Research Output
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Publication
Facies and internal stratigraphic variability in the Ross Sandstone Formation (Pennsylvanian), western Ireland - new borehole data from south of the Shannon Estuary
2013-09, Obradors-Latre, Arnau, Pierce, Colm, Haughton, Peter D. W., Shannon, Patrick M.
The 500 m thick Ross Sandstone Formation is well
exposed in sea cliffs facing the Atlantic and along the Shannon Estuary in
western Ireland. It forms the sandy deep-water part of a major
shallowing-upward Pennsylvanian succession. Over the last four years, a major
behind-outcrop drilling program targeting the Ross Sandstone Formation has been
undertaken, focussing primarily on the Loop Head peninsula in west Clare. This
has provided a full composite Ross cored section that underpins a new understanding
of bed-scale variability and the wider evolution of the system. The focus has
recently shifted to the key Ballybunion section on the south side of the River Shannon,
obliquely down-dip from the Loop Head area (c. 18 km from the tip of the Loop)
and is important in that previous outcrop studies have inferred that (1) the
distinctive character of the lower Ross here with its abundant hybrid event
beds may reflect a marginal position; and (2) extra sandy section may be present
in the uppermost Ross due to offset stacking of the youngest sandy lobes. Two
new cores are now available ¿behind¿ the Ballybunion section - a 200 m PQ
borehole straddling the lower Ross and the upper part of the underlying Clare Shale
Formation (12-CE-UCD-09), and a 151.5 m long, cored slimhole with associated
wireline log data acquired by the Geological Survey of Ireland (GSI 09/05). The
latter is 1.1 km along strike from coastal exposures of the upper Ross and the
study reported here focusses on the relationship of the section acquired in
this borehole to the local cliffs and to upper Ross outcrops on the north side
of the River Shannon at Kilcredaun, some 4.6 km away. Correlation is based on
goniatite-rich ¿marine bands¿, legacy biostratigraphic data (new determinations
are underway), and a number of laterally extensive slump bodies which form
distinctive marker beds.
The GSI 09/05 core contains three thin goniatite-rich
levels, and a fourth candidate level, each interpreted as marine bands. These
separate sand-prone packages, interpreted as stacked isolated to amalgamated
lobe units, and at least two mass-transport units (MTDs), the lower and
thickest of which is 25.5 m thick (true thickness). In the local cliffs to the
west, all four marine bands can be identified, as well as the two MTDs. In
addition, a third MTD is more obvious in the cliff. The lobe sandstones are
dominated by deposits of high-density turbidity currents; amalgamated
sandbodies become more abundant upwards. Hybrid event beds are rare (<10%)
compared to lower in the formation. At least 50% of the sandbodies extend from
the core to the adjacent outcrop without change; the remainder show a change
from deposition from high- to low-concentration flows or vice versa. Overall,
the Ballybunion Ross section is 480 m thick, broadly similar to the thickness established
by drilling on the Loop. At longer length scales, all but the upper marine band
are found at Kilcredaun. Correlatives of the two MTD units also occur in the
core here, although the thickest slump has become thinner and muddier.
Nonetheless this MTD unit can be traced widely across the Loop as a distinctive
couplet. As correlated, the Ballybunion outcrop and core suggest there may not
be an additional younger sandbody in this area, however the location appears
axial and down-dip rather than marginal in character overall.
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Sedimentology of the upper Ross Formation (Pennsylvanian) in borehole GSI 09/05 at Ballybunion, Co. Kerry
2013-03, Obradors-Latre, Arnau, Haughton, Peter D. W., Shannon, Patrick M.
The Pennsylvanian Ross Sandstone Formation is well
exposed around the Shannon Estuary, in western Ireland. It forms the deep-water
part of a major shallowing-upward succession filling the Clare Basin and it has
been extensively used as a turbidite reservoir analogue and for subsurface
training.
Since 2009, a major program of behind-outcrop drilling
targeting the Ross Sandstone Formation has been undertaken in west Co. Clare (Loop
Head) and across the Shannon estuary in Co. Kerry. To date, most of the focus has been on boreholes acquired on Loop Head. These
have provided a composite vertical section through the Ross Sandstone Formation
and a framework for interpreting bed type variations and overall system
evolution. Now, the emphasis is changing to examine lateral variability away
from Loop Head using a new core at Ballybunion in the lowermost Ross Sandstone
Formation, together with legacy data and two recent GSI slim-holes (at
Inishcorker and Ballybunion).
This poster focuses on first results from the GSI 09/05 borehole,
located c.4.3 km north of Ballybunion town. This 150
m long slim-hole core intersects the upper Ross Formation as confirmed by
correlation with a measured outcrop section on the adjacent cliff c.1.2 km away.
Correlation is based on goniatite-rich "marine bands", distinctive thick
sandstone units and slump bodies. Three marine bands are identified, the
uppermost being unusually thick (c.4.5 m) and provisionally equated with the R. paucicrenulatum
band marking the top of the Ross Sandstone Formation on Loop Head. The core
records an upward transition from well-bedded sandstones (turbidites and
subordinate hybrid event beds) interpreted as stacked lobe deposits to more
amalgamated sandstones towards the top of the formation indicating increased
channelisation. A major composite slump body (25 m thick) occurs below the
central marine band. This remobilised both sand-prone and silty deposits and is
significantly thicker than any of the slump units identified in the Loop Head
cores and outcrop.
Publication
Down-Dip Termination of the Carboniferous Ross Fan System in the Inner Shannon Area, Western Ireland - New Insight from Core and Outcrop
2015-06, Obradors-Latre, Arnau, Haughton, Peter D. W., Shannon, Patrick M., et al.
Scattered outcrops and limited borehole data in the inner Shannon estuary and mid-Clare are critical to constrain the down-dip extension of the Ross system. Previous outcrop studies have described a much thinner Ross section at Inishcorker and Foynes (over 50 km east of the Ross type section on the Loop Head) involving only the youngest Ross cycles in the west. A re-interpretation of the inner Shannon outcrops is now possible given a new GSI 09/04 borehole in the Inishcorker area, a re-analysis of Foynes Island sections and new biostratigraphic data
Publication
Large-scale, linked drainage systems in the NW European Triassic: insights from the Pb isotopic composition of detrital K-feldspar
2012-05, Tyrrell, Shane, Souders, A. Kate, Daly, J. Stephen, Shannon, Patrick M., Haughton, Peter D. W.
Pb isotopic data from K-feldspars in Middle Triassic (Anisian) sandstones in the Wessex Basin, onshore southwest UK, and the East Irish Sea Basin, some to the north, show that the same grain populations are present. This indicates that the drainage system (the “Budleighensis” River) feeding these basins originated from the same source/s, most probably the remnant Variscan Uplands to the south. Fluvial and aeolian sandstones have the same provenance, suggesting that if water- and wind-driven sands were originally derived from different sources, this has been obscured through reworking prior to final deposition. Significant recycling of feldspar from arkosic sandstones in earlier sedimentary basins can be ruled out. The provenance data agree with previous depositional models, indicating transport distances in excess of , with a drainage pattern that linked separate basins. This supports the idea that the regional fluvial system was driven by topography and episodic flooding events of sufficient magnitude to overcome evaporation and infiltration over hundred’s of kilometres. Importantly, this drainage system appears to have been isolated and independent from those operating contemporaneously to the northwest of the Irish and Scottish massifs, where the remnant Variscan Uplands apparently exerted no influence on drainage or sand supply.
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Publication
Facies Trends and Large-Scale Architecture of the Pennsylvanian Ross Formation, Western Ireland - New Insight from Cores South of the Shannon
2013-12, Obradors-Latre, Arnau, Pierce, Colm, Haughton, Peter D. W., Shannon, Patrick M., et al.
The Ross Formation is well exposed in sea cliffs facing the Atlantic and Shannon estuary
in western Ireland. It forms the sandy deep-water part of a major
shallowing-upward Pennsylvanian succession. Over the last four years, a major
behind-outcrop drilling program targeting the Ross Formation has focussed
primarily on the Loop Head peninsula in west Clare. This has provided a composite
Ross cored section (490 m thick) that underpins a new understanding of bed-scale
variability and the wider vertical evolution of the system. The focus has now shifted
to the key Ballybunion section on the south side of the Shannon, which sits obliquely
down-dip (to the east) of the Loop Head area (c. 18 km away). This area is
important in that previous outcrop studies have suggested that (1) the
character of the lower Ross with its abundant hybrid event beds may reflect a
marginal fringe position; (2) an extra sandy section may be present in the uppermost
Ross due to offset stacking of the youngest lobes and (3) some of the upper
Ross mass transport units may extend across the estuary from Clare. Two new
cores are now available ¿behind¿ the Ballybunion cliff section: a 200 m long PQ
borehole straddling the lower Ross and the upper part of the underlying Clare Shale
(12-KY-UCD-09), and a 151.5 m long slimhole core acquired by the Geological
Survey of Ireland (GSI 09/05). In addition, a re-analysis of the
biostratigraphy is underway. Together the matched pair of Kerry boreholes with
the outcrop section provide a reference section (480 m thick) that can be
compared with the Loop composite section. Both sections have a distinctive
precursor cycle involving first stacked thin mudflows and then outsized and coarse
grained hybrid event beds. The muddier make-up of the latter at Ballybunion is
consistent with a down-dip position based on trends in other basins. The onset of
the main Ross system that follows is sandier at Ballybunion than at Loop
suggesting the former was more axial at this time. Thereafter hybrid event beds
appear not to be as important at Ballybunion. Several of the mass transport
units and condensed sections extend across the Shannon and tie the sections.
Publication
Hybrid Event Bed Character Across the Clare Shale - Basal Ross Formation Contact, Western Ireland - New Insight from Behind-Outcrop Cores
2014-12-22, Obradors-Latre, Arnau, Pierce, Colm, Haughton, Peter D. W., Shannon, Patrick M., et al.
A recent behind - outcrop drilling program targeting the Ross Formation has focussed on the Loop Head peninsula in west Clare. This has provided a fully-cored composite Ross section (490 m thick) that underpins a new understanding of bed-scale variability and the vertical evolution of the system . The work programme h as now been broadened to include the key Ballybunion section on the south side of the Shannon which sits obliquely down-dip (to the east) of Loop Head (c. 18 km away).
Publication
Down-dip Termination of Sandy Fan Systems - New Insight from the Pennsylvanian Ross Sandstone Formation, Western Ireland
2015-12-22, Obradors-Latre, Arnau, Pierce, Colm, Haughton, Peter D. W., Shannon, Patrick M., et al.
New and legacy borehole constraints and outcrop work on the eastward extension of the Ross Formation help constrain the down-dip character of the fan stack.
Publication
Down-dip Termination of Sandy Fan Systems - New Insight from the Pennsylvanian Ross Sandstone Formation, Western Ireland
2016-06-22, Obradors-Latre, Arnau, Pierce, Colm, Haughton, Peter D. W., Shannon, Patrick M., et al.
The Pennsylvanian Ross Sandstone Fm. in western Ireland forms part of a thick (>2200m) progradational and shallowing-upward basin-fill succession. New and legacy borehole constraints and outcrop work on the eastward extension of the Ross help constrain the down-dip character at different levels in the fan stack.
Publication
The Clare Shale - Basal Ross Formation Contact, Western Ireland - New Insight from Behind-Outcrop Cores
2015-02-21, Obradors-Latre, Arnau, Pierce, Colm, Haughton, Peter D. W., Shannon, Patrick M., et al.
A recent behind - outcrop drilling program targeting the Ross Formation has focussed on the Loop Head peninsula in west Clare. This has provided a fully-cored composite Ross section (490 m thick) that underpins a new understanding of bed-scale variability and the vertical evolution of the system . The work programme h as now been broadened to include the key Ballybunion section on the south side of the Shannon which sits obliquely down-dip (to the east) of Loop Head (c. 18 km away).
Publication
Drainage reorganization during breakup of Pangea revealed by in-situ Pb isotopic analysis of detrital K-feldspar
2007-11, Tyrrell, Shane, Haughton, Peter D. W., Daly, J. Stephen
The Pb isotopic composition of detrital K-feldspar grains can be rapidly measured using laser ablation MC-ICPMS. The feldspar Pb signal can survive weathering, transport and diagenesis, and careful targeting avoids problems with inclusions and alteration. As common Pb isotopic compositions show broad (100s km scale) variation across the continents, the method provides a powerful provenance tracer for feldspathic sandstones. Here we combine a new Pb domain map for the circum-North Atlantic with detrital feldspar Pb isotopic data for Triassic and Jurassic sandstones from basins on the Irish Atlantic margin. The Pb compositions reveal otherwise cryptic feldspar populations that constrain the evolving drainage pattern. Triassic sandstones were sourced from distant Archean and Paleoproterozoic rocks, probably in Greenland, Labrador and Rockall Bank to the NW, implying long (>500 km) transport across a nascent rift system. Later Jurassic sandstones had a composite Paleo- and Mesoproterozoic source in more proximal sources to the north (<150 km away). Little or no feldspar was recycled from Triassic into Jurassic sandstones, and the change in provenance is consistent with distributed, low relief Triassic extension in a wide rift, followed by narrower Jurassic rifting with more localised fault-controlled sediment sources and sinks.