Module 1- sedimentation/stratigraphy Flashcards
What is sedimentation?
separation of particles from a parent rock, to the consolidation of the particles into another rock
What is Stratigraphy?
branch of geology which deals with the formation, composition, sequence, and correlation of the stratified rocks within the Earth’s crust.
What are the 4 processes involves in sedimentation?
- Weathering
- Erosion & Transportation
- Deposition
- Lithification
What 2 categories is weathering broken into?
mechanical
chemical
What is weathering?
the mechanical and chemical alteration of Earth’s materials at or near the surface.
Erosion is what?
removes weathered materials from their place or origin by running water or wind.
What are the 4 example of mechanical weathering?
- Pressure release on unloading
- Thermal expansion and contraction (frost wedge)
- Growth of foreign crystals within a rock
- Plant growth
What is Frost wedging and when does it occur?
Frost wedging is a type of mechanical weathering.
It takes place when water seeps into cracks and expands as it freezes. Angular pieces of rock are pried loose by repeating freezing and thawing.
What is chemical weathering?
includes those processes by which rocks and minerals are decomposed by chemical alteration of the parent material.
What are important agents of chemical weathering?
- atmospheric gases
- Oxygen
- Water
- Acids
What is bowen’s reaction series?
the stability of minerals and their resistance to chemical weathering is opposite of their order of crytallization.
What are the most stable and least mineral?
Quartz and feldpsar
How are siliclastic sedimentary rocks primarily classified?
Grain size
What are the 5 siliclastic rocks?
- mudstone/shales
- Siltstones
- Sandstones
- Conglomerates
- Breccias
what are the 5 transport agents of sediments?
- gravity
- organisms
- wind
- ice
- water
What are the 2 transport load mechanisms and what do they transport?
- Bed load mechanisms (transports fine to coarse sand particles including saltation(bouncing) and creeping(rolling and sliding)
- Suspended load mechanisms (affect very fine sand and silt particles).
Why do current ripple marks form?
In respinse to flow in one direction, as in a stream channel.
How does a turbidity current flow and why?
downslope along the seafloor or lake bottom because it is denser than sediment free water.
When does deposition of graded bed take place?
Takes place when the turbidity current flow slows and deposits progressively smaller particles/
What is bioturbation?
Process whereby sediment is mixed by the movement of living organisms (eg. works burrowing).
What are the 8 depositional environments?
- Glaciers
- Alluvial
- Fluvial (streams, channels, network of streams)
- Marine (near shore-shelf, deep water)
- Eolian
- Deltaic
- Lacustrine
- Estuarine
What are the kinds of rivers classified under fluvial depositional environments?
- Braided rivers
- Anastomosing rivers
- Meandering rivers
What is an estuary?
an estuary is a semi-enclose coastal body of water along a coastline and is influenced by the tidal and wave action of the open sea.
What are the 4 forms of modern deltas?
- Original Delta (nile)
- River dominated delta (mississippi)
- Wave dominated delta (Rhone)
- Tide dominated (Ganges)
T of F: sediments usually become increasingly fine with distance from the coast?
TRUE
Where are silts and clays generally deposited?
in quieter, deeper water
Sand is limited to shallow water. How is affected?
By wave, tides, and storms.
What are 3 deep water deposits with no petroleum potential?
- Pelagic sediments
- Calcareous and silica ooze
- Fe and Mg concentrated deposits
