CHAPTER XXVIII

Illustrative Examples of the Carboniferous Puys of Scotland

The Basin of the Firth of Forth--North Ayrshire--Liddesdale 462

LIST OF ILLUSTRATIONS

FIG. PAGE

1. Vesicular structure, Lava from Ascension Island, slightly less than natural size 15

2. Elongation and branching of steam-vesicles in a lava, Kilninian, Isle of Mull, a little less than natural size 17

3. Microlites of the Pitchstone of Arran (magnified 70 diameters) 19

4. Perlitic structure in Felsitic Glass, Isle of Mull (magnified) 19

5. Spherulitic structure (magnified) 19

6. Micropegmatitic or Granophyric structure in Granophyre, Mull (magnified) 20

7. Ophitic structure in Dolerite, Gortacloghan, Co. Derry (magnified) 20

8. Variolitic or orbicular structure, Napoleonite, Corsica (nat. size) 22

9. Flow-structure in Rhyolite, Antrim, slightly reduced 23

10. Lumpy, irregular trachytic lava-streams (Carboniferous), East Linton, Haddingtonshire 24

11. View at the entrance of the Svinofjord, Faroe Islands, illustrating the terraced forms assumed by basic lavas 25

12. Sack-like or pillow-form structure of basic lavas (Lower Silurian), Bennan Head, Ballantrae, Ayrshire 26

13. Alternations of coarser and finer Tuff 34

14. Alternations of Tuff with non-volcanic sediment 35

15. Ejected block of basalt which has fallen among Carboniferous shales and limestones, shore, Pettycur, Fife 37

16. Effects of denudation on a Vesuvian cone 40

17. Section to illustrate the structure of the Plateau type 43

18. Diagram illustrating the structure and denudation of Puys 45

19. Section illustrating submarine eruptions; alternations of lavas and tuffs with limestones and shales full of marine organisms 48

20. Diagram illustrating volcanic eruptions on a river-plain 49

21. Diagram illustrating volcanic eruptions on a land-surface 50

22. Ground-plans of some volcanic vents from the Carboniferous districts of Scotland 55

23. View of an old volcanic "Neck" (The Knock, Largs, Ayrshire, a vent of Lower Carboniferous age) 56

24. Section of neck of agglomerate, rising through sandstones and shales 58

25. Neck filled with stratified tuff 64

26. Section of neck of agglomerate with plug of lava 65

27. Section of agglomerate neck with dykes and veins 66

28. Section of neck filled with massive rock 68

29. Successive shiftings of vents giving rise to double or triple cones 70

30. Section to show the connection of a neck with a cone and surrounding bedded tuffs 71

31. Diagram illustrating the gradual emergence of buried volcanic cones through the influence of prolonged denudation 75

32. Dyke, Vein, and Sill 80

33. Section of Sill or Intrusive Sheet 83

34. Ideal section of three Laccolites. (After Mr. Gilbert) 86

35. Diagram illustrating the stratigraphical relations of the pre-Cambrian and Cambrian rocks of the North-west Highlands of Scotland 112

36. Map of a portion of the Lewisian gneiss of Ross-shire 118

37. Section showing the position of sills in the mica-schist series between Loch Tay and Amulree 124

38. Sketch of crushed basic igneous rock among the schists, E. side of Porth-tywyn-mawr, E. side of Holyhead Straits 128

39. Section across the Uriconian series of Caer Caradoc 132

40. Map of the volcanic district of St. David's 146

41. Section showing the interstratification of tuff and conglomerate above Lower Mill, St. David's 154

42. Basic dyke traversing quartz-porphyry and converted into a kind of slate by cleavage. West side of Llyn Padarn 162

43. Section of well-cleaved tuff, grit and breccia passing up into rudely-cleaved conglomerate and well-bedded cleaved fine conglomerate and grit. East side of Llyn Padarn 163

44. Section of Clegyr on the north-east side of Llyn Padarn, near the lower end 164

45. Section across the Cambrian formations of the Malvern Hills, showing the position of the intercalated igneous rocks. After Phillips 170

46. Section across Rhobell Fawr 178

47. Section at the Slate Quarry, Penrhyn Gwyn, north slopes of Cader Idris 180

48. Sketch-section across Cader Idris 182

49. Section across the Moelwyn Range 185

50. Section across the anticline of Corndon 190

51. Structure in finely-amygdaloidal diabase lava, south of mouth of Stinchar River, Ayrshire 193

52. View of Knockdolian Hill from the east 194

53. Section across the Lower Silurian volcanic series in the south of Ayrshire (B. N. Peach) 197

54. Section of part of the Arenig volcanic group, stream south of Bennane Head, Ayrshire 198

55. Flow-structure in the lowest felsite on the track from Llanberis to the top of Snowdon 211

56. Section of Snowdon 212

57. Section across the Berwyn Hills. (Reduced from Horizontal Section, Geol. Surv. Sheet 35) 219

58. Section of the strata on the shore at Porth Wen, west of Amlwch 223

59. Section of intercalated black shale in the volcanic series at Porth yr hwch, south of Carmel Point, Anglesey 224

60. Green slates overlain with volcanic breccia, Carmel Point 224

61. Blue shale or slate passing into volcanic breccia east of Porth Padrig, near Carmel Point 225

62. Section of felsites in the Coniston Limestone group, west of Stockdale 232

63. Fine tuff with coarser bands near Quayfoot Quarries, Borrowdale 234

64. Diagram of the general relations of the different groups of rock in the Lower Silurian volcanic district along the western shore of Lough Mask 253

65. Veins and nests of sandstone due to the washing of sand into fissures and cavities of an Old Red Sandstone lava. Turnberry Point, Ayrshire 283

66. Ground-plan of reticulated cracks in the upper surface of an Old Red Sandstone lava filled in with sandstone. Red Head, Forfarshire 284

67. Section across the volcanic series of Forfarshire 286

68. Section across two necks above Tillicoultry, Ochil Hills 288

69. Section of the granite core between Merrick and Corscrine 290

70. Section across the three Dirrington Laws, Berwickshire 291

71. Section of Papa Stour, Shetlands, showing sill of spherulitic felsite traversing Old Red Sandstone and bedded porphyrites (Messrs. Peach and Horne) 292

72. Section across Northmavine, from Okrea Head to Skea Ness, Shetland, showing dykes and connected sill of granite and felsite (Messrs. Peach and Horne) 292

73. Section at the edge of one of the bays of Lower Old Red Sandstone along the northern margin of Lake Caledonia, near Ochtertyre 295

74. Craig Beinn-nan-Eun (2067 feet), east of Uam Var, Braes of Doune. Old Red Conglomerate, with the truncated ends of the strata looking across into the Highlands; moraines of Corry Beach in the foreground 296

75. Section showing the top of the volcanic series at the foot of the precipice of the Red Head, Forfarshire 300

76. Andesite with sandstone veinings and overlying conglomerate. Todhead, south of Caterline, coast of Kincardineshire 303

77. Section across the Boundary-fault of the Highlands at Glen Turrit, Perthshire 305

78. Section across the chain of the Sidlaw Hills near Kilspindie 306

79. Section across the Eastern Ochil Hills from near Newburgh to near Auchtermuchty 307

80. Generalized section across the heart of the Ochil Hills from Dunning on the north to the Fife coal-field near Saline on the south 308

81. Diagram of the volcanic series of the Western Ochil Hills 309

82. View of Cnoc Garbh, Southend, Campbeltown. A volcanic neck of Lower Old Red Sandstone age, about 400 yards wide in its longer diameter 312

83. Section of volcanic series on beach, Southend, Campbeltown 313

84. Section of the base of the volcanic series, Reclain, five miles south of Pomeroy 316

85. Section of shales and breccias at Crossna Chapel, north-east of Boyle 316

86. Section across the north end of the Pentland Hills, from Warklaw Hill to Pentland Mains. Length about five miles 318

87. View of the lava-escarpments of Warklaw Hill, Pentland chain, from the north-west 319

88. Section across the Pentland Hills through North Black Hill and Scald Law. Length about three miles 322

89. Section from the valley of the Gutterford Burn through Green Law and Braid Law to Eight-Mile Burn 322

90. Section across the north end of the Pentland Hills, and the southern edge of the Braid Hill vent. Length about two miles 324

91. Section across the northern end of the Biggar volcanic group, from Fadden Hill to beyond Mendick Hill 326

92. Section across the southern part of the Biggar volcanic group from Covington to Culter 328

93. Section from Thankerton Moor across Tinto to Lamington 328

94. Section across the Duneaton volcanic district from the head of the Duneaton Water to Kirklea Hill 330

95. Cavernous spaces in andesite, filled in with sandstone, John o' Groats Port, Turnberry, Ayrshire 333

96. Section of andesites, Turnberry Castle, Ayrshire 334

97. Lenticular form of a brecciated andesite (shown in Fig. 96), Turnberry, Ayrshire 334

98. Section across the volcanic area of St. Abb's Head (after Prof. J. Geikie) 339

99. View of terraced andesite hills resting on massive conglomerate, south of Oban 341

100. Section of lava-escarpment at Beinn Lora, north side of mouth of Loch Etive, Argyllshire 342

101. Section across Strathbogie, below Rhyme, showing the position of the volcanic band 344

102. View of Knockfeerina, Limerick, from the north-east--a volcanic neck of Upper Old Red Sandstone age 349

103. Section of the volcanic zone in the Upper Old Red Sandstone, Cam of Hoy, Orkney 351

104. Section of the volcanic zone in the Upper Old Red Sandstone at Black Ness, Rackwick, Hoy 351

105. Section across the volcanic band and its associated necks, Hoy, Orkney 352

106. Ground-plan of volcanic neck piercing the Caithness Flagstone series on the beach near John o' Groat's House 353

107. View of the escarpment of the Clyde Plateau in the Little Cumbrae, from the south-west 368

108. View of the edge of the Volcanic Plateau south of Campbeltown, Argyllshire 370

109. View of North Berwick Law from the east, a phonolite neck marking one of the chief vents of the Garleton Plateau. (From a photograph) 371

110. The Bass Rock, a trachytic neck belonging to the Garleton plateau, from the shore at Canty Bay 372

111. Corston Hill--a fragment of the Midlothian Plateau, seen from the north 373

112. View of Arthur Seat from Calton Hill to the north 374

113. View of Arkleton Fell, part of the Solway Plateau, from the south-west 376

114. Vertical sections of the escarpment of the Clyde plateau from north-east to south-west 384

115. Section of Craiglockhart Hill, Edinburgh 387

116. Section of the bottom of the Midlothian Plateau, Linnhouse Water above Mid-Calder Oilworks 387

117. Section of the top of the Midlothian Plateau in the Murieston Water 388

118. Section of Calton Hill, Edinburgh 389

119. Cliff of tuff and agglomerate, east side of Oxroad Bay, a little east from Tantallon Castle, East Lothian 391

120. Section across part of the Clyde Plateau to the west of Bowling (reduced from Sheet 6 of the Horizontal Sections of the Geological Survey of Scotland) 392

121. Diagram illustrating the thinning away southwards of the lavas of the Clyde Plateau between Largs and Ardrossan. Length about 10 miles 393

122. Diagram illustrating the thinning away eastwards of the lavas of the Clyde Plateau in the Fintry Hills. Length about 12 miles 394

123. View of the two necks Dumgoyn and Dumfoyn, Stirlingshire, taken from the south 395

124. Ground-plan of Plateau-vents near Strathblane, Stirlingshire, on the scale of 6 inches to a mile 395

125. Ground-plans of double and triple necks in the Plateau series, on the scale of 6 inches to a mile 396

126. Ground-plan of tuff-neck, shore east of Dunbar 398

127. Section across the vents Dumgoyn and Dumfoyn, and the edge of the Clyde plateau above Strathblane, Stirlingshire 400

128. Section through the large vent of the Campsie Hills 400

129. Diagrammatic section across the central vent of the Clyde plateau in Renfrewshire 400

130. Section across Southern Berwickshire, to show the relation of the volcanic plateau to the vents lying south from it 401

131. Section of south end of Dumbuck Hill. East of Dumbarton 403

132. Section across the East Lothian plateau, to show the relative position of one of the necks 403

133. View of Traprain Law from the south, a phonolite neck of the Garleton Plateau 405

134. Veins and dykes traversing the agglomerate and tuff of the great Renfrewshire vent 408

135. "The Yellow Man," a dyke in volcanic tuff and conglomerate on the shore a little east of North Berwick 409

136. Trachytic sills, Knockvadie, Kilpatrick Hills 410

137. Section across the edge of the Clyde plateau, south-east of Beith 411

138. Section across the upper part of the Clyde plateau at Kilbirnie, Ayrshire 411

139. Section across the upper surface of the Clyde volcanic plateau, Burnhead, north-west of Kilsyth 412

140. Section across the upper surface of the Clyde volcanic plateau at Campsie 412

141. Section across western edge of the Garlton plateau 412

142. Section across the Solway plateau 413

143. Section of volcanic vent at East Grange, Perthshire coal-field, constructed by Mr. B. N. Peach from the rocks exposed in a railway-cutting, and from plans of ironstone- and coal-pits 426

144. View of the Binn of Burntisland--a volcanic neck of agglomerate 428

145. View of part of the cliffs of vertical agglomerate, Binn of Burntisland 431

146. Diagram of buried volcanic cone near Dalry, Ayrshire. Constructed from information obtained in mining operations 434

147. Diagram to illustrate how Volcanic Necks may be concealed and exposed 434

148. Section across the Saline Hills, Fife 435

149. Section across the Binn of Burntisland, in an east and west direction 436

150. Section in old quarry, west of Wester Ochiltree, Linlithgowshire. Calciferous Sandstone series 437

151. Ejected volcanic block in Carboniferous strata, Burntisland 438

152. View of volcanic agglomerate becoming finer above east end of Kingswood Craig, two miles east from Burntisland 439

153. Alternations of basalt and tuff, with shale, etc., of Kingswood Craig, Burntisland 441

154. Section of the upper surface of a diabase ("leckstone") sheet, Skolie Burn, south-east of Bathgate 443

155. Section across the volcanic ridge of the Linlithgow and Bathgate Hills, showing the intercalation of limestones that mark important stratigraphical horizons 444

156. Section in Wardlaw Quarry, Linlithgowshire 445

157. Section from Linlithgow Loch to the Firth of Forth 446

158. Section across the Campsie Fells illustrating the contrast between the sills below and above the plateau-lavas 447

159. Section showing the position of the basic sills in relation to the volcanic series at Burntisland, Fife 448

160. Sills between shales and sandstones, Hound Point, Linlithgowshire 449

161. Section of Sill, Cramond Railway, Barnton, near Edinburgh 450

162. Intrusive dolerite sheet enclosing and sending threads into portions of shale, Salisbury Crags, Edinburgh 452

163. Intrusive sheet invading limestone and shale, Dodhead Quarry, near Burntisland 452

164. Spheroidal weathering of dolerite sill, quarry east of North Queensferry, Fife. 455

165. Two thin sills of "white trap" injected into black carbonaceous shale overlying the Hurlet Limestone, Hillhouse Quarry, Linlithgow 456

166. Dyke cutting the agglomerate of a neck. Binn of Burntisland 457

167. Boss of diabase cutting the Burdiehouse Limestone and sending sills and veins into the overlying shales. Railway cutting, West Quarry, East Calder, Midlothian 458

168. Side of columnar basalt-dyke in the same agglomerate as in Fig. 166 459

169. Dyke rising through the Hurlet Limestone and its overlying shales. Silvermine Quarry, Linlithgowshire 460

170. Junction of amygdaloidal basalt with shales and limestone, shore, half a mile east from Kinghorn, Fife 464

171. Columnar basalt, Pettycur, Kinghorn, Fife 469

172. Section across the Fife band of Sills 473

173. Section across the upper volcanic band of north Ayrshire. Length about four miles 474

174. Section showing the connection of the two volcanic bands in Liddesdale 476

175. Diagram to show the position of a mass of Upper Old Red Sandstone which has fallen into the great vent near Tudhope Hill, east of Mosspaul 476

MAPS

I. General map of the Volcanic districts of the British Isles--_At the end of the volume_

II. Map of the Cambrian and Silurian volcanic region of North Wales _To face p. 256_

III. Map of the Old Red Sandstone volcanic region of "Lake Caledonia" in Central Scotland and North Ireland _To face p. 334_

IV. Map of the Carboniferous volcanic districts of Scotland _To face p. 476_