Continental and Marine Environments: A Comprehensive Guide

Continental Environments

Fluvial (River) Environments

• Stream/river channels
• Sand bars
• Levees
• Floodplains

Lacustrine (Lake) Environments

• Vary in depth, salinity, biological activity, and sediment
• Source sand and mud

Aeolian (Desert) Environments

• Little to no annual precipitation
• Low vegetation
• High wind
• Transport of sand grains
• Dunes contain well-sorted, well-rounded, and frosted (scratched during wind transport) sand grains sand and dust

Paludal (Swamp) Environments

• Area of anoxic (deoxygenated) water where plant material accumulates but cannot decompose (coal)
• Very low energy environment

Glacial Environments

• Glacial meltwater and sediment transport
• Sand, mud, gravel

Transitional Environments

Deltas

• Fan-shaped deposits of sediment
• Coarser sediment is commonly deposited near the river mouth, whereas finer particles are transported longer distances and deposited in deeper water
• Sand & mud

Tidal Flats

• Large flat areas periodically flooded and drained by the tides
• Fine sediments are trapped here when the tide goes out
• Sand & mud

Beaches

• Shaped by tides and wave energy
• The dominant sediment size is sand on shore, but gets finer out to sea
• Sand & gravel

Marine Environments

The Continental Shelf

• The submerged edge of the continent
• Flat and shallow, affected by waves, tides, and currents
• Sediment ranges in size from gravel to silt

Organic Carbonate Reefs

• Wave-resistant, mound-shaped structures that contain coral and other calcareous algae
• These structures are typically built up on the continental shelf

Continental Slope

• The relatively steep drop-off at the edge of the continental shelf

Continental Rise

• The base of the continental slope contains a thick accumulation of sediments

Abyssal Plain (Deep Sea)

• Basically flat and covered by very fine-grained sediment that settles from the overlying water column over time

Sedimentary Structures

Ripple Marks

• Symmetry of ripples indicates environment (symmetrical vs asymmetrical)

Mud Cracks

• Once was wet mud then dried out in the sun and preserved cracks

Stratification

• Sediments from distinct layers known as “strata”

Graded Bedding

• Forms when a sediment-laden current carrying sediments of varying sizes stops, heaviest ones settle first, than the smaller ones on top

Cross-Stratification

• Forms with ripples and dunes

Tool Marks/Flute Marks/Traicks/Trails/Burrows/Stromatolites (Cyanobacteria)