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1
TAKASHIMA, REISHI, HIROSHI NISHI, and TAKEYOSHI YOSHIDA. "Late Jurassic–Early Cretaceous intra-arc sedimentation and volcanism linked to plate motion change in northern Japan." Geological Magazine 143, no. 6 (September 4, 2006): 753–70. http://dx.doi.org/10.1017/s001675680600255x.
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The Sorachi Group, composed of Upper Jurassic ophiolite and Lower Cretaceous island-arc volcano-sedimentary cover, provides a record of Late Jurassic–Early Cretaceous sedimentation and volcanism in an island-arc setting off the eastern margin of the Asian continent. Stratigraphic changes in the nature and volume of the Sorachi Group volcanic and volcaniclastic rocks reveal four tectonic stages. These stages resulted from changes in the subduction direction of the Pacific oceanic plate. Stage I in the Late Jurassic was characterized by extensive submarine eruptions of tholeiitic basalt from the back-arc basin. Slab roll-back caused rifting and sea-floor spreading in the supra-subduction zone along the active Asian continental margin. Stage II corresponded to the Berriasian and featured localized trachyandesitic volcanism that formed volcanic islands with typical island-arc chemical compositions. At the beginning of this stage, movement of the Pacific oceanic plate shifted from northeastward to northwestward. During Stage III, in the Valanginian, submarine basaltic volcanism was followed by subsidence. The Pacific oceanic plate motion turned clockwise, and the plate boundary between the Asian continent and the Pacific oceanic plate changed from convergent to transform. During Stage IV in the Hauterivian–Barremian, in situ volcanism ceased in the Sorachi–Yezo basin, and the volcanic front migrated west of the Sorachi–Yezo basin.
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Le Pera, Emilia, Consuele Morrone, José Arribas, M. Eugenia Arribas, Eumenio Ancochea, and M. José Huertas. "Petrography and provenance of beach sands from volcanic oceanic islands: Cabo Verde, Atlantic Ocean." Journal of Sedimentary Research 91, no. 1 (January 31, 2021): 92–115. http://dx.doi.org/10.2110/jsr.2020.096.
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ABSTRACT Volcaniclastic deposits have been extensively analyzed in several settings in the Pacific and circum-Pacific area. Recent volcaniclastic products from Atlantic oceanic islands offer another opportunity to add new data and be an important key to a better understanding of volcanic imprints on the sedimentary record. The Cabo Verde archipelago is an Atlantic Oceanic plateau with late Oligocene to Holocene volcanism. Outcrops consist mainly of mafic and strongly alkaline and ultra-alkaline volcanic (pyroclastic and lava flows) and less abundant intrusive rocks with minor carbonatites and carbonate sedimentary rocks, constituting a multiple-provenance assemblage for the sandy beaches surrounding the islands. Currently, climate is semiarid to hyperarid with ephemeral and intermittent streams. Thirty-six samples of beach sand from six principal Cabo Verde Islands were selected for petrographic inspection. On average, beach sands constitute a volcanolithic petrofacies. A relative increase in carbonate limeclasts and bioclasts dilutes the pure volcaniclastic contribution mainly on the older island beaches (Sao Vicente, Sal, and Boa Vista). The major components of Cabo Verde beach sands are highly variable; in general, composition is a function of island morphological evolution and age. Thus, beaches of the younger islands (Sao Nicolau, Santiago, and Fogo) consist mainly of volcanic lithic fragments, and monomineralic grains of dense minerals such as olivine, pyroxene, and amphibole, and single grains of plagioclase and anorthoclase. By contrast, beaches of older eastern islands (Sal, Boa Vista, and Sao Vicente) contain more calcareous bioclasts, micritic and/or sparitic sedimentary lithic grains. The presence of carbonate grains suggests provenance from shallow carbonate platforms developed during periods of volcanic quiescence. Cabo Verde volcanic sandy fractions are composed mostly of black, brown, and orange glassy volcanic particles exhibiting microlitic, lathwork, and vitric textures. Volcanic particles with lathwork textures are linked to mafic provenance assemblages (nephelinites, basanites, and tephrites). The content of glassy particles is nearly constant in all beaches, and both hydroclastic and epiclastic processes are reflected in these populations of glassy grains. Boa Vista, Sao Vicente, and Santiago beaches contain higher proportions of sideromelane, linked to recent coastal volcanism, and lower proportions of orange and black glassy particles. The concentration of orange glass particles in the beaches of Santiago Island is higher than in the other island beaches. These orange glassy textures have been preserved even if they were sourced from the intensely altered Ancient Eruptive Complex, representing the pre-Miocene seamount stage of Santiago Island. A very small percentage of altered labile monocrystalline grains such as olivine and the paucity of altered volcanic components reflect the weathering-limited erosion regime of the islands. The exposed phonolitic lava flows that occupy only a minor surface part of the inland source produce particles with microlitic texture in sand beaches. Thus, this texture is not exclusive to andesitic, basaltic, and basaltic andesites sources, suggesting the need for a review of these particles as source-sensitive provenance signals.
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Cumberlidge, Neil. "Insular species of Afrotropical freshwater crabs (Crustacea: Decapoda: Brachyura: Potamonautidae and Potamidae) with special reference to Madagascar and the Seychelles." Contributions to Zoology 77, no. 2 (2008): 71–81. http://dx.doi.org/10.1163/18759866-07702003.
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The evolutionary relationships between island and mainland faunas of the 24 species of insular freshwater crabs in the Afrotropical region are reviewed in the light of phylogenetic studies. Twenty insular species of freshwater crabs are endemic, and four are also found on the neighboring mainland of Africa. The Atlantic Ocean islands of Sherbro, Bioko, Principe, and São Tomé support five species of Potamonautidae, while the Western Indian Ocean islands of the Seychelles, Zanzibar, Pemba, Mafia, and Madagascar together have 16 species of Potamonautidae, and Socotra has three species of Potamidae. Disjunct distributions of non-endemic insular species of Afrotropical freshwater crabs with conspecifics on the mainland are the result of past lower sea levels that once united islands with the coast. The presence of endemic species of freshwater crabs on oceanic volcanic islands (such as Príncipe and São Tomé) separated from the mainland by deep seas is probably the result of transoceanic dispersal. Endemic genera of freshwater crabs found on oceanic ‘Gondwanan’ islands are derived from ancestral populations on the Eurasian (Socotra) or African (The Seychelles and Madagascar) mainlands that probably reached there by transoceanic dispersal, rather than their being the vicariant descendents of Gondwanan ancestors. Species of freshwater crabs found on islands in the Afrotropical region are either not unique, or are endemic at the species or genus level. The degree of endemism depends on the island’s geological history: whether it is part of the continental shelf, an oceanic island of volcanic origin, or a former part of the ancient continent of Gondwana.
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LEAT, P. T., R. D. LARTER, and I. L. MILLAR. "Silicic magmas of Protector Shoal, South Sandwich arc: indicators of generation of primitive continental crust in an island arc." Geological Magazine 144, no. 1 (October 27, 2006): 179–90. http://dx.doi.org/10.1017/s0016756806002925.
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Protector Shoal, the northernmost and most silicic volcano of the South Sandwich arc, erupted dacite–rhyolite pumice in 1962. We report geochemical data for a new suite of samples dredged from the volcano. Geochemically, the dredge and 1962 samples form four distinct magma groups that cannot have been related to each other, and are unlikely to have been related to a single basaltic parent, by fractional crystallization. Instead, the silicic rocks are more likely to have been generated by partial melting of basaltic lower crust within the arc. Trace element and Sr–Nd isotope data indicate that the silicic volcanics have compositions that are more similar to the volcanic arc than the oceanic basement formed at a back-arc spreading centre, and volcanic arc basalts are considered to be the likely source for the silicic magmas. The South Sandwich Islands are one of several intra-oceanic arcs (Tonga–Kermadec, Izu–Bonin) that have: (1) significant amounts of compositionally bimodal mafic–silicic volcanic products and (2) 6.0–6.5 km s−1P-wave velocity layers in their mid-crusts that have been imaged by wide-angle seismic surveys and interpreted as intermediate-silicic plutons. Geochemical and volume considerations indicate that both the silicic volcanics and plutonic layers were generated by partial melting of basaltic arc crust, representing an early stage in the fractionation of oceanic basalt to form continental crust.
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Leat, Philip T., and Teal R. Riley. "Chapter 3.1a Antarctic Peninsula and South Shetland Islands: volcanology." Geological Society, London, Memoirs 55, no. 1 (2021): 185–212. http://dx.doi.org/10.1144/m55-2018-52.
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AbstractThe voluminous continental margin volcanic arc of the Antarctic Peninsula is one of the major tectonic features of West Antarctica. It extends from the Trinity Peninsula and the South Shetland Islands in the north to Alexander Island and Palmer Land in the south, a distance ofc.1300 km, and was related to east-directed subduction beneath the continental margin. Thicknesses of exposed volcanic rocks are up toc.1.5 km, and the terrain is highly dissected by erosion and heavily glacierized. The arc was active from Late Jurassic or Early Cretaceous times until the Early Miocene, a period of climate cooling from subtropical to glacial. The migration of the volcanic axis was towards the trench over time along most of the length of the arc. Early volcanism was commonly submarine but most of the volcanism was subaerial. Basaltic–andesitic stratocones and large silicic composite volcanoes with calderas can be identified. Other rock associations include volcaniclastic fans, distal tuff accumulations, coastal wetlands and glacio-marine eruptions.Other groups of volcanic rocks of Jurassic age in Alexander Island comprise accreted oceanic basalts within an accretionary complex and volcanic rocks erupted within a rift basin along the continental margin that apparently predate subduction.
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Soja, Constance M. "Using fossils to identify allochthonous oceanic islands in the ancient geologic record." Paleontological Society Special Publications 6 (1992): 275. http://dx.doi.org/10.1017/s2475262200008352.
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Silurian organisms preserved in southeastern Alaska (Alexander terrane) inhabited marine environments within an island-arc complex during a phase of waning volcanism and are fossilized in a diversity of shallow-marine platform and deep-water deposits. These fossils exhibit a distinctive suite of characteristics and share fundamental similarities with biotas of Paleozoic-Mesozoic age that are preserved in other accreted island terranes of North America. These special attributes reflect the colonization, evolution, and diversification of marine organisms adjacent to subconical/conical volcanic edifices characterized by relatively high rates of subsidence, steep submarine slopes, tectonic instability, and biogeographic isolation. Recognition of these diagnostic features enables many ancient island faunas to be distinguished from those that lived on the craton and enhances differentiation of island biotas from pelagic assemblages that accumulated as oozes in deep ocean basins.Although island faunas exhibit a high degree of variability in taxonomic diversity, levels of endemism, and provincial affinities, many share a significant number of similarities. Several of these shared attributes reflect organismal evolution in biogeographic isolation at island sites separated from continental and other source regions by considerable geographic distances or at locations unfavorably situated with respect to oceanic currents transporting teleplanic larvae. Comparison of Silurian island-arc faunas from Alaska with coeval assemblages from different tectonic settings and with modern volcanic islands shows that oceanic island biotas commonly are characterized by: (1) initially impoverished, normal marine faunas of low diversity and abundance that are preserved in exceptionally thick platform sequences; (2) sequential development of organic structures from fringing to barrier reefs on the outer shelf during thermal subsidence and lateral expansion of the carbonate platform; (3) restricted faunas devoid of normal marine shelly benthos and tolerant of quiet-water conditions, muddy substrates, and fluctuations in salinity, temperature, and oxygen concentrations in back-reef lagoons; (4) extensive taphonomic redistribution of organisms along bathymetric gradients and downslope preservation in debris flows, slumps, and turbidites of mixed fossil assemblages derived from shelf and shelf-margin habitats; (5) rapid lateral and vertical changes in biofacies, reflecting complex depositional systems in fault-block basins; (6) insular biotas with relatively high levels of endemism; (7) complex paleobiogeographic affinities expressed in assemblages that comprise mixtures of taxa from different faunal regions; and (8) relict biotas that may represent the protracted survival of some organisms in island refugia.Because many accreted islands are poorly preserved and highly deformed, recognizing these distinctive features in oceanic island faunas enhances identification of allochthonous volcanic arcs, seamounts, atolls, and hot-spot islands in the ancient geologic record. Using fossils to identify islands in accreted terranes is especially important when island origins of strata are suspected but difficult to prove because calc-alkaline volcano-plutonic rocks or derivative volcanogenic and quartz-poor siliciclastic deposits are absent or not exposed. Hence, relying on fossils to recognize oceanic islands that survived destructive tectonic processes offers an expanded list of geologic criteria to aid in reconstructing plate boundaries marking ancient zones of convergence and to use in unraveling the tectonic history of ocean basins recorded in suspect terranes.
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Dóniz-Páez, Javier, Esther Beltrán-Yanes, Rafael Becerra-Ramírez, Nemesio M. Pérez, Pedro A. Hernández, and William Hernández. "Diversity of Volcanic Geoheritage in the Canary Islands, Spain." Geosciences 10, no. 10 (September 28, 2020): 390. http://dx.doi.org/10.3390/geosciences10100390.
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Volcanic areas create spectacular landscapes that contain a great diversity of geoheritage. The study of this geoheritage enables us to inventory, characterise, protect and manage its geodiversity. The Canary Islands are a group of subtropical active volcanic oceanic islands with a great variety of magma types and eruption dynamics that give rise to a wide diversity of volcanic features and processes. The aim of this paper is to identify, for the first time, the diversity of volcanic geoheritage of the Canary Islands and to appraise the protection thereof. To this end, a geomorphological classification is proposed, taking into account the features and processes directly related to volcanism, such as those resulting from erosion and sedimentary processes. The main findings demonstrate that the volcanic geoheritage of the Canary Islands is extremely varied and that this geodiversity is safeguarded by regional, national and, international protection and management frameworks. Even so, and given the enormous pressure of coastal tourism on the coastlines of the islands, we believe that continuing efforts should be made to conserve and manage their volcanic and non-volcanic geoheritage, so that these places can continue to be enjoyed in the form of geotourism.
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Liu, Xin, and Dapeng Zhao. "Seismic evidence for a plume-modified oceanic lithosphere–asthenosphere system beneath Cape Verde." Geophysical Journal International 225, no. 2 (January 11, 2021): 872–86. http://dx.doi.org/10.1093/gji/ggab012.
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SUMMARY We determine a new 3-D shear wave velocity (Vs) model down to 400 km depth beneath the Cape Verde hotspot that is far from plate boundaries. This Vs model is obtained by using a new method of jointly inverting P- and S-wave receiver functions, Rayleigh-wave phase-velocity data and S-wave arrival times of teleseismic events. Two Vs discontinuities at ∼15 and ∼60 km depths are revealed beneath volcanic islands, which are interpreted as the Moho discontinuity and the Gutenberg (G) discontinuity. Between the north and south islands, obvious high-Vs anomalies exist in the uppermost mantle down to a depth of ∼100–150 km beneath the Atlantic Ocean, whereas obvious low-Vs anomalies exist in the uppermost mantle beneath the volcanic islands including the active Fogo volcano. These low-Vs anomalies merge into a significant column-like low-Vs zone at depths of ∼150–400 km beneath the Cape Verde swell. We propose that these features in the upper mantle reflect a plume-modified oceanic lithosphere–asthenosphere system beneath the Cape Verde hotspot.
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Johnson, Markes E., and B. Gudveig Baarli. "Charles Darwin in the Cape Verde and Galápagos archipelagos: The role of serendipity in development of theories on the ups and downs of oceanic islands." Earth Sciences History 34, no. 2 (January 1, 2015): 220–42. http://dx.doi.org/10.17704/1944-6187-34.2.220.
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The 1831–1836 voyage of H.M.S. Beagle under Captain Robert FitzRoy launched Charles Darwin's entry into the world of geology with two pioneering publications on oceanic islands to his credit. Best known is Darwin's 1842 contribution on the theory of atoll development from the subsidence of volcanic islands and coeval upward growth of coral reefs. This work can be linked, in part, to the ten days during which the Beagle visited the Keeling (Cocos) Islands. The subsequent and lesser known of Darwin's parallel contributions is his 1844 summary on all the volcanic islands visited during the expedition, including Santiago (Cape Verde Islands), Terceira (Azores), St. Paul's Rocks, Fernando Noronha, Ascension, St. Helena, the Galápagos Islands, Tahiti, and Mauritius. Ostensibly, the centerpiece of the 1844 volume is Darwin's extensive coverage of Ascension based on the five days spent there in 1836. However, Darwin had many more days at his disposal in the Galápagos and ‘St. Jago’ (Santiago), where the Beagle stopped in the Cape Verde Islands at the outset and again near the end of the voyage. The volcanic islands where Darwin spent the most time were in the Galápagos (thirty-five days) and the Cape Verdes (twenty-nine days). In particular, those island groups make an interesting comparison with respect to the development of Darwin's ideas on tectonic uplift based on basalt flows with inter-bedded limestone formations. Chance played a huge role in what Darwin saw and did not see during his island travels. The initial visit to the Cape Verde islands was instrumental in shaping Darwin's earliest vision of a book on volcanic islands, but his time there was entirely fortuitous due to a forced change in FitzRoy's plan for a stay in the Canary Islands. Although Darwin was on the look out for limestone formations in the Galápagos islands comparable to those on Santiago in the Cape Verdes, he missed finding them due only to the vagaries of FitzRoy's charting schedule in the Galápagos. This overview looks at limestone distribution in the Cape Verde and Galápagos archipelagos as now understood and speculates on how a wider knowledge of both regions may have influenced Darwin's thinking on global patterns of island uplift and subsidence.
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Embry, Ashton F., and Kirk G. Osadetz. "Stratigraphy and tectonic significance of Cretaceous volcanism in the Queen Elizabeth Islands, Canadian Arctic Archipelago." Canadian Journal of Earth Sciences 25, no. 8 (August 1, 1988): 1209–19. http://dx.doi.org/10.1139/e88-118.
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Cretaceous volcanic rocks, which consist mainly of basalt flows and pyroclastic rocks, occur on northern Ellesmere Island, Axel Heiberg Island, and northernmost Amund Ringnes Island as part of the Sverdrup Basin succession. Volcanic rocks are associated with each of four regional transgressive–regressive (T–R) cycles that constitute the Cretaceous clastic succession of Sverdrup Basin and are of Valanginian – early Barremian, late Barremian – Aptian, latest Aptian – early Cenomanian, and late Cenomanian – Maastrichtian age; the volcanic component of each increases northward. The centre of volcanism appears to have been north of Ellesmere Island and is interpreted as the site of a mantle plume that was active throughout the Cretaceous.Most of the volcanic activity took place from Hauterivian to early Cenomanian (T–R cycles 1–3) and was accompanied by widespread sill and dyke intrusion. This activity coincided with the main rifting phase of the adjacent oceanic Canada Basin and with minor crustal extension in the Sverdrup Basin. From late Cenomanian to Campanian, volcanism was restricted to the extreme northeast, and trachytes and rhyolites were extruded along with basalts. This volcanic succession is interpreted as being the southern limit of Alpha Ridge, a major volcanic edifice that formed as a hot-spot track across Canada Basin during sea-floor spreading in Late Cretaceous.
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Blanco-Montenegro, Isabel, Iacopo Nicolosi, Alessandro Pignatelli, and Massimo Chiappini. "Magnetic imaging of the feeding system of oceanic volcanic islands: El Hierro (Canary Islands)." Geophysical Journal International 173, no. 1 (April 2008): 339–50. http://dx.doi.org/10.1111/j.1365-246x.2008.03723.x.
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Kiselev, A. I., and V. V. Yarmolyuk. "Early Jurassic magmatism of the Kobyuminsky system of grabens (Verkhoyansk frame of the Siberian platform) and its geodynamic nature." Доклады Академии наук 484, no. 5 (May 16, 2019): 584–88. http://dx.doi.org/10.31857/s0869-56524845584-588.
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The Kobyuminsky system of grabens was formed in the Early Jurassic within the Verkhoyansk passive margin of the Siberian platform. The volcanic complex of grabens is represented by basalts with elevated TiO2 contents (> 1.8 wt%). According to geochemical characteristics, the rocks of the volcanic series occupy an intermediate position between the basalts of the oceanic islands (OIB) and the basalt-rich mid-oceanic ridges (E-MORB). The data obtained led to the conclusion that the Kobuminsky system of grabens within the passive margin of the Siberian continent arose in connection with the activity of a small mantle plume.
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Leat, Philip T., and Teal R. Riley. "Chapter 3.1b Antarctic Peninsula and South Shetland Islands: petrology." Geological Society, London, Memoirs 55, no. 1 (2021): 213–26. http://dx.doi.org/10.1144/m55-2018-68.
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AbstractThe Antarctic Peninsula contains a record of continental-margin volcanism extending from Jurassic to Recent times. Subduction of the Pacific oceanic lithosphere beneath the continental margin developed after Late Jurassic volcanism in Alexander Island that was related to extension of the continental margin. Mesozoic ocean-floor basalts emplaced within the Alexander Island accretionary complex have compositions derived from Pacific mantle. The Antarctic Peninsula volcanic arc was active from about Early Cretaceous times until the Early Miocene. It was affected by hydrothermal alteration, and by regional and contact metamorphism generally of zeolite to prehnite–pumpellyite facies. Distinct geochemical groups recognized within the volcanic rocks suggest varied magma generation processes related to changes in subduction dynamics. The four groups are: calc-alkaline, high-Mg andesitic, adakitic and high-Zr, the last two being described in this arc for the first time. The dominant calc-alkaline group ranges from primitive mafic magmas to rhyolite, and from low- to high-K in composition, and was generated from a mantle wedge with variable depletion. The high-Mg and adakitic rocks indicate periods of melting of the subducting slab and variable equilibration of the melts with mantle. The high-Zr group is interpreted as peralkaline and may have been related to extension of the arc.
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CASTRO, JUAN M., YURENA YANES, MARIA R. ALONSO, and MIGUEL IBÁÑEZ. "Hemicycla (Hemicycla) fuenterroquensis (Gastropoda: Helicoidea: Helicidae), a new species from La Palma, Canary Islands." Zootaxa 3527, no. 1 (October 26, 2012): 72. http://dx.doi.org/10.11646/zootaxa.3527.1.6.
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The rugged, volcanic oceanic island of La Palma (Fig. 1), with the oldest subaerial rocks dated at 1.7 Ma, is one of the youngest islands of the Atlantic Canarian Archipelago. La Palma is an elongated island with North-South orientation (about 45 km long and near 28 km wide in the northern half, then tapering towards its southernmost tip), with an area of 708 km2 and an altitude of 2426 m above sea level (a.s.l.). The island is in the second stage (“emergence and subaerial construction”) out of the six phases of the hotspot island’s life cycle (Fernández-Palacios & Whittaker, 2010). The most recent volcanic eruption occurred at the Teneguía volcano in 1971. The island exhibits a considerable range of habitats (from arid lowland shrub zones to humid highland evergreen forests) generated by high mountains that intercept the moist trade winds. This great variety of habitats has enhanced land snail radiation and speciation, so the island accommodates about 30 validly described endemic species of land snails, most of them belonging to the main genera (e. g., Napaeus Albers, 1850, Canariella Hesse, 1918, Insulivitrina Hesse, 1923) living today in the archipelago. The genus Hemicycla Swainson, 1840 is second land gastropods in terms of species richness within the Canary Islands, with about 40 known living species (Neiber et al., 2011). Only two of these Hemicycla species are present in La Palma, H. vermiplicata (Wollaston, 1878) and H. granomalleata (Wollaston, 1878) (Fig. 2 A, E), which were merely studied conchologically back in the 19th century. Moreover, Odhner (1937) mentions the presence in Santa Cruz de La Palma of H. ethelema Mabille, 1882, a species viewed as endemic to the Gran Canaria Island, in basis to three shells placed at his disposal by Count C. Strömfelt, Stockholm, and he compares these shells with those of H. granomalleata, indicating that he finds the best concordance in all essential charecteristics, but having the H. granomalleata shells finer granulation than those of H. ethelema.
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Santos, T. M. T., and V. Venekey. "Meiofauna and free-living nematodes in volcanic sands of a remote South Atlantic, oceanic island (Trindade, Brazil)." Journal of the Marine Biological Association of the United Kingdom 98, no. 8 (October 11, 2017): 1919–34. http://dx.doi.org/10.1017/s0025315417001710.
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This study presents patterns of spatial and temporal variation in the meiofaunal community and nematode associations on the volcanic sandy beaches of Trindade Island, a remote oceanic island in the South-east Atlantic Ocean. Samples were collected in August (rainy season) and December 2014 (dry season) on four beaches (Tartarugas, Parcel, Cabritos and Portugueses) at three zones of the intertidal (high, mid and low). A total of 10 meiofaunal groups were found. Copepods (31%) and nematodes (27%) dominated the meiofauna in all beaches and zones, regardless of the season. Nematodes were comprised mainly of non-selective deposit feeders, with a total of 27 genera from 12 families, with Cyatholaimidae, Xyalidae and Oncholaimidae as the most diverse and abundant. Significant differences were found in the meiofaunal community, as well as in nematode associations, among seasons and intertidal zones but not among beaches. The sediment characteristics were the main drivers regulating the structure of meiobenthic fauna in Trindade Island. Our findings are also compared to other studies focusing on the meiofauna and nematodes of oceanic islands with carbonate and volcanic sediments; the major patterns are herein presented.
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Leat, Philip T., Peter T. Fretwell, Alex J. Tate, Robert D. Larter, Tara J. Martin, John L. Smellie, Wilfried Jokat, and Gerhard Bohrmann. "Bathymetry and geological setting of the South Sandwich Islands volcanic arc." Antarctic Science 28, no. 4 (March 18, 2016): 293–303. http://dx.doi.org/10.1017/s0954102016000043.
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AbstractThe South Sandwich Islands and associated seamounts constitute the volcanic arc of an active subduction system situated in the South Atlantic. We introduce a map of the bathymetry and geological setting of the South Sandwich Islands and the associated East Scotia Ridge back-arc spreading centre that consists of two sides: side 1, a regional overview of the volcanic arc, trench and back-arc, and side 2, detailed maps of the individual islands. Side 1 displays the bathymetry at scale 1:750 000 of the intra-oceanic, largely submarine South Sandwich arc, the back-arc system and other tectonic boundaries of the subduction system. Satellite images of the islands on side 2 are at scales of 1:50 000 and 1:25 000 with contours and main volcanological features indicated. These maps are the first detailed topological and bathymetric maps of the area. The islands are entirely volcanic in origin, and most have been volcanically or fumarolically active in historic times. Many of the islands are ice-covered, and the map forms a baseline for future glaciological changes caused by volcanic activities and climate change. The back-arc spreading centre consists of nine segments, most of which have rift-like morphologies.
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CARRACEDO, J. C., S. DAY, H. GUILLOU, E. RODRÍGUEZ BADIOLA, J. A. CANAS, and F. J. PÉREZ TORRADO. "Hotspot volcanism close to a passive continental margin: the Canary Islands." Geological Magazine 135, no. 5 (September 1998): 591–604. http://dx.doi.org/10.1017/s0016756898001447.
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The Canarian Archipelago is a group of volcanic islands on a slow-moving oceanic plate, close to a continental margin. The origins of the archipelago are controversial: a hotspot or mantle plume, a zone of lithospheric deformation, a region of compressional block-faulting or a rupture propagating westwards from the active Atlas Mountains fold belt have been proposed by different authors. However, comparison of the Canarian Archipelago with the prototypical hotspot-related island group, the Hawaiian Archipelago, reveals that the differences between the two are not as great as had previously been supposed on the basis of older data. Quaternary igneous activity in the Canaries is concentrated at the western end of the archipelago, close to the present-day location of the inferred hotspot. This is the same relationship as seen in the Hawaiian and Cape Verde islands. The latter archipelago, associated with a well-defined but slow-moving mantle plume, shows anomalies in a plot of island age against distance which are comparable to those seen in the Canary Islands: these anomalies cannot therefore be used to argue against a hotspot origin for the Canaries. Individual islands in both archipelagoes are characterized by initial rapid growth (the ‘shield-building’ stages of activity), followed by a period of quiescence and deep erosion (erosion gap) which in turn is followed by a ‘post-erosional’ stage of activity. The absence of post-shield stage subsidence in the Canaries is in marked contrast with the major subsidence experienced by the Hawaiian Islands, but is comparable with the lack of subsidence evident in other island groups at slow-moving hotspots, such as the Cape Verdes. Comparison of the structure and structural evolution of the Canary Islands with other oceanic islands such as Hawaii and Réunion reveals many similarities. These include the development of triple (‘Mercedes Star’) rift zones and the occurrence of giant lateral collapses on the flanks of these rift zones. The apparent absence of these features in the post-erosional islands may in part be a result of their greater age and deeper erosion, which has removed much of the evidence for their early volcanic architecture. We conclude that the many similarities between the Canary Islands and island groups whose hotspot origins are undisputed show that the Canaries have been produced in the same way.
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Ramalho, Ricardo S., Gisela Winckler, José Madeira, George R. Helffrich, Ana Hipólito, Rui Quartau, Katherine Adena, and Joerg M. Schaefer. "Hazard potential of volcanic flank collapses raised by new megatsunami evidence." Science Advances 1, no. 9 (October 2015): e1500456. http://dx.doi.org/10.1126/sciadv.1500456.
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Large-scale gravitational flank collapses of steep volcanic islands are hypothetically capable of triggering megatsunamis with highly catastrophic effects. Yet, evidence for the generation and impact of collapse-triggered megatsunamis and their high run-ups remains scarce or is highly controversial. Therefore, doubts remain on whether island flank failures truly generate enough volume flux to trigger giant tsunamis, leading to diverging opinions concerning the real hazard potential of such collapses. We show that one of the most prominent oceanic volcanoes on Earth—Fogo, in the Cape Verde Islands—catastrophically collapsed and triggered a megatsunami with devastating effects ~73,000 years ago. Our deductions are based on the recent discovery and cosmogenic3He dating of tsunamigenic deposits found on nearby Santiago Island, which attest to the impact of this giant tsunami and document wave run-up heights exceeding 270 m. The evidence reported here implies that Fogo’s flank failure involved at least one fast and voluminous event that led to a giant tsunami, in contrast to what has been suggested before. Our observations therefore further demonstrate that flank collapses may indeed catastrophically happen and are capable of triggering tsunamis of enormous height and energy, adding to their hazard potential.
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Herrera, Christian, and Emilio Custodio. "Groundwater flow in a relatively old oceanic volcanic island: The Betancuria area, Fuerteventura Island, Canary Islands, Spain." Science of The Total Environment 496 (October 2014): 531–50. http://dx.doi.org/10.1016/j.scitotenv.2014.07.063.
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MCINNES, SANDRA J., and PETER CONVEY. "Tardigrade fauna of the South Sandwich Islands, maritime Antarctic." Zootaxa 1058, no. 1 (October 4, 2005): 43. http://dx.doi.org/10.11646/zootaxa.1058.1.3.
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The maritime Antarctic South Sandwich Islands are an isolated oceanic archipelago of volcanic origin lying between 56º18'S, 27º34'W and 59º27'S, 27º22'W. All the islands are of recent origin (maximum ages 0.5–3 million years) with many still exhibiting some form of volcanic activity. The islands are part of the Scotia Arc, lying on a crustal upwarp extending from South Georgia through the South Sandwich Islands to the South Shetland Islands that connects the Andean chain of South America to the Antarctic Peninsula. As part of an extensive biological survey completed during early 1997, samples were collected from 10 of the 11 major islands in the archipelago from which the tardigrade fauna has subsequently been extracted. We report the composition of this fauna, and discuss its biogeographical relationships. Tardigrade species richness was low (6 taxa), in keeping with the recent formation and isolation of these islands. However, as reported previously for the terrestrial arthropod fauna and bryophyte flora, there is indication of both suband maritime Antarctic origin.
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Silva, Pablo G. "The role of Volcanic vs Seismic actions in ground deformations recorded in Oceanic Volcanic Islands: Examples from the Eastern Canary Islands (Spain)." Quaternary International 279-280 (November 2012): 450–51. http://dx.doi.org/10.1016/j.quaint.2012.08.1485.
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DAY, S. J., J. C. CARRACEDO, and H. GUILLOU. "Age and geometry of an aborted rift flank collapse: the San Andres fault system, El Hierro, Canary Islands." Geological Magazine 134, no. 4 (July 1997): 523–37. http://dx.doi.org/10.1017/s0016756897007243.
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The catastrophic slope failures and landslides that occur in the final stages of lateral collapses of volcanoes destroy much of the evidence for precursory deformation and the early stages of the collapses concerned. Aborted or incomplete collapse structures, although rare, are rich sources of information on these stages of development of catastrophic collapses. The San Andres fault system, on the volcanic island of El Hierro, is a relatively young (between about 545 and about 261–176 ka old) but inactive lateral collapse structure. It appears to represent an aborted giant landslide. It is developed along the flank of a steep-sided volcanic rift zone, and is bounded by a discrete strike-slip fault zone at the up-rift end, closest to the centre of the island. This geometry differs markedly from that of collapse structures on stratovolcanoes but bears some similarities to that of active fault systems on Hawaii. Although the fault system has undergone little erosion, cataclasites which formed close to the palaeosurface are well exposed. These cataclasites are amongst the first fault rocks to be described from volcano lateral collapse structures and include the only pseudotachylytes to have been identified in such structures to date. Their development at unusually shallow depths is attributed to large movements on the fault in a single event, the inferred aborted landslide, and a lack of pressurized pore water. The absence of pressurized fluids in the slumping block may have caused the San Andres fault system to cease moving, rather than develop into a giant volcanic landslide. The recognition that the San Andres fault system is inactive greatly reduces the estimated volcanic hazard associated with El Hierro. However, the lack of evidence for precursory deformation prior to the aborted landslide event is disturbing as it implies that giant lateral collapses can occur on steep-sided oceanic islands with little warning.
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Gailler, Lydie-Sarah, Guillaume Martelet, Isabelle Thinon, Vincent Bouchot, Jean-Frédéric Lebrun, and Philippe Münch. "Crustal structure of Guadeloupe islands and the Lesser Antilles arc from a new gravity and magnetic synthesis." Bulletin de la Société Géologique de France 184, no. 1-2 (January 1, 2013): 77–97. http://dx.doi.org/10.2113/gssgfbull.184.1-2.77.
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Abstract Guadeloupe island (West French Indies) is one of the twenty islands that compose the Lesser Antilles arc, which results from the subduction of the Atlantic ocean plate beneath the Caribbean one. The island lies in a complex volcano-tectonic system and the need to understand its geological context has led to numerous on- and offshore geophysical investigations. This work presents a compilation and the processing of available, on-land, airborne and marine, gravity and magnetic data acquired during the last 40 years on Guadeloupe islands and at the scale of the Lesser Antilles arc. The overall dataset provides new Bouguer and reduced to the pole magnetic anomaly maps at the highest achievable resolution. Regionally, the main central negative gravity trend of the arc allows defining two subsident areas. The first one is parallel to the arc direction (~N160°E) to the north, whereas the second unexpected southern one is oriented parallel to oceanic ridges (N130°E). Along the Outer arc, the long wavelength positive anomaly is interpreted, at least along the Karukera spur, as an up-rise of the volcanic basement in agreement with the seismic studies. To the NE of Guadeloupe, the detailed analysis of the geophysical anomalies outlines a series of structural discontinuities consistent with the main bathymetric morphologies, and in continuity of the main fault systems already reported in this area. Based on geophysical evidences, this large scale deformation and faulting of the Outer arc presumably primarily affects the Atlantic subducting plate and secondarily deforms the upper Caribbean plate and the accretion prism, as evidenced in bathymetry as well as on the islands. At the scale of Guadeloupe island, combined gravity and magnetic modeling has been initiated based on existing interpretation of old seismic refraction profiles, with a general structure in three main layers. According to our geophysical anomalies, additional local structures are also modeled in agreement with geological observations: i) the gravity and magnetic signals confirm an up-rise of the volcanic basement below the limestone platforms outcropping on Grande-Terre island ; ii) the ancient volcanic complexes of Basse-Terre island are modeled with high density and reverse magnetized formations; iii) the recent volcanic centre is associated with formations consistent with the low measured density and the underlying hydrothermal system. The E-W models coherently image a NNW-SSE depression structure in half-graben beneath Basse-Terre island, its western scarp following the arc direction in agreement with bathymetric and seismic studies to the north of the island. The so-defined depressed area, and particularly its opening in half-graben toward the SW, is interpreted as the present-day front of deformation of the upper plate, associated with the recent volcanic activity on and around Guadeloupe. Based on this regional deformation model, perspectives are given for further integrated investigation of key targets to address the internal structure and evolution of the Lesser Antilles arc and Guadeloupe volcanic system.
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Lloret, E., C. Dessert, E. Lajeunesse, O. Crispi, L. Pastor, J. Gaillardet, and M. F. Benedetti. "Are small mountainous tropical watersheds of oceanic islands important for carbon export?" Biogeosciences Discussions 9, no. 6 (June 18, 2012): 7117–63. http://dx.doi.org/10.5194/bgd-9-7117-2012.
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Abstract. In the tropic, the small watersheds are affected by intense meteorological events playing an important role on the erosion of soils and therefore on the associated organic carbon fluxes. We studied the geochemistry of three small watersheds around the Basse-Terre volcanic Island (FWI) during a four years period, by measuring DOC, POC and DIC concentrations. The mean annual yields ranged 8.1–15.8 t C km−2 yr−1, 1.9–8.6 t C km−2 yr−1 and 8.1–25.5 t C km−2 yr−1 for DIC, DOC and POC, respectively. Floods and extreme floods represent 45 to 70 % of the annual DOC flux, and more than 80 % of the annual POC flux. The DIC flux occurs essentially during the low water level, only 43 % of the annual DIC flux is exported during floods. The distribution of the dissolved carbon between the inorganic and the organic fraction is correlated to the hydrodynamic of rivers. During low water level and floods, the dissolved carbon is exported under the inorganic form (DIC/DOC = 2.6 ± 2.1), while during extreme floods, the dissolved carbon transported is mostly organic (DIC/DOC = 0.7 ± 0.2). The residence time of the organic carbon in Guadeloupean soils may vary from 381 to 1000 yr, and is linked to the intensity of meteorological events than the frequency of meteorological events. Looking at the global carbon mass balance, the total export of organic carbon coming from small tropical and volcanic mountainous rivers is estimated about 2.0–8.9 Tg C yr−1 for DOC and about 8.4–26.5 Tg C yr−1 for POC, emphasizing that these carbon fluxes are significant and should be included in global carbon budgets.
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Rivera, J., G. Lastras, M. Canals, J. Acosta, B. Arrese, N. Hermida, A. Micallef, O. Tello, and D. Amblas. "Construction of an oceanic island: Insights from the El Hierro (Canary Islands) 2011-2012 submarine volcanic eruption." Geology 41, no. 3 (January 4, 2013): 355–58. http://dx.doi.org/10.1130/g33863.1.
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Craven, Dylan, Tiffany M. Knight, Kasey E. Barton, Lalasia Bialic-Murphy, and Jonathan M. Chase. "Dissecting macroecological and macroevolutionary patterns of forest biodiversity across the Hawaiian archipelago." Proceedings of the National Academy of Sciences 116, no. 33 (July 29, 2019): 16436–41. http://dx.doi.org/10.1073/pnas.1901954116.
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Biodiversity patterns emerge as a consequence of evolutionary and ecological processes. Their relative importance is frequently tested on model ecosystems such as oceanic islands that vary in both. However, the coarse-scale data typically used in biogeographic studies have limited inferential power to separate the effects of historical biogeographic factors (e.g., island age) from the effects of ecological ones (e.g., island area and habitat heterogeneity). Here, we describe local-scale biodiversity patterns of woody plants using a database of more than 500 forest plots from across the Hawaiian archipelago, where these volcanic islands differ in age by several million years. We show that, after controlling for factors such as island area and heterogeneity, the oldest islands (Kaua’i and O’ahu) have greater native species diversity per unit area than younger islands (Maui and Hawai’i), indicating an important role for macroevolutionary processes in driving not just whole-island differences in species diversity, but also local community assembly. Further, we find that older islands have a greater number of rare species that are more spatially clumped (i.e., higher within-island β-diversity) than younger islands. When we included alien species in our analyses, we found that the signal of macroevolutionary processes via island age was diluted. Our approach allows a more explicit test of the question of how macroevolutionary factors shape not just regional-scale biodiversity, but also local-scale community assembly patterns and processes in a model archipelago ecosystem, and it can be applied to disentangle biodiversity drivers in other systems.
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BATELKA, JAN, and JAKUB STRAKA. "Ripiphorus caboverdianus sp. nov.—the first ripiphorid record from the Macaronesian volcanic islands (Coleaoptera: Ripiphoridae: Ripiphorinae)." Zootaxa 2792, no. 1 (March 16, 2011): 51. http://dx.doi.org/10.11646/zootaxa.2792.1.5.
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Ripiphorus caboverdianus sp. nov. (Ripiphoridae, Ripiphorinae) from Boavista Island (Cape Verde archipelago) represents the first record of the family Ripiphoridae from the volcanic islands west of Africa and the first record of the genus Ripiphorus on an isolated volcanic archipelago worldwide. Its significance for our understanding of oceanic dispersal abilities of the subfamily Ripiphorinae is discussed. The new species is characterized by milky white elytra, hyaline hind wings and translucent membranous suture between dorsal and ventral surface of the first abdominal segments in both sexes. Female has a slightly curved hind tibia, 2× wider at the apex than at its base, and a slender, parallel-sided first metatarsomere, 5× as long as wide. Morphology of the free-living first instar larva is described; it is very similar to R. smithi Linsley & MacSwain, 1950. Behavioral observations of the adults and the first instar larvae in the type locality are given. Known hosts of the genus Ripiphorus are reviewed; possible host-association and conservation implications for the new species are discussed.
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Burner, Ryan C., Subir B. Shakya, Tri Haryoko, Mohammad Irham, Dewi M. Prawiradilaga, and Frederick H. Sheldon. "Ornithological observations from Maratua and Bawean Islands, Indonesia." TREUBIA 45 (January 10, 2019): 11–24. http://dx.doi.org/10.14203/treubia.v45i0.3445.
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Indonesia’s many islands, large and small, make it an important center of avian diversity and endemism. Current biogeographic understanding, however, is limited by the lack of modern genetic samples for comparative analyses from most of these islands, and conservation efforts are hampered by the paucity of recent information from small islands peripheral to major, more commonly visited islands. In November and December 2016, we visited Maratua, an oceanic coral atoll 50 km east of Borneo, and Bawean, a volcanic island on the Sunda continental shelf 150 km north of Java, to survey birds and collect specimens for morphological and genetic analysis. We detected many of the birds on Maratua’s historical lists and added several new resident and migratory species. Notably, we did not detect the Maratua White-rumped Shama (Copsychus malabaricus barbouri). On Bawean, we found the forests to be nearly silent and detected remarkably few resident land-bird species overall. The severe population reduction of C. m. barbouri on Maratua and the drastic reduction of forest birds on Bawean probably result from overexploitation by the cage-bird trade in the first case and a combination of the cage-bird trade and pellet-gun hunting in the second.
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Neall, Vincent E., and Steven A. Trewick. "The age and origin of the Pacific islands: a geological overview." Philosophical Transactions of the Royal Society B: Biological Sciences 363, no. 1508 (September 3, 2008): 3293–308. http://dx.doi.org/10.1098/rstb.2008.0119.
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The Pacific Ocean evolved from the Panthalassic Ocean that was first formed ca 750 Ma with the rifting apart of Rodinia. By 160 Ma, the first ocean floor ascribed to the current Pacific plate was produced to the west of a spreading centre in the central Pacific, ultimately growing to become the largest oceanic plate on the Earth. The current Nazca, Cocos and Juan de Fuca (Gorda) plates were initially one plate, produced to the east of the original spreading centre before becoming split into three. The islands of the Pacific have originated as: linear chains of volcanic islands on the above plates either by mantle plume or propagating fracture origin, atolls, uplifted coralline reefs, fragments of continental crust, obducted portions of adjoining lithospheric plates and islands resulting from subduction along convergent plate margins. Out of the 11 linear volcanic chains identified, each is briefly described and its history summarized. The geology of 10 exemplar archipelagos (Japan, Izu-Bonin, Palau, Solomons, Fiji, New Caledonia, New Zealand, Society, Galápagos and Hawaii) is then discussed in detail.
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Ramalho, Ricardo S., António Brum da Silveira, Paulo E. Fonseca, José Madeira, Michael Cosca, Mário Cachão, Maria M. Fonseca, and Susana N. Prada. "The emergence of volcanic oceanic islands on a slow-moving plate: The example of Madeira Island, NE Atlantic." Geochemistry, Geophysics, Geosystems 16, no. 2 (February 2015): 522–37. http://dx.doi.org/10.1002/2014gc005657.
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Ramalho, Ricardo S., Rui Quartau, Alan S. Trenhaile, Neil C. Mitchell, Colin D. Woodroffe, and Sérgio P. Ávila. "Coastal evolution on volcanic oceanic islands: A complex interplay between volcanism, erosion, sedimentation, sea-level change and biogenic production." Earth-Science Reviews 127 (December 2013): 140–70. http://dx.doi.org/10.1016/j.earscirev.2013.10.007.
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Puchkov, Viktor N. "The plume-dependent granite-rhyolite magmatism." LITOSFERA, no. 5 (October 28, 2018): 692–705. http://dx.doi.org/10.24930/1681-9004-2018-18-5-692-705.
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The plume-dependent magmatism is widespread and well justified. The bulk of it is represented by flood basalts, basalts of oceanic islands (OIB), and basalts of oceanic plateaus (OPB), though the whole scope of plume magmatism is very diverse. A noticeable role among them is played also by acid (silicic) magmatic rocks - rhyolites and granites. Two main types of plume magmatism are recognized. The first belongs to Large Igneous Provinces (LIP) and is thought to be born at the Core-Mantle boundary within structures, called superswells, that produce giant, short-living mantle upwellings, resulting in abundant volcanism on the Earth’s surface. The second type is represented by linear volcanic chains characterized by regular age progressions. They are formed by single plumes - thin ascending mantle flows, acting during longer periods of time. It is shown that the abundance of silicic magmatism strongly depends on the type of the earth’s crust. Among flood basalts of continents, silicic magmatism is usually present, subordinate in volume to basalts and belongs to a bimodal type of magmatism. But in some cases LIP in continents are formed predominantly by silicic rocks; they are given the name Silicic LIPS, or SLIPS. In oceans, LIP are fundamentally basaltic with no considerable volume of silicic volcanics, if any. The time-progressive volcanic chains in continents are rare and usually comprise a noticeable silicic component. In oceans, the chains are composed mostly of basalts (OIB type), though in the top parts of volcanoes more acid and alkaline differentiates are present; usually they lack rhyolites and granites, except the cases of a presence of some strips of continental crust or anomalously thick oceanic crust. This review can lead to a thought of an important role of melting of continental crust in formation of plume-dependent rhyolite-granite magmatism. As for the Urals, the proofs for a presence of plume-dependent magmatism in its history were presented only recently. Among the plume episodes, some are characterized by presence of silicic components, in particular: Mashak (1380-1385 Ma), Igonino (707-732 Ma), Man’khambo (mainly Cambrian), Ordovician Kidryasovo, Stepninsky (Permian) and Urals-Siberian (Triassic).
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Lubetkin, Megan, Nicole Raineault, and Sarah Gaines. "Envisioning an Interconnected Ocean: Understanding the Links Between Geological Ocean Structure and Coastal Communities in the Pacific." Marine Technology Society Journal 55, no. 3 (May 1, 2021): 68–69. http://dx.doi.org/10.4031/mtsj.55.3.44.
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Abstract Covering nearly one third of the Earth's surface, the Pacific Ocean contains many significant interconnected geologic features extending into the coastal zone and the islands themselves. Trenches, ridges, seamount chains, faults, and fracture zones are not only fundamental expressions of Earth processes but also fundamental to life. Without awareness of these features and their natural and cultural importance, marine management and global understanding will remain disjointed. The Ocean Exploration Trust (OET) will spend the next several years in the Pacific conducting scientific expeditions to better understand the ocean through seafloor mapping and ocean exploration. Western ocean science is one of many ways to perceive and value the structural features of the Pacific. Communities across Pacific islands—often volcanic peaks emerging from deep below—are interconnected by water and by the underlying seafloor. We acknowledge the knowledge from local communities and recognize the multitude of ways to conceptualize and relate to the Pacific. With the University of Rhode Island's Coastal Resources Center (CRC), OET seeks to collaborate with local communities to reveal the structural significance and interconnected nature of oceanic features, making a link to the livelihoods of Pacific islanders. Further objectives would be co-designed with partners from local communities.
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Marques, R., M. I. Prudêncio, J. C. Waerenborgh, B. J. C. Vieira, F. Rocha, M. I. Dias, J. Madeira, and J. Mata. "Extrusive carbonatite outcrops – A source of chemical elements imbalance in topsoils of oceanic volcanic islands." CATENA 157 (October 2017): 333–43. http://dx.doi.org/10.1016/j.catena.2017.05.035.
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Davis, Alicé S., Susan H. Gunn, Leda-Beth Gray, Michael S. Marlow, and Florence L. Wong. "Petrology and isotopic composition of Quaternary basanites dredged from the Bering Sea continental margin near Navarin Basin." Canadian Journal of Earth Sciences 30, no. 5 (May 1, 1993): 975–84. http://dx.doi.org/10.1139/e93-081.
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Quaternary basanites were recovered from shallow water depth from the continental margin of the Bering Sea (58°39.0′N, 177°12.9′W) near Navarin Basin. The basanites are highly vesicular flow rock and hyaloclastites similar to other alkalic volcanic rocks erupted repeatedly during the late Cenozoic on islands in the Bering Sea region and in mainland Alaska. K–Ar ages for the basanites indicate at least two episodes of volcanism at about 1.1 and 0.4 Ma. Similar alkalic volcanism occurred sporadically at geographically widely separated centers in the Bering Sea region for at least the past 6 Ma. Chemically, these alkalic lavas are intraplate basalts similar to those erupted from oceanic islands and in some continental settings. Trace-element data indicate these alkalic lavas have been generated by small, but variable, amounts of partial melting of a meta-somatized lherzolite source. The relatively primitive compositions (MgO > 9%), presence of mantle-derived xenoliths in some alkalic lavas, and presence of forsteritic olivine with low CaO and high NiO suggest that magma rose rapidly from greath depth without spending time in large, long-lived magma chambers. Although lavas from different volcanic centers in the Bering Sea region are similar with respect to major elements and many trace-element ratios, isotopic compositions indicate heterogeneities in the source. The Navarin basanites have higher 87Sr/86Sr and lower 143Nd/144Nd values than any other lavas so far reported from this region. The 207Pb/204Pb isotopic ratios indicate involvement of a crustal component, which may have resulted from metasomatism associated with subduction-related magmatic activity during the Early Eocene in this region. Although some volcanic episodes appear to have occurred roughly synchronously at geographically widely separated centers, no large-scale regional extension nor presence of large mantle plumes are indicated. Instead, alkalic volcanism apparently resulted from upwelling and decompressional melting of small isolated mantle diapirs in response to local lithospheric attenuation associated with jostling of blocks during adjustment to regional stresses.
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Garcia, Michael O., and Eric Hellebrand. "Celestine discovered in Hawaiian basalts." American Mineralogist 105, no. 1 (January 1, 2020): 52–57. http://dx.doi.org/10.2138/am-2020-6995.
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Abstract We report here the first occurrence of celestine (SrSO4) in recent oceanic basalts. Celestine was found in moderately altered accidental volcanic blocks from Ka‘ula Island, a rejuvenated tuff cone in the northern Hawaiian Islands. This occurrence is novel not only for the presence of celestine but also for the absence of barite, the sulfate mineral most commonly found in oceanic hydrothermal deposits. Celestine was found lining vesicles and partially fillings voids within the matrix of several high Sr (2200–6400 ppm) Ka‘ula basalts. High-quality wavelength-dispersive microprobe analyses of celestine are reported here for near end-member celestine (>90%). The Ka‘ula celestine deposits are compositionally heterogeneous with large variations in Ba content (0.9–7.5 wt%) within single mineral aggregates. The most likely source of the Sr for celestine in the Ka‘ula basalts was the host basalt, which contains ~1200 ppm. This is about 10 times higher than normally found in mid-ocean ridge basalts and 4 times greater than commonly observed in Hawaiian basalts. Hydrothermal alteration by S-bearing fluids related to the eruption that transported these accidentally fragments probably mobilized Sr in the blocks. These S-rich solutions later precipitated celestine during or following the eruption. We were unable to confirm the origin for the Sr via Sr isotope measures because the Ka‘ula celestine was too fine grained, friable, and widely dispersed to be concentrated for Sr isotope analyses. Future studies of basalts from active volcanoes on oceanic islands, especially for basalts with elevated Sr contents (>1000 ppm), should be aware of the possible presence of celestine in moderately altered lavas.
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Casson, Max, Luc G. Bulot, Jason Jeremiah, and Jonathan Redfern. "Deep sea rock record exhumed on oceanic volcanic islands: the Cretaceous sediments of Maio, Cape Verde." Gondwana Research 81 (May 2020): 252–64. http://dx.doi.org/10.1016/j.gr.2019.11.007.
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Carracedo, Juan Carlos, Valentin R. Troll, Kirsten Zaczek, Alejandro Rodríguez-González, Vicente Soler, and Frances M. Deegan. "The 2011–2012 submarine eruption off El Hierro, Canary Islands: New lessons in oceanic island growth and volcanic crisis management." Earth-Science Reviews 150 (November 2015): 168–200. http://dx.doi.org/10.1016/j.earscirev.2015.06.007.
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LIMA, DANIEL, MARCOS TAVARES, and JOEL BRAGA JR DE MENDONÇA. "Paguroids (Decapoda: Anomura: Diogenidae and Paguridae) of the remote oceanic Archipelago Trindade and Martin Vaz, off southeast Brazil, with new records, description of three new species and zoogeographical notes." Zootaxa 4694, no. 1 (November 5, 2019): 1–63. http://dx.doi.org/10.11646/zootaxa.4694.1.1.
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Trindade and Martin Vaz (TMV) is a highly isolated, oceanic volcanic archipelago located some 1200 km off the Brazilian coast and about 4200 km away from the nearest African coast. For almost 100 years Calcinus tibicen (Herbst, 1791) was the only hermit crab species known from TMV. From 2012 to 2018, 263 daytime SCUBA diving and intertidal samplings conducted at TMV yielded 1075 paguroid specimens in 10 species, three of which are established herein as new species: Iridopagurus martinvaz sp. nov., Nematopagurus micheleae sp. nov., and Pagurus carmineus sp. nov. Iridopagurus margaritensis García-Gómez, 1983, and Phimochirus leurocarpus McLaughlin, 1981, both only known from the northern hemisphere, are recorded for the first time from the southwestern Atlantic. Opportunity was taken herein to include hitherto unreported or little known specimens from along the Vitória-Trindade Seamount Chain, namely, Dardanus venosus H. Milne Edwards, 1848, Nematopaguroides pusillus Forest & de Saint Laurent, 1968, Pagurus provenzanoi Forest & de Saint Laurent, 1968, and Phimochirus holthuisi (Provenzano, 1961). The lectotype of Pagurus venosus H. Milne Edwards, 1848 is designated as the neotype for the obscure Pagurus arrosor divergens Moreira, 1905, which thus becomes an objective junior synonym of the former. A list of all paguroid species known from the tropical southern-central Atlantic oceanic archipelagoes and islands (Ascension, Cape Verde, Fernando de Noronha, Gulf of Guinea, Rocas Atoll, Saint Helena, Trindade and Martin Vaz) with their gross distribution in the Atlantic Ocean is provided. Investigation on the existence of patterns of geographic distribution for the paguroid fauna of the tropical southern-central Atlantic oceanic islands showed that 70% percent of the paguroids from TMV are western Atlantic in origin and 30% endemic. No amphi-Atlantic paguroid species are known from TMV. Conversely, the affinity of Ascension’s (33%) and Saint Helena’s (50%) paguroids is with the eastern Atlantic; no western Atlantic paguroids have been reported from these two islands so far. Exploration on the existence of trends of correlation between islands area and species richness through the Spearman’s coefficient of correlation showed that the patterns in the number of paguroid species cannot be explained by variation in island area alone (rs = 0.4728; p = 0.28571).
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Márquez, Alvaro, Raquel Herrera, Tatiana Izquierdo, Fidel Martín-González, Iván López, and Silvia Martín-Velázquez. "The dyke swarms of the Old Volcanic Edifice of La Gomera (Canary Islands): Implications for the origin and evolution of volcanic rifts in oceanic island volcanoes." Global and Planetary Change 171 (December 2018): 255–72. http://dx.doi.org/10.1016/j.gloplacha.2017.12.004.
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Barker, Abigail, Thor Hansteen, and David Nilsson. "Unravelling the Crustal Architecture of Cape Verde from the Seamount Xenolith Record." Minerals 9, no. 2 (February 1, 2019): 90. http://dx.doi.org/10.3390/min9020090.
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The Cape Verde oceanic plateau hosts 10 islands and 11 seamounts and provides an extensive suite of alkaline lavas and pyroclastic rocks. The volcanic rocks host a range of crustal and mantle xenoliths. These xenoliths provide a spectrum of lithologies available to interact with magma during transport through the lithospheric mantle and crust. We explore the origin and depth of formation of crustal xenoliths to develop a framework of magma-crust interaction and a model for the crustal architecture beneath the Cape Verde oceanic plateau. The host lavas are phononephelinites to phonolites and the crustal xenoliths are mostly mafic plutonic assemblages with one sedimentary xenolith. REE profiles of clinopyroxene in the host lavas are light rare-earth element (LREE) enriched whereas clinopyoxene from the plutonic xenoliths are LREE depleted. Modelling of REE melt compositions indicates the plutonic xenoliths are derived from mid-ocean ridge basalt (MORB)-type ocean crust. Thermobarometry indicates that clinopyroxene in the host lavas formed at depths of 17 to 46 km, whereas those in the xenoliths formed at 5 to 20 km. This places the depth of origin of the plutonic xenoliths in the oceanic crust. Therefore, the xenoliths trace magma-crust interaction to the MORB oceanic crust and overlying sediments located beneath the Cape Verde oceanic plateau.
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Smith, Alan D., and Richard StJ Lambert. "Nd, Sr, and Pb isotopic evidence for contrasting origins of late Paleozoic volcanic rocks from the Slide Mountain and Cache Creek terranes, south-central British Columbia." Canadian Journal of Earth Sciences 32, no. 4 (April 1, 1995): 447–59. http://dx.doi.org/10.1139/e95-038.
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The Slide Mountain and Cache Creek terranes are two prominent oceanic sutures in the Canadian Cordillera. Petrological and isotopic variations between volcanic rocks in these terranes support earlier interpretations from stratigraphic evidence that the Slide Mountain terrane represents the remnant of a late Paleozoic basin situated marginal to western North America, whereas the Cache Creek terrane represents a remnant of a much larger, open-ocean basin. Slide Mountain terrane volcanic rocks, represented by Late Pennsylvanian basalts of the Fennell Formation, resemble normal mid-oceanic ridge basalts but possess an unusual kaersutite- or augite-dominated mineralogy. Their εNd(300 Ma) values of +7.7 to +10.2 are among the highest observed for Paleozoic basalts. The hydrous mineralogy can be reconciled with eruption on a spreading ridge in either a back-arc or marginal basin setting. The latter is preferred from Pb isotope compositions (206Pb/204Pb = 17.7–18.5, 207Pb/204Pb = 15.51–15.61, 208Pb/204Pb = 37.2–38.8), which suggest exchange with high Th/U continental-derived sediment during hydrothermal alteration. Volcanic rocks, probably middle Mississippian, in the Bonaparte subterrane of the Cache Creek terrane include picrites and basalts belonging to a within-plate tholeiite suite. The intraplate suite broadly resembles Hawaiian basalts in major and trace element composition. However, moderate positive εNd values (εNd(340 Ma) +4.2 to +5.6) and a transition toward DUPAL signatures in Pb isotopic composition (206Pb/204Pb = 18.1–19.1, 207Pb/204Pb = 15.54–15.61, 208Pb/204Pb = 37.8–38.6) are features more similar to volcanic rocks from modern South Pacific ocean islands. Basaltic andesite and andesitic tuffs, also found in the Bonaparte subterrane, are tentatively correlated with Late Triassic to Early Jurassic low-K tholeiitic volcanic rocks of the Nicola Group on the Quesnel terrane.
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Parra, M., P. Delmont, A. Ferragne, C. Latouche, J. C. Pons, and C. Puechmaille. "Origin and evolution of smectites in Recent marine sediments of the NE Atlantic." Clay Minerals 20, no. 3 (September 1985): 335–46. http://dx.doi.org/10.1180/claymin.1985.020.3.06.
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AbstractPresent-day marine sediments around the emerged basaltic areas of Iceland and the Faeroe Islands are characterized by the abundance and predominance of smectites. Smectites increase regularly and systematically near volcanic areas. Their origin from (i) meteoric/deuteric weathering, (ii) hydrothermal products, (iii) neoformation in the marine environment or (iv) transformation during their transport to or stay in oceanic regions is considered in a comparative study of three types of environments on or near the Faeroe Islands. These are (1) a basaltic environment where phyllite minerals of deuteric and hydrothermal origin are abundant; (2) a soil environment formed on basaltic flows; (3) a marine sedimentary environment within adjacent sedimentary basins. This investigation clearly shows the link between hydrothermal and deuteric saponite-celadonite in basalt, Fe,Mg-smectite in Faeroe soils and Fe-smectite in marine sediments.
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Coello-Bravo, Juan Jesús, Álvaro Márquez, Raquel Herrera, María José Huertas, and Eumenio Ancochea. "Multiple related flank collapses on volcanic oceanic islands: Evidence from the debris avalanche deposits in the Orotava Valley water galleries (Tenerife, Canary Islands)." Journal of Volcanology and Geothermal Research 401 (September 2020): 106980. http://dx.doi.org/10.1016/j.jvolgeores.2020.106980.
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Pellizzari, Franciane, Vanessa Sayuri Osaki, and Michelle C. Santos-Silva. "New records of seaweeds and filamentous cyanobacteria from Trindade Island: an updated checklist to support conservation guidelines and monitoring of environmental changes in the southern Atlantic archipelagos." Scientia Marina 84, no. 3 (September 4, 2020): 227. http://dx.doi.org/10.3989/scimar.05036.05a.
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Oceanic islands are natural laboratories for investigating species diversity and richness patterns. Changes in abiotic parameters may induce shifts in marine biota. Seaweeds are recognized as bioindicators, though those from remote tropical islands have been rarely studied. This study updates the diversity, richness and distribution of macroalgae from Trindade, a Brazilian volcanic island located 1140 km off the coast. Biotic data, obtained in a global database and in situ and compiled in a new records list, were associated with abiotic parameters. Conservation and ecological issues were discussed in the context of the observed greater richness, expansion of the distributional range and low endemism. A total of 141 species were identified, including 60 new records and 20 taxa of filamentous cyanobacteria. The greater richness, including potential cryptogenic species, may primarily be associated with past incomplete samplings, current new techniques and combined taxonomical methods, including molecular analysis for cryptic species. However, on the macroscale, this study provides information for the re-evaluation of aspects of endemism, connections and biogeographical distribution shifts of seaweed assemblages, considering environmental changes. In addition, this updated checklist establishes a baseline for further comparative studies, reinforcing the hypothesis that biogeographical isolation can be disrupted by meteorological and oceanographic shifts, altering dispersal patterns and resulting in higher ecosystems connectivity.
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Ricklefs, Robert, and Eldredge Bermingham. "The West Indies as a laboratory of biogeography and evolution." Philosophical Transactions of the Royal Society B: Biological Sciences 363, no. 1502 (April 18, 2007): 2393–413. http://dx.doi.org/10.1098/rstb.2007.2068.
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Islands have long provided material and inspiration for the study of evolution and ecology. The West Indies are complex historically and geographically, providing a rich backdrop for the analysis of colonization, diversification and extinction of species. They are sufficiently isolated to sustain endemic forms and close enough to sources of colonists to develop a dynamic interaction with surrounding continental regions. The Greater Antilles comprise old fragments of continental crust, some very large; the Lesser Antilles are a more recent volcanic island arc, and the low-lying Bahama Islands are scattered on a shallow oceanic platform. Dating of island lineages using molecular methods indicates over-water dispersal of most inhabitants of the West Indies, although direct connections with what is now southern Mexico in the Early Tertiary, and subsequent land bridges or stepping stone islands linking to Central and South America might also have facilitated colonization. Species–area relationships within the West Indies suggest a strong role for endemic radiations and extinction in shaping patterns of diversity. Diversification is promoted by opportunities for allopatric divergence between islands, or within the large islands of the Greater Antilles, with a classic example provided by the Anolis lizards. The timing of colonization events using molecular clocks permits analysis of colonization–extinction dynamics by means of species accumulation curves. These indicate low rates of colonization and extinction for reptiles and amphibians in the Greater Antilles, with estimated average persistence times of lineages in the West Indies exceeding 30 Myr. Even though individual island populations of birds might persist an average of 2 Myr on larger islands in the Lesser Antilles, recolonization from within the archipelago appears to maintain avian lineages within the island chain indefinitely. Birds of the Lesser Antilles also provide evidence of a mass extinction event within the past million years, emphasizing the time-heterogeneity of historical processes. Geographical dynamics are matched by ecological changes in the distribution of species within islands over time resulting from adaptive radiation and shifts in habitat, often following repeatable patterns. Although extinction is relatively infrequent under natural conditions, changes in island environments as a result of human activities have exterminated many populations and others—especially old, endemic species—remain vulnerable. Conservation efforts are strengthened by recognition of aesthetic, cultural and scientific values of the unique flora and fauna of the West Indies.
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Sepúlveda, P., J. P. Le Roux, L. E. Lara, G. Orozco, and V. Astudillo. "Biostratigraphic evidence for dramatic Holocene uplift of Robinson Crusoe Island, Juan Fernández Ridge, SE Pacific Ocean." Biogeosciences 12, no. 6 (March 27, 2015): 1993–2001. http://dx.doi.org/10.5194/bg-12-1993-2015.
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Abstract. Hotspot oceanic islands typically experience subsidence due to several processes related to migration of the oceanic plate away from the mantle plume and surface flexural loading. However, many other processes can interrupt subsidence, some of which may be associated with catastrophic events. A study of the biostratigraphy and sedimentology of Holocene deposits on Robinson Crusoe Island (RCI) on the Juan Fernández Ridge (JFR) indicated that dramatic uplift has occurred since 8000 years BP, at a rate of about 8.5mm yr-1. This is evidenced by supratidal flats with tepee structures and sand layers containing marine gastropods (mostly Nerita sp.) that are now exposed ca. 70 m a.s.l. The active hotspot is located 280 km further west and the last volcanic activity on RCI occurred at ca. 800 000 years BP. Long-term subsidence is evidenced by deep submerged marine abrasion terraces at RCI. As no direct evidence was found for the existence of a compensating bulge generated by the present hotspot upon which RCI would be situated, it must be concluded that subsidence in the wake of the mantle plume beneath the migrating plate was interrupted by very rapid uplift, but on a scale that did not fully compensate for the previous subsidence. This can be attributed to large-scale landslides followed by isostatic rebound, although this is only vaguely reflected in the low-resolution bathymetry of the area. To determine if this mechanism produced the uplift, a detailed bathymetric survey of the area will be required. If such a survey confirms this hypothesis, it may have implications for the short-term dynamics of vertical variations of oceanic edifices and their related effects on ecosystems and human population.
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Paris, R., H. Guillou, J. C. Carracedo, and F. J. Perez Torrado. "Volcanic and morphological evolution of La Gomera (Canary Islands), based on new K–Ar ages and magnetic stratigraphy: implications for oceanic island evolution." Journal of the Geological Society 162, no. 3 (May 2005): 501–12. http://dx.doi.org/10.1144/0016-764904-055.
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Rodríguez, Fátima, Nemesio M. Pérez, Eleazar Padrón, Gladys Melián, Pedro A. Hernández, María Asensio-Ramos, Samara Dionis, et al. "Diffuse Helium and Hydrogen Degassing to Reveal Hidden Geothermal Resources in Oceanic Volcanic Islands: The Canarian Archipelago Case Study." Surveys in Geophysics 36, no. 3 (March 13, 2015): 351–69. http://dx.doi.org/10.1007/s10712-015-9320-8.
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Heller, Paul L., Rowland W. Tabor, and Christopher A. Suczek. "Paleogeographic evolution of the United States Pacific Northwest during Paleogene time." Canadian Journal of Earth Sciences 24, no. 8 (August 1, 1987): 1652–67. http://dx.doi.org/10.1139/e87-159.
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Paleogeographic reconstructions for Oregon and Washington during Paleogene time illustrate a major transition from a dominantly compressional (prior to middle Eocene time) to an extensional tectonic regime. This transition resulted in the development of three phases of Paleogene basin evolution in the United States Pacific Northwest. During the initial phase, basins formed along the continental margin during collision of oceanic islands. Sediments in these basins were derived from nearby orogenic highlands. The second phase of basin development began in middle Eocene time and consisted of rapid subsidence of individual basins that formed within a broad forearc region. Nonmarine basins that formed during this phase were caused by extension possibly associated with transcurrent faulting. Rapid sedimentation in both marine and nonmarine basins during this time consisted dominantly of sandstone derived from Cretaceous plutonic sources far to the east. The final stage of basin development was the modification of previous basin configurations by the growth of the Cascade volcanic arc, which was initiated in early Oligocene time. The rising Cascade Range diverted streams carrying eastern-derived material, thereby reducing overall sedimentation rates in the coastal basins and providing a local source of volcanic detritus.