c h r i s t o p h e r r i l e y

c h r i s t o p h e r r i l e y

p h d r e s e a r c h

The Morphotectonics

of the Spanish Sierra Nevada.

a study using digital elevation modelling.

Christopher David Belfield Riley

April 1995

Submitted for the degree of Doctor of Philosophy

Imperial College, University of London.

Acknowledgements

Without the financial support of Conoco Plc. through Professor Richard Selley, none of this research would have been possible. For the faith, tolerance and patience of John McMahoan Moore I am most grateful, and to Dr. Joseph Cartwright I am equally indebted.

The staff of University College London, Photogrammetry and Geography Departments made it possible for me to make the DEMs, and to them I am also grateful; particularly; Helen Marshall, David Alison, James Pearson, Kevin Morris, Tony Cook and David Haydock who was tragically killed in January 1992.

During the course of the research I sought advice and help from a number of people. I would particularly like to thank Professor Claudio Vita-Finzi at UCL for his unending enthusiasm, encouragement and inspiration, Dr. Iain Stewart, (West London College) Drs. Carlos Sanz de Galdeano, Jesus Galdívar and Mario Chico-Olma, (University of Granada) Professor Denys Brunsden, (Kings College, London) Professor Douglas Shearman and Dr. John Cosgrove, (Imperial College, London).

The trials and tribulations though of day-to-day research are always shared most closely with family and friends without whom, I would have given up a long time ago. Particularly I am most grateful to Stephanie Riley, Encarnacion Vives, Stephane Vial, John Bradley, Andrew Williams, Jackie Houghton, Steve Bennett, Duncan Copp, Paul Seaman, Stephen Grant, Ronan Dowling and Robyn Dummer for advice, criticism, loyalty and patient friendships.

The seeds of discovery and wonder at the science of geology were first planted in me by my late father Andrew Riley. Alistair Wells encouraged me later and his continuing energy and enthusiasm for communicating the Earth Sciences is still an inspiration to me. The ideas and thoughts in this thesis owe their origins to both of them.

Finally during the long days locked away from geology in London, writing this thesis and pondering the implications of my observations I have looked to geomorphology in the glaciated peaks of Snowdonia, the coastal cliffs of Cornwall and Romania's remote Carpathian mountains for inspiration. There are undoubtedly parts of these places contained unseen within the following pages. I make no apologies for their influence on my thoughts

To my first science teacher

Andrew John Riley.

"When one looks south from Granada across the red towers of the Alhambra one sees a range of mountains known as the Sierra Nevada which have snow on them all the year round....But forget the Alhambra, forget the nightingales, and consider only the mountains. They are high enough to boast having small glaciers, and if you cross them you will come to a broad, hollow country, very broken and separated from the sea by a coastal range. It is this country , which until quite recently could only be explored on foot or mule-back, that is the subject of this book".

Gerald Brenan, "South from Granada", 1957.

Contents.

Chapter One - Introduction.

1.1 Introduction.......................................................................................... 2

1.2 Regional Geology and Tectonic Setting............................................. 6

1.3 Sierra Nevada...................................................................................... 12

1.3.1 The Nevado-Filábride Complex........................................................ 13

1.3.2 The Ballabona-Cucharón Complex................................................ 13

1.3.3 The Alpujárride Complex............................................................... 14

1.3.4 The Maláguide Complex................................................................ 15

1.4 The Intermontane Basins........................................................................ 16

1.4.1 Neogene Stratigraphy.........................................................................16

1.4.2 The Granada Basin.............................................................................18

1.4.3 The Guadix Basin............................................................................... 25

1.4.4 The Alpujárride Corridor - Ugiyar & Orgiva Basins..........................31

1.4.5 The Sorbas-Tabernas Basin.................................................................35

1.5 Tectonic History........................................................................................39

1.5.1 Palaeozoic - Triassic............................................................................ 40

1.5.2 Cretaceous - Tertiary...........................................................................40

1.5.3 Early Miocene, (Aquitanian - Burdigalian).............................................41

1.5.4 Middle Miocene, (Langhian - Serravallian)............................................43

1.5.5 Late Miocene, (Serravallian - Tortonian).............................................. 45

1.5.6 Messinian.............................................................................................47

1.5.7 Pliocene - Quaternary - Pleistocene -Holocene......................................47

1.6 Uplift history of the Sierra Nevada..............................................................54

1.7 Summary of tectonics relating to the geomorphology of the Sierra Nevada..57

1.8 Thesis Themes and Research Objectives.....................................................59

Download PDF of Chapter 1



Chapter Two - Digital Elevation Modelling	63
2.1 Introduction.......................................................................................	64
2.2 Data Souces and Capture ................................................................	67
2.1.1 Topographic Maps..............................................................	67
2.1.2 Metric Camera Photography..............................................	67

2.3 Generating a DEM..........................................................................	69
2.3.1 Digitising contours.............................................................	69
2.3.2 Creating a triangulation DEM...........................................	70
2.3.3 Stereo Matching.................................................................	73
2.4 DEM visualisations..........................................................................	78
2.5 Data Limitations...............................................................................	87
2.6 Software Limitations.........................................................................	89
2.7 Errors in DEMs.................................................................................	90
2.8 Calibration of DEMs.........................................................................	92
2.9 Summary............................................................................................	99
Chapter Three - Palaeoseismic Activity	101
3.1 Introduction........................................................................................	102
3.2 Data Sources......................................................................................	103
3.3 Data Processing.................................................................................	114
3.4 Discussion..........................................................................................	116
3.4.1 Time distribution..................................................................	116
3.4.2 Magnitude - Frequency Distribution....................................	122
3.4.3 Depth Distribution................................................................	125
3.4.4 Spatial Distribution...............................................................	128
3.4.5 Seismotectonic Interpretation...............................................	133
3.5 Summary & Conclusions.....................................................................	139
Chapter Four - A Field Study of the
Mountain Front Fault Segment Geomorphology.	141
4.1 Introduction..........................................................................................	142
4.2 Segmentation of the mountain fronts..................................................	146
4.3 The Sierra Nevada Mountain Front Segments....................................	153
4.3.1 Tectonic Activity Class 1 and 2 segments...............................	153
4.3.2 Tectonic Activity Class 3 Segments........................................	192
4.4 Discussion............................................................................................	206
4.4.1 Tectonic Regime......................................................................	206
4.4.2 Tectonic evolution...................................................................	207
4.5 Conclusions & Summary......................................................................	209

Chapter Five - Erosional Morphotectonics	212
5.1 Introduction............................................................................................	213
5.2 Fault Scarp Degradation........................................................................	215
5.2.1 Field Profiling & Morphometry...............................................	217
5.2.2 Dating Fault Scarps.................................................................	219
5.2.3 Statistical Separation of Degraded & Fresh Scarps................	224
5.2.4 Assessment of Scarp Degradation from DEM profiles............	226
5.2.5 Results......................................................................................	245
5.3 Tectonic Pediments................................................................................	230
5.3.1 Pediment Appearance on DEMs..............................................	232
5.3.2 Local Pediment Correlation.....................................................	235
5.3.3 Regional Pediment Correlation................................................	240
5.3.4 Heights of Major Pediments.....................................................	243
5.4 Hypsometric Analysis..............................................................................	251
5.4.1 Hypsometric Curves from DEMs...............................................	251
5.4.2 Results........................................................................................	252
5.5 Embayment Dimensions..........................................................................	258
5.5.1 Embayment Widths....................................................................	258
5.5.2 River Retreat Rates (R) & Time since uplift (T).........................	261
5.5.3 Pediment Ages...........................................................................	265
5.5.4 Uplift Rates................................................................................	267
5.5.5 Uplift Patterns...........................................................................	269
5.6 Ridge Morphology...................................................................................	272
5.7 Summary & Conclusions..........................................................................	275
5.8 Discussion.................................................................................................	280

Chapter Six - Tectonics and Drainage	288
6.1 Introduction...............................................................................................	289
6.1.1 General Drainage Patterns in the Study Area............................	292
6.1.2 Factors which shape drainage....................................................	295
6.2 Stream Profiles..........................................................................................	300
6.2.1 Concavity Index..........................................................................	304
6.2.2 Stream Gradient Index................................................................	309
6.3 Drainage Valley Morphology...................................................................	316
6.3.1 Valley floor to Valley Height ratio..............................................	316
6.3.2 River terraces and valley walls...................................................	324
6.4 Drainage Networks...................................................................................	327
6.4.1 Asymmetry Index.........................................................................	332
6.4.2 Bifurcation Ratio..........................................................................	332
6.4.3 Drainage Density..........................................................................	335
6.4.4 Frequency Distribution of stream lengths....................................	337
6.5 Drainage Basin Shape................................................................................	340
6.5.1 Circularity Ratio...........................................................................	344
6.5.2 Elongation Ratio...........................................................................	344
6.5.3 Relief Ratio....................................................................................	345
6.6 Drainage Crossing the Mountain front......................................................	348
6.6.1 The Wallace Ratio..........................................................................	348
6.6.2 Mountain Front Sinuosity Index....................................................	352
6.7 Palaeodrainage.............................................................................................	354
6.8 Strike-slip tectonics and drainage displacement.........................................	357
6.9 Drainage and Uplift in the Sierra Nevada...................................................	361
6.10 Summary and Conclusions..........................................................................	370
6.11 Discussion....................................................................................................	374

Chapter Seven - Tectonics and Deposition	382
7.1 Introduction....................................................................................................	383
7.1.1 Fan Measurements..........................................................................	384
7.1.2 The Study Area................................................................................	384
7.2 Qualitative observations of Fans.................................................................	395
7.2.1 Fan segmentation & entrenchment................................................	395
7.2.2 Fan descriptions.............................................................................	400
7.2.3 Climatic affects on fan development.............................................	404
7.2.4 Soil development............................................................................	409
7.3 Fan Slope......................................................................................................	410
7.3.1 The affect of tectonics...................................................................	411
7.3.2 The affect of catchment characteristics........................................	420
7.4 Fan Area.......................................................................................................	427
7.5 Fan Shape.....................................................................................................	432
7.6 Summary.......................................................................................................	438
7.7 Discussion.....................................................................................................	440

Chapter Eight - Summary and Conclusions,
Analysis of Geomorphological Data.	444
8.1 Introduction...................................................................................................	445
8.2 Summary & Conclusions..............................................................................	447
8.3 Discussion.....................................................................................................	453
8.3.1 - The Question of Climate.............................................................	453
8.3.2 - Patterns and Chronology of Uplift - geomorphological evolution	453
8.3.3 - Tectonic Activity Classes based on geomorphology...................	466
8.3.4 - Drainage Response to Tectonics.................................................	469
8.3.5 - A Mechanism for Uplift..............................................................	470
(i) Pop-up and pull apart strike slip faulting............................	472
(ii) Collision - obduction and changing 2 directions..............	474
(iii) Migrating Plutons.................................................................	477
8.4 Thesis aims and objectives answered..........................................................	482
8.5 Further Investigations..................................................................................	484
References..........................................................................................................	486
Appendix 1.	i