Template:P916111
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Development phase | Location, lithofacies and thickness | Main events | |
11 | Marine transgression | Post-BVG Marginal to Lake District in late Caradoc times; S Lake District in Ashgill |
Thermal contraction of granites on cooling allowed progressive marine transgression on to Lake District block |
10 | Batholith emplacement | Beneath Scafell and Haweswater calderas. Granite, microgranite and granodiorite | Injection of thick tabular granite sheets resulting in uplift and erosion of volcanic field |
9b | Cross Fell | Cross Fell Inlier. Volcaniclastic sedimentary and pyroclastic rocks, one major sheet of silicic lapilli-tuff; >1100 m | Volcaniclastic sedimentation interspersed with sporadic pyroclastic eruptions |
9a | Gosforth succession | West Cumbria: stratiform sequence of andesitic and dacitic lapilli-tuff with subordinate volcaniclastic sedimentary rocks and andesite sills; >2500 m | Dominantly explosive intermediate and silicic pyroclastic activity producing many densely welded ignimbrites; ?caldera related |
8 | Helvellyn Basin succession | Central Fells, Helvellyn Basin. Stratiform units of volcaniclastic sandstone and breccia; subordinate pyroclastic units and a silicic lava; >1600 m | Fluviolacustrine sedimentation within extensional basin with episodic catastrophic influx of eruption-generated sediment-gravity flows; interrupted by small andesite lava shields and ignimbrite emplacement |
7 | Lincomb Tarns ignimbrite | Throughout BVG. Eutaxitic and parataxitic dacitic lapilli-tuff; columnar jointed; >800 m |
Most widespread and voluminous ignimbrite within BVG. Large magnitude silicic pyroclastic eruptions forming ignimbrite shield |
6 | Ambleside Basin succession | Central south Lake District. Oversteps 5a, b, 4a; bedded volcaniclastic sandstone and breccia; >1100 m | Fluviolacustrine sedimentation dominated by catastrophic influx of eruption generated sediment-gravity flows. ?Associated with emplacement of many sills |
5b | Kentmere Basin succession | SE Lake District. Bedded units of volcaniclastic sedimentary rocks, intercalated with sheets of pyroclastic rocks, some lavas; <2800 m | Intermediate to silicic ignimbrites; andesitic tuff-cone and lava-shield; fluviolacustrine sedimentation at base; major centre for sill emplacement |
5a | Duddon Basin succession | SW Lake District. Stratified sequence of volcaniclastic sedimentary rocks, andesitic and rhyolitic pyroclastic rocks and andesite lavas | Explosive intermediate ?caldera-related pyroclastic eruptions; succeeded by catastrophic eruption-generated sedimentation in extensional basin, episodically interrupted by emplacement of silicic ignimbrites. Many sills emplaced? |
4b | Haweswater Caldera succession | Ullswater, Haweswater. Stratified sheets of dacitic and rhyolitic pyroclastic rocks; garnetiferous; <650 m | Large magnitude silicic pyroclastic activity; large-volume ignimbrites associated with caldera collapse |
4a | Scafell Caldera succession | Central Fells. Stratified sheets of andesitic, dacitic and rhyolitic pyroclastic rocks; dacite and rhyolite lavas; garnetiferous. Overlain by bedded volcaniclastic sandstone and breccia; >700 m | Andesitic phreatoplinian eruption followed by sequence of large volume silicic ignimbrites with associated development of piecemeal hydrovolcanic caldera; postcaldera silicic lavas and caldera basin sedimentary infill |
3 | Monogenetic andesite volcanoes | Throughout BVG. Andesite lavas and sills, some of basalt, basaltic andesite and dacite; subordinate tuff, lapilli-tuff and sandstone; some units garnetiferous; <2700 m | Construction of subaerial, multiple-vent, low-profile andesite volcanoes; some high volume basalt lava-fields; episodic silicic volcanism including possible caldera formation |
2 | Initial phreato- magmatism | Devoke Water, Calder Bridge, Millom Park, Ullswater. Mafic lapilli-tuff and tuff-breccia; contains much mudstone and sandstone from Skiddaw Group; <600 m | Hydrovolcanism, construction of tuff-cone field(s) |
1 | Pre-volcanic | Latterbarrow Sandstone and Overwater Siltstone locally preserved; 0–400 m | Regional uplift and erosion of Skiddaw Group. Local evidence of fluvial and ?marine deposition |