Chapter 7 - Sedimentary Rocks

three diagenetic changes that can occur in clastic sediments during burial

-recrystallization -chemical alteration (organic matter transformed into carbon) -lithification

Conglomerate

A coarse-grained sedimentary rock (grains coarser than 2 millimeters) formed by the cementation of rounded gravel.

Shale

A fine-grained sedimentary rock (grains finer than 1/16 millimeter in diameter) formed by the cementation of silt and clay (mud). Shale has thin layers (laminations) and an ability to split (fissility) into small chips.

Travertine and how does it form

A form of limestone that is deposited by hot springs or as a cave deposit

Chert

A hard, compact, fine-grained sedimentary rock formed almost entirely of silica.

Compaction

A loss in overall volume and pore space of a rock as the particles are packed closer together by the weight of overlying material.

Bedding Plane

A nearly flat surface separating two beds of sedimentary rock.

Travertine

A porous deposit of calcite that often forms around hot springs.

Chemical Sedimentary Rock

A rock composed of material precipitated directly from solution.

A graywacke is...

A sandstone with the sand grains embedded in a clay-rich matrix

Gradded Bedding

A sedimentary layer where grains range in size from coarsest at the bottom to finest at the top.

Limestone

A sedimentary rock composed mostly of calcite.

Detrital sedimentary rock

A sedimentary rock composed of fragments of preexisting rock.

Sandstone

A sedimentary rock composed of sand-size grains of mineral, rock, or organic material

Dolostone

A sedimentary rock composed primarily of the mineral dolomite, CaMg(CO3)2

Siltstone

A sedimentary rock consisting mostly of silt grains.

Organic reef

A sedimentary rock structure of significant dimensions erected by, and composed almost exclusively of the remains of, corals, algae, bryozoans, sponges, and other sedentary or colonial organisms.

Evaporites

A sedimentary rock that consists of one or more minerals formed as precipitates from the evaporation of a saline solution, such as saltwater.

Coquina

A sedimentary rock that is composed either wholly or almost entirely of the transported, abraded, and mechanically-sorted fragments of the shells of molluscs, trilobites, brachiopods, or other invertebrates

Chalk

A very fine-grained bioclastic limestone.

Crystalline texture

An arrangement of interlocking crystals

Cross-bedding

An arrangement of relatively thin layers of rock inclined at an angle to the more nearly horizontal bedding planes of the larger rock unit.

Clastic texture

An arrangement of rock fragments bound into a rigid network by cement.

Rock gypsum

An evaporite composed of gypsum.

Bituminous coal (organic)

An organic sedimentary rock formed by diagenetic and sub metamorphic compression of peat bog material. Its primary constituents are macerals: vitrinite, and liptinite.

Fossiliferous limestone

Any type of limestone, made mostly of calcium carbonate (CaCO3) in the form of the minerals calcite or aragonite, that contains an abundance of fossils or fossil traces

Facies

Bodies of sediment that are recognizably distinct from adjacent sediments that resulted from different depositional environments

Which type of carbonate sedimentary rock consists mainly of tiny, microscopic marine fossils composed of calcite?

Chalk

Describe how currents sort sediment during transport

Describe how currents sort sediment during transport

Salt Flat

Flat expanses of ground covered with salt and other minerals, usually shining white under the Sun

Biochemical

Precipitated by the action of organisms

Sorting

Process of selection and separation of sediment grains according to their grain size (or grain shape or specific gravity).

On what basis is sandstone further classified into quartz sandstone, arkose and graywacke?

Quartz = quartz is predominant Arkose = feldspar is 25% or more. poor sorting Graywacke = 15% or more is matrix poor sorting

Which of the following sedimentary features can each be used to determine paleocurrent directions?

Ripple marks and cross-bedding

Zircon and tourmaline are dense, insoluble, chemically stable, minor minerals of igneous and metamorphic rocks. In which sedimentary rock might you expect to find these minerals concentrated?

Sandstone lithified from quartz-rich beach sand

Mudcracks

Sedimentary structures formed as muddy sediment dries and contracts. Crack formation also occurs in clayey soils as a result of a reduction in water content.

Oolitic limestone is most likely to form in what type of depositional environment?

Shallow, clear, marine waters with vigorous current activity

Fissility

The ability of a rock to split into thin layers.

Diagenesis

The change of sediments or existing sedimentary rocks into a different sedimentary rock during and after rock formation (lithification), at temperatures and pressures less than that required for the formation of metamorphic rocks. It does not include changes from weathering.

Cementation

The chemical precipitation of material in the spaces between sediment grains, binding the grains together into a hard rock.

bioturbation structure

The process by which organisms rework existing sediments by burrowing through muds and sands.

Lithification

The process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock

Bioturbation

The reworking of soils and sediments by animals or plants. Its effects include changing the texture of sediments (diagenesis), bioirrigation, and displacement of microorganisms and non-living particles.

Sedimentary environment

Transported sediments are ultimately deposited in lowlands, coastal plains, shallow ocean or deep ocean.

How does dolostone form from limestone?

When magnesium rich waters circulate through limestone and convert calcite to dolomite by replacing calcium ions with magnesium ions aka DOLOMIZATION

Turbidity Current

When mud and sand on the continental shelf are loosened by earthquakes, collapsing slopes, and other geological disturbances

Detrital sedimentary rocks have ___ textures.

clastic

Describe the differences between detrital and chemical sediments and sedimentary rocks

detrital and chemical sediments are made from rock particles and chemical sediments are made from percipitated minerals Sedimentary rock is a type of rock that is formed by sedimentation of material at the Earth's surface and within bodies of water

What is the basis for classification of detrital sediments and sedimentary rocks?

detrital: particle size chem/organic: composition

Graded bedding is usually associated with beaches and desert sand dunes (t/f)

false

graded-bedding sed struct (& environment)

layers change from coarse at the bottom to fine at the top -bottom of lake or ocean

cross-bedding sed struct (& environment)

layers inclined to the horizontal -sand dunes -river deltas

What type(s) of sedimentary rock(s) is/are associated with reefs

limestone

Where does coal originate? How does coal form?

made of organic matter & is accumulation of plant remains buried for millions of years -swamp environments

Which of the sediment undergoes the most compaction and reduction in volume during burial and lithification to sedimentary rock?

marine mud

What is meant by inorganic precipitation of chemical sedimentary rocks?

processes such as evaporation and chemical activity producing chem sed -dripstone that decorates caves

mud cracks (& environment)

sediment was alternatively wet & dry -tidal flats -shallow lakes -desert basins

Biochemical sediment & example

sedimentary rock formed from material (such as shells) produced by living organisms

Describe the stages leading to formation of a detrital sedimentary rock: e.g. weathering, erosion, transportation, deposition, compaction, and lithification. At what stage does compaction and lithification occur?

sedimentary rock is made from lithification which is compaction, cementation, recrystalization. lithification occurs when the sediment is planted or after. compaction occurs Compaction occurs as the weight of the overlying material increases. Compaction forces the grains closer together, reducing pore space and eliminating some of the contained water.

Sedimentary environments for marine

shallow marine borders continents deep marine include floors of the ocean

Sedimentary environments for transitional

shoreline beaches tidal flats spits lagoons deltas

A cherty limestone would contain which major constituents?

silica & calcite

ripple marks sed struct (& environment)

small waves of sand that develop on the surface of a sediment layer by the action of moving air/water -shallow near shore environment

Sedimentary environments for Non-marine continental

streams, glaciers, deserts,

Coal beds originate in...

swamps

How do currents modify the composition of sediments during transport? Describe the composition of an immature sediment; a mature sediment.

texture, size, roundness. an immature sediment was buried early in the mud basin, well sorted sediment with no mud is mature.

Which of the following is a form of calcium carbonate typically found as cave deposits?

travertine