Post on 05-Apr-2018
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NOTES ONAPPLIED GEOLOGY
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BEDDING
Bed :
Sedimentation unitgreater than 1cm.
Lamina:
Sedimentation unitsmaller than 1cm.
Interbedded:between two things
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STRATIGRAPHY
Stratigraphic unit
A naturally occuring body of rock or rockmaterial which is distinguished from
adjoining rock on the basis of some statedproperty or properties.
1.Lithostratigraphic unit.
2.Biostratigraphic unit.3.Chronostratigraphic unit.
4.Geochronologic unit.
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Lithostratigraphic Unit
(( is a stratum or body of strata,generally layered which conforms
to the law of superposition and isdistinguished and delimited on thebasis of lithic characteristics and
stratigraphic position.))
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Nature of Lithostratigraphic Units
Type section andlocality.
Independence frominferred Geologichistory.
Independence from
time concepts.
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Boundaries
Are placed at positions oflithic change.
Boundaries in lateral lithologic change.
Correspondence with generic units.
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Lithostratigraphic boundaries
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Rank of Lithologic Units
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Formation
It is the fundamental unit inlithostratigraphic classification.
Content:
A formation should posses some degree ofinternal homogeneity or distinct features.
i. One lithic type.
ii. Repetitions of two or more lithic types.
iii. Extrem lithic heterogenity.
Lithic characteristics.
Mappability and thickness.
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Lithostratigraphic Nomenclature
Compound character:
Geographic +Lithic term+ Rank.
Geographic + Rank.Geographic + Lithic + Rank.
Use of Simple lithic terms.
Misuse of well known name.
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Clay Minerals
A term reserved for those constituents of aclay which give it its plastic properties. They
are hydrous aluminosilicates.
Generally occur as minute, platy, rarely fibrouscrystals.
Some contain loosely bonded cations which canbe easily exchanged.
Ability to loose or take up water. Produced by the degradation of other silicates.
Both two and three layered types are known.
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The sheets of clay minerals
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Clay minerals (continue)
Layers of Al - O/OH are called gibbsite.
Layers of MgO/OH are called brucite. The stacking arrangement of the sheets
determine the clay mineral type, as does
the replacement of the Si and Al inons.
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I. Kandit Group
Members have two layeredstructure consisting of a silicatetrahedral sheet linked to analumina octahedral sheet bycommon O/OH ions.
No replacement occur for Si
or Al. The structure formula is
(OH)4Al2Si2O5. e.g Kaolinite
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II. Smectite Group
Members have a threelayered structure.
Have ability for Al and Siexchange.
Have ability for absorbingwater.
e.g Montmorillonite(Mg,Ca)O.Al2O3.5SiO2.nH2O
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Three layered structure.
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Diagensis
Pre-Burial changes:
1. Burrowing organismseffect.
2. Adjustment to eH andpH.
3. Adjustment to majorcations.
4. Development ofAuthigenic menerals.
Early-Burial changes
1. Continuation of 2 & 3.
2. Oxidation of carbonaceous
material.3. Continuation of compaction.
4. Probable initiation ofconcretions.
5. Start of primary cementation.6. Some conversation of
aragonite to calcite, anddevelopment of dolomite.
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Diagensis(continue)
Late Burial Changes:
Cease of eH and pHadjustments.
Completion of compaction.
Authigenic mica & chlorite.
Completion of concretions
development andcementation.
Replacement of aragoniteby calcite; dolomitization.
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Sedimentary Rock Types
Rocks formed from material derived
from pre-existing rocks byprocesses of denudation, together
with material of organic origin.
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Lithological Description
1. Type of formation (Limestone, sandstone,shale).
2. Colour.
3. Texture.4. Cementing material.
5. Hardness.
6. Porosity.
7. Minor components (accessories).
8. Staining and fluorescence (oil shows).
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3. Texture
Sediments with visible graine size:1. Size,
2. Sorting,
3. Roundness,
4. Sphericity. Sediments with crystalline appearance.
estimate crystallinity:
1. Microcrystalline
2. Cryptocrystalline3. Succrose
Sediments without recognizable size at ordinarymicroscope:
Descripe the morphology of the cutting.
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Dunham Classification
Depositional texturenot recognized.
Crystalline carbonate.
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Mud supported
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Grain supported
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Dunham ClassificationDepositional
texture notrecognisable
Depositional texture recognisable
Originalcomponentsboundtogetherduringdeposition
Original components not bound together duringdeposition.
Lacks mud
and is grainsupported
Contain mud (particles 10%
grains
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Dunham Classification
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5. Hardness
Hardness is a reflection of degree ofcementation.
1. Soft or friable
2. Moderately hard; fairly cemented.
3. Hard; moderately cemented.
4. Very hard; well cemented.
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6. Porosity
Porosity could be estimated from hardness andcementation.
Archi classification matrix porosity
I. Compact, dense, hardII. Chaiky, earthy, soft.III. Sugary, loose, poorly cemented. Visible porosityA. No visible pores w/ 10x
B. Visible w/ 10xC. Visible w/ eye.D. Larger than 2 mm
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7. Minor constituents
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Oil Shows DescriptionA. In Normal Light
PercentageNo visible stain
Poor stain
Fair stain
Good stain
40%
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Oil Shows DescriptionA. In Normal Light
Distribution Uniform Scattered Spoty Streaked Shade
V. Light LightMedium Dark Very dark Hue
Green Yellow Brown Black
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Oil Shows DescriptionB. Under UV Light
IntensityNo florescence
Faint
Dull
bright
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Oil Shows DescriptionB. Under UV light
Distribution Uniform Scattered
Spoty Streaked
Shade
V. Light Light
Medium Dark
Very dark
Hue
Blue
white Yellow, Orange
Gold
Brown
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