Deskripsi sample geologi

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NOTES ON APPLIED GEOLOGY



BEDDING

• Bed :

Sedimentation unit

greater than 1cm.

• Lamina:

Sedimentation unit

smaller than 1cm.

• Interbedded:between two things



STRATIGRAPHY

• Stratigraphic unit

A naturally occuring body of rock or rock

material 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.



Lithostratigraphic Unit

(( is a stratum or body of strata,

generally layered which conforms

to the law of superposition and isdistinguished and delimited on the

basis of lithic characteristics and

stratigraphic position.))



Nature of Lithostratigraphic Units

• Type section and

locality.

• Independence frominferred Geologic

history.

• Independence from

time concepts.



Boundaries

Are placed at positions of

lithic change.Boundaries in lateral lithologic change.

Correspondence with generic units.



Lithostratigraphic boundaries



Rank of Lithologic Units



Formation

It is the fundamental unit inlithostratigraphic classification.

• Content:

A formation should posses some degree of internal 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.



Lithostratigraphic Nomenclature

• Compound character:

Geographic +Lithic term+ Rank.

Geographic + Rank.Geographic + Lithic + Rank.

• Use of Simple lithic terms.

• Misuse of well known name.



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.



The sheets of clay minerals



Clay minerals (continue)

• Layers of Al - O/OH are called “gibbsite”.

• Layers of Mg – O/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.



I. Kandit Group

• Members have two – layered

structure consisting of a silica

tetrahedral sheet linked to an

alumina octahedral sheet by

common O/OH ions.

• No replacement occur for Si

or Al.• The structure formula is

(OH)4Al2Si2O5. e.g Kaolinite



II. Smectite Group

• Members have a three –

layered structure.

• Have ability for Al and Si

exchange.

• Have ability for absorbing

water.

• e.g Montmorillonite(Mg,Ca)O.Al2O3.5SiO2.nH2O



Three – layered structure.



Diagensis

• Pre-Burial changes:

1. Burrowing organisms

effect.

2. Adjustment to eH andpH.

3. Adjustment to major

cations.

4. Development of Authigenic menerals.

• Early-Burial changes

1. Continuation of 2 & 3.

2. Oxidation of carbonaceous

material.3. Continuation of compaction.

4. Probable initiation of

concretions.

5. Start of primary cementation.6. Some conversation of

aragonite to calcite, and

development of dolomite.



Diagensis (continue)

• Late – Burial Changes:

• Cease of eH and pH

adjustments.

• Completion of compaction.

• Authigenic mica & chlorite.

• Completion of concretions

development andcementation.

• Replacement of aragonite

by calcite; dolomitization.



Sedimentary Rock Types

Rocks formed from material derived

from pre-existing rocks byprocesses of denudation, together

with material of organic origin.



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).



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.



Dunham Classification

• Depositional texture

not recognized.

• Crystalline carbonate.



Depositional texture recognized

• Depositional texture

recoginized.

• Original componentsbound together

• Boundstone.



Mud supported



Grain supported



Dunham ClassificationDepositional

texture notrecognisable

Depositional texture recognisable

Original

components

bound

together

during

deposition

Original components not bound together during

deposition.

Lacks mud

and is grainsupported

Contain mud (particles<20m)

Grain

supported

Mud supported

> 10%

grains

< 10%

grainsCrystalline

carbonate

Boundstone Grainstone Packstone Wackstone Mud

stone



Dunham Classification



5. Hardness

Hardness is a reflection of degree of

cementation.

1. Soft or friable

2. Moderately hard; fairly cemented.

3. Hard; moderately cemented.

4. Very hard; well cemented.



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 porosity

A. No visible pores w/ 10x

B. Visible w/ 10x

C. Visible w/ eye.

D. Larger than 2 mm



7. Minor constituents



Oil Shows Description A. In Normal Light

• Percentage

No visible stain

Poor stain

Fair stain

Good stain

40%



Oil Shows Description A. In Normal Light

• Distribution Uniform Scattered

Spoty Streaked

• Shade

V. Light LightMedium Dark

Very dark

• Hue

Green Yellow

Brown

Black



Oil Shows DescriptionB. Under UV Light

• Intensity

No florescence

Faint

Dull

bright



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



C. Cuts & D. Residual ring

• Stream cut: Immediate

Fast

Slow

• DiscolorationVery slow

Slow

Fast

• Crush cut

Poor

Fair

Good

• Allow the solvent toevaporate,

describe the

fluorescence of thering as well as the

color of the ring in

the day light.

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Deskripsi sample geologi

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