Landforms and Geology of Granite Terrains

ISBN-13: 9780415364355 / Angielski / Twarda / 2005 / 354 str.

J. R. Vidal Romani

Opis

A detailed analysis and explanation of granite landforms, this text focuses on granitic terrains and their structures, forms and surfaces.

Spis treści

Table of Contents; Preface and acknowledgements; 1 Characteristics and foundations1.1 Typical landforms and landscapes1.2 Previous work1.3 Occurrences of granite1.4 Granite – definition and composition 1.5 Physical characteristics 1.6 Orthogonal fracture systems 1.7 Fractures and drainage patterns 2 Sheet fractures and structures2.1 Terminology2.2 Description and characteristics 2.3 Theories of origin 2.3.1 Exogenetic explanations 2.3.2 Endogenetic explanations 2.4 Summary 3 Weathering 3.1 Definition and significance 3.2 Physical disintegration 3.3 Chemical alteration 3.4 The course of weathering in granite 3.5 Controls of weathering 4 Plains – the expected granite form 4.1 Weathering and surfaces of low relief 4.2 Plains of epigene (subaerial) origin 4.2.1 Rolling or undulating plains 4.2.2 Pediments 4.2.3 Relationship between pediment and peneplain 4.3 Etch plains in granite 4.4 Very flat plains 4.5 Multicyclic and stepped assemblages 4.6 Exhumed plains 4.7 Summary 5 Boulders as examples of two-stage forms5.1 The two-stage or etching mechanism 5.2 Boulders – morphology and occurrences 5.3 Subsurface exploitation of orthogonal fracture systems 5.4 Tectonic and structural forms 5.5 Types of peripheral or marginal weathering 5.6 Causes of peripheral weathering 5.7 Evacuation of grus 5.8 Boulders of epigene origin 5.9 Summary 6 Inselbergs and bornhardts 6.1 Definitions and terminology 6.2 Bornhardt characteristics 6.3 Theories of origin 6.3.1 Environment 6.3.2 The scarp retreat hypothesis 6.3.3 Tectonics and structure: faulting and lithology 6.3.4 Variations in fracture density 6.3.5 Differential subsurface weathering and the two-stage concept 6.4 Evidence and argument concerning origins of bornhardts6.4.1 Contrasts in weathering between hill and plain 6.4.2 Incipient domes 6.4.3 Subsurface initiation of minor forms 6.4.4 Flared slopes and stepped inselbergs 6.4.5 Regional and local patterns in plan 6.4.6 Coexistence of forms associated with compression/shearing 6.4.7 Topographic settings 6.4.8 Occurrence in multicyclic landscapes 6.4.9 Fracture-defined margins 6.4.10 Age of inselbergs and bornhardts 6.5 Exhumed bornhardts and inselbergs 6.6 Antiquity and inselberg landscapes 6.7 Summary Other granitic residuals and uplands 7.1 Isolated residuals7.1.1 Nubbins7.1.2 Castle koppies7.1.3 Large conical forms or medas7.1.4 Towers and acuminate forms7.2 Massifs7.3 Regions of all slopes topography 7.4 Discussion 8 Minor forms developed on steep slopes 8.1 Flared slopes 8.1.1 Description and characteristics 8.1.2 Origin 8.1.3 Changes after exposure 8.2 Fretted basal slopes and other variants8.3 Scarp-foot weathering and erosion, and the piedmont angle8.4 Rock platforms 8.4.1 Description 8.4.2 Origin 8.5 Scarp-foot depressions 8.5.1 Description 8.5.2 Origin 8.6 Flutings or grooves 8.6.1 Description 8.6.2 Origin 8.6.3 Surface or subsurface initiation? 8.6.4 Inversion 9 Minor forms developed on gentle slopes 9.1 Rock basins 9.1.1 Description 9.1.2 Nomenclature 9.1.3 Origin 9.1.4 Differentiation of major types 9.1.5 Evacuation of debris 9.1.6 Rate of development 9.2 Plinths and associated blocks and boulders 9.2.1 Description 9.2.2 Origin 9.3 Pedestal rocks 9.3.1 Terminology 9.3.2 Origin 9.4 Gutters or runnels 9.4.1 Terminology 9.4.2 Description 9.4.3 Origin 9.5 Rock levees 9.6 Rock doughnuts 9.6.1 Description 9.6.2 Origin 9.6.3 Evidence and argument 9.7 Fonts 10 Caves and tafoni 10.1 General statement 10.2 Caves associated with corestones and grus 10.3 Caves associated with fractures 10.4 Tafoni 10.4.1 Description 10.4.2 Process 10.4.3 Stages of development 10.4.4 Case-hardening and other veneers10.5 Speleothems 11 Split and cracked blocks and slabs 11.1 Split rocks 11.1.1 Description 11.1.2 Origin 11.2 Parted and dislodged blocks 11.3 Dislocated slabs 11.3.1 A-tents 11.3.2 Overlapping slabs 11.3.3 Displaced slabs 11.3.4 Chaos 11.3.5 Wedges 11.3.6 Origin of the forms 11.3.7 Relationship of A-tents and pressure ridges 11.4 Polygonal cracking 11.4.1 Description11.4.2 Previous interpretations 11.4.3 Evidence11.4.4 Explanations 11.5 Tesselated pavements 12 Zonality, azonality and the coastal context 12.1 Introduction 12.2 Lithological zonality and azonality 12.3 Climatic zonality and azonality 12.4 The coastal context 13 Retrospect and prospect Author Index; Location Index;Subject Index.

O autorze

Charles Rowland Twidale is presently a Visiting Fellow of the University of Adelaide, South Australia, and Honorary Professor of the University Institute of Geology "Isidro Parga Pondal" of the University of Coruña.

Juan Ramón Vidal Romaní is specialized in the interpretation of the origin of granitic forms in relation to their geodynamic environment. He is a Professor in Geodynamics at the University of Coruña and Director of the University Institute of Geology, "Isidro Parga Pondal".