What Is Lithology In Geography

D Procedures For Establishing Lithostratigraphic Units

1. Stratotypes and type localities as standard of definition

Each formal lithostratigraphic unit should have a clear and precise definition or characterization.

The designation of a stratotype for a layered unit or a type locality for a nonlayered unit is essential.

Designation of auxiliary reference sections or additional type localities may be used to supplement the definition of a lithostratigraphic unit. Where a complete section of a unit does not crop out in an area, the lower and upper boundary-stratotypes at specific sections are designated.

2. BoundariesBoundaries of lithostratigraphic units are placed at positions of lithologic change or arbitrarily within zones of vertical or lateral lithologic gradation or intertonguing. In subsurface work, because of caving in drill holes, it is best to define lithostratigraphic boundaries at the highest occurrence of a particular rock type rather than at the lowest.

Boundaries of lithostratigraphic units commonly cut across time surfaces, across the limits of fossil ranges, and across the boundaries of any other kind of stratigraphic units.

3. Unconformities and hiatusesStratigraphic sequences of similar lithologic composition but separated by regional unconformities or major hiatuses should be mapped as separate lithostratigraphic units.

Where Do Glacial Erratics Come From

As a glacier or ice sheet moves, it can erode bedrock. The ice can then pick up, or entrain, the eroded rock. As the ice flows, it transports the bedrock debris in the direction of flow. The ice then deposited the entrained sediment once it begins to retreat.

Erratics can range from large boulders to smaller stones and pebbles. All erratics are of a different rock type. Glacial sediments often contain a range of rocks of different kinds, which can be used to reconstruct the provenance1, or source, of the sediment and therefore the direction of ice flow.

Rocks that are moved by the glacier but are of the same rock type are called glacially-transported rocks. All glacially-transported rocks and erratics tend to show evidence of that glacial transport, with scratches , rounded edges and polished faces.

Glacial erratics and glacially-transported rocks can be sourced from rocks falling onto the glacier, rocks being picked up and transported at the base of the glacier, and rocks plucked from valley sides. Rocks transported on the glacier surface are said to be supraglacial, whilst rocks transported at the base of the ice are subglacially transported.

E Procedures For Extending Lithostratigraphic Units

A lithostratigraphic unit and its boundaries are extended away from the type section or type locality only as far as the diagnostic lithologic properties on which the unit is based may be identified.

1. Use of indirect evidence for identification of units and their boundariesWhere lithologic identity is difficult to determine because of poor or no outcrops, a lithostratigraphic unit and its boundaries may be identified and correlated on the basis of indirect evidence: geomorphic expression, wire-line logs, seismic reflections, distinctive vegetation, etc.

2. Marker beds used as boundariesThe top or the base of a marker bed may be used as a boundary for a formal lithostratigraphic unit where the marker bed occurs at or near a recognizable vertical change in lithology.

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What Is The Difference Between Geology And Petrology

Geology is the study of the earth, although recently this has been extended to include other planets and moons. Petrology is the study of rocks, particularly their mineralogy. It is typically carried out by viewing thin sections under the microscope. … It is a word used to mean a description of a rock formation.

Factors Affecting The Rate Of Erosion

The biggest factor affecting coastal erosion is the strength of the waves breaking along the coastline. A waves strength is controlled by its fetch and the wind speed. Longer fetches & stronger winds create bigger, more powerful waves that have more erosive power. As waves approach a coastline they lose energy though because friction with the seabed increases. This means that the bathymetry of the ocean or sea bed also impacts the strength of waves.

Certain landforms further reduce waves erosive power. Beaches increase the distance a wave travels before it reaches the coastlines cliffs and so reduces its energy. Headlands refract waves around them, reducing their erosive power at one location while increasing it at another.

Weathering also plays a role in the rate of erosion by creating weaknesses in rocks that are exploited by the processes of erosion. Freeze-thaw weathering, for example, creates cracks in rocks, increasing the rocks susceptibility to hydraulic action.

As always, humans have an impact on coastal erosion. Human activities have a variety of complex effects on coastal erosion but most commonly the activities increase the strength of waves. One activity, dredging, is commonly carried out to improve shipping capacities but it reduces the amount of energy dissipated from incoming waves and so increases erosion.

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B4b Wave Erosion Processes

The importance of wave erosion processes and how they are influenced by wave type, size and lithology.

How these are influences by wave type, size and lithology

• They are most effective during high energy storm events with large destructive waves.
• However, even coastlines composed of soft, unconsolidated sediment , experience little erosion under normal conditions.
• Most erosion occurs in the winter, in high energy storms.
• It’s faster when the wind is blowing directly onshore
• It’s faster when the tide is high

The effect of erosion

• The boulder clay of the Holderness coast has retreated by 120 m in the last 100 years.
• The granite of Land’s End in Cornwall has retreated by only 10 cm in the last 100 years.

Controls Of Climate Topography Vegetation And Lithology On Drainage Density Extracted From High Resolution Topography Data

Controls on drainage density analyzed using lidar data.

Proposed dimensionless drainage density metric Ddd less dependent on resolution.

Correlation of Ddd and precipitation ve in semi-arid and +ve in humid environments.

Transition in correlation occurs at 1100 ± 100 mm/yr of mean annual precipitation.

Thick soil, high available water capacity, and dense vegetation at the transition.

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What Do Glacial Erratics Tell Us About Past Ice Sheets

The first thing erratics can tell us about past ice sheets is the direction of ice movement. If you find an erratic with a distinctive lithology, you can trace it back to the location where the distinctive bedrock is found.

A good example of this indicator lithology in England is the Shap Granite from Cumbria. Boulders of Shap Granite are found throughout Cumbria, County Durham, North Yorkshire and as far southeast as Bridlington on the Yorkshire Coast2,3. The example shown in the figure below is from Goldsborough Carr in County Durham, which is 40 km east of the Shap Granite.

Erratics can tell us when the ice sheet retreated, by cosmogenic dating of the boulder. Assuming the boulder was eroded at the base of the glacier, the exposure age given by the cosmogenic dating will tell us when the boulder was deposited by the retreating glacier4. The boulder of Shap Granite in the figure above was deposited by the retreating Eden-Stainmore Ice Stream approximately 19,750 years ago5.

F Naming Of Lithostratigraphic Units

1. GeneralThe name of lithostratigraphic units follows the general rules for naming stratigraphic units .

In the case of lithostratigraphic units, a simple lithologic term indicating its dominant rock type may be used instead of the unit-term indicating its rank .

However, the use of the unit-term is preferable and the use of both the lithologic term and the unit-term should be discouraged.

The terms “lower”, “middle”, and “upper” should not be used for formal subdivisions of lithostratigraphic units.

2. Geographic component of nameSee section 3.B.3.a.

In the case of lateral changes in lithologic composition, change in the geographic term is desirable for important regional changes, but the indiscriminate proposal of new names for minor lithologic variations is undesirable.

3. Lithologic component of nameIf a lithologic term is used in the name of a lithostratigraphic unit it should be a simple, generally accepted term that indicates the predominant lithology of the unit.**

Compound, combined or lithogenetic terms should not be used.

4. Some special aspects of igneous and metamorphic rocksStratified volcanic rocks and bodies of metamorphic rocks that can be recognized as of sedimentary and/or extrusive volcanic origin can be treated as sedimentary lithostratigraphic units.

Also appropriate is the use of the terms “complex”, “melange”, and “ophiolite”.

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What Is A Polje In Geography

poljepolje

Polje, , elongated basin having a flat floor and steep walls it is formed by the coalescence of several sinkholes.

Subsequently, question is, what are karst features? Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. Subterranean drainage may limit surface water, with few to no rivers or lakes.

Herein, what is Uvala in geography?

Uvala is originally a local toponym used by people in some regions in Slovenia, Croatia, Bosnia and Herzegovina, Montenegro and Serbia. In geosciences it denotes a closed karst depression, a terrain form usually of elongated or compound structure and of larger size than that of sinkholes .

What is karst window?

A karst window occurs where the aquifer is directly exposed to the surface. Because of this, there is no filtration by soil or bedrock for water that moves over the ground and into this ‘window‘.

What Is The Difference Between Lithology And Geology

The main difference between lithology and geology is that lithology describes the properties of a unit of rocks whereas geology describes the occurrence and changing of rock on Earths crust over a long time period.

Lithology and geology are branches of Earth sciences that are important in describing the properties, occurrence and changes of rocks on the Earths crust. Therefore, these are sciences related to solid Earth.

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Neutron And Density Logs Combined

Neutron and density logs each react to both lithology and porosity, so by analyzing the two logs together, one can begin to distinguish lithology from porosity. Neutron and density logs, together with a caliper measurement recorded by the density tool and a natural gamma ray log, are commonly run as a combination. This is the most powerful of the commonly available log suites for general purpose determination of lithology.

Where Can You Find Glacial Erratics In The Uk

There are many famous examples of glacial erratics in the UK. These erratics have captured the imagination of amateur and professional geologists for centuries. In 1928, the Yorkshire Geological Society published the work of Frederic Harmer7. This map collated the studies of the Yorkshire Boulder Committee and many similar groups.

As you can see below, the map shows the huge density of glacial erratics in the UK. The Norber erratics in the Yorkshire Dales, near Austwick, Settle, are famous and scenic examples of erratics. More examples of erratics are the Great Stone of Fourstones on the Lancashire/Yorkshire border, and Cloughmore in County Down, Northern Ireland.

Scotland is full of glacial erratics thanks to its diverse bedrock geology. We use these erratics to reconstruct the dynamics of the British-Irish Ice Sheet. The figure below shows Dubawnt-style dispersal trains in the Assynt region of Scotland. The outcrops of Torridonian Sandstone and the trains of dispersed erratics show that ice flowed towards the west-northwest. The constant width of the dispersal trains shows that the regional flow of ice was a constant velocity over this area8.

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A Nature Of Lithostratigraphic Units

Lithostratigraphic units are bodies of rocks, bedded or unbedded, that are defined and characterized on the basis of their lithologic properties and their stratigraphic relations. Lithostratigraphic units are the basic units of geologic mapping.

The relationship of lithostratigraphic units to other kinds of stratigraphic units is discussed in Chapter 10.

What Are The Differences Between Geology Petrology And Lithology

What differences are there between geology, petrology, and lithology?

If I were to get into any of those fields, what exactly would I be studying?

Also, are petrology and lithology just branches of geology?

The basic differences are:

Geology

Petrology

Lithology

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C Kinds Of Lithostratigraphic Units

1. Formal lithostratigraphic unitsSee Table 1 and section 3.A.5.

The conventional hierarchy of formal lithostratigraphic terms is as follows:

• Group – two or more formations
• Formation – primary unit of lithostratigraphy
• Member – named lithologic subdivision of a formation
• Bed – named distinctive layer in a member or formation
• Flow -smallest distinctive layer in a volcanic sequence

The component units of any higher rank unit in the hierarchy need not be everywhere the same.

2. FormationThe primary formal unit of lithostratigraphic classification.

Formations are the only formal lithostratigraphic units into which the stratigraphic column everywhere should be divided completely on the basis of lithology.

The contrast in lithology between formations required to justify their establishment varies with the complexity of the geology of a region and the detail needed for geologic mapping and to work out its geologic history.

No formation is considered justifiable and useful that cannot be delineated at the scale of geologic mapping practiced in the region. The thickness of formations may range from less than a meter to several thousand meters.

3. MemberThe formal lithostratigraphic unit next in rank below a formation.

It possesses lithologic properties distinguishing it from adjacent parts of the formation.

No fixed standard is required for the extent and thickness of a member.

A formation need not be divided into members unless a useful purpose is thus served.

Cliff Profiles & Bedding Layers

Rocks tend to form in layers of different rock types known as beds. These beds are subjected to tectonic forces that tilt and deform them so they dip at an angle. The angle the beds dip at affects how they are eroded and the profile of the resulting cliffs.

Horizontal beds produce steep cliffs with notches where differential erosion has taken place. Near vertical beds also produce steep cliffs but differential erosion is less prevalent in these structures. Beds that dip seaward produce gentler cliffs but are less stable because loose material can slide down the bedding planes in . Landward dipping beds produce stabler & steeper cliffs.

An idealised horizontally bedded cliff. Its profile is steep but the softer rock has undergone differential erosion producing several notches.

A cliff with seaward dipping bedding planes. Loose material can slide down the bedding planes making the cliff unstable & dangerous.

A cliff with landward dipping bedding planes. Compared to cliffs with seaward dipping bedding planes, it is relatively steep and stable.

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What Is Lithostratigraphy

Bethan Davies cleaning a face for sedimentological logging in County Durham.

Lithostratigraphy is the classification of bodies of rock based on the observable lithological properties of the strata and their relative stratigraphic positions1. Stratigraphy includes information about processes, geographical distributions, and the palaeo-environment of past glaciers and glaciation. It involves an attempt to determine the chronological sequence of geological events over a wide area.

Lithofacies associations, landform-sediment assemblages, depositional processes, syndepositional tectonics, landsystems, and geochronology are combined in a hierarchical structure to form a stratigraphy, through which the history and patterns of past glaciations and their associated environments can be reconstructed and interpreted1,2.

Sedimentological approaches should be based upon the lithostratigraphic unit, which has distinctive lithological properties, should be capable of being mapped and is typically tabular3,4. The lithostratigraphic unit has a hierarchical system with the Group, Formation, Member and Bed sub-categories5, and each new mappable lithostratigraphic unit must be formally proposed with a stratotype, and described emphasising lithological properties1,3. A lithostratigraphic scheme therefore:

Spectral Gamma Ray Logs

In this enhancement to natural gamma ray logging, the energy levels of incoming gamma rays are counted in a series of energy windows, and an algorithm converts the energy spectrum to count rates for potassium , thorium , and uranium . Spectral gamma ray logs are most useful in identifying the following:

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Design Of Tunnels: 3 Considerations

Rocks may be broadly divided into two categories in relation to tunneling- consolidated and unconsolidated or soft ground. Geological characters that have a direct bearing on a tunnel project will differ almost in all details in these categories.

Only a brief account is given below:

Consolidated Rocks:

This group includes the massive igneous, sedimentary and metamorphic rocks that very often form major mountain ranges and sub-mountainous regions. Most tunnels in the mountains pass through these rocks.

Tunnel design, method of its excavation and stability are greatly influenced by following geological conditions:

1. Lithology,

1. Lithology:

The information regarding mineralogical composition, textures and structures of the rocks through which the proposed tunnel is to pass is of great importance in deciding:

The method of tunnelling,

The strength and extent of lining and, thus

The cost of the project.

Hard and Crystalline Rocks are the favourites with the tunnel engineers. These are excavated by using conventional rock blasting methods and also by tunnel boring machines of suitable strength. In the blasting method, full face or a convenient section of the face is selected for blasting up to a pre-selected depth during one shooting sequence.

Soft Rocks:

2. Geological Structures:

The design, stability and cost of tunnel depend not only on the type of rock but also on the structures developed in these rocks.

i. Dip and strike,

iii. Faulting and shear zones and

ii. Folding: