Geology: Sedimentary Rocks

made from ions and dissolved from pre-existing rocks

made of fragments and pre-existing rock

Tells us how fast/slow and far the sediment was transported

fast flowing rivers

moderate flowing beaches

lakes and deep ocean

It rounds out as it has eroded against so many other materials

compaction and cementation

the process that turns loose sediment into solid sedimentary rock

pressure from overlying sediment squeezes sediment grains together,

dissolved minerals precipitate and fill the spaces between sediment grains, gluing them together

the layered structure visible in sedimentary rocks

happens when loose sediment is deposited in layers by water, wind, or ice, and those layers eventually harden into rock

sedimentary structures that form when fine-grained, water-saturated mud or clay dries out

the disturbance or mixing of sediment by organisms, such as worms burrowing or animals digging

small ridges in sediment formed by moving water or wind

thin sediment layers deposited in lakes, usually forming a pair of layers each year due to seasonal changes.
winter = darker
summer = lighter

Carbonate, Evaporite, Siliceous, Carbonaceous

derived from shells and biological activity

crystals precipitate from evaporating water

silica precipitates in situ

compressed remains of plant material

Carbonates form in warm, shallow ocean water because they’re more likely to accumulate due to favorable conditions
In cold, deep ocean water, calcium carbonate dissolves more easily because of higher pressure and more dissolved CO₂

continental, transitional, marine

Sediment is deposited on land.
examples: rivers, lakes, deserts, glaciers, and alluvial fans.

Sediment is deposited where land meets the sea.
examples: beaches, deltas, tidal flats, lagoons, and estuaries.

Sediment is deposited in the ocean.
examples: continental shelves, coral reefs, deep-ocean floors, and submarine fans.

deltas form when a river flows into a lake or ocean, slows down, and deposits sediment. Over time, the sediment builds up and creates new land at the river's mouth.

warm, shallow, clear, sunlit, salty water

Turbidites form through underwater avalanches called turbidity currents and are recognized by their distinct, layered sediment patterns known as the Bouma sequence

A diagram showing the sequence of rock layers in an area and their characteristics.

Bottom = oldest rocks
Top = youngest rocks

sedimentary environments that occur next to each other horizontally can appear as layers stacked vertically over time, as environments shift.

bottom to the top

uses fossils in rock layers to determine their relative ages and correlate rocks from different locations. Certain fossils indicate specific time periods.

uses changes in Earth's magnetic field recorded in rocks to determine ages and match rock layers from different locations

when existing rocks change because of heat, pressure, and chemically active fluids without melting completely

minerals change size or shape, affecting the rock's texture

new minerals form, changing the rock's mineral composition

minerals flatten or align, changing the rock's texture and shape

minerals react with fluids or each other, changing the rock's composition

the arrangement of minerals into parallel layers or bands in a metamorphic rock

directed pressure squeezes the rock, causing minerals to flatten or align in the same direction

the intensity of metamorphism based mainly on temperature and pressure

higher-grade rocks typically have larger mineral grains and minerals that form at higher temperatures and pressures

Slate
Phyllite
Schist
Gneiss

Near magma intrusions, where heat changes surrounding rock

Deep underground over large areas, often during mountain building, due to heat and pressure.

Where hot, chemically active fluids interact with rock, often near mid-ocean ridges.

Deep beneath the surface, where sediment is buried under more layers, increasing pressure and temperature.

Along faults, where rocks experience intense pressure and shearing.

High temperature, low pressure.

High temperature, high pressure.

High temperatures from hot fluids; pressure varies.

Low to moderate temperature and increasing pressure with depth.

High directed pressure and stress along faults; temperature varies

younger strata stacks on top of older strata

rock deposits flat and dissolves later

a rock unit that cuts through another is younger than the one it's cutting

rocks deposit in continuous horizontal layers

a contact where the sequence in deposition has been interrupted

a pause in deposition that allows for erosion or a very abrupt change in pattern, layers remain parallel

rock beds aren’t parallel

abrupt contact between sedimentary AND igneous/ metamorphic

combining relative rock sequences, fossil records, and radiometric dating

Unstable atomic nucleus loses energy by emitting radiation to transform into a more stable element or isotope

an unstable, radioactive atom that breaks down into a new, more stable atom through radioactive decay

emaining product that forms after parent isotope undergoes radioactive decay

the amount of time it takes for a substance to reduce to half of its initial value or amount

The only way we’re able to get absolute dates for sedimentary rock is from igneous intrusions and extrusions. This happens when a magma chamber pushes its way into older sedimentary rock layers, or cuts across them