GLS 381
SEDIMENTOLOGY: This is the scientific study of the classsification, origin and interpretation of sediments &sedimentary rock. it is concerned with the physical (texture, structure, mineralogy),chemical & biological (fossils) properties of sedimentary rocks and the process by which the properties are generated.
The properties provide much of the basis for interpreting paleoclimatology, paleogeography and paleo ecology. Sedimentary rocks and the fossils they contains are paticularly important because they provide significant information’s about earths past geography, climates, depositional environments, life forms and ocean composition. The fossils sedimentary rock also provide a means for determining the relative ages of sedimentary rocks.
DEFINITION OF TERMS
SEDIMENTS: They are loosed particulate materials which may be derived from the following
(a) Weathering and Erosion: of pre-existing rocks and is referred to as terrigenous or detrital/ Clastic sediments and are very rich in quartz
(b) Chemical or Biochemical process: That is produced from precipitation in lakes or oceans.
(c) Biological material: Accumulated remains of organisms which lived within the basin
SEDIMENTATION: This is a process of sediments accumulation
SEDIMENTARY ROCK: These are rocks found through a complex set of process that include
(i) weathering of source rocks
(ii) Erosion
(iii) Sediment transport
(iv) Depositional and buria diogenesis
They are composed of particules or grains which could be (a) Epiclastic particles which are derived by weathering of pre-existing rocks.
(b)Pyroclastic particles which are formed through explosive, volcanism.
Both (a) and (b) are termigenous particles and composed entirely of silica (siliclastic)
(c)Chemically and Biochemically formed particles which are produced by precipitation from water in lakes and oceans eg particles in lime stone
There are three main types of sedimentary Rocks
(I) Siliciclastic Sedimentary rocks: These made up of siliciclastic grains consist os silica eg sand stone, conglomerate, siltstone, claystone, mudstone e.t.c.
(II) Chemical / Biochemical Sedimentary rocks: lime stone cherts and others like evapurites
(III) Carbonaceous Sedimentary rocks: Contain subs tancial amount of organic materials
(IV) Sedimentary Process: These include the physical and chemical process that affects sedimentation and operates in sedimentary environment.
ORIGIN OF SEDIMENTS AND SEDIMENTARY ROCKS
The process of forming sediments and sedimentary rocks begins with weathering (physical disintegration and chemical decomposition of rocks that produces solid and dissolves chemical products). The solid products of weathering rocks fragments may accumulate to form salt. They may be removed eventually and transported to depositional basins (mass transport such as slumps, debris flow, mud flow are important agents in initial stages of transport of sediments from the weathering sites to valley flood.
Debris flow and mud flow are like flows compound of highly concentrated, poorly sorted mixture of sediments and water. Mud flows are compound mostly of mud size materials while debris flow contains a significant fraction of coarsen materials that may include clasts ranging to boulder size
Fluid flows process which includes moving water ice and wind moves sediments from valley floors to depositional basin at lower elevation. When transport process are no longer capable of moving sediments, deposition of sands, gravel ,mud takes place sub aerially e.g. in desert dume fields or subequeosly in river system,lakes or the marginal ocean sediments deposited at ocean margin maybe re-entrained and re-transported tens-hundreds of kilometers into deeper water by turbidity currents or other transport process. Sedimentary rocks made up of siliclsastic grains are siliclastic sedimentary rock
Weathering processes also release from the source rocks soluble constituents such as calcium, magnesium and silica that makes their way in surface water and ground water to lakes or oceans when the concentration of these chemical elements becomes sufficiently high, they are removed by chemical and biochemical processes to form limestone and other chemical and biochemical sedimentary rocks
Plant materials on land are partly broken down by chemical and microbial process to yield organic residue. Some organic residue are accumulated in soils, others are deposited in swampy environment to form peats or coal and still others may be transported along with weathering detritions flow depositional basins. Sedimentary rocks that contains substantial amount of organic materials are called carbonaceous sedimentary rocks.
TRANSPORT PROCESS: Particles transported by sediment gravity floods: sediments can be transported independently of fluids by the effects of gravity acting directly on the sediment. In this type of transport, fluids may play a role in reducing the internal friction and supporting grains but they are not primarily responsible for the down slope movement of sediments. Movement of sediments under the influence of gravity creates the flow and the flow stops when the sediment load is deposited. Gravity mass movement can be grouped into
(a) Gravity flow (Debris, mud flow and turbidity current)
(b) Rock fall which involves free fall of blocks or clasts from cliffs or steep slope
(c) Slides: these are en-mass movement of rocks or sediments owing to sheer failure that takes place accompanying internal deformation of mass movement.
In sedimentary gravity flows, internal deformation of the sedimentary mass is intense
DEBRIS FLOW AND MUD FLOW: They are sediments flows that behave as Bingham plastics to yield strength that must be covered before flow begins. They consist of poorly sorted mixture of particles which may be composed predominantly of mud size grains of fraction 5% by volume are Muddy Debris Flow. The grains in these mud bearing debris flows are supported in a matrix of mud and interstitial water has cohesive strength to prevent larger particles settling but not enough strength to prevent flood and flow that have matrix composed predominantly cohesive less sand and gravel are mud free debris.
DEBRIS OF FLUID FLOWS: Water and air responsible for most sediment transports by fluid flow. However, ice may account for local transport of volumes of sediments and particles of very large structures. Sediments entrainment are transported by various processes stop and deposition occurs when local wind condition changes sufficiently to cause decreased shear stress to the point that it no longer initiate and sustain sustain particles movement. Sediments deposited by fluid flow of water or wind are commonly characterized by layers of beds of various thickness, Scarcity of vertical grain size grading, grain size sorting ranging from poor to excellent depending on the depositional conditions and the presence of a variety of sedimentary structures such as cross beds, ripple mark and pebble imbrications that display direction features from which the direction of the ancient fluid flows can be determined.
SEDIMENT LOADS AND TRANSPORT PATHS: Once sediments has been eroded and put into motion, the transport path it takes during further sustained down current movement is a function of the setting velocity and turbulence. Under a given set of condition, the sediment load may consist entirely of very coarse particles, entirely of very fine particles of a mixture of coarse and fine particles. Coarse sediments such as sand and gravel moves on or very close to the bed during transport and is considered to constitute the bed load finer –material carried higher up in the main flow above beds which makes suspended load
BED LOAD TRANSPORT: Particles larger than sand size are commonly transported as part of the bed load in essentially contact with the bed. This type of transport called traction transport may include rolling of large elongated grains, sliding of grains over or past each other.
SALTATION: This is a type of bed load transport in which grains particularly sand size grains tends to move in intermediate contact with the beds. Saltation transport may be thought of as intermediate between tranctions, transport and suspension transport.
SUSPENDED LOAD TRANSPORT: Particles that do not settle reading to the bottom in a fluid are said to be hold on suspension. A particle of clay size settles very slowly and will remain in suspension for many hours even in standing water. A large grain settles faster than smaller ones those with with high specific gravity more rapidly than light ones. Spherical particles likewise faster than irregular ones of equal size because they offer less frictional resistance. In moving water. Turbulence is an additional faction tending to keep sediments in suspension. In linear flow, particles of sediments settle as readily as still water but in turbulence food they are given repeated upward boost that regards their settling.
THE EFFECTS OF STREAM TRANSPORT ON SEDIMENTS: During transportation, particles of sediments are modified by many factors. A man kuenen in 1956 recognized 7 distinct processes that operates to shape particles and reduce them in size.Thet include (1)splitting (2)Crushing (3)Chipping (4)Cracking (5)Grinding (6)chemical attacks involving rock decay and solution (7)Sand blasting
TRANSPORTATION IN THE SEA: Currents in the sea are generated by winds (Drift current),by tides (tidal currents), and by difference in specific gravity (Density current) e.g. turbidity current waves plays a very important rule in the movement of sediments on the shallow sea floor since each gives a lift as it passes.
TRANSPORT BY WIND: Wind is a powerful agent of transportation especially in the arid region but its effect on loose sediments differs in important respect from that of flowing waters. The difference stems from the great difference in density and viscosity between air and water are far smaller by water and particles of sediments settles more rapidly in air than in water. On the other hand, the velocity of wind may greatly exceed that of current in water and it common change abruptly. Whereas a current of water loosing velocity drops progressively finer and finer particles so that the resultant sedimentary deposit’s, grades laterally from coarse to fine, ordinarily without abrupt change, the wind tend to select sand grains of a limited size range to concentrate them to ridges or dunes meanwhile lifting the finer particles into suspension and scattering them for and wide as dust.
TRANSPORTATION BY ICE: Sediments are transported by glaciers and by floating ice. in either case, it comes and dropped without sorting or size grading and the resulting deposits are unstratified. The very poor sorted sediments with coarse clasts is deposited as till while the movement of sorted finer grains sediments is deposited as out wash.
CHEMICAL TRANSPOTATION: The ions and molecules that are produced by weathering either react to yield less soluble compounds that remain in the soil or they become part of the ground of surface water solution. Migration of these aqueous solution results in transportation of dissolved sediment load. As they migrate, particularly if they do so as ground water, the solution may be diluted, concentrated or altered in chemistry due to reaction with the rock through which they pass. The water with the dissolve load that made it to seas and lakes mixed there with resident water yielding their chemical load through (a) Digenetic sediment-water reaction (b) In organic precipitation (c) biochemical precipitation
FACTORS THAT CONTROL THE PRECIPITATION: Includes (a) THE REDOX POTENTIAL (Eh): which is the measure of ability of a solution to produce oxidation whereas negative values indicate reduction (b) THE PH OF THE WATER: Which is the negative logarithm of the hydrogen ion – concentration of the solution.
BIOLOGICAL PROCESSES: 1. Secretion of calcium carbonate (Caco3) skeleton by organisms algae precipitates calcium carbonate skeleton as part of metabolic process. The skeleton may be calcite or Aragonite (Both posses the same chemical composition but different crystal content).2 Degradation of calcium carbonate skeleton into skeletal debris: Lime sands and muds. Some sponges, algae, fungi, worms, echinoids, gastropods, pelecypods bores into cancerous cords thereby disintegrating them into sand size or mud size particles (3)Trapping and Baffling of sedimentary particles by organisms. Filamentous blue-green algae secrets muscle agenous mats which traps and binds fine grained carbonate particles (lime muds) in layers of mats –example Stromatolite. (4) BURROWING: Simple hole made in sediments into sedimentary rocks. Even after sediments reaches its final resting place it may still undergo some important changes during its transformation into rocks. The digenesis’ embraces all the changes that results from sedimentary process but excluding metamorphosis. The processes are as follows 1. Compaction 2. Cementation 3.chemical alteration 4. Rework of sediments by organism 5.Recrystallisation
THE CONCEPT OF FLOW REGIME: The relationship of unidirectional current flood is summarized below
The succession of bed- form that develop during unidirectional flood of sandy sediments (0.25-0.7mm) in shallow water as flood velocity increases. Ripples are the smallest bed form ranging in length from about 5.20cm and in height from about 0.5 -3cm. Thus, they have a ripple index (ratio of ripple height) ranging from about 8 for coarse sand to 20 for fine sand. They form in sediment ranging in size from silt (0.06mm) to sand as coarse as 0.7mm. Dunes are used for larger bed forms (larger than ripples). They are similar in general appearance to ripples except for size they form at higher flow velocities in sediment ranging in grain size from fine sand to gravel. The ripple index of dune ranges from about 5 in finer sand to 50 in coarser sediments. During the formation of ripples and dunes, either the water surface over large scale ripples and large swirls that rise to the surface. The hydraulic condition that generates these beds form and out of phase waves distinguishes what is called lower flow Regime. With further increase in flow velocity, dunes are destroyed and gives way to an upper flow regime stage of flow, sheet like rapid flow of water takes a place which generates surface water waves that are in phase with the bed forms. It distinguishes the upper flow regime owing to the very rapid water flow, intense sediments transport takes place over an initially relatively flat bed during what is referred to as the plane – bed stage of flow plane-bed stage of flow. Plane-bed flow gives rise to internal planer lamination in which individual laminae range in thickness from a few millimeters to a few centimeters.
SEDIMENTARY STRUCTURES: These are large scales features of sedimentary rocks such as bedding units, ripple marks, mud cracks that are best studied in the field. They are generated by a variety of a sedimentary process including fluid flows, sediments, gravity flows, soft sediment deformation and biogenic activities of the organisms. Because they reflect environmental conditions that prevailed at, or shortly after the time of deposition, they are of special interest to geologist as a tool for interpreting such aspect of ancient sedimentary environment as sediments transport mechanism, paleo-current, flow directions, relative water depth, and relative current velocity. Some sedimentary structures can also be used to identify the top and bottom of beds and thus to determine if sedimentary sequences are in depositional stratigraphic order or have been overturned by tectonic forces. Sedimentary structures are particularly abundant in siliciclastic sedimentary rocks but they occur in non-siliciclastic sedimentary rocks such as lime stone and evaporites CLASSIFICATION OF SEDIMENTARY STRUCTURES: (1) STRATIFICATION AND BED FORMS: (A) Planar bedding and lamination (i) Laminated bedding (ii) Graded bedding (iii) massive (structure less) bedding (B) Bed forms (i) Ripples (ii) Dunes (iii) Anti Dunes (C) cross-stratification (i) cross-bedding (ii) Ripple cross lamination (iii) lenticular bedding (iv)Hummocky- cross stratification (D)Irregular stratification (i)Con volute bedding and lamination (ii) Flame structure (iii) Ball and pillow structure (iv) Syn sedimentary fold and faults (v)Dish and pillar structure or channels etc. (2)BEDDING-PLANE MARKINGS (a) Groove casts, Flute casts, Load casts, tracks trails burrows, mud cracks, pits e.t.c.
ORIGIN OF BEDDING: individual beds are produced under essentially constant physical, chemical or biological conditions. The true bedding planes or bounding surfaces between beds represents period of non-deposition, erosion or changes to completely different depositional conditions.
ORIGIN OF LAMINATION: Parallel laminae are produced by less severe or shorter lived fluctuations in sedimentation conditions than those that generate beds. They results from changing depositional conditions that cause variation in (a) Grain size, (b)Content of clay and organic material (c) Mineral composition (d) micro fossil content of sediments. (ii) GRADED BLEEDING: They are sedimentation units characterized by distinct vertical gradations in grain size. They range in thickness from a few centimeters to a few meters or more and commonly have sharp basal contacts. They are commonly devoid of internal laminations beds that shows gradation from coarser particles at the base to finer particles at the top are said to have normal grading. (iii) MASSIVE (STRUCTURELESS) BEDDING: The term massive bedding is used to describe beds that appear to be homogenous and lacking internal structure. (B)I CROSS –BEDDING: Forms primarily by migration of ripples or and dunes in water or air. Cross beds commonly occurs in sets. Cross bedding in sets-less than 5cm thick is called small-scale cross-bedding. The sets thicken than 5cm to large scale cross bedding. Cross beds are divided into two principal types on the basis of overall geometry and the nature of the banding surfaces of the cross-bedded unit. The two principal types of cross-beds are (A) TABULAR CROSS-BEDDING: They are planer bounding surfaces and are formed mainly by the migration of large scale, straight-crested ripples and dunes; thus, it forms during lower flow regime conditions. (B) TROUGH CROSS-BEDDING: One rounding both bounding surfaces a curved. They can originate both by migration of large scale, trough-shaped dunes. Cross-bedding is one of the most useful sedimentary structures of determining paleo-current directions (ii) RIPPLE CROSS-LAMINATION: They form when deposition takes place very rapidly during migration of current or wave ripples. The formation of ripple cross-lamination appears to require abundance of sediments, especially sediments in suspension, which quickly bums and preserves original rippled layers.
GLS 381
SEDIMENTOLOGY: This is the scientific study of the classsification, origin and interpretation of sediments &sedimentary rock. it is concerned with the physical (texture, structure, mineralogy),chemical & biological (fossils) properties of sedimentary rocks and the process by which the properties are generated.
The properties provide much of the basis for interpreting paleoclimatology, paleogeography and paleo ecology. Sedimentary rocks and the fossils they contains are paticularly important because they provide significant information’s about earths past geography, climates, depositional environments, life forms and ocean composition. The fossils sedimentary rock also provide a means for determining the relative ages of sedimentary rocks.
DEFINITION OF TERMS
SEDIMENTS: They are loosed particulate materials which may be derived from the following
(a) Weathering and Erosion: of pre-existing rocks and is referred to as terrigenous or detrital/ Clastic sediments and are very rich in quartz
(b) Chemical or Biochemical process: That is produced from precipitation in lakes or oceans.
(c) Biological material: Accumulated remains of organisms which lived within the basin
SEDIMENTATION: This is a process of sediments accumulation
SEDIMENTARY ROCK: These are rocks found through a complex set of process that include
(i) weathering of source rocks
(ii) Erosion
(iii) Sediment transport
(iv) Depositional and buria diogenesis
They are composed of particules or grains which could be (a) Epiclastic particles which are derived by weathering of pre-existing rocks.
(b)Pyroclastic particles which are formed through explosive, volcanism.
Both (a) and (b) are termigenous particles and composed entirely of silica (siliclastic)
(c)Chemically and Biochemically formed particles which are produced by precipitation from water in lakes and oceans eg particles in lime stone
There are three main types of sedimentary Rocks
(I) Siliciclastic Sedimentary rocks: These made up of siliciclastic grains consist os silica eg sand stone, conglomerate, siltstone, claystone, mudstone e.t.c.
(II) Chemical / Biochemical Sedimentary rocks: lime stone cherts and others like evapurites
(III) Carbonaceous Sedimentary rocks: Contain subs tancial amount of organic materials
(IV) Sedimentary Process: These include the physical and chemical process that affects sedimentation and operates in sedimentary environment.
ORIGIN OF SEDIMENTS AND SEDIMENTARY ROCKS
The process of forming sediments and sedimentary rocks begins with weathering (physical disintegration and chemical decomposition of rocks that produces solid and dissolves chemical products). The solid products of weathering rocks fragments may accumulate to form salt. They may be removed eventually and transported to depositional basins (mass transport such as slumps, debris flow, mud flow are important agents in initial stages of transport of sediments from the weathering sites to valley flood.
Debris flow and mud flow are like flows compound of highly concentrated, poorly sorted mixture of sediments and water. Mud flows are compound mostly of mud size materials while debris flow contains a significant fraction of coarsen materials that may include clasts ranging to boulder size
Fluid flows process which includes moving water ice and wind moves sediments from valley floors to depositional basin at lower elevation. When transport process are no longer capable of moving sediments, deposition of sands, gravel ,mud takes place sub aerially e.g. in desert dume fields or subequeosly in river system,lakes or the marginal ocean sediments deposited at ocean margin maybe re-entrained and re-transported tens-hundreds of kilometers into deeper water by turbidity currents or other transport process. Sedimentary rocks made up of siliclsastic grains are siliclastic sedimentary rock
Weathering processes also release from the source rocks soluble constituents such as calcium, magnesium and silica that makes their way in surface water and ground water to lakes or oceans when the concentration of these chemical elements becomes sufficiently high, they are removed by chemical and biochemical processes to form limestone and other chemical and biochemical sedimentary rocks
Plant materials on land are partly broken down by chemical and microbial process to yield organic residue. Some organic residue are accumulated in soils, others are deposited in swampy environment to form peats or coal and still others may be transported along with weathering detritions flow depositional basins. Sedimentary rocks that contains substantial amount of organic materials are called carbonaceous sedimentary rocks.
TRANSPORT PROCESS: Particles transported by sediment gravity floods: sediments can be transported independently of fluids by the effects of gravity acting directly on the sediment. In this type of transport, fluids may play a role in reducing the internal friction and supporting grains but they are not primarily responsible for the down slope movement of sediments. Movement of sediments under the influence of gravity creates the flow and the flow stops when the sediment load is deposited. Gravity mass movement can be grouped into
(a) Gravity flow (Debris, mud flow and turbidity current)
(b) Rock fall which involves free fall of blocks or clasts from cliffs or steep slope
(c) Slides: these are en-mass movement of rocks or sediments owing to sheer failure that takes place accompanying internal deformation of mass movement.
In sedimentary gravity flows, internal deformation of the sedimentary mass is intense
DEBRIS FLOW AND MUD FLOW: They are sediments flows that behave as Bingham plastics to yield strength that must be covered before flow begins. They consist of poorly sorted mixture of particles which may be composed predominantly of mud size grains of fraction 5% by volume are Muddy Debris Flow. The grains in these mud bearing debris flows are supported in a matrix of mud and interstitial water has cohesive strength to prevent larger particles settling but not enough strength to prevent flood and flow that have matrix composed predominantly cohesive less sand and gravel are mud free debris.
DEBRIS OF FLUID FLOWS: Water and air responsible for most sediment transports by fluid flow. However, ice may account for local transport of volumes of sediments and particles of very large structures. Sediments entrainment are transported by various processes stop and deposition occurs when local wind condition changes sufficiently to cause decreased shear stress to the point that it no longer initiate and sustain sustain particles movement. Sediments deposited by fluid flow of water or wind are commonly characterized by layers of beds of various thickness, Scarcity of vertical grain size grading, grain size sorting ranging from poor to excellent depending on the depositional conditions and the presence of a variety of sedimentary structures such as cross beds, ripple mark and pebble imbrications that display direction features from which the direction of the ancient fluid flows can be determined.
SEDIMENT LOADS AND TRANSPORT PATHS: Once sediments has been eroded and put into motion, the transport path it takes during further sustained down current movement is a function of the setting velocity and turbulence. Under a given set of condition, the sediment load may consist entirely of very coarse particles, entirely of very fine particles of a mixture of coarse and fine particles. Coarse sediments such as sand and gravel moves on or very close to the bed during transport and is considered to constitute the bed load finer –material carried higher up in the main flow above beds which makes suspended load
BED LOAD TRANSPORT: Particles larger than sand size are commonly transported as part of the bed load in essentially contact with the bed. This type of transport called traction transport may include rolling of large elongated grains, sliding of grains over or past each other.
SALTATION: This is a type of bed load transport in which grains particularly sand size grains tends to move in intermediate contact with the beds. Saltation transport may be thought of as intermediate between tranctions, transport and suspension transport.
SUSPENDED LOAD TRANSPORT: Particles that do not settle reading to the bottom in a fluid are said to be hold on suspension. A particle of clay size settles very slowly and will remain in suspension for many hours even in standing water. A large grain settles faster than smaller ones those with with high specific gravity more rapidly than light ones. Spherical particles likewise faster than irregular ones of equal size because they offer less frictional resistance. In moving water. Turbulence is an additional faction tending to keep sediments in suspension. In linear flow, particles of sediments settle as readily as still water but in turbulence food they are given repeated upward boost that regards their settling.
THE EFFECTS OF STREAM TRANSPORT ON SEDIMENTS: During transportation, particles of sediments are modified by many factors. A man kuenen in 1956 recognized 7 distinct processes that operates to shape particles and reduce them in size.Thet include (1)splitting (2)Crushing (3)Chipping (4)Cracking (5)Grinding (6)chemical attacks involving rock decay and solution (7)Sand blasting
TRANSPORTATION IN THE SEA: Currents in the sea are generated by winds (Drift current),by tides (tidal currents), and by difference in specific gravity (Density current) e.g. turbidity current waves plays a very important rule in the movement of sediments on the shallow sea floor since each gives a lift as it passes.
TRANSPORT BY WIND: Wind is a powerful agent of transportation especially in the arid region but its effect on loose sediments differs in important respect from that of flowing waters. The difference stems from the great difference in density and viscosity between air and water are far smaller by water and particles of sediments settles more rapidly in air than in water. On the other hand, the velocity of wind may greatly exceed that of current in water and it common change abruptly. Whereas a current of water loosing velocity drops progressively finer and finer particles so that the resultant sedimentary deposit’s, grades laterally from coarse to fine, ordinarily without abrupt change, the wind tend to select sand grains of a limited size range to concentrate them to ridges or dunes meanwhile lifting the finer particles into suspension and scattering them for and wide as dust.
TRANSPORTATION BY ICE: Sediments are transported by glaciers and by floating ice. in either case, it comes and dropped without sorting or size grading and the resulting deposits are unstratified. The very poor sorted sediments with coarse clasts is deposited as till while the movement of sorted finer grains sediments is deposited as out wash.
CHEMICAL TRANSPOTATION: The ions and molecules that are produced by weathering either react to yield less soluble compounds that remain in the soil or they become part of the ground of surface water solution. Migration of these aqueous solution results in transportation of dissolved sediment load. As they migrate, particularly if they do so as ground water, the solution may be diluted, concentrated or altered in chemistry due to reaction with the rock through which they pass. The water with the dissolve load that made it to seas and lakes mixed there with resident water yielding their chemical load through (a) Digenetic sediment-water reaction (b) In organic precipitation (c) biochemical precipitation
FACTORS THAT CONTROL THE PRECIPITATION: Includes (a) THE REDOX POTENTIAL (Eh): which is the measure of ability of a solution to produce oxidation whereas negative values indicate reduction (b) THE PH OF THE WATER: Which is the negative logarithm of the hydrogen ion – concentration of the solution.
BIOLOGICAL PROCESSES: 1. Secretion of calcium carbonate (Caco3) skeleton by organisms algae precipitates calcium carbonate skeleton as part of metabolic process. The skeleton may be calcite or Aragonite (Both posses the same chemical composition but different crystal content).2 Degradation of calcium carbonate skeleton into skeletal debris: Lime sands and muds. Some sponges, algae, fungi, worms, echinoids, gastropods, pelecypods bores into cancerous cords thereby disintegrating them into sand size or mud size particles (3)Trapping and Baffling of sedimentary particles by organisms. Filamentous blue-green algae secrets muscle agenous mats which traps and binds fine grained carbonate particles (lime muds) in layers of mats –example Stromatolite. (4) BURROWING: Simple hole made in sediments into sedimentary rocks. Even after sediments reaches its final resting place it may still undergo some important changes during its transformation into rocks. The digenesis’ embraces all the changes that results from sedimentary process but excluding metamorphosis. The processes are as follows 1. Compaction 2. Cementation 3.chemical alteration 4. Rework of sediments by organism 5.Recrystallisation
THE CONCEPT OF FLOW REGIME: The relationship of unidirectional current flood is summarized below
