Deep-water clastic systems in the Upper Carboniferous (Upper Mississippian–Lower Pennsylvanian) Shannon Basin, western Ireland

Martinsen, Ole J.; Pulham, Andrew J.; Elliott, T.; Haughton, Peter D. W.; Pierce, Colm; Lacchia, Anthea; Barker, Simon P.; Latre, Arnau Obradors; Kane, Ian A.; Shannon, Patrick M.; Sevastopulo, George D.

doi:10.1306/021417dig17099

Cited by 9 publications

(11 citation statements)

References 21 publications

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“…The Ross Formation is well‐exposed in high sea cliffs and foreshore exposures around the Loop Head peninsula (Fig. B; Collinson et al ., ; Chapin et al ., ; Elliot, ,b; Martinsen et al ., , ; Wignall & Best, ; Lien et al ., ; Pyles, ; Pierce et al ., ). Additional exposures occur at Ballybunion on the south side of the Shannon estuary in county Kerry (Fig.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…It was one of a series of interconnected, low‐latitude basins extending from Ireland into Britain and beyond, the geometry of which reflects reactivation of earlier Caledonian structures (Leeder, ; Collinson et al ., ; Pyles, ). Although a largely carbonate‐filled Mississippian depocentre, an influx of clastic sediment from the west produced a Serpukhovian to Bashkirian shallowing‐upward succession more than 2200 m thick in the axis of the basin (Martinsen et al ., , ). The basin was subsequently inverted and deformed during the Variscan Orogeny in the late Pennsylvanian (Fitzgerald et al ., ; Blackmore, ; Goodhue & Clayton, ; Nenna & Aydin, ).…”

Section: Geological Backgroundmentioning

confidence: 99%

“…(A) Regional geological map of the study area showing distribution of lithostratigraphic units filling the Clare Basin in western Ireland (modified after Martinsen et al ., ). (B) Summary geological map centred on the Loop Head peninsula showing the location of the behind‐outcrop research boreholes (after Pierce et al ., ).…”

Section: Introductionmentioning

confidence: 97%

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High‐resolution X‐ray fluorescence profiling of hybrid event beds: Implications for sediment gravity flow behaviour and deposit structure

et al. 2020

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Hybrid event beds form when turbidity currents that transport or locally acquire significant quantities of mud decelerate. The mud dampens turbulence driving flow transformations, allowing both mud and sand to settle into dense, near‐bed fluid layers and debris flows. Quantifying details of the mud distribution vertically in what are often complex tiered deposits is critical to reconstructing flow processes and explaining the diverse bed types left by mud‐bearing gravity flows. High‐resolution X‐ray fluorescence core scanning provides continuous vertical compositional profiles that can help to constrain mud distribution at sub‐millimetre scale, offering a significant improvement over discrete sampling. The approach is applied here to cores acquired from the Pennsylvanian Ross Sandstone Formation, western Ireland, where a range of hybrid event beds have been identified. Raw X‐ray fluorescence counts are calibrated against element concentrations and mineral abundances determined on coincident core plugs, with element and element log‐ratios used as proxies to track vertical changes in abundances of quartz, illite (including mica), chlorite and calcite cement. New insights include ‘stepped’ (to higher values) as opposed to ‘saw‐tooth’ vertical changes in mud content and the presence of compositional banding that would otherwise be overlooked. Hybrid event beds in basin floor sheets that arrived ahead of the prograding fan system have significantly cleaner sandy components than those in mid‐fan lobes. The latter may imply that the heads of the currents emerging from mid‐fan channels entrained significant mud immediately before they collapsed. Many of the H3 debrites are bipartite with a sandier H3a division attributed to re‐entrainment and mixing of a trailing debris or fluid mud flow (H3b) with sand left by the forward part of the flow. Hybrid event bed structure may thus partly reflect substrate interaction and mixing during deposition, and the texture of the bed divisions may not simply mirror those in the suspensions from which they formed.

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Section: Geological Backgroundmentioning

confidence: 99%

Section: Geological Backgroundmentioning

confidence: 99%

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High‐resolution X‐ray fluorescence profiling of hybrid event beds: Implications for sediment gravity flow behaviour and deposit structure

et al. 2020

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“…The Shannon Basin (sensu Sevastopulo, 2001; also known as the Clare Basin or Western Irish Namurian Basin; Croker, 1995;Wignall & Best, 2000) developed during the Carboniferous as a consequence of the reactivation of the Iapetus suture during the assembly of Pangaea (Phillips et al, 1976;Klemperer, 1989;McKerrow & Soper, 1989). The basin has an elongate WSW-ENE orientation stretching from the Atlantic Ocean to central Ireland (Collinson et al, 1991;Martinsen et al, 2003) and was filled by a thick succession of Serpukhovian to Bashkirian siliciclastic sediments that record the overall progradation of the depositional system from deep-marine turbidites to delta slope and fluvio-deltaic environments (Rider, 1974;Pulham, 1989;Wignall & Best, 2000Martinsen et al, 2003Martinsen et al, , 2017 Fig. 1).…”

Section: Geological Settingmentioning

confidence: 99%

“…The lower portion of the succession, the Shannon Group ( Fig. 1B; Clare Shale, Ross Sandstone and Gull Island formations), represents deep-marine and slope depositional environments (Hodson & Lewarne, 1961;Rider, 1974;Gill, 1979;Chapin et al, 1994;Wignall & Best, 2000Lien et al, 2003;Martinsen et al, 2003Martinsen et al, , 2017Pyles & Jennette, 2009;Pyles et al, 2011Pyles et al, , 2014Pierce et al, 2018). The Pennsylvanian (Namurian) Central Clare Group overlies these deposits ( Fig.…”

Section: Geological Settingmentioning

confidence: 99%

Early burial mud diapirism and its impact on stratigraphic architecture in the Carboniferous of the Shannon Basin, County Clare, Ireland

et al. 2018

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Delta fronts are often characterized by high rates of sediment supply that result in unstable slopes and a wide variety of soft‐sediment deformation, including the formation of overpressured and mobile muds that may flow plastically during early burial, potentially forming mud diapirs. The coastal cliffs of County Clare, western Ireland, expose Pennsylvanian (Namurian) delta‐front deposits of the Shannon Basin at large scale and in three dimensions. These deposits include decametre‐scale, internally chaotic mudstone masses that clearly impact the surrounding sedimentary strata. Evidence indicates that these were true mud (unlithified sediment) diapirs that pierced overlying strata. This study documents a well‐exposed ca 20 m tall mud diapir and its impact on the surrounding mouth‐bar deposits of the Tullig Cyclothem. A synsedimentary fault and associated rollover dome, evident from stratal thicknesses and the dip of the beds, define one edge of the diapir. These features are interpreted as recording the reactive rise of the mud diapir in response to extensional faulting along its margin. Above the diapir, heterolithic sandstones and siltstones contain evidence for the creation of localized accommodation, suggesting synsedimentary filling, tilting and erosion of a shallow sag basin accommodated by the progressive collapse of the diapir. Two other diapirs are investigated using three‐dimensional models built from ‘structure from motion’ drone imagery. Both diapirs are interpreted to have grown predominantly through passive rise (downbuilding). Stratal relationships for all three diapirs indicate that they were uncompacted and fluid‐rich mud beds that became mobilized through soft‐sediment deformation during early burial (i.e. <50 m, likely <10 m depth). Each diapir locally controlled the stratigraphic architecture in the shallow subsurface and potentially influenced local palaeocurrents on the delta. The mud diapirs studied herein are distinct from deeper ‘shale diapirs’ that have been inferred from seismic sections worldwide, now largely disputed.

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Heavy mineral variations in mid‐Carboniferous deltaic sandstones: Records of a pre‐depositional sediment history?

Nauton‐Fourteu

Tyrrell

Morton³

2020

The Depositional Record

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Sandstone composition is influenced by multiple factors, including acidic weathering, occurring during storage in the hinterland, prior to deposition. This study aims to better understand and constrain how the nature and duration of such pre‐depositional factors might impact the final sediment composition. Mid‐Carboniferous deltaic sandstones from the Clare Basin, western Ireland, for which depositional environments and provenance are well constrained, are the target of this study. Conventional heavy mineral analysis and specific heavy mineral ratios, such as the apatite–tourmaline index are utilised to examine these phenomena. Relatively high apatite–tourmaline index values observed in channelised sandstones contrast with lower values seen in sandstones associated with mouth bar and interdistributary bay facies. These variations are not linked to changes in provenance and thus potentially indicate differences in weathering intensity due to variable duration of alluvial storage. These changes are probably linked with shorter hinterland residence time in the channelised than in mouth bar and interdistributary bay sandstones. Variations are seen in the rutile‐zircon index without any clear link with facies. These fluctuations could be ascribed to variable supply from a source, which is relatively rich in rutile but poor in zircon and apatite. Despite the apatite component in these sandstones being partially derived from recycled sources, the apatite–tourmaline index stills appears to hold information on the last sedimentary cycle.

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Deep-water clastic systems in the Upper Carboniferous (Upper Mississippian–Lower Pennsylvanian) Shannon Basin, western Ireland

Cited by 9 publications

References 21 publications

High‐resolution X‐ray fluorescence profiling of hybrid event beds: Implications for sediment gravity flow behaviour and deposit structure

High‐resolution X‐ray fluorescence profiling of hybrid event beds: Implications for sediment gravity flow behaviour and deposit structure

Early burial mud diapirism and its impact on stratigraphic architecture in the Carboniferous of the Shannon Basin, County Clare, Ireland

Heavy mineral variations in mid‐Carboniferous deltaic sandstones: Records of a pre‐depositional sediment history?

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