Famennian microbial reef facies, Napier and Oscar Ranges, Canning Basin, western Australia

Abstract

Following the Frasnian–Famennian mass extinction, which eliminated most skeletal reef‐building fauna, the early Famennian reefs of the Canning Basin were constructed primarily by reef‐framework microbial communities. In the Napier and Oscar Ranges, the Famennian reef complexes had high‐energy, reef‐flat depositional environments on a reef‐rimmed platform that transitioned into low‐energy, deep‐water reefs growing in excess of 50 m below sea level. High‐energy, reef‐flat depositional environments contain doming fenestral stromatolites that grade into porous thrombolites and are associated with coarse‐grained sandstones and grainstones. The reef‐margin subfacies contains mounds of microdigitate thrombolites, which are more delicate than the reef‐flat thrombolites and locally contain abundant red algae, Girvanella, renalcids and sediment‐filled tubes. Within the thrombolites, the red algae are in upright growth positions, suggesting that the thrombolites are largely composed of carbonate that precipitated in situ. Reefal‐slope environments are dominated by Wetheredella and Rothpletzella with locally abundant Girvanella, renalcids and Uralinella. In reefal‐slope strata, delicate fans and microdigitate stromatolites of Wetheredella and Rothpletzella are often oriented horizontal or diagonal to bedding and are interpreted as syndepositionally toppled over. Most mesoscale microbial community structures contain several species of microbial fossils, and no single microbial species appears to have controlled the morphology of the community structure. Therefore, the depositional environment must have determined the distribution and morphology of the stromatolites, thrombolites and other microbial community structures. The adaptability of microbial communities to various reef environments allowed them to fill ecological niches opportunistically after the Frasnian–Famennian mass extinction.

Tube structures of probable microbial origin in the Neoarchean Carawine Dolomite, Hamersley Basin, Western Australia

“…The Devonian Canning Basin ‘sand tubes’ are 3–15 cm in diameter, up to 1 m long, and filled with siliciclastic sand and grainstones (Kerans et al ., 1986; George & Powell, 1997; Playford, 2000; Stephens & Sumner, 2003). These ‘sand tubes’ have sharp walls that are coated by up to 1 cm of Renalcis and other calcified microbes that grew into the tube center but not into the host sediment or water column (Stephens & Sumner, 2003).…”

Mid-late Devonian calcified marine algae and cyanobacteria, South China

“…1, p. 37), are locally prominent components of oncoids, stromatolitic deposits and reefs in both the Frasnian and early Famennian (Chuvashov and Riding, 1984). They are generally well documented in the Frasnian from the Canning Basin (Wray, 1967;Playford et al, 1976;Webb, 1996, p. 953;George, 1999), Alberta (Mountjoy and Riding, 1981), and southern China (e.g., Shen et al, 2005Shen et al, , 2008, and from the early Famennian in the same areas (e.g., Playford, 1984;Wood, 2000;Stephens and Sumner, 2003;Whalen et al, 2002;Shen et al, 1997;Webb, 2004a, 2004b). However, it has proved difficult to establish whether they actually increased in absolute abundance from Frasnian to Famennian or simply were made more conspicuous by demise of metazoan reef-builders such as stromatoporoids and corals.…”

Thrombolite fabrics and origins: Influences of diverse microbial and metazoan processes on Cambrian thrombolite variability in the Great Basin, California and Nevada

“…Some thrombolites contain evidence of metazoan activity, which may also influence thrombolite development and fabrics (e.g. Aitken, ; Pratt & James, ; Read & Pfeil, ; Walter & Heys, ; Stephens & Sumner, , ). Thus, thrombolites provide a record of sediment–organism interactions from the Precambrian and throughout the Phanerozoic.…”