Microbialites and global environmental change across the Permian–Triassic boundary: a synthesis

Abstract

Permian-Triassic boundary microbialites (PTBMs) are thin (0.05-15 m) carbonates formed after the end-Permian mass extinction. They comprise Renalcis-group calcimicrobes, microbially mediated micrite, presumed inorganic micrite, calcite cement (some may be microbially influenced) and shelly faunas. PTBMs are abundant in low-latitude shallow-marine carbonate shelves in central Tethyan continents but are rare in higher latitudes, likely inhibited by clastic supply on Pangaea margins. PTBMs occupied broadly similar environments to Late Permian reefs in Tethys, but extended into deeper waters. Late Permian reefs are also rich in microbes (and cements), so post-extinction seawater carbonate saturation was likely similar to the Late Permian. However, PTBMs lack widespread abundant inorganic carbonate cement fans, so a previous interpretation that anoxic bicarbonate-rich water upwelled to rapidly increase carbonate saturation of shallow seawater, post-extinction, is problematic. Preliminary pyrite framboid evidence shows anoxia in PTBM facies, but interbedded shelly faunas indicate oxygenated water, perhaps there was short-term pulsing of normally saturated anoxic water from the oxygen-minimum zone to surface waters. In Tethys, PTBMs show geographic variations: (i) in south China, PTBMs are mostly thrombolites in open shelf settings, largely recrystallised, with remnant structure of Renalcis-group calcimicrobes; (ii) in south Turkey, in shallow waters, stromatolites and thrombolites, lacking calcimicrobes, are interbedded, likely depth-controlled; and (iii) in the Middle East, especially Iran, stromatolites and thrombolites (calcimicrobes uncommon) occur in different sites on open shelves, where controls are unclear. Thus, PTBMs were under more complex control than previously portrayed, with local facies control playing a significant role in their structure and composition.

Role and lifestyle of calcified cyanobacteria (Stanieria) in Permian–Triassic boundary microbialites

“…It is generally 2 to 10 m thick and consists of two parts (Kershaw et al, 1999(Kershaw et al, , 2007(Kershaw et al, , 2012Lehrmann, 1999;Ezaki et al, 2003Ezaki et al, , 2008Wang et al, 2005Wang et al, , 2012Jiang and Wu, 2007a,2007bYang et al, 2011). The lower part consists of gray limestone with scattered irregular brown spots 0.5 to 1.5 cm wide, and has been described as spotted rock.…”

“…Many previous studies have also documented the presence of very small (b0.05 mm) coccoid fossils in these microbialites (Ezaki et al, 2003(Ezaki et al, , 2008Wang et al, 2005;Yang et al, 2011;Kershaw et al, 2012), and related them to cyanobacteria. Some researchers (Ezaki et al, 2003) suggested that the precursor microbes of the coccoid fossils formed the mesoclots constituting the microbialites.…”

The Phanerozoic δ88/86Sr record of seawater: New constraints on past changes in oceanic carbonate fluxes

“…Accordingly, we argue that the massive carbonate formation suggested by our δ 88/86 Sr sw record and related model results was sustained and possibly triggered by BSR, producing large amounts of alkalinity in anoxic waters and sediments. This hypothesis could also explain the inorganic precipitation of sea-floor CaCO 3 cements that are observed in Late Permian reef complexes and Early Triassic carbonate platforms and pelagic plateaus (Grotzinger and Knoll, 1995;Kershaw et al, 2011;Knoll et al, 1996;Riding and Liang, 2005;Woods et al, 1999). The long lasting anoxic conditions may have been supported and amplified by a combination of additional factors, such as global warming (Wignall and Twitchett, 2002), a stagnant and stratified ocean (Knoll et al, 1996), and long term high nutrient fluxes to the oceans from the weathering of coal-swamp deposits ( Fig.…”

A Review on Microbialites: a Korean Perspective

“…그러나 데본기 후 기 대멸종 이전에도 상당수의 미생물초가 존재하였기 때문에, 이 시기에 미생물초가 번성했던 것에는 대멸 종 이외에도 다른 이유가 있을 수 있다 (Feng et al, 2010;Shen et al, 2010). 페름기 말 대멸종 직후 약 150만 년에서 500만 년에 걸쳐 주로 Renalcis 그룹 또는 Microcystis로 생각되는 미생물과 미크라이트로 구성된 미생물암이 전 세계적으로 널리 나타났다 (Kershaw et al, 1999(Kershaw et al, , 2012Ezaki et al, 2003;Wu et al, 2014). 이 시 기의 미생물암은 주로 저위도 지역의 다양한 퇴적 환 경에 분포하였으며 (Kershaw et al, 2012), 트라이아 스기 중기 이후 후생동물 생태계가 대멸종의 타격에 서 점차 회복되면서 크게 감소하였다 (Xie et al, 2010;Brayard et al, 2011).…”

“…페름기 말 대멸종 직후 약 150만 년에서 500만 년에 걸쳐 주로 Renalcis 그룹 또는 Microcystis로 생각되는 미생물과 미크라이트로 구성된 미생물암이 전 세계적으로 널리 나타났다 (Kershaw et al, 1999(Kershaw et al, , 2012Ezaki et al, 2003;Wu et al, 2014). 이 시 기의 미생물암은 주로 저위도 지역의 다양한 퇴적 환 경에 분포하였으며 (Kershaw et al, 2012), 트라이아 스기 중기 이후 후생동물 생태계가 대멸종의 타격에 서 점차 회복되면서 크게 감소하였다 (Xie et al, 2010;Brayard et al, 2011). 이후 쥐라기 중후기 및 백악기 초기에 주로 쓰롬볼 라이트와 스트로마톨라이트로 구성된 미생물암이 상 대적으로 흔하게 나타나며, 이들은 얕은 바다에서는 산호와, 깊은 바다에서는 해면동물과 함께 생물초를 형성하였다 (Leinfelder et al, 1993(Leinfelder et al, , 1994Dupraz and Strasser, 1999;Parcell, 2002;Olivier et al, 2003Olivier et al, , 2006Bádenas and Aurell, 2010).…”