contents - 1. soil morphology 2. soil macromorphology 3. soil micromorphology 4. techniques used in micromorphology study 5. some terms, definations and concept 6. soil mineral material 7. soil organic materials 8. application

1. COURSE NO- SOILS-501*
COURE TITLE- SOIL PHYSICS
PRESENTATION ON-
SOIL MICROMORPHOLOGY
COURSE INCHARGE-
Dr. G. Jayashree
(Dept. of soil science and agricultural
chemistry )
PRESENTED BY-
PUJA PRIYADARSINI NAIK
RAM/19-97

2. • Soil morphology deals with the form and arrangement of
soil features.
• Soil morphology deals with the form, structure, and
organization of the soil material, observed, described, and
studied in the field, but investigation can be continued in
the laboratory with optical and electron microscopes.
• Field observations with the unaided eye or with a hand lens
are considered macro morphology, whereas observations
utilizing a microscope are considered micromorphology.
SOIL MORPHOLOGY

3. • Macromorphology is best evaluated from the in situ
examination of the soil profile.
• A recently dug pit large enough for observation of a pedon is
desirable.
• Old exposures such as road cuts and ditches are acceptable
only for preliminary examination because morphological
features often become altered after prolonged exposure.
• The exposed profile should be probed by hand, with the aid of
a knife or small pick to remove any alterations resulting from
digging equipment and to expose the natural condition of the
soil.
Soil Macromorphology

4. • Micromorphology is a term used in biology, mineralogy and
soil science.
• The fine-level structures or morphology of an organism,
mineral, or soil component visible through microscopy.
• Micromorphology is the branch of earth science that describes,
interprets, and measures the components, features, and fabrics
of soils, regolith materials, and prehistoric/historic artifacts at
the microscopic and submicroscopic levels (Goldberg, 1983;
Stoops, 2003).
Soil micromorphology owes it popularity to the late Walter Kubiëna who saw
its potential as a tool to investigate some of the properties and processes in soils.
His two books “Micropedology” and “Soils of Europe” are landmarks in the
development of Soil Science.
Soil Micromorphology

5. • The basic technique in soil microscopy and micromorphology
involves the preparation of thin sections of undisturbed soil
materials, the samples being collected in boxes with double lids to
avoid disturbance.
• The outstanding developments include the use of synthetic resins
for improved impregnation and the increase in size of thin sections.
• The introduction of acetone as a diluent of the resins made it
possible to remove water from the samples by acetone exchange
thus reducing shrinkage.
• Over 45 ancillary techniques are used, including fluorescence,
image analysis and electron microscope analyses.
• Polished blocks may be adequate if a fluorescent dye is
incorporated in the impregnating resin as the block can then be
photographed with fluorescent light to show the distribution of the
pore pattern.
TECHNIQUES –

6. Fabric, Structure and Assemblage –
• Fabric is the mutual arrangement and relationship
between particles within the soil as a whole and within the
various features, while structure is the type and degree of
aggregation.
• The totality of all features in a specimen is called an
ensemble or assemblage.
• The main fabric relationships seen in thin sections are in
the fine earth, including both mineral and organic
materials. These may be observed in thin sections but in a
number of cases SEM is required.
Definitions, Concepts and Features

7. • This refers to the material with a diameter of less than about
20µm and which is beyond the resolving power of the
optical microscope.
• It may be arranged as granules, masses, and links between
grains or forms a complete matrix.
Burnham (1970) suggested seven different ways in which clay
particles might be arranged.
(A) fabric composed of randomly orientated clay particles
Fine material

8. (B) Fabric composed of
randomly orientated domains
(C) fabric of domains in parallel
alignment
(D) fabric of parallel orientated
clay particles with little
differentiation of domains
(E) granular particles of iron oxide,
organic matter or fine silt interfere
with the parallel orientation of the
clay particles

9. (F) randomly orientated domains may
occur between grains if coarse silt
(G) large sand particles with clay particles
aligned tangential to their surfaces

10. Material of any size forming a continuous phase surrounding
and enclosing coarser particles. Thus, a matrix may be
dominantly clay surrounding sand particles or silt surrounding
particles of gravel.
Matrix –

11. • The concepts of homogeneity and heterogeneity are difficult
to apply since a given volume of soil may at the same time
be homogeneous with regard to one property, for example
color, and heterogeneous with regard to another property
such as the sand mineralogy.
• Even the most uniform soils exhibit some degree of
heterogeneity which might be just visible in the field, but
conspicuous in thin sections.
• If, for example, a soil composed mainly of clay has a few
grains of silt, and more particularly quartz sand these will
appear conspicuous particularly when examined with
circularly polarized light.
Homogeneity and heterogeneity

12. Recognition of individual features –
• One of the most difficult tasks in micromorphology is
the recognition of individual features.
• Clay particles are themselves individuals; they cannot be
recognized with the optical microscope but can only be
identified with TEM or SEM techniques.
• Most thick clay coatings are easily recognized, but thin
clay coatings are extremely difficult to identify.
• The frequency of clay coatings in a given soil can vary
widely when estimated by different operators.

13. Recognition of patterns –
• Probably the most important aspect of micromorphology is
the recognition of patterns, not only the pattern of single
individuals but also the relationships between the individuals
themselves.
• The types of pattern range from the relatively simple
distribution of individual quartz grains to the often complex
distribution pattern of clay coatings.
• Probably the most difficult patterns to recognize are those of
the anisotropism of matrices. It is often difficult to describe
individuals and patterns.
• In many cases a true representation can only be achieved with
good photographs and diagrams.

14. Quantification of features –
• It has been shown that over 20 cores with two thin sections
from each core are required to characterize quantitatively
coatings, matrices, pores and concretions in horizons with
translocated clay.
• However, considerable success is being achieved by the
application of many image analysis techniques to thin
sections and polished blocks.

15. Interpretation of features and patterns-
• This is based on a combination of experience, intuition and guess-
work.
• Most workers agree that the majority of clay coatings have been
formed by the translocation of clay particles and their deposition
on surfaces.
• They also agree that clusters of calcite and gypsum crystals have
been formed by the translocation of calcium bicarbonate and
calcium sulfate and crystals growth.
• However the interpretation of some concretionary material in very
old tropical soils is extremely difficult.

16. Confirmation of the interpretations
• This will probably require experimentation.
• It may, however, not always be possible to reproduce in the
space of a few weeks or even months, those features that
have taken hundreds or thousands of years to form.
• Some researchers have nevertheless been able to produce
clay coatings similar to those found in natural soils in the
field, while others have demonstrated that certain forms of
matrix anisotropism can be produced by stress and shearing.

17. The main properties are:
 color,
 prominence,
 size,
 Shape,
 roundness,
 sphericity,
 surface characteristics,
 boundaries, distribution pattern,
 relationships between features and
 orientation.
Properties of features and minerals

18. Mineral Soil Material
Primary Minerals and Particle Size Classes
• The mineral material in soils ranges in size from the very smallest particle,
such as single grains of hematite >0.1 µm in highly weathered tropical soils
up to the largest erratic boulders found in glacial drift or core stone in
weathered rocks.
• The shape of the large separates often give a clear indication of the process
which have influenced the formation of the parent material or soil itself.
e.g.- Sand varies in shape from smooth and rounded to rough and angular.
Smooth and rounded shapes are found in wind-blown materials and beach
sands.
• The particle classes have different degree of mobility within the soil.
• The clay fraction is often considered as being the most mobile and forms
clay coatings, but by far the greatest amount of material is translocated by
the soil fauna including earthworms and termites.
• Therefore, thin sections should always be carefully examined for any
evidence of movement particularly by biological processes.

19. Secondary minerals
• The most frequently encountered secondary minerals in soils
include:
• The minerals that occur in amorphous or microcrystalline forms
include.
Anhydrite, allophane, aluminum hydroxide, barite, bassanite,
celestite, calcite, chalcedony, chlorite, ferrihydrite, gibbsite, geothite,
gypsum, hamatite, halite, halloysite, hydrous mica, iddingsite,
imogolite, jarosite,kaolinite, lepidocrocite, leucoxene, maghemite,
manganese dioxide, opal, pyrite, quartz, smectite,siderite and
vermiculite.
Allophone, chlorite, ferrihydrate, gibbsite, geothite, hematite,
halloysite,hydrousmica,jarosite,immogolite,kaolinite,leucoxene,lepido
crocite,opal,siderite,smectite and vermiculite

20. • The secondary minerals can be observed in different positions
in soils.
• Generally, they are found in matrix, in pores and in plant
material.
• They may occur as amorphous or microcrystalline material,
single grains, aggregates, clusters or fillings
Secondary minerals

21. (A)Bassanite with charactristics lozenge shape crystal with
cross cleavage
(B)Calcite forming a pendant beneath a round rock fragment
(C) Secondary chalcedony in a soil of an arid area, with its
well developed radial crystallization

22. (D) A cluster of gypsum crystals with their characteristic lozenge shape
(E)Ice from an ice wedge
(F) Vermiform kaolinite in weathered rock surrounded by clay coatings

23. (G) Brilliant white opal in calcrete revealed after the removal of calcite
(H) Cluster of spherical pyrite crystals in a plant fragment in a lower horizon of peat
(I) Biotite beings transformed into vermiculite, hence the variable interference colours;
the relatively fresh biotite still has its brilliant third order colours which grade to the paler
colour of the vermiculite
Secondary minerals

24. • Quartz is soluble but dissolves
very slowly and develops numbers
of distinctive morphology.
(A) irregular grains of quartz as a
result of etching during the
formation of opaque matrix of
manganese/iron oxide
The principle one undergoes
hydration is biotite.
(B)Initial stage of weathering of
biotite where the grains are split
apart
Chemical weathering
Solution
Hydration

25. Mineral Hydrolysis
• Hydrolysis is the most impt
process decomposing minerals.
(A)Gibbsitization of feldspar in
very strongly weathered granite
(B)Iddingsite peudomorph of
olivine and the surronding material
is gibbsite.

26. Physical weathering
• It is brought about by
hydration, exfoliation,
crystal growth, heating
and cooling and frost
action .
• In granite and similar
rocks the initial stage of
weathering is by granular
disintegration.

27. Biological weathering
• Very little work has been conducted at the microscopic
level on biological weathering of minerals except for the
effects of lichens on rock surfaces where hydrolysis is
induced and etching of minerals surfaces through the
secretion of various organic acid especially oxalic acid.

28. Faunal features
• A large number of
mesofauna live in the soil
or on the soil surface and
formation of a wide ranges
of features including
passages and faecal
material.
• These include earthworms,
enchytraeids, mites,
termites, nematodes, larvae
and mollusks.
Organic soil materials

29. Floral features

31. Applications
The number of disciplines currently using thin sections
on a regular basis, are –
1. AGRICULTURE
• The main contribution to this discipline is in the study of
soil structure, both natural and in the change that
accompany soil uses.
• The preparation of seed bed prior to the planting, being
one of the most important operation in crop production,
was studied by the use of thin sections.
• Fertilizers can also affect soil micromorphology.
• Irrigation may improve the soil structure in some cases.

32. 2.ARCHAEOLOGY
• Thin sections of pottery can also yield very useful
information about the history of an area and source of
material for manufacturing the pots.
• Ash can be used as an indicator of the type of plant
material that was used for fuel. And Wattez, Courty,
MacPhail(1990) used this for determining the nature of
fuel used in prehistoric caves.

33. 3. ENGINEERING
• At present engineers are in the process of accumulating
data about behavior of fabrics.
4. GEOMORPHOLOGY
• Thin sections are being used to study the erosion and
deposition process as especially differential erosion which
leaves behind an accumulation of coarse material.

34. 5. PALAEO-CLIMATOLOGY
• Thin sections have been also used to established the presence
of palaeocatenas which are better indicator of palaeo-climate
than indivisual palaesols.
6. PEDOLOGY AND PALAEOPEDOLOGY
• Thin sections are particularly valuable in the study of some
features like-
• Clay coatings
• Earthworm faecal material
• Gibbsite concentration
• Fragments of concentration
• Iron/Mn concentration
• Silt coating etc.

35. • Thanks