Geological Processes: Erosion, Sediment Transport, and Deposition

Major Geological Processes: Erosion, Transport, and Deposition

Erosion: Material Evacuation and Relief Modeling

Erosion is the evacuation of material by geological agents, resulting in the wear of reliefs and karst modeling.

Effects of Erosion

• Evacuation of Debris: Fragments of rocks or clasts produced by weathering.
• Modeling Land Surface Characteristics: Geological agents move rock clasts, producing specific relief forms.
• Peneplain Formation: Large, virtually flat areas resulting from extensive erosion.
• Redistribution of Continental Masses: Erosion, sediment transport, and subsequent deposit in sedimentary basins cause weight loss in mountainous areas.

Transport: Conveyance of Geological Materials

Transport is the conveyance of materials by geological agents.

Sedimentation: Accumulation in Basins

Sedimentation is the accumulation of materials in depressed areas of the Earth's surface, known as sedimentary basins.

Parameters Characterizing Sediment Transport

Energy

The capacity of an agent to mobilize sediments.

Selection

Related to energy; high-energy agents do not select clasts and carry different sizes.

Maturation

How the sediment has changed in composition, shape, and size during transport.

Forms of Sediment Transportation

Contact with the Bottom (Bedload)

The fluid is unable to maintain these clasts suspended, so they move along the bottom by: rolling, saltation, and drag.

Without Touching the Bottom (Suspended Load)

Thin clasts, attached to floating objects, are transported in: suspension, flotation, or dissolution.

Sedimentation: Accumulation of material transported by an agent; they may again be transported or permanently accumulated.

Areas Subject to Sedimentation Processes

Areas subject to erosion where deposited sediment may be re-transported. Zones in the process of Sag (Sedimentary Basins): Agents can accumulate thousands of meters of sediment thickness, which eventually form sedimentary rocks.

Sediment Accumulation and Sedimentary Structures

Accumulation Mechanisms

Decantation

The fall or precipitation of clasts at the bottom of the medium in which they were suspended.

Kinetic Accretion

Occurs when transported clasts face an obstacle that stops them, causing them to accumulate against each other.

Sedimentary Structures (Clast Arrangement)

Stratification

The arrangement of sediments in layers (strata) of some centimeters or a few meters thick.

Lamination

Layering of a few millimeters thick, occurring when sedimentation takes place in a low-energy stream.

Graded Settling (Graded Bedding)

Arrangement of clast size, with coarser material settling down and finer material above.

Cross-Lamination

Available in sheets that intersect each other when sedimentation occurs in the presence of currents.