[ROCKS &] SEDIMENT NOTES

ALL Sediments come from ROCKS!! There are 3 Main Rock Types, each with Subtypes

IGNEOUS ROCKS - SUBTYPES & ORIGIN: EXTRUSIVE LAVA ON EARTH’S SURFACE INTRUSIVE MAGMA BELOW EARTH’S SURFACE

Pumice, Obsidian, Basalt Igneous EXTRUSIVE Rocks

Granite Igneous INTRUSIVE Rock Granite is found in many colors due to the change in chemical composition caused by the trace elements found within and around it

SEDIMENTARY ROCKS - SUBTYPES & ORIGIN: CLASTIC FRAGMENTS PIECES OF BROKEN ROCKS NONCLASTIC ORGANICS & CHEMICAL PROCESSES LIVING THINGS & PRECIPITATES/EVAPORITES

Sandstone, Shale, Conglomerate Clastic Sedimentary Rocks

Limestone, Coal, Coral Reefs Nonclastic (Organic) Sedimentary Rocks limestone (shells) (coal) (coral reefs)

Gypsum, Rock Salt, Limestone (caves) Nonclastic (Chemical) Sedimentary Rocks (& precipitate in seawater)

METAMORPHIC ROCKS - SUBTYPES & ORIGIN: FOLIATED Minerals from parent rock align to create bands, layers or stripes MUST KNOW PARENT ROCKS UNFOLIATED Minerals from parent rock seem to blend; no obvious bands or layers

Slate, Schist, Gneiss Foliated Metamorphic Rocks (from shale) (from phyllite) (from granite)

Marble, Quartzite Unfoliated Metamorphic Rock (from limestone) (from sandstone)

Can help you identify what mineral/rock the sediment is made of. SEDIMENT COLOR Can help you identify what mineral/rock the sediment is made of. Helps determine its source.

Rounded  Traveled very far Angular  Close to its origin SEDIMENT SHAPE Running river water smooths out the surface of a sediment grain as it travels to the ocean. Weathering and erosion also smooth out sediment. The rounder the sediment is, the farther it has traveled from its source. Rounded  Traveled very far Angular  Close to its origin

ANGULAR ROUNDED

SEDIMENT SIZE Small sediments: low energy beach (little to no waves needed to move them) Large sediments: high energy beach (big, strong waves needed)

Biggest  Boulders  Very high wave energy Cobbles Pebbles Sand Silt  Very low wave energy Smallest  Clay  *Exception – clay requires very high energy to be moved

4 TYPES OF SEDIMENTS Terrigenous - from continents (aka Lithogeneous) Biogenous – plant or animal origin Hydrogenous - precipitated from water Cosmogenous - from outer space

TERRIGENOUS SEDIMENTS Covers approximately 45% of the ocean floor Composed of weathered rock material from land *Most common composition:          QUARTZ (SiO2)          CLAY MINERALS

TERRIGENOUS SED., CONT. *When found on continental margins: - Carried to the ocean by rivers - Coarse sediment is nearest to the shore - Finer sediment is found offshore

TERRIGENOUS SED., CONT. *When found in deep ocean basins: - Carried by turbidity currents & found near continents - Carried by wind (clay size particles) and can be found far from land

BIOGENOUS SEDIMENTS Covers about 55% of the ocean floor. *From benthic organisms:    -coral reef debris & shell fragments *From zooplankton - Calcium carbonate (CaCO3) composition: Foraminifera & Coccolithophores - Silicate (SiO2)composition: Radiolaria & Diatoms

Biogenous, Cont’d. Can range in size from coarse to fine Predominantly shells and skeletons Oozes! (consistency of thick mud; produced as shells decompose) Calcareous ooze dredged from the Arctic Ocean Bottom. Photo: Bogdan Onac

HYDROGENOUS SEDIMENTS *Manganese nodules (deep ocean basin) from: - hydrothermal vent water *Evaporites:  -restricted circulation + high evaporation = precipitation of salts -originate from chemical reactions that occur in the existing sediment

COSMOGENOUS SEDIMENTS Always <1% of a sediment Rain down uniformly from space, but most abundant in deep ocean sediments because not "diluted" by other kinds of sediments *Meteorite fragments & dust *Rare earth elements