Chapter 8 Biostratigraphy and stratigraphic subdivision of Cryogenian successions of Australia in a global context

Grey, Kathleen; Hill, Andrew C.; Calver, Clive R.

doi:10.1144/m36.8

Cited by 35 publications

(17 citation statements)

References 80 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Microfossil assemblages from the Kanpa Formation in the Empress‐1A drill core also show similarities to those in the Chuar Group (Grey et al ., ), most notably the presence of Cerebrosphaera buickii , a species found in the lower members of the Chuar Group (Nagy et al ., ) and whose first appearance, ca. 800 Ma, has been suggested as a possible global stratigraphic marker (Grey et al ., ). Thus, despite the wide paleogeographic separation, the eukaryotic fossil assemblages of the Visingsö and Kanpa are similar to the Chuar.…”

Section: Discussionmentioning

confidence: 89%

Early sponges and toxic protists: possible sources of cryostane, an age diagnostic biomarker antedating Sturtian Snowball Earth

et al. 2015

View full text Add to dashboard Cite

The period 800-717 million years (Ma) ago, in the lead-up to the Sturtian Snowball glaciation, saw an increase in the diversity of eukaryotic microfossils. To afford an independent and complementary view of this evolutionary period, this study presents the distribution of eukaryotic biomarkers from three pre-Sturtian successions across the supercontinent Rodinia: the ca. 780 Ma Kanpa Formation of the Western Australian Officer Basin, the ca. 800-740 Ma Visingsö Group of Sweden, and the 740 Ma Chuar Group in Arizona, USA. The distribution of eukaryotic steranes is remarkably similar in the three successions but distinct from all other known younger and older sterane assemblages. Cholestane was the only conventional structure, while indigenous steranes alkylated in position C-24, such as ergostane, stigmastane, dinosterane and isopropylcholestane, and n-propylcholestane, were not observed. This sterane distribution appears to be age diagnostic for the pre-Sturtian Neoproterozoic. It attests to the distinct evolutionary state of pre-Snowball eukaryotes, pointing to a taxonomic disparity that was still lower than in the Ediacaran (635-541 Ma). All three basins also show the presence of a new C28 sterane that was tentatively identified as 26-methylcholestane, here named cryostane. The only known extant organisms that can methylate sterols in the 26-position are demosponges. This assignment is plausible as molecular clocks place the appearance of the earliest animals into the pre-Sturtian Neoproterozoic. The unusual 26-methylsterol may have protected sponges, but also other eukaryotes, against their own membranolytic toxins. Some protists release lytic toxins to deter predators and kill eukaryotic prey. As conventional membrane sterols can be the site of attack for these toxins, sterols with unusual side-chain modification protect the cell. This interpretation of cryostane supports fossil evidence of predation in the Chuar Group and promotes hypotheses about the proliferation of eukaryophagy in the lead-up to the Cryogenian.

show abstract

Section: Discussionmentioning

confidence: 89%

Early sponges and toxic protists: possible sources of cryostane, an age diagnostic biomarker antedating Sturtian Snowball Earth

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Similar approaches have been conducted on the basis of morphological differences of stromatolites, providing a more precise interpretation of their paleoenvironmental context (Schopf, 1977;Bertrand-Sarfati and Walter, 1981;Allwood et al, 2006;Grey et al, 2011;Collins, 2012, 2013). Morphological relief does not necessarily correlate with an increased bioproductivity, however, it can be assumed that it indicates an increased biomass accumulation.…”

Section: Biostratigraphy and Paleoecologymentioning

confidence: 99%

Morphological adaptations of 3.22 Ga-old tufted microbial mats to Archean coastal habitats (Moodies Group, Barberton Greenstone Belt, South Africa)

Homann

Heubeck

Airo

et al. 2015

Precambrian Research

110

View full text Add to dashboard Cite

a b s t r a c tMicrobial life was well established and widespread by the Paleoarchean; however, the degree of evolutionary advancement such as microbial motility, intra-and inter-species interactions, phototropism, or oxygenic photosynthesis by that time remains highly debated. The 3.22 Ga Moodies Group in the Barberton Greenstone Belt (BGB, South Africa) are Earth's oldest well-preserved siliciclastic tidal deposits. They exhibit a unique assemblage of microbial mats, providing an excellent opportunity to decipher the morphological adaptations of microbial communities to different paleoenvironmental settings. The fossil mats are preserved as kerogenous laminations (0.5-1 mm thick) that can be traced laterally for ∼15 km in a ∼1000 m-thick succession of fine-to coarse-grained tidal sandstones and conglomerates. We here present a detailed stratigraphic and depositional facies analysis, documenting the association of the three principal mat morphotypes with specific environmental settings: (1) planar-type in coastal floodplain, (2) wavy-type in intertidal, and (3) tufted-type in upper inter-to supratidal facies. All mat types indicate a flourishing phototrophic biota; moreover, the tufted morphology suggests an intricate level of coordinated growth commonly known from cyanobacterial mats in modern environments.

show abstract

“…There is no obvious (or not obvious, either) "interstromatolite" sediment, which frequently appears lithologically different, especially when weathered, in unequivocally stromatolitic deposits (cf. Grey et al, 2011). In some areas, especially under layers that are unfolded, the "interstromatolite" area is fi lled with a breccia including platy fragments, often with a very high aspect ratio, that are typically planar (Fig.…”

Section: Please Do Not Use Hammers At This Outcrop Which Is Uniquementioning

confidence: 99%

Neoproterozoic Glacial and Associated Facies in the Tanafjord-Varangerfjord Area, Finnmark, North Norway

Rice¹,

Edwards²,

Hansen³

2012

Neoproterozoic Glacial and Associated Facies in the Tanafjord-Varangerfjord Area, Finnmark, North Norway

View full text Add to dashboard Cite

This excursion guide describes the glacigenic rocks of the Smalfjord and Mortensnes Formations, and parts of the intervening Nyborg Formation, at the base of the Vestertana Group in the Tanafjord-Varangerfjord region of East Finnmark, NorthNorway. These are agreed to be either of glacial (sensu lato) origin or signifi cant to our understanding of Neoproterozoic glacial processes and events. The Smalfjord and Mortensnes Formations have been equated with the Marinoan (636.3 ± 4.9 Ma and 635.5 ± 1.2 Ma) and Gaskiers (584-582 Ma) glaciations, respectively. The rocks, which are superbly exposed, display a wide range of sedimentary lithologies/facies; lodgment, banded, deformation, fl ow, and melt-out diamictites; as well as glaciomarine, proglacial, and fl uvioglacial sediments. Diamictites derived from carbonate units showing the Trezona and Wonoka negative δ 13 C anomalies are seen.Glaciotectonic and/or soft-sediment structures described include folds, normal and thrust faults (imbricate fans), fl anking structures, shear-sense criteria (sigma clasts), striations (with paleoloess), lobate-cuspate contacts, downward intrusion of fl uidized sediments (with bridge structures), pro-and subglacial channels, nested channels, graded beds, possible iceberg dump structures, ghost clasts, dropstones and lonestones, allochthonous rafts of substrate sediments, ball-and-pillow structures, convolute laminations (pseudonodules), delta foresets, ice-crystal molds, sandstone dikes, and a possible kettle hole. The complex geometry of the sub-Smalfjord unconformity onto older Neoproterozoic sediments and the Archean Baltic Shield is documented at several scales. Marinoan cap dolostones (Maieberg negative δ 13 C anomaly), with typical sheet cracking (and "pseudostromatolites") and atypical clastic interbeds, are described from the base of the Nyborg Formation at several localities.

show abstract

Chapter 8 Biostratigraphy and stratigraphic subdivision of Cryogenian successions of Australia in a global context

Cited by 35 publications

References 80 publications

Early sponges and toxic protists: possible sources of cryostane, an age diagnostic biomarker antedating Sturtian Snowball Earth

Early sponges and toxic protists: possible sources of cryostane, an age diagnostic biomarker antedating Sturtian Snowball Earth

Morphological adaptations of 3.22 Ga-old tufted microbial mats to Archean coastal habitats (Moodies Group, Barberton Greenstone Belt, South Africa)

Neoproterozoic Glacial and Associated Facies in the Tanafjord-Varangerfjord Area, Finnmark, North Norway

Contact Info

Product

Resources

About