12 Questions
What does the term 'glacial till' refer to?
Mixture of different sediment sizes from rock flour to large blocks
Which factor determines whether sediments are well sorted or poorly sorted in flowing water?
Energy of currents and waves
What is the significance of grain size in sediment transport?
Grain size affects the ability of the fluid to entrain and transport sediment
Which forces act on a sediment grain in moving fluid according to the text?
Gravity, Lift, Drag, Friction, and Electrostatic forces
What principle does Stoke's Law of Settling relate to?
Principle of small grain velocity
What determines the balance between entraining and transporting sediment in channel fluids?
The balance between gravitational and drag forces
What is the final conversion of sediment into rock known as?
Diagenesis
Which agent is responsible for transporting very large blocks in detrital sediment transport?
Ice
What type of rock results from the accumulation of organic deposits?
Sedimentary rock
What major group of sediments are residual deposits that stay in place known as?
Terrigenous
Which process enables the interpretation of sedimentary structures preserved in ancient rocks?
Understanding transport and deposition processes
What key principle makes understanding transport and deposition processes vital for studying sedimentary rocks?
The present is the key to the past
Study Notes
Sediment Transport and Movement
- Glacial till is a mixture of different sizes of sediments, ranging from rock flour to large blocks.
Sediments and Transport Agents
- Water: fine to coarse sediments, depending on the energy of currents and waves; sediments can be well-sorted to poorly sorted, with sorting improving with increased energy and time.
- Wind: very fine to fine sediments, very well sorted.
Principles of Sediment Transport
- The ability of a channel fluid to entrain and transport sediment depends on the balance between:
- Gravitational forces acting to settle particles on the bed.
- Drag forces that act to suspend particles in the flow or push them along downstream.
- The submerged weight of a grain acts to hold it on the bed, while fluid lift and drag forces act to lift, roll, and slide the grain along the bed.
Grain Size and Its Significance
- Grain size affects movement during bedload transport.
Forces Acting on a Sediment Grain
- Lift
- Fluid Drag
- Friction
- Electrostatic
- Gravity
Sedimentary Rocks and Source Rocks
- Source rocks: Igneous, Metamorphic, Sedimentary; unaffected material that remains in place as residual deposits.
- Sedimentary rocks: Fragmental deposits, Chemical deposits, Organic deposits; formed through uplift, exposure, weathering, and collection.
Sediment Erosion, Transport, and Deposition
- governed by physical laws and physical agents such as wind, water, ice, and gravity.
- Transport and deposition of sediment occur through:
- Solution
- Saltation
- Suspension
- Settling out of particulate material
- Chemical/organic precipitation
- Final conversion to rock during burial: Diagenesis.
Importance of Studying Sediment Transport and Deposition
- Understanding transport and deposition processes enables the interpretation of sedimentary structures preserved in ancient rocks.
- The present is the key to the past.
Agents of Detrital Sediment Transport
- ICE: up to very large blocks, very poor sorting.
Test your knowledge on sediment transport, deposition, and sedimentary rocks. Topics include source rocks, terrigenous materials, major groups of sediments, and diagenesis.
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