Early middle triassic stromatolites from the luoping area, yunnan province, southwest china: Geobiologic features and environmental implications

摘要: Abstract An early Middle Triassic stromatolite deposit is documented from the Guanling Formation of Luoping area, Yunnan, SW China. The shows five types constructional microbial forms in various magnifications: 1) typical stratified columnar structures, up to 20 cm high, with crinkled laminae. Dark coloured laminae, 1 mm thick, are composed upright filamentous tubes, averagely 29.4 μm diameter, showing a vertical growth fabric. 2) Laminoid fenestrae, 0.5–1 mm wide, and 3) prostrate filaments, which reflected by strong fluorescence sharp contrast dolomite cement fluorescent images. 4) Rod-like aggregates, 4.6–18 μm minute rhombs, very common stromatolitic laminae; they resemble present-day cyanobacterial trichome, thus may represent putative fossilized cyanobacteria. 5) Moreover, small pits, coccoid-like spheroids, calcified biofilms, fibrous structures also last two extracellular polymeric substances (EPS) that contributed development lithification stromatolites. Authigenic quartz grains have involved biological processes formation. Of these functional-groups driving accretion literature, both lithified cyanobacteria/oxygenic phototrophs possible sulfate-reducing bacteria (SRB), induced formation stromatolite, suggestive biogenic origin. differs Permian–Triassic boundary microbialites (PTBMs) having abundant growing an oxic marine environment. Both sedimentary facies analysis cyanobacteria indicate proliferation oxygenic normal, habitat during middle Anisian (early Triassic), period when hospitable environments, coupled biotic diversification, prevailed South China set agenda for full recovery ecosystems middle–late Anisian. However, post-extinction stromatolites other anachronistic not necessarily indicative anoxic or conditions, their environmental settings much more complex than previously thought.