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Clastic depositional system
1. Clastic Hierarchies and Eustasy
Spring 2005
Professor Christopher G. St. C. Kendall
kendall@sc.edu
777.2410
“Clastic Hierarchies”
Christopher G. St. C. Kendall
3. Lecture Series Overview
Sequence stratigraphy & stratigraphic surfaces
Basics: Ideal ‘sequence’ of Vail et al 1977 &
associated terminology
Clastic system response to changing sea level and
rates of sedimentation - with movie
Carbonate systems response to changing sea
level and rates of sedimentation - with movie
Exercises – Sequence stratigraphy of carbonates
and clastics from chronostratigraphy, seismic,
outcrop and well log character
“Clastic Hierarchies”
Christopher G. St. C. Kendall
4. Sedimentary rocks are the
product of the generation,
transport, deposition, and
diagenesis of detritus and
solutes derived from pre-existing
rocks.
5. Sedimentary rocks are the
product of the creation, transport,
deposition, and diagenesis of
detritus and solutes derived from
pre-existing rocks.
7. Depositional Systems
depositional system: assemblage of multiple process-related
sedimentary facies assemblages, commonly identified by the
geography in which deposition occurs.
EX: nearshore depositional system, deep marine depositional system,
glacial depositional system, fluvial depositional system
NB depositional systems are:
modern features
used to interpret ancient sedimentary successions
“Clastic Hierarchies”
Christopher G. St. C. Kendall
8. Types of Depositional Systems
marine ocean, sea
transitional part land, part ocean
terrestrial land
“Clastic Hierarchies”
Christopher G. St. C. Kendall
15. Characteristics of Clastic System
Critical stratigraphic signals of
system?
Geomorphologic & tectonic setting
Dominant sedimentary processes
Facies
Subdividing surfaces
Lithology
Sedimentary structures
Geometries – Confined versus open
Fauna & flora
“Clastic Hierarchies”
Christopher G. St. C. Kendall
16. Types of Depositional Systems
marine ocean, sea
terrestrial land
transitional part land, part ocean
“Clastic Hierarchies”
Christopher G. St. C. Kendall
17. Types of Depositional Systems
marine ocean, sea
transitional part land, part ocean
terrestrial land
“Clastic Hierarchies”
Christopher G. St. C. Kendall
18. Marine Depositional Systems
shallow/nearshore
tide-dominated
wave-dominated
reef
shelf/platform
carbonate
clastic
deep marine
deep sea fans
pelagic
“Clastic Hierarchies”
Christopher G. St. C. Kendall
19. Marine Depositional Systems
wave-dominated coasts
tide-dominated coasts
fluvial-dominated coasts (deltas)
carbonate reefs
clastic shelves & platforms
carbonate shelves & platforms
deepwater fans
pelagic abyssal plains
“Clastic Hierarchies”
Christopher G. St. C. Kendall
20. Coastal Depositional Systems
Form proximal to shorelines
Geographically narrow, geologically important
Fluid flow transport and deposition
Surface waves
Tidal waves (not tsunami!)
Fluvial input
Grain-size decreases with deeper water
Onshore, offshore & longshore sediment transport
important
Net sediment input (often from rivers) often leads to
progradational geometries
Important for tracking sea-level changes
“Clastic Hierarchies”
Christopher G. St. C. Kendall
25. Marine Depositional Systems
wave-dominated coasts
tide-dominated coasts
fluvial-dominated coasts (deltas)
carbonate reefs
clastic shelves & platforms
carbonate shelves & platforms
deepwater fans
pelagic abyssal plains
“Clastic Hierarchies”
Christopher G. St. C. Kendall
26. Waves & Wave Periods
“Clastic Hierarchies”
Christopher G. St. C. Kendall
27. Characteristics of Beach Systems
Sediments coarsen upward from marine shales
Linear sand bodies parallel to basin margin, serrated margins landward
Formed by a mix of waves and tidal currents
Facies
Subdivided erosion surfaces formed during
– Dropping in base level
Local channels
– Rising in base level
Wells sorted and rounded pure quartz arenites common
Sedimentary structures
–
–
–
Offshore hummocky wavy bedding
Nearshore cut and fill
Gently seaward dipping thin parallel beds
Geometries
– Confined incised channels
– Open linear sheets parallel to shore
Fauna & flora
– Marine fauna at base of units
– Terrestrial flora at crest of units
“Clastic Hierarchies”
Christopher G. St. C. Kendall
28. Vertical stacking of shore line sediments
“Clastic Hierarchies”
Christopher G. St. C. Kendall
53. Delta Mouth Bar - Kentucky
Note Incised Surface Of Reworked Bar
“Clastic Hierarchies”
Christopher G. St. C. Kendall
54. Tidal, Storm or Tsunami Channel
Note Incised Surface Beneath Channel
“Clastic Hierarchies”
Christopher G. St. C. Kendall
55.
56. Characteristics of Sequence Boundary
(SB) from well logs, core & outcrop
Defined by erosion or incision of underlying flooding
surfaces (mfs and TS)
Inferred from interruption in the lateral continuity of
these surfaces
“Clastic Hierarchies”
Christopher G. St. C. Kendall
57. Characteristics of Sequence Boundary
(SB) from well logs, core & outcrop
Defined by erosion or incision of underlying flooding
surfaces (mfs and TS)
Inferred from interruption in the lateral continuity of
these surfaces
“Clastic Hierarchies”
Christopher G. St. C. Kendall
58. Beach Ridges: St. Phillips Island, SC
“Clastic Hierarchies”
Christopher G. St. C. Kendall
59. Progradation & Transgressive Architectures
“Clastic Hierarchies”
Christopher G. St. C. Kendall
Kraft & John, 1979
67. Characteristics of Estuary Systems
Sediments coarsen upward from marine shales
Sand bodies perpendicular to basin margin, narrow landward
Formed by a mix of tidal currents and occasional storm waves
Facies
Subdivided erosion surfaces formed during
– Dropping in base level
Local channels
– Rising in base level
Wells sorted and rounded pure quartz arenites common
Sedimentary structures
–
–
–
Offshore hummocky wavy bedding
Nearshore cut and fill
Gently seaward dipping thin parallel beds
Geometries
– Confined incised channels
– Open linear sheets perpendicular and occasionally parallel to shore
Fauna & flora
– Marine fauna at base of units
– Terrestrial flora at crest of units
“Clastic Hierarchies”
Christopher G. St. C. Kendall
71. Marine Depositional Systems
Wave-dominated coasts
Tide-dominated coasts
Fluvial-dominated coasts (deltas)
Carbonate reefs
Clastic shelves & platforms
Carbonate shelves & platforms
Deepwater fans
Pelagic abyssal plains
“Clastic Hierarchies”
Christopher G. St. C. Kendall
72. Deltaic Depositional Systems
Form where rivers with large drainages meet standing
water bodies (~basins)
Very large sediment flux
Fluid & gravity flow transport and deposition
Surface waves
Tidal waves (not tsunami!)
Fluvial input
Turbidity currents & sub-aqueous debris flows
Net sediment input often leads to progradational
geometries
Delta types depend on tidal range, wave climate, and
composition and depths of water in river and basin
“Clastic Hierarchies”
Christopher G. St. C. Kendall
73. Characteristics of Deltaic Systems
Sediments coarsen upward from marine shales
Sand bodies form tongues perpendicular to basin margin
Formed by a mix of fluvial input, tidal currents and storm waves
Facies
Subdivided erosion surfaces formed during
– Dropping in base level
Local channels
– Rising in base level
Poorly sorted and irregular litharenites common
Sedimentary structures
–
–
–
Offshore laminated to hummocky wavy bedding
Nearshore cut and fill
Gently seaward dipping thin parallel beds
Geometries
– Confined incised channels
– Open linear sheets perpendicular and occasionally parallel to shore
Fauna & flora
– Marine fauna at base of units
– Terrestrial flora at crest of units
“Clastic Hierarchies”
Christopher G. St. C. Kendall
81. Amazon Delta - Brazil
“Clastic Hierarchies”
Christopher G. St. C. Kendall
82. Nile Delta - Egypt
“Clastic Hierarchies”
Christopher G. St. C. Kendall
83. Delta Types
River-dominated
Small tidal range, weak storms and large
sediment flux build delta out into basin
Tide-dominated
Large tidal ranges dominate transport,
deposition & geomorphology
Wave-dominated
Strong and repeated storms rework delta
sediment
“Clastic Hierarchies”
Christopher G. St. C. Kendall
84. Delta Processes
Depositional patterns and geomorphology
depend on the relative dominance of three
competing processes at river mouths:
Inertia
– River water
– Basin water
Friction
– Water vs. substrate
– Water vs. water
Buoyancy
“Clastic Hierarchies”
Christopher G. St. C. Kendall
85. Delta Processes
Relative influence of inertia, friction & buoyancy is a
function of:
Density contrasts
Homopycnal flow – equal density water bodies mix
Hyperpycnal flow – higher density sinks below ocean (Yellow)
Hypopycnal flow – lower density floats on ocean (Mississippi)
Concentration, grain size and suspended vs. bedload
ratio
Water depths
Mouth
Basin
Water discharge
Water inflow velocity
“Clastic Hierarchies”
Christopher G. St. C. Kendall
86. Delta Processes
Inertia-dominated deltas
deep water, steep slopes, high river flow velocity
moderate sediment transport, large flow expansion
Friction-dominated deltas
shallow water, low slopes,
proximal sediment transport, large bars, limited flow
expansion
hyperpycnal flow possible
Buoyancy-dominated deltas
deep water, hypopycnal flow, large suspended load
distant sediment transport, flow rafting plumes
“Clastic Hierarchies”
Christopher G. St. C. Kendall
110. Types of Depositional Systems
marine ocean, sea
terrestrial land
transitional part land, part ocean
“Clastic Hierarchies”
Christopher G. St. C. Kendall
111. Marine Depositional Systems
wave-dominated coasts
tide-dominated coasts
fluvial-dominated coasts (deltas)
carbonate reefs
clastic shelves & platforms
carbonate shelves & platforms
deepwater fans
pelagic abyssal plains
“Clastic Hierarchies”
Christopher G. St. C. Kendall
114. Characteristics of Deepwater Systems
Sediments fine upward from marine fans
Sand bodies form lobes perpendicular to basin margin
Formed by a mix of fluvial input, and turbidite currents
Facies
Subdivided erosion surfaces formed during
– Migrating fan lobe fill
– Dropping in base level
Local channels
– Rising in base level
Poor to well sorted litharenites common
Sedimentary structures
– Fining upward cycles that coarsen up as depo-center of lobes migrate
– Up dip channel cut and fill
– Gently seaward dipping thin parallel lobate sheets
Geometries
– Confined incised channels
– Open lobate sheets perpendicular and occasionally parallel to shore
Fauna & flora
“Clastic Hierarchies”
Christopher G. St. C. Kendall
– Restricted Marine fauna often in over bank shales
115. Deep Sea Fan Depositional Systems
Form in the moderate to deep ocean, down-dip of
submarine canyons and often deltas
Large sediment flux, high sedimentation rate, large
area
Gravity flow transport and deposition
turbidity currents
subaqueous debris flows
suspension fall-out
Lobes and lobe-switching important
Both coarse and fine grained sediment
Often well-sorted and normally graded
“Clastic Hierarchies”
Christopher G. St. C. Kendall
116. Bengal Fan & Ganges-Brahmaputra Delta
“Clastic Hierarchies”
Christopher G. St. C. Kendall
117. Submarine Canyons and Deep Sea Fans
“Clastic Hierarchies”
Christopher G. St. C. Kendall
141. Delaware Mountains – Basin Fans
Deepwater Channel
Cha n
nel S
a n ds
“Clastic Hierarchies”
Christopher G. St. C. Kendall
Kendall Photo
142. Brushy Canyon Group - Base of Slope
Permian Basin
Channel Fill
Turbidites
“Clastic Hierarchies”
Christopher G. St. C. Kendall
Kendall Photo
143. Brushy Canyon Group - Base of Slope Permian Basin
Margin of submarine fan channel incised
into "overbank". Channel fill with
amalgamation as well as flowage & injection
of sand into the surrounding strata of the
channel walls.
Kendall Photo
“Clastic Hierarchies”
Christopher G. St. C. Kendall
U.S. Highway 62-180 south of Guadalupe Pass
144. Pelagic Depositional Systems
Form in the open ocean or open (large) lakes and seas
Small sediment flux, very low sedimentation rate
Suspended load current transport
Surface waves
Tidal waves (not tsunami!)
Fluvial input
Turbidity currents & sub-aqueous debris flows
Suspension fall-out deposition
Fine-grained (clay, mud and silt) deposition
Carbonates
Siliciclastic mudstones
“Clastic Hierarchies”
Christopher G. St. C. Kendall
158. Types of Depositional Systems
marine ocean, sea
transitional part land, part ocean
terrestrial land
“Clastic Hierarchies”
Christopher G. St. C. Kendall
161. Alluvial Fan System Characteristics
Sediments fine upward within fan lobes
Sand bodies form lobes perpendicular to basin margin
Formed by a mix of fluvial input, and mass sediment movement
Facies
Subdivided erosion surfaces formed during
– Migrating fan lobe fill
– Dropping in base level
Local channels
– Rising in base level
Poor to well sorted litharenite boulders, gravels and sands common
Sedimentary structures
– Fining upward cycles that coarsen up as depo-center of lobes progrdes
– Up dip channel cut and fill
– Gently seaward dipping thin parallel lobate sheets
Geometries
– Confined incised channels
– Open lobate sheets perpendicular and occasionally parallel to Mt front
Fauna & flora
“Clastic Hierarchies”
Christopher G. St. C. Kendall
– Terrestrial flora can be common in over bank lobes
162. Alluvial Fan Depositional Systems
Form upon exit of drainage basin from a mountain front
Mix of sediment gravity flow & fluid flow depositional
processes
Debris flows
Hyperconcentrated flows
Fluvial channels
Sheetfloods
Lobe-switching processes produce cone
Radial sediment dispersal
Decreasing grain size downslope
“Clastic Hierarchies”
Christopher G. St. C. Kendall
170. Alluvial and Fluvial Fans
‘Stream-dominated’ Alluvial Fans D = ~10 Km; S = 5-15º
‘Gravity-flow’ Alluvial Fans D = ~10 Km; S = 5-15º
Talus Cones D < 1 Km; S = 10-30º
Fluvial Megafans D = 50 -100s Km; S < 1º
“Clastic Hierarchies”
Christopher G. St. C. Kendall
180. Fluvial System Characteristics
Sediments fine upward within channel fill
Sand bodies fine distally from channels
Formed by a mix of fluvial bedload, and fine suspended sediment
Facies
Subdivided erosion surfaces formed during
– Migrating channel fill
– Dropping in base level
Local channels
– Rising in base level
Poor to well sorted litharenite gravels, sands and shales common
Sedimentary structures
– Fining upward cycles that fill channels
– Up dip channel cut and fill
– Gently dipping thin parallel lobate sheets perpendicular to channels
Geometries
– Confined incised channels
– Open lobate sheets perpendicular and occasionally parallel to channels
Fauna & flora
“Clastic Hierarchies”
Christopher G. St. C. Kendall
– Terrestrial flora can be common in over bank sediments
181. Fluvial Depositional Systems
Dominant conduit from regions of sediment
production (mountains) to sediment storage
(oceans, basins)
Characterized by channel pattern
Meandering
Braided
Anastomozing
Characterized by sediment load
Bedload
Suspended load
Mixed load
Unidirectional sediment dispersal
“Clastic Hierarchies”
Christopher G. St. C. Kendall
210. Past Glacial Periods
Pre-Cambrian at end of Neoproterozoic eon
End of the Ordovician
Late Carboniferous (Pennsylvanian]
through Permian
Pleistocene
“Clastic Hierarchies”
Christopher G. St. C. Kendall
212. The Snowball Earth
During last ice age max, 21,000 years ago, North
America & Europe covered by glaciers over 2
kilometers thick, sea level dropped 120 meters.
Global chill : land & sea ice covered 30 %t of Earth,
more than at other times in last 500 million years
Near end of Neoproterozoic eon (1000-543 million
years ago), glaciation immediately preceded first
appearance of recognizable animal life some 600
million years ago
“Clastic Hierarchies”
Christopher G. St. C. Kendall
213. Paul Hoffman & Daniel Schrag - Snowball Earth
Sun abruptly cooled or Earth tilted on its axis or
experienced an orbital blip that reduced solar
warmth or carbon dioxide increased?
ice sheets covered continents & seas froze
almost to equator, events that occurred at least
twice between 800 million & 550 million years
ago
Each glacial period lasted millions of years &
ended under extreme greenhouse conditions.
Climate shocks triggered evolution of
multicellular animal life, & challenge long-held
assumptions regarding the limits of global
change
“Clastic Hierarchies”
Christopher G. St. C. Kendall
217. Glacial System Characteristics
Signal extremes in local climate & sea level position
Stratigraphic markers of glacial events
Source of tillite (pebbles & larger fragments supported in
fine-grained matrix ) deposited from glaciers.
Massive tillite inferred deposited below ice sheets or dropping
from marine supported ice in submarine setting
Banded tillite may be deposited by ice sheets
Laminites common in lakes (Varve), Loess dust on land
Supraglacial & pro-glacial deposits with stratified
conglomerates & sandstone
U Shaped valleys & glacial striae
Mountain glaciation could be source of much downslope
fluvial sediment
“Clastic Hierarchies”
Christopher G. St. C. Kendall
218. Simplified Glacial Systems signals
Sediment signal a mix of:
Glacial carried & dumped in moraines
Water born fluvial sediment
Lacustrian varves
Aeolian loess
Erosion:
U-shaped valleys
Eroded rock surface
– Grooved
– Plucked
– Striated
“Clastic Hierarchies”
Christopher G. St. C. Kendall
Base level: changes in sea level.
219. Glacial Setting
Currently forms 10% of earths’s surface, Pleistocene
reached 30%, but in Pre Cambrian could have
reached 100%
Develop where all of annual snow doesn’t melt away
in warm seasons
Polar regions
Heavy winter snowfall e.g. Washington State
High elevations e.g. even equator
85% in Antarctica
10% in Greenland “Clastic Hierarchies”
Christopher G. St. C. Kendall
221. Glacial Erosion
Under glacier
Abrasion & plucking
Bedrock polished & striated
Rock flour washes out of glacier
Polishing and rounding
–
“Sheep Rocks”
Striations- scratches & grooves on rock
Above glacier
Frost wedging takes place
Erosion by glaciers steepens slopes
“Clastic Hierarchies”
Christopher G. St. C. Kendall
222. Roche Moutone – Ice Sheet Plucking
“Clastic Hierarchies”
Christopher G. St. C. Kendall
224. Glacial Sediments
Facies of continental glacial settings
Grounded Ice Facies
Glaciofluvial facies
Glacial lacustrine facies
– Facies of proglacial lakes
– Facies of periglacial lakes
Cold-climate periglacial facies
Facies of marine glacial settings
Proximal facies
Continental Shelf facies
Deepwater facies
“Clastic Hierarchies”
Christopher G. St. C. Kendall
225. Glacial Deposition
Till
Unsorted debris in fine matrix
Erratic
Moraine- body of till
Lateral Moraine
Medial Moraine- where tributaries join
End moraine–
–
Terminal
Recessional
Ground moraine
Drumlin
“Clastic Hierarchies”
Christopher G. St. C. Kendall
234. Glacial Sediments
Facies of continental glacial settings
Grounded Ice Facies
Glaciofluvial facies
Glacial lacustrine facies
– Facies of proglacial lakes
– Facies of periglacial lakes
Cold-climate periglacial facies
Facies of marine glacial settings
Proximal facies
Continental Shelf facies
Deepwater facies
“Clastic Hierarchies”
Christopher G. St. C. Kendall
235. Glacial Systems - Conclusions
Signal extremes in local climate & sea level position
Stratigraphic markers of glacial events
Source of tillite (pebbles & larger fragments supported in
fine-grained matrix ) deposited from glaciers.
Massive tillite inferred deposited below ice sheets or dropping
from marine supported ice in submarine setting
Banded tillite may be deposited by ice sheets
Laminites common in lakes (Varve), Loess dust on land
Supraglacial & pro-glacial deposits with stratified
conglomerates & sandstone
U Shaped valleys & glacial striae
Mountain glaciation could be source of much downslope
fluvial sediment
“Clastic Hierarchies”
Christopher G. St. C. Kendall
236. Simplified Conclusions Glacial Systems
Sediment signal a mix of:
Glacial carried & dumped moraines
Water born fluvial sediment
Lacustrian varves
Aeolian loess
Erosion:
U-shaped valleys
Eroded rock surface
– Grooved
– Plucked
– Striated
“Clastic Hierarchies”
Christopher G. St. C. Kendall
Base level: changes in sea level.
239. Aeolian System – Desert & Coast
Distribution of Aeolian systems – Holocene &
Ancient
Deserts: Transport & Depositional Sytems
Wind & Fluvial Action
Deposits of Modern Deserts
Dunes
Interdunes
Sheet Sands
Aeolian Systems
Bounding Surfaces
Ancient Deposits
“Clastic Hierarchies”
Christopher G. St. C. Kendall
240. Simplified Desert Systems signals
Sediment signal a mix of:
Aeolian sediment – dunes and sheets
Water born intermittent fluvial sediment
Playas and lakes
Aeolian loess
Erosion:
Water table “Stokes Surfaces” marks limit
Incised valleys
Gravel remnants
Rock pavements
Ventifacts
Base level: changes in ground water level.
“Clastic Hierarchies”
Christopher G. St. C. Kendall
241. Desert
Region with low precipitation
Usually less than 25 cm rain per year
Distribution
Most related to descending air
Belts at 30 degrees North & South latitude
Rain shadow of mountains
Great distance from oceans
Tropical coasts beside cold ocean currents
Polar desserts
“Clastic Hierarchies”
Christopher G. St. C. Kendall
246. Deserts – Dune Factories
Common characteristics: Lack of through-flowing streams
Internal drainage
Local base levels
Desert thunderstorms
Flash floods
–
Mudflows
Dominated by water transportation
“Clastic Hierarchies”
Christopher G. St. C. Kendall
247. Deserts – Depositional Systems
Dunes fed by water transported
sediment
Margin rimmed by incised seasonal streams
(Wadiis or Arroyo)
In turn flanked by alluvial fans and rock
pavements or bajada
Intermittent drainage supplying sediment
Dunes
Playas
“Clastic Hierarchies”
Christopher G. St. C. Kendall
249. Alluvial fans – Death
Valley
“Clastic Hierarchies”
Christopher G. St. C. Kendall
250. Salt Pan & Alluvial Fans – Death Valley
“Clastic Hierarchies”
Christopher G. St. C. Kendall
251. Sediment Source - Deserts & Coasts
Abundant sediment supply (sand, silt)
Favorable wind regimes
Grain transport in wind
Transport populations & resultant deposits
i. Traction (deflation pavements)
ii. Saltation (sand dunes)
iii. Suspension (loess)
III. Subenvironments of eolian dune systems
Dominated by water transportation
“Clastic Hierarchies”
Christopher G. St. C. Kendall
252. Wind Erosion and Transportation
Sand
Moves along ground- saltation
Sandstorms
Sandblasting up to 1 meter
–
Ventifact
Deflation
Blowout
Dust storms
“Clastic Hierarchies”
Christopher G. St. C. Kendall
254. Brice Canyon - Utah
“Clastic Hierarchies”
Christopher G. St. C. Kendall
255. Arches National Park – Utah
“Clastic Hierarchies”
Christopher G. St. C. Kendall
256. Wind Erosion and Transportation
Dust storms
Sand
Moves along ground- saltation
Sandstorms
Sandblasting up to 1 meter
–
Ventifact
Deflation
Blowout
“Clastic Hierarchies”
Christopher G. St. C. Kendall
258. Wind Action
Strong in desert because:
Low humidity
Great temperature ranges
More effective because of lack of
vegetation
Effective erosion in deserts because
sediment is dry
“Clastic Hierarchies”
Christopher G. St. C. Kendall
259. Wind Erosion and Transportation
Sand
Moves along ground- saltation
Sandstorms
Sandblasting up to 1 meter
–
Ventifact
Deflation
Blowout
Dust storms
“Clastic Hierarchies”
Christopher G. St. C. Kendall
262. Wind Erosion and Transportation
Sand
Moves along ground- saltation
Sandstorms
Sandblasting up to 1 meter
–
Ventifact
Deflation
Blowout
Dust storms
“Clastic Hierarchies”
Christopher G. St. C. Kendall
263. Red Sea Dust Storm
RedSeaDustStorm
“Clastic Hierarchies”
Christopher G. St. C. Kendall
264. North Africa - Sea Dust Storm
“Clastic Hierarchies”
Christopher G. St. C. Kendall
265. Wind Erosion and Transportation
Dust storms
Wind-blown dust accumulates in the deep
ocean floor at a rate of 0.6 x 1014 g/year.
“Clastic Hierarchies”
Christopher G. St. C. Kendall
278. Hierarchies exhibited by aeolian
and associated sediments
Grains
Ripples
Dunes
Interdune unconfined sheets
Confined bodies of wadii channel fills
Playa unconfined sheets of heterogenous
chemical, wind and water transported
clastic sediments
“Clastic Hierarchies”
Christopher G. St. C. Kendall
279. Mechanisms of Aeolian Transportation
Rolling: 2-4 mm
Surface creep
20-25% of sand moves by grains shifted by
impacting saltating grains < 2 mm
Suspension: fine sand, silt, clay
Grains 0.1 mm are most easily moved by
wind; mostly > 2 m above the ground
surface
“Clastic Hierarchies”
Christopher G. St. C. Kendall
293. Some characteristics of deserts
Stream channels normally dry
covered with sand & gravel
Narrow canyons with vertical walls
Resistance of rocks to weathering
Desert topography typically steep and angular
“Clastic Hierarchies”
Christopher G. St. C. Kendall
294. Aeolian Sediment - Critical Character
Aeolian sediments evidenced by x-bedding with
high angle (30-34 degrees)
Horizontal thin laminae common locally
Sand rounded and frosted
Quartz coated by iron oxide suggests hot arid
and/or seasonally humid climate (exceptions)
Well Sorted: often unimodal but if bimodal two
populations present
Silt and clay minimal
“Clastic Hierarchies”
Christopher G. St. C. Kendall
295. Aeolian Sediment - Critical Character
Small & large scale cross bedding, with multiple
orientations within horizontal bedding
Grains in laminae well sorted, especially finer
sizes, sharp differences in size between lamina
Size ranges from silt (60 mu) to coarse & (2mm)
Max size transported by wind 1 cm but rare grains
over 5 mm
Larger grains (0.5 - 1.mm) often well rounded
Sands free of clay and clay drapes rare
Uncemented sands have frosted surfaces
Mica usually absent
Rules of thumb - Glennie1970
“Clastic Hierarchies”
Christopher G. St. C. Kendall
296. Aeolian sediment interpretation
Analyse sedimentology & internal architecture
with outcrop, cores and downhole imaging
Identify & seperate single aggradational units
bounded by regional deflation surfaces (deepscoured to flat surfaces)
Genetic models from cyclic recurrence in facies
Aggradation characterises near- continuous
accumulation
Internal facies evolution related to differences in
sediment budget & moving water table
Palaeosols provide evidence of climate change
“Clastic Hierarchies”
Christopher G. St. C. Kendall
297. Conclusions - Desert Systems - Simplified
Sediment signal a mix of:
Aeolian sediment – dunes and sheets
Water born intermittent fluvial sediment
Playas and lakes
Aeolian loess
Erosion:
Water table “Stokes Surfaces” marks limit
Incised valleys
Gravel remnants
Rock pavements
Ventifacts
Base level: changes in ground water level.
“Clastic Hierarchies”
Christopher G. St. C. Kendall
300. Lacustrian Systems
Critical characteristics of
system?
Geomorphologic & tectonic setting
Dominant sedimentary processes
Facies
Subdividing surfaces
Lithology
Sedimentary structures
Geometries – Confined versus open
Fauna & flora
“Clastic Hierarchies”
Christopher G. St. C. Kendall
301. Lake Systems – Simplified Signals
Sediment signal a mix of:
Lake Center –sheets and incised & unconfined turbidite cycles
Margins marked by alluvial fans & fluvial sediment
Reducing setting that favors organic preservation
Signal cycles in order from:
– Clastics & organics
– Limestone & organics
– Evaporites & organics
Base level: changes in ground water level
Origin of large lakes:
Continental break up
Continental collision
“Clastic Hierarchies”
Sags on craton
Christopher G. St. C. Kendall
302. Significance of Lake Systems
Signal extremes in local climate & geochemistry
Stratigraphic markers (Organics trap radioactive minerals)
Major source of hydrocarbons along Atlantic Margins
Major source of oil shale & gas in western USA & Canada
Major source of
Trona (Hydrated Sodium Bicarbonate Carbonate)
Borax (Hydrated Sodium Borate)
Sulfohalite (Na6ClF(SO4)2)
Hanksite (Sodium Potassium Sulfate Carbonate Chloride)
“Clastic Hierarchies”
Christopher G. St. C. Kendall
303. Lake Geomorphologic & Tectonic Setting
Temporary features forming 1% of earths’s land surface, filling:-
Major rifted, & faulted (Break-up) continental terrains – E. Africa
Major final fill of foreland basin – Caspian & Aral
Continental sags – Victoria, Kenya, Uganda, and Eyre
Glacial features including:
Moraine damming and/or ice scouring – Great Lakes
Ice damming
Landslides or mass movements
Volcanic activity including:
Lava damming
Crater explosion and collapse – Crater Lake
Deflation by wind scour or damming by wind blown sand - Fayum
Fluvial activity including
Oxbow lakes
Levee lakes,
Delta & barrier island entrapment
“Clastic Hierarchies”
Christopher G. St. C. Kendall
307. Lake Tanganyika
Lake levels have varied historical and earlier
Fossil and living stromatolites abundant around
the margins of Lake Tanganyika, Africa provides a
source of paleolimnologic and paleoclimatic
information for the late Holocene
late Holocene carbonates suggests that the
surface elevation of the lake has remained near
the outlet level, with only occasional periods of
closure
In past the lake draw down encouraged
evaporites
“Clastic Hierarchies”
Christopher G. St. C. Kendall
311. I so
la t
Be
lt o ed lin
d r a f i n te e a r
ina rio
ge r
Restricted
Entrances
To Sea
Organic Rich Lake Fill
Regional
Drainage
Away
From Margin
Arid Tropics Air System
“Clastic Hierarchies”
Wide Envelope of St. C. Kendall
Christopher G. surrounding continents
313. Lakes flanking Major Mountain Chains
“Clastic Hierarchies”
Christopher G. St. C. Kendall
314. Caspian and the Arral Sea
Bodies of fresh to saline water trapped on
craton behind major mountain chains
Tend to act as traps to clastics, carbonates
and evaporitic sediments
Climatic change is recorded in the record
of the sediment fill
Water draw down encourages evaporites
“Clastic Hierarchies”
Christopher G. St. C. Kendall
318. Great Lakes
Bodies of fresh water trapped on glacially
scoured depressions on craton behind
glacial moraines
Act as traps to clastic sediments
Climatic change is recorded in record of
sediment fill
Water draw down encourages precipitates
“Clastic Hierarchies”
Christopher G. St. C. Kendall
321. Ice Dammed Lake – Alaska
“Clastic Hierarchies”
Christopher G. St. C. Kendall
322. Lake Response to Stratification
“Clastic Hierarchies”
Christopher G. St. C. Kendall
323. Lake Sedimentary facies
Sedimentary signal like that of a foreshortened
Marine setting
Narrow shores with beaches and deltas
Finer sediments and turbidites fill the lake center
“Clastic Hierarchies”
Christopher G. St. C. Kendall
324. Lake Sedimentary facies
Presence of freshwater fossils
Lake sediments commonly better sorted than fluvial and periglacial
sediments
May (or may not) display a tendency toward fining upward and
inward towards the basin center
Lake sediments are predominantly fine grained sediments either
siliciclastic muds but may be carbonate sediments and evaporates
Typical sequence may produced as the lake dries up with a
coarsening upward sequence from laminated shales, marls and
limestones to rippled and cross-bedded sandstone and possibly
conglomerates
Lake sediment fill often shows cyclic alternation of laminae
Varves produced by seasonal variations in sediment supply and
lake circulation which changes the chemistry of the lakes
“Clastic Hierarchies”
Christopher G. St. C. Kendall
325. Lacustrian sedimentary geometries
Shore marked by linear beaches
Coarse to fine slope
Deeper water lake laminae and turbidites
Eclectic clastic and evaporitic sedments
“Clastic Hierarchies”
Christopher G. St. C. Kendall
336. Conclusions - Lake Systems
Sediment signal a mix of:
Lake Center –sheets and incised & unconfined turbidite cycles
Margins marked by alluvial fans & fluvial sediment
Reducing setting that favors organic preservation
Signal cycles in order from:
– Clastics & organics
– Limestone & organics
– Evaporites & organics
Base level: changes in ground water level
Origin of large lakes:
Continental break up
Continental collision
“Clastic Hierarchies”
Sags on craton
Christopher G. St. C. Kendall
