Disentangling Diagenesis From the Rock Record: An Example From the Permo‐Triassic Wordie Creek Formation, East Greenland

Roberts, Jenny; Turchyn, Alexandra V.; Wignall, P. B.; Newton, Robert J.; Vane, Christopher H.

doi:10.1002/2017gc007259

Cited by 6 publications

(3 citation statements)

References 38 publications

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“…In contrast to this regional trend, the East Greenland Fiskegrav section had lower overall δ 15 N values prior to the LPE, and does not show any significant change across the extinction event (Mettam et al, 2017). This likely reflects the highly restricted nature of the East Greenland Basin, which was separated from wider Panthalassa ocean circulation during Late Permian time (Mettam et al, 2017;Roberts et al, 2018). East Greenland was thus not affected by regional upwelling prior to the LPE, nor changes to N delivery after the extinction.…”

Section: Early Triassic Nitrogen Limitationmentioning

confidence: 81%

Global warming leads to Early Triassic nutrient stress across northern Pangea

et al. 2019

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The largest extinction in Earth history, in the latest Permian, was followed throughout most of the Early Triassic by a prolonged period of ecologic recovery. What factors delayed biotic recovery are still under debate and partly revolve around impacts of global warming on primary marine productivity. We examined N isotope records from the Festningen section on Spitsbergen, Arctic Norway, to examine changes in nutrient availability through the Early to Middle Triassic along the northern margin of Pangea. Our results show progressive decline in N availability throughout the Griesbachian, leading to severe nutrient limitations through the remainder of the Early Triassic, until returning to a highly productive continental margin in Middle Triassic time. These results are consistent with other studies from northern and western Pangea and thus show regional nutrient limitations occurred in what should have been the main zone of marine primary productivity. Such nutrient limitation likely stressed primary production and consequently contributed to prolonged marine recovery. We suggest this was driven by high ocean temperatures depressing the marine nutricline.

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Section: Early Triassic Nitrogen Limitationmentioning

confidence: 81%

Global warming leads to Early Triassic nutrient stress across northern Pangea

et al. 2019

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“…A similar diagenetic condition was reported for the Brent Group of the North Sea with a burial depth of 2500–3500 m 43 , 44 . The δ 18 O value of T 1 b pore water is likely to have increased by the same value (about 4‰) as the Brent Group from that of the initial meteoric water (−10 to −8‰) to −6 to −4‰ 44 – 46 . Using this δ 18 O value, we calculated that the temperature was greater than 90 °C during formation of more than 85% of the total calcite, with a background temperature range of 90–135 °C and an average of 109.6 °C (see Supplementary Data 2 ), consistent with the temperatures estimated from the geothermal gradient.…”

Section: Discussionmentioning

confidence: 93%

Thermochemical oxidation of methane induced by high-valence metal oxides in a sedimentary basin

Kang

Cao

et al. 2018

Nat Commun

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Thermochemical oxidation of methane (TOM) by high-valence metal oxides in geological systems and its potential role as a methane sink remain poorly understood. Here we present evidence of TOM induced by high-valence metal oxides in the Junggar Basin, located in northwestern China. During diagenesis, methane from deeper source strata is abiotically oxidized by high-valence Mn(Fe) oxides at 90 to 135 °C, releasing 13C-depleted CO2, soluble Mn2+ and Fe2+. Mn generally plays the dominant role compared to Fe, due to its lower Gibbs free energy increment during oxidation. Both CO2 and metal ions are then incorporated into authigenic calcites, which are characterized by extremely negative δ13C values (−70 to −22.5‰) and high Mn content (average MnO = 5 wt.%). We estimate that as much as 1224 Tg of methane could be oxidized in the study area. TOM is unfavorable for gas accumulation but may act as a major methane sink in the deep crustal carbon cycle.

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“…In the specific context of reconstructing late Holocene RSL, this technique is effective at differentiating samples based on the relative proportions of marine and terrestrial organic material that they contain, which could enable recognition of sub-tidal, inter-tidal (e.g., mangroves), and freshwater environments in the stratigraphic record. Furthermore, Rock-Eval pyrolysis quantifies the maturity of organic carbon, which can provide insight into the burial history and diagenetic alteration of sediment (e.g., Roberts et al, 2018).…”

Section: Rock-eval Pyrolysismentioning

confidence: 99%

Testing the Utility of Geochemical Proxies to Reconstruct Holocene Coastal Environments and Relative Sea Level: A Case Study from Hungry Bay, Bermuda

Kemp¹,

Vane²,

Khan³

et al. 2019

Open Quaternary

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On low-lying, tropical and sub-tropical coastlines freshwater marshes may be replaced by salt-tolerant mangroves in response to relative sea-level rise. Pollen analysis of radiocarbon-dated sediment cores showed that such a change occurred in Hungry Bay, Bermuda during the late Holocene. This well-established paleoenvironmental trajectory provides an opportunity to explore if geochemical proxies (bulk-sediment δ 13 C and Rock-Eval pyrolysis) can reconstruct known environmental changes and relative sea level. We characterized surface sediment from depositional environments in Bermuda (freshwater wetlands, saline mangroves, and wrack composed of Sargassum natans macroalgae) using geochemical measurements and demonstrate that a multi-proxy approach can objectively distinguish among these environments. However, application of these techniques to the transgressive sediment succession beneath Hungry Bay suggests that freshwater peat and mangrove peat cannot be reliably distinguished in the sedimentary record, possibly because of post-depositional convergence of geochemical characteristics on decadal to multi-century timescales and/or the relatively small number of modern samples analyzed. Sediment that includes substantial contributions from Sargassum is readily identified by geochemistry, but has a limited spatial extent. Radiocarbon dating indicates that beginning at -700 CE, episodic marine incursions into Hungry Bay (e.g., during storms) carried Sargassum that accumulated as wrack and thickened through repeated depositional events until ~300 CE. It took a further ~550 years for a peat-forming mangrove community to colonize Hungry Bay, which then accumulated sediment rapidly, but likely out of equilibrium with regional relative sea-level rise.

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Disentangling Diagenesis From the Rock Record: An Example From the Permo‐Triassic Wordie Creek Formation, East Greenland

Cited by 6 publications

References 38 publications

Global warming leads to Early Triassic nutrient stress across northern Pangea

Global warming leads to Early Triassic nutrient stress across northern Pangea

Thermochemical oxidation of methane induced by high-valence metal oxides in a sedimentary basin

Testing the Utility of Geochemical Proxies to Reconstruct Holocene Coastal Environments and Relative Sea Level: A Case Study from Hungry Bay, Bermuda

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