The significance of Tournaisian tectonism in the Dublin basin: Implications for basin evolution and zinc-lead mineralization in the Irish Midlands

Morton, Simone N. de; Wallace, Malcolm W.; Reed, Christopher P.; Hewson, Chad; Redmond, Patrick; Cross, Eoin; Moynihan, Conor

doi:10.1016/j.sedgeo.2015.09.017

Cited by 10 publications

(8 citation statements)

References 25 publications

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“…According to the widespread geological models, the Calp limestone is formed by two lithofacies groups: The Upper and Lower Calp groups. This stratigraphic Upper/Lower Calp boundary was previously detected by several active seismic profiles carried out in the Irish Midlands (de Morton et al., 2015). It appears as pronounced reflectors laterally varying in depth from 100–500 m within the Calp limestone (de Morton et al., 2015).…”

Section: Resultssupporting

confidence: 73%

“…This stratigraphic Upper/Lower Calp boundary was previously detected by several active seismic profiles carried out in the Irish Midlands (de Morton et al., 2015). It appears as pronounced reflectors laterally varying in depth from 100–500 m within the Calp limestone (de Morton et al., 2015). Furthermore, the NGE1 sonic log (Figure 1b) located at the Dublin Basin margins clearly shows a significant sonic P velocity increment associated with the upper/lower boundary at ∼600 m. In contrast, the NGE2 lithostratigraphic borehole (located 1 km north‐west from the NGE1 sonic log) identifies the Lower/Upper Calp boundary at ∼880 m. The analysis of the available information and results leads us to propose two interpretative scenarios.…”

Section: Resultssupporting

confidence: 73%

“…A regional depositional unconformity marks the boundary with the underlying Lower Paleozoic (Silurian) Dublin basement. The Lower Paleozoic rocks consist of various Silurian phyllitic siltstones and shales underlying low metamorphic Cambro‐Ordovician quartzites (de Morton et al., 2015). The Lower Palaeozoic basement was intruded during the Caledonian orogenesis by granite plutons.…”

Section: Geological Backgroundmentioning

confidence: 99%

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Subsurface characterization using passive seismic in the urban area of Dublin City, Ireland

Maggio

Subašić

Bean

2022

Geophysical Prospecting

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We investigate the shallow geological features and previously unknown depths of the main geological interfaces in the highly urbanized Dublin City area by using a set of complementary ambient noise seismic methods. A sparse seismic array, composed of 19 broadband sensors, was installed in a 5 × 5 km area across the city centre. The dataset was acquired over a 5‐month‐long deployment and used to perform horizontal/vertical spectral ratios and frequency–wave number analysis cross‐correlation interferometry. From the horizontal/vertical high‐frequency resonance peaks, we estimate the depth to bedrock. Then we use a subset of six seismic stations to obtain the frequency–wavenumber Rayleigh wave fundamental mode in the 0.8–3 Hz frequency band. Next, the ambient noise dataset is cross‐correlated in order to extract the empirical Green's functions before measuring surface‐wave phase velocities by undertaking a dispersion analysis in the 0.5–9 Hz frequency band. Then, a Monte Carlo global optimization algorithm is used to invert the phase velocity dispersion measurements. We generate a reference one‐dimensional depth S velocity profile along with a set of localized one‐dimensional S velocity profiles. Finally, a smooth three‐dimensional shear wave velocity model is derived for the top 1000 m in the sedimentary Dublin Basin. From the one‐dimensional velocity profiles and three‐dimensional shear velocity model, with some sensitivity down to approximately 1.2 km, we observe velocity changes with depth that highlight the presence of three consistent interfaces. We discuss interpretative scenarios that correlate the velocity features to potential stratigraphic boundaries occurring within the sedimentary Dublin Basin, suggesting that basement rocks could be located at a depth significantly greater than the top kilometre. The results of this study may indicate that future geothermal studies should be directed at structures deeper than 1 km, towards the bottom of the sedimentary basin beneath the city.

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Section: Resultssupporting

confidence: 73%

Section: Resultssupporting

confidence: 73%

Section: Geological Backgroundmentioning

confidence: 99%

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Subsurface characterization using passive seismic in the urban area of Dublin City, Ireland

Maggio

Subašić

Bean

2022

Geophysical Prospecting

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“…Following collision, terrestrial sediments were deposited during the Devonian (e.g., Graham 2009), before a shift to predominantly carbonate deposition as a result of a regional marine transgression during earliest Carboniferous (Tournaisian) times (MacDermot and Sevastopulo 1972). During the Tournaisian and Viséan, several intracratonic basins developed across Ireland as a result of tectonism and subsidence (e.g., Strogen et al 1996;Somerville 2008;de Morton et al 2015), principally controlled by movement on NE-SW oriented structures, whose orientation was inherited from underlying Caledonian features (Worthington and Walsh 2011; see also Walsh et al 2019). Extensive carbonate production continued in Ireland for much of the Mississippian, before a switch to terrigenous mud and sand deposition in the Serpukhovian and Bashkirian (formerly regionally termed the Namurian in northwest Europe: see Sevastopulo and Wyse Jackson 2009;Barham et al 2015 Fallon and.…”

Section: St Gorman's Well In Contextmentioning

confidence: 99%

Characterising thermal water circulation in fractured bedrock using a multidisciplinary approach: a case study of St. Gorman’s Well, Ireland

Blake

Henry

Moore³

et al. 2021

Hydrogeol J

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A hydrogeological conceptual model of the source, circulation pathways and temporal variation of a low-enthalpy thermal spring in a fractured limestone setting is derived from a multidisciplinary approach. St. Gorman’s Well is a thermal spring in east-central Ireland with a complex and variable temperature profile (maximum of 21.8 °C). Geophysical data from a three-dimensional(3D)audio-magnetotelluric(AMT) survey are combined with time-lapse hydrogeological data and information from a previously published hydrochemical analysis to investigate the operation of this intriguing hydrothermal system. Hydrochemical analysis and time-lapse measurements suggest that the thermal waters flow within the fractured limestones of the Carboniferous Dublin Basin at all times but display variability in discharge and temperature. The 3D electrical resistivity model of the subsurface revealed two prominent structures: (1) a NW-aligned faulted contact between two limestone lithologies; and (2) a dissolutionally enhanced, N-aligned, fault of probable Cenozoic age. The intersection of these two structures, which has allowed for karstification of the limestone bedrock, has created conduits facilitating the operation of relatively deep hydrothermal circulation (likely estimated depths between 240 and 1,000 m) within the limestone succession of the Dublin Basin. The results of this study support a hypothesis that the maximum temperature and simultaneous increased discharge observed at St. Gorman’s Well each winter is the result of rapid infiltration, heating and recirculation of meteoric waters within a structurally controlled hydrothermal circulation system.

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“…Following the collision, terrestrial sediments were deposited during the Devonian (e.g., Graham, 2009), with the onset of predominantly carbonate deposition as a result of a regional marine transgression during earliest Carboniferous (Tournaisian; McDermot & Sevastopulo, 1972). Several local depocenters, including the Clare Basin, developed across Ireland during the Tournaisian and Viséan (358.9-330.9 Ma) as a result of extensional tectonism and subsidence (e.g., de Morton et al, 2015;Somerville, 2008;Strogen et al, 1996). These basins were principally controlled by movement on NE-SW oriented structures, the orientation of which was inherited from underlying Caledonian trending features (Worthington & Walsh, 2011).…”

Section: Tectonic Contextmentioning

confidence: 99%

Subsurface Characterization of the Pennsylvanian Clare Basin, Western Ireland, by Means of Joint Interpretation of Electromagnetic Geophysical Data and Well‐Log Data

et al. 2019

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The integration of passive electromagnetic geophysical data and well-log data for basin characterization and interpretation has been investigated in the Clare Basin, western Ireland. The Clare Basin is overmature and has a clear contrast in electrical resistivity between the Clare Shale Formation, a widespread organic rich shale unit, and the surrounding stratigraphy. The electrical resistivity distribution beneath the Clare Basin was determined by means of three-dimensional (3-D) joint inversion of three distinct and differently sensitive electromagnetic parameters: (1) the MT impedance tensor (Z), (2) the geomagnetic transfer function (T), and (3) the interstation horizontal magnetic transfer function (H). Well-log data from a local exploration well, Doonbeg-1, were analyzed by means of multivariate statistical methods identifying three groups with distinct resistivity values. The groups were propagated along the basin using the 3-D electrical resistivity model, showing those regions in the basin with significant organic content at high maturity stage. The lack of continuity of these regions supports the hypothesis of advective fluid heating as the cause of the high maturity levels. The results also help to define the geometry of the basin at depth and have identified an area within the basin, near the Loop Head, where organic-rich clay/shale is either poorly developed, and/or the organic matter is less mature and less conductive. Finally, the potential of the basin for both CO 2 storage and geothermal energy was considered, supporting the use of the Clare Basin as a potential site for geothermal energy but not for the storage of CO 2 .

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The significance of Tournaisian tectonism in the Dublin basin: Implications for basin evolution and zinc-lead mineralization in the Irish Midlands

Cited by 10 publications

References 25 publications

Subsurface characterization using passive seismic in the urban area of Dublin City, Ireland

Subsurface characterization using passive seismic in the urban area of Dublin City, Ireland

Characterising thermal water circulation in fractured bedrock using a multidisciplinary approach: a case study of St. Gorman’s Well, Ireland

Subsurface Characterization of the Pennsylvanian Clare Basin, Western Ireland, by Means of Joint Interpretation of Electromagnetic Geophysical Data and Well‐Log Data

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