Occurrence of Hyperpycnal Flows and Hybrid Event Beds Related To Glacial Outburst Events In A Late Ordovician Proglacial Delta (Murzuq Basin, SW Libya)

Girard, Flavia; Ghienne, Jean‐François; Rubino, Jean‐Loup

doi:10.2110/jsr.2012.61

Cited by 56 publications

(86 citation statements)

References 97 publications

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“…The stratigraphic position and range of facies are comparable with those of Wadi Aramat in western Libya, where outburst deposits record the final demise of Hirnantian ice sheets (Girard et al 2012). In a 200 m thick succession at Jabal Eghei, both humpback dunes with a sigmoidal geometry (Lang & Winsemann 2013) and antidunes are recognized (Fig.…”

Section: Uppermost Mamuniyat Formationsupporting

confidence: 60%

“…Ghienne et al 2010;Girard et al 2012). retreating ice sheets shed sediment toward the north during catastrophic collapse Girard et al 2012;Hirst 2012), and we interpret the climbing dune crossstratification facies association in the Jabal Eghei part of the uppermost Mamuniyat Formation as representing jökulhlaup outbursts following the main phase of the Hirnantian glaciation.…”

Section: Uppermost Mamuniyat Formationmentioning

confidence: 78%

“…Earlier claims of hummocky cross-stratification (Le Heron et al 2006) have failed to be substantiated, because the structures present are climbing-dune cross-stratification deposited by a different process (e.g. Girard et al 2012).…”

Section: Study Area and Stratigraphymentioning

confidence: 97%

“…The Mamuniyat Formation similarly is ill constrained in Jabal Eghei, whereas the Tanezzuft Formation contains graptolites of Hirnantian-rhuddanian affinity (Page et al 2013). the topmost part of the Mamuniyat Formation (Girard et al 2012), recording the final collapse of Hirnantian ice sheets (Fig. 2).…”

Section: Uppermost Mamuniyat Formationmentioning

confidence: 99%

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Did lingering ice sheets moderate anoxia in the Early Palaeozoic of Libya?

Heron

Meinhold

Page

et al. 2013

JGS

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Abstract:The Hirnantian glaciation of West Gondwana produced a glacially sculpted topography, which is draped by organic-rich latest Ordovician and early Silurian 'hot shales'. Although these are the most important Early Palaeozoic source rock in North Africa, organic enrichment is distributed unevenly. For example, in Al Kufrah Basin, Libya, 'hot shales' are elusive, but outcrop analysis at the western basin demonstrates why this is the case. The topmost Mamuniyat Formation, of Hirnantian age, comprises glaciogenic sandstones, passing upward into mixed facies of the Tanezzuft Formation, which has a latest Ordovician-early Silurian age. The basal Tanezzuft Formation contains a shelly carbonate (cool-water deposits accumulated under oxygenating conditions) and bioturbated sandstone succession. Above, hummocky cross-bedded and graded sandstone intervals are intercalated with shale and siltstone (storm influx onto a muddy shelf). These are interrupted by several lonestone-bearing intervals (ice-rafted debris), a striated pavement (of subglacial origin), and manganese oxide crusts and concretions. The concretions and bioturbation imply oxygenation of the sea floor during transgression. These putative glacial deposits were deposited following the main phase of the Hirnantian glaciation, at the same stratigraphic level as 'hot shales' elsewhere in northern Gondwana. Lingering ice caps may have produced well-oxygenated marine waters precluding 'hot shale' deposition.

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Section: Uppermost Mamuniyat Formationsupporting

confidence: 60%

Section: Uppermost Mamuniyat Formationmentioning

confidence: 78%

Section: Study Area and Stratigraphymentioning

confidence: 97%

Section: Uppermost Mamuniyat Formationmentioning

confidence: 99%

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Did lingering ice sheets moderate anoxia in the Early Palaeozoic of Libya?

Heron

Meinhold

Page

et al. 2013

JGS

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“…GLOFs have been studied on all continents, including Africa (e.g. Girard et al, 2012), Australia (e.g. Goodsell et al, 2005) and Antarctica (e.g.…”

Section: Citations and Referencesmentioning

confidence: 99%

GLOFs in the WOS: bibliometrics, geographies and global trends of research on glacial lake outburst floods (Web of Science, 1979–2016)

Emmer

2018

Nat. Hazards Earth Syst. Sci.

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Abstract. Research on glacial lake outburst floods (GLOFs) -specific low-frequency, high-magnitude floods originating in glacial lakes, including jökulhlaups -is well justified in the context of glacier ice loss and glacial lake evolution in glacierized areas all over the world. Increasing GLOF research activities, which are documented by the increasing number of published research items, have been observed in the past few decades; however, comprehensive insight into the GLOF research community, its global bibliometrics, geographies and trends in research is missing. To fill this gap, a set of 892 GLOF research items published in the Web of Science database covering the period 1979-2016 was analysed. General bibliometric characteristics, citations and references were analysed, revealing a certain change in the publishing paradigm over time. Furthermore, the global geographies of research on GLOFs were studied, focusing on (i) where GLOFs are studied, (ii) who studies GLOFs, (iii) the export of research on GLOFs and (iv) international collaboration. The observed trends and links to the challenges ahead are discussed and placed in a broader context.

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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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Occurrence of Hyperpycnal Flows and Hybrid Event Beds Related To Glacial Outburst Events In A Late Ordovician Proglacial Delta (Murzuq Basin, SW Libya)

Cited by 56 publications

References 97 publications

Did lingering ice sheets moderate anoxia in the Early Palaeozoic of Libya?

Did lingering ice sheets moderate anoxia in the Early Palaeozoic of Libya?

GLOFs in the WOS: bibliometrics, geographies and global trends of research on glacial lake outburst floods (Web of Science, 1979–2016)

The climatic significance of Late Ordovician‐early Silurian black shales

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