quaternary geomorphology a workshop for p.g. candidates december 18, 2010 dr. don thieme
TRANSCRIPT
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 out-of-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
Clay as particle size [< 2(4) microns] but alsomineral group (phyllosilicates)
Phi = - log D in millimeters
Geometric reduction: 1/2, 1/4, 1/16,...
Gravel is coarser than 2 mm
Sand is 1/16 - 2 mm, visible to naked eye.
Silt is too small to see but can be felt.
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
Three Major Particle Sizes
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)
ML (low plasticity clayey silt)
SP (Poorly-graded sand) (Well "graded" sedimentis actually poorly sorted.)
Major Divisions (USCS) Symbol Description
GW Well-graded gravelsCLEANGRAVELS(< 5% fines)
GP Poorly-graded gravels
GM Silty gravels
GRAVEL ANDGRAVELLY
SOIL(>50% coarser
than no. 4)GRAVELS
WITH FINES(>12% fines)
GC Clayey gravels
SW Well-graded sandsCLEAN SANDS(<5% fines)
SP Poorly-graded sands
SM Silty sands
COARSEGRAINED
SOILS
(> 50% largerthan no. 200
sieve)
SAND ANDSANDY SOIL
(>50% finer thanno. 4)
SANDS WITHFINES
(>12% fines)SC Clayey sands
Major Divisions (USCS) Symbol Description
ML Inorganic or clayey silts of low plasticity
CL Inorganic lean clays
SILTS ANDCLAYS
(low plasticity)
OL Organic silts and clays of low plasticity
MH Elastic silts (micaceous or diatomaceous soils)
CH Inorganic clays or fat clays
FINEGRAINED
SOILS
(50% or >50%finer than no.
200 sieve)
SILTS ANDCLAYS
(high plasticity)
OH Organic silts and clays of high plasticity
HIGHLY ORGANICSOILS
PT Peats and Swamp soils with high organiccontent
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"
Kingdom Order 12
Phylum Suborder 60
Class Great Group 303
Order Subgroup
Family Family
Genus Series >17,000
Species Phase
Biology Soil Science Number
USDA Soil Taxonomy
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
Associations and Complexes descriptions may include useful summaries of regional physiography and local landformsSoil Catena diagrams show how soils vary across a landscape (RELIEF)
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, ...
Soil CatenaSoil 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