ASBOG Ch 5 - Rocks, Minerals, and Fossils

Aureole

The zone of metamorphosed rock surrounding an igneous

intrusion and showing the effects of contact metamorphism.

Color Index

A number that represents the percent by weight or volume of

dark-colored minerals in a rock.

Eugeosyncline

The oceanic part of a geosyncline (synform) characterized by volcanism associated with clastic sedimentation

Facies

a mappable. areally restricted part of a rock body that has different fossils or lithology from another contiguous beds deposited at the same time

Diagenesis

The physical and chemical changes undergone by sediments when compacted and lithified

P < 1 kilobar

100 C < T < 300 C

Geosyncline

a major downwarp in the Earth's crust in which sediments accumulate (synform)

Metasomatism

The process of mineral replacement whereby a new mineral of a different chemical composition grows in an old mineral. Interstitial liquids or gases must be present for solution and deposition to occur

Pelitic

Referring to a rock that is composed of clay or clay-sized particles, or derived from metamorphism of a fine-grained sediment

Provenance

The place of origin from which the constituent materials of a sedimentary rock or facies are derived

Sessile

A plant or animal that is attached and cannot move

Test

The external part of an invertebrate

Type Locality

The place where a geologic feature (such as a fossil species) was first recognized and described. It contains a type section.

Zeolites

A large group of hydroaluminosilicate minerals that are analogous in composition to the feldspars. Chief metals are Na, Ca, and K. They occur in basalt cavities, saline lake and deep sea sediments, and volcanic tuff. They are used as water softeners or desiccants.

Zoning

formed by changes in temperature phases

Luster

the property of light reflection from a mineral surface

Specific gravity

the ratio of the mineral density to that of water

pegmatitic texture

intrusive, high water content

porphyritic texture

intrusive or extrusive, two-phase cooling resulting in at least 2 different grain sizes

vesicular texture

extrusive, contains dissolved gasses

frothy texture

extrusive, lots of dissolved gasses

Feldspathoids

rock-forming minerals that have too little silica to form feldspar (never found in the same rock with quartz)

Ex. sodalite, lazurite, leucite, nepheline

Polymorphous

two minerals that have the same chemical formula but different crystal structures (ex. calcite and aragonite)

Dolomite

Precipitates directly from waters in highly saline tidal flats

Diatomite

Formed from silica oozes secreted from diatoms and is formed in oceans where there is little detritus supplied from land

Chert

An amorphous or extremely fine-grained silica found in concretions and beds. Originates in coastal waters and formed by silica-secreting organisms.

Pyrite

Formed by the indirect action of bacteria, which grow only in the absence of oxygen. Pyrite is created when organic matter decays and consumes oxygen.

Peat

Formed when decaying vegetation does not have enough oxygen. Burial (increasing P and T) and chemical transformation turn it to coal.

Sphericity

how close a grain is to being equal in each demension

Arenite

a well-sorted sandstone with rounded grains and no feldspar

Wacke

a poorly-sorted sandstone with a matrix of silt and clay

Arkose

a sandstone with more than 25% feldspar

Graywacke

lithic fragments of iron and magnesium minerals and feldspar are present along with quartz sand and silt

Authigenesis

the process by which minerals form in a sedimentary rock after its deposition

Migmatite

igneous and metamorphic

regional

quartz, feldspar, biotite, and hornblende

Mylonite

coarse-grained rocks

dynamic

quartz and feldspar

Skarn

limestone, dolomite

contact and metasomatism

Ca-rich silicates, also Mg- and Fe-silicates

Argillite

mudstone

very low-grade regional

only slight recrystallization

Greisen

granitic rock

metasomatism of granitic rock

quartz and muscovite (or lepidolite)

Greenstone

mafic igneous

submarine alteration

prehnite-pumpellyite, or greenschist facies minerals

Serpentinite

peridotite

metasomatism of peridotite

serpentine, talc, chlorite

Amphibolite

igneous rocks, shaly limestone

intermediate- to high-grade regional, metasomatism of calcareous sediments

hornblende + plagioclase

Granofels (Granulite)

basement gneisses or igneous rocks

high-grade regional, water poor

quartz, feldspar, pyroxene, and garnet, little mica

Asbestos

a naturally-occurring fibrous silicate mineral that is found in serpentines and amphiboles

stromatolites

layered rocks formed from the accumulation of blue-green algae and sedimentary grains.

Fossil assemblages

groups of animals that lived at the same time and place

Taxonomy Order:

Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species (Keep Pots Clean or Family Gets Sick)

Arthopods have...

external skeletons, segmented bodies, and jointed appendages

Mollusks are invertebrates with three basic parts:

foot, visceral mass, and mantle

Gastropods

crawl

snails, slugs, limpets

Cephalopods

swim

squid, nautilus, octopus

Bivalves

burrow

clams, oysters, mussels, and scallops

Brachiopods

marine invertebrates that inhabit the sea floor in cold water

have two shells or valves unequal in size

Paleozoic abundance

Cnidaria

soft-bodied, mostly marine, colonial animals

corals, sea anemones, jellyfish

Hemichordata

acorn worms and colonial graptolites

graptolites are index fossils between Ordovician and Silurian, die out at end of Devonian

Bryozoa

marine invertebrate colonial filter feeders

Echinodermata

marine spiny animals with radial symmetry (starfish, sea urchins, sand dollars, blastoids, crinoids

Chordata

conodont (eel-like animal from Devonian)

index fossil: color used as indicator of paleo-temps

Foraminifera

Fusilinids (Pennsylvanian to Permian)

marine single-celled protozoa

can be used to precisely date cores and to locate potential sources of oil

Radiolaria

planktonic protozoa that secrete silica to form a spiny, spherical, or conical test

Plankton

any drifting organism in the pelagic zone

Phytoplankton

foundation of the ocean's food web

consume carbon dioxide and release oxygen

as ocean temperatures increase, phytoplankton productivity decreases forming large and expanding deserts in the ocean

Paleoecology

relationship between ancient organisms and the environment where they lived

Benthic

habitat that is found at the floor of the ocean

KT boundary

(65 Ma) Asteroid impact, massive Deccan Traps flood basalts, dinosaur extinction

Triassic-Jurassic boundary

(~200 Ma) Massive volcanic eruptions, killed half of marine life

Permian-Triassic boundary

(~251 Ma) Massive lava eruptions from Siberian Traps, Earth's worst mass extinction (95% of all species)

Late Devonian

(~360 Ma) Cause unknown, killed half of marine life

Ordovician-Silurian boundary

(~440 Ma) Glaciation led to sea level drop, followed by glacial melt and flooding, killed 60% of marine life

Fission Track U238

(100k - 20my) yields cooling ages

Radon222 - Lead210

(150-200 yrs) Dates snowfall, recent fresh and marine sedimentation, environmental pollutant rates

Rubidium87 - Strontium87

(65my - 3.8by) Determines emplacement or cooling ages

Potassium40 - Argon40

(3k - 4.5by) Age of mineralization

Thermoluminescence

(1k - 500k) Burial sediments with radioactivity glow when exposed to LED light; older ages, produce greater light

Optically Stimulated Luminescence (OSL)

(300 yrs - 900k) Measures the last time a mineral was exposed to sunlight

Palynology

the study of pollen grains and other spores, especially as found in archaeological or geological deposits.

Moho discontinuity

crust-mantle boundary

Appalachian orogenies

(490-250 Ma) Tacony, Acadian, Alleghanian

Taconic orogeny

(490-440 Ma; Ordovician-Silurian) thrust volcanic arcs over metamorphosed sediments (VT, NY)

Acadian orogeny

(420-350 Ma; Devonian) formed by the collision of the Avalon island arc with Laurentia (New England)

Alleghanian orogeny

(300-280 Ma; Carboniferous-Permian) Oblique collision of Africa with North America (Mid-Atlantic)

Antler orogeny

(375 - 300 Ma; Late Devonian-Early Pennsylvanian) (NV, ID)

Sonoma orogeny

(280-200 Ma; Permian-Triassic) (NV, UT)

Palisades orogeny

Jurassic, NY

Nevadan orogeny

(150-140 Ma; Jurassic-Cretaceous) (CA, NV)

Sevier orogeny

(130-80 Ma, Late Cretaceous-Paleocene) (Basin & Range)

Laramide orogeny

(80-50 Ma, Late Cretaceous-Early Eocene) (Rocky Mountain Region)