Ancient glaciations and hydrocarbon accumulations in North Africa and the Middle East

Heron, Daniel Paul Le; Craig, Jonathan; Etienne, James L.

doi:10.1016/j.earscirev.2009.02.001

Cited by 143 publications

(65 citation statements)

References 98 publications

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“…The causes of widespread deposition of black shales in the aftermath of the Hirnantian glaciation are under debate also (Lüning et al, 2005;Armstrong et al, 2006;Le Heron et al, 2009;Loydell et al, 2009). One theory contends that glaciation enhanced physical weathering on the continents, generating rock flour with a high surface-to-volume ratio (Saltzman, 2005).…”

Section: Introductionmentioning

confidence: 99%

Global and regional controls on marine redox changes across the Ordovician-Silurian boundary in South China

Liu

Algeo

et al. 2016

Palaeogeography, Palaeoclimatology, Palaeoecology

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The Ordovician-Silurian (O-S) transition coincided with significant environmental and biological changes. In South China, the Yangtze Platform experienced both global and regional events at this time, including sea-level fluctuations, tectonic movements, volcanic eruptions, mass extinction, and widespread anoxia. The O-S transitional strata of the Yangtze Platform comprise organic-rich black shales that are an important oil source rock. To explore the evolution of watermass chemistry and its relationship to organic matter accumulation, we conducted an integrated Fe-S-C geochemical study (i.e., Fe-speciation, δ 13 C org , δ 34 S py , pyrite-S and TOC) of the O-S boundary sections at Datianba (Chongqing Municipality) and Shuanghe (Sichuan Province). These sections were located in the restricted inner Yangtze Sea, in contrast to the previously studied Wangjiawan section, which was deposited in a more open setting of the outer Yangtze Sea. In contrast to the well-oxygenated conditions at Wangjiawan, the Datianba and Shuanghe sections record persistently anoxic, and episodically euxinic, conditions during the Hirnantian, which can be explained by the unique paleogeography and restricted hydrography of the inner Yangtze Sea. We propose that the regional Kwangsian Orogeny, which was driven by collision of the Yangtze and Cathaysia blocks, played a key role in basin development, watermass chemistry changes, and accumulation of Wufeng Formation black shales within the Yangtze Sea. The more widespread black shales of the Lower Silurian Lungmachi Formation were linked to the post-Hirnantian global marine transgression.

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Section: Introductionmentioning

confidence: 99%

Global and regional controls on marine redox changes across the Ordovician-Silurian boundary in South China

Liu

Algeo

et al. 2016

Palaeogeography, Palaeoclimatology, Palaeoecology

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“…Well-preserved exposed subglacial channels are rare. During glacial recession, meltwater released from the ice sheet accumulates at the ice marginal area and erodes the channel, with post-glacial sediment accumulation causing burial or partial burial (Le Heron et al, 2009). Vegetation overprint and fluvial incision makes the detailed study of channel geometry and morphology difficult (e.g., Walder and Hallet, 1979).…”

mentioning

confidence: 99%

Subglacial drainage patterns of Devon Island, Canada: detailed comparison of rivers and subglacial meltwater channels

Galofre

Jellinek

Osinski³

et al. 2018

The Cryosphere

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Abstract. Subglacial meltwater channels (N-channels) are attributed to erosion by meltwater in subglacial conduits. They exert a major control on meltwater accumulation at the base of ice sheets, serving as drainage pathways and modifying ice flow rates. The study of exposed relict subglacial channels offers a unique opportunity to characterize the geomorphologic fingerprint of subglacial erosion as well as study the structure and characteristics of ice sheet drainage systems. In this study we present detailed field and remote sensing observations of exposed subglacial meltwater channels in excellent preservation state on Devon Island (Canadian Arctic Archipelago). We characterize channel cross section, longitudinal profiles, and network morphologies and establish the spatial extent and distinctive characteristics of subglacial drainage systems. We use field-based GPS measurements of subglacial channel longitudinal profiles, along with stereo imagery-derived digital surface models (DSMs), and novel kinematic portable lidar data to establish a detailed characterization of subglacial channels in our field study area, including their distinction from rivers and other meltwater drainage systems. Subglacial channels typically cluster in groups of ∼10 channels and are oriented perpendicular to active or former ice margins. Although their overall direction generally follows topographic gradients, channels can be oblique to topographic gradients and have undulating longitudinal profiles. We also observe that the width of firstorder tributaries is 1 to 2 orders of magnitude larger than in Devon Island river systems and approximately constant. Furthermore, our findings are consistent with theoretical expectations drawn from analyses of flow driven by gradients in effective water pressure related to variations in ice thickness. Our field and remote sensing observations represent the first high-resolution study of the subglacial geomorphology of the high Arctic, and provide quantitative and qualitative descriptions of subglacial channels that revisit well-established field identification guidelines. Distinguishing subglacial channels in topographic data is critical for understanding the emergence, geometry, and extent of channelized meltwater systems and their role in ice sheet drainage. The final aim of this study is to facilitate the identification of subglacial channel networks throughout the globe by using remote sensing techniques, which will improve the detection of these systems and help to build understanding of the underlying mechanics of subglacial channelized drainage.

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“…Some other factor may have therefore increased TOC during the 'hot shale' window. Although argued that upwelling may have contributed to this, the palaeogeography, with a shallow northward dipping shelf during the preceding Ordovician period (Le Heron et al 2009), makes this process unlikely at a large scale. Instead, the strongest correlation of TOC enrichment in this interval seems to be the post-Hirnantian glacial maximum transgression (Armstrong et al 2005;Page et al 2007), which coincides with deposition of the lower 'hot shale' in the latest Hirnantian and rhuddanian.…”

Section: The Anatomy Of Toc Enrichment In the 'Hot Shale' Windowmentioning

confidence: 99%

“…Elsewhere in Libya, the underlying Mamuniyat Formation yields a Hirnantia fauna and glacial deposits (Le Heron et al 2009, and references therein). Its disconformable contact with the Tanezzuft Formation is considered to result from post-glacial transgression and/or isostatic rebound following the Hirnantian glacial maximum (see Le Heron et al 2006;Moreau 2011).…”

Section: Prolonged Glaciation and Delayed Anoxia In The Tanezzuft Formentioning

confidence: 99%

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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Ancient glaciations and hydrocarbon accumulations in North Africa and the Middle East

Cited by 143 publications

References 98 publications

Global and regional controls on marine redox changes across the Ordovician-Silurian boundary in South China

Global and regional controls on marine redox changes across the Ordovician-Silurian boundary in South China

Subglacial drainage patterns of Devon Island, Canada: detailed comparison of rivers and subglacial meltwater channels

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

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