sedimentary environments pt. 2 (mod #9.2)

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fluvial systems

TERRESTRIAL ENVIRONMENTS:

Encompass sediments generated by riverine and gravity-flow

processes;

Subdivided to alluvial fan and river settings

alluvial fan, poorly sorted

TERRESTRIAL ENVIRONMENTS:

conical (fan) segment with convex-up cross section with high relief and steep slopes;

transition of mountains and plains;

_____-sorted mud to gravel-sized sediments forming conglomerate, breccia and sandstone;

high-energy environment

conglomerate, breccia, sandstone

TERRESTRIAL ENVIRONMENTS (FLUVIAL SYSTEMS):

in alluvial fans, there are poorly-sorted mud to gravel-sized sediments forming ______, ______, & _______

river

TERRESTRIAL ENVIRONMENTS (FLUVIAL SYSTEMS):

Elongated bodies of water that flow through channels

meandering channel, low

TERRESTRIAL ENVIRONMENTS (FLUVIAL SYSTEMS):

Single channel with thalweg (deepest);

____ gradient and high sinuosity (many curves);

deposition at point bars and erosion at cut banks

thalwegs

DEFINITIONS:

this is the line of lowest elevation connecting the deepest points along the length of a stream bed, river channel, or subterranean valley

braided river, low sinuosity

TERRESTRIAL ENVIRONMENTS (FLUVIAL SYSTEMS):

Multiple channels with ____ sinuosity with multiple thalwegs and bars;

Occurs in areas with irregular water regime and abundant sediment supply

Deposits composed of alternating lenses of coarse gravel and sand

Terraces

TERRESTRIAL ENVIRONMENTS (FLUVIAL SYSTEMS):

elevated areas at the sides of channels

Yazoo Tributary

TERRESTRIAL ENVIRONMENTS (FLUVIAL SYSTEMS):

tributary running along the main channel;

tributary that is forced to flow parallel to a larger, major river within the same floodplain for a long distance before finally joining it at a delayed confluence

• tributary - freshwater stream or river that flows into a larger stream, river, or lake instead of draining directly into an ocean

Natural Levees

TERRESTRIAL ENVIRONMENTS (FLUVIAL SYSTEMS):

accumulation of sediments along banks

Lacustrine Environment

TERRESTRIAL ENVIRONMENTS:

Landlocked body of standing, fresh and non-marine water with circular plan and lenticular section;

Low energy depositing fine sediments (shales, laminated mudstone, sandstone) with well preserved fossils and structures that coarse upward-outward

Varves

TERRESTRIAL ENVIRONMENTS (LACUSTRINE):

alternating dark and light-colored mud laminations

Aeolian Environment

TERRESTRIAL ENVIRONMENTS:

Dominated by wind erosion and deposition;

Occurs in arid regions & has wind erosion

• sandblasting, deflation

Sandblasting

AEOLIAN ENVIRONMENTS (WIND EROSION):

erosion from constant impact of grains carried by the wind

Deflation

AEOLIAN ENVIRONMENTS (WIND EROSION):

erosion of fine sediments, leaving coarser sediments to form desert pavements

Dunes

AEOLIAN ENVIRONMENTS:

wind deposited sands with windward gentler stoss side eroded and deposited to the steeper lee side

1. stoss

2. lee

UNDER DUNES:

1. side facing into the wind or water current; long, gentle, gradual slope

2. sheltered, downwind (or downstream) side facing away from the prevailing wind; short steep slope

Glacial Environment

TERRESTRIAL ENVIRONMENTS:

Glacial (ice) processes dominate;

High altitude and latitude regions;

Poorly-sorted mixtures of sediments

Glacial Till

GLACIAL ENVIRONMENTS:

unsorted sediments derived from glacial erosion and entrainment

Moraine

GLACIAL ENVIRONMENTS:

landforms composed of glacial till that has been transported and deposited by a glacier or ice sheet

deltaic environment, low energy

TRANSITIONAL ENVIRONMENTS:

Triangular depositional bodies where a river drains into a larger body of water;

_____ energy except during flood events

False; beaches should be deltas

TRUE OR FALSE:

Beaches (transitional environments) are dominated by fine-grained sediments (mud and sand) with occasional gravel with grain size decreasing away from land and coarsening upwards (along a section) due to progradation.

River-dominated

DELTAIC ENVIRONMENT

associated with high sediment load rivers;

lobate (moderate supply) to elongate (large supply)

Tide-dominated

DELTAIC ENVIRONMENT

exhibit linear inlets parallel to tidal flow and perpendicular to shore

Wave-dominated, coarser

DELTAIC ENVIRONMENT

constantly reworked by wave action;

smoothly arcuate and contains _____ sediments

beach environment

TRANSITIONAL ENVIRONMENT:

shore area of a body of water formed and washed by waves and tides;

_____ energy environment;

False; should be well-sorted

TRUE OR FALSE:

Beaches are covered by poorly-sorted, loose, and highly reworked sand to pebble-sized sediments.

Longshore current

BEACHES:

current moving parallel to shore from swells sweeping into the coastline at an angle

longshore drift

BEACHES:

transportation of sediments along a coast parallel to the coastline

tidal flats, high salinity

TRANSITIONAL ENVIRONMENTS:

these are extensive marshy to barren tract of land that is cyclically submerged by tide with ______ salinity range from mixing of freshwater and salt water;

depositionary environment for finer grained sediments

False; should be low

TRUE OR FALSE:

Tidal flats are of high energy dominated by loose fine mud and sand sediments.

reef

MARINE ENVIRONMENTS:

wave resistant, mound-like structures composed of fossiliferous carbonates and sand along shallow marine settings

• fringing, barrier, atoll

Fringing Reef

TYPES OF REEFS:

in direct contact with landmass;

grows directly attached to or closely seaward from the shorelines of islands or continents, separated only by a narrow, shallow lagoon or flat

Barrier Reef

TYPES OF REEFS:

separated by a lagoon from the landmass;

Run parallel to coastlines but sit much farther out at sea

Atoll

TYPES OF REEFS:

reef without an associated landmass;

Circular or oval-shaped rings of coral enclosing an open central lagoon with no central landmass left above water

continental shelf

MARINE ENVIRONMENT (CONTINENTAL MARGIN):

Continuous and underwater coastal plain;

Between shoreline and continental slope;

Dominated by mud, sand and carbonates (if above Carbonate Compensation Depth)

Carbonate Compensation Depth

MARINE ENVIRONMENT (CONTINENTAL MARGIN):

this is the depth below which the rate of formation of calcite is lower than of its solvation

continental slope & rise

MARINE ENVIRONMENT (CONTINENTAL MARGIN):

Between continental shelf and abyssal plain;

Gentle to moderate incline and smooth topography;

Associated with submarine canyon and fans

• slope: steep descent that marks the true outer edge of the continental crust

• rise: located at the base of the continental slope, sitting between the slope and the deep abyssal plain; wide slope

submarine canyons & fans

MARINE ENVIRONMENT (CONTINENTAL MARGIN):

______ _____ and _____ are associated with continental rise

fining upward sequence

MARINE ENVIRONMENT (CONTINENTAL MARGIN):

Turbidites are sediment laden by turbidity currents characterized by a ____ ____ sequence (conglomerate, sand to massive mud, shales)

• sequence: grain size gradually decreases from coarse at the bottom to fine at the top

abyssal plain; low energy

MARINE ENVIRONMENTS:

Pelagic / Open ocean;

Flat and low relief region of the ocean floor

_____ energy environment

• ex. Pelagic mud, micritic limestones (lime mud) and chert