2. 3. Caledonian Orogenesis

4. 1. Caledonian Orogeny 2. Variscan Orogeny 4. Alpine Orogeny 3. North Atlantic Tertiary Igneous Province (NATP)

5. 1. Caledonian Orogeny 2. Variscan Orogeny 4. Alpine Orogeny 3. North Atlantic Tertiary Igneous Province (NATP)

6. Pre-Cambrian 1. Major differences in the age and character of the Precambrian (basement) rocks. Precambrian rocks no older than 700 MYA in most of southern Britain and Ireland Precambrian rocks as old as 2500 MYA in northern Britain 2. Palaeomagnetic evidence. Evidence for the interpretation that northern and southern Britain were on two different continents: (Palaeomagnetism is magnetism trapped in certain rocks at their time of formation. It can give an indication of a continent’s palaeolatitude.) 10ºS

7. Cambrian 544 – 510 MYA – Caledonian Orogenesis Evidence for the existence of a widening oceanic area separating northern and southern Britain: 1. Palaeomagnetic evidence gives latitude.

8. Cambrian 3. Contrasts in sedimentary environments between the two areas e.g. Durness Lst. 2. Fossil contrasts, especially trilobites such as Olenellus, found only in Scotland. Evidence for the existence of a widening oceanic area separating northern and southern Britain: 1. Palaeomagnetic evidence gives latitude.

11. Cambrian 3. Contrasts in sedimentary environments between the two areas e.g. Durness Lst. 2. Fossil contrasts, especially trilobites such as Olenellus, found only in Scotland. Evidence for the existence of a widening oceanic area separating northern and southern Britain: 1. Palaeomagnetic evidence gives latitude. 4. Absence of andesitic and rhyolitic volcanic lavas suggests a widening ocean and no subduction.

12. Ordovician 510 - 439MYA Northern Britain & Southern Britain separated by the 3,500km Iapetus Ocean Laurentia remained stationary approx 10ºS of Equator whilst Avalonia (containing England & Wales) drifted away from Gondwana to approx 40ºS. Subduction occurring under both continents, causing the Iapetus to close. Island-arc volcanism Evidence: Palaeomagnetism Distinct trilobite faunal provinces Durness Lst in Scotland Volcanic rocks in Lake District Ophiolites at Ballantrae and Arran in Scotland Accretionary prism – Southern Uplands in Scotland

13. Silurian 439 – 409 MYA

14. Aim: Show how the study of geology can provide evidence for the tectonic regime active in Britain during the Lower Palaeozoic. Caledonian Orogenesis 1. Name the orogenic belt that formed in Britain during the Lower Palaeozoic. 2. When was this orogenesis completed by? 3. What two continents collided during this orogenesis? 4. What was the ocean that was destroyed? 5. What areas in Britain were affected? 6. What is the general trend of the structures formed in this orogenesis? 7. What is the name of the continent that formed after this collision? 8. What was the name of the mountain chain formed? 9. At what latitude did these two continents collide at?

15. Iapetus Suture Laurentia (Northern Britain) Avalonia (Southern Britain) Cambrian ~550 Ma

16. Iapetus Suture Laurentia (Northern Britain) Avalonia (Southern Britain) Early Ordovician ~490 Ma

17. Iapetus Suture Laurentia (Northern Britain) Avalonia (Southern Britain) Early Silurian ~440 Ma

18. Iapetus Suture Laurentia (Northern Britain) Avalonia (Southern Britain) Devonian ~400 Ma

19. Subduction Zones Orogenic Belts Does not melt unless young (<3 Ma) Dehydration of slab cools it and increases its density 400km phase change olivine to spinel (10% denser) 670km phase change spinel to perovskite (10% denser) Slab pull forces increase Reabsorbed into mantle by subduction Cooling, thickening & becomes denser as it moves away from MOR Dewatering of slab lowers MTP of mantle wedge causing it to partially melt

22. Caledonian Orogenesis (Lower Palaeozoic) HinterlandInner Zone Outer Zone Foreland

23. Show how the study of geology provides evidence for the tectonic regime active in Britain during the Lower Palaeozoic.(25 marks) Geology = Rock types + geological structures Igneous Rocks – Andesites & Rhyolites in Cumbria (BVG) or North Wales (Snowdonia) Metamorphic Rocks – Slate in North Wales & Cumbria, & Schists in Scotland Sedimentary Rocks – Black Shales (Skiddaw Slates) Folds – Harlech Dome, Shap Fell, Tebay & Tay Nappe Faults – Moine Thrust Trends - Intrusions – Skiddaw Granite or Cairngorms Accretionary Prism – Southern Uplands Ophiolites – Ballantrae Complex

24. With reference to a named orogenic belt in Britain, explain how a study of the geology enables a reconstruction of the plate tectonic regime in which it developed. (25 marks) Named Orogenic Belt in Britain ? EraPeriodOrogeny CenozoicQuaternary Tertiary ALPINE (40 MYA) MesozoicCretaceous Jurassic Triassic Upper Palaeozoic Permian Carboniferous Devonian VARISCAN (300 MYA) Lower Palaeozoic Silurian Ordovician Cambrian CALEDONIAN (400 MYA)

25. With reference to a named orogenic belt in Britain, explain how a study of the geology enables a reconstruction of the plate tectonic regime in which it developed. (25 marks) Geology = Rock types + geological structures Sedimentary Rocks – Black Shales (Skiddaw Slates) Igneous Rocks – Andesites & Rhyolites in Cumbria (BVG) or North Wales (Snowdonia) Metamorphic Rocks – Slate in North Wales & Cumbria, & Schists in Scotland Folds – Harlech Dome, Shap Fell, Tebay & Tay Nappe Faults – Moine Thrust Intrusions – Skiddaw Granite or Cairngorms Accretionary Prism – Southern Uplands Ophiolites – Ballantrae Complex

26. Tectonic Structures of the Caledonian Orogenesis Moine Thrust Belt Great Glen Fault Highland Boundary Fault Southern Uplands Fault Tay Nappe

27. Caledonian Faults Moine Thrust Belt NE-SW strike 200km long 0-12km wide up to 150km displacement 435-425 Mya

28. Moine Thrust Belt

29. Caledonian Faults Great Glen Fault NE-SW strike 150km long strike-slip fault sinistral >100km displacement 430-425 Mya Highland Boundary Fault NE-SW strike Reverse fault Allowed Midland Valley to descend as major rift by 4,000m Sinistral displacement 430-424 Mya

30. Caledonian Faults Southern Uplands Fault NE-SW strike Reverse fault Allowed Midland Valley to descend as major rift by 4,000m Sinistral displacement 430-424 Mya

31. Caledonian Faults

32. Tay Nappe

34. Ballantrae Ophiolite Complex

37. 1. North-west Highlands Torridonian rocks – 1 billion – 770 million years old Fragmental, red-brown in colour. Coarse-grained sand & pebbles, with some thin layers of finer grained red mudstone. Grains sub-rounded to rounded. Sandstone layers are many metres thick and commonly show clear cross-bedding. Horizontal to gently dipping strata. Lewisian rocks – 3 – 1.8 billion years old Coarse-grained, crystalline rock, in which the crystals can easily be seen with the naked eye. Stripy appearance – with alternating darker and paler stripes. Darker stripes made of minerals such as hornblende and biotite, white or pink stripes made up of quartz and feldspar. Eriboll rocks – 500 million years old Rocks white to pink on fresh surfaces, but typically weathers to a grey colour. Made up of almost entirely of grains of quartz, which are cemented tightly together to form a very hard rock. These rocks are broken into loose, angular blocks forming scree slopes. The lower layers (oldest) show cross-bedding and fossilised symmetrical ripples. The upper (younger) layers contain vertical “pipes” a few centimetres in length and ½cm to 1 cm wide. Fossil trilobite Olenellus can also be found. Durness rocks – 450 million years old Grey, crystalline rock which is creamy yellow in places. Dissolves fairly readily in rainwater to produce caves. Fizzes with HCl acid. Rock contains stromatolites (sediment mounds bound together by algae) and ooliths (small-spherical growths of CaCO 3 upto 2mm).

38. Lewisian rocks – 3 – 1.8 billion years old

39. Torridonian rocks – 1 billion - 770 million years old

40. Eriboll rocks – 500 million years old Lower layers

41. Eriboll rocks – 500 million years old Upper layers

42. Durness rocks – 450 million years old

43. 2. Northern Highlands Moine rocks – 1 billion – 870 million years old Crystalline rocks, medium to coarse-grained. Silvery grey in colour. Abundant flakes of muscovite and biotite mica, which are aligned into parallel layers (foliated). Lower layer of Moine rocks Hard, crystalline & fine-grained rock. Light grey in colour with a streaked out texture due to the elongation of the minerals. Intensely deformed and folded dating to 450 million years.

44. Moine rocks – 1 billion to 870 million years old

45. Lower layer

48. 3. Grampian Highlands Dalradian rocks – 750 – 480 million years old A mixture of rocks which have been intensely folded and metamorphosed. Repeated fining-upward sequences, with coarse-grained sands at the base often with flute casts and tool marks, and fine-grained silts and clays at the top. Hard and re-crystalline in places. Tay Nappe Complex overfolds and huge nappes. Locally geology has become inverted. Trend of fold axis is NE to SW, with fold amplitudes of up to 10km from trough to crest. Cairngorm rocks – 400 million years old Crystalline rocks, interlocking and coarse-grained. Mineralogically composed of quartz and feldspar, which are randomly orientated. Relatively undeformed and approximately 400 mya. Lochranza, Isle of Arran – Greenish tinge to rocks. Fine-grained and re-crystalline. Chlorite mica minerals which are clearly aligned. Ballachulish, Glencoe – dark grey and black in colour, very fine-grained. Re-crystalline muscovite mica minerals. Fine layering visible throughout rock.

49. Cairngorm rocks – 400 million years old

50. Dalradian rocks – 400 million years old

51. 5. Southern Uplands Southern Uplands – 470 -420 million years old Rocks have been weakly metamorphosed. Great majority of older rocks are coarse-grained greywackes with smaller amounts of finer siltstones, mudstones, shale, volcanic ash and lavas. Metamorphism of fine-grained rocks (mudstone and shale) has produced slate. Greywacke, a grey, black, dark-green or deep-purplish hard rock, is coarse-grained and poorly sorted. It contains angular fragments of quartz, feldspar, ferromagnesian minerals and igneous and metamorphic rock fragments held together in a dark mud or clay matrix. Low grade metamorphism has re-crystallised the cement to produce a tough hard rock which often looks like an igneous rock. Southern Upland greywackes are divided into 3 main zones, separated by faults that run NE-SW, parallel to the strike of the beds. Overall the beds get younger to the SE. The many NE-SW trending faults all have their downthrow side on the SE. Within each of the 30 or so fault blocks, the oldest beds are on the SE side, but the blocks get progressively older towards the NW. These faults dip towards the NE and get progressively steeper towards the NE. Fossils are restricted to the fine sediments, where dead animal remains would have been preserved by slow accumulation of mud in an oxygen-deficient environment. The most abundant fossils are the graptolites. No fossils occur in the greywackes.

52. 6. Lake District Skiddaw Group – 470 million years old Weakly metamorphosed greywackes, sandstones, siltstones and mudstones. Fine-grained rocks clearly foliated. Uniform grey colour. Approx. 3km thick. Very few fossils. Intensely folded. Igneous Intrusions – 400 million years old Undeformed batholith emplaced at a depth of 5kn. Now exposed due to erosion and uplift. Coarse-grained and felsic in colour. Found at Shap. Skiddaw, Ennerdale and Eskdale. Gravity anomaly data suggests that these intrusions all join up to form one large batholith. Borrowdale Volcanic Group – 450 million years old 6km thick sequence of volcanic rocks – mostly andesite and tuffs, with ignimbrites and welded tuffs. Windermere Supergroup – 440 - 420 million years old Limestones and thick turbidite sequences of sandstones, siltstones and mudstones, weakly metamorphosed and folded. e.g. Shap Fell and Jeffrey’s Mount, Tebay – evidence of tectonic folding, with fold axes trending NE-SW.

53. 7. North Wales & Anglesey Cambrian Rocks – 500 million years old Thick sequences of marine sandstones and shales, weakly metamorphosed. Many of the sandstones such as the Rhinog Grits are greywackes. Above this the sediments grade into fine-grained shales now forming the Llanberis Slates. Ordovician Rocks – 450 million years old Volcanic rocks containing rhyolites and andesites, and tuffs. Outcrops trend in a NE to SW direction. In some areas many of the volcanic rocks are welded ash flows. All sediments have been gently folded into large open antiforms and synforms. E.g Harlech Dome. The strike of the axial planes is NE-SW. Anglesey Rocks – 580 – 550 million years old Schists with metamorphic minerals indicating high pressure and low temperature conditions. These schists were orinally fine-grained shales and medium-grained sandstones.