The search for ‘hot shales’ in the western Kufra Basin, Libya: geochemical and mineralogical characterisation of outcrops, and insights into latest Ordovician climate

Meinhold, Guido; Heron, Daniel Paul Le; Elgadry, Mohamed; Abutarruma, Yousef

doi:10.1007/s12517-015-2173-0

Cited by 10 publications

(8 citation statements)

References 28 publications

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“…This theory has been suggested in several published studies [e.g., Armstrong et al, 2005Armstrong et al, , 2009Le Heron et al, 2013]. It is also supported by the changes in clay mineral composition documented in the Kufra basin (Libya) by Meinhold et al [2015], who interpreted an increase in kaolinite content as probably representative of enhanced continental weathering due to the climate change occurring from the Late Ordovician icehouse to the Silurian greenhouse. Similarly, Finlay et al [2010] demonstrated an increase in continental weathering concomitant with the deglaciation based on osmium isotope analysis.…”

Section: Impact Of An Increased Nutrient Supply To the Oceansupporting

confidence: 53%

The Climatic Significance of Late Ordovician–early Silurian Black Shales

Pohl

2019

Geological Society of America Abstracts With Programs

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The Ordovician-Silurian transition (∼455-430 Ma) is characterized by repeated climatic perturbations, concomitant with major changes in the global oceanic redox state best exemplified by the periodic deposition of black shales. The relationship between the climatic evolution and the oceanic redox cycles, however, remains largely debated. Here using an ocean-atmosphere general circulation model accounting for ocean biogeochemistry (MITgcm), we investigate the mechanisms responsible for the burial of organic carbon immediately before, during, and right after the latest Ordovician Hirnantian (445-444 Ma) glacial peak. Our results are compared with recent sedimentological and geochemical data. We show that the late Katian time slice (∼445 Ma), typified by the deposition of black shales at tropical latitudes, represents an unperturbed oceanic state, with regional organic carbon burial driven by the surface primary productivity. During the Hirnantian, our experiments predict a global oxygenation event, in agreement with the disappearance of the black shales in the sedimentary record. This suggests that deep-water burial of organic matter may not be a tenable triggering factor for the positive carbon excursion reported at that time. Our simulations indicate that the perturbation of the ocean circulation induced by the release of freshwater, in the context of the post-Hirnantian deglaciation, does not sustain over sufficiently long geological periods to cause the Rhuddanian (∼444 Ma) oceanic anoxic event. Input of nutrients to the ocean, through increased continental weathering and the leaching of newly exposed glaciogenic sediments, may instead constitute the dominant control on the spread of anoxia in the early Silurian.

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Section: Impact Of An Increased Nutrient Supply To the Oceansupporting

confidence: 53%

The Climatic Significance of Late Ordovician–early Silurian Black Shales

Pohl

2019

Geological Society of America Abstracts With Programs

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“…This theory has been suggested in several published studies [e.g., Armstrong et al , , ; Le Heron et al , ]. It is also supported by the changes in clay mineral composition documented in the Kufra basin (Libya) by Meinhold et al [], who interpreted an increase in kaolinite content as probably representative of enhanced continental weathering due to the climate change occurring from the Late Ordovician icehouse to the Silurian greenhouse. Similarly, Finlay et al [] demonstrated an increase in continental weathering concomitant with the deglaciation based on osmium isotope analysis.…”

Section: The Early Silurian Rhuddanian Oceanic Anoxic Eventmentioning

confidence: 59%

The climatic significance of Late Ordovician‐early Silurian black shales

et al. 2017

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The Ordovician‐Silurian transition (∼455–430 Ma) is characterized by repeated climatic perturbations, concomitant with major changes in the global oceanic redox state best exemplified by the periodic deposition of black shales. The relationship between the climatic evolution and the oceanic redox cycles, however, remains largely debated. Here using an ocean‐atmosphere general circulation model accounting for ocean biogeochemistry (MITgcm), we investigate the mechanisms responsible for the burial of organic carbon immediately before, during, and right after the latest Ordovician Hirnantian (445–444 Ma) glacial peak. Our results are compared with recent sedimentological and geochemical data. We show that the late Katian time slice (∼445 Ma), typified by the deposition of black shales at tropical latitudes, represents an unperturbed oceanic state, with regional organic carbon burial driven by the surface primary productivity. During the Hirnantian, our experiments predict a global oxygenation event, in agreement with the disappearance of the black shales in the sedimentary record. This suggests that deep‐water burial of organic matter may not be a tenable triggering factor for the positive carbon excursion reported at that time. Our simulations indicate that the perturbation of the ocean circulation induced by the release of freshwater, in the context of the post‐Hirnantian deglaciation, does not sustain over sufficiently long geological periods to cause the Rhuddanian (∼444 Ma) oceanic anoxic event. Input of nutrients to the ocean, through increased continental weathering and the leaching of newly exposed glaciogenic sediments, may instead constitute the dominant control on the spread of anoxia in the early Silurian.

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“…They are the most important source rock for Early Palaeozoic-sourced hydrocarbons across North Africa (e.g., Lüning et al, 2000). Consequently, both the Upper Ordovician glaciogenic sediments and the lower Silurian 'hot' shales have been the focus of geological investigations in Libya (e.g., Lüning et al, 2000Lüning and Fello, 2008;Loydell et al, 2013;Meinhold et al, 2016;El Diasty et al, 2017a, b, c;Stockey et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

“…Portable gamma-ray spectrometry (PGRS) is widely used to measure the U content of the Tanezzuft Formation shales at outcrop to search for 'warm' shales and 'hot' shales in southern Libya (e.g., Lüning and Fello, 2008;Meinhold et al, 2016).…”

Section: Introductionmentioning

confidence: 99%