Sedimentary Structures Flashcards

Sedimentary Structures

• Grains in rocks are organized in specific patterns, defining sedimentary structures.
• Bedding refers to sedimentary beds that are deposited horizontally, with "up" indicating younger rock layers.

Key Sedimentary Features

• Graded Bed: Characterized by larger cobbles at the bottom and smaller grains at the top, often formed by flood events.
• Cross Beds: Result from wind erosion creating dunes; the direction of wind or dune formation is indicated as "up."
• Ripples: Formed in shallow beach water where waves cause sediment movement.

Environmental Indicators

• Mudcracks: Indications of drying conditions, preserved in the rock throughout geological history.
• Sedimentary Provenance: Describes the origin of sedimentary rocks and their source materials.

Sandstone Types

• Arenite: Composed predominantly of quartz, formed far from mountains but close to coastal regions.
• Arkose: Contains significant potassium feldspar, formed near coastal regions.
• Graywacke: Located close to mountains, this rock includes quartz, feldspar, and rock fragments.

Chemical Sedimentary Rocks

• Inorganic Precipitates: Formed when minerals precipitate from solution, leading to sedimentary beds; evaporites are specific deposits resulting from evaporation in lake basins.
• Organics: Reefs develop from limestone in deep water, as calcium carbonate is produced from the skeletal remains of marine life.

Sources of Energy Resources

• Oil is generated from the remains of diatoms and radiolarians, both types of plankton.
• Coal originates from decayed plant debris found in swamp-like environments.

Lithification Processes

• Compaction: Occurs as layers accumulate, causing the bottom layer to compress, which reduces the spaces between grains.
• Cementation: Involves the flow of water between grains, where ions precipitate to bond grains together.

Depositional Environments

• Fluvial: Environments related to rivers, resulting in conglomerate, sandstone, mudstone, and coal formations in floodplain and swamp areas.
• Deep Marine: Found in deep ocean settings, characterized by deposits like mudstone and chert from dead phytoplankton.
• Shallow Marine: Consists of environments such as beaches, lagoons, and reefs.

Sedimentary Basins and Tectonics

• Sedimentary basins form from the sinking of crust layers, with deposits maintaining consistent elevation.
• Rift Basin: Created when the crust stretches, thins, and sinks.
• Flexural Basin: Formed by downward flexing of the crust, allowing for sediment accumulation; often associated with mountain building.

Test your knowledge of sedimentary structures with these flashcards. Each card presents a term related to sedimentary geology, along with its definition, helping you understand the organization of grains in rocks and related concepts. Perfect for geology students looking to enhance their vocabulary and insights into sedimentary processes.