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NARROW
Format
Article Type
Journal
Publisher
Section
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Africa
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Afar (3)
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East Africa
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Afar Depression (8)
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Ethiopia
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Addis Ababa Ethiopia (1)
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Omo River (1)
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Omo Valley (1)
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Ethiopian Rift (39)
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Kenya
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Kenya Rift valley (1)
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Lake Turkana (1)
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Tanzania (2)
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Turkana Basin (3)
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East African Lakes
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Lake Turkana (1)
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East African Rift (13)
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Gregory Rift (3)
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Nile River (1)
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Southern Africa
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Kaapvaal Craton (1)
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Namaqualand (1)
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South Africa
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KwaZulu-Natal South Africa (1)
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-
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Asia
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Arabian Peninsula
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Saudi Arabia (1)
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Far East
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China (1)
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Himalayas (1)
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Middle East
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Turkey
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East Anatolian Fault (1)
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Tibetan Plateau (1)
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Indian Ocean
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Arabian Sea
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Gulf of Aden (2)
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Red Sea
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Red Sea Rift (1)
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-
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South America
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Brazil
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Bahia Brazil
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Reconcavo Basin (1)
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Tucano Basin (1)
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commodities
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construction materials
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building stone (1)
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geothermal energy (1)
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elements, isotopes
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isotope ratios (2)
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isotopes
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radioactive isotopes
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Ar-40/Ar-39 (1)
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Pb-206/Pb-204 (1)
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Pb-207/Pb-204 (1)
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Pb-208/Pb-204 (1)
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stable isotopes
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Ar-40/Ar-39 (1)
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He-4/He-3 (1)
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Nd-144/Nd-143 (1)
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Pb-206/Pb-204 (1)
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Pb-207/Pb-204 (1)
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Pb-208/Pb-204 (1)
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Sr-87/Sr-86 (2)
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metals
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alkaline earth metals
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strontium
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Sr-87/Sr-86 (2)
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lead
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Pb-206/Pb-204 (1)
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Pb-207/Pb-204 (1)
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Pb-208/Pb-204 (1)
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rare earths
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neodymium
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Nd-144/Nd-143 (1)
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noble gases
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argon
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Ar-40/Ar-39 (1)
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helium
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He-4/He-3 (1)
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fossils
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Chordata
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Vertebrata
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Tetrapoda
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Mammalia
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Theria
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Eutheria
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Primates
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Hominidae
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Homo
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Homo sapiens (1)
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simians (1)
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geochronology methods
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Ar/Ar (5)
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K/Ar (5)
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Rb/Sr (1)
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geologic age
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Cenozoic
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Koobi Fora Formation (1)
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Omo Group (1)
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Quaternary
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Holocene
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Mesolithic (1)
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Neolithic (1)
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Pleistocene
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upper Pleistocene (1)
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Shungura Formation (1)
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Stone Age
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Mesolithic (1)
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Neolithic (1)
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Paleolithic
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Acheulian (1)
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Tertiary
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Neogene
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Miocene (2)
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Pliocene (2)
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Paleogene
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Eocene
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upper Eocene (1)
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Oligocene (3)
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Precambrian (1)
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igneous rocks
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igneous rocks
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plutonic rocks
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ultramafics
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peridotites
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harzburgite (1)
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lherzolite (1)
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pyroxenite
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websterite (1)
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volcanic rocks
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basalts
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alkali basalts (1)
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flood basalts (2)
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glasses (1)
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pyroclastics
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ignimbrite (1)
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pumice (1)
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tuff (1)
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trachyandesites (1)
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volcanic ash (1)
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minerals
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silicates
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chain silicates
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pyroxene group
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clinopyroxene (1)
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framework silicates
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feldspar group (1)
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orthosilicates
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nesosilicates
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olivine group
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olivine (1)
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Primary terms
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absolute age (7)
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Africa
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Afar (3)
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East Africa
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Afar Depression (8)
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Ethiopia
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Addis Ababa Ethiopia (1)
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Omo River (1)
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Omo Valley (1)
-
-
Ethiopian Rift (39)
-
Kenya
-
Kenya Rift valley (1)
-
-
Lake Turkana (1)
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Tanzania (2)
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Turkana Basin (3)
-
-
East African Lakes
-
Lake Turkana (1)
-
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East African Rift (13)
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Gregory Rift (3)
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Nile River (1)
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Southern Africa
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Kaapvaal Craton (1)
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Namaqualand (1)
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South Africa
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KwaZulu-Natal South Africa (1)
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-
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Asia
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Arabian Peninsula
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Saudi Arabia (1)
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Far East
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China (1)
-
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Himalayas (1)
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Middle East
-
Turkey
-
East Anatolian Fault (1)
-
-
-
Tibetan Plateau (1)
-
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catalogs (1)
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Cenozoic
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Koobi Fora Formation (1)
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Omo Group (1)
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Quaternary
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Holocene
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Mesolithic (1)
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Neolithic (1)
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Pleistocene
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upper Pleistocene (1)
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-
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Shungura Formation (1)
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Stone Age
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Mesolithic (1)
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Neolithic (1)
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Paleolithic
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Acheulian (1)
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-
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Tertiary
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Neogene
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Miocene (2)
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Pliocene (2)
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-
Paleogene
-
Eocene
-
upper Eocene (1)
-
-
Oligocene (3)
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-
-
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Chordata
-
Vertebrata
-
Tetrapoda
-
Mammalia
-
Theria
-
Eutheria
-
Primates
-
Hominidae
-
Homo
-
Homo sapiens (1)
-
-
-
simians (1)
-
-
-
-
-
-
-
-
conservation (1)
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construction materials
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building stone (1)
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continental drift (1)
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crust (7)
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crystal chemistry (1)
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data processing (1)
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deformation (5)
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earthquakes (7)
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engineering geology (1)
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explosions (1)
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faults (12)
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fractures (4)
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geochemistry (1)
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geochronology (2)
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geomorphology (2)
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geophysical methods (3)
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geothermal energy (1)
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ground water (2)
-
igneous rocks
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plutonic rocks
-
ultramafics
-
peridotites
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harzburgite (1)
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lherzolite (1)
-
-
pyroxenite
-
websterite (1)
-
-
-
-
volcanic rocks
-
basalts
-
alkali basalts (1)
-
flood basalts (2)
-
-
glasses (1)
-
pyroclastics
-
ignimbrite (1)
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pumice (1)
-
tuff (1)
-
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trachyandesites (1)
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-
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inclusions
-
fluid inclusions (1)
-
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Indian Ocean
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Arabian Sea
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Gulf of Aden (2)
-
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Red Sea
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Red Sea Rift (1)
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-
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intrusions (3)
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isotopes
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radioactive isotopes
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Ar-40/Ar-39 (1)
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Pb-206/Pb-204 (1)
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Pb-207/Pb-204 (1)
-
Pb-208/Pb-204 (1)
-
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stable isotopes
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Ar-40/Ar-39 (1)
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He-4/He-3 (1)
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Nd-144/Nd-143 (1)
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Pb-206/Pb-204 (1)
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Pb-207/Pb-204 (1)
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Pb-208/Pb-204 (1)
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Sr-87/Sr-86 (2)
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lava (2)
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lineation (1)
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magmas (4)
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mantle (3)
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metals
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alkaline earth metals
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strontium
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Sr-87/Sr-86 (2)
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-
-
lead
-
Pb-206/Pb-204 (1)
-
Pb-207/Pb-204 (1)
-
Pb-208/Pb-204 (1)
-
-
rare earths
-
neodymium
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Nd-144/Nd-143 (1)
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-
-
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metasomatism (1)
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Mohorovicic discontinuity (1)
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noble gases
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argon
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Ar-40/Ar-39 (1)
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helium
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He-4/He-3 (1)
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ocean basins (1)
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paleoclimatology (2)
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paleogeography (1)
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petrology (1)
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phase equilibria (1)
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plate tectonics (18)
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Precambrian (1)
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remote sensing (4)
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rock mechanics (1)
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sea-floor spreading (2)
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sedimentation (2)
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sediments (2)
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seismology (2)
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South America
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Brazil
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Bahia Brazil
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Reconcavo Basin (1)
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Tucano Basin (1)
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springs (1)
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structural analysis (1)
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structural geology (2)
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tectonics
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neotectonics (3)
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tectonophysics (1)
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thermal waters (1)
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volcanology (1)
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sedimentary rocks
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volcaniclastics (1)
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sediments
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sediments (2)
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volcaniclastics (1)
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GeoRef Categories
Era and Period
Epoch and Age
Date
Availability
Ethiopian Rift
Possible Role of Internal Erosion in the Development of Ground Fissures around Lake Ziway, Ethiopia Open Access
Reconciling plate motion and faulting at a rift-rift-rift triple junction Available to Purchase
Tectonic and Paleoclimatic Setting for Hominin Evolution in Eastern Africa Available to Purchase
Formation of magmatic segments within the Aluto-Gedemsa area, Main Ethiopian Rift Available to Purchase
Transverse tectonics control on the Late Quaternary development of the Central Main Ethiopian Rift Available to Purchase
Interactions between propagating rifts and linear weaknesses in the lower crust Open Access
Locations and Source Parameters for Calibration Events in Turkey, Saudi Arabia, Ethiopia, and Tanzania Available to Purchase
Recurrent explosive eruptions from a high-risk Main Ethiopian Rift volcano throughout the Holocene Open Access
Volcanic field elongation, vent distribution, and tectonic evolution of a continental rift: The Main Ethiopian Rift example Open Access
Structural controls on fluid pathways in an active rift system: A case study of the Aluto volcanic complex Open Access
Magma-induced axial subsidence during final-stage rifting: Implications for the development of seaward-dipping reflectors Open Access
From Craton to Rift: Empirically Based Ground‐Truth Criteria for Local Events Recorded on Regional Networks Available to Purchase
Magmatic history of Dabbahu, a composite volcano in the Afar Rift, Ethiopia Available to Purchase
Integrated geological-architectural pilot study of the Biet Gabriel-Rufael rock hewn church in Lalibela, northern Ethiopia Available to Purchase
Q from 1‐Hz Lg Wave and Its Coda in the Northern Main Ethiopian Rift and Afar Available to Purchase
Holocene opening directions along the axes of the Red Sea (Afar) and Main Ethiopian Rifts: An overview Available to Purchase
Assessments of the extension directions and their variations are critical for understanding rifting processes. This study provides an overview of the extension directions along the axes of the Main Ethiopian Rift and the Red Sea Rift (or propagator) of Afar, two of the three rifts meeting at the Afar triple junction. This overview is based on new and published field data on the opening direction of significant (width >0.2 m) Holocene extension fractures along the rift axis. The data show that the Red Sea propagator axis opens orthogonally, both in northern and central Afar, even though a significant strike-slip component is recognized at the rift margins in central Afar. The Main Ethiopian Rift axis also opens orthogonal to the trend of the rift, which varies between the different rift segments. Therefore, the axes of two of the three rifts meeting in Afar are characterized by orthogonal extension. However, given the variable orientations of the rift segments, the obtained opening directions are usually not uniform along the rift. Current plate-motion models suggest slightly different divergence directions, especially along the Main Ethiopian Rift, which shows a significant oblique component. The discrepancy between the data along the rift axis and those from plate-motion models suggests an across-rift strain partitioning. The observed orthogonal extension along the rift axis may be magma-induced, provided that a depth-dependent variation in the kinematics exists, at least below the Main Ethiopian Rift axis.
The Ethiopia Afar Geoscientific Lithospheric Experiment (EAGLE): Probing the transition from continental rifting to incipient seafloor spreading Available to Purchase
The Miocene–Holocene East African Rift in Ethiopia is unique worldwide because it subaerially exposes the transition between continental rifting and seafloor spreading within a young continental flood basalt province. As such, it is an ideal study locale for continental breakup processes and hotspot tectonism. Here, we review the results of a recent multidisciplinary, multi-institutional effort to understand geological processes in the region: the Ethiopia Afar Geoscientific Lithospheric Experiment (EAGLE). In 2001–2003, dense broadband seismological networks probed the structure of the upper mantle, while controlled-source wide-angle profiles illuminated both along-axis and across-rift crustal structure of the Main Ethiopian Rift. These seismic experiments, complemented by gravity and magnetotelluric surveys, provide important constraints on variations in rift structure, deformation mechanisms, and melt distribution prior to breakup. Quaternary magmatic zones at the surface within the rift are underlain by high-velocity, dense gabbroic intrusions that accommodate extension without marked crustal thinning. A magnetotelluric study illuminated partial melt in the Ethiopian crust, consistent with an overarching hypothesis of magma-assisted rifting. Mantle tomographic images reveal an ~500-km-wide low-velocity zone at ≥75 km depth in the upper mantle that extends from close to the eastern edge of the Main Ethiopian Rift westward beneath the uplifted and flood basalt–capped NW Ethiopian Plateau. The low-velocity zone does not interact simply with the Miocene–Holocene (rifting-related) base of lithosphere topography, but it provides an abundant source of partially molten material that assists extension of the seismically and volcanically active Main Ethiopian Rift to the present day.
Peridotite xenoliths from Ethiopia: Inferences about mantle processes from plume to rift settings Available to Purchase
A comprehensive petrological study carried out on Ethiopian mantle xenoliths entrained in Neogene–Quaternary alkaline lavas overlying the continental flood basalt area (Dedessa River–Wollega region, Injibara-Gojam region) and from the southern Main Ethiopian Rift (Mega-Sidamo region) provides an ideal means to investigate mantle evolution from plume to rift settings. Mantle xenoliths from the plateau area (Injibara, Dedessa River) range in composition from spinel lherzolite to harzburgite and olivine websterite, showing pressure-temperature ( P-T ) equilibrium conditions in the range 1.3–0.9 GPa and 950–1050 °C. These xenoliths show flat chondrite (ch)–normalized bulk-rock rare earth element (REE) patterns, with only few light (L) REE–enriched samples (La N /Yb N up to 7) in the most refractory lithotypes. Clinopyroxene (cpx) REE patterns are mostly LREE depleted (La N /Yb N down to 0.2) or enriched (La N /Yb N up to 4.4). Sr-Nd isotopes of clinopyroxene mainly show compositions approaching the depleted mantle (DM) end member ( 87 Sr/ 86 Sr < 0.7030; 143 Nd/ 144 Nd > 0.5132), or less depleted values ( 87 Sr/ 86 Sr = 0.7033–0.7034; 143 Nd/ 144 Nd = 0.5129–0.5128) displaced toward the enriched mantle components that characterize the Afar plume signature and the related Ethiopian Oligocene continental flood basalts. The 3 He/ 4 He (R a ) values of olivines range from 6.6 to 8.9 R a , overlapping typical depleted mantle values. These characteristics suggest that most xenoliths reflect complex asthenosphere-lithosphere interactions due to refertilization processes by mafic subalkaline melts that infiltrated and reacted with the pristine peridotite parageneses, ultimately leading to the formation of olivine-websterite domains. On the other hand, mantle xenoliths from the southern Main Ethiopian Rift (Mega-Sidamo region) consist of spinel lherzolite to harzburgites showing various degree of deformation and recrystallization, coupled with a wider range of P-T equilibrium conditions, from 1.6 ± 0.4 GPa and 1040 ± 80 °C to 1.0 ± 0.2 GPa and 930 ± 80 °C. Bulk-rock REE patterns show generally flat heavy (H) REEs, ranging from 0.1 chondritic values in harzburgites up to twice chondritic abundances in fertile lherzolites, and are variably enriched in LREE, with La N /Yb N up to 26 in the most refractory lithologies. The constituent clinopyroxenes have flat HREE distributions and La N /Yb N between 0.1 and 76, i.e., in general agreement with the respective bulk-rock chemistry. Clinopyroxenes from lherzolites have 87 Sr/ 86 Sr = 0.7022–0.7031, 143 Nd/ 144 Nd = 0.5130–0.5138, and 206 Pb/ 204 Pb = 18.38–19.34, and clinopyroxenes from harzburgites have 87 Sr/ 86 Sr = 0.7027–0.7033, 143 Nd/ 144 Nd = 0.5128–0.5130, and 206 Pb/ 204 Pb = 18.46–18.52. These range between the DM and high-μ (HIMU) mantle end members. The helium isotopic composition varies between 7.1 and 8.0 R a , comparable to the xenoliths from the plateau area. Regional comparison shows that HIMU-like alkali-silicate melt(s), variably carbonated, were among the most effective metasomatizing agent(s) in mantle sections beneath the southern Main Ethiopian Rift, as well as along the Arabian rifted continental margins and the whole East African Rift system. The different types of metasomatic agents recorded in Ethiopian mantle xenoliths from the continental flood basalt area and the rift systems clearly reflect distinct tectonomagmatic settings, i.e., plume-related subalkaline magmatism and rift-related alkaline volcanism, with the latter extending far beyond the influence of the Afar plume.