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 stated property 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 is distinguished and delimited on the basis of lithic characteristics and stratigraphic position.))

Nature of Lithostratigraphic Units Type section and locality. Independence from inferred 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 in lithostratigraphic 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 a clay which give it its plastic properties. They are hydrous aluminosilicates. Generally occur as minute, platy, rarely fibrous crystals. Some contain loosely bonded cations which can be 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 and pH. 3.Adjustment to major cations. 4.Development of Authigenic menerals. Early-Burial changes 1. 1.Continuation of 2 & Oxidation of carbonaceous material Continuation of compaction Probable initiation of concretions Start of primary cementation 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 and cementation. Replacement of aragonite by calcite; dolomitization.

Sedimentary Rock Types Rocks formed from material derived from pre-existing rocks by processes 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.Cryptocrystalline 3.Succrose Sediments without recognizable size at ordinary microscope: Descripe the morphology of the cutting.

Dunham Classification Depositional texture not recognized. Crystalline carbonate.

Depositional texture recognized Depositional texture recoginized. Original components bound together Boundstone.

Mud supported

Grain supported

Dunham Classification Depositional texture not recognisable Depositional texture recognisable Original components bound together during deposition Original components not bound together during deposition. Lacks mud and is grain supported Contain mud (particles<20m) Grain supported Mud supported > 10% grains < 10% grains Crystalline carbonate BoundstoneGrainstonePackstoneWackstoneMud 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 and cementation. Archi classification  matrix porosity I.Compact, dense, hard II.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  SpotyStreaked Shade  V. LightLight  MediumDark  Very dark Hue  Green  Yellow  Brown  Black

Oil Shows Description B. Under UV Light Intensity   No florescence   Faint   Dull   bright

Oil Shows Description B. Under UV light Distribution  Uniform Scattered  SpotyStreaked Shade  V. LightLight  MediumDark  Very dark Hue  Blue  white  Yellow, Orange  Gold  Brown

C. Cuts & D. Residual ring Stream cut:  Immediate  Fast  Slow Discoloration  Very slow  Slow  Fast Crush cut  Poor  Fair  Good Allow the solvent to evaporate, describe the fluorescence of the ring as well as the color of the ring in the day light.