Oxygen isotope evidence of Little Ice Age aridity on the Caribbean slope of the Cordillera Central, Dominican Republic

Climate change during the so-called Little Ice Age (LIA) of the 15th to 19th centuries was once thought to be limited to the high northern latitudes, but increasing evidence reflects significant climate change in the tropics. One of the hypothesized features of LIA climate in the low latitudes is a more southerly mean annual position of the Intertropical Convergence Zone (ITCZ), which produced more arid conditions through much of the northern tropics. High-resolution stable oxygen isotope data and other sedimentary evidence from Laguna de Felipe, located on the Caribbean slope of the Cordillera Central of the Dominican Republic, support the hypothesis that the mean annual position of the ITCZ was displaced significantly southward during much of the LIA. Placed within the context of regional paleoclimate and paleoceanographic records, and reconstructions of global LIA climate, this shift in mean annual ITCZ position appears to have been induced by lower solar insolation and internal dynamical responses of the global climate system. Our results from Hispaniola further emphasize the global nature of LIA climate change and the sensitivity of circum-Caribbean climate conditions to what are hypothesized to be relatively small variations in global energy budgets.     

Early island-arc intrusive activity,Cordillera Central,Dominican Republic

Reconnaissance studies of early island-arc intrusions in the Cordillera Central of the Dominican Republic demonstrate that these rocks are mainly hornblende tonalite with lesser amounts of hornblende diorite, quartz diorite, granodiorite and quartz monzonite. Two plutons (El Bao, Medina) are petrographically and chemically homogeneous, whereas two others (El Rio and Loma de Cabrera) are compositionally heterogeneous. Samples from these intrusions range in SiO₂ from 49 to 70% with most rocks in the 59 to 62% range. K₂O ranges from 0.24 to 3% and averages 1.2%. Cu, Zn, Co, Ni, V and possibly Cr decrease with increasing SiO₂. Rb/Sr values for the intrusions are low but variable. Present-day ⁸⁷Sr/⁸⁶Sr values range from 0.7031 to 0.7045 for the El Bao and Loma de Cabrera batholiths and 0.7033 to 0.7091 for the Medina stock. These data do not generate isochrons. The Cordillera Central tonalite intrusions are the most abundant plutonic rock type in the Greater Antilles, although small, younger granodiorite and quartz monzonite stocks are present. The Cordillera Central intrusions are lower in SiO₂, K₂O, Rb, and Sr than the average composition of the Sierra Nevada batholith, but they are similar to the tonalites and trondjhemites from the western margin of the Sierra Nevada batholith. The low Rb/Sr ratios and low initital Sr⁸⁷/Sr⁸⁶ ratios for the Cordillera Central intrusions combined with the high liquidus temperatures required for the generation of tonalite magmas strongly favor a subcrustal source for these magmas in an island-arc setting.     

Magmatic relationships and ages of Caribbean Island arc tholeiites, boninites and related felsic rocks, Dominican Republic

Located in the Cordillera Oriental of the Dominican Republic, the Early Cretaceous Los Ranchos Fm (LRF) comprises a > 3-km thick sequence of volcanic and volcaniclastic rocks with variable geochemical characteristics, which is intruded by tonalite batholiths, minor gabbro/diorite plutons and mafic dykes. From top to bottom, three main stratigraphic units have been mapped: upper basaltic, intermediate rhyodacitic and lower basaltic. Combined detailed mapping, stratigraphy, geochemistry, Rb–Sr/Sm–Nd isotopic studies and U–Pb/Ar–Ar geochronology show that the mafic rocks of the LRF include boninites and LREE-depleted island arc tholeiites (IAT) in the lower unit, both which appear genetically related, whereas normal IAT occur in the upper unit. The source for these rocks is thought to reflect variably depleted mantle, overprinted by a subduction zone component. Contemporaneous Aptian U–Pb zircon ages were obtained for a rhyodacite from the intermediate unit (116.0 ± 0.8 Ma) and a tonalite of the Zambrana batholith (115.5 ± 0.3 Ma) that intrudes the LRF. The similarity of trace element signatures in both units argues for genetic link between the felsic volcanics of the LRF and the tonalite plutonism. Low-K rhyolites and tonalite batholiths are interpreted as products of secondary melting at the base of thickened early arc crust. ⁴⁰Ar/³⁹Ar plateau ages of hornblende in most tonalites are Albian (109–106 Ma) and interpreted as final cooling ages, prior to unroofing and growth of unconformable overlying reef limestones of the Hatillo Fm (112–100 Ma). The LREE-depleted IAT and boninites of lower basaltic unit are interpreted to have formed during subduction zone initiation in the Caribbean Island arc, and the normal IAT of the upper unit are thought to represent the subsequent establishment of the volcanic front.     

A risk analysis for floods and lahars: case study in the Cordillera Central of Colombia

The glacier-covered Nevado del Tolima in the Colombian Cordillera Central is an active volcano with potential lahars that might be more hazardous than those on Nevado del Ruiz. Furthermore, rainfall-triggered floods and landslides notoriously and severely affect the region. For effective disaster prevention, a risk analysis is of primary importance. We present here a risk analysis methodology that is based on the assessment of lahar and rainfall-related flood hazard scenarios and different aspects of vulnerability. The methodology is applied for populated centres in the Combeima valley and the regional capital Ibagué (~500,000 inhabitants). Lahar scenarios of 0.5, 1, 5, and 15?million m³ volume are based on melting of 1, 2, 10, and 25?% of ice, firn and snow, respectively, due to volcanic activity and subsequent lahar formation. For flood modelling, design floods with a return period of 10 and 100?years were calculated. Vulnerability is assessed considering physical vulnerability, operationalized by market values of dwelling parcels and population density, whereas social vulnerability is expressed by the age structure of the population and poverty. Standardization of hazard and vulnerability allows for the integration into a risk equation, resulting in five-level risk maps, with additional quantitative estimate of damage. The probability of occurrence of lahars is low, but impacts would be disastrous, with about 20,000 people and more directly exposed to it. Floods are much more recurrent, but affected areas are generally smaller. High-risk zones in Ibagué are found in urban areas close to the main river with high social vulnerability. The methodology has proven to be a suitable tool to provide a first overview of spatial distribution of risk which is considered by local and regional authorities for disaster risk reduction. The harmonization of technical-engineering risk analysis and approaches from social sciences into common reference concepts should be further developed.     

Defining the forest,defending the forest: Political ecology,territoriality, and resistance to a protected area in the Dominican Republic

Political ecologists have considered the social and economic impacts that nature reserves, national parks and other forms of protected area can have on neighbouring communities, and how this can generate conflicts between them. This paper analyses such conflicts through the lens of territoriality, considering how the way protected area territories are created, delineated, and defined is linked to the social impacts experienced by local people. Conflicts between locals and conservation authorities over protected areas are about rival attempts to define the boundaries of protected areas, who the land should belong to, what it should be used for, and what its purpose is. Yet the ability of local people or conservation authorities to impose their meaning is unequal. It illustrates these processes with the example of a scientific reserve in the Dominican Republic, and a decades-long conflict to define what the reserve should mean, what it should look like, and who it should belong to.     

秦岭东段卢氏盆地始新世沉积序列与气候环境变迁

始新世是新生代重要的暖期,其气候环境的特征与演化备受学界关注。位于秦岭东段的卢氏盆地保存了>1000 m厚的连续的始新世河湖相沉积物,是揭示古气候和环境变化规律的宝贵沉积记录。在前人工作基础上,本研究利用沉积学、古生物学、碎屑年代学等方法对卢氏盆地始新世地层的沉积特征、年代和环境进行了分析。结果表明：1）碎屑磷灰石裂变径迹与碎屑锆石U-Pb年龄指示沉积序列年代晚于约60 Ma,与前人将张家村组-卢氏组化石组合对比到中始新世的结论基本吻合。2）始新统张家村组沉积相演化表现为冲积扇→河流→洪泛平原或滨湖,反映盆地拉张、初期成湖的过程;卢氏组为滨浅湖→深湖/半深湖→滨浅湖或洪泛平原→浅湖/半深湖,反映湖泊开始稳定出现后的扩张、收缩和复活过程;大峪组为河流→洪泛平原→冲积扇,反映湖泊淤满消亡后河流与冲洪积物相继充填的历史。3）沉积相、化石组合、盐类矿物种类揭示中始新世卢氏盆地古气候为半湿润半干旱,地表景观呈现径流活跃、动物种类多样、树木茂盛、发育淡水至微咸水湖的特征,并可能具有一定的季节性。卢氏盆地沉积序列提供了始新世暖期中国中部气候环境变化的重要证据。

     

Garnierites and garnierites: Textures,mineralogy and geochemistry of garnierites in the Falcondo Ni-laterite deposit,Dominican Republic

Garnierites (Ni–Mg-bearing phyllosilicates) are significant ore minerals in Ni-laterites of the hydrous silicate-type. In the Falcondo Ni-laterite deposit (Dominican Republic), garnierites are found within the saprolite horizon mainly as fracture-fillings and thin coatings on joints. Field observations indicate an important role of active brittle tectonics during garnierite precipitation. Different greenish colours and textures can be distinguished, which correspond to different mineral phases, defined according to X-ray diffraction (XRD) and electron microprobe (EMP) analyses: a) talc-like (10 Å-type), b) serpentine-like (7 Å-type), c) a mixture of talc- and serpentine-like, and d) sepiolite-like types. Compositional data indicate continuous Mg–Ni solid solution along the joins lizardite–népouite (serpentine-like), kerolite–pimelite (talc-like) and sepiolite–falcondoite (sepiolite-like). In general, talc-like garnierite is dominant in Falcondo Ni-laterite and displays higher Ni contents than serpentine-like garnierites. EMP analyses showing deviations from the stoichiometric Mg–Ni solid solutions of serpentine and talc are best explained by talc- and serpentine-like mixing at the nanoscale. A detailed textural study by means of quantified X-ray element imaging provides a wealth of new information about the relationships between textural position, sequence of crystallization and mineral composition of the studied garnierite samples. These results indicate several stages of growth with variable Ni content, pointing to recurrent changes in the physical–chemical conditions during garnierite precipitation. In addition, our detailed mineralogical study of the Falcondo garnierites revealed that the different types identified have characteristic H₂O content and SiO₂/MgO ratios, which play important roles during the pyrometallurgy process.     

Biogeochemical exploration for gold at a site in the Cordillera Cantabrica,Spain

Dried leaves of Festuca ovina L. (Gramineae) and Chamaespartium tridentatum (L.) P. Gibbs. sub. sp. cantabricum (Spach.) Riv.-Mart., Izco & Costa (Leguminosae) were systematically collected over areas of gold mineralization in the southern part of the Cordillera Cantabrica and analyzed for gold, arsenic and antimony by neutron activation analysis during biogeochemical exploration for gold. Although both plants indicated similar areas of gold mineralization, anomalies with F. ovina were more pronounced than those with C. tridentatum. Plant gold concentrations were shown to correlate with soil gold concentrations for the one transect examined. Cumulative frequency data were used to estimate the geochemically anomalous areas. It was concluded that biogeochemical exploration for gold was feasible within this geochemical province.     

The tropical storm Noel and its effects on the territory of the Dominican Republic

In the period between the end of October and the beginning of November 2007, the Dominican Republic was hit by the tropical storm Noel, then turned into hurricane in its movement toward the Californian coasts. The passage of Noel was accompanied by huge precipitation especially in the south-western part of the country. In some areas, the rainfall registered in 6 days exceeded 700 mm, i.e., more than two-thirds of the mean annual precipitation. The return periods calculated for this rainfall event vary greatly from region to region: while they locally reach 200 years, such as in San José de Ocoa (50 km west of Santo Domingo), in other areas, as for instance in the territory of the capital Santo Domingo, return periods do not exceed 20 years. The tropical storm caused huge damage both in terms of human victims and economic losses, related to diffused inundations and landslide phenomena, which may be attributed only partially to the exceptionality of the event. As a matter of fact, in many regions, the inadequate answer of the territory—widely characterized by serious problems of land degradation and an almost complete lack of territorial planning—appears to be the major responsible for the occurred negative effects. The impact assessment, based on the calculation of an Impact Index, confirms this statement.     

A multi-proxy lacustrine record of Holocene climate change on northeastern Baffin Island, Arctic Canada

Reconstructions of past environmental changes are critical for understanding the natural variability of Earth's climate system and for providing a context for present and future global change. Radiocarbon-dated lake sediments from Lake CF3, northeastern Baffin Island, Arctic Canada, are used to reconstruct past environmental conditions over the last 11,200 years. Numerous proxies, including chironomid-inferred July air temperatures, diatom-inferred lakewater pH, and sediment organic matter, reveal a pronounced Holocene thermal maximum as much as 5°C warmer than historic summer temperatures from 10,000 to 8500 cal yr B.P. Following rapid cooling 8500 cal yr B.P., Lake CF3 proxies indicate cooling through the late Holocene. At many sites in northeastern Canada, the Holocene thermal maximum occurred later than at Lake CF3; this late onset of Holocene warmth is generally attributed to the impacts of the decaying Laurentide Ice Sheet on early Holocene temperatures in northeastern Canada. However, the lacustrine proxies in Lake CF3 apparently responded to insolation-driven warmth, despite the proximity of Lake CF3 to the Laurentide Ice Sheet and its meltwater. The magnitude and timing of the Holocene thermal maximum at Lake CF3 indicate that temperatures and environmental conditions at this site are highly sensitive to changes in radiative forcing.     

永吉高速公路黑潭坪边坡三维稳定性研究

通过对永吉高速公路黑潭坪边坡的野外调查,详细地了解了研究区工程地质条件,探讨了边坡变形破坏机理,结合室内试验和计算反演获取岩土体强度参数,在此基础上建立三维地质模型,运用FLAC3D数值分析软件采用强度折减法对不同工况下的坡体稳定性进行详细分析并提出治理建议。研究表明:(1)边坡变形破坏是内外因素综合作用的结果,岩土体性质不良是边坡变形破坏的内在因素,坡脚便道开挖和地表水下渗是边坡变形破坏的诱导因素;(2)强度折减法应用于边坡三位稳定性分析具有较好的适用性;(3)数值模拟显示采用削坡结合锚固的综合治理措施具有明显的效果。     

Palynological evidences on paleoclimate and paleoenvironmental changes during Holocene of Al-Hussaynia District,Central Iraq

This paper is concerned with the study of paleoclimate and paleoenvironmental changes of Hussaynia township which is located in Karbala at the center of the Mesopotamian plain during Holocene. Ten soil samples were examined to determine their content of pollens, spores, and marine organisms (dinoflagellates). These palynomorphs include: Graminidites, Palmaepollenites, Chenopodiaceae, Composita, Cyperaceae, Sphaginum sporites, Pinus pollenites, Convovolus, Artimesia, Laevigatosporites, Quercus, dinoflagellates, and fungi. The study revealed climatic and environmental changes in the area during Holocene and four climatic zones were determined in the studied sequence and correlated with other areas in and outside of Iraq. The climate was pluvial with intervening dry periods in the 10000 years?bp. The study indicated as well, some marine effects on the studied area on the commencement of Holocene due to the global transgression. This is based on the presence of marine organisms, dinoflagellate.     

Palaeomagnetism of the Guaniguanico Cordillera, western Cuba: a pilot study

A palaeo- and rock-magnetic study was carried out on the Jurassic–Cretaceous Guaniguanico Cordillera (15 sites, 112 oriented cores) in order to define a preliminary magnetostratigraphy and to obtain some constraints on the tectonic evolution of western Cuba. Rock-magnetic experiments indicate Ti-poor titanomagnetites as principal remanence carriers. Two magnetic phases seem to be present in a few samples: some spinels, which saturate at moderate magnetic fields and goethite, with higher coercivity. The presence of hematite (or mixture of spinels and hematite) is apparent in two units. In most cases the characteristic palaeodirections could be determined above 300°C. Eleven sites yield normal magnetic polarity and four reverse. The polarity zones can be tentatively correlated to chrons CM29–C24 in the reference geomagnetic polarity time scale. The mean palaeodirection calculated from all sites is Dm=335.7°, Im=43.1°, K=11, α₉₅=12.3 and N=15. The corresponding palaeopole is Plat=66.4°, Plong=205.8°, K=13, and A₉₅=11.1. This pole is not significantly different from North American Jurassic–Cretaceous poles. This suggests that no major latitudinal displacements and deformation have occurred since the Jurassic, in contrast to some previously proposed tectonic models.     

Uneven socio-ecologies of Hispaniola: Asymmetric capabilities for climate adaptation in Haiti and the Dominican Republic

This article adopts a “capabilities” approach to climate justice to examine a globally unique phenomenon: a decade of unprecedented surface area growth in Lake Azuéi (the largest lake in Haiti) and Lake Enriquillo in the Dominican Republic (the largest lake in the Caribbean region). The objective was to explore how two neighbouring communities and their governments respond to large-scale environmental change within connected but uneven political ecological contexts. Current climate change impacts in this bi-national island present an opportunity to better understand not only local climate justice but also how fragmented sovereignty, territoriality, and citizenship regimes may affect processes of climate adaptation. The researchers conducted 27 semi-structured interviews in the Dominican Republic and 11 in Haiti, with open ended questions. The data analysis explores impacts of the lakes’ growth; perceived causes and solutions; access to assistance; views on responsibility; and capacities for mobilization, bi-national cooperation, and international partnerships. The article argues that different capabilities for climate adaptation are shaped by historical path dependencies, local institutional contexts, and international linkages; and that attaining climate justice requires attention to these factors within a collective normative framework. The conclusion examines how climate science, research partnerships, and citizen participation might be leveraged to help build binational adaptation strategies grounded in a capabilities approach to climate justice.     

Seismic hazard maps of Mexico, the Caribbean, and Central and South America

The growth of megacities in seismically active regions around the world often includes the construction of seismically unsafe buildings and infrastructures due to an insufficient knowledge of existing seismic hazard and/or economic constraints. Minimization of the loss of life, property damage, and social and economic disruption due to earthquakes depends on reliable estimates of seismic hazard. We have produced a suite of seismic hazard estimates for Mexico, the Caribbean, and Central and South America. One of the preliminary maps in this suite served as the basis for the Caribbean and Central and South America portion of the Global Seismic Hazard Map (GSHM) published in 1999, which depicted peak ground acceleration (pga) with a 10% chance of exceedance in 50 years for rock sites. Herein we present maps depicting pga and 0.2 and 1.0 s spectral accelerations (SA) with 50%, 10%, and 2% chances of exceedance in 50 years for rock sites. The seismicity catalog used in the generation of these maps adds 3 more years of data to those used to calculate the GSH Map. Different attenuation functions (consistent with those used to calculate the U.S. and Canadian maps) were used as well. These nine maps are designed to assist in global risk mitigation by providing a general seismic hazard framework and serving as a resource for any national or regional agency to help focus further detailed studies required for regional/local needs. The largest seismic hazard values in Mexico, the Caribbean, and Central and South America generally occur in areas that have been, or are likely to be, the sites of the largest plate boundary earthquakes. High hazard values occur in areas where shallow-to-intermediate seismicity occurs frequently.     

Holocene climate in the subarctic fjord Malangen, northern Norway: a multi-proxy study

A Holocene sedimentary record from the deep-silled Malangen fjord in northern Norway reveals regional changes in sedimentary environment and climate. Down-core analysis of two sediment cores includes multi-core sensor logging, grain size, x-radiography, foraminifera, oxygen isotopes, dinoflagellates, pollen, trace elements and radiocarbon datings. The cores are located just proximal to the submarine Younger Dryas moraine complex, and reveal the deglaciation after Younger Dryas and the postglacial evolution. Five sedimentary units have been identified. The oldest units, V and IV, bracket the Younger Dryas glacial readvance in the fjord between 12 700 cal. years BP and 11 800 cal. years BP. This is followed by deposition of glaciomarine sediments (units IV and III) starting around 12 100 cal. years BP. Glaciomarine sedimentation ceased in the fjord c. 10 300 cal. years BP and was replaced by open marine sedimentation (units II and I). A rapid stepwise warming occurred during the Preboreal. Onset of surface water warming lagged bottom water warming by several hundred years. The δ[Formula: See Text]O record indicates a significant, gradual bottom water cooling (c. 4°C) between 8000 and 2000 cal. years BP, a trend also supported by the other proxy data. Other records in the region, as well as GCM simulations, also support this long-term climatic evolution. Superimposed on this cooling were brief warmings around 6000 cal. years BP and 2000 cal. years BP. The long-term change may be driven by orbitally forced reduction in insolation, whereas the short-term changes may be linked to for example solar forcing, meltwater and NAO changes all causing regional changes in the North Atlantic heat transport.     

Sr-Nd isotopic constraints on the petrogenesis of the Central Bohemian Pluton,Czech Republic

The Sr-Nd isotopic data for selected granitoids of the Central Bohemian Pluton show a broad negative correlation with the total range of (⁸⁷Sr/⁸⁶Sr)₃₃₀ = 0.7051–0.7129 and _Nd ³³⁰ = +0.2 to –8.9. The older intrusions have more depleted Sr-Nd compositions and calc-alkaline geochemistry (Sázava suite), whereas the younger intrusions shift towards K-rich calc-alkaline (Blatná suite) and shoshonitic rocks (íany and ertovo bemeno suites) with more evolved isotopic signatures. The distribution of the data is interpreted as reflecting a diversity of sources and processes, rather than a single progressive crustal contamination trend. The Sázava suite could have originated by partial melting of metabasites, or of a mantle source with an isotopic composition close to bulk earth, or by hybridization of crustally-derived tonalitic and mantle-derived magmas. Variation within the Blatná suite is modelled by mixing between a moderately enriched [(⁸⁷Sr/⁸⁶Sr)₃₃₀ 0.708, _Nd ³³⁰ –3] mantle component with either an isotopically evolved metasedimentary component, or with more evolved magmas of the suite. The íany suite was most probably produced by partial melting of peraluminous lithologies, possibly of the adjacent Moldanubian unit. The ertovo bemeno suite evolved from strongly enriched mantle-derived magmas [(⁸⁷Sr/⁸⁶Sr)₃₃₀0.7128, _Nd ³³⁰ –7], either through closed-system fractional crystallization or interaction with magma corresponding to leucogranites of the Central Bohemian Pluton.     

Metamorphism at a late Mesozoic accretionary margin: a study from the Coast Belt of the North American Cordillera

The late Mesozoic and Cenozoic metamorphic evolution of the western North American continental margin is recorded in a belt of homogeneous metapelitic rocks, the Kluane metamorphic assemblage (KMA), in the northern Coast Belt of Yukon Territory. A record of Late Cretaceous medium‐pressure and ‐temperature (c. 7 kbar, 500 °C) metamorphism, M1, is preserved in Ca‐rich garnet and Na‐rich plagioclase cores in rocks that were little affected by later events. M1 was synchronous with mylonitization and is attributed to accretion of the KMA to the ancient continental margin. Isothermal decompression during rapid uplift was followed by early Eocene emplacement of the Ruby Range Batholith (RRB), part of a magmatic arc produced by subduction of the Kula plate. The intrusion of the RRB led to a contact metamorphic overprint, M2, producing a 5–6 km wide aureole in which the grade ranges from subgarnet zone to garnet–cordierite–K‐feldspar zone. Pressure and temperature estimates for M2, calculated from mineral equilibria, are 3.5–4.5 kbar and 530–720 °C, generally consistent with the stability limits of the observed mineral assemblages. Comparison of mineral assemblages and P–T conditions in the KMA with those in the Mclaren Glacier metamorphic belt in Alaska does not support the correlation of the two metamorphic sequences. This weakens the hypothesis proposing 400 km of dextral slip along the Denali fault zone.     

青藏高原东缘晚新生代地质特征与古环境变化

青藏高原东缘地区发育了完整的晚新生代湖相、黄土、红土和冰川沉积系列,不同成因的沉积物记录了晚新生代以来古环境时空变迁的信息。上新世昔格达湖相沉积发育于4.2～2.6MaBP,具有9个冷—暖气候环境变化阶段。川西风尘堆积始于1.15MaBP,连续记录了14个古季风变化旋回,成都平原红土记录了1.13Ma来的5个古环境演化阶段。青藏高原东缘发育了约4.3MaBP的老冰期,第四纪时期出现了5次极端古气候事件,对应为5期冰期。