Sedimentary Environments, Rocks, and Geological Processes Overview

What covers most of Earth's exposed surface?

Sediment and sedimentary rocks

How are sediment and sedimentary rocks formed?

Through weathering and erosion

What transports sediment?

Water, ice, and wind

Where can sediment be deposited?

In environments ranging from deserts to deep oceans

What is lithification?

The process of loose sediment hardening into sedimentary rock

Why are sedimentary rocks important?

They host energy, mineral, and water resources

What is the Fraser River used as a case study for?

To illustrate sediment transport and deposition

What is a braided river?

A river with multiple channels that branch apart and rejoin

What is the impact of the Fraser River delta on Vancouver?

Vancouver is built on the older part of the delta, providing farmland and groundwater

What is weathering?

Physical and chemical processes acting on near-surface materials

What is erosion?

The transport of loose rock and soil downhill

What are clasts?

Broken pieces of rock

What is clastic sediment?

Sediment made of clasts

What is nonclastic sediment?

Sediment not made of clasts, such as chemical deposits

What are the 8 land sedimentary environments?

Mountain, mountain streams, sand dunes, glaciers, meandering streams, delta, lakes, wetlands

What characterizes mountain sedimentary environments?

Steep slopes on bedrock with vigorous erosion

What is a delta?

A sediment deposit where a river meets the sea

What are the characteristics of beaches?

Stretches of coastline where sediment accumulates, varying by setting

What defines lagoons?

Sheltered water near shorelines, calm and warm, with land-derived and coral sediment

What types of sediment are found on continental shelves?

Layers of mud, sand, and carbonate

What is found on the deep seafloor?

Fine windblown dust and remains of single-celled marine organisms

What are tidal flats?

Low areas on shorelines that are flooded at high tide and exposed at low tide

What is the significance of wetlands?

They are very wet environments that support abundant water-dependent vegetation

What is the relationship between sediment and groundwater?

Sediment can contain groundwater in subsurface, supplementing rivers and lakes

What is the role of glaciers in sediment transport?

They carry eroded materials downhill and release sediment upon melting

What is the sediment type found in sand dunes?

Almost entirely sand with little to no other sizes

What are the key characteristics of meandering streams?

Gentle terrain with streams that meander and flanked by flat floodplains

What are submarine deltas?

Submarine deltas extend tens of kilometers offshore from shore and may have unstable muddy or sandy fronts where material slides down to deeper water.

What are barrier islands?

Long, narrow islands that rise above shallow coastal waters, with areas between them and the shoreline being shallow lagoons or saltwater marshes.

Define turbidity currents.

Turbulent, flowing masses of sand, mud, and water.

What are submarine canyons?

Branching canyons on continental slopes that funnel sediment to deeper waters.

What are evaporite minerals?

Salt and other minerals that accumulate as seawater and terrestrial water evaporate under hot, arid conditions.

What are the key characteristics of beaches?

Stretches of coastline where sediment accumulates, with sediment type depending on the setting.

Describe lagoons.

Sheltered, shallow, calm, and warm waters near shorelines, with land-derived sediment in nearshore areas and sand/coral from reefs in outer areas.

What defines reefs?

Shallow, warm, clear waters where coral and marine organisms build structures that protect shorelines from waves.

What are continental shelves and slopes?

Areas away from the shoreline with layers of mud, sand, and carbonate, where material moves down slope in landslides or turbidity currents.

What is the deep seafloor?

Dark, cold areas several kilometers beneath the surface with less sediment than regions closer to land.

What are coastal dunes?

Sandy dunes located inland from beaches, shaped by wind and sediment movement.

Define tidal flats.

Low areas on shorelines that are flooded at high tide and exposed at low tide, often accumulating salt or evaporite minerals.

How are clastic sediments classified by size?

Sizes include boulders (>256 mm), cobbles (64-256 mm), pebbles (4-64 mm), granules (2-4 mm), sand (1/16-2 mm), silt (1/256-1/16 mm), and clay (<1/256 mm).

What are the three size groups of clastic sediments?

Gravel (boulders, cobbles, pebbles, granules), sand, and mud (silt + clay).

What are the shapes of clasts?

Clasts can be angular (sharp corners), rounded (smooth surfaces), or partially rounded (some edges worn down).

What does sorting refer to in sediment?

The range of clast sizes in sediment, classified as poorly sorted, moderately sorted, or well-sorted.

What factors control the size, shape, and sorting of clasts?

Steepness of slope, strength of current, sediment supply, and agents of transport.

What happens to clasts during transport?

They undergo tumbling, collisions, and abrasion, which reduce size, increase roundness, and sort by size.

What is the sediment type found in deep seafloor environments?

Fine windblown dust and remains of single-celled marine organisms.

What sediment types are found in tidal flats?

Mud, sand, or rocky sediments, often with salt or evaporite minerals.

What is the significance of transport distance for clasts?

Transport distance affects clast size and sorting; closer to the source, clasts are larger and more angular.

How do strong currents affect sediment transport?

Strong currents can move large clasts, while slow currents typically only transport fine sediments.

What is the role of wind in sediment transport?

Wind can only carry sand and finer sediments.

What are the characteristics of poorly sorted sediment?

Sediment with a wide range of clast sizes.

What defines well-sorted sediment?

Sediment where all clasts are the same size, such as sand on dunes.

What process forms clastic sedimentary rocks?

Lithification, which involves compaction and cementation.

What are the two main processes involved in lithification?

Compaction and cementation.

What is the primary factor that classifies clastic sedimentary rocks?

Clast size.

What type of clastic rock is formed from rounded gravel-sized clasts?

Conglomerate.

What is breccia?

A clastic rock made of angular clasts, poorly sorted, and with a jumbled appearance.

What is sandstone primarily composed of?

Sand-sized grains.

What distinguishes arkose from other sandstones?

It contains at least 25% sand-sized feldspar grains.

What is quartz sandstone primarily made of?

Mostly quartz grains.

What is graywacke?

A clastic rock with grains of several different compositions including quartz and feldspar.

What is siltstone composed of?

Silt-sized particles, generally quartz.

What characterizes shale?

Very fine-grained clay minerals that break into sheetlike pieces.

What happens during the compaction process?

Increasing pressure pushes clasts together, forcing out excess water and reducing volume.

What is cementation in sedimentary rock formation?

The process where dissolved materials precipitate to bind grains together.

What are the four types of natural cement?

Calcite, silica, clay minerals, and iron oxides.

What is the composition of rock salt (halite)?

NaCl, formed from evaporated seawater.

How does gypsum form?

From seawater evaporation in tidal flats.

What is limestone primarily composed of?

Calcium carbonate, often from shells and coral.

What is the difference between biochemical and inorganic limestone?

Biochemical limestone forms from organisms, while inorganic limestone precipitates from water.

What is peat?

Accumulated plant material in swampy environments that can lithify into coal.

What is the process that leads to the formation of coal?

Peat is buried, compacted, and heated, losing water and oxygen.

What is chert composed of?

Silica (SiO₂) from compacted silica-rich plankton shells or precipitated from seawater.

What is the significance of iron formations?

They consist of iron oxide layers that precipitated from seawater in Earth's early history.

What are evaporites?

Rocks formed from the evaporation of water, leaving behind salts and minerals.

What is the role of plant accumulation in sedimentary rock formation?

Plants accumulate, decay, and compact to form lithified rock like coal.

What is the term for thick layers of sedimentary rock?

Formations.

What are thin layers of sedimentary rock called?

Beds or bedding.

What factors can affect the thickness and composition of sedimentary layers?

Discrete events, changes in current, sediment supply, sea level, or climate.

What is the thickness range of sedimentary rock layers?

From millimeters (beds) to meters (formations)

What defines sedimentary rock layers?

Layers are distinct by grain size (e.g., sandstone = sand, shale = clay) and composition.

What are the two types of boundaries in sedimentary rock layers?

Sharp (distinct contact) and gradational (gradual change).

What characterizes a sharp boundary in sedimentary rocks?

A very distinct contact between layers.

What is a gradational boundary in sedimentary rocks?

A gradual change in grain size, composition, or thickness upward.

What is a scoured boundary?

A sharp contact indicating that the underlying unit was eroded before the overlying layer was deposited.

What is one cause of layer formation in sedimentary rocks?

Discrete events, such as flood deposits leading to rapid sand influx.

How does a change in current affect sedimentary layers?

Coarse sediment is deposited by strong currents, while fine sediment is deposited by weak currents.

What role does sediment supply play in layer formation?

Changes in sediment supply can lead to variations in layer composition, such as tan quartz-rich sandstone between limestone-clast conglomerate layers.

How does sea-level change affect sedimentary layers?

It causes alternation between marine limestone and marine/nonmarine shale and siltstone.

What is the impact of climate change on sedimentary layers?

It can lead to variations in layer composition, such as lower gray clay from wet periods versus top sands from desert conditions.

What are graded beds?

Layers formed when a strong current loses velocity, dropping progressively finer sediment from coarse at the base to fine at the top.

What are cross beds?

Layers formed when grains accumulate on the down-current side of dunes or ripples, angled to other beds.

What are parallel beds?

Most beds are parallel, reflecting the piling of one layer on another under various conditions.

What are the key characteristics of breccia?

Breccia contains large, angular clasts, is poorly sorted, and has massive layers with little visible bedding.

In what environments does breccia typically form?

Mudflows, debris flows, landslides, alluvial fans, and glaciers.

What distinguishes conglomerate from breccia?

Conglomerate has rounded clasts indicating longer transport, while breccia has angular clasts indicating minimal transport.

What are the formation environments for conglomerate?

Stream channels, braided streams, beaches, and deltas/turbidity currents.

What is the dominant mineral found in sandstone?

Quartz.

What are the characteristics of sandstone?

Sandstone is composed mostly of sand-sized grains, moderately to well-sorted, and can contain silt or scattered pebbles.

What environments are conducive to sandstone formation?

Land environments like sand dunes and streams, shorelines like beaches and deltas, and offshore environments like continental shelves.