Regional variations of Tournaisian and Viséan lithostratigraphy and their links to basin and structural evolution in Ireland
PhD Candidate: Robert Doyle
Supervisor: Dr Koen Torremans, Prof John Walsh
Abstract:
This work details the lithological and unit thickness variability across a large portion of the Tournaisian and Viséan of Ireland, using 476 stratigraphically representative boreholes. A particular focus was put on how lithological changes link with their depositional environment and with the evolving rift structural framework. The deposition of carbonates during the Tournaisian in Ireland is characterised by a south to north diachroneity, reflecting a
northward transgression, initially on a generally south-dipping overall ramp geometry. The transgression was accompanied by a northward stepping of facies belts in several sub-Waulsortian units across the study area. Compiled micropalaeontological information suggests that early extensional faulting initiated in the early Ivorian, represented by clear syn-sedimentary thickening of the Moathill Fm across faults in the Central Midlands province. Conversely, such relationships are not shown for the underlying units such as the Meath Fm. The character of the Waulsortian Limestone Fm changes dramatically in terms of facies and thickness across the study area. In south-eastern areas, the Waulsortian forms laterally continuous “sheet-reef” growth forms which substantially thicken towards the central Iapetus suture zone. However, towards the north its development becomes less consistent
and is evidently more often localized to the immediate proximity of faults and in most northerly areas, the Waulsortian is commonly absent. Some of the reasons for this dramatic change in character are discussed.
The Waulsortian Limestone Fm records the transition from a general ramp geometry to an increasingly fault-controlled basin architecture. The Lower Viséan to Arundian is marked by a major change in facies deposition. Continued syn-rift extension localized on fewer but faster moving faults, temporally associated with a complex facies mosaic comprising areas of interfingering coeval deep basinal and shallower water shelf deposition. This was interpreted to coincide with eustatic sea level changes which strongly influenced the sedimentary environment. Using newly compiled biostratigraphical data, and lithological correlations, regional shallowing and (sudden) deepening trends can be recognized which correlate with well documented examples in laterally equivalent basins in Belgium, Wales and Germany.
Publications:
Doyle R., Kyne R., Torremans K., Güven, J., Walsh, J. (2017). The effect of inversion structures on the Irish Orefield from regional to mine scale. Irish Geological
Doyle, R., Philcox, M., Murray, J., McGrath, E., Torremans, K., Güven, J., Pracht, M., Walsh, J.J. (2019). The ‘Blue Book’ Revamped: Towards a Tectonostratigraphic Framework of the Tournaisian and Viséan of Ireland. Geoscience 2019 – Geoscience for Climate Action, 5 November, Dublin, Ireland
Kyne, R., Torremans, K., Doyle, R., Güven, J., Walsh, J.J. (2019). 3D modelling of the Lisheen and Silvermines deposits, Co. Tipperary, Ireland: Insights into structural viii controls on the formation of Irish Zn-Pb deposits. Economic Geology 114(1), 93-116. doi.org/10.5382/econgeo.2019.4621
Torremans, K., Kyne, R., Doyle, R., Güven, J., Walsh, J.J. (2018c). Controls on metal distributions at the Lisheen and Silvermines deposits: Insights into fluid flow pathways in Irish-type Zn-Pb deposits. Economic Geology, 113(7), 1455-1477. doi.org/10.5382/econgeo.2018.4598
Conneally, J., Torremans, K., Güven, J., Walsh, J.J., Doyle, R., Kyne, R., Guo, J. (2019a). 3D structure of the Irish Lower Carboniferous from deposit to regional scale modelling. Irish Association for Economic Geology Annual Conference: Mining our future, 11-12 May, Kilkenny, Ireland.
Torremans, K., Conneally, C., Güven, J., Doyle, R., Kyne, R., Guo, J., Dunlevy, E., Walsh, J.J. (2020a). Fault interactions, fault kinematics, and evolution of the structural framework in the Irish Lower Carboniferous. EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-4557, https://doi.org/10.5194/egusphereegu2020-4557
Torremans, K., Güven, J., Doyle, R., Conneally, J., Vafeas, N., Dunlevy, E., Walsh, J.J. (2020b). Insights into the basin evolution and structural framework of the Carboniferous of South-Central and SE Ireland. Irish Geological Research Meeting 2020, 28 February – 1 March, Athlone, Ireland.
Torremans, K., Güven, J., Conneally, J., Doyle, R., Guo, J., Kyne, R., Hollis, S.P., Hitzman, M.W., Walsh, J.J. (2018a). Insights into structural and tectonostratigraphic controls on base metal mineralization in the Irish Lower Carboniferous. Gordon Research Conference on Geochemistry of Mineral Deposits, 6-10 August 2018, Waterville Valley, New Hampshire.
Torremans, K., Güven, J., Conneally, J., Kyne, R., Doyle, R., Hollis, S., Hitzman, M.W., Walsh, J.J. (2018b). An integrated tectono-stratigraphic basin evolution approach to understanding the Irish Orefield. SEG2018: Metal, Minerals and Society, 22-25 September, Keystone, Colorado, USA.
Güven, J., Torremans, K., Kyne, R., Conneally, J., Doyle, R., Hitzman, M.W., Walsh, J.J. (2018). Segmented fault arrays and their control on Irish Zn-Pb deposits. SEG2018: Metal, Minerals and Society, 22-25 September, Keystone, Colorado,
USA.
References:
A full list of references can be found at the (opens in a new window)UCD Research Repository.