scholarly journals A rare disc-like holdfast of the Ediacaran macroalga from South China

2017 ◽  
Vol 91 (6) ◽  
pp. 1091-1101 ◽  
Author(s):  
Ye Wang ◽  
Yue Wang ◽  
Wei Du
Keyword(s):  
Water Column ◽  
Marine Environment ◽  
South China ◽  
Tissue Differentiation ◽  
Black Shales ◽  
Low Energy ◽  
Doushantuo Formation ◽  
Phylogenetic Affinity

AbstractThe fixing organ of the Precambrian macroalga was briefly described by most researchers as a holdfast or rhizoid, suggesting a fixation structure and/or tissue differentiation. An Ediacaran macroscopic alga, Discusphyton whenghuiensis n. gen. n. sp., with a complex disc-like holdfast and an unbranching thallus, has been collected, together with abundant and diverse macrofossils (i.e., the Wenghui biota) in black shales of the upper Doushantuo Formation (~560–551 Ma) in northeastern Guizhou, South China. The Wenghui biota lived in a relatively low-energy marine environment and was preserved in situ or nearby their growth position. Morphologically, the macroalgal thallus, including the compressed lamina and cylindrical stipe, might have been suspended in the water column for photosynthesis. Its holdfast, a rare fixing form, is complex in structure and construction, consisting of a globular rhizome and a discoidal rhizoid. The large-sized discoidal rhizoid is regarded as a flat-bottomed and dome-shaped organ to attach the macroalga on the water-rich muddy seafloor. The globular rhizome, expanded by a thallus on the substrate, was originally harder and spherical nature within the dome-shaped rhizoid. It may have been an important organ as a steering knuckle to connect between the stipe and the rhizoid. The macroscopic metaphyte D. whenghuiensis n. gen. n. sp. shows the appearance of complex holdfast in morphology and bio-functions. However, not enough is known, in the absence of more information, to decipher the phylogenetic affinity of D. whenghuiensis n. gen. n. sp. and the origin of a discoidal rhizoid.

Origin of chert nodules in the Ediacaran Doushantuo Formation black shales from Yangtze Block, South China

2020 ◽  
Vol 114 ◽  
pp. 104227 ◽  
Author(s):  
Ping Gao ◽  
Zhiliang He ◽  
Gary G. Lash ◽  
Shuangjian Li ◽  
Rongqiang Zhang
Keyword(s):  
South China ◽  
Black Shales ◽  
Yangtze Block ◽  
Doushantuo Formation

A predominantly ferruginous condition in the Ediacaran deep ocean: Geochemistry of black shales in the Ediacaran Doushantuo Formation, South China

2017 ◽  
Vol 295 ◽  
pp. 12-23 ◽  
Author(s):  
Jing Huang ◽  
Lianjun Feng ◽  
Xuelei Chu ◽  
Tao Sun ◽  
Hanjie Wen ◽  
...  
Keyword(s):  
South China ◽  
Deep Ocean ◽  
Black Shales ◽  
Doushantuo Formation

Paleoecology of a well-preserved nautiloid assemblage from a Late Ordovician shale unit, southwestern Ohio

1989 ◽  
Vol 63 (5) ◽  
pp. 604-620 ◽  
Author(s):  
Robert C. Frey
Keyword(s):  
North America ◽  
Marine Environment ◽  
Benthic Communities ◽  
Late Ordovician ◽  
Low Energy ◽  
Eastern North America ◽  
Sea Mud ◽  
Recurrent Nature ◽  
Water Depths

A diverse, well-preserved assemblage of nautiloid cephalopods was collected from the Treptoceras duseri shale, a 1.5-m-thick claystone within the Waynesville Formation (Late Ordovician, early Richmondian) exposed in southwest Ohio. The strata, the enclosed fauna, and its taphonomy indicate deposition in a low-energy, mud-bottom marine environment, in water depths of 20–25 m, below wave base but within the zone of storm-current reworking.Nautiloid specimens consist of complete conchs that have been replaced by calcite. Twelve species of nautiloids, belonging to eight genera, representative of four orders, have been collected from the shale in southwest Ohio. Longiconic orthocones are clearly the dominant nautiloid morphotype present, with the assemblage dominated by three species of the longiconic orthocerid Treptoceras and with fewer numbers of the endocerid Cameroceras and the slender orthocerid Isorthoceras?, the cyrtoconic oncocerids Oncoceras and Manitoulinoceras, and rare specimens of the orthocerid Gorbyoceras, the oncocerid Zittelloceras, and the ascocerid Schuchertoceras.Nautiloid taphonomy, the diversity of nautiloid taxa present, the lack of postmortem buoyancy in the shells of the more common taxa, the recurrent nature of this assemblage, and the restricted distribution of this Treptoceras–Cameroceras fauna to portions of eastern North America in the Late Ordovician suggest that this nautiloid assemblage represents an in-situ accumulation of nautiloids representative of a living assemblage. These nautiloids were important elements associated with benthic communities in these epeiric sea mud-bottom environments and not simply assemblages of drifted, necroplanktonic shells.

SYSTEMATIC DESCRIPTION AND PHYLOGENETIC AFFINITY OF TUBULAR MICROFOSSILS FROM THE EDIACARAN DOUSHANTUO FORMATION AT WENG’AN, SOUTH CHINA

Palaeontology ◽  
2008 ◽  
Vol 51 (2) ◽  
pp. 339-366 ◽  
Author(s):  
PENGJU LIU ◽  
SHUHAI XIAO ◽  
CHONGYU YIN ◽  
CHUANMING ZHOU ◽  
LINZHI GAO ◽  
...  
Keyword(s):  
South China ◽  
Doushantuo Formation ◽  
Phylogenetic Affinity ◽  
Systematic Description

Re–Os geochronology of black shales from the Neoproterozoic Doushantuo Formation, Yangtze platform, South China

2013 ◽  
Vol 225 ◽  
pp. 67-76 ◽  
Author(s):  
Bi Zhu ◽  
Harry Becker ◽  
Shao-Yong Jiang ◽  
Dao-Hui Pi ◽  
Mario Fischer-Gödde ◽  
...  
Keyword(s):  
South China ◽  
Black Shales ◽  
Yangtze Platform ◽  
Doushantuo Formation

Silicified tubular microfossils from the Upper Doushantuo Formation (Ediacaran) in the Yangtze Gorges area, South China

2009 ◽  
Vol 83 (4) ◽  
pp. 630-633 ◽  
Author(s):  
Pengju Liu ◽  
Shuhai Xiao ◽  
Chongyu Yin ◽  
Feng Tang ◽  
Linzhi Gao
Keyword(s):  
South China ◽  
New Genus ◽  
Black Shales ◽  
New Genus And Species ◽  
Doushantuo Formation ◽  
Environmental Distribution

The ediacaran Doushantuo Formation in the Yangtze Gorges area (Fig. 1.2) contains abundant silicified cyanobacterial coccoids and filaments (Y. Zhang et al., 1998), acanthomorphic acritarchs (Zhou et al., 2007), multicellular algae (Xiao, 2004), and possible animal embryos (L. Yin et al., 2007). These silicified fossils are taxonomically similar to the phosphatized fossils in the Doushantuo Formation of the Weng'an area, South China (Y. Zhang et al., 1998). However, the Weng'an assemblage contains tubular microfossils that have not been previously documented in the Yangtze Gorges area. Here we report the occurrence of secondarily silicified tubular microfossils—Sinocyclocyclicus guizhouensis(Xue et al., 1992) andYangtzitubus semiteresnew genus and species—from lenticular cherts in the upper Doushantuo Formation in the Yangtze Gorges area. Of the two named taxa,Sinocyclocyclicus guizhouensiswas previously known from the Weng'an area (Liu et al., 2008). The new data extend the geographic, taphonomic, and environmental distribution of Doushantuo tubular microfossils. A fuller documentation of the Doushantuo biodiversity is also important to the evaluation of possible taphonomic or environmental biases among the three exceptional taphonomic windows—carbonaceous compression (Xiao et al., 2002), phosphatization (Xiao and Knoll, 1999), and silicification (Y. Zhang et al., 1998)—in Doushantuo black shales, phosphorites, and cherts, respectively.

The Carbon:²³⁴Thorium ratios of sinking particles in the California Current Ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model

2019 ◽  
Author(s):  
Michael Stukel ◽  
Thomas Kelly
Keyword(s):  
Organic Carbon ◽  
Water Column ◽  
Particulate Organic Carbon ◽  
Transport Model ◽  
California Current ◽  
In Situ Measurements ◽  
Power Law Distribution ◽  
Sinking Particles ◽  
Organic Carbon Concentration

Thorium-234 (234Th) is a powerful tracer of particle dynamics and the biological pump in the surface ocean; however, variability in carbon:thorium ratios of sinking particles adds substantial uncertainty to estimates of organic carbon export. We coupled a mechanistic thorium sorption and desorption model to a one-dimensional particle sinking model that uses realistic particle settling velocity spectra. The model generates estimates of 238U-234Th disequilibrium, particulate organic carbon concentration, and the C:234Th ratio of sinking particles, which are then compared to in situ measurements from quasi-Lagrangian studies conducted on six cruises in the California Current Ecosystem. Broad patterns observed in in situ measurements, including decreasing C:234Th ratios with depth and a strong correlation between sinking C:234Th and the ratio of vertically-integrated particulate organic carbon (POC) to vertically-integrated total water column 234Th, were accurately recovered by models assuming either a power law distribution of sinking speeds or a double log normal distribution of sinking speeds. Simulations suggested that the observed decrease in C:234Th with depth may be driven by preferential remineralization of carbon by particle-attached microbes. However, an alternate model structure featuring complete consumption and/or disaggregation of particles by mesozooplankton (e.g. no preferential remineralization of carbon) was also able to simulate decreasing C:234Th with depth (although the decrease was weaker), driven by 234Th adsorption onto slowly sinking particles. Model results also suggest that during bloom decays C:234Th ratios of sinking particles should be higher than expected (based on contemporaneous water column POC), because high settling velocities minimize carbon remineralization during sinking.

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