Graded Bedding Definition Earth Science

By | April 24, 2021

Graded Bedding: An Insight into Earth's History

Graded bedding is a sedimentary structure characterized by a gradual change in the size and composition of sediment particles from the base to the top of a bed. It forms when a layer of sediment is deposited from a fluid, such as water or wind, that is carrying a mixture of particle sizes. As the fluid's velocity decreases, larger particles settle out first, followed by progressively smaller particles.

Formation of Graded Bedding

Graded bedding typically occurs in environments where the fluid flow is turbulent, such as in river channels or submarine currents. As the fluid moves, it entrains and transports sediment particles of various sizes. When the fluid's velocity decreases, typically due to a change in slope or a decrease in discharge, the heavier and larger particles settle out first, forming the base of the bed. Lighter and smaller particles remain suspended in the fluid and are deposited later, creating the upper portion of the bed.

Types of Graded Bedding

There are two main types of graded bedding:

  • Normal graded bedding: This type has a coarsening-upward sequence, where the particle size increases from the base to the top of the bed.
  • Reverse graded bedding: This type has a fining-upward sequence, where the particle size decreases from the base to the top of the bed.

Significance of Graded Bedding

Graded bedding provides valuable information about the depositional environment and the history of the sedimentary basin. It can indicate the direction of fluid flow, the velocity of the fluid, and the duration of deposition. Graded beds can also help geologists identify different sedimentary facies and correlate strata across different locations.

For example, normal graded bedding in a river deposit suggests that the flow was strong initially and gradually decreased over time. Reverse graded bedding in a marine deposit may indicate a sudden increase in the fluid's velocity, perhaps due to a storm or a turbidity current.

Examples of Graded Bedding

Graded bedding can be observed in various sedimentary environments, including:

  • River channels
  • Submarine currents
  • Turbidity currents
  • Lag deposits
  • Glacial tills

By studying graded bedding, geologists gain insights into the dynamic processes that shaped our planet's surface in the past, helping them better understand the evolution of sedimentary basins and the history of Earth's environments.


Graded Bedding Wikipedia

Graded Bedding Wikipedia

Graded Bedding

Graded Bedding

Graded Bedding

Graded Bedding

Sedimentary Structures Industry

Sedimentary Structures Industry Energy And Technology

Way Up Structures Historical Geology

Way Up Structures Historical Geology

Graded Bedding

Graded Bedding

Gradation Grading Springerlink

Gradation Grading Springerlink

Grading Graded Bedding Springerlink

Grading Graded Bedding Springerlink

Graded Bedding

Graded Bedding

Way Up Structures Historical Geology

Way Up Structures Historical Geology

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.