Continental Island Research Articles

Tectonic Evolution of the West Bogeda: Evidences from Zircon U-Pb Geochronology and Geochemistry Proxies, NW China

The Bogeda Shan (Mountain) is in southern part of the Central Asian Orogenic Belt (CAOB) and well preserved Paleozoic stratigraphy, making it an ideal region to study the tectonic evolution of the CAOB. However, there is a long-standing debate on the tectonic setting and onset uplift of the Bogeda Shan. In this study, we report detrital zircon U-Pb geochronology and whole-rock geochemistry of the Permian sandstone samples, to decipher the provenance and tectonic evolution of the West Bogeda Shan. The Lower-Middle Permian sandstone is characterized by a dominant zircon peak age at 300–400 Ma, similar to the Carboniferous samples, suggesting their provenance inheritance and from North Tian Shan (NTS) and Yili-Central Tian Shan (YCTS). While the zircon record of the Upper Permian sandstone is characterized by two major age peaks at ca. 335 Ma and ca. 455 Ma, indicating the change of provenance after the Middle Permian and indicating the uplift of Bogeda Shan. The initial uplift of Bogeda Shan was also demonstrated by structural deformations and unconformity occurring at the end of Middle Permian. The bulk elemental geochemistry of sedimentary rocks in the West Bogeda Shan suggests the Lower-Middle Permian is mostly greywacke with mafic source dominance, and tectonic setting changed from the continental rift in the Early Permian to post rift in the Middle Permian. The Upper Permian mainly consists of litharenite and sublitharenite with mafic-intermediate provenances formed in continental island arcs. The combined evidences suggest the initial uplift of the Bogeda Shan occurred in the Late Permian, and three stages of mountain building include the continental rift, post-rift extensional depression, and continental arc from the Early, Middle, to Late Permian, respectively.

The venom variability of the Bothrops jararaca complex and its correlation with the speciation processes in continental islands

The venom variability of the Bothrops jararaca complex and its correlation with the speciation processes in continental islands

Endemic and alien vascular plant diversity in the small Mediterranean islands of Sardinia: Drivers and implications for their conservation

Islands are of high interest for conservationists, due to their great biodiversity within discrete territories. Nonetheless, several mechanisms of plant diversity patterns are unknown, especially for continental islands. In this paper, we explored how endemic and alien vascular plant species richness and the compositional dissimilarity of small Mediterranean continental islands vary according to factors related to human activities, geography/landscape, and climate. Actions for endemic plant conservation were also prioritised according to both endemic and alien components. To this aim, data of endemic and alien plant species for forty islands of Sardinia were considered. Species-area residuals, which express the actual species composition free of area-effects, were modelled using 19 variables related to anthropogenic, geographic/landscape and climatic domains (group of factors). The geographic/landscape domain appeared to be important for both endemic and alien species richness and compositional dissimilarity, while the climatic one was especially relevant for alien species richness. The anthropogenic domain was mostly important for the compositional dissimilarity of aliens and for the endemic species richness. Actions for endemic plant conservation were of high priority for 14 islands; 11 of which are located off the northwest coast of Sardinia. Our research confirms that the Mediterranean small islands of Sardinia are plant endemism hotspots prone to alien invasion. Our findings suggest that removing anthropogenic disturbances is not sufficient to prevent plant invasions. Other factors related to climatic and geographic/landscape domains are as or more important in determining endemic and alien plant composition.

How long have dogs been in Melanesia? New evidence from Caution Bay, south coast of Papua New Guinea

Currently the earliest evidence for dog dispersal into the Greater Australian region and surrounds is found in Australia (Madura Cave 3210–3361 cal BP), New Ireland (Kamgot, c. 3000–3300 cal BP) and Timor-Leste (Matja Kuru 2, 2886–3068 cal BP). Previously, the earliest published dog remains for the large continental island of New Guinea was from Edubu 1 (2314–2700 cal BP) in Caution Bay, south coast of mainland PNG. Here we report on a dog mandible from Moiapu 1, also in Caution Bay. Although the mandible could not be directly dated, good chronostratigraphic resolution indicates that it confidently dates to between 2573 and 2702 cal BP (95% probability). It was found deeply buried in association with Late Lapita cultural materials, and is currently the earliest known dog remain from New Guinea. Biometric measurements on a small sample of archaeological and modern dog remains from the broader region support previously published models (based on genetic results) of multiple dog dispersals into the Pacific region.

Islands as a crossroad of evolutionary lineages: A case study of Centaurea sect. Centaurea (Compositae) from Sardinia (Mediterranean Basin).

The Mediterranean Basin is a biodiversity hotspot, where islands play a key role because of their high biological diversity, degree of endemicity and human pressure. One of these islands, Sardinia, is a good evolutionary laboratory, especially for the study of complex genera, such as Centaurea. In particular, endemic species of Centaurea sect. Centaurea from Sardinia provides an interesting case study of plant evolution on continental islands. We attempted to clarify the processes leading to the diversification of Centaurea species on Sardinia using bi-parentally inherited nuclear markers and maternally inherited plastid markers. Our plastid results revealed the presence of five lineages of sect. Centaurea on the island. Three of them were defined as three species: C. ferulacea, C. filiformis and C. horrida. The other two lineages highlighted the complex evolutionary history of the two polyploids C. corensis and C. magistrorum. Multiple colonization events from the mainland involving the C. deusta and C. paniculata lineages among others, have led to the diversity of sect. Centaurea on Sardinia. One colonization event likely followed a southern path via the land connection between the mainland, the Calabrian Plate and Sardinia. A second pathway likely followed a northern connection, probably through the Tuscan Archipelago. Implications of these findings on conservation efforts for Centaurea endemics on Sardinia are also discussed.

Species–area relationship and small‐island effect of bryophytes on the Zhoushan Archipelago, China

AbstractAimThe species–area relationship (SAR) and the small‐island effect (SIE) are of important ecological significance. However, few studies have focused on these topics in regard to bryophytes. We aimed to (1) determine whether SIEs and a SAR with two thresholds and three different processes of species addition exist for bryophytes across continental islands and (2) test whether the SIE threshold tends to be high for stenoecious species with a high sensitivity to habitats and for those with relatively high resource requirements and low dispersal abilities.LocationThe Zhoushan Archipelago, China.TaxonBryophytes.MethodsWe obtained species number data for five bryophyte categories (total bryophytes, total mosses, acrocarpous mosses, pleurocarpous mosses and liverworts) from 66 continental islands of the archipelago and analysed the dataset using 24 SAR models. According to Akaike's information criterion, we identified models suitable for revealing SARs and detecting SIEs among the five bryophyte categories.ResultsThe power model was best for fitting SARs of all bryophyte categories except for pleurocarpous mosses. For detecting SIEs, the three‐segmented model provided the best support for the five categories. There were obvious SIEs for the five bryophyte groups, with area thresholds of 0.11–1.42 km2. The SIE threshold was much higher in liverworts than in mosses and in pleurocarpous mosses than in acrocarpous mosses. The second thresholds for the five categories were similar, ranging from 53.62 to 73.19 km2.Main conclusionsA unique SAR pattern with two area thresholds and three different dominant processes of species addition with island area was found for bryophytes across the continental islands. The second thresholds were not due to in situ speciation but were likely due to the high immigration of bryophytes from the mainland attributed to local residents. The SIE thresholds detected for the different categories of bryophytes indicated that the values tended to be low for species groups with low resource requirements and high dispersal abilities and high for those with a high sensitivity to habitat conditions, the latter indicating that areas for conservation purposes for species sensitive to habitats should be comparatively large.

Biological and ecological notes about the snapping shrimp Alpheus formosus Gibbes, 1850 from two continental islands in São Paulo State - Brazil

Abstract While previous studies on Alpheus formosus Gibbes, 1850 focused on taxonomic and phylogenetic issues, the present study provides information on the biology and ecology of this snapping shrimp, a representative coral reef species widely distributed in the Atlantic Ocean. We studied A. formosus between 2015 and 2016 on two islands in Sao Paulo state, Brazil: Laje de Santos and Vitoria Island. We analyzed 47 specimens from Laje de Santos and 44 from Vitoria Island. Individuals ranged in size from 2.0 mm to 13.99 mm CL. The mean number of embryos attached to the pleopods of females was 211.28 ± 312.8 in Laje de Santos and 125.2 ± 177.8 in Vitoria Island. This species should be included in monitoring programs of coral ecosystems they inhabit as A. formosus represents a key element in trophic dynamics of these ecosystems.

A tale of two islands: evidence for impaired stress response and altered immune functions in an insular pit viper following ecological disturbance.

The frequency and intensity of ecological perturbations affecting wild animal populations is expected to increase in the future with animals facing numerous global threats. Seahorse Key is a continental island off mainland Florida that has historically been a major rookery for several species of waterbirds. As a result of an unknown disturbance, the entire rookery abandoned Seahorse Key in April 2015 and shifted nesting activities to nearby Snake Key, resulting in an influx of food resources in the form of fish carrion to resident Florida cottonmouth snakes (Agkistrodon conanti), while snakes on Seahorse Key experienced a drastic reduction in food resources. Our objective was to assess plasma corticosterone concentrations, corticosterone negative feedback using dexamethasone, blood glucose, body condition, packed cell volume, natural antibody agglutination, white blood cell counts and ratios and erythrocyte sedimentation rate to characterize the long-term effects of differential resource availability in these two snake populations 3years after this major ecological disturbance. We collected blood samples at three time points from cottonmouths on Seahorse Key (n = 6 individuals) and Snake Key (n = 13 individuals) in fall 2018. In due consideration of the small sample size, our study shows evidence that 3years after the shift in waterbird nesting Seahorse Key cottonmouths exhibit a dampened acute stress response and presumptive impaired innate immune functions relative to cottonmouths on Snake Key. These results highlight the context-dependent nature of biomarkers and implicate the significant decrease in food resources on Seahorse Key in altering hormonal stress responses and innate immune functions, possibly leading to unknown long-term downstream effects. This study assessed the response of a wild population of pit viper to ecological disturbance in situ with the aim to improve our understanding of how animals cope with such perturbations and improve our capacity to make informed decisions for conservation.

Can differences between continental and insular habitats influence the parasites communities associated with the endemic frog Haddadus binotatus?

Habitats characterized by geographic isolation such as islands have been studied using different organisms as models for understanding the dynamic and insular patterns of biodiversity. Determinants of parasite richness in insular host populations have been conducted mainly with mammals and birds, showing that parasite richness decreases in insular areas. In the present study, we predicted that the type of environment (insular or continental) can influence the richness, diversity and abundance of parasites associated with the endemic frog Haddadus binotatus (Spix, 1824). We sampled frogs in two insular and two mainland fragments to survey their helminth parasites. The total richness was composed of 15 taxa of Nematoda and two of Acanthocephala, and the community composition of the two islands had more similarities between them than the two mainland localities. The insular effect was positive for richness and abundance of helminths, and no significant effect was observed on helminth diversity - even the mean diversity presented high numbers for the islands. We presumed that insular hosts could have lost some parasites in the colonization process when these continental islands were separated from the mainland, approximately 11,000 years ago. However, the high richness and abundance on islands can be explained by an epidemiological argument, which considers high population density due to insularity and other features of the host as factors that increase parasite transmission success among individuals.

Mineralogical and geochemical composition of the subsurface sediments at the mouth of Wadi Al- Hamd, Red Sea coast, Saudi Arabia: implication for provenance and climate

The present work is related to mineralogy and geochemistry of sedimentary successions of the modern Red Sea coastal plain at the mouth of Wadi Al-Hamd, Northern Saudi Arabia. It identifies the provenance, weathering effect, and paleoenvironment of the area. The mineralogical composition is dominated by quartz, plagioclase, and trace of feldspars, clay minerals, mica, and hornblende. Additionally, traces of non-detrital minerals including high and low Mg calcite, dolomite, halite, and anhydrite were locally detected. Four chemo-facies, dominated by three associations of element groups linked with detrital minerals, grain size properties, and biogenic products were recognized. The mineralogical and geochemical indices showed that sediments were derived from the intermediate igneous rocks at active continental margin and continental island arc settings. Weathering indices showed that the sediments were poorly weathered, consistent with the arid-to-semi-arid climate of the area. The spatial and vertical variations of mineralogical and chemical composition reflect variation depositional environments, hydraulic sorting, and the influence of coastal processes.

Mesozoic sooty mould beetles as living relicts in New Zealand.

New Zealand is an island continent that completed its split from the Gondwanan continent at 52 Ma, harbouring an iconic biota of tuatara, kiwi and weta. The sooty mould community is a distinctive trophic element of New Zealand forest ecosystems that is driven by plant-feeding sternorrhynchan Hemiptera. These produce honeydew, which supports fungal growth, which in turn supports numerous endemic invertebrates, including endemic New Zealand beetle families. Ancient New Zealand insect fossils are rare but a single fossil of a sooty mould cyclaxyrid was recently described from Cretaceous Burmese amber, a family that was previously known from two extant New Zealand species. Well-preserved fossils like this one are recasting Earth history, and, based on a wealth of additional specimens, we re-evaluate the taxonomy of Cretaceous cyclaxyrids and one Eocene species here transferred to Cyclaxyridae. Cyclaxyridae are highly tied to the sooty mould community and have now been discovered to occur in disparate biogeographic realms in deep time. Our discovery indicates that the family, and perhaps the sooty mould community in general, was widespread in Pangaea from at least the Cretaceous and survived as a relict in New Zealand. Persistence of a sooty mould ecosystem in New Zealand and fungal specialization may not necessarily be an evolutionary 'dead-end' for cyclaxyrids and other insects.

Geochronology and geochemistry of volcanic rocks of the Bima Formation, southern Lhasa subterrane, Tibet: Implications for early Neo-Tethyan subduction

Bima Formation volcanic rocks, which record the history of Neo-Tethyan subduction, are found within the central and eastern segments of the southern Lhasa subterrane, Tibetan Plateau. Zircon UPb dating, whole-rock major and trace element analysis, and Sr–Nd–Pb–Hf isotopic compositions of Bima Formation volcanic rocks from the central segment of the southern Lhasa subterrane were used to constrain the magmatic and tectonic evolution of the Lhasa terrane during the early Mesozoic. Zircon UPb dating of five samples yielded consistent ages of 184.3 ± 2.4 to 176.8 ± 3.5 Ma. The dominant volcanic rock types within the Bima Formation are basalts, basaltic andesites, andesites, and dacites, which are enriched in the large-ion lithophile elements (e.g., Rb, Sr, and Ba) and depleted in high-field-strength elements (e.g., Nb, Ta, and Ti). (87Sr/86Sr)t ratios are low (0.702900–0.704146), εNd(t) and εHf(t) values are high and positive (+4.4 to +6.9 and + 9.6 to +15.7, respectively), and Pb isotope ratios are homogeneous (initial 206Pb/204Pb = 18.28–18.40; 207Pb/204Pb = 15.53–15.56; 208Pb/204Pb = 38.21–38.38). Combining the new data with those from a previous study of Bima Formation volcanic rocks from the eastern segment of the southern Lhasa subterrane indicates that the Bima Formation formed between the Middle Triassic and Early Jurassic. It suggests that more widespread early Mesozoic volcanic rocks in the southern margin of the Lhasa terrane. The basaltic rocks of the Bima Formation were generated by partial melting of a depleted mantle wedge metasomatized by slab-derived fluids, and subsequently experienced fractional crystallization without significant crustal contamination. The andesitic and dacitic rocks were formed by fractional crystallization of the basaltic magma. Our study indicates that the Bima Formation volcanic rocks were generated within a continental island arc setting related to northward subduction of the Neo-Tethyan oceanic slab during the early Mesozoic.

Pre-gabi biotic connections between the Americas:: an alternative model to explain the “less-splendid isolation” of South America

Traditionally, South America was considered as an island continent during most of the Tertiary. However, sparse paleontological and biological evidence indicates that a biotic interchange between North and South America may have been occurred by pre-Pliocene times. Nevertheless, the geological evidence suggesting Miocene closure of the Isthmus is still wanting, and this constitutes an important inconsistency between biological and geological data. With the aim to explain the population of Caribbean islands by terrestrial fauna and flora, several authors proposed that between Eocene and Oligocene times there existed an above-water land span between South America and these islands, currently known as GAARlandia. If this is the case, there must have been biotic interchanges between the Americas and Caribbean islands in a narrow time window. This new hypothesis has deep implications for the understanding of the early phases of the biotic interchange between the Americas by pre-Pliocene times.

Tale of two islands. The reality of large-scale extinction in the early stages of the Anthropocene: a lack of awareness and appropriate action

The endemic biotas of oceanic islands were vulnerable and many have been lost. The more ancient, complex and dynamic biotas of continents were more resilient but are now being obliterated. Sumatra and Madagascar are large continental plate islands with very different histories and biotas that exemplify the situation on continental land masses. Both tropical islands have suffered massive habitat loss and species extinction from human population pressure, Sumatra mostly from global and Madagascar from local pressure. Snails demonstrate the complex history of faunal origins as illustrated by the relationships between Madagascan, Indian and southeast Asian snail faunas and their plate tectonic geological history. Snails also reveal our limited knowledge of the details but not the scope of extinctions through habitat loss. International agencies are failing to address the root causes of natural habitat loss and consequent extinctions, which are overpopulation and an economic system based on perpetual growth. The fallacy of sustainable development and the limitations of current conservation practice are addressed. Recognition that we cannot stop extinctions in the immediate future demands a new, supplementary approach to conservation based on advances in molecular technology.

Petrogenesis of Middle Triassic andesite in Sayaburi area, Laos: Constraints from whole-rock geochemistry, zircon U-Pb geochronology, and Sr-Nd isotopes

Despite the presence of a large area of andesite in the Sayaburi Province of Laos, it has received very little attention. Based on a combination of detailed field investigations, geochronology and geochemical analysis, this study aims to explore the geochemical, Sr-Nd isotopic, and source rock characteristics, as well as the genesis and tectonic setting of the andesite in this region. In the Sayaburi Province, the andesite zircon U-Pb age is (241.2±1.2) Ma. The andesite rock is classified in the metaluminous-weak peraluminous calc-alkaline series. The light rare-earth elements (LREEs) are enriched and characterized by clear fractionation, whereas heavy rare-earth elements (HREEs) are relatively depleted and have no signs of fractionation. The average δEu is 0.96 with weak-or-no Eu anomalies. It is enriched in large ion lithophile elements such as Rb and K, while depleted in high field-strength elements such as Nb, Ta, P and Ti. For andesites in the Sayaburi Province, the (87Rb/86Sr)t value ranges in 0.702849–0.704687, the eNd(t) value is between 3.53 and 4.77, the tDM(t) value ranges in 633–835 Ma, and the tDM2(t) ranges in 625–724 Ma. The results based on the synthesis of petrology, geochemistry, and regional tectonic background studies show that 1) the andesitic magma source in the study area is an enriched mantle, which is modified by subduction zone fluids; 2) the geotectonic background environment of the andesite in Sayaburi area is the continental island arc environment and related to the tectonic evolution of Jinghong-Nan-Uttaradit back-arc basin, which reflects that the magmatic source is enriched with a mantle wedge component modified by a subduction zone fluid (or melt).

Petrography and Geochemistry of the Upper Triassic Sandstones from the Western Ordos Basin, NW China: Provenance and Tectonic Implications

Petrographic and geochemical characteristics of the Upper Triassic sandstones in the western Ordos Basin were studied to provide insight into weathering characteristics, provenance, and tectonic implications. Petrographic features show that the sandstones are characterized by low‐medium compositional maturity and textural maturity. The CIA and CIW values reveal weak and moderate weathering history in the source area. The geochemical characteristics together with palaeocurrent data show that the northwestern sediments were mainly derived from the Alxa Block with a typical recycled nature, while the provenance of the western and southwestern sediments were mainly from the Qinling‐Qilian Orogenic Belt. The tectonic setting discrimination diagrams signify that the parent rocks of sandstones in the western and southern Ordos Basin were mainly developed from continental island arc, which is closely related to the evolution of the Qinling‐Qilian Orogenic Belt. However, the sandstones in the northwestern Ordos Basin show complex features, which may be resulted from a typical recycling process. Overall evidence from petrography, geochemistry and sedimentology, together with previous researches suggest the Kongtongshan and Helanshan areas were the southwestern and northwestern boundary of the Ordos Basin, respectively, and there was no clear boundary between the Hexi Corridor Belt and Ordos Basin, where a large, uniform sediment dispersal system developed during the Late Triassic.

Provenance of Cretaceous Dasheng Group Malanggou Formation in the mid-part of the Yishu fault zone, Shandong Province, China

The Yishu fault zone has an important impact on sedimentary formation, magmatism, and mineralization in Shandong Province of eastern China. Determining the sedimentary source, tectonic setting, and age of the Cretaceous Dasheng Group Malanggou Formation is of great significance for clarifying the relationship between the tectonic evolution and mineralization of the Yishu fault zone. In order to decipher the source characteristics and associated sedimentary setting, elemental geochemistry and detrital zircon U–Pb geochronology of sandstones in the Malanggou Formation within the mid-part of the Yishu fault zone are studied. The results show that the provenance of the Malanggou Formation in the Dasheng Group was dominated by felsic volcanic rocks, and its sedimentation was in an arid and oxidized climate environment. The provenance of the Malanggou Formation was in a continental island arc setting. The major element concentrations and CIA value indicate that the Malanggou Formation has suffered weak chemical weathering. The abrasion of quartz and the trace element concentrations indicate that the Malanggou Formation is a set of proximal deposit. Detrital zircon age of the sandstone in Malanggou Formation can be divided into two age groups: 117–141 and 1852–2499 Ma. According to the age data of 117–141 Ma, the western Shandong uplift should be the main provenance of the Malanggou Formation, while according to the age data of 1852–2499 Ma, the Yishui Group in the Gongdanshan uplift had a certain contribution to the provenance of the Malanggou Formation.

Sedimentary source area and paleoenvironmental reconstruction since late Miocene in the southern South China Sea

The South China Sea (SCS) is the largest marginal sea of the Western Pacific and is located in the low-latitude of the world. The Site 1143 of the Ocean Drilling Program (ODP) Leg 184 in the southern South China Sea provides continuous sedimentary records from late Miocene to Holocene. To better understand the evolution of climate, paleo-productivity and the source of sediments during the 6.0–0.8 Ma period in the southern South China Sea, 36 sediment core samples (45.77–251.36 mcd) were collected and analyzed for major and trace elements. The results show that the provenance area of sediments is in a high intensity of chemical weathering at 6.0–5.2 Ma, and the terrestrial materials input increases due to the combined effect of the Vietnam tectonic uplift and the enhancement of the East Asian summer monsoon, while the precipitation driven by the strengthened East Asian summer monsoon also results in a high paleo-productivity. From 5.2 to 1.7 Ma, the climate in the provenance of sediment has cooled, resulting in a weakening of the marine biological activities and lower marine paleo-productivity. The decrease of Rb/Sr and MgO/CaO and an extremely high Al flux at 3.5–2.5 Ma suggests an erosional response to both the uplift of the Tibetan Plateau and the strengthening of the East Asian summer monsoon. At 6.0–5.2 Ma, the lower content of Mo and the ratios of Ni/Co and Mo/TOC indicate that sediments were deposited in an oxidizing restricted marine environment. During 1.4-1.0 Ma, the lower V/(V+Ni) ratio and the increase of the content of Mo and Mo/TOC reflect a suboxic environment and the gradually increased water cycle in the basin. The tectonic environment of the provenance area might be continental island arc, and granite is a major type of the source rock. The potential provenance area of sediments at Site 1143 might be similar to that of the Mekong River.

Geochemical and mineralogical records of late Albian oceanic anoxic event 1d (OAE-1d) in the La Grita Member (southwestern Venezuela): Implications for weathering and provenance

In this paper, stratigraphic distributions of major, trace and rare earth element (REE) concentrations as well as the bulk and clay mineralogy of organic-rich calcareous rocks of the La Grita Member (Capacho Formation) in southwestern Venezuela were studied to constrain sedimentary depositional conditions during the late Albian-early Cenomanian oceanic anoxic event 1-d (OAE-1d; 103 to 99.5 Ma). The statistically significant correlations observed between total REEs and Al, total organic carbon (TOC) and phyllosilicates suggest that REEs mainly occur in clay minerals and organic matter. Ce anomalies are mainly controlled by detrital input and cannot be used as redox proxies in this stratigraphic sequence. Detrital proxies, notably phyllosilicate/(K-feldspar + plagioclase), K-feldspar/(K-feldspar + plagioclase), and kaolinite/illite, suggest that greenhouse warming established during the OAE-1d intensified the hydrologic cycle and consequently increased continental chemical weathering rates. The Zr/Sc ratio and Al2O3–TiO2–Zr ternary diagram suggest detrital input dominated by recycling of older sedimentary rocks, while the La–Th-Sc ternary relationship indicates that most sediment samples were deposited between a passive margin and a continental island arc setting. Sedimentary discrimination diagrams (including La–Th-Sc and Co/Th vs. La/Sc), combined with chondrite-normalized REE patterns, suggest that siliciclastic sediments of the La Grita Member were mainly supplied by metasedimentary and intracratonic rocks of the Guayana Craton, notably the Roraima Formation, suggesting that this area was the main source for siliciclastic sediments during the Cretaceous. The Santander Massif and Merida and El Baúl Arches likely acted as secondary provenance areas, confirming previous work using U–Pb detrital zircon geochronology.

Seroepidemiological survey of canine visceral leishmaniasis in a continental island of northeast Brazil

<p><strong>Introdução:</strong> Leishmaniose Visceral (LV) é uma doença endêmica em municípios vizinhos à Ilha de Maré, situada na plataforma continental do município de Salvador, Bahia, Brasil. Entretanto, casos de LV não tem sido notificados nesta Ilha. <strong>O</strong><strong>bjetivo</strong>: foi investigar a soroprevalência e sinais clínicos de Leishmaniose Visceral Canina (LVC) e identificar a população de flebótomos presentes no povoado de Botelho, Ilha de Maré. <strong>Metodologia:</strong> Soro de cães locais foram testados para IgG anti-<em>Leishmania </em>por imunoensaios (teste rápido TR DPP™ e Elisa Indireto) e uma investigação entomológica foi conduzida. <strong>Resultados:</strong> 106 amostras foram testadas, sendo que sete (6,6%) foram positivas usando o teste rápido. As amostras positivas foram encaminhadas ao Laboratório Central da Bahia para a confirmação, entretanto, essas amostras apresentaram resultado negativo no ELISA indireto. Foi identificada a presença de nove exemplares da espécie <em>Pressatia choti, </em>subfamília Phlebotominae, espécie frequentemente encontrada em áreas de transmissão de leishmaniose cutânea no Brasil. <strong>Conclusão:</strong> Apesar deste trabalho não ter identificado a presença de LVC na Ilha de Maré, novos inquéritos sorológicos e analises entomológicas em uma maior área da ilha de Maré serão necessários para a manutenção de uma vigilância epidemiológico na região insular em destaque.</p>