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Thesaurus

Or

Oran
SN	No longer a valid term for GeoRef. Valid 1978-1981. As of 1982, see Oran region for the department of French Algeria. As of 1993, see Oran Algeria for the department.

Oran Algeria
BT	Africa
	.North Africa
	..Algeria
	...Oran Algeria
NT	Descartes Algeria
SN	Department. NW coast. Before 1993, also search Oran region.

Oran region
SN	No longer a valid term for GeoRef. Used as large department of French Algeria. As of 1993, see Algeria for departments.

Orange County California
BT	United States
	.California
	..Orange County California
NT	Santa Ana California
RT	San Jacinto Fault
	San Pedro Bay
	Newport Bay
	Santa Ana Mountains
	Santa Ana River
SN	S California.

Orange County Florida
BT	United States
	.Florida
	..Orange County Florida
SN	Central Florida.

Orange County Indiana
BT	Indiana
	.Orange County Indiana
SN	S Indiana.

Orange County New York
BT	United States
	.New York
	..Orange County New York
NT	Port Jervis New York
SN	SE New York.

Orange County North Carolina
BT	United States
	.North Carolina
	..Orange County North Carolina
SN	N central North Carolina.

Orange County Texas
BT	United States
	.Texas
	..Orange County Texas
RT	Sabine Lake
SN	SE Texas.

Orange County Vermont
BT	United States
	.Vermont
	..Orange County Vermont
SN	Central and E Vermont.

Orange County Virginia
BT	United States
	.Virginia
	..Orange County Virginia
SN	N central Virginia.

Orange Free State South Africa
USE	Free State South Africa

orange material
RT	Moon

Orange River
BT	Africa
	.Southern Africa
	..Orange River
RT	Namibia
	Cape Province region
	Northern Cape Province South Africa
	Eastern Cape Province South Africa
	Free State South Africa
	Lesotho
SN	Rises in the Drakensberg Range in Lesotho and flows W into the Pacific Ocean. Indexed with Namibia, Lesotho and provinces of South Africa.

Orangeburg County South Carolina
BT	United States
	.South Carolina
	..Orangeburg County South Carolina

Orava Valley
BT	Europe
	.Central Europe
	..Slovakia
	...Orava Valley
SN	River valley in N Slovakia. Also search Orava.

orbicular texture
BT	textures
	.orbicular texture
RT	spherulites
SN	Before 1978, search orbicular AND texture.

orbit
USE	orbits

orbital forcing
UF	climatic orbital forcing
	Milankovitch forcing
RT	sedimentation
	climate
	paleoclimatology
	paleo-oceanography
	climate effects
	climatic controls
	cyclic processes
	periodicity
	Milankovitch theory
SN	Also search Milankovitch theory if applicable. Added to Thesaurus in 1998.

orbital motion
USE	orbits

orbital observations
RT	observations
	orbits
	remote sensing
	satellite methods
SN	Before 1978, search observations AND orbital.

Orbitoidacea
BT	Invertebrata
	.Protista
	..Foraminifera
	...Rotaliina
	....Orbitoidacea
NT	Amphistegina
	Asterocyclina
	Cibicides
	Discocyclina
	Lepidocyclina
	Nephrolepidina
	Orbitoididae
RT	microfossils
SN	Indexed with microfossils if applicable.

Orbitoidae
USE	Orbitoididae

Orbitoididae
BT	Invertebrata
	.Protista
	..Foraminifera
	...Rotaliina
	....Orbitoidacea
	.....Orbitoididae
UF	Orbitoidae
RT	microfossils
SN	Indexed with microfossils if applicable.

Orbitolina
BT	Invertebrata
	.Protista
	..Foraminifera
	...Textulariina
	....Lituolacea
	.....Orbitolinidae
	......Orbitolina
RT	microfossils
SN	Genus. Indexed with microfossils if applicable.

Orbitolinidae
BT	Invertebrata
	.Protista
	..Foraminifera
	...Textulariina
	....Lituolacea
	.....Orbitolinidae
NT	Orbitolina
RT	microfossils
SN	Family. Indexed with microfossils if applicable.

orbits
UF	orbit
	orbital motion
	planetary orbits
RT	motions
	planetology
	extraterrestrial geology
	satellite methods
	orbital observations

Orbulina
BT	Invertebrata
	.Protista
	..Foraminifera
	...Rotaliina
	....Globigerinacea
	.....Globigerinidae
	......Orbulina
NT	Orbulina universa
RT	microfossils
SN	Genus. Indexed with microfossils if applicable.

Orbulina universa
BT	Invertebrata
	.Protista
	..Foraminifera
	...Rotaliina
	....Globigerinacea
	.....Globigerinidae
	......Orbulina
	.......Orbulina universa
RT	microfossils
SN	Species. Indexed with microfossils if applicable.

Orca Basin
BT	Atlantic Ocean
	.North Atlantic
	..Gulf of Mexico
	...Orca Basin
RT	DSDP Site 618
SN	Depression on the continental slope of the N central Gulf of Mexico, containing brines. Added to Thesaurus in 1981.

Orca Group
BT	Chronostratigraphic Units
	.Phanerozoic
	..Cenozoic
	...Paleogene
	....Orca Group
RT	Paleocene
	Eocene
	Alaska
SN	S central Alaska. Indexed with ages as applicable. Added to Thesaurus in 1989.

Orcadian Basin
BT	Atlantic Ocean
	.North Atlantic
	..North Sea
	...Orcadian Basin
RT	Scotland
	Orkney Islands
SN	Offshore NE Scotland, in the North Sea. Added to Thesaurus in 1989.

order-disorder
RT	amorphous materials
	bonding
	crystal chemistry
	substitution

ordinary chondrites
BT	meteorites
	.stony meteorites
	..chondrites
	...ordinary chondrites
RT	enstatite chondrites
	carbonaceous chondrites
SN	Added to Thesaurus in 1985.

Ordos Basin
BT	Asia
	.Far East
	..China
	...Ordos Basin
UF	Eerduosi Basin
	Erduos Basin
RT	Inner Mongolia China
	Shanxi China
	Gansu China
	Ningxia China
	Shaanxi China
SN	NE central China. Before 1995, also search Eerduos Basin. Added to Thesaurus in 1989.

Ordovician
BT	Chronostratigraphic Units
	.Phanerozoic
	..Paleozoic
	...Ordovician
NT	Lower Ordovician
	Middle Ordovician
	Upper Ordovician
	Antelope Valley Limestone
	Bala
	Betts Cove Ophiolite
	Borrowdale Volcanic Series
	Buchans Group
	Catoche Formation
	Chickamauga Group
	Clays Ferry Formation
	Davidsville Group
	Ely Springs Dolomite
	Eureka Quartzite
	Gander Lake Group
	Gull River Formation
	Ledbetter Slate
	Lushs Bight Group
	Martinsburg Formation
	Meguma Group
	Montoya Group
	Pogonip Group
	Shap Granite
	Skiddaw Slates
	Tetagouche Group
	Valmy Formation
	Vinini Formation
	Viola Limestone
	Viruan
	Womble Shale
RT	Bowers Supergroup
	Ellis Bay Formation
	Berwick Formation
	Merrimack Group
	Collier Shale
	Cow Head Group
	Delamerian Orogeny
	Elberton Granite
	Henderson Gneiss
	New York City Group
	Hanson Creek Formation
	Lincolnshire Limestone
	Kittery Formation
	Penobscot Formati
SN	After the Cambrian, before the Silurian.

Ordubad Azerbaijan
BT	Europe
	.Azerbaijan
	..Nakhichevan Azerbaijan
	...Ordubad Azerbaijan
SN	City in Nakhichevan Autonomous Soviet Socialist Republic (W enclave of Azerbaijan). This term has multiple hierarchies.

ore bodies
UF	bodies, ore
RT	mineral deposits, genesis
	metal ores
	blind deposits
	chimneys
	size

ore deposits
SN	As of 1981, no longer a valid term for GeoRef. Before 1981, included use for all papers on metal commodities. Was sometimes used in combination with origin (i.e. ore deposits, origin). Now use metal ores; mineral deposits, genesis; mineral resources or sp

ore exploration
USE	mineral exploration

ore finding
SN	Not a valid index term for GeoRef. See mineral exploration.

ore grade
RT	cutoff grade
	economic geology
	evaluation
	grade
	metal ores
	mineral economics
	mineral exploration
	production
	productive capacity
	reserves
	tonnage
SN	Added to Thesaurus in 1985.

ore guides
UF	guides, ore
RT	metal ores
	mineral exploration
	gossan

ore microscopy
UF	microscopy, ore
	mineragraphy
RT	metal ores
	microscope methods
	mineralogy
	optical mineralogy
	universal stage

ore minerals
RT	economic geology
	metal ores
	metals
	minerals
	ore-forming fluids
	platinum minerals
	uranium minerals

ore of sedimentation
USE	placers

ore reflectivity
RT	metal ores
	mineral deposits, genesis
	reflectance
SN	Before 1982, reflectivity was used for this term. Added to Thesaurus in 1982.

ore rolls
USE	roll-type deposits

ore sources
SN	As of 1981, no longer a valid term for GeoRef. See mineral deposits, genesis.

ore transport
SN	No longer a valid term for GeoRef. As of 1995, see mineral deposits, genesis for specific natural processes and controls involved, e.g. epigene processes, ore-forming fluids. Before 1978, ore deposits AND transport was used.

ore-forming fluids
UF	fluids, ore-forming
RT	mineral deposits, genesis
	hydrothermal alteration
	mineralization
	ore minerals
SN	Before 1981, also search mineralizers; hydrothermal solutions; hydrothermal fluids.

Oread Limestone
BT	Chronostratigraphic Units
	.Phanerozoic
	..Paleozoic
	...Carboniferous
	....Pennsylvanian
	.....Upper Pennsylvanian
	......Virgilian
	.......Oread Limestone
RT	Iowa
	Missouri
	Oklahoma
	Nebraska
	Kansas
	Shawnee Group
	Plattsmouth Limestone Member
SN	In Shawnee Group. Includes Toronto Limestone, Snyderville Shale, Leavenworth Limestone, Heebner Shale, Plattsmouth Limestone, Heumader Shale, Kereford Limestone members. SW Iowa, E Kansas, NW Missouri, SE Nebraska, and N Oklahoma.

orebodies, hidden
USE	blind deposits

Orebro Sweden
BT	Europe
	.Western Europe
	..Scandinavia
	...Sweden
	....Orebro Sweden
NT	Stripa region
UF	Oerebro Sweden
RT	Bergslagen
SN	County and city in S central Sweden.

Oregon
BT	United States
	.Oregon
NT	Baker County Oregon
	Benton County Oregon
	Brothers fault zone
	Clackamas County Oregon
	Clatsop County Oregon
	Columbia County Oregon
	Coos County Oregon
	Crook County Oregon
	Curry County Oregon
	Deschutes County Oregon
	Douglas County Oregon
	Gilliam County Oregon
	Grant County Oregon
	Harney County Oregon
	Hood River County Oregon
	Jackson County Oregon
	Jefferson County Oregon
	Josephine County Oregon
	Klamath County Oregon
	Lake County Oregon
	Lane County Oregon
	Lincoln County Oregon
	Linn County Oregon
	Malheur County Oregon
	Marion County Oregon
	Morrow County Oregon
	Mount Hood
	Multnomah County Oregon
	Polk County Oregon
	Rogue River
	Sherman County Oregon
	Tillamook County Oregon
	Umatilla County Oregon
	Union County Oregon
	Wallowa County Oregon
	Wallowa Mountains
	Wasco County Oregon
	Washington County Oregon
	Wheeler County Oregon
	Willamette River
	Willamette Valley
	Yamhill County Oregon
RT	Astoria

Oregon County Missouri
BT	United States
	.Missouri
	..Oregon County Missouri

Orenburg Russian Federation
BT	Commonwealth of Independent States
	.Russian Federation
	..Orenburg Russian Federation
BT	Europe
	.Orenburg Russian Federation
NT	Blyava
	Orsk Russian Federation
	Romashkino Field
	Sakmara Russian Federation
UF	Chkalov Russian Federation
RT	Ural region
	Sakmara Zone
SN	Oblast and city in the Southern Urals in European Russian Federation. Before 1993, also search Chkalov Russian Republic. This term has multiple hierarchies. Indexed with Europe if applicable.

Orense City Spain
BT	Europe
	.Southern Europe
	..Iberian Peninsula
	...Spain
	....Galicia Spain
	.....Orense Spain
	......Orense City Spain
SN	Refers to only the city in NW Spain. Before 1993, also search Orense Spain.

Orense Spain
BT	Europe
	.Southern Europe
	..Iberian Peninsula
	...Spain
	....Galicia Spain
	.....Orense Spain
NT	Orense City Spain
SN	Refers only to the province in NW Spain. From 1981-1992, also search Orense Province and Spain. For the city, see Orense City Spain.

ores
SN	Not a valid term for GeoRef. Use specific commodity terms (see list C) or mineral resources or mineral deposits, genesis.

ores in sedimentary rocks
SN	A valid term through 1973. Use sedimentary rocks or sedimentation in conjunction with the individual ore (list C).

ores, polymetallic
USE	polymetallic ores

Oresund
BT	Atlantic Ocean
	.North Atlantic
	..Oresund
RT	Baltic Sea
	Sweden
	Denmark
	Kattegat
SN	Strait connecting the Kattegat with the Baltic Sea. Indexed with Kattegat and/or Baltic Sea as applicable.

organic
SN	A valid term through 1977. As of 1998, use organic compounds if applicable.

organic acids
BT	organic compounds
	.organic acids
NT	amino acids
	carboxylic acids
	fatty acids
	fulvic acids
	humic acids
RT	acids
	DNA
	inorganic acids
	RNA
	ketones
SN	May be used for groups of several organic acids or when more specific term is not known. Added to Thesaurus in 1981.

organic carbon
BT	carbon
	.organic carbon
RT	organic compounds
	total organic carbon
	carbon cycle
SN	Also search organic compounds AND carbon.

organic compounds
NT	acetate
	alcohols
	carbohydrates
	chlorophenols
	dioxins
	esters
	fullerenes
	halogenated hydrocarbons
	humates
	hydrocarbons
	isoprenoids
	ketones
	lignin
	organic acids
	peptides
	phenols
	pigments
	proteins
	sapropel
	sporopollenin
	steroids
	total organic carbon
	volatile organic compounds
RT	anthraxolite
	asphalt
	biochemistry
	biomarkers
	bitumens
	carbon
	carbonaceous composition
	caustobiolith
	chelation
	chitin
	clathrates
	coal
	color alteration index
	complexing
	compounds
	creosote
	crude oil
	epimerization
	gas sands
	gasoline
	gilsonite
	grahamite
	humic
SN	Compounds may be naturally occurring or manufactured. For economic deposits, use petroleum, coal or other appropriate commodity terms in list C. For minerals, use organic minerals. See sedimentary rocks or sediments for discussions of their organic compos

organic materials
SN	No longer a valid term for GeoRef. Was used for discussions of naturally occurring organic materials before 1998. Now use organic compounds. For economic deposits, use petroleum, coal or other appropriate commodity terms in list C. For minerals, search or

organic minerals
NT	amber
	ozocerite
RT	gilsonite
	grahamite
	organic compounds
	porphyrins

organic mound
USE	bioherms

organic nitrogen
BT	nitrogen
	.organic nitrogen
RT	organic compounds
SN	Also search organic compounds AND nitrogen.

organic residues
SN	No longer a valid term for GeoRef. As of 1998, see sediments or sedimentary rocks. From 1978-1997, this term was used in hierarchies with both sediments and sedimentary rocks. From 1981-1992, macerals was used as a narrower term. Before 1981, organic sedi

organic sediments
SN	As of 1981, no longer a valid term for GeoRef. Use sediments. Term was introduced in 1976.

organic sulfur
BT	sulfur
	.organic sulfur
RT	organic compounds
SN	Before 1998, also search organic compounds AND sulfur. Added to Thesaurus in 1993.

organisms
USE	biota

organization
RT	academic institutions
	associations
	government agencies
	museums
	survey organizations
	symposia

organo-metallic complexes
USE	organo-metallics

organo-metallic compounds
USE	organo-metallics

organo-metallics
UF	organo-metallic complexes
	organo-metallic compounds
RT	geochemistry
	organic compounds
	porphyrins
	ligands
	methylmercury
SN	Added to Thesaurus in 1981.

Orgon III
RT	Atlantic Ocean
	expeditions
	marine geology
	marine sediments
	oceanography
SN	Oceanographic expedition. Added to Thesaurus in 1985.

Orgueil Meteorite
BT	meteorites
	.stony meteorites
	..chondrites
	...carbonaceous chondrites
	....Orgueil Meteorite
UF	Montauban Meteorite
RT	France
	Tarn-et-Garonne France
SN	Before 1981, also search Montauban AND meteorites; Orgueil AND meteorites. Added to Thesaurus in 1981.

orientation
RT	dip
	discordant folds
	drag folds
	fabric
	faults
	folds
	horizontal orientation
	inclined folds
	linear orientation
	lineation
	nappes
	navigation
	oblique orientation
	overturned folds
	petrofabrics
	plunging folds
	preferred orientation
	recumbent folds
	schistosity
	str
SN	Includes use as attitude of fold elements with respect to external coordinates.

Oriente
SN	No longer a valid term for GeoRef. See Santiago de Cuba.

Oriente Cuba
USE	Santiago de Cuba

origin
SN	A valid index term through 1977 used in combination with life. Before 1971, was used sometimes used alone or in combination with ore deposits or mineral deposits (i.e. ore deposits, origin; mineral deposits, origin). Also see provenance or genesis or pedo

Orin

Orinoco Basin
USE	Orinoco River basin

Orinoco Belt
BT	South America
	.Venezuela
	..Orinoco Belt
RT	Cerro Negro
SN	Petroliferous region in Venezuela. Added to Thesaurus in 1989.

Orinoco Delta
BT	South America
	.Venezuela
	..Orinoco Delta
UF	Orinoco River delta
RT	Orinoco River
SN	On Atlantic Ocean in Delta Amacuro Territory, NE Venezuela. Added to Thesaurus in 1989.

Orinoco River
BT	South America
	.Orinoco River
RT	Colombia
	Venezuela
	Amazonas Brazil
	Amazonas Colombia
	Amazonas Venezuela
	Anzoategui Venezuela
	Bolivar Venezuela
	Orinoco River basin
	Guarico Venezuela
	Monagas Venezuela
	Orinoco Delta
SN	Rises in the Serra Parima of S Venezuela, flows W across Amazonas, then flows N along the Colombia-Venezuela border, turns E in central Venezuela and empties through a wide delta into the Atlantic Ocean. Also search Orinoco. Indexed with countries as appl

Orinoco River basin
BT	South America
	.Orinoco River basin
UF	Orinoco Basin
RT	Colombia
	Venezuela
	Orinoco River
	Llanos
SN	Drainage basin of the Orinoco River. Indexed with countries as applicable. Added to Thesaurus in 1989.

Orinoco River delta
USE	Orinoco Delta

Oriskany Sandstone
BT	Chronostratigraphic Units
	.Phanerozoic
	..Paleozoic
	...Devonian
	....Lower Devonian
	.....Oriskany Sandstone
RT	Virginia
	Pennsylvania
	New York
	Maryland
	West Virginia
SN	Comprises Shriver Chert, and Ridgeley Sandstone Member. W Maryland, New York, Pennsylvania, Western Virginia and E West Virginia.

Orissa India
BT	Asia
	.Indian Peninsula
	..India
	...Orissa India
NT	Balasore India
	Bolangir India
	Cuttack India
	Dhenkanal India
	Keonjhar India
	Koraput India
	Mayurbhanj India
	Sambalpur India
	Talchir
	Talchir coal field
RT	Deccan Plateau
	Singhbhum Granite
	Singhbhum shear zone
	Gangpur Series
	Kamthi Formation
	Mahanadi Valley
	Rampur coal field
	Talchir Series
SN	State on the Bay of Bengal in E India.

Orivesi Finland
BT	Europe
	.Western Europe
	..Scandinavia
	...Finland
	....Western Finland Province
	.....Orivesi Finland
SN	Town, SW central Finland. Before 1998, may also have been used for an administrative region.

Orizaba, Pico de
USE	Pico de Orizaba

Orkney Islands
BT	Europe
	.Western Europe
	..United Kingdom
	...Great Britain
	....Scotland
	.....Orkney Islands
UF	Orkney region Scotland
RT	Atlantic Ocean Islands
	South Orkney Islands
	Orcadian Basin
SN	Archipelago off NE coast of Scotland.

Orkney region Scotland
USE	Orkney Islands

Orleans County New York
BT	United States
	.New York
	..Orleans County New York

Orleans County Vermont
BT	United States
	.Vermont
	..Orleans County Vermont

Orleans France
BT	Europe
	.Western Europe
	..France
	...Loiret France
	....Orleans France
SN	City in N central France.

Orleans Parish Louisiana
BT	United States
	.Louisiana
	..Orleans Parish Louisiana
NT	New Orleans Louisiana
SN	SE Louisiana, coextensive with New Orleans.

Orlov Russian Federation
BT	Commonwealth of Independent States
	.Russian Federation
	..Orlov Russian Federation
RT	Vyatka Russian Federation
SN	Old name for city of Khalturin just W of Vyatka in Vyatka Oblast of European Russian Federation. May occur in other locations. Before 1993, Orlov Russian Republic was also used. Indexed with oblast as applicable.

ornamental materials
RT	Carrara Marble
	ceramic materials
	clays
	construction materials
	granite deposits
	jadeite
	limestone deposits
	marble deposits
	materials
	rhodonite
SN	May be used as a commodity term with terms such as granite deposits, limestone deposits, marble deposits and construction materials. Added to Thesaurus in 1982.

ornamentation
RT	paleontology
	shells

Orne France
BT	Europe
	.Western Europe
	..France
	...Orne France
NT	Mortagne France
RT	Normandy
	Eure Valley
SN	Department in NW France.

Ornithischia
BT	Chordata
	.Vertebrata
	..Tetrapoda
	...Reptilia
	....Diapsida
	.....Archosauria
	......Ornithischia
BT	Chordata
	.Vertebrata
	..Tetrapoda
	...Reptilia
	....dinosaurs
	.....Ornithischia
NT	Ankylosauria
	Ceratopsia
	Ornithopoda
	Stegosaurus
SN	Order. This term has multiple hierarchies.

Ornithopoda
BT	Chordata
	.Vertebrata
	..Tetrapoda
	...Reptilia
	....Diapsida
	.....Archosauria
	......Ornithischia
	.......Ornithopoda
NT	Hadrosauridae
SN	This term has multiple hierarchies.

ORNL
USE	Oak Ridge National Laboratory

oroclines
BT	orogenic belts
	.oroclines
RT	tectonics
	plate tectonics
SN	Orogenic belts that curve sharply, possibly due to horizontal bending of the crust. Added to Thesaurus in 1989.

Orocopia Schist
BT	Chronostratigraphic Units
	.Phanerozoic
	..Mesozoic
	...Orocopia Schist
RT	California
	Arizona
SN	S California and SW Arizona. Added to Thesaurus in 1989.

orogenesis
USE	orogeny

orogenic belts
NT	oroclines
RT	clastic wedges
	fold and thrust belts
	fold belts
	foreland basins
	forelands
	geosynclines
	intracontinental belts
	mobile belts
	orogeny
	tectonics
SN	Added to Thesaurus in 1981.

orogeny
UF	orogenesis
	tectogenesis
RT	absolute age
	Acadian Phase
	Antler Orogeny
	Alice Springs Orogeny
	Alleghany Orogeny
	Alpine Orogeny
	Andean Orogeny
	Appalachian Phase
	Cadomian Orogeny
	Assyntic Orogeny
	Asturian Orogeny
	Avalonian Orogeny
	back-arc basins
	Baikalian Phase
	Caledonian Orogeny
	Cimme
SN	Used for discussions of either individual orogenies or detailed general treatments on several orogenies. Before 1974, also search mountain building. Before 1981, also search diastrophism if applicable.

Orogrande Basin
BT	United States
	.Orogrande Basin
RT	New Mexico
	Texas
	Sierra County New Mexico
	Dona Ana County New Mexico
	El Paso County Texas
	Hudspeth County Texas
	Otero County New Mexico
	Socorro County New Mexico
	Lincoln County New Mexico
SN	Petroleum-producing region in S New Mexico and W Texas. Indexed with states and counties as applicable. Added to Thesaurus in 1989.

Oronto Group
BT	Chronostratigraphic Units
	.Precambrian
	..Proterozoic
	...Oronto Group
RT	Wisconsin
	Minnesota
	Michigan
	Freda Sandstone
	Nonesuch Shale
SN	Keweenawan. Includes Freda Sandstone. Added to Thesaurus in 1989.

Orosei
BT	Mediterranean Sea
	.West Mediterranean
	..Tyrrhenian Sea
	...Orosei
RT	Sardinia Italy
SN	Gulf of Tyrrhenian Sea. As of 1993, see Orosei Italy for the village.

Orosei Italy
BT	Europe
	.Southern Europe
	..Italy
	...Sardinia Italy
	....Orosei Italy
SN	Village in Sardinia.

Orosian
BT	Chronostratigraphic Units
	.Precambrian
	..Proterozoic
	...Paleoproterozoic
	....Orosian

Oroville California
BT	United States
	.California
	..Butte County California
	...Oroville California
SN	City in N California. Site of August, 1975 earthquake.

Oroville Dam
BT	United States
	.California
	..Butte County California
	...Oroville Dam
RT	Feather River
SN	Earth fill dam on Feather River which forms Oroville Reservoir in Butte County of N central California. Also search (Oroville Reservoir OR reservoirs OR dams) AND Oroville California.

Oroville earthquake 1975
BT	earthquakes
	.Oroville earthquake 1975
RT	California
	Butte County California
SN	Butte County, N California. Added to Thesaurus in 1989.

Orozco fracture zone
BT	Pacific Ocean
	.North Pacific
	..Northeast Pacific
	...Orozco fracture zone
RT	East Pacific Rise
SN	East Pacific Rise, E Pacific. This term has multiple hierarchies. Added to Thesaurus in 1989.

orpiment
BT	sulfides
	.orpiment
UF	yellow arsenic

Orr Formation
BT	Chronostratigraphic Units
	.Phanerozoic
	..Paleozoic
	...Cambrian
	....Upper Cambrian
	.....Orr Formation
RT	Utah
SN	W Utah. Added to Thesaurus in 1985.

Orsha Belarus
BT	Europe
	.Belarus
	..Orsha Belarus
SN	City in Vitebsk Oblast in N Belarus. This term has multiple hierarchies.

Orsk Russian Federation
BT	Commonwealth of Independent States
	.Russian Federation
	..Orenburg Russian Federation
	...Orsk Russian Federation
SN	City in Orenburg Oblast in Southern Urals near the Kazakh border. Before 1993, Orsk Russian Republic was also used. This term has multiple hierarchies.

Ortega Group
BT	Chronostratigraphic Units
	.Precambrian
	..Proterozoic
	...Ortega Group
RT	New Mexico
SN	N New Mexico. Added to Thesaurus in 1989.

Orthida
BT	Invertebrata
	.Brachiopoda
	..Articulata
	...Orthida
NT	Enteletacea

orthite
USE	allanite

ortho-amphibolite
USE	orthoamphibolite

orthoamphibole
BT	silicates
	.chain silicates
	..amphibole group
	...orthoamphibole
NT	anthophyllite
	gedrite
	holmquistite

orthoamphibolite
BT	metamorphic rocks
	.amphibolites
	..orthoamphibolite
UF	ortho-amphibolite

orthoclase
BT	silicates
	.framework silicates
	..feldspar group
	...alkali feldspar
	....orthoclase
RT	adularia
	K-feldspar
	anorthoclase
	sanidine

orthoenstatite
USE	enstatite

orthogneiss
BT	metamorphic rocks
	.gneisses
	..orthogneiss
SN	Added to Thesaurus in 1981.

Orthoptera
BT	Invertebrata
	.Arthropoda
	..Mandibulata
	...Insecta
	....Pterygota
	.....Neoptera
	......Exopterygota
	.......Orthoptera
RT	Orthopteroida
SN	Order. Also search Orthopteroida if applicable.

Orthopteroida
BT	Invertebrata
	.Arthropoda
	..Mandibulata
	...Insecta
	....Pterygota
	.....Neoptera
	......Orthopteroida
RT	Orthoptera
SN	Also search Orthoptera if applicable.

orthopyroxene
BT	silicates
	.chain silicates
	..pyroxene group
	...orthopyroxene
NT	enstatite
	hypersthene
	protoenstatite
RT	orthopyroxenite

orthopyroxenite
BT	igneous rocks
	.plutonic rocks
	..ultramafics
	...orthopyroxenite
RT	websterite
	pyroxenite
	orthopyroxene

orthoquartzite
BT	sedimentary rocks
	.clastic rocks
	..orthoquartzite
UF	orthoquartzitic sandstone
	sedimentary quartzite
RT	sandstone
	terrigenous materials
	ferruginous quartzite
	quartzites
	quartz arenite

orthoquartzitic sandstone
USE	orthoquartzite

orthorhombic
USE	orthorhombic system

orthorhombic system
BT	crystal systems
	.orthorhombic system
UF	orthorhombic
RT	crystallography
SN	Added to Thesaurus in 1985.

orthosilicates
BT	silicates
	.orthosilicates
NT	britholite
	ellenbergerite
	nesosilicates
	sorosilicates
SN	Sorosilicates and nesosilicates.

Orulgan Mountains
BT	Commonwealth of Independent States
	.Russian Federation
	..Yakutia Russian Federation
	...Orulgan Mountains
SN	Extend N and S, E of Lena River in N central Russian Federation. Before 1978, also search Orulgan. This term has multiple hierarchies.

Oruro Bolivia
BT	South America
	.Bolivia
	..Oruro Bolivia
SN	Department and city in W Bolivia on the Chilean border.

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