New clastic coasts

Clastic Coasts Part 2

Overview

  • Focuses on various coastal and sedimentary systems.

  • Emphasizes deposition processes and coastal morphologies.

Deposition Systems

Definition

  • Depositional system: Collection of process-related sedimentary facies assemblages, informed by geography.

  • Examples: Nearshore, deep marine, glacial, and fluvial depositional systems.

  • Importance: Modern systems help in interpreting ancient sedimentary records.

Marine Depositional Systems

Types

  • Wave-dominated coasts

  • Tide-dominated coasts

  • Fluvial-dominated coasts (deltas)

  • Carbonate reefs

  • Clastic shelves & platforms

  • Carbonate shelves & platforms

  • Deepwater fans

  • Pelagic abyssal plains

Clastic Depositional Systems

Types

  • Terrestrial

  • Transitional

  • Marine

  • Characteristics: Dominated by sedimentary structures like graded beds and facies represented by highstand, lowstand, etc.

  • Shows the interface between land and sea in dynamic environments.

Coastal Types

Coastal Morphology

  • Increasing tidal and wave power influences coastal types: strand plains, barrier islands, and deltaic formations.

  • Types defined by sediment supply and wave/tide influence.

Beach Systems

Characteristics

  • Sediments coarsen upward from marine shales.

  • Linear sand bodies formed by waves and tidal currents.

  • Various facies identified: well-sorted quartz arenites, offshore hummocky bedding, cut and fill structures.

  • Faunal distribution: marine at the base, terrestrial at the crest.

Vertical Stacking in Shoreline Sediments

Prograding Coastal Plain

  • Holistic view of sediment integration over time.

  • Influence of sea level changes on sedimentation patterns.

Coastal Systems and Features

Types

  • Coastal plain, sandstone, and mudstone formations.

  • Characteristics: burrows, planar beds indicative of environmental conditions, foreshore & delta front structures.

  • Combinations of terrestrial and marine influences observed in sequence.

Deltaic Systems

Characteristics

  • Form where rivers meet standing water, offering large sediment influx.

  • Features: mix of fluvial, tidal currents, and storm influences.

  • Typical delta types based on tidal range, wave climate, and basin characteristics.

Processes in Deltaic Systems

Key Influences

  • Inertia, friction and buoyancy determined by water density and sediment interaction.

  • Different deltaic forms arise based on the dominance of these processes leading to various depositional traits.

Lake Systems

Characteristics

  • Lakes as sediment traps influenced by terrestrial input, internal morphology, and climatic conditions.

  • Lake sediments typically show a varying character from clastics & organics to evaporites.

Glacial Systems

Features

  • Glacial systems indicate climatic extremes with clear sedimentological signatures.

  • Glacial deposits like till and stratified sequences reveal evidence of historical ice coverage and melting trends.

Aeolian Systems

Characteristics

  • Presence in deserts with notable dust, loess deposits, and dune formations.

  • Role of wind in the transport of sediments, shaping the landscape through processes of erosion and deposition.

Conclusion

  • Understanding sedimentary systems is crucial for reconstructing past environments and predicting geological behavior under varying climatic conditions.