Black shale deposition in an Upper Ordovician–Silurian permanently stratified, peri-glacial basin, southern Jordan

Organic geochemical characteristics of black shales across the Ordovician–Silurian boundary in the Holy Cross Mountains, central Poland

“…9 A&B) in the HCM are consistent with those for the wider Ordovician-Silurian paleoenvironments. For instance, a drastic change in the Mustafa, K.A., Sephton M.A., Spathopoulos, F., Watson, J.S., Krzywiec, P Mountains, Central Poland, Marine andPetroleum Geology, doi:10.1016/j.marpetgeo.2015.08.018. 15 depositional environment, bottom water condition, fossil fauna, and organic matter production and preservation was observed during the transition from the Late Ordovician to the Early Silurian, not only in Poland (Kremer, 2001;Masiak et al, 2003;Podhalanska, 2003;Sawlowicz and Porebska, 1998;Trela et al, 2001), but also in other parts of the world (Armstrong et al, 2009;Lüning et al, 2006;Melchin et al, 2013;Vecoli, 2008).…”

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

“…It seems that ice sheets remained into at least the late Hirnantian in the Al Kufrah Basin. rather than experiencing a sudden large-scale outwash following the Hirnantian glacial maximum that led to 'hot shale' deposition in Jordan (Armstrong et al 2005(Armstrong et al , 2009), these lingering ice sheets at Jabal Eghei may have decayed more gradually. This locality did not receive the rapid injection of meltwater and terrestrially derived nutrients that drove post-glacial 'hot shale' deposition elsewhere in Gondwana, so although the Tanezzuft Formation did experience a brief interval of post-glacially transgressive anoxia at Jabal Eghei, the melt of the localized ice sheets may have been insufficient to sustain long-lived anoxia or 'hot shale' deposition.…”

“…The ice sheets grew to their maximum extent in the Hirnantian, which left a distinct yet only partially understood stable isotopic excursion in low-latitude carbonates known as the Hirnantian Isotopic Curve Excursion, or HICE (Delabroye & Vecoli 2010). Although it is possible that deposits of the Hirnantian glacial maximum in North Gondwana correlate with the HICE, the only stable isotope data in North Gondwana derive from post-glacial shale in Tunisia (Vecoli et al 2009) and Jordan (Armstrong et al 2009). …”

“…Unfortunately, this model inadequately explains the sheet-like occurrence of organic-rich shales over wide areas of western Algeria, and a tectonic component for their uneven distribution has also been suggested around the oilfields of the northern Murzuq Basin . Elsewhere, in Jordan, variation in TOC is linked to changes in the rate of nutrients supplied to the upper ocean by deglacial outwash (Armstrong et al 2005(Armstrong et al , 2009). To better understand the controls on anoxia and the genesis of the 'hot shales', we address the temporal, lateral and bathymetric distribution of organic-rich shales and oxygen-poor depositional conditions from a superbly exposed succession in Libya.…”

Geomicrobial functional groups: A window on the interaction between life and environments

“…In the Phanerozoic, euxinic oceans also occurred frequently, and interrupted the normal oxic oceanic sedimentation. The main intervals known with euxinic conditions in the Phanerozoic are Late Cambrian [171], the transition from Ordovician to Silurian [172], Late Devonian [173], late Permian to early Triassic [55,174] and several intervals in the Cretaceous known as the Anoxic Ocean Events [175]. It remains unclear whether these euxinic oceans were global, or caused by local restricted sedimentary basin conditions (e.g.…”