Permineralized Fossils from the Terminal Proterozoic Doushantuo Formation, South China

Abstract

Permineralized fossils of the terminal Proterozoic (600–550 Ma) Doushantuo Formation, China, provide an unusually clear window on biological diversity just before the Ediacaran radiation. In the eastern Yangtze Gorges region, cherts in lower and upper Doushantuo carbonates preserve prokaryotes and protists from subtidal marine environments below and above fair weather wave base, respectively. Phosphorites in the Weng'an district to the south contain diverse acanthomorphic acritarchs as well as cellularly preserved thalloid algae. Twelve taxa of probable cyanobacteria are recognized. None is endemic to the Doushantuo Formation, and most have long stratigraphic ranges. The apparent restriction of two species to late Neoproterozoic and Cambrian rocks may reflect secular variation in taphonomic circumstance rather than evolution. Thirty-one species of spheromorphic and acanthomorphic acritarchs are recognized, about half of which occur elsewhere in rocks of the same approximate age. At least some of the eight formally described species of multicellular algae can be assigned with confidence to the Rhodophyta; these fossils provide a glimpse of structural and reproductive diversity in Neoproterozoic algae that is, to date, unique. Several reports of Doushantuo animal fossils have been published; most compelling are triact spicules identified in chert nodules. Along with more than two dozen taxa of compressed macrofossils preserved in carbonaceous shales from the top of the formation, Doushantuo permineralizations indicate that large animals radiated into a world rich in prokaryotic, protistan, and, even, multicellular diversity.

New material of microfossils from the Ediacaran Doushantuo Formation in the Zhangcunping area, Yichang, Hubei Province and its zircon SHRIMP U-Pb age

“…The new microfossils consist of acritarchs (including 6 genera and 7 species, they are Asterocapsoides sinensis, Echinosphaeridium maximum, Ericiasphaera speldeaesii, Leiosphaeridia tenuissima, Meghystrichosphaeridium perfectum, Tianzhushania spinosa, and T. ornata), multi-cellular algae (Sarcinophycus papilloformis) and filamentous cyanobacteria (Oscillatoriopsis obtusa) ( Figure 2). All of these new microfossils generally occur in silicified biota from both members II and III of the Doushantuo Formation in the Yangtze Gorges [2,[4][5][6][19][20][21][22] . Apart from acritarchs Ericiasphaera speldeaesii and multi-cellular algae Sarcinophycus papilloformis, others generally occur in the phosphatized biota from the upper part of the Doushantuo Formation at Weng'an, Guizhou Province [23][24][25][26] .…”

“…Apart from acritarchs Ericiasphaera speldeaesii and multi-cellular algae Sarcinophycus papilloformis, others generally occur in the phosphatized biota from the upper part of the Doushantuo Formation at Weng'an, Guizhou Province [23][24][25][26] . Besides, the multi-cellular algae Paratetraphycus giganteus and Wengania globosa, which reported from the Doushantuo Formation in Zhangcunping before [15] , also occur from the upper part of the Doushantuo Formation at Weng'an [6] . Thus, the microfossil assemblage of the Doushantuo Formation in the Zhangcunping area shows similarity with both the phosphatized biota at Weng'an and the typical silicified biota in the Yangtze Gorges.…”

“…These members are, in ascending stratigraphic order, (1) cap dolostone overlying glacial diamictite of the Cryogenian (Nanhuan) Nantuo Formation; (2) black shale intercalated with medium-bedded muddy dolostone, with abundant chert nodules; (3) medium-bedded dolostone with chert nodules or lenticles and banded limestone; and (4) black shale with large dolostone concretions. Abundant silicified microfossils (micrometers to millimeters) had been reported from chert nodules or lenticles in both Members II and III [1][2][3][4][5][6] . In addition, Chuaria-like carbonaceous compressions and a dichotomously branching algal thallus were found in black shale of Member II at Jiulongwan [7] (Figure 1) and the black shale in the Member IV at Miaohe (Figure 1) contains abundant algal and possible metazoan macroscopic carbonaceous compressions [8][9][10] .…”

“…Besides, the age of the Doushantuo Formation has been constrained between 635.2±0. 6 from the interbedded ash beds [11][12][13][14] .…”

Methane seeps, methane hydrate destabilization, and the late Neoproterozoic postglacial cap carbonates

“…Abundant acanthomorph acritarchs, multicellular algae, and cyanobacteria have been found in the phosphorite-chert nodules shortly after the Doushantuo cap carbonate [158,159] ; some of them have been reported to be only ~2 m above the Doushantuo cap carbonate [160] . Important aspects include the recovery history of organisms in the post-cap carbonate ocean from platform to basin and evidence for land organisms in strata younger than overlying cap carbonates.…”