Microbialite recovery in the aftermath of the Sturtian glaciation: Insights from the Rasthof Formation, Namibia

Ber, E. Le; Heron, Daniel Paul Le; Winterleitner, Gerd; Bosence, Dan; Vining, B. A.; Kamona, Fred

doi:10.1016/j.sedgeo.2013.05.003

Cited by 20 publications

(10 citation statements)

References 40 publications

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“…The coin is 2 cm in diameter. Roll-ups are associated with neptunian dikes and indicate that biomats were cohesive and pliable ( 475 , 478 ), but the metabolic basis for their growth, inferentially below the photic zone, remains undetermined. ( D ) Macropeloids and low-angle cross-stratification in characteristically organic-poor Marinoan cap dolostone, Keilberg Member of the Maieberg Formation, northern Namibia ( 97 ).…”

Section: Cap Carbonates and Snowball Earth Aftermathsmentioning

confidence: 99%

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Snowball Earth climate dynamics and Cryogenian geology-geobiology

et al. 2017

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Section: Cap Carbonates and Snowball Earth Aftermathsmentioning

confidence: 99%

“…In Namibia, they are hosted in the lower HST by a bizarre succession of likely nonphototrophic stromatolites and microbialaminites ( Fig. 25C ) with neptunian dikes and early void-filling cements ( 442 , 475 , 478 , 479 ). Sturtian and Marinoan cap carbonates are distinct and distinctive.…”

Section: Cap Carbonates and Snowball Earth Aftermathsmentioning

confidence: 99%

Snowball Earth climate dynamics and Cryogenian geology-geobiology

et al. 2017

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“…The cyclic occurrence of dolomite in alkaline Lake Van provides a unique analogue potentially helpful for interpreting Neoproterozoic alkaline oceans and related dolomite formation, which share similar features beyond deposition in an alkaline carbonate saturated environment (Kempe & Kazmierczak, ). These include dolomite within finely laminated (Le Ber et al, ) and fabric preserving sediments (Hood et al, ), its association with deglacial highstand deposits (Hoffman et al, ), anoxic conditions (Font et al, ), possible cold‐water precipitation (Pokrovsky et al, ), and cyclic changes between dominance of dolomite and calcium carbonate (Tojo et al, ). The comparison between Lake Van's dolomite and ancient dolomite might prove valuable in constraining some of the important issues discussed for cap dolomite formation, such as warm (Nédélec et al, ) versus cold (Pokrovsky et al, ) water temperatures, oxidation state (Font et al, ) and timescales of dolomite formation, and Neoproterozoic deglaciation (Hoffman et al, ).…”

Section: Implications For Geological Recordsmentioning

confidence: 99%

Controls on Cyclic Formation of Quaternary Early Diagenetic Dolomite

McCormack

Bontognali

Immenhauser

et al. 2018

Geophysical Research Letters

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The origin of sedimentary dolomite and the factors that control its formation within the geological record remain speculative. In most models, dolomite formation is linked to evaporative conditions, high water temperature, increasing Mg/Ca ratio, increasing alkalinity, and high amounts of biomass. Here we challenge these archetypal views, by documenting a case example of Quaternary dolomite which formed in Lake Van at constantly low temperature (<4°C) and without direct control of the latter conditions. Dolomite occurs within highstand sediments related to suborbital climate variability (Dansgaard‐Oeschger cycles). We propose that dolomite precipitation is a product of a microbially influenced process, triggered by ecological stress, resulting from reventilation of the water‐sediment interface. Independently from the validity of this hypothesis, our results call for a reevaluation of the paleoenvironmental conditions often invoked for early diagenetic dolomite‐rich intervals within sedimentary sequences and for caution when interpreting time series of subrecent lacustrine carbonates.

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“…Like the Marinoan cap, the Sturtian cap in Namibia (Rasthof Formation) displays carbon‐isotope evidence of diachronous deposition during deglaciation for at least the basal part of the cap (Pruss et al ., ). Microbialite sedimentation continues for >150 m thickness, with vertical trends in stromatolite and thrombolite architecture presumably charting recovery of cyanobacterial communities during fluctuating energy levels (Le Ber et al ., ), while δ 13 C continues to rise to +5‰ (Pruss et al ., ).…”

Section: Glaciation and Its Aftermathmentioning

confidence: 99%

Sedimentological perspectives on climatic, atmospheric and environmental change in the Neoproterozoic Era

2016

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Sedimentological insights underpin many of the important recent advances in understanding of Earth system behaviour in the Neoproterozoic Era. This article reviews three main areas: (i) chemical proxies and their preservation, with emphasis on carbonate facies; (ii) glacial and post-glacial facies, including their age constraints; (iii) sedimentary evidence for biotic innovations and responses. Chemostratigraphy plays an important role in ordering Neoproterozoic events and defining disturbances to the carbon cycle. There is increasing attention being paid to assessing the role of diagenetic origination or modification of chemostratigraphic signals. Alongside this, new criteria for identifying primary dolomite and precursor metastable phases such as ikaite have been developed. In respect of oxygenation, geochemical proxies substantiate the concept of a Neoproterozoic Oxygenation Event as a very gradual transition, the ocean being at any one time a heterogeneous assemblage of ferruginous, sulphidic and oxic conditions, with some evidence of increasing deep-sea oxidation through the Ediacaran Period. Techniques such as Fe-speciation need to be supplemented with proxies sensitive to suboxic conditions. More generally, it is predicted that petrographically constrained microanalytical studies will also become more important in reconstructing palaeoenvironmental conditions. The global distribution of Neoproterozoic glacial deposits combined with palaeomagnetic evidence supports the concept of panglaciations in which ice sheets reached sea-level in the tropics. Advances in radiometric dating have demonstrated the synchronous onset of global (Sturtian) glaciation at 717 Ma and the demise of a second (Marinoan) glaciation at 635 Ma, and plausibly indicate long durations for each (55 Myr for Sturtian and 5 to 15 Myr for Marinoan). However, a compilation of radiometric dates indicates ambiguities indicating the need for further improvements to the radiometric and Sr-isotope database to understand events within the Sturtian time frame, the timing of onset of Marinoan glaciations, and the age and synchroneity of individual negative d 13 C anomalies. Sturtian deposits are typically thick, rift-related successions containing a range of environments influenced or dominated by dynamic glaciers, as well as ice-free marine intervals. Marinoan glacial deposits, by contrast, tend to be thin and continental. During the latter interval, oxygen isotope systematics of sulphate demonstrate that atmospheric CO 2 was high, as predicted by Snowball Earth theory, and that sedimentation was influenced by orbital forcing. The Sturtian record, by comparison, needs to be searched for evidence of cold-climate hiatuses on the one hand and orbital forcing on the other. Cap carbonate formation appears to have coincided with rising sea-levels following panglaciations. Snowball theory considers that they formed rapidly in the postglacial greenhouse, but an alternative (2016) 63, 253-306 doi: 10.1111/sed.12261 STATE OF THE SCIENCE model o...

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Microbialite recovery in the aftermath of the Sturtian glaciation: Insights from the Rasthof Formation, Namibia

Cited by 20 publications

References 40 publications

Snowball Earth climate dynamics and Cryogenian geology-geobiology

Snowball Earth climate dynamics and Cryogenian geology-geobiology

Controls on Cyclic Formation of Quaternary Early Diagenetic Dolomite

Sedimentological perspectives on climatic, atmospheric and environmental change in the Neoproterozoic Era

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