Carbonate Petrography
Carbonate petrography is the study of limestones, dolomites and associated deposits under optical or electron microscopes greatly enhances field studies or core observations and can provide a frame of reference for geochemical studies.
25 strangest Geologic Formations on Earth
The strangest formations on Earth.
What causes Earthquake?
Of these various reasons, faulting related to plate movements is by far the most significant. In other words, most earthquakes are due to slip on faults.
The Geologic Column
As stated earlier, no one locality on Earth provides a complete record of our planet’s history, because stratigraphic columns can contain unconformities. But by correlating rocks from locality to locality at millions of places around the world, geologists have pieced together a composite stratigraphic column, called the geologic column, that represents the entirety of Earth history.
Folds and Foliations
Geometry of Folds Imagine a carpet lying flat on the floor. Push on one end of the carpet, and it will wrinkle or contort into a series of wavelike curves. Stresses developed during mountain building can similarly warp or bend bedding and foliation (or other planar features) in rock. The result a curve in the shape of a rock layer is called a fold.
Plate Tectonics Concepts
PLATE TECTONICS CONCEPTS
.Wegener's Concept of Continental Drift: Polar Wandering
Weathering and erosion
Weathering processes
Physical weathering
Freeze-thaw action
Salt growth
Temperature changes
Chemical weathering
Solution
Hydrolysis
Oxidation
The products of weathering
Soil development
Erosion and transport
Erosion and transport under gravity
Downslope movement
Scree and talus cones
Erosion and transport by water
Erosion and transport by wind
Erosion and transport by ice
Paleocurrents indicators and its analysis
Paleocurrents
Palaeocurrent indicators
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Cross lamination |
- Cross-lamination is produced by ripples migrating in the direction of the flow of the current. The dip direction of the cross-laminae is measured.
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Cross bedding |
- Cross-bedding is formed by the migration of aeolian and subaqueous dunes and the direction of dip of the lee slope is approximately the direction of flow. The direction of dip of the cross-strata in cross-bedding is measured.
- Large-scale cross-bedding and cross-stratification formed by large bars in river channels and shallow marine settings, or the progradation of foresets of Gilbert-type deltas is an indicator of flow direction. The direction of dip of the cross-strata is measured. An exception is epsilon cross-stratification produced by point-bar accumulation,which lies perpendicular to flow direction.
Clast imbrication |
- Clast imbrication is formed when discoid gravel clasts become oriented in strong flows into a stable position with one of the two longer axes dipping upstream when viewed side-on. Note that this is opposite to the measured direction in cross stratification.
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Flute casts |
- Flute casts are local scours in the substrata generated by vortices within a flow. As the turbulent vortex forms it is carried along by the flow and lifted up, away from the basal surface to leave an asymmetric mark on the floor of the flow, with the steep edge on the upstream side. The direction along the axis of the scour away from the steep edge is measured.
- Primary current lineations on bedding planes are measured by determining the orientation of the lines of grains.
- Groove casts are elongate scours caused by the indentation of a particle carried within a flow that give the flow axis.
- Elongate clast orientation may provide information if needle-like minerals, elongate fossils such as belemnites, or pieces of wood show a parallel alignment in the flow.
- Channel and scour margins can be used as indicators because the cut bank of a channel lies parallel to the direction of flow.
Stromatolites
Measuring palaeocurrents
Presentation and analysis of directional data
Mass Flow
What is Mass flow?
Debris flows
Turbidity currents
Low- and medium-density turbidity currents
- Ta: This lowest part consists of poorly sorted, structureless sand: on the scoured base deposition occurs rapidly from suspension with reduced turbulence inhibiting the formation of bedforms.
- Tb: Laminated sand characterises this layer, the grain size is normally finer than in ‘a’ and the material is better sorted: the parallel laminae are generated by the separation of grains in upper flow regime transport.
- Tc: Cross-laminated medium to fine sand, sometimes with climbing ripple lamination, form the middle division of the Bouma sequence: these characteristics indicate moderate flow velocities within the ripple bedform stability field and high sedimentation rates. Convolute lamination can also occur in this division.
- Td: Fine sand and silt in this layer are the products of waning flow in the turbidity current: horizontal laminae may occur but the lamination is commonly less well defined than in the ‘b’ layer.
- Te: The top part of the turbidite consists of finegrained sediment of silt and clay grade: it is deposited from suspension after the turbidity current has come to rest and is therefore a hemipelagic deposit.