Quaternary Geomorphology
A Workshop for P.G. Candidates
December 18, 2010
Dr. Don Thieme
• Geochronology, Glacial
Intervals, Isotopic Dating, etc...
• Glacial Landforms and
Sedimentary Deposits
• Soil Classification and Paleosols
• Sea Level and Coastal
Geomorphology
Soil Classification
and Paleosols
Soil
• Engineering definitions • all unconsolidated materials above bedrock
(regolith)
• any material that can be moved without blasting
• Soil Science definition - A natural body,
occurring at the Earth's surface, consisting
of layers or horizons of mineral and organic
materials, capable of supporting plants outof-doors.
• Most of the elements essential for plant
growth are obtained from soil.
Soil Formation
• a continuous interaction between the
Earth's solid crust and the biosphere
• new soil material is added
• from below by weathering of rock
• from above as sediment is transported to the soil
surface by
• water (alluvial)
• gravity (colluvial)
• wind (aeolian)
Sediment
• solid material settling out of a fluid
• weathered rock detritus
• matter deposited by
• water (alluvial)
• wind (aeolian)
• gravity (colluvial)
• Clasts are particles in sediment or sedimentary
rock which derive from preexisting rock
Udden-Wentworth Scale
Phi = - log D in millimeters
Gravel is coarser than 2 mm
Geometric reduction: 1/2, 1/4, 1/16,...
Sand is 1/16 - 2 mm, visible to naked eye.
Silt is too small to see but can be felt.
Clay as particle size [< 2(4) microns] but also
mineral group (phyllosilicates)
Three Major Particle Sizes
Property
Sand
Silt
Clay
Particle diameter (mm)
2.0 - 0.05
0.05 - 0.002
< 0.002
Means of observation
Naked eye
Microscope
Electron microscope
Dominant minerals
Primary
Primary and
secondary
Primary
Attraction of particles for each other
Low
Medium
High
Attraction of particles for water
Low
Medium
High
Retention of plant nutrients
Very low
Low
High
Consistence when wet
Loose, gritty
Smooth
Sticky, malleable
Consistence when dry
Very loose,
gritty
Powdery, some
clods
Hard clods
Soil Texture
Soil Property
Sandy
Loam
Clayey
Aeration
Excellent
Good
Poor
Drainage
Excellent
Good
Poor
Mineral Content
Low
Medium
High
Water Holding Capacity
Low
Medium
High
Workability
Easy
Moderate
Difficult
Unified Soil Classification
System (USCS)
Basis for USCS
• Percentage of gravels, sands and fines
• Shape of the grain size distribution curve
• Plasticity
Three Categories
• Coarse-grained (G for gravel; S for sand)
• Fine-grained (M for silt; C for clay
• Highly organic (O for organic; P for peat)
SP (Poorly-graded sand)
ML (low plasticity clayey silt)
(Well "graded" sediment
is actually poorly sorted.)
Major Divisions (USCS)
Symbol
Description
GRAVEL AND
GRAVELLY
SOIL
(>50% coarser
than no. 4)
CLEAN
GRAVELS
(< 5% fines)
GW
Well-graded gravels
GP
Poorly-graded gravels
GRAVELS
WITH FINES
(>12% fines)
GM
Silty gravels
GC
Clayey gravels
CLEAN SANDS
(<5% fines)
SW
Well-graded sands
SP
Poorly-graded sands
SM
Silty sands
SC
Clayey sands
COARSE
GRAINED
SOILS
SAND AND
(> 50% larger SANDY SOIL
than no. 200 (>50% finer than
no. 4)
sieve)
SANDS WITH
FINES
(>12% fines)
Major Divisions (USCS) Symbol
SILTS AND
CLAYS
(low plasticity)
FINE
GRAINED
SOILS
(50% or >50%
finer than no.
200 sieve)
SILTS AND
CLAYS
(high plasticity)
HIGHLY ORGANIC
SOILS
Description
ML
Inorganic or clayey silts of low plasticity
CL
Inorganic lean clays
OL
Organic silts and clays of low plasticity
MH
Elastic silts (micaceous or diatomaceous soils)
CH
Inorganic clays or fat clays
OH
Organic silts and clays of high plasticity
PT
Peats and Swamp soils with high organic
content
Soil Forming Factors
•
•
•
•
•
Climate
Organic Matter
Parent Material
Relief
Time
S = f (cl, o, p, r, t) - equation of Hans Jenny
Soil Genesis
• The properties of a soil formed in any given
location, the horizons present, and their
sequence depends on the combination of soil
forming factors present.
• Prairie: A-B-C
• Floodplain: A-C-A-C-A-C
• Forest: O-A-E-B-C
Pedogenic Regimes
• Laterization
•
•
Removal of Silica
Dissolution of nearly all minerals, leaving
• Quartz
• Iron and Aluminum Oxides
•
Rapid decomposition of Organic Matter
• Laterite Soils are classified as Oxisols under
the USDA Soil Taxonomy
Lateritic soil near Savusavu on the Fijian Island of Vanua Levu
Pedogenic Regimes
• Podzolization
•
Acid soil solution results in
• Elluviation of A and/or E horizons
• Illuviation of Iron and Aluminum Oxides, Clay, and
Organic Matter down profile into B horizon(s)
•
Acid organic litter and limited nutrient
requirements (Boreal Forest, Coastal Plain of SE
USA)
• Podzol soils are classified as Spodosols in
the USDA Soil Taxonomy
"Podzolic" Soil
Profile (Spodosol)
on Trail Ridge at
Hoboken, GA
Pedogenic Regimes
• Gleization
• waterlogged environment
with poor drainage
• dark, highly organic A
horizon
• lack of oxygen (anaerobic
condition) inhibits decay
• low chroma and mottling in B
horizon
"Gleyed" Bg and Cg
Soil Horizons in a
Histosol profile
Pedogenic Regimes
• Calcification
• CaCO3 carried downward in
profile
• concentrated in B horizon,
sometimes as hardpan
• capillary water and grass roots
carry CaCO3 back toward
surface
"Calcic" Bk Soil
Horizon in a Mollisol
profile
Pedogenic Regimes
• Salinization
•
•
•
•
•
Salts carried downward in profile
Chlorides (CaCl, NaCl)
Sulfates (CaSO4, Na2SO4)
Toxic to most plants and soil organisms
Salic soils in western United States support only
sage and "saltbush"
USDA Soil Taxonomy
Biology
Kingdom
Phylum
Class
Order
Family
Genus
Species
Soil Science
Number
Order
Suborder
Great Group
Subgroup
Family
Series
Phase
12
60
303
>17,000
Ultisols, Spodosols, Entisols, Histosols, Alfisols
SOIL MAPPING UNITS
Series - basic unit of mapping for county
soil surveys in the United States. Soils
mapped as one series are similar in all
major profile characteristics
Phase - subdivision based upon some
important deviation that influences the
use of the soil.
•
•
•
•
•
Texture
Drainage Class
Slope
Stoniness
Salt Content
SOIL MAPPING UNITS
Consociation - should be 50% pure soil
that represents one phase of one soil
series. There should be less than 15%
inclusions of contrasting soils that
differ in major profile characteristics.
Complex - contains two or three distinctly
different soil series which occur so closely
adjacent that they cannot be mapped
separately on detailed map sheets.
Association - maps at 3rd order or higher
may group soils together which could be
distinguished on detailed map sheets
COUNTY SOIL SURVEYS
General Soil Map - in color at a scale of
approximately 1:200,000 showing soil
associations which correspond to major
physiographic regions in a county of the
United States
Detailed Map Sheets - folded in the back of
the report as an overlay on aerial
photographs at 1:20,000
Profile Descriptions - representative "pedon"
of each series
COUNTY SOIL SURVEYS
Characterization data in Tables at the back
of each survey.
• Older characterization focused on agricultural
requirements (yields, suitability, drainage,
etc...)
• Newer characterization includes wildlife
habitat, forestry, waste disposal, ...
Associations and Complexes descriptions may
include useful summaries of regional
physiography and local landforms
Soil Catena diagrams show how soils vary
across a landscape (RELIEF)
Soil Catena
Catena diagram for Plymouth County, Massachusetts
Paleosols
• soil formed on a landscape
of the past
• can sometimes be
classified into a soil order
• record of past climate
• Formation of Soils and Deep Regoliths occurred
primarily during interglacial intervals in the
Quaternary
• particularly in temperate latitudes
• more gradual and less discrete than glacial
processes of deposition and erosion
Dune-Interdune Soils
• in Mauritania and Mediterranean region bordering
Sahara Desert
• Early Holocene paleosol found on summit and
shoulder positions rerpresenting periods of moist
climate
Soil Horizons and Time
Soil Orders and Time
Interglacial Paleosols, USA
Sangamon
Yarmouth
Tibetan Plateau,
Western China
Soils across a Fault Scarp
(Wasatch Fault Zone, Utah)
County Dump Fault,
New Mexico
• 500 thousand years of
normal faulting with
intervening periods of
soil formation
• Soils show varying
degrees of
calcification,
development of Bk
horizons
• Hachures are spaced
in proportion to degree
of soil development
Soils disrupted by the La Jencia fault, New Mexico
Geoarcheology - Lubbock Lake, TX