Sedimentary and volcano-tectonic processes in the British Paleocene Igneous Province: a review

Brown, David J.; Holohan, Eoghan P.; Bell, Brian R.

doi:10.1017/s0016756809006232

Cited by 26 publications

(21 citation statements)

References 112 publications

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“…Although it remains possible that regional Palaeocene exhumation may contribute to early Cenozoic cooling, further work is needed to isolate this signal from cooling resulting from the cessation of hydrothermal heating, contact effects and more localized exhumation caused by intrusion of central complexes (Brown et al 2009). …”

Section: Implications For Low-temperature Thermal Histories Of Basemementioning

confidence: 99%

Multiple post-Caledonian exhumation episodes across NW Scotland revealed by apatite fission-track analysis

Holford

Green²,

Hillis

et al. 2010

JGS

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14The post Caledonian exhumation history of northwest Scotland is a controversial issue, with 15 some studies advocating largely continual emergence while others suggest dominantly early Abstract 36The origin and development of the high topography bordering the Atlantic margin of NW 37 Europe has long been the subject of debate (Geike, 1901; George, 1966; Doré et al., 2002). 38 The mountains of Scotland and western Scandinavia are characterized by rugged topography 39 and elevations that exceed 1.3 km and 2.4 km respectively and largely comprise rocks that 40 were formed and/or deformed during the Caledonian Orogeny. Numerous lines of evidence 41 indicate that the present-day topography of both regions was initiated by tectonic uplift that 42 began during the Cenozoic or late Mesozoic and which also affected peripheral sedimentary 43 basins (Doré et al., 2002). These include; the transition from deposition of shallow-marine 44 carbonates in the late Cretaceous to rejuvenated clastic sedimentation in the early Palaeogene 45 (Doré et al., 2002)); the easterly tilt of Britain (Brodie & White, 1994) Cretaceous rocks are less widely distributed (Fig. 1), but this is considered to be due 137 Cenozoic uplift and erosion rather than non-deposition (Hallam, 1983 This igneous activity has been attributed to the proto-Iceland mantle plume, and petrological 150 data suggest that a significant proportion (up to 70%) of the melt generated around the British Post-Caledonian exhumation of northwest Scotland 8We present AFTA data from 78 samples collected from onshore and offshore northwest 177 Scotland (Fig. 1 The majority of measured fission track ages are younger than the respective stratigraphic ages 187 (Table 1). Overall there is a consistent trend between fission track age and mean track length, totally anneal all tracks (typically >110°C), followed by a subsequent peak around 90-100°C 245 which leads to shortening of tracks formed after the initial cooling to a mean length of ~10 246 μm. Finally, cooling to a low temperature is followed by reheating to ~70°C, sufficient to 247 reduce track lengths formed after the second episode to ~12-13 μm. Post-Caledonian exhumation of northwest Scotland 11 West Orkney Basin 252Of six Permian-Lower Jurassic samples from offshore shallow boreholes in the WOB, most 253 require two discrete episodes of heating and cooling (Table 2) Post-Caledonian exhumation of northwest Scotland 12The variation of palaeotemperature with depth for the two separate episodes (Fig. 4b (Table 2). An onset of cooling beginning between 225 319 and 190 Ma satisfies all samples that show evidence for this episode (Fig. 3). on this basis for sample GC369-6 predicts total annealing, whereas this sample contains 353 tracks and gives a finite (though very young) fission track age (Fig. 5a) superimposed on a "background" linear profile (Fig. 5b). The rapid fluctuations clearly 366 reflect contact heating around the igneous intrusions. AFTA data in GC369-2 is also 367 interpr...

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Section: Implications For Low-temperature Thermal Histories Of Basemementioning

confidence: 99%

Multiple post-Caledonian exhumation episodes across NW Scotland revealed by apatite fission-track analysis

Holford

Green²,

Hillis

et al. 2010

JGS

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“…Latest Cretaceous uplift predates the first volcanism in the North Atlantic Igneous Province by several millions of years; the earliest lavas, the Antrim basalts in NE Ireland, were erupted at 62.6 ± 0.3 Ma (Ganerød et al, ). The evidence of uplift and erosion prior to the volcanism is widespread in NW Scotland and Northern Ireland, where subaerial Paleocene lavas lie unconformably on Jurassic or Cretaceous rocks (Brown et al, ; Hopson, ; Simms, ; Williamson & Bell, ). The common feature is a clearly erosional unconformity between the brecciated Mesozoic rocks and Paleocene lavas (Williamson & Bell, ).…”

Section: Discussionmentioning

confidence: 99%

Early Cenozoic Denudation of Central West Britain in Response to Transient and Permanent Uplift Above a Mantle Plume

2018

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Upwelling mantle plumes beneath continental crust are predicted to produce difficult to quantify, modest uplift and denudation. The contribution of permanent and transient components to the uplift is also difficult to distinguish. A pulse of denudation in Britain in the Early Paleogene has been linked, although with some controversy, with the arrival of the proto‐Iceland mantle plume. In this contribution we show that combining apatite and zircon (U‐Th‐Sm)/He and apatite fission track analyses from central west Britain with numerical modeling clearly identifies a pulse of early Cenozoic denudation. The data indicate that rock uplift and denudation were centered on the northern East Irish Sea Basin and 1.0–2.4 km of rocks were removed during the latest Cretaceous‐early Paleogene. Uplift and erosion appears to have started a few million years before the earliest magmatism in the region. The regional denudation pattern mirrors the distribution of low‐density magmatic rocks that has been imaged in the deep crust. However, the injection of the underplating melt is not enough to account for the total denudation. An additional regional uplift of at least 300 m is required, which is consistent with a transient thermal effect from the hot mantle plume. The rapid exhumation event ceased by ~40 Ma and the data do not require significant Neogene exhumation.

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“…Given that the Arran Volcanic Formation comprises Palaeogene surface-deposited rocks juxtaposed against Devonian and Permo-Triassic rocks, it must occupy a caldera Easting 194,494 194,504 194,276 194,335 198,373 198,490 198,376 193,937 194,242 Northing 633 which has experienced at least some degree of downfaulting and must therefore possess at least one ring fault. Although this fault is not exposed, the complex meets the other criteria of Brown et al (2009) for recognising a caldera in the British Palaeogene Igneous Province: (1) a collapse succession of breccias; and (2) evidence of subsidence (i.e. displacement relative to country rocks).…”

Section: Collapse (And Resurgence?) Of the Calderamentioning

confidence: 94%

“…Other Palaeogene remnants of the North Atlantic Igneous Province are preserved on Greenland, the Faroe Islands and offshore (Saunders et al 1997). Although the majority of magmatism in the British Palaeogene Igneous Province is preserved as basaltic lavas and gabbroic and granitic intrusions, there is widespread evidence of extrusive silicic volcanism and explosive eruptions (Bell and Emeleus 1988;Brown et al 2009). Due in part to its historical importance and relative ease of access, the British Palaeogene Igneous Province has been the source of many developments in the global understanding of volcanological processes.…”

Section: Why the Isle Of Arran?mentioning

confidence: 99%

“…Pyroclastic rocks in the British Palaeogene Igneous Province are largely found within calderas (on Mull and Rùm, as well as Skye and Arran), often bound by arcuate faults and intrusions, originally interpreted as ring faults, ring dykes and cone sheets. Detailed studies of the pyroclastic successions on Skye and Rùm have revealed complex histories of caldera collapse in the British Palaeogene Igneous Province (Troll et al 2000;Holohan et al 2009;Brown et al 2009), but exposures in these areas are limited due to later, cross-cutting layered intrusions. Recently, many silicic extrusive rocks in this province, previously described as lavas or shallow intrusions, have been re-interpreted as welded and rheomorphic lava-like ignimbrites, for example the rhyodacite sheets on Rùm (Troll et al 2000;Holohan et al 2009) and the Sgurr of Eigg Pitchstone (Brown and Bell 2013).…”

Section: Why the Isle Of Arran?mentioning

confidence: 99%

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A proximal record of caldera-forming eruptions: the stratigraphy, eruptive history and collapse of the Palaeogene Arran caldera, western Scotland

et al. 2018

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Caldera-forming volcanic eruptions are among the most dangerous, and can generate extensive pyroclastic deposits and deliver ash into global atmospheric circulation systems. As calderas collapse, the eruptions can deposit thick proximal ignimbrite sequences and thinner ignimbrites more distally. However, the proximal record of caldera collapse is often obscured by later intrusions, volcanism, faults, alteration, water and sediments, which significantly limits our understanding of these eruptions. A Palaeogene caldera system in central Arran, western Scotland, preserves a rare proximal caldera-fill succession, the Arran Volcanic Formation. This caldera largely comprises highly heterogeneous ignimbrites and minor intra-caldera sedimentary rocks. The current level of erosion, and the general absence of faults, intrusions and sediments, allows a complex stratigraphy and collapse history to be determined, which can be linked to changing eruptive styles at a constantly evolving volcano. The first recorded phase was eruption of a homogeneous rhyolitic lava-like tuff, deposited from high temperature, high mass-flux pyroclastic density currents generated from low fountaining columns that retained heat. A succeeding phase of highly explosive Plinian eruptions, marked by a thick blanket of massive lapilli tuffs, was then followed by piston-like caldera collapse and erosion of steep caldera walls. Volcanism then became generally less explosive, with predominantly lava-like and eutaxitic tuffs and cognate spatter-rich agglomerates interbedded with non-homogenous lapilli tuffs. High topographic relief between distinct units indicate long periods of volcanic quiescence, during which erosive processes dominated. These periods are, in several places, marked by sedimentary rocks and evidence for surface water, which includes a localised basaltic-andesitic phreatomagmatic tuff. The caldera-forming eruptions recorded by the Arran Volcanic Formation provide an important insight into caldera collapse processes and proximal ignimbrite successions. The lack of thick autobreccias and lithic-rich lapilli-and block-layers indicates that subsidence was relatively gradual and incremental in this caldera, and not accompanied by catastrophic wall collapse during eruption. The relatively horizontal nature of the caldera-fill units and paucity of intra-caldera faulting indicate that piston subsidence was the dominant method of collapse, with a relatively coherent caldera floor bounded by a steeply dipping ring fault. Possible resurgence may have caused later doming of the floor and radial distribution of subsequent ignimbrites and sedimentary rocks. Our work emphasises the continued need for field studies of caldera volcanoes.

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Sedimentary and volcano-tectonic processes in the British Paleocene Igneous Province: a review

Cited by 26 publications

References 112 publications

Multiple post-Caledonian exhumation episodes across NW Scotland revealed by apatite fission-track analysis

Multiple post-Caledonian exhumation episodes across NW Scotland revealed by apatite fission-track analysis

Early Cenozoic Denudation of Central West Britain in Response to Transient and Permanent Uplift Above a Mantle Plume

A proximal record of caldera-forming eruptions: the stratigraphy, eruptive history and collapse of the Palaeogene Arran caldera, western Scotland

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