Improving Correlation Between Landform and Parent Material

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Improving Correlation Between Landform and Parent
Material

• MO6 Soils Workshop
• March 2009

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Issues

• Recent QA reviews continue to find errors and
  inconsistencies in identifying, using, and
  assigning parent material and landform.

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A Few Examples

• Alluvium on mountainsides, 50 slopes
• Risers on alluvial flats
• Outwash on stream terraces
• Backslopes on fan remnants
• Colluvium on alluvial fans
• Colluvium and alluvium derived.
• Abuse of the term residuum
• Abuse of the term mixed sources

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Lets Review

• The National Standards for Landforms and Geologic
  Terms are
• Geomorphic Description System 4.11, June 2008
• Groups Landforms by Geomorphic Process
• Diagrams and Illustrations
• This is also contained in the Field Book for
  Describing and Sampling Soils
• ftp//ftp-fc.sc.egov.usda.gov/NSSC/GDS/GDS_v4_11.p
  df
• National Soil Survey Handbook, Part 629, Glossary
  of Landform and Geologic Terms
• Definitions of landforms, parent materials, and
  geologic terms
• ftp//ftp-fc.sc.egov.usda.gov/NSSC/Soil_Survey_Han
  dbook/629.doc

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• Additional Sources of Information and Guidance
• Previous Geomorphic Tours in the MLRA
• MO QA Staff and Guidance Documents

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Soil Formation

• The process of climate, topography, and biota
  (living organisms) acting upon parent material
  (rock or unconsolidated sediments) over time to
  produce soil. Soil evolution is dependent on the
  dynamic interaction of the five soil forming
  factors, time, topography, climate, biota, and
  parent material over time.

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Parent Material

• From NSSH Part 629 The unconsolidated and more
  or less chemically weathered mineral or organic
  matter from which a soils solum is developed by
  pedogenic processes.
• It is the initial state in the soil forming
  process.
• Categorized by the original source and the most
  recent mode of transportation of the resulting
  material.
• It is common for a pedon to have more than one
  type of parent material present, i.e.
• Slope alluvium derived from sandstone over
  residuum derived from shale

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Parent Material continued

• Sources
• Sandstone
• Shale
• Granite
• Etc
• General Forces of Transportation
• Wind
• Water
• Gravity
• Glaciers
• Volcanic

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Transported Materials

• Wind transported
• Eolian Deposits predominantly sand sized
  (0.1-2mm) particles
• Loess Deposits- predominantly silt sized
  (.002-0.1mm) particles

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Transported Materials

• Water transported
• Alluvium Unconsolidated, clastic material
  subaerially deposited by running water, including
  gravel, sand, silt, clay, and various mixtures of
  these. This term is not to be used with soils
  formed from glacial melt water.
• Often conflicted with slope alluvium
• Should only be used for materials laterally
  deposited by channelized water flow, i.e.
  streams, intermittent streams, and rivers.

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Transported Materials

• Water transported
• Slope Alluvium Sediment gradually transported
  down mountain or hill slopes primarily by
  non-channel alluvial processes (i.e., slope wash
  processes) and characterized by particle sorting.
  Lateral particle sorting is evident on long
  slopes. In a profile sequence, sediments may be
  distinguished by differences in size and/or
  specific gravity of coarse fragments and may be
  separated by stone lines. Sorting of rounded or
  subrounded pebbles or cobbles and burnished peds
  distinguish these materials from unsorted
  colluvial deposits.
• Often conflicted with alluvium. Probably the
  most common parent material.
• Should always be considered for sloping landforms
  where alluvium and colluvium are not
  possibilities.

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Transported Materials

• Water transported
• Lacustrine Deposit NSSH - Clastic sediments and
  chemical precipitates deposited in lakes.
• Rare in the MO6 Region. Associated with ancient
  lake sediments, i.e. Lake Alamosa in the San Luis
  Valley area of Colorado.

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Transported Materials

• Glacier transported
• Outwash - glacial geology - Stratified and
  sorted sediments (chiefly sand and gravel)
  removed or "washed out" from a glacier by
  melt-water streams and deposited in front of or
  beyond the end moraine or the margin of a
  glacier. The coarser material is deposited nearer
  to the ice. Similar to alluvium except the
  water can be traced to melting glaciers.

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Transported Materials

• Glacier transported
• Till glacial - Dominantly unsorted and
  unstratified drift, generally unconsolidated and
  deposited directly by a glacier without
  subsequent reworking by meltwater, and consisting
  of a heterogeneous mixture of clay, silt, sand,
  gravel, stones, and boulders rock fragments of
  various lithologies are imbedded within a finer
  matrix that can range from clay to sandy loam.

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Transported Materials

• Gravity transported
• Mass Movement A generic term for any process or
  sediments (mass movement deposit) resulting from
  the dislodgment and downslope transport of soil
  and rock material as a unit under direct
  gravitational stress. The process includes slow
  displacements such as creep and solifluction, and
  rapid movements such as landslides, rock slides,
  and falls, earthflows, debris flows, and
  avalanches. Agents of fluid transport (water,
  ice, air) may play an important, if subordinate
  role in the process.

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Transported Materials

• Gravity transported
• Colluvium - Unconsolidated, unsorted earth
  material being transported or deposited on side
  slopes and/or at the base of slopes by mass
  movement (e.g. direct gravitational action) and
  by local, unconcentrated runoff.
• Slope percent should never be used as the sole
  criteria for using colluvium. Colluvium can
  occur on 5 slopes and not occur on 50 slopes.
  Evidence of mass movement must be present to
  support the use of Colluvium.

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Transported Materials

• Volcanic transported
• Volcanic (adjective) Pertaining to (a) the deep
  seated (igneous) processes by which magma and
  associated gases rise through the crust and are
  extruded onto the earths surface and into the
  atmosphere, and (b) The structures, rocks, and
  landforms produced.
• Ash, tuff, basalt, rhyolite, pyroclastic flows,
  etc.

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Non-Transported Material

• Residuum - (residual soil material)
  Unconsolidated, weathered, or partly weathered
  mineral material that accumulates by
  disintegration of bedrock in place.
• Frequently abused. The mere presence of bedrock
  does not warrant the use of Residuum. There must
  be evidence that the soil material directly above
  the bedrock has weathered from the underlying
  bedrock. A paralithic layer over a lithic layer
  of the same geology is common evidence.
  Weathering rinds at the top of the lithic contact
  is also evidence.
• Rarely are soils formed entirely in Residuum.
  Most of the time there is at least one overlying
  parent material, i.e. slope alluvium derived from
  sandstone over residuum derived from shale.

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Tips for Correctly Linking Parent Material and
Landform

• Use of the Geomorphic Description System and the
  NSSH Part 629.
• Develop a list of landforms and parent materials
  to be used in your MLRA SSA. Review and update
  as needed.
• Identify the most recent modes of transport and
  geomorphic processes in your pedon.
• Link the processes with the correct parent
  material and landform
• Fluvial process?alluvium?stream terrace
• Mass movement?colluvium?debris flow

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Tips for Correctly Linking Parent Material and
Landform

• Stack parent materials and landforms where
  appropriate
• Slope alluvium derived from sandstone over
  residuum derived from shale
• Colluvium derived from glacial fluvial deposits
  over colluvium derived from shale on rotational
  slides on mountain flanks
• When stacking parent materials make sure the word
  over is used rather than and, i.e. colluvium
  over residuum and not colluvium and residuum

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Other Tips

• For MUDs, TUDs, and OSDs list only the most
  predominant landforms and parent materials. Keep
  it simple. Convey the central concept, not
  extremes.
• For parent material source try to be as specific
  as possible sandstone and shale, or granite,
  gneiss, and schist is preferred over the term
  mixed. Use of the term mixed will be
  limited. Its use will always be questioned
  during the QA review.

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Other Tips

• Use of hillslope profile terms summit, shoulder,
  backslope, footslope, toeslope, are restricted
  for use on hills only. These must not be used
  on other landforms.
• Ensure consistency between slope shape and the
  landform, i.e. concave depressions and not
  convex depressions.
• Use the MO6 NASIS report CHECK Geomorphic
  Properties to review your landform and parent
  material information for your survey area.
• Ask yourself, Does the process, landform, and
  parent material make sense?