《the middle silurian rocks of north wales》

PART Ⅰ. GENERAL1

1. INTRODUCTION1

1.1. Distribution1

1.2. West Denbighshire1

1.3. East Denbighshire, Flintshire, etc3

1.4. Lithological changes and correlation4

1.5. Condition of deposit and rate of accumula-tion6

1.6. Geological history of the region8

1.7. Scenery13

1.8. Superficial deposits16

1.9. Economic products, water supply19

1.10. Making the map27

1.11. Problems outstanding29

2. STRATIGRAPHY30

2.1. Zone of Cyrtograptus murchisoni30

2.2. Zone of Mono-graptus riccartonensis31

2.3. Zone of C. symmetricus31

2.4. Zone of C. linnarssoni32

2.5. Zone of C. rigidus33

2.6. The Denbighshire Grits and Flags Series35

2.7. Zone of C. lundgreni37

2.8. Monograptus-dubius Beds38

2.9. Zone of M. vulgaris39

2.10. Zone of M. nilssoni39

2.11. Zone of M. scanicus48

2.12. Zone of M. tumescens53

2.13. Zone of M. leintwardinensis56

2.14. Dinas-Bran Beds57

2.15. Thicknesses of Subdivisions57

2.16. The Valentian-Salopian boundary60

2.17. The Diagnostic Value of Grapto-lite Assemblages63

3. STRUCTURE : FOLDING, FAULTING AND JOINTING66

3.1. Folding67

3.2. Faulting72

Jointing90

4. OTHER STRUCTURAL FEATURES96

4.1. Cleavage96

4.2. Intraformational and other Disturbance of Bedding109

4.3. Land-forms125

4.4. General dis-cussion of Structural Features126

4.5. The Regional Tectonic Pattern129

5. PETROGRAPHY134

5.1. Lithology and Mineralogy134

5.2. Density of the Rocks135

5.3. Texture and banding137

5.4. Chemical Com-position138

5.5. Characters as seen under the microscope138

6. PALAEONTOLOGY152

6.1. Graptolites153

6.2. Shelly faunas161

6.3. Faunas of the various zones163

7. HISTORY OF INVESTIGATION IN THE AREA166

Lists of published works171

PART Ⅱ. DETAILS OF AREAS177

8. THE DENBIGH DISTRICT178

8.1. General178

8.2. Denbigh and the Ystrad Section179

8.3. The country north-west of Denbigh,Llanefydd, Mynydd y Gaer, Moel Fodiar183

8.4. The country west and south of Denbigh, Eriviat, Tywysog, Rh?d-Galed, Groes, Moel Fechan, Foel Gasyth, Moel Prion, Moel Ytta190

8.5. Tributaries to River Clwyd between Denbigh and Pentre199

9. THE ABERGELE-LLANFAIR TALHAIARN DISTRICT (EASTERN SECTION)201

9.1. General201

9.2. Sanatorium Block203

9.3. Moelfre Isaf204

9.4. Plas-isaf Block204

9.5. Fron-fawr206

9.6. Mynydd y Gyrt and Beniar207

9.7. Pengwem208

9.8. Mynydd Bodrochwyn208

9.9. Mynydd Bodran211

9.10. Moel Iago and Cefn Treflech213

9.11. Dyffryn Aled to Mostyn Dingle215

9.12. Y Foel216

9.13. The Heskin Block216

10. THE ABERGELE-LLANFAIR TALHAIARN DISTRICT (WESTERN SECTION)219

10.1. The area west of the Llanfair faults, the Cynant Mass, Mynydd Du, Garthewin219

10.2. The area west of Garthewin, Bettws-yn-Rh?s, Moelfre Uchaf, Cae-eithin, Mynydd Glyn-Lws, Tollhouse area223

10.3. The Branar-Pentre Isaf district, Rhosmarch area, Mynydd Branar, Pentre Isaf area228

10.4. The country south of the River Elwy, the Pentre-du Block, south of Llanfair, Moel Unben, Ffrǐth Bedwyn231

10.5. Tre-pys-llygod, Moel Pentre-wern235

11. THE AREA LYING SOUTH-WEST, SOUTH AND SOUTH-EAST OF LLAN-SANNAN239

11.1. General239

11.2. The Aled Valley from Llyn Aled to Llansannan242

11.3. Tributary streams245

12. BYLCHAU AND THE CENTRAL MOORLAND AREA248

12.1. The Moorland south and south-west of Nantglyn248

12.2. The Bylchau district249

12.3. The area around the Sportsman’s Arms251

12.4. Mynydd Hiraethog, Llyn Aled to Mon Brenig, Alwen Reservoir, Afon Brenig to Pennant252

13. THE DISTRICT WEST OF LLANGERNIEW258

13.1. The Hafodunos area258

13.2. Gell to the Llyn Ty'n-y-llyn faults264

13.3. The Trofarth area266

13.4. The Wenlli fault-belt267

13.5. The district around Holland Arms269

13.6. The Llangerniew fault-system271

14. THE COUNTRY AROUND EGLWYS-FACH273

14.1. General273

14.2. The area between Bodnant and the Pentre-felin faults281

14.3. Nant Maes-Adda, Topan, Erw-g?ch and Deunant283

14.4. Llyn Syberi area286

14.5. Nant y Rhaglaw290

14.6. The Ty-mawr area293

14.7. The district south of Pentre’r Felin294

14.8. Pennant to Maenan295

15. THE COLWYN-CONWAY DISTRICT299

15.1. The Colwyn Area299

15.2. The Salopian rocks west of the Conway Valley303

15.3. The Salopian rocks north of the gap from Llandudno Junction to Mochdre309

15.4. The Glan Conway area311

16. THE LLANRWST DISTRICT314

16.1. General314

16.2. Llanrwst and the western margin324

16.3. Hendre House to Soflen326

16.4. Coed y Garth327

16.5. Area north of Melin-y-Coed328

16.6. The Llanrwst Stream section330

16.7. The Lladdoget area331

16.8. The Henblas area333

16.9. The Ll?yn-Goronwy district334

16.10. Afon Sychbant and Nant Bwlch-y-gwynt336

17. THE DISTRICT AROUND GWYTHERIN339

17.1. General339

17.2. The country south of Gwytherin342

17.3. The Pandy Tudyr area346

17.4. Farmyard to Rhwng-y-ddwyffordd, Pant-glas, Maelogen, Oerfa and Friddog347

17.5. The Cledwen Basin below Gwytherin349

17.6. The country south of Llangerniew352

18. THE COUNTRY FROM NEBO TO PENTRE VOELAS AND CERRIG-Y-DRUIDION353

18.1. The Nebo district, Moel Seisiog and Llyn Alwen353

18.2. The Country around Pentre Voelas355

18.3. The Cerrig-y-druidion Area358

19. THE RUTHIN-DERWEN AREA362

19.1. General362

19.2. The Clywedog section (Lady Bagot's Drive)364

19.3. The Ysgeibion area, Moel y Fron, Foel Ganol, Foel Uchaf, Meifod Block and Ffr?dd Fawr366

19.4. The country south and south-west of Ruthin, Llanfwrog to Efenechtyd, Pwll-glas to Nantclwyd, Clawdd-newydd to Derwen, Pool Park370

19.5. Nant Melin-d?r and south of Bont-uchel, Gyffylliog375

19.6. Clocaenog district377

19.7. Bryn Ocyn378

19.8. Clawdd-newydd to Pont Petryal380

20. THE LLANELIDAN DISTRICT382

20.1. The Llanelidan fault-system382

20.2. The country north of the main fault, the Derwen area383

20.3. The district between the main Llanelidan and Pentre faults384

20.4. The area north-west and west of Gwyddelwern386

20.5. The R?g district388

20.6. The country between Gwyddelwern and Llanelidan, Moel Truan390

20.7. The Ffynnon-Tudur area393

21. THE CLWYDIAN RANGE396

21.1. The Northern Part396

21.2. The North-central Area403

21.3. The Central Region412

21.4. The Southern End420

INDEX435