures of controversial origin: remains of algae (Vai and Ricci Lucchi, 1977) or bacteria (Oliveri et al, 2010; Dela Pierre et al, 2012, 2014; Caruso et al, 2015; Perri et al, 2017), fecal pellets of brine shrimps ( Artemia salina ) adapted to hypersaline conditions (e.g., Schreiber, 1978; Natalicchio et al, 2013; García-Veigas et al, 2015) or of copepods (Guido et al, 2007) thriving in a normal marine water column, thus excluding the presence of hypersaline conditions. The distinction of the predominating group of precursor microorganisms beyond these enigmatic structures is fundamental to assess the environmental conditions in the water column and on the bottom of the basin during deposition and early diagenetic phase.…”

The upper Miocene diatomaceous sediments of the northernmost Mediterranean region: A lamina‐scale investigation of an overlooked palaeoceanographic archive

“…Diatoms and diatom moulds have been also reported from other deposits of the Piedmont Basin, such as in the bottom‐grown gypsum crystals (e.g. Dela Pierre et al ., 2015; Carnevale et al ., 2019) and the interbedded organic‐rich shales (Dela Pierre et al ., 2014) from the Primary Lower Gypsum unit that represent the first phase of the MSC (Dela Pierre et al ., 2011). The poor preservation of diatoms in the MSC organic‐rich mudstones is particularly interesting in light of the ambiguity of the ‘anoxic paradigm’, i.e.…”

“…According to palaeogeographic and palaeoceanographic reconstructions (e.g. Dela Pierre et al ., 2014), the Piedmont Basin was a sort of semi‐isolated gulf, where the late Miocene diatomaceous accumulation took place during the progressive restriction of the connection between the Mediterranean and the Atlantic Ocean (e.g. Kouwenhoven et al ., 1999), coupled to an ongoing increase in riverine runoff (e.g.…”

Genomic features of “Candidatus Venteria ishoeyi”, a new sulfur-oxidizing macrobacterium from the Humboldt Sulfuretum off Chile

“…e ., a highly diverse community of big filamentous and spherical non-photosynthetic sulfur-oxidizing bacteria [ 5 ], and small Archaea, might have been the only or the dominant types of life in primeval ocean bottoms when free oxygen was lacking or scarce [ 5 , 7 ]. Paleontological, geological, and geochemical evidence from this habitat and its biota have been reported from the Archaean and Proterozoic Eons [ 8 – 10 ], and from late Miocene (Tertiary), Italian mudstone beds [ 11 ]. We further posit that such evidence might still be present in the late Jurassic (Oxfordian), “proto-Humboldt Sulfuretum”-derived fossil-bearing deposits in northern Chile’s “Cordillera Domeyko” [ 12 ].…”