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NARROW
GeoRef Subject
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all geography including DSDP/ODP Sites and Legs
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Atlantic Ocean Islands
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Azores (1)
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Canary Islands
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Hierro (2)
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elements, isotopes
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carbon
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C-13/C-12 (1)
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C-14 (2)
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isotope ratios (2)
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isotopes
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radioactive isotopes
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C-14 (2)
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stable isotopes
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C-13/C-12 (1)
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S-34/S-32 (1)
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nitrogen (1)
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oxygen (1)
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sulfur
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S-34/S-32 (1)
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fossils
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Invertebrata
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Mollusca
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Bivalvia (1)
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geologic age
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Cenozoic
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Quaternary
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Holocene (2)
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Mesozoic
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Cretaceous (1)
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igneous rocks
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igneous rocks
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plutonic rocks (1)
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volcanic rocks
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pyroclastics
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ignimbrite (1)
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trachytes (1)
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metamorphic rocks
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turbidite (1)
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minerals
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native elements
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graphite (1)
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silicates (1)
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sulfates
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barite (1)
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Primary terms
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absolute age (2)
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Atlantic Ocean Islands
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Azores (1)
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Canary Islands
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Hierro (2)
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carbon
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C-13/C-12 (1)
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C-14 (2)
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Cenozoic
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Quaternary
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Holocene (2)
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crust (1)
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data processing (1)
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geochemistry (1)
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geomorphology (1)
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heat flow (1)
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igneous rocks
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plutonic rocks (1)
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volcanic rocks
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pyroclastics
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ignimbrite (1)
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trachytes (1)
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inclusions
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fluid inclusions (2)
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Invertebrata
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Mollusca
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Bivalvia (1)
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-
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isotopes
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radioactive isotopes
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C-14 (2)
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stable isotopes
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C-13/C-12 (1)
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S-34/S-32 (1)
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lava (1)
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magmas (2)
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Mesozoic
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Cretaceous (1)
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metasomatism (1)
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nitrogen (1)
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ocean basins (1)
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ocean floors (1)
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oxygen (1)
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plate tectonics (1)
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sea water (1)
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standard materials (1)
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sulfur
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S-34/S-32 (1)
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-
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sedimentary rocks
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turbidite (1)
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volcaniclastics (1)
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sediments
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turbidite (1)
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volcaniclastics (1)
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Volcaniclastic deposits and sedimentation processes around volcanic ocean islands: the central Azores
Abstract Geological histories of volcanic ocean islands can be revealed by the sediments shed by them. Hence there is an interest in studying cores of volcaniclastic sediments that are particularly preserved in the many flat-floored basins lying close to the Azores islands. We analyse four gravity cores collected around the central group of the islands. Three sedimentary facies (F1-F2a, F2b) are recognized based on visual core logging, particle morphometric and geochemical analyses. F1 is clay-rich hemipelagite comprising homogeneous mud with mottled structures from bioturbation. F2a and F2b are both clay-poor volcaniclastic deposits, which are carbonate-rich and carbonate-poor, respectively. More biogenic carbonate in F2a reflects the incorporation of unconsolidated calcareous material from island shelves or bioturbation. Within F2a and F2b we identify deposits emplaced by pyroclastic fallout, primary or secondary turbidity currents by combining multiple information from lithological composition, sedimentary structures, chemical composition of volcanic glass shards and morphometric characteristics of volcanic particles. Primary volcaniclastic sediments were found in all four cores, echoing activity known to have occurred up to historical times on the adjacent islands. These preliminary results suggest that greater details of geological events could be inferred for other volcanic islands by adopting a similar approach to core analysis.