Iron mineralization and taphonomy of microfossils of the 2.45–2.21 Ga Turee Creek Group, Western Australia

Snapshot of an early Paleoproterozoic ecosystem: Two diverse microfossil communities from the Turee Creek Group, Western Australia

“…X: not present or not described in study. The 3-4 μm wide straw-like (type 5) filamentous microfossils here (Figure 5a) are distinct from any of the filaments presented in Schopf et al (2015), although they are probably comparable to "type 1" filaments of Fadel et al (2017). The 3-4 μm wide straw-like (type 5) filamentous microfossils here (Figure 5a) are distinct from any of the filaments presented in Schopf et al (2015), although they are probably comparable to "type 1" filaments of Fadel et al (2017).…”

“…The first texture most commonly found within nodular black chert samples is that previously described by Schopf et al (2015) and Fadel et al (2017), of relatively long filamentous microfossils of different length and diameter, tangled in a web-like network surrounding ellipsoidal to partly polygonal domains that now consist of coarse mosaic to spherulitic microquartz ( Figure 3). The first texture most commonly found within nodular black chert samples is that previously described by Schopf et al (2015) and Fadel et al (2017), of relatively long filamentous microfossils of different length and diameter, tangled in a web-like network surrounding ellipsoidal to partly polygonal domains that now consist of coarse mosaic to spherulitic microquartz ( Figure 3).…”

“…Fadel et al (2017) identified four filamentous forms: "type 1" narrow filaments, 2-3 μm in diameter, with a thin continuous sheath (30-100 nm thick); "type 2" narrow filaments with thin central tubes (1-1.5 μm in diameter), bound by thick granular sheaths (3.5-5 μm wide) and light and dark banding along their length; "type 3" broad filaments, 3-10 μm in diameter, with thin discontinuous sheaths (50-100 nm thick); and "type 4" siderite-rich, highly degraded filaments with poorly preserved granular kerogen. Fadel et al (2017) interpreted that the iron present in these samples, in the form of siderite, ankerite and minor Fe-silicates, was originally a product of the metabolisms of Fe-oxidising micro-organisms. Similarly, Wilson et al (2010) suggested an iron-based metabolism for microfossils preserved within cherts in ironstone from the c. 1.8 Ga Duck Creek Dolomite.…”

“…Hundreds of samples of nodular and bedded black chert were collected between 22°26.291′S, 116°27.888′E and 22°31.021′S, 116°33.151′E (see green circles in Figure 1), including at the collection site of Fadel et al (2017). Hundreds of samples of nodular and bedded black chert were collected between 22°26.291′S, 116°27.888′E and 22°31.021′S, 116°33.151′E (see green circles in Figure 1), including at the collection site of Fadel et al (2017).…”

“…The DCS is a large (~20 km half wavelength), open, north-west-plunging fold structure that contains the major outcrops of the younger, c. 1.8 Ga Duck Creek Dolomite, including the well-studied Duck Creek Gorge locality ( Figure 1; Grey, 1985;Grey & Thorne, 1985;Knoll & Barghoorn, 1976;Knoll, Strother, & Rossi, 1988;Schopf et al, 2015;Walter, 1972;Wilson et al, 2010). Despite these different interpretations of the specific formation, the important point is that all researchers agree that the studied unit belongs to the TCG (e.g., Barlow et al, 2016;Fadel et al, 2017;Hickman & Van Kranendonk, 2012;Krapez, 1996Krapez, , 1999Krapez et al, 2017;Martin, 1999;Martin & Morris, 2010;Martin et al, 2000;Powell & Horwitz, 1994;Simonson, Schubel, & Hassler, 1993;Trendall, Compston, Nelson, De Laeter, & Bennett, 2004;Van Kranendonk, 2010;Van Kranendonk, Mazumder, Yamaguchi, Yamada, & Ikehara, 2015;Williford et al, 2011). Instead, Krapez et al (2017) classified the stromatolitic dolomite ridge as part of the underlying Kungarra Formation.…”