EAS 222 Midterm 2

Conglomerate

A sedimentary rock composed of rounded gravel-sized clasts.

Siltstone

A sedimentary rock composed of silt-sized particles.

Claystone

A sedimentary rock made up primarily of clay-sized particles.

Sandstone

A clastic sedimentary rock composed mainly of sand-sized grains.

Framework

The grains that make up the skeleton or structure of sandstone.

Matrix

The finer-grained material that fills the spaces between framework grains.

Cement

Mineral material that precipitates in the spaces between sediment grains and binds them together.

Pores

Spaces or voids between grains in a rock that can contain fluids.

Accessory minerals

Minerals present in small amounts in a rock, important for provenance studies.

Arenite

A sandstone with less than 15% matrix.

Wacke

A sandstone with more than 15% matrix.

Arkose

A sandstone with more than 25% feldspar present.

Olistolith

A very large clast found within a sedimentary rock.

Olistostrome

A rock made up of olistoliths, similar to conglomerate but on a larger scale.

Fabric-selective porosity

Porosity controlled by the arrangement of grains in the rock.

Fabric-destructive porosity

Porosity that develops as a result of the destruction of the rock's fabric.

Cementation

The process that reduces pore space in sandstone by filling voids with mineral deposits.

Dissolution

The process that creates pore space by dissolving certain minerals.

Compaction

The process that decreases pore space by compressing sediment layers.

Calcite

A common carbonate mineral that forms from calcium carbonate.

Halite

A mineral composed of sodium chloride, commonly known as rock salt.

Dolomite

A carbonate mineral composed of calcium magnesium carbonate.

Aragonite

A carbonate mineral made of calcium carbonate, more soluble than calcite.

Biological material

Organic remains, such as shells and bone fragments, found in carbonate rocks.

Seawater evaporation sequence

The order in which minerals precipitate from evaporating seawater: calcium carbonate, gypsum, halite.

Carbonate Compensation Depth

The depth in the ocean below which calcium carbonate dissolves faster than it is deposited.

Intercrystal porosity

Pores occurring between crystals within a rock.

Moldic porosity

Pores left by the removal of grains, commonly seen in sedimentary rocks.

Fenestral porosity

Porosity associated with aligned ellipsoidal pores, common in supratidal sediments.

Fracture porosity

Low porosity associated with fractures in a rock.

Channel porosity

Irregular porosity associated with channel-like structures.

Vug porosity

Single irregular cavities in a rock.

Burrow porosity

Porosity created by the activities of infauna that replace grains.

Glauconite

A ferris-iron silicate mineral that forms on the sea floor from various biological and chemical processes.

Siderite

An iron carbonate mineral that forms under anoxic conditions.

Banded Iron Formation (BIF)

Layered formations created when high iron and oxygen levels in water lead to the deposition of iron oxides.

Phosphorites

Sedimentary deposits rich in phosphate minerals, primarily found in marine settings.

Alluvial fan

A fan-shaped deposit formed where a stream flows out of a mountain or steep area onto a flatter plain.

Fluvial fan

Broad sedimentary deposits formed by rivers, characterized by a fluid flow pattern.

Fan delta

An alluvial fan that extends into a standing body of water.

Crevasse splay

Deposits formed when a river breaks its levee and spreads sediment over adjacent floodplains.

Ventifact

A rock that has been shaped by wind-driven sand or ice particles.

Barchan Dunes

Dunes that form in conditions with limited sand supply and consistent wind direction.

Transverse Dunes

Formed in areas with a large sand supply and consistent wind.

Linear Dunes

Dunes that form with two prominent wind directions and limited sand supply.

Star Dunes

Dunes that form in areas of multidirectional winds with good sand supply.

Hydrologically closed lake

A lake system with no exchange of water or materials with other systems.

Hydrologically open lake

A lake system where there is an exchange of materials or energy with other systems.

Stratified lake layers

Different layers in a lake defined by temperature and density, typically including epilimnion, metalimnion, and hypolimnion.

Ooids

Small, spherical grains composed of calcium carbonate, typically formed in warm, shallow marine waters.

Fringing reef

A type of reef that develops close to shore with no significant lagoon.

Barrier reef

A reef that lies some distance from the shore and creates a lagoon between the reef and the coast.

Patch reef

Small isolated reefs found within a larger area of sediment or water.

Bioherm

A type of carbonate buildup formed primarily of carbonate-secreting organisms.