Field and laboratory tests for recognition of Ediacaran paleosols

Retallack, Gregory J.

doi:10.1016/j.gr.2016.05.001

Cited by 47 publications

(25 citation statements)

References 158 publications

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“…Subsequent discovery of palaeosols beneath vendobiont fossils in growth position supplied evidence that they lived on Ediacaran coastal floodplains (Retallack 2013) and intertidal flats (Retallack 2016b). This palaeosol interpretation for the Ediacara Member of South Australia is based on 12 independent lines of evidence (Retallack 2016c), to which now can be added early diagenetic silica cements with Ge/Si ratios (Tarhan et al 2016) intertidal to supratidal mudflats (Retallack 2015a). Comparable coastal lagoon-margin levees and swamp woodlands are envisaged here for Protonympha (Fig.…”

Section: And Ordovicianmentioning

confidence: 90%

REASSESSMENT OF THE DEVONIAN PROBLEMATICUM PROTONYMPHA AS ANOTHER POST-EDIACARAN VENDOBIONT

Retallack

2016

Geological Society of America Abstracts With Programs

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Protonympha is an enigmatic fossil represented by two species from the Middle Devonian (Protonympha transversa) and Late Devonian (Protonympha salicifolia) of New York. Although interpreted in the past as a polychaete worm or starfish arm, Protonympha is not found with marine fossils, but with fossil plants. This fossil plant community was a swamp woodland of Lepidosigillaria whitei, with ground cover of Haskinsia colophylla, fringing brackish to freshwater coastal lagoons of the Catskill Delta. Protonympha shares with Ediacaran Vendobionta a quilted body of unskeletonized biopolymer that is unusually resistant to burial compaction. In overall form, Protonympha is most like the Ediacaran genus Spriggina. Protonympha has branching and tapering tubular structures radiating from the bottom. These rhizine-like structures, thallus stratification and internal chambers revealed by petrographic thin sections suggest affinities with lichenized fungi. As for Cambrian Swartpuntia and Ordovician-Silurian Rutgersella, Protonympha may have been a post-Ediacaran vendobiont. □ Devonian, New York, Problematicum, Protonympha, vendobiont.

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Section: And Ordovicianmentioning

confidence: 90%

REASSESSMENT OF THE DEVONIAN PROBLEMATICUM PROTONYMPHA AS ANOTHER POST-EDIACARAN VENDOBIONT

Retallack

2016

Geological Society of America Abstracts With Programs

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“…Changes in stomatal conductance due to physiological stress can result in a spread of up to 10‰ in cellulose δ 13 C and δ 18 O 57 , 60 , and our dataset spans most of that range for δ 13 C (9.3‰, Table S1 ) but indicates a much larger range for δ 18 O (17‰), which is to be expected given the large variation in source water across time and space. Biochemical oxygen isotope fractionation during cellulose synthesis can vary between 26‰ and 31‰ depending on temperature and VPD 61 , but another potential source of variation could possibly result from RuBisCO fractionation 4 (− 27‰), which may select light isotopologues of CO 2 for chemical reduction regardless of whether CO 2 is enriched or depleted with respect to heavy C or O isotopes 62 , 63 . This “ternary effect” 63 is expected to be maximized when the leaf-to-air vapour mole fraction difference is greatest and the effect is thought to be most pronounced on factors derived by the difference, most notably mesophyll resistance to CO 2 assimilation 63 .…”

Section: Discussionmentioning

confidence: 99%

“…Indeed, a fractionation of − 4.4‰ is produced by stomatal resistance to diffusion of CO 2 from the air into leaves 4 (Fig. 1) but positive covariance of δ 13 C and δ 18 O does not require stomates because it is observed in pedogenic carbonate of paleosols before the evolution of stomates 62 . Since we do not consider mesophyll conductance in the model for VPD (Fig.…”

Section: Discussionmentioning

confidence: 99%

A record of vapour pressure deficit preserved in wood and soil across biomes

Broz

Retallack

Maxwell

et al. 2021

Sci Rep

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The drying power of air, or vapour pressure deficit (VPD), is an important measurement of potential plant stress and productivity. Estimates of VPD values of the past are integral for understanding the link between rising modern atmospheric carbon dioxide (pCO2) and global water balance. A geological record of VPD is needed for paleoclimate studies of past greenhouse spikes which attempt to constrain future climate, but at present there are few quantitative atmospheric moisture proxies that can be applied to fossil material. Here we show that VPD leaves a permanent record in the slope (S) of least-squares regressions between stable isotope ratios of carbon and oxygen (13C and 18O) found in cellulose and pedogenic carbonate. Using previously published data collected across four continents we show that S can be used to reconstruct VPD within and across biomes. As one application, we used S to estimate VPD of 0.46 kPa ± 0.26 kPa for cellulose preserved tens of millions of years ago—in the Eocene (45 Ma) Metasequoia from Axel Heiberg Island, Canada—and 0.82 kPa ± 0.52 kPa—in the Oligocene (26 Ma) for pedogenic carbonate from Oregon, USA—both of which are consistent with existing records at those locations. Finally, we discuss mechanisms that contribute to the positive correlation observed between VPD and S, which could help reconstruct past climatic conditions and constrain future alterations of global carbon and water cycles resulting from modern climate change.

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“…In contrast, recent studies (Retallack, ) have alternatively proposed a terrestrial (paleosol) depositional environment for the fossiliferous Ediacara Member. Despite major issues raised and strong debate surrounding the paleosol model (e.g., Tarhan, Droser, & Gehling, ; Xiao & Knauth, ; Xiao et al., ), it has continued to play an active role in the dialogue of the geological and biological research communities (e.g., Algeo, Marenco, & Saltzman, ; Beraldi‐Campesi, ; Beraldi‐Campesi & Retallack, ; Kump, ; Pandey & Sharma, ; Retallack, , , ,b, , ,b). One of the fundamental tenets on which the paleosol model for the Ediacara Member has rested is the argument that the iron oxide coatings present on many fossiliferous horizons represent “synsedimentary ferruginization” associated with soil horizon development, and thus, a terrestrial depositional environment for the Ediacara Member (Retallack, ).…”

Section: Introductionmentioning

confidence: 99%

The late‐stage “ferruginization” of the Ediacara Member (Rawnsley Quartzite, South Australia): Insights from uranium isotopes

et al. 2017

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The paleoenvironmental setting in which the Ediacara Biota lived, died, and was pre- U values, consistent with a groundwater U source. These U isotope data thus corroborate sedimentological observations that ferric oxides along fossiliferous surfaces of the Ediacara Member consist of surficial, non-bedform-parallel staining, and sharply irregular patches, strongly reflecting post-depositional, late-stage processes.Therefore, both sedimentological and geochemical evidence indicate that Ediacara iron oxides do not reflect synsedimentary ferruginization and that the presence of iron oxides cannot be used to either invoke a terrestrial paleoenvironmental setting for or reconstruct the taphonomic pathways responsible for preservation of the EdiacaraBiota. These findings demonstrate that careful assessment of paleoenvironmental parameters is essential to the reconstruction of the habitat of the Ediacara Biota and the factors that led to the fossilization of these early complex ecosystems.

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Field and laboratory tests for recognition of Ediacaran paleosols

Cited by 47 publications

References 158 publications

REASSESSMENT OF THE DEVONIAN PROBLEMATICUM PROTONYMPHA AS ANOTHER POST-EDIACARAN VENDOBIONT

REASSESSMENT OF THE DEVONIAN PROBLEMATICUM PROTONYMPHA AS ANOTHER POST-EDIACARAN VENDOBIONT

A record of vapour pressure deficit preserved in wood and soil across biomes

The late‐stage “ferruginization” of the Ediacara Member (Rawnsley Quartzite, South Australia): Insights from uranium isotopes

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