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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
This fully revised and updated edition introduces the reader to sedimentology and stratigraphic principles, and provides tools for the interpretation of sediments and sedimentary rocks. The processes of formation, transport and deposition of sediment are considered and then applied to develop conceptual models for the full range of sedimentary environments, from deserts to deep seas and reefs to rivers.
Different approaches to using stratigraphic principles to date and correlate strata are also considered, in order to provide a comprehensive introduction to all aspects of sedimentology and stratigraphy. The text and figures are designed to be accessible to anyone completely new to the subject, and all of the illustrative material is provided in an accompanying CD-ROM. High-resolution versions of these images can also be downloaded from the companion website for this book at:
www.wiley.com/go/nicholssedimentology.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 1071
Veröffentlichungsjahr: 2013
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Table of Contents
Cover
Title
Copyright
Preface
Acknowledgements
1 Introduction: Sedimentology and Stratigraphy
1.1 SEDIMENTARY PROCESSES
1.2 SEDIMENTARY ENVIRONMENTS AND FACIES
1.3 THE SPECTRUM OF ENVIRONMENTS AND FACIES
1.4 STRATIGRAPHY
1.5 THE STRUCTURE OF THIS BOOK
FURTHER READING
2 Terrigenous Clastic Sediments: Gravel, Sand and Mud
2.1 CLASSIFICATION OF SEDIMENTS AND SEDIMENTARY ROCKS
2.2 GRAVEL AND CONGLOMERATE
2.3 SAND AND SANDSTONE
2.4 CLAY, SILT AND MUDROCK
2.5 TEXTURES AND ANALYSIS OF TERRIGENOUS CLASTIC SEDIMENTARY ROCKS
2.6 TERRIGENOUS CLASTIC SEDIMENTS: SUMMARY
FURTHER READING
3 Biogenic, Chemical and Volcanogenic Sediments
3.1 LIMESTONE
3.2 EVAPORITE MINERALS
3.3 CHERTS
3.4 SEDIMENTARY PHOSPHATES
3.5 SEDIMENTARY IRONSTONE
3.6 CARBONACEOUS (ORGANIC) DEPOSITS
3.7 VOLCANICLASTIC SEDIMENTARY ROCKS
FURTHER READING
4 Processes of Transport and Sedimentary Structures
4.1 TRANSPORT MEDIA
4.2 THE BEHAVIOUR OF FLUIDS AND PARTICLES IN FLUIDS
4.3 FLOWS, SEDIMENT AND BEDFORMS
4.4 WAVES
4.5 MASS FLOWS
4.6 MUDCRACKS
4.7 EROSIONAL SEDIMENTARY STRUCTURES
4.8 TERMINOLOGY FOR SEDIMENTARY STRUCTURES AND BEDS
4.9 SEDIMENTARY STRUCTURES AND SEDIMENTARY ENVIRONMENTS
FURTHER READING
5 Field Sedimentology, Facies and Environments
5.1 FIELD SEDIMENTOLOGY
5.2 GRAPHIC SEDIMENTARY LOGS
5.3 PALAEOCURRENTS
5.4 COLLECTION OF ROCK SAMPLES
5.5 DESCRIPTION OF CORE
5.6 INTERPRETING PAST DEPOSITIONAL ENVIRONMENTS
5.7 RECONSTRUCTING PALAEOENVIRONMENTS IN SPACE AND TIME
5.8 SUMMARY: FACIES AND ENVIRONMENTS
FURTHER READING
6 Continents: Sources of Sediment
6.1 FROM SOURCE OF SEDIMENT TO FORMATION OF STRATA
6.2 MOUNTAIN-BUILDING PROCESSES
6.3 GLOBAL CLIMATE
6.4 WEATHERING PROCESSES
6.5 EROSION AND TRANSPORT
6.6 DENUDATION AND LANDSCAPE EVOLUTION
6.7 TECTONICS AND DENUDATION
6.8 MEASURING RATES OF DENUDATION
6.9 DENUDATION AND SEDIMENT SUPPLY: SUMMARY
FURTHER READING
7 Glacial Environments
7.1 DISTRIBUTION OF GLACIAL ENVIRONMENTS
7.2 GLACIAL ICE
7.3 GLACIERS
7.4 CONTINENTAL GLACIAL DEPOSITION
7.5 MARINE GLACIAL ENVIRONMENTS
7.6 DISTRIBUTION OF GLACIAL DEPOSITS
7.7 ICE, CLIMATE AND TECTONICS
7.8 SUMMARY OF GLACIAL ENVIRONMENTS
FURTHER READING
8 Aeolian Environments
8.1 AEOLIAN TRANSPORT
8.2 DESERTS AND ERGS
8.3 CHARACTERISTICS OF WIND-BLOWN PARTICLES
8.4 AEOLIAN BEDFORMS
8.5 DESERT ENVIRONMENTS
8.6 AEOLIAN DEPOSITS OUTSIDE DESERTS
8.7 SUMMARY
FURTHER READING
9 Rivers and Alluvial Fans
9.1 FLUVIAL AND ALLUVIAL SYSTEMS
9.2 RIVER FORMS
9.3 FLOODPLAIN DEPOSITION
9.4 PATTERNS IN FLUVIAL DEPOSITS
9.5 ALLUVIAL FANS
9.6 FOSSILS IN FLUVIAL AND ALLUVIAL ENVIRONMENTS
9.7 SOILS AND PALAEOSOLS
9.8 FLUVIAL AND ALLUVIAL FAN DEPOSITION: SUMMARY
FURTHER READING
10 Lakes
10.1 LAKES AND LACUSTRINE ENVIRONMENTS
10.2 FRESHWATER LAKES
10.3 SALINE LAKES
10.4 EPHEMERAL LAKES
10.5 CONTROLS ON LACUSTRINE DEPOSITION
10.6 LIFE IN LAKES AND FOSSILS IN LACUSTRINE DEPOSITS
10.7 RECOGNITION OF LACUSTRINE FACIES
FURTHER READING
11 The Marine Realm: Morphology and Processes
11.1 DIVISIONS OF THE MARINE REALM
11.2 TIDES
11.3 WAVE AND STORM PROCESSES
11.4 THERMO-HALINE AND GEOSTROPHIC CURRENTS
11.5 CHEMICAL AND BIOCHEMICAL SEDIMENTATION IN OCEANS
11.6 MARINE FOSSILS
11.7 TRACE FOSSILS
11.8 MARINE ENVIRONMENTS: SUMMARY
FURTHER READING
12 Deltas
12.1 RIVER MOUTHS, DELTAS AND ESTUARIES
12.2 TYPES OF DELTA
12.3 DELTA ENVIRONMENTS AND SUCCESSIONS
12.4 VARIATIONS IN DELTA MORPHOLOGY AND FACIES
12.5 DELTAIC CYCLES AND STRATIGRAPHY
12.6 SYNDEPOSITIONAL DEFORMATION IN DELTAS
12.7 RECOGNITION OF DELTAIC DEPOSITS
FURTHER READING
13 Clastic Coasts and Estuaries
13.1 COASTS
13.2 BEACHES
13.3 BARRIER AND LAGOON SYSTEMS
13.4 TIDES AND COASTAL SYSTEMS
13.5 COASTAL SUCCESSIONS
13.6 ESTUARIES
13.7 FOSSILS IN COASTAL AND ESTUARINE ENVIRONMENTS
FURTHER READING
14 Shallow Sandy Seas
14.1 SHALLOW MARINE ENVIRONMENTS OF TERRIGENOUS CLASTIC DEPOSITION
14.2 STORM-DOMINATED SHALLOW CLASTIC SEAS
14.3 TIDE-DOMINATED CLASTIC SHALLOW SEAS
14.4 RESPONSES TO CHANGE IN SEA LEVEL
14.5 CRITERIA FOR THE RECOGNITION OF SANDY SHALLOW-MARINE SEDIMENTS
FURTHER READING
15 Shallow Marine Carbonate and Evaporite Environments
15.1 CARBONATE AND EVAPORITE DEPOSITIONAL ENVIRONMENTS
15.2 COASTAL CARBONATE AND EVAPORITE ENVIRONMENTS
15.3 SHALLOW MARINE CARBONATE ENVIRONMENTS
15.4 TYPES OF CARBONATE PLATFORM
15.5 MARINE EVAPORITES
15.6 MIXED CARBONATE–CLASTIC ENVIRONMENTS
FURTHER READING
16 Deep Marine Environments
16.1 OCEAN BASINS
16.2 SUBMARINE FANS
16.3 SLOPE APRONS
16.4 CONTOURITES
16.5 OCEANIC SEDIMENTS
16.6 FOSSILS IN DEEP OCEAN SEDIMENTS
16.7 RECOGNITION OF DEEP OCEAN DEPOSITS: SUMMARY
FURTHER READING
17 Volcanic Rocks and Sediments
17.1 VOLCANIC ROCKS AND SEDIMENT
17.2 TRANSPORT AND DEPOSITION OF VOLCANICLASTIC MATERIAL
17.3 ERUPTION STYLES
17.4 FACIES ASSOCIATIONS IN VOLCANIC SUCCESSIONS
17.5 VOLCANIC MATERIAL IN OTHER ENVIRONMENTS
17.6 VOLCANIC ROCKS IN EARTH HISTORY
17.7 RECOGNITION OF VOLCANIC DEPOSITS: SUMMARY
FURTHER READING
18 Post-depositional Structures and Diagenesis
18.1 POST-DEPOSITIONAL MODIFICATION OF SEDIMENTARY LAYERS
18.2 DIAGENETIC PROCESSES
18.3 CLASTIC DIAGENESIS
18.4 CARBONATE DIAGENESIS
18.5 POST-DEPOSITIONAL CHANGES TO EVAPORITES
18.6 DIAGENESIS OF VOLCANICLASTIC SEDIMENTS
18.7 FORMATION OF COAL, OIL AND GAS
FURTHER READING
19 Stratigraphy: Concepts and Lithostratigraphy
19.1 GEOLOGICAL TIME
19.2 STRATIGRAPHIC UNITS
19.3 LITHOSTRATIGRAPHY
19.4 APPLICATIONS OF LITHOSTRATIGRAPHY
FURTHER READING
20 Biostratigraphy
20.1 FOSSILS AND STRATIGRAPHY
20.2 CLASSIFICATION OF ORGANISMS
20.3 EVOLUTIONARY TRENDS
20.4 BIOZONES AND ZONE FOSSILS
20.5 TAXA USED IN BIOSTRATIGRAPHY
20.6 BIOSTRATIGRAPHIC CORRELATION
20.7 BIOSTRATIGRAPHY IN RELATION TO OTHER STRATIGRAPHIC TECHNIQUES
FURTHER READING
21 Dating and Correlation Techniques
21.1 DATING AND CORRELATION TECHNIQUES
21.2 RADIOMETRIC DATING
21.3 OTHER ISOTOPIC AND CHEMICAL TECHNIQUES
21.4 MAGNETOSTRATIGRAPHY
21.5 DATING IN THE QUATERNARY
FURTHER READING
22 Subsurface Stratigraphy and Sedimentology
22.1 INTRODUCTION TO SUBSURFACE STRATIGRAPHY AND SEDIMENTOLOGY
22.2 SEISMIC REFLECTION DATA
22.3 BOREHOLE STRATIGRAPHY AND SEDIMENTOLOGY
22.4 GEOPHYSICAL LOGGING
22.5 SUBSURFACE FACIES AND BASIN ANALYSIS
FURTHER READING
23 Sequence Stratigraphy and Sea-level Changes
23.1 SEA-LEVEL CHANGES AND SEDIMENTATION
23.2 DEPOSITIONAL SEQUENCES AND SYSTEMS TRACTS
23.3 PARASEQUENCES: COMPONENTS OF SYSTEMS TRACTS
23.4 CARBONATE SEQUENCE STRATIGRAPHY
23.5 SEQUENCE STRATIGRAPHY IN NON-MARINE BASINS
23.6 ALTERNATIVE SCHEMES IN SEQUENCE STRATIGRAPHY
23.7 APPLICATIONS OF SEQUENCE STRATIGRAPHY
23.8 CAUSES OF SEA-LEVEL FLUCTUATIONS
23.9 SEQUENCE STRATIGRAPHY: SUMMARY
FURTHER READING
24 Sedimentary Basins
24.1 CONTROLS ON SEDIMENT ACCUMULATION
24.2 BASINS RELATED TO LITHOSPHERIC EXTENSION
24.3 BASINS RELATED TO SUBDUCTION
24.4 BASINS RELATED TO CRUSTAL LOADING
24.5 BASINS RELATED TO STRIKE-SLIP TECTONICS
24.6 COMPLEX AND HYBRID BASINS
24.7 THE RECORD OF TECTONICS IN STRATIGRAPHY
24.8 SEDIMENTARY BASIN ANALYSIS
24.9 THE SEDIMENTARY RECORD
FURTHER READING
References
Index
End User License Agreement
Guide
Cover
Table of Contents
Begin Reading
List of Illustrations
1 Introduction: Sedimentology and Stratigraphy
Fig. 1.1 A modern depositional environment: a sandy river channel and vegetated floodplain.
Fig. 1.2 Sedimentary rocks interpreted as the deposits of a river channel (the lens of sandstones in the centre right of the view) scoured into mudstone deposited on a floodplain (the darker, thinly bedded strata below and to the side of the sandstone lens).
2 Terrigenous Clastic Sediments: Gravel, Sand and Mud
Fig. 2.1 A classification scheme for sediments and sedimentary rocks.
Fig. 2.2 The Udden–Wentworth grain-size scale for clastic sediments: the clast diameter in millimetres is used to define the different sizes on the scale, and the phi values are –log
2
of the grain diameter.
Fig. 2.3 A conglomerate composed of well-rounded pebbles.
Fig. 2.4 A conglomerate (or breccia) made up of angular clasts.
Fig. 2.5 Nomenclature used for mixtures of gravel, sand and mud in sediments and sedimentary rock.
Fig. 2.6 A clast-supported conglomerate: the pebbles are all in contact with each other.
Fig. 2.7 A matrix-supported conglomerate: each pebble is surrounded by matrix.
Fig. 2.8 The shape of clasts can be considered in terms of four end members, equant, rod, disc and blade. Equant and disc-shaped clasts are most common.
Fig. 2.9 A conglomerate bed showing imbrication of clasts due to deposition in a current flowing from left to right.
Fig. 2.10 The relationship between imbrication and flow direction as clasts settle in a stable orientation.
Fig. 2.11 The Pettijohn classification of sandstones, often referred to as a ‘Toblerone plot’ (Pettijohn 1975).
Fig. 2.12 A photomicrograph of a sandstone: the grains are all quartz but appear different shades of grey under crossed polars due to different orientations of the grains.
Fig. 2.13 The optical properties of the minerals most commonly found in sedimentary rocks.
Fig. 2.14 The crystal lattice structure of some of the more common clay minerals.
Fig. 2.15 Graphic illustration of sorting in clastic sediments. The sorting of a sediment can be determined precisely by granulometric analysis, but a visual estimate is more commonly carried out.
Fig. 2.16 Roundness and sphericity estimate comparison chart (from Pettijohn et al. 1987).
Fig. 2.17 Histogram, frequency distribution and cumulative frequency curves of grain size distribution data. Note that the grain size decreases from left to right.
Fig. 2.18 Flow diagram of the determination of the textural maturity of a terrigenous clastic sediment or sedimentary rock.
3 Biogenic, Chemical and Volcanogenic Sediments
Fig. 3.1 Types of bioclast commonly found in limestones and other sedimentary rocks.
Fig. 3.2 Bioclastic debris on a beach consisting of the hard calcareous parts of a variety of organisms.
Fig. 3.3 Fossil gastropod shells in a limestone.
Fig. 3.4 Mounds of cyanobacteria form stromatolites, which are bulbous masses of calcium carbonate material at various scales: (top) modern stromatolites; (bottom) a cross-section through ancient stromatolites.
Fig. 3.5 Non-biogenic fragments that occur in limestones.
Fig. 3.6 The Dunham classification of carbonate sedimentary rocks (Dunham 1962) with modifications by Embry & Klovan (1971). This scheme is the most commonly used for description of limestones in the field and in hand specimen.
Fig. 3.7 The calcareous hard parts of organisms may be made up of aragonite, calcite in either its low-or high-magnesium forms, or mixtures of minerals.
Fig. 3.8 The proportions of the principal ions in seawater of normal salinity and ‘average’ river water. (Data from Krauskopf 1979).
Fig. 3.9 The proportions of minerals precipitated by the evaporation of seawater of average composition.
Fig. 3.10 White halite precipitated on the shores of the Dead Sea, Jordan, which has a higher concentration of ions than normal seawater.
Fig. 3.11 Thinly bedded banded iron formation (BIF) composed of alternating layers of iron-rich and silica-rich rock.
Fig. 3.12 (a) The classification of volcaniclastic sediments and sedimentary rocks based on the grain size of the material. (b) Nomenclature used for loose ash and consolidated tuff with different proportions of lithic, vitric and crystal components.
4 Processes of Transport and Sedimentary Structures
Fig. 4.1 Laminar and turbulent flow of fluids through a tube.
Fig. 4.2 Particles move in a flow by rolling and saltating (bedload) and in suspension (suspended load).
Fig. 4.3 Flow of a fluid through a tapered tube results in an increase in velocity at the narrow end where a pressure drop results.
Fig. 4.4 The lift force resulting from the Bernoulli effect causes grains to be moved up from the base of the flow.
Fig. 4.5 The Hjülstrom diagram shows the relationship between the velocity of a water flow and the transport of loose grains. Once a grain has settled it requires more energy to start it moving than a grain that is already in motion. The cohesive properties of clay particles mean that fine-grained sediments require relatively high velocities to re-erode them once they are deposited, especially once they are compacted. (From Press & Siever 1986.)
Fig. 4.6 Normal and reverse grading within individual beds and fining-up and coarsening-up patterns in a series of beds.
Fig. 4.7 Layers within a flow and flow surface roughness: the viscous sublayer, the boundary layer within the flow and the flow depth.
Fig. 4.8 Flow over a bedform: imaginary streamlines within the flow illustrate the separation of the flow at the brink of the bedform and the attachment point where the streamline meets the bed surface, where there is increased turbulence and erosion. A separation eddy may form in the lee of the bedform and produce a minor counter-current (reverse) flow.
Fig. 4.9 Current ripple cross-lamination in fine sandstone: the ripples migrated from right to left. The coin is 20mm in diameter.
Fig. 4.10 Migrating straight crested ripples form planar cross-lamination. Sinuous or isolated (linguoid or lunate) ripples produce trough cross-lamination. (From Tucker 1991.)
Fig. 4.11 In plan view current ripples may have straight, sinuous or isolated crests.
Fig. 4.12 Climbing ripples: in the lower part of the figure, more of the stoss side of the ripple is preserved, resulting in a steeper ‘angle of climb’.
Fig. 4.13 Dune bedforms in an estuary: the most recent flow was from left to right and the upstream side of the dunes is covered with current ripples.
Fig. 4.14 Graphs of subaqueous ripple and subaqueous dune bedform wavelengths and heights showing the absence of overlap between ripple and dune-scale bedforms. (From Collinson et al. 2006.)
Fig. 4.15 Migrating straight crested dune bedforms form planar cross-bedding. Sinuous or isolated (linguoid or lunate) dune bedforms produce trough cross-bedding. (From Tucker 1991.)
Fig. 4.16 Subaqueous dune bedforms in a braided river.
Fig. 4.17 The patterns of cross-beds are determined by the shape of the bedforms resulting from different flow conditions.
Fig. 4.18 Planar tabular cross-stratification with tangential bases to the cross-beds (the scale bar is in inches and is 100mm long).
Fig. 4.19 Horizontal lamination in sandstone beds.
Fig. 4.20 A bedform stability diagram which shows how the type of bedform that is stable varies with both the grain size of the sediment and the velocity of the flow.
Fig. 4.21 The formation of wave ripples in sediment is produced by oscillatory motion in the water column due to wave ripples on the surface of the water. Note that there is no overall lateral movement of the water, or of the sediment. In deep water the internal friction reduces the oscillation and wave ripples do not form in the sediment.
Fig. 4.22 Forms of wave ripple: rolling grain ripples produced when the oscillatory motion is capable only of moving the grains on the bed surface and vortex ripples are formed by higher energy waves relative to the grain size of the sediment.
Fig. 4.23 Wave ripples in sand seen in plan view: note the symmetrical form, straight crests and bifurcating crest lines.
Fig. 4.24 Internal stratification in wave ripples showing cross-lamination in opposite directions within the same layer. The wavelength may vary from a few centimetres to tens of centimetres.
Fig. 4.25 Wave ripple cross-lamination in sandstone (pen is 18 cm long).
Fig. 4.26 A muddy debris flow in a desert wadi.
Fig. 4.27 A debris-flow deposit is characteristically poorly sorted, matrix-supported conglomerate.
Fig. 4.28 A turbidity current is a turbulent mixture of sediment and water that deposits a graded bed – a turbidite.
Fig. 4.29 The ‘Bouma sequence’ in a turbidite deposit.
Fig. 4.30 Proximal to distal changes in the deposits formed by turbidity currents. The lower, coarser parts of the Bouma sequence are only deposited in the more proximal regions where the flow also has a greater tendency to scour into the underlying beds.
Fig. 4.31 A high-density turbidite deposited from a flow with a high proportion of entrained sediment.
Fig. 4.32 Mudcracks caused by subaerial desiccation of mud.
Fig. 4.33 Syneresis cracks in mudrock, believed to be formed by subaqueous shrinkage.
Fig. 4.34 Sole marks found on the bottoms of beds: flute marks and obstacle scours are formed by flow turbulence; groove and bounce marks are formed by objects transported at the base of the flow.
Fig. 4.35 Bed thickness terminology.
Fig. 4.36 Terminology used for sets and co-sets of cross-stratification.
Fig. 4.37 Lenticular, wavy and flaser bedding in deposits that are mixtures of sand and mud.
5 Field Sedimentology, Facies and Environments
Fig. 5.1 An example of a graphic sedimentary log: this form of presentation is widely used to summarise features in successions of sediments and sedimentary rocks.
Fig. 5.2 Examples of patterns and symbols used on graphic sedimentary logs.
Fig. 5.3 A proforma sheet for constructing graphic sedimentary logs.
Fig. 5.4 An example of an annotated sketch illustrating sedimentary features observed in the field.
Fig. 5.5 A field photograph of sedimentary rocks: an irregular lower surface of the thick sandstone unit in the upper part of the cliff marks the base of a river channel.
Fig. 5.6 The true direction of dip of planes (e.g. planar cross-beds) cannot be determined from a single vertical face (faces A or B): a true dip can be calculated from two different apparent dip measurements or measured directly from the horizontal surface (T).
Fig. 5.7 Trough cross-bedding seen in plan view: flow is interpreted as being away from the camera.
Fig. 5.8 A rose diagram is used to graphically summarise directional data such as palaeocurrent information: the example on the right shows data indicating a flow to the south west.
Fig. 5.9 Directions measured from palaeoflow can be considered in terms of ‘x’ and ‘y’ co-ordinates: see text for discussion.
Fig. 5.10 Some of the heavy minerals that can be used as provenance indicators.
Fig. 5.11 When drilling through strata it is possible to recover cylinders of rock that are cut vertically to reveal the details of the beds.
Fig. 5.12 A graphic sedimentary log with facies information added. The names for facies are usually descriptive. Facies codes are most useful where they are an abbreviation of the facies description. The use of columns for each facies allows for trends and patterns in facies and associations to be readily recognised.
Fig. 5.13 A summary of the principal sedimentary environments.
6 Continents: Sources of Sediment
Fig. 6.1 The pathway of processes involved in the formation of a succession of clastic sedimentary rocks, part of the rock cycle.
Fig. 6.2 The boundaries of the present-day principal tectonic plates.
Fig. 6.3 The present-day world climate belts.
Fig. 6.4 The principal weathering processes and their controls.
Fig. 6.5 Frost shattering of a boulder (50 cm across) in a polar climate setting.
Fig. 6.6 The relative stability of common silicate minerals under chemical weathering.
Fig. 6.7 An in
situ
soil profile with a division into different horizons according to presence of organic matter and degree of breakdown of the regolith.
Fig. 6.8 Mechanisms of gravity-driven transport on slopes. Rock falls and slides do not necessarily include water, whereas slumps, debris flows and turbidity currents all include water to increasing degrees.
Fig. 6.9 A scree slope or talus cone in a mountain area with strong physical weathering.
Fig. 6.10 Erosion by solution in beds of limestone results in a karst landscape.
Fig. 6.11 Badlands scenery formed by the erosion of weak mudrock beds.
Fig. 6.12 The development of land plants through time: grasses, which are very effective at binding soil and stabilising the land surface, did not become widespread until the mid-Cenozoic.
Fig. 6.13 Uplift due to thickening of the crust followed by erosion results in isostatic compensation as the load of the rock mass eroded is removed. If the erosion is uneven then locally the removal of mass from valleys can result in uplift of the mountain peaks between.
Fig. 6.14 The rain shadow effect in mountain belts: moisture in air blown from the sea falls as rain as the air mass cools over a mountain range.
7 Glacial Environments
Fig. 7.1 Snowfall adds to the mass of a glacier in the accumulation zone and as the glacier advances downslope it enters the ablation zone where mass is lost due to ice melting. Glacial advance or retreat is governed by the balance between these two processes.
Fig. 7.2 Hills and ridges of bare rock (known as nunataks) surrounded by glaciers and ice sheets in a high-latitude polar glacial area.
Fig. 7.3 Floating ice, including icebergs, is formed by calving of ice from a glacier.
Fig. 7.4 The thermal regimes of glaciers are determined by the climatic setting: glaciers frozen to bedrock tend to occur in polar regions, while temperate glaciers occur in mountains in lower latitudes.
Fig. 7.5 A valley glacier in a temperate mountain region partially covered by a carapace of detritus.
Fig. 7.6 Till deposits result from the accumulation of debris above, below and in front of a glacier.
Fig. 7.7 Glacial landforms and glacial deposits in continental glaciated areas.
Fig. 7.8 Graphic sedimentary log illustrating some of the deposits of continental glaciers.
Fig. 7.9 A lateral moraine left by the retreat of a valley glacier.
Fig. 7.10 A dark ridge of material within a valley glacier that will form a medial moraine when the ice retreats (viewed from the air).
Fig. 7.11 In periglacial areas, freeze–thaw processes in the surface of the permafrost form polygonal patterns.
Fig. 7.12 At continental margins in polar areas, continental ice feeds floating ice sheets that eventually melt releasing detritus to form a till sheet and calve to form icebergs, which may carry and deposit dropstones.
Fig. 7.13 An ice shelf at the edge of a continental glaciated area.
Fig. 7.14 Glaciomarine deposits are typically laminated mudrocks with sparse coarser debris derived from icebergs.
8 Aeolian Environments
Fig. 8.1 The distribution of high- and low-pressure belts at different latitudes creates wind patterns that are deflected by the Coriolis force.
Fig. 8.2 Pebbles in a stony desert with a shiny desert varnish of iron and manganese oxides.
Fig. 8.3 Aeolian ripples, dunes and draas are three distinct types of aeolian bedform.
Fig. 8.4 Aeolian ripples form by sand grains saltating: finer grains are winnowed from the crests creating a slight inverse grading between the trough and the crest of the ripple that may be preserved in laminae.
Fig. 8.5 Aeolian ripples in modern desert sands: the pen is 18 cm long.
Fig. 8.6 Aeolian dunes migrate as sand blown up the stoss (upwind) side is either blown off the crest to fall as grainfall on the lee side or moves by grain flow down the lee slope.
Fig. 8.7 Aeolian ripples superimposed on an aeolian dune.
Fig. 8.8 Grain flow on the lee slope of an aeolian dune.
Fig. 8.9 Four of the main aeolian dune types, their forms determined by the direction of the prevailing wind(s) and the availability of sand. The small ‘rose diagrams’ indicate the likely distribution of palaeowind indicators if the dunes resulted in cross-bedded sandstone.
Fig. 8.10 Sand supply and the variability of prevailing wind directions control the types of dunes formed.
Fig. 8.11 Aeolian dune cross-bedding in sands deposited in a desert: the view is approximately 5m high.
Fig. 8.12 Depositional environments in arid regions: coarse material is deposited on alluvial fans, sand accumulates to form aeolian dunes and occasional rainfall feeds ephemeral lakes where mud and evaporite minerals are deposited.
Fig. 8.13 Graphic sedimentary log of the arid-zone environments shown in Fig. 8.12.
Fig. 8.14 The preservation of aeolian dune deposits is influenced by the level of the groundwater table: if the water table is high the interdune areas are wet and the sand is not reworked by the wind.
Fig. 8.15 The global distribution of modern deserts: most lie within 40° of the Equator.
Fig. 8.16 During glacial periods the regions of polar high pressure are larger, creating stronger pressure gradients and hence stronger winds. In the absence of large high pressure areas at the poles in interglacial periods the pressure gradients are weaker and winds are consequently less strong.
9 Rivers and Alluvial Fans
Fig. 9.1 The geomorphological zones in alluvial and fluvial systems: in general braided rivers tend to occur in more proximal areas and meandering rivers occur further downstream.
Fig. 9.2 A sandy river channel and adjacent overbank area: the river is at low-flow stage exposing areas of sand deposited in the channel.
Fig. 9.3 Several types of river can be distinguished, based on whether the river channel is straight or sinuous (meandering), has one or multiple channels (anastomosing), and has in-channel bars (braided). Combinations of these forms can often occur.
Fig. 9.4 Main morphological features of a braided river. Deposition of sand and/or gravel occurs on mid-channel bars.
Fig. 9.5 Mid-channel gravel bars in a braided river.
Fig. 9.6 A schematic graphic sedimentary log of braided river deposits.
Fig. 9.7 Sandy dune bedforms on a mid-channel bar in a braided river.
Fig. 9.8 This large braided river has moved laterally from right to left.
Fig. 9.9 Depositional architecture of a braided river: lateral migration of the channel and the abandonment of bars leads to the build-up of channel-fill successions.
Fig. 9.10 Flow in a river follows the sinuous thalweg resulting in erosion of the bank in places.
Fig. 9.11 Main morphological features of a meandering river. Deposition occurs on the point bar on the inner side of a bend while erosion occurs on the opposite cut bank. Levees form when flood waters rapidly deposit sediment close to the bank and crevasse splays are created when the levee is breached.
Fig. 9.12 The point bars on the inside bends of this meandering river have been exposed during a period of low flow in the channel.
Fig. 9.13 A schematic graphic sedimentary log of meandering river deposits.
Fig. 9.14 A pale band across the inside of this meander bend marks the path of a chute channel that cuts across the point bar.
Fig. 9.15 Depositional architecture of a meandering river: sandstone bodies formed by the lateral migration of the river channel remain isolated when the channel avulses or is cut-off to form an oxbow lake.
Fig. 9.16 A channel is commonly not filled with sand: in this case the form of a channel is picked out by steep banks on either side, but the fill of the channel is mainly mud.
Fig. 9.17 The architecture of fluvial deposits is determined by the rates of subsidence and frequency of avulsion.
Fig. 9.18 Alluvial fans in the Death Valley, USA, a region with a hot, arid climate.
Fig. 9.19 A colluvial fan, a mixture of scree and debris flows in a cold, relatively dry setting in the Arctic.
Fig. 9.20 Types of alluvial fan: debris-flow dominated, sheetflood and stream-channel types – mixtures of these processes can occur on a single fan.
Fig. 9.21 Schematic sedimentary logs through debris-flow, sheetflood and stream-channel alluvial fan deposits.
Fig. 9.22 A debris flow on an alluvial fan: the conglomerate is poorly sorted, with the larger clasts completely surrounded by a matrix of finer sediment.
Fig. 9.23 Sheetflood deposits on an alluvial fan showing well-developed stratification.
Fig. 9.24 Twelve major soil types recognised by the US Soil Survey.
Fig. 9.25 A calcrete forms by precipitation of calcium carbonate within a soil in an arid or semi-arid environment.
10 Lakes
Fig. 10.1 Hydrological regimes of lakes.
Fig. 10.2 A lake basin supplied by a river in the foreground, with outflow through a sill to the sea in the distance.
Fig. 10.3 The thermal stratification of fresh lake waters results in a more oxic, upper layer, the epilimnion, and a colder, anoxic lower layer, the hypolimnion. Sedimentation in the lake is controlled by this density stratification above and below the thermocline.
Fig. 10.4 Facies distribution in a freshwater lake with dominantly clastic deposition.
Fig. 10.5 A schematic graphic sedimentary log through clastic deposits in a freshwater lake.
Fig. 10.6 Facies distributions in a freshwater lake with carbonate deposition.
Fig. 10.7 A saline lake, Mono Lake, California: the mineral deposit mounds are associated with underground spring waters.
Fig. 10.8 Three general types of saline lake can be distinguished on the basis of their chemistry.
Fig. 10.9 A salt crust of minerals formed by evaporation in an ephemeral lake.
Fig. 10.10 When an ephemeral lake receives an influx of water and sediment, mud is deposited from suspension to form a thin bed that is overlain by evaporite minerals as the water evaporates. Repetitions of this process create a series of couplets of mudstone and evaporite.
11 The Marine Realm: Morphology and Processes
Fig. 11.1 A cross-section from the continental shelf through the continental slope and rise down to the abyssal plain.
Fig. 11.2 Depth-related divisions of the marine realm: (a) broad divisions are defined by water depth; (b) the shelf is described in terms of the depth to which different processes interact with the sea floor, and the actual depths vary according to the characteristics of the shelf.
Fig. 11.3 The gravitational force of the Sun and Moon act on the Earth and on anything on the surface, including the water masses in oceans.
Fig. 11.4 The North Sea of northwest Europe has a variable tidal range along different parts of the bordering coasts. Amphidromic points mark the centres of cells of rotary tides that affect the shallow sea.
Fig. 11.5 During the diurnal tidal cycle the direction of flow reverses from ebb (offshore) to flood (onshore). The current velocity also varies from peaks at the mid points of ebb and flood flow, reducing to zero at high and low tide slack water before accelerating again.
Fig. 11.6 Features that indicate tidal influence of transport and deposition: (a) herringbone cross-stratification; (b) mud drapes on cross-bedding formed during the slack water stages of tidal cycles; (c) reactivation surfaces formed by erosion of part of a bedform when a current is reversed.
Fig. 11.7 Herringbone cross-stratification in sandstone beds (width of view 1.5 m).
Fig. 11.8 Cross-bedded sandstone in sets 35 cm thick with the surfaces of individual cross-beds picked out by thin layers of mud. Mud drapes on cross-beds are interpreted as forming during slack water stages in the tidal cycle.
Fig. 11.9 A reactivation surface within cross-bedded sands is a minor erosion surface truncating some of the cross-beds.
Fig. 11.10 The main geostrophic current pathways (thermo-haline circulation patterns) affecting the modern oceans. Sink points in the North Atlantic are due to input of cold glacial meltwater from the Greenland ice-cap.
Fig. 11.11 Classification of trace fossils based on interpretation of the activity of the organism. (Adapted from Seilacher 2007.)
Fig. 11.12 Assemblages of trace fossil forms and their relationship to the major divisions of the marine realm. (Adapted from Pemberton et al. 1992.) The assemblages are named after characteristic ichnofauna and the ‘type’ ichnofossil does not need to be present in the assemblage.
Fig. 11.13 The characteristics of trace fossils are influenced by the nature of the substrate. Boring organisms cut sharp-sided traces into solid rock or cemented sea floors (hardgrounds). Semiconsolidated surfaces (firmgrounds) result in well-defined burrows.
Fig. 11.14 Examples of common trace fossils: (a) bird footprint; (b) bivalve borings into rock; (c) vertical burrows in sandstone (
Skolithos
); (d) large crustacean burrow (
Ophiomorpha
); (e) complex burrows (
Thalassanoides
); (f)
Zoophycos
; (g)
Palaeodictyon
; (h)
Helmenthoides
.
12 Deltas
Fig. 12.1 A delta fed by a river prograding into a body of water.
Fig. 12.2 The forms of modern deltas: (a) the Nile delta, the ‘original’ delta, (b) the Mississippi delta, a river-dominated delta, (c) the Rhone delta, a wave-dominated delta, (d) the Ganges delta, a tide-dominated delta.
Fig. 12.3 Classification of deltas taking grain size, and hence sediment supply mechanisms, into account. (Modified from Orton & Reading 1993.)
Fig. 12.4 Controls on delta environments and facies. (Adapted from Elliott 1986a.)
Fig. 12.5 Delta deposition can be divided into two subenvironments, the delta top and the delta front.
Fig. 12.6 A cross-section across a delta lobe: progradation results in a coarsening-up succession.
Fig. 12.7 Differences in the grain size of the sediment supplied affect the form of a delta: (a) a high proportion of suspended load results in a relatively small mouth bar deposited from bedload and extensive delta-front and prodelta deposits; (b) a higher proportion of bedload results in a delta with a higher proportion of mouth bar gravels and sands.
Fig. 12.8 (a) A delta prograding into shallow water will spread out as the sediment is redistributed by shallow-water processes to form extensive mouth-bar and delta-front facies. (b) In deeper water the mouth bar is restricted to an area close to the river mouth and much of the sediment is deposited by mass-flow processes in deeper water.
Fig. 12.9 A schematic sedimentary log of a sandy delta prograding into shallow water.
Fig. 12.10 A schematic sedimentary log of a sandy delta prograding into a deep-water basin.
Fig. 12.11 A modern Gilbert-type coarse-grained delta.
Fig. 12.12 Gilbert-type deltas are coarse-grained deltas that prograde into deep water. They display a distinctive pattern of steeply-dipping foreset beds sandwiched between horizontal topset and bottomset strata.
Fig. 12.13 A schematic sedimentary log of a Gilbert-type coarse-grained delta deposit.
Fig. 12.14 A Gilbert-type coarse-grained delta exposed in a cliff over 500 m high. The exposure is made up mostly of foreset deposits dipping at around 30°: horizontal topset strata form the top of the cliff and the toes of the foreset beds pass into gently dipping bottomset facies.
Fig. 12.15 A river-dominated delta with the distributary channels building out as extensive lobes due to the absence of reworking by wave and tide processes. Low-energy, interdistributary bays are a characteristic of river-dominated deltas.
Fig. 12.16 When a delta channel avulses a new lobe starts to build out at the new location of the channel mouth. The abandoned lobe subsides by dewatering until completely submerged. Through time the channel will eventually switch back to a position overlapping the former delta lobe. This results in a series of delta-lobe successions, each coarsening-up.
Fig. 12.17 A schematic graphic sedimentary log of riverdominated delta deposits.
Fig. 12.18 A wave-dominated delta formed where wave activity reworks the sediment brought to the delta front to form coastal sand bars and extensive mouth-bar deposits.
Fig. 12.19 Sand bars at the mouth of a wavedominated delta.
Fig. 12.20 A schematic graphic sedimentary log of wavedominated delta deposits.
Fig. 12.21 A tide-dominated delta in a macrotidal regime will show extensive reworking of the delta front by tidal currents and the delta top will have a region of intertidal deposition.
Fig. 12.22 A schematic graphic sedimentary log of tidedominated delta deposits.
Fig. 12.23 Delta cycles: the facies succession preserved depends on the location of the vertical profile relative to the depositional lobe of a delta.
13 Clastic Coasts and Estuaries
Fig. 13.1 Reflective coasts are usually erosional with steep beaches and a narrow surf zone. Dissipative coasts may be depositional, with sand deposited on a gently sloping foreshore.
Fig. 13.2 An erosional coastline: wave action has eroded the cliff and left a wave-cut platform of eroded rock on the beach.
Fig. 13.3 Morphological features of a beach comprising a beach foreshore and backshore separated by a berm; beach dune ridges are aeolian deposits formed of sand reworked from the beach.
Fig. 13.4 Foreshore-dipping and backshore-dipping stratification in sands on a beach barrier bar.
Fig. 13.5 A beach dune ridge formed by sand blown by the wind from the shoreline onto the coast to form aeolian dunes, here stabilised by grass.
Fig. 13.6 A schematic graphic sedimentary log of sandy beach deposits.
Fig. 13.7 A wave-dominated coastline with a coastal plain bordered by a sandy beach: chenier ridges are relics of former beach strand plains.
Fig. 13.8 A wave-dominated coastline with a beach-barrier bar protecting a lagoon.
Fig. 13.9 Beach-barrier bars along a wave-dominated coastline.
Fig. 13.10 Morphological features of a coastline influenced by wave processes and tidal currents.
Fig. 13.11 A schematic graphic sedimentary log of clastic lagoon deposits.
Fig. 13.12 A schematic graphic sedimentary log of a transgressive coastal succession.
Fig. 13.13 Distribution of depositional settings in a wave-dominated estuary.
Fig. 13.14 A wave-dominated estuary, with an extensive beach barrier protecting a lagoonal area.
Fig. 13.15 A graphic sedimentary log of wave-dominated estuary deposits.
Fig. 13.16 Distribution of depositional settings in a tidally dominated estuary.
Fig. 13.17 A tidally dominated estuarine environment with banks of sand covered with dune bedforms exposed at low tide.
Fig. 13.18 A graphic sedimentary log of tidal estuary deposits.
14 Shallow Sandy Seas
Fig. 14.1 Characteristics of a storm-dominated shelf environment.
Fig. 14.2 Hummocky–swaley cross-stratification, a sedimentary structure that is thought to be characteristic of storm conditions on a shelf.
Fig. 14.3 An example of hummocky cross-stratified sandstone with very well-defined, undulating laminae. The bed is 30cm thick.
Fig. 14.4 A bed deposited by storm processes. The base (bottom of the photograph) of the bed has a sharp erosional contact with underlying mudrocks. Planar lamination is overlain by hummocky cross-stratification and capped by wave-rippled sandstone and mudstone (just below the adhesive tape roll, 8 cm across).
Fig. 14.5 A schematic graphic sedimentary log of a storm-dominated succession.
Fig. 14.6 The strata in the hillside are a succession passing up from offshore mudstones (bottom left), to thin-bedded sandstone of the offshore transition zone up to the cliff-forming shoreface sandstones.
Fig. 14.7 Sandwaves, sand ridges and sand ribbons in shallow, tidally influenced shelves and epicontinental seas.
Fig. 14.8 Large-scale cross-stratification formed by the migration of sandwaves in a tidally influenced shelf environment.
Fig. 14.9 Bioturbated, cross-bedded sandstones deposited on a tidally influenced shelf.
Fig. 14.10 A schematic sedimentary log through a tidally influenced shelf succession.
15 Shallow Marine Carbonate and Evaporite Environments
Fig. 15.1 The relationship between water depth and biogenic carbonate productivity, which is greatest in the photic zone.
Fig. 15.2 The types of carbonate platform in shallow marine environments.
Fig. 15.3 Different groups of organisms have been important producers of carbonate sedimentary material through the Phanerozoic; limestones of different ages therefore tend to have different biogenic components.
Fig. 15.4 Morphological features of a carbonate coastal environment with a barrier protecting a lagoon.
Fig. 15.5 A carbonate-dominated coast with a barrier island in an arid climatic setting: evaporation in the protected lagoon results in increased salinity and the precipitation of evaporite minerals in the lagoon.
Fig. 15.6 In arid coastal settings a sabkha environment may develop. Evaporation in the supratidal zone results in saline water being drawn up through the coastal sediments and the precipitation of evaporite minerals within and on the sediment surface.
Fig. 15.7 Tide-influenced coastal carbonate environments.
Fig. 15.8 Modern coral atolls.
Fig. 15.9 Modern corals in a fringing reef. The hard parts of the coral and other organisms form a boundstone deposit.
Fig. 15.10 The type and abundance of carbonate reefs has varied through the Phanerozoic (data from Tucker, 1992).
Fig. 15.11 The core of a Devonian reef flanked by steeply dipping forereef deposits on the right-hand side of the exposure.
Fig. 15.12 Facies distribution in a reef complex.
Fig. 15.13 Reefs can be recognised as occurring in three settings: (a) barrier reefs form offshore on the shelf and protect a lagoon behind them, (b) fringing reefs build at the coastline and (c) patch reefs or atolls are found isolated offshore, for instance on a seamount.
Fig. 15.14 Cliffs of Cretaceous Chalk.
Fig. 15.15 Generalised facies distributions on carbonate platforms: (a) ramps, (b) non-rimmed shelves and (c) rimmed shelves.
Fig. 15.16 Schematic graphic log of a carbonate ramp succession.
Fig. 15.17 Schematic graphic log of a non-rimmed carbonate shelf succession.
Fig. 15.18 Schematic graphic log of a rimmed carbonate shelf succession.
Fig. 15.19 Settings where barred basins can result in thick successions of evaporites.
Fig. 15.20 (a) A barred basin, ‘bulls-eye’ pattern model of evaporite deposition; (b) a barred basin ‘teardrop’ pattern model of evaporite deposition.
16 Deep Marine Environments
Fig. 16.1 Deep water environments are floored by ocean crust and are the most widespread areas of deposition worldwide.
Fig. 16.2 Depositional environments on a submarine fan.
Fig. 16.3 The proportions of different architectural elements on submarine fans are determined by the dominant grain size deposited on the fan.
Fig. 16.4 Thick sandstone beds deposited in a channel in the proximal part of a submarine fan complex.
Fig. 16.5 Schematic graphic sedimentary logs through submarine fan deposits: proximal, mid-fan lobe deposits and lower fan deposits.
Fig. 16.6 A succession of sandy and muddy turbidite beds deposited on the distal part of a submarine fan complex.
Fig. 16.7 Facies model for a gravel-rich submarine fan: typically found in front of coarse fan deltas, the fan is small and consists mainly of debris flows.
Fig. 16.8 Facies model for a sand-rich submarine fan: sand-rich turbidites form lobes of sediment that build out on the basin floor, with switching of the locus of deposition occurring through time.
Fig. 16.9 Facies model for a mixed sand–mud submarine fan: the lobes are a mixture of sand and mud and build further out as the turbidites travel longer distances.
Fig. 16.10 Facies model for a muddy submarine fan: lobes are very elongate and most of the sand is deposited close to the channels.
Fig. 16.11 Slope apron deposits include pelagic sediment, slumps, debris flows and sands from the shelf edge. (From Stow 1986.)
Fig. 16.12 Schematic graphic sedimentary log through contourite deposits.
Fig. 16.13 Thin-bedded cherts deposited in a deep marine environment.
Fig. 16.14 The distribution of pelagic sediment in the oceans is strongly influenced by the effects of depth-related pressure on the solubility of carbonate minerals. Below the calcite compensation depth particles of the mineral dissolve resulting in concentrations of silica, which is less soluble, and clay minerals.
17 Volcanic Rocks and Sediments
Fig. 17.1 The ropy surface texture of a pahoehoe lava.
Fig. 17.2 Beds of volcaniclastic sediments: the lower layers are coarse lapillistones while the upper beds are finer ash forming tuff beds.
Fig. 17.3 Distribution of ash over topography from pyroclastic falls, pyroclastic flows and pyroclastic surges.
Fig. 17.4 Sketch graphic sedimentary logs of pyroclastic fall, flow and surge deposits.
Fig. 17.5 Pelée, Merapi and St Vincent types of pyroclastic flow.
Fig. 17.6 A small ash cone formed by a pyroclastic eruption.
18 Post-depositional Structures and Diagenesis
Fig. 18.1 Instabilities within the beds result in parts of the succession slumping to form deformed masses of material: slump scars are the surfaces on which movement occurs.
Fig. 18.2 The layers of strata at different angles are a result of slumps rotating the strata.
Fig. 18.3 Faulting during sedimentation results in the formation of a growth fault: the layers to the right thickening towards the fault are evidence of movement on the fault during deposition.
Fig. 18.4 Convolute lamination and convolute bedding form as a result of local liquefaction of deposits.
Fig. 18.5 Convolute lamination in thinly bedded sandstone and mudstone formed as a result of slumping.
Fig. 18.6 Overturned cross-stratification in sandstone beds 60 cm thick: these would have been originally deposited as simple cross-beds by the migration of a subaqueous dune bedform and subsequently the upper part of the cross-bed set was deformed by the shear stress of a flow over the top.
Fig. 18.7 Movement of fluid up from lower layers results in the formation of dewatering structures.
Fig. 18.8 Movement of fluid up from lower layers incorporates sand that reaches the sediment surface to form a sand volcano.
Fig. 18.9 Load casts and ball and pillow structures form where denser sediment, typically sand, is deposited on top of soft mud.
Fig. 18.10 Diapiric structures form where low-density material such as salt or water-saturated mud is overlain by denser sediments.
Fig. 18.11 Depth and temperature ranges of diagenetic processes.
Fig. 18.12 Changes to the packing of spheres can lead to a reduction in porosity and an overall reduction in volume.
Fig. 18.13 Differential compaction between sandstone and mudstone results in draping of layers around a sandstone lens.
Fig. 18.14 Compaction of layers within a mudrock around a concretion.
Fig. 18.15 Pressure solution has occurred at the contact between two limestone pebbles.
Fig. 18.16 Types of grain contact: there is generally a progressive amount of compaction from point, to long contacts (involving a re-orientation of grains), to concavoconvex and to sutured contacts (which both involve a degree of pressure dissolution.
Fig. 18.17 Cement fabrics: (a) overgrowths formed by precipitation of the same mineral (such as quartz or calcite) are in optical continuity with the grain; (b) a poikilotopic fabric is the result of cement minerals completely enveloping grains; (c) an isopachous cement grows on all surfaces within pores, a pattern commonly seen in sparry calcite cements; (d) a meniscus fabric forms when cement precipitation occurs from water flowing down through the sediment.
Fig. 18.18 An isopachous, sparry calcite cement formed in the pore spaces between pebbles lines the surfaces of the pebbles.
Fig. 18.19 Flow-chart of the pathways of diagenesis of organic matter in sediments.
Fig. 18.20 Stylolites are surfaces of pressure dissolution, in this case marked by an irregular band of insoluble residue in a limestone.
Fig. 18.21 Four of the models proposed for the processes of dolomitisation. (From Tucker & Wright 1990.)
Fig. 18.22 Dissolution of evaporite minerals within a stratigraphic succession results in the formation of a breccia due to collapse of the beds.
Fig. 18.23 Peat-forming environments: waterlogged areas where organic material can accumulate may either be regions of stagnant water (ombotrophic mires or bogs) or places where there is a through-flow of fresh or saline water (rheotrophic mires or marshes).
Fig. 18.24 The formation of coal from peat involves a considerable amount of compaction, initially converting peat into brown coal (lignite) before forming bituminous coal.
Fig. 18.25 With increased burial the maturation of kerogen results in the formation initially of oil and later gas: greater heating results in the complete breakdown of the hydrocarbons.
Fig. 18.26 Cartoon of the relationships between the source rock, migration pathway, reservoir, trap and cap rocks required for the accumulation of oil and gas in the subsurface.
19 Stratigraphy: Concepts and Lithostratigraphy
Fig. 19.1 Nomenclature used for geochronological and chronostratigraphic units.
Fig. 19.2 A stratigraphic chart with the ages of the different divisions of geological time. (Data from Gradstein et al. 2004.)
Fig. 19.3 Principles of superposition: (a) a ‘layer-cake’ stratigraphy; (b) stratigraphic relations around a reef or similar feature with a depositional topography.
Fig. 19.4 Gaps in the record are represented by unconformities: (a) angular unconformities occur when older rocks have been deformed and eroded prior to later deposition above the unconformity surface; (b) disconformities represent breaks in sedimentation that may be associated with erosion but without deformation.
Fig. 19.5 An angular unconformity between horizontal sandstone beds above and steeply dipping shaly beds below.
Fig. 19.6 Stratigraphic relationships can be simple indicators of the relative ages of rocks: (a) cross-cutting relations show that the igneous features are younger than the sedimentary strata around them; (b) a fragment of an older rock in younger strata provides evidence of relative ages, even if they are some distance apart.
Fig. 19.7 Way-up indicators in sedimentary rocks.
Fig. 19.8 Relationships between the boundaries of lithostratigraphic units (defined by lithological characteristics resulting from the depositional environment) and time-lines in a succession of strata formed during gradual sea-level rise (transgression).
20 Biostratigraphy
Fig. 20.1 The Linnaean hierarchical system for the taxonomy of organisms.
Fig. 20.2 Major groups of organisms preserved as macrofossils in the stratigraphic record and their age ranges.
Fig. 20.3 Zonation schemes used in biostratigraphic correlation. (Adapted from North American Commission on Stratigraphic Nomenclature 1983.)
Fig. 20.4 Shelly fossils in a limestone bed.
Fig. 20.5 Graphical correlation methods are used to identify changes in rates of sedimentation or a hiatus in deposition. (Adapted from Shaw 1964.)
21 Dating and Correlation Techniques
Fig. 21.1 Radioactive decay results in the formation of a new ‘daughter’ isotope from the ‘parent’ isotope.
Fig. 21.2 The main decay series used in radiometric dating of rocks: the K–Ar, Rb–Sr and U–Pb systems are the ones most commonly used –
14
C dating is mainly used for dating archaeological materials.
Fig. 21.3 The strontium isotope curve: these changes in the ratio of the isotopes
86
Sr and
87
Sr through geological time can be used to determine the age of some rocks, but the same ratio can occur at different ages. (Data from Faure 1986.)
Fig. 21.4 Reversals in the polarity of the Earth’s magnetic field through part of the Cenozoic. (From Haq et al. 1988.)
Fig. 21.5 An illustration of how different successions can be correlated using a combination of magnetic reversals, marker beds and biostratigraphic data.
22 Subsurface Stratigraphy and Sedimentology
Fig. 22.1 In marine seismic reflection surveys the ship tows the energy source, the airgun, and the receivers either as a single line or in multiple lines to generate a 3-D survey.
Fig. 22.2 Example of a seismic reflection profile: the horizontal scale is distance (in this case several kilometres across), but the vertical scale is in two-way travel time, that is, the time it takes for sound waves to reach a subsurface reflector and return to the surface. If the acoustic properties of the rock are known (these vary with the bulk density) this can be converted to depth.
Fig. 22.3 Reflector patterns and reflector relationships on seismic reflection profiles.
Fig. 22.4 Cores cut by a drill bit and brought to the surface provide information about subsurface strata.
Fig. 22.5 Geophysical instruments are normally mounted on a sonde that passes through formations on the end of a wireline.
Fig. 22.6 (a) Determination of lithology using information provided by a gamma-ray logging tool. (b) Determination of lithology and porosity using information provided by a sonic logging tool. (From Rider 2002.)
Fig. 22.7 Wireline logging traces produced by geophysical logging tools.
Fig. 22.8 Trends in gamma-ray traces can be interpreted in terms of depositional environment provided that there is sufficient corroborative evidence from cuttings and cores. (From Cant 1992.)
23 Sequence Stratigraphy and Sea-level Changes
Fig. 23.1 Relative sea-level change (the change in water depth at a point) may be due to uplift or subsidence of the crust, increase or decrease in the amount of water, or addition of sediment to the sea floor. It is often not possible to determine which mechanism is responsible if there is information from only one place.
Fig. 23.2 (a) If sea level rises faster than sediment is supplied the coastline shifts landward: this is known as transgression and the pattern in the sediments is retrogradational. (b) If sediment is supplied to a coast where there is no (or relatively slow) sea-level rise the coastline moves seaward: this is regression and the sediment pattern is progradational. (c) Sea-level fall results in a forced regression and the sediment pattern is retogradational, and may include erosion surfaces. (d) A situation where the coastline stays in the same position for long periods of time is relatively unusual and requires a balance between relative sea-level rise and sediment supply producing a pattern of aggradation in the sediments.
Fig. 23.3 The various possible patterns of sedimentation that can result from different relative amounts of sediment supply and relative sea-level change are summarised in this diagram. The responses to the different combinations are expressed in terms of vertical sedimentary successions, as seen in successions of strata in outcrop or boreholes, or as geometries seen in regional cross-sections or seismic reflection profiles expressed in terms of shoreline trajectories. Eight main scenarios (I–VIII) are recognised.
Fig. 23.4 A sinusoidal curve of sea-level variation combined with a long-term increase in relative sea-level results in periods when there is relative sea-level rise (and hence transgression) and periods of relative sea-level fall (resulting in regression).
Fig. 23.5 Two main types of continental margin are recognised, each resulting in different stratigraphic patterns when there are sea-level fluctuations: (a) shelf-break margins have a shallow shelf area bordered by a steeper slope down to the deeper basin floor; (b) ramp margins do not have a distinct change in slope at a shelf edge.
Fig. 23.6 Variations in sea level that follow the pattern in Fig. 23.4 affecting a shelf-break margin result in a series of systems tracts formed at different stages: the lowstand is characterised by deep-basin turbidites if the sea level falls to the shelf edge.
Fig. 23.7 Variations in sea level that follow the pattern in Fig. 23.4 affecting a ramp margin result in a series of systems tracts formed at different stages: during lowstand the deposition is shifted down the ramp.
Fig. 23.8 A higher frequency sea-level fluctuation curve superimposed on the curve in Fig. 23.4 produces a pattern of short-term rises and falls in sea level within the general trends of transgression and regression. These short-term fluctuations result in creation of small amounts of accommodation being created, even during the falling stage.
Fig. 23.9 A schematic graphic sedimentary log of a parasequence in an inner shelf shallow-marine setting.
Fig. 23.10 A schematic graphic sedimentary log of a parasequence in an offshore shelf shallow-marine setting.
Fig. 23.11 The stacking patterns of parasequences to form parasequence sets are characteristic of different systems tracts.
Fig. 23.12 A falling-stage systems tract (FSST) on a ramp margin can show different patterns of deposition: if the sea level falls relatively slowly with respect to sediment supply deposition forms a continuous succession across the ramp as an attached FSST; relatively fast sea-level fall results in a detached FSST.
Fig. 23.13 The responses of a carbonate rimmed shelf to changes in sea level. An important difference with clastic systems tracts is that the carbonate productivity varies because most carbonate material is biogenic and forms in shallow water. During high-stand and transgressive systems tracts wide areas of shallow water allow more sediment to be formed, whereas at falling stage and lowstand production of carbonate sediment is much lower.
Fig. 23.14 A summary of the stratal geometries and the patterns within systems tracts in a depositional sequence.
Fig. 23.15 Schematic sedimentary log through an idealised depositional sequence: in practice, the succession seen in outcrop or in the subsurface will often include only parts of this whole pattern, with considerable variations in thicknesses of the systems tracts. (a) Lower part of the succession. (b) Continuation into the upper part of the succession.
Fig. 23.16 Interpretation of gamma-ray logs in terms of parasequences and systems tracts.
Fig. 23.17 A hypothetical example of correlation between logs in different parts of the coastal and marine environments using sequence stratigraphic principles. Note that correlation is on the basis that in different places on the shelf and in the basin there will be different facies deposited at the same time.
Fig. 23.18 There are a number of possible causes of sea-level change related to tectonic and climatic factors; the approximate magnitudes of change and the rates at which it will occur are indicated in each case.
Fig. 23.19 First-, second- and third- order sea-level cycles are considered to be global signatures due to tectonic and climatic controls outlined in Fig. 23.18. (Modified from Vail et al. 1977.)
Fig. 23.20 Milankovitch cycles: the eccentricity of the Earth’s orbit of the Sun, changes on the obliquity of the axis of rotation of the Earth and the precession of the axis of rotation may result in global climatic cycles on the scale of tens of thousands of years.
24 Sedimentary Basins
Fig. 24.1 The facies of deposits in sedimentary basins and their distributions in three dimensions are controlled by climatic and tectonic factors, the nature of the hinterland bedrock and the connection with the oceans.
Fig. 24.2 Rift basins form by extension in continental crust: sediment is supplied from the rift flanks or may also be brought in by rivers flowing along the axis of the rift.
Fig. 24.3 Rift valleys are characterised by steep sides formed by the extensional faults that form the basin (East African Rift Valley).
Fig. 24.4 Intracratonic basins are broad regions of subsidence within continental crust: they are typically broad and shallow basins.
Fig. 24.5 With continued extension in a rift, the lithosphere thins and oceanic crust starts to form in a proto-oceanic trough where sedimentation occurs in a marine setting.
Fig. 24.6 An ocean basin is flanked by thinned continental crust, which subsides to form passive margins to the ocean basin.
Fig. 24.7 An arc–trench system forms where oceanic crust is subducted at an ocean trench and the downgoing plate releases magma at depth, which rises to form a volcanic arc. Sediment may accumulate in the trench, in the forearc basin between the trench and the arc and in the region behind the arc called a backarc basin if there is subsidence due to extension (see also retroarc basins, Fig. 24.13).
Fig. 24.8 Arc–trench systems include chains of volcanoes that form the arc.
Fig. 24.9 Forearc basins, trenches and extensional backarc basins are supplied by volcaniclastic material from the adjacent arc and may also receive continentally derived detritus if the overriding plate is continental crust.
Fig. 24.10 Sediment deposited in an ocean trench includes both material derived from the overriding plate and pelagic material. As subduction proceeds sediment is scraped off the downgoing plate to form an accretionary prism of deformed sedimentary material.
Fig. 24.11 The major mountainous areas of the world occur in areas of plate collision where an orogenic belt forms.
Fig. 24.12 Collision between two continental plates results in the formation of an orogenic belt where there is thickening of the crust: this results in an additional load being placed on the crust either side and causes a downward flexure of the crust to form peripheral foreland basins.
Fig. 24.13 The thickness of the crust increases due to emplacement of magma in a volcanic arc at a continental margin, resulting in flexure of the crust behind the arc to form a retroarc foreland basin.
Fig. 24.14 Basins may form by a variety of mechanisms in strike-slip settings: (a) a releasing bend, (b) a fault termination, (c) a fault offset (usually referred to as a pull-apart basin) and (d) at a junction between faults. Note that if the relative motion of the faults were reversed in each case the result would be uplift instead of subsidence.
Fig. 24.15 The Wilson Cycle of extension to form a rift basin and ocean basin followed by basin closure and formation of an orogenic belt. (Adapted from Wilson 1966.)
Fig. 24.16 Basin analysis techniques.
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