Landforms and Geology of Granite Terrains/

Twidale, Charles Rowland

Landforms and Geology of Granite Terrains/ - 2005.

1 Characteristics and foundations

1.1 Typical landforms and landscapes

1.2 Previous work

1.3 Occurrences of granite

1.4 Granite – definition and composition

1.5 Physical characteristics

1.6 Orthogonal fracture systems

1.7 Fractures and drainage patterns

2 Sheet fractures and structures

2.1 Terminology

2.2 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 forms

5.1 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 bornhardts

6.4.1 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 residuals

7.1.1 Nubbins

7.1.2 Castle koppies

7.1.3 Large conical forms or medas

7.1.4 Towers and acuminate forms

7.2 Massifs

7.3 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 variants

8.3 Scarp-foot weathering and erosion, and the piedmont angle

8.4 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 veneers

10.5 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 Description

11.4.2 Previous interpretations

11.4.3 Evidence

11.4.4 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



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