NW Region Research Articles

Zooplankton diel vertical migration and contribution to deep active carbon flux in the NW Mediterranean

The diel vertical migration (DVM) of zooplankton contributes to the biological pump transporting material from surface to deep waters. We examined the DVM of the zooplankton community in different size fractions (53–200μm, 200–500μm, 500–1000μm, 1000–2000μm and >2000μm) during three cruises carried out in the open NW Mediterranean Sea. We assessed their metabolic rates from empirical published relationships and estimated the active fluxes of dissolved carbon to the mesopelagic zone driven by migrant zooplankton. Within the predominantly oligotrophic Mediterranean Sea, the NW region is one of the most productive ones, with a seasonal cycle characterized by a prominent spring bloom. The study area was visited at three different phases of the seasonal cycle: during the spring bloom, the post-bloom, and strongly stratified oligotrophic conditions. We found seasonal differences in DVM, less evident during the bloom. Changes in DVM intensity were related to the composition of the zooplanktonic assemblage, which also varied between cruises. Euphausiids appeared as the most active migrants in all seasons, and their life cycle conditioned the observed pattern. Immature stages, which are unable to perform large diel vertical movements, dominated during the bloom, in contrast to the higher relative importance of migrating adults in the other two sampling periods. The amount of dissolved carbon exported was determined by the migrant zooplankton biomass, being highest during the post-bloom (2.2mmol C respiredm−2d−1, and up to 3.1mmol C exportedm−2d−1 when DOC release estimations are added). The active transport by diel migrants represented a substantial contribution to total carbon export to deep waters, especially under stratified oligotrophic conditions, revealing the importance of zooplankton in the biological pump operating in the study area.

Spatiotemporal relationship between temperature and precipitation in inland China from meteorological data and paleoclimatic implications for lacustrine oxygen records

The factors controlling climate in China's western interior are numerous and quite complex. These vary on seasonal to multi-millennial time scales as a result of changing dominance of influence from the Westerlies and the Asian and Indian Monsoon systems. These in turn respond to additional factors such as the dynamics of the Walker and Hadley circulation in the Pacific and Indian Ocean basins, the strength of the Siberian and Northwest Pacific Highs, and on long timescales to changes in the distribution of solar insolation resulting from orbital forcing. Here, we use the Empirical Orthogonal Function (EOF) analysis to investigate the spatiotemporal patterns of climate in China's western interior during the last 15 ka as revealed from a suite of 17 lacustrine carbonate δ18O records. Based on similarities to the EOF analysis of the modern data, we interpret the first two leading eigenmodes of the paleodata sets as P and T, respectively. Other climatic proxy data from this region appear to agree well with this interpretation. Our analysis reveals a discrete change in the spatial EOF patterns occurring at circa 7.5–6 ka BP with respect to the patterns observed prior to this. These patterns suggest that the arid NW region of the study area became significantly wetter following this juncture, but that the Asian Monsoon influenced (SE) region of the study area along the eastern flank of the Tibetan Plateau became drier. A more complex pattern of change is revealed by the second rank EOF, interpreted as temperature. This shows a discrete change at ∼7.5–6 ka BP from cooler to hotter temperatures on the central Tibetan Plateau, but slightly cooler temperatures in the lowland Monsoon affected area (SE) after 6 ka BP. We interpret both these sets of changes to result from more persistent high pressure over the Tibetan Plateau during Boreal summer, with a resultant enhancement of moisture transport by the westerlies and diminished monsoonal flow following ∼6 ka BP.

Radial Epitaxy of Silicon for Optoelectronic Applications

At the heart of the dramatic transition in semiconductor device technology from planar to three-dimensional (3D) architectures is the ability to shrink devices to nanoscale dimensions with near atomic level control of materials’ structure and composition. The 3D structures serve as building blocks for high-performance electronic and photonic devices such as photovoltaic cells, light-emitting diodes, multi-gate field effect transistors and require unprecedented control in dimensions and materials properties. Epitaxial crystal growth, along with lithographic and etching technologies, provides one of the enabling approaches to create such structures. The standard for epitaxy in electronics technology is chemical vapor deposition (CVD) growth, which enables preparation of 3D semiconducting nanomaterials with modulated composition and electrical dopant profiles, with silicon (Si) epitaxy being arguably the world’s best studied crystal growth system. It is thus important to understand Si epitaxy on nanoscale structures, since any change in crystal growth kinetics at small sizes would have a large effect on dimensional control from a technological perspective and would also be of great interest from a fundamental perspective for understanding atomic scale processes and fabricating novel structures. We show that Si epitaxial growth at the nanoscale becomes size dependent at dimensions significantly larger than the onset of thermodynamic limits, and that this previously unknown behavior within the mesoscopic size regime for one of the best known crystal growth systems is a general phenomenon. A monotonic reduction in homoepitaxial growth rate with size is observed for facet widths below certain scale and the results modeled by an area-dependent precursor incorporation rate. The presence of n and p type dopants results in even greater reductions in low temperature radial growth rates, and a critical thicknesses for Si single crystal radial epitaxy is found for phosphorus. The results provide new insights on the nature of CVD crystal growth at small dimensions and have significant implications for 3D nanoscale fabrication of technologically important Si electronic device architectures. Si radial p-i-n junction nanowire structure is a suitable platform to integrate fundamental understanding and applications since the structure provides an approach for realizing concurrent maximization of light absorption and photogenerated carrier separation in photovoltaic (PV) devices. Additionally, NW arrays embedding radial p-(i)-n junctions enhance light absorption significantly in wide range of wavelengths. Si radial p-i-n junctions consisted of core Si NWs and Si shells. Core Si NWs were prepared by top-down consisting of lithographic technique and deep reactive ion etching. After formation of Si NWs, the color of Si substrate in NW regions turned to be black from shiny metallic surface. The change of color indicates enhanced light absorption in visible wavelengths. Electrically doped Si radial shell was prepared by epitaxial growth on the surfaces of Si NWs via low-pressure chemical vapor deposition. PV characteristics of crystalline Si radial p-i-n junction arrays prepared by top-down approach and epitaxial shell growth were investigated by current–voltage measurements under dark and Air Mass 1.5G conditions. Though the unoptimal dimensions of NWs and top electrode configuration, the open circuit voltage, short circuit current density, and photoconversion efficiency of the device were 0.46 V, 40 mA/cm2, and 10%, respectively. The high short circuit current density comparable to that of commercialized Si PV cell indicates that efficient photogenerated generation/collection is occurred in Si radial p-i-n junction.

Tracking the expansion of the American mink (Neovison vison) range in NW Portugal

Invasive in many European countries, the American mink (Neovison vison) was introduced in Portugal in the late 1980’s, presumably escaping from Spanish fur farms close to the border. In spite of the biological richness of the invaded area, no study ever addressed the evolution of the invasion process. We aimed to investigate the current distribution and status of the mink in NW Portugal and discuss some contributing factors to explain the rate of invasion. We detected mink presence using floating rafts as footprint tracking devices, and scats as a molecular tool aiding in species identification. Results demonstrate a clear range expansion southwards, with mink already occupying most of the region’s hydrographic basins. After a first phase of slow expansion (55 km in 20 years), mink seems to have expanded its range quite rapidly in only 2 years (45 km). The initial delay could be due to local thriving otter populations, whereas the recent establishment of red swamp crayfish (Procambarus clarkii) in the area could be a plausible explanation for the acceleration in the mink’s expansion. Being a key food resource, crayfish may be playing an important role as an expansion facilitator. Mink eradication is probably no longer feasible since well established populations near the border continue to function as sources for the Portuguese population. Therefore, a control program should start immediately in the NW region, preferably in conjunction with Spanish authorities.

Stable isotopic compositions of precipitation in China

During the mid-1980s, there were 31 stations in China that successfully participated in the Global Network of Isotopes in Precipitation. However, most observations were suspended after the mid-1990s. The discontinuous data hindered the application of precipitation isotopes, which are strongly affected in China by the Asian monsoon and are thus of intrinsic interest for palaeoclimatologists. Therefore, to continuously observe precipitation isotopes nationwide, the Chinese Network of Isotopes in Precipitation was established in 2004. The current study reviewed the major characteristics of the 928 samples that were collected from 2005 to 2010. The ranges of δD and δ18O values generally followed the pattern NE>NW>TP>NC>SC, and the amount-weighted δ-values followed the pattern SC>NW>NC>TP>NE. Temporal variations presented a ‘V’-shaped pattern at the SC region and reverse ‘V’-shaped patterns at the NE and NW regions. Decreasing trends with the advent of the rainy season were found at the NC and TP regions. The Chinese Meteoric Water Line has been established as δD=7.48δ18O+1.01. The distributions of scattering along the line demonstrated different water vapour origins and characteristics. The values of δ18O showed strong temperature dependence at the NE (0.27‰/°C) and NW stations (0.37‰/°C), and this dependent variable switched to water vapour pressure and vapour pressure at the SC stations. The geographical controls of δ18O were −0.22‰/° and −0.13‰/100 m for latitude and altitude, respectively. The δ18O/Latitude gradient increased from south to north at the Eastern Monsoon Region, and the δ18O/Altitude gradient (−0.30‰/100 m) was especially significant for the TP region. The results of this study could provide basic isotopic information for on-going investigations in hydrology, meteorology, palaeoclimatology and ecology at different regions of China.

Large wildland fires in three diverse regions in Spain from 1978 to 2010.

Aim of study: Large wildland fires (LWF) are major disturbance processes affecting many ecosystems each year. In last decades, socio-economic changes have contributed to major changes in land uses. This study assess trends in number, burned area and average size of large wildfires (> 100 ha) from 1978 to 2010 in Spain.Area of study: This work analyzes three clearly different regions of Spain (Mediterranean coast, MC, Mediterranean Interior, MI, Northwestern Spain, NW).Material and Methods: We studied historical wildland fire data from Spain’s EGIF database (General Statistics on Wildland Fires). We selected only wildland fires larger than 100 ha. All LWF were analyzed to test trends in number of fires, burned area and mean fire size.Main results: The number of LWF decreased in all regions but the burned area only decreased in MC and NW regions. However, both the number of LWF and the burned area did not decrease after 1995 in any region. The average size of LWF did not change in any of the three regions. Fires larger than 500 ha were very significant due to the high percentage of area burned in relation to the total area burned by fires larger than 100 ha (79.3 % in MC, 63.9 % in MI, and 35.7% in NW).Research highlights: After 1995, the number of LWF and burned area did not decrease. Additional actions are required including learned lessons from past LWF spread, and better trained fire suppression workers and more fuel management.Keywords: large wildland fires; trends; forest management; Spain.

A multiple dating-method approach applied to the Sanabria Lake moraine complex (NW Iberian Peninsula, SW Europe)

New evidence in the NW region of the Iberian Peninsula (∼42°N 6°W) of a glacial advance coeval with the global Last Glacial Maximum (LGM) of the Marine Isotope Stage 2 has been identified through a dataset of exposure ages based on 23 10Be concentration measurements carried out on boulder samples taken from a set of latero-frontal moraines. Results span the interval 19.2–15.4 10Be ka, matching the last deglaciation period when Iberia experienced the coldest and driest conditions of the last 25 ka, and are consistent with Lateglacial chronologies established in other mountain regions from SW Europe. The extent of the LGM stade identified in this work is similar to the local maximum ice extent stade recorded and dated as prior to 33 ka using radiocarbon and optically stimulated luminescence. This work showcases how multiple-dating approaches and detailed geomorphological mapping are required to reconstruct realistic palaeoglacier evolution models.

Intercomparison of the Charnock and COARE bulk wind stress formulations for coastal ocean modelling

Abstract. The accurate parameterisation of momentum and heat transfer across the air–sea interface is vital for realistic simulation of the atmosphere–ocean system. In most modelling applications accurate representation of the wind stress is required to numerically reproduce surge, coastal ocean circulation, surface waves, turbulence and mixing. Different formulations can be implemented and impact the accuracy of the instantaneous and long-term residual circulation, the surface mixed layer, and the generation of wave-surge conditions. This, in turn, affects predictions of storm impact, sediment pathways, and coastal resilience to climate change. The specific numerical formulation needs careful selection to ensure the accuracy of the simulation. Two wind stress parameterisations widely used in the ocean circulation and the storm surge communities respectively are studied with focus on an application to the NW region of the UK. Model–observation validation is performed at two nearshore and one estuarine ADCP (acoustic Doppler current profiler) stations in Liverpool Bay, a hypertidal region of freshwater influence (ROFI) with vast intertidal areas. The period of study covers both calm and extreme conditions to test the robustness of the 10 m wind stress component of the Coupled Ocean–Atmosphere Response Experiment (COARE) bulk formulae and the standard Charnock relation. In this coastal application a realistic barotropic–baroclinic simulation of the circulation and surge elevation is set-up, demonstrating greater accuracy occurs when using the Charnock relation, with a constant Charnock coefficient of 0.0185, for surface wind stress during this one month period.

The lightning activity associated with the dry and moist convections in the Himalayan Regions

AbstractLightning activity in the dry environment of northwest India and Pakistan (NW) and in the moist environment of northeast India (NE) has been examined from the Optical Transient Detector and Lightning Imaging Sensor data obtained from the Tropical Rainfall Measuring Mission satellite during 1995–2010. In the NW region, seasonal variation of flash rate is annual with a maximum in July but is semi‐annual with a primary maximum in April and a secondary maximum in September, in the NE region. On diurnal scale, flash rate is the maximum in the afternoons, in both the NE and NW regions. The correlation of flash rate with convective parameters, viz. surface temperature, convective available potential energy (CAPE) and outgoing long‐wave radiation is better with convective activity in the NW than in the NE region. Mean value of aerosol optical depth at 550 nm is ~ 26% higher and is highly correlated with flash rate in NW as compared to that in NE. Results indicate that CAPE is ~ 120 times more efficient in NW than in the NE region for production of lightning. The empirical orthogonal function analysis of flash rate, surface temperature, and CAPE shows that variance of lightning activity in these regions cannot be fully explained by the variance in the surface temperature and CAPE alone, and that some other factors, such as orographic lifting, precipitation, topography, etc., may also contribute to this variance in these mountainous regions. Further, the increase in CAPE due to orographic lifting in the Himalayan foothills in the NE region may contribute to ~ 7.5% increase in lightning activity. Relative roles of the thermally induced and moisture‐induced changes in CAPE are examined in these regions. This study merely raises the questions, and that additional research is required for explaining the fundamental reasons for the reported observations here.

PTU-105 Outcome of Cirrhotic Patients Admitted to Intensive Care Units at Hospitals without Specialist Liver Services

IntroductionPatients with liver cirrhosis admitted to an ICU are believed to have a poor prognosis with high mortality despite significant use of resources. Most of the literature to date on...

Comparison of 1-min rain rate derived from TRMM satellite data and raingauge data for microwave applications in Nigeria

A comparative statistical study of derived 1-min rain rate using data obtained from Tropical Rainfall Measuring Mission (TRMM) satellite (3A12 V6 and 3B43V6) and raingauge measurements are presented. 30-years data of rainfall intensities obtained from the Nigerian Meteorological Agency rain-gauge network and 9-years rainfall data obtained from TRMM satellite are used. Cumulative distributions of rain rate were obtained using a combination of an improved version of the Moupfouma–Martin model for rain rate prediction in the tropical regions. Variations of rain rate of different integration time are compared for 28 stations across Nigeria. The Kriging interpolation method was used for spatial interpolation of rain accumulation values into a regular grid in order to obtain a highly consistent and predictable inter-gauge rainfall variation. Noticeable differences between rain rate estimated from rain-gauge and TRMM data were found to be a function of period and location. From quantitative comparison over each of the region, there are reasonably positive correlations between the two sets of data for different percentages of time with correlation coefficient varying from 0.84 to 0.99 at 99.99% availability of time. Comparison with ITU-R 837-5 shows that, ITU model underestimates rain rate as high as 51% from the mean value depending on the percentages of at which time rain rate is exceeded. The overall result shows that the gauge data perform better than TRMM data in most of the sites located in the SW, SE, SS, MB and NE regions, while TRMM data provided better results for sites in the NW region from the statistical perspective with the lower RMS values.

Su1711 Outcome of Cirrhotic Patients Admitted to Intensive Care Units At Hospitals Without Specialist Liver Services

Introduction Patients with liver cirrhosis admitted to an ICU are believed to have a poor prognosis with high mortality despite significant use of resources. Most of the literature to date on this topic has been collected at hospitals with Specialist Liver Units and these results may not be representative of the outcome at general ICUs. A recent prospective study of cirrhotic patients admitted to a tertiary Liver ICU in the UK demonstrated an overall hospital mortality of 59%. The aim of this study was to determine the outcome of cirrhotic patients admitted to non-specialist ICUs. Methods Data was retrospectively collected from four hospitals in the NW region of the UK without specialist liver ICUs. Patients were identified using the Intensive Care National Audit and Research Unit (ICNARC) database. 61 patients with liver cirrhosis admitted to a general ICU between January 2010 and January 2012 were included in this study. Results Age range was 30 to 79 years (average 51 years). 80% of patients were male and alcohol was the commonest aetiology for liver cirrhosis (90%). The main reason for admission to ICU was for gastrointestinal bleeding (38%). 51% of patients had a Child Pugh score of C on admission to ICU. 46% of patients had a MELD score between 10 and 19 and 28% had a score between 20 and 29. 79% of patients required invasive ventilatory support, 49% required vasopressors and 21% needed renal replacement therapy. 51% developed further decompensation of their liver disease during their ICU stay. These included GI bleeding (21%), hepatic encephalopathy (15%), HRS (11%) and SBP (3%). 67% of patients had an ICU stay of Conclusion Patients with liver cirrhosis admitted to general ICUs have similar rates of mortality compared to those in tertiary liver ICUs. Therefore, admission to such units should not be deemed futile in cirrhotic patients and earlier admission may improve outcome. Disclosure of Interest None Declared

N010 Coming out about IBD: transferable skills from the gay, lesbian, bisexual and transgender (GLBT) population in the UK

Conclusions: This study confirms the knowledge of IBD patients is poor and is not just representative of one hospital trust. It also confirms that patients do not recognise their deficit in their knowledge. This study echos previous recommendations that IBD teams need to do more to actively educate their patients. We are currently planning a rolling 12 month IBD patient educational programme in the NW region to investigate the possible benefits to IBD patients.

GPR investigations at an Inca‐Spanish site in Argentina

ABSTRACTWe present the results of a GPR prospecting carried out at the archaeological site of Batungasta, in the NW region of Argentina. This site was established by the Incas in the 14th century and was later occupied during the Spaniard conquest. Environmental information obtained at this arid zone led us to postulate that parts of the site buildings had been seriously damaged and buried by seasonal flood events as well as aeolian sedimentation. Therefore, we considered applying the GPR method to investigate the existence of buried remains, their architectural characteristics and to provide further evidence about the flows that possibly affected them. This method seemed suitable to attain these goals since it usually provides a good detection capacity for architectural structures and layers in dry environments, as well as good quality maps of the soil. Seven sectors of the site were surveyed using a GPR constant‐offset methodology and 500 MHz antennas. The analysis of the data allowed recognizing electromagnetic patterns that could be associated to the existence of walls. In six of the seven sectors, enclosures formed by rock‐earth and earth walls were detected and mapped, confirming Incaic‐Spanish and Spanish structures, respectively. A sedimentary layer produced by a large flood that covered the structures was detected and mapped, providing evidence of this kind of event and its influence on the site. The maps of this layer were also useful to indirectly visualize the 3D shapes of the discovered walls, which were unclear in many sections of the data and to detect additional anthropogenic structures with very bad preservation conditions. These structures had not been previously identified from analysis of the data sections due to the confusing aspect of the reflections produced at their irregular boundaries.

Multivariate statistical analysis of deformation tensors: independent vs. correlated tensor observations

In the presence of errors in measuring a random displacement field (under the normal distribution assumption of displacement field), stochastic behaviors of principal components of deformation tensors (strain tensor and tensor of change of curvature (TCC)), based on the intrinsic assumption of geometrical modeling of surface deformation analysis, are discussed. We divided the contents into two parts: In the first, we considered independent random vectors of repeated tensor measurements. In the second step, we considered correlations among repeated measurements. Then, covariance components between tensor elements by Helmert estimator, based on prior information of variance components, are estimated. As a case study, both assumptions are applied to the estimation of principal components of deformation rate tensor observations in Zagros region (Western Iran). The results of numerical analysis showed that greatest shortening is accommodated in oblique orientation (NS) with respect to the Main Recent Fault (MRF), northwest part of North Zagros, Central Iran block and MRF, respectively. Most of the extensions occurred in the east part of the belt. The pattern of eigenspace components of TCC shows highest positive values across the NW region, nearly in orthogonal direction to the MRF and Main Zagros Fault (MZF). The pattern has insignificant values in the Central Zagros. It takes the significant negative values across the SW part, especially along the SPF and Persian Gulf shore. The effect of non-independent observations on the estimation of eigenspace components of deformation tensors (strain tensor and TCC) shows that the estimation of covariance components has influence on the confidence intervals of eigenspace components, especially in seismically active regions of the belt (along the Persian Gulf shore, NW of the belt and region between the Central Iran block and MRF). The results demonstrate the importance of considering the correlation structure among the observations on statistical behavior of principal components of deformation tensors in seismically active regions.

Aquifer Vulnerability Assessment and Wellhead Protection Areas to Prevent Groundwater Contamination in Agricultural Areas: An Integrated Approach

To implement successful policies for the protection of groundwater and curtail the possibility of water supply contamination, an early evaluation of aquifer vulnerability is needed. Rather than implementing broad restrictions to land use and effluent discharge, it is more cost-effective and economically favourable to approach protection in a stepwise manner by first assessing the intrinsic vulnerability of the aquifer when defining the level of land use control that is needed to protect groundwater quality. Following aquifer vulnerability evaluation, specific land uses and restrictions should be defined locally for each water supply within the wellhead protection areas (WHPAs), which are identified by means of the groundwater time of travel (TOT). The WHPA should be established for each individual situation, considering the level of vulnerability of the exploited aquifer. We applied our findings to a specific test site in the Piemonte region of NW Italy, following the current local procedure for individuating the WHPAs. Using data gathered from this site-specific exercise, we identified that the procedure allows methods that consider only aquifer parameters to evaluate vulnerability and discourages the use of techniques that already compartmentalize soil parameters in the vulnerability assessment.

Contribution of the resistivity method to characterize mud walls in a very dry region and comparison with GPR

Mud walls are frequent in many archaeological sites, including sites located in semi-desert regions. In cases with buried walls, the geophysical methods can be useful tools for their investigation, since they provide maps of the subsoil in a non-invasive way and in relatively short times. This article deals with the characterization of mud walls in very dry soils through the resistivity method, discussing a methodology to satisfactorily apply the method in this kind of adverse environment and how to interpret the results. The case of the Palo Blanco archaeological site, a pre-Incaic village located in the NW region of Argentina, is analyzed. In very dry soils, it is frequent that the electrical current cannot be injected due to the high values of electrical resistivity at the shallowest portions of soil, which makes the resistivity method useless. Here we show how this problem can be systematically overcome by wetting a shallow thread between each pair of injection electrodes, and the manner in which the resulting profiles can be analyzed. We perform numerical simulations of the resistivity profiles considering 3D models of mud walls and wetted threads that reproduce experimental situations, and compare them to 2D field data. The resistivity profiles are analyzed for different orientations and distances between the wall and profile, and fluctuations of the soil parameters. The experimental profiles are interpreted from these simulations and compared to ground penetrating radar (GPR) profiles. The resistivity methodology shows effective for characterizing the size and depth of the mud walls, even in cases with collapsed or much eroded walls, for which GPR often fails.

Systematic documentation of landslide events in Limbe area (Mt Cameroon Volcano, SW Cameroon): geometry, controlling, and triggering factors

Limbe town and surrounding areas, on the SE foot slopes of the active Mt Cameroon Volcano, have experienced numerous small-scale shallow landslides within the last 20 years. These resulted in the loss of *30 lives and significant damage to farmland and properties. Landslides and their scars are identified in the field, and their geometry systematically measured to construct a landslide inventory map for the study area. Specific landslides are investigated in detail to identify site-specific controlling and triggering factors. This is to constrain key input parameters and their variability for subsequent susceptibility and risk modeling, for immediate local and regional applications in land-use planning. It will also enable a rapid exploration of remediation strategies that are currently lacking in the SW and NW regions of Cameroon. Typical slides within the study area are small-scale, shallow, translational earth, and debris slides though some rotational earth slides were also documented. The depletion zones have mean widths of 22 m ± 16.7 m and lengths of 25 ± 23 standard deviation. Estimated aerial extents of landslide scars and volume of generated debris range from 10 1 to 10 4 m 2 and 2 to 5 9 10 4 m 3 , respectively. A key finding is that most slope instabilities within the study area are associated with and appear to be exacerbated by man-made factors such as excavation, anarchical construction, and deforestation of steep slopes. High intensity rainfall notably during localized storms is the principal triggering factor identified so far. The findings from this case study have relevance to understanding some key aspects of locally devastating slope instabilities that commonly occur on intensely weathered steep terrains across subtropical Africa and in the subtropics worldwide and affecting an ever denser and most vulnerable population.

Geochemical, zircon U–Pb dating and Sr–Nd–Hf isotopic constraints on the age and petrogenesis of an Early Cretaceous volcanic-intrusive complex at Xiangshan, Southeast China

The Late Mesozoic geology of Southeast China is characterized by extensive Jurassic to Cretaceous magmatism consisting predominantly of granites and rhyolites and subordinate mafic rocks, forming a belt of volcanic-intrusive complexes. The Xiangshan volcanic-intrusive complex is located in the NW region of the belt and mainly contains the following lithologies: rhyodacite and rhyodacitic porphyry, porphyritic lava, granite porphyry with mafic microgranular enclaves, quartz monzonitic porphyry, and lamprophyre dyke. Major and trace-element compositions, zircon U–Pb dating, and Sr–Nd–Hf isotopic compositions have been investigated for these rocks. The precise SHRIMP and LA–ICP–MS zircon U–Pb dating shows that the emplacement of various magmatic units at Xiangshan took place within a short time period of less than 2 Myrs. The stratigraphically oldest rhyodacite yielded a zircon U–Pb age of 135 ± 1 Ma and the overlying rhyodacitic porphyry has an age of 135 ± 1 Ma. Three porphyritic lava samples yielded zircon U–Pb ages of 136 ± 1 Ma, 132 ± 1 Ma, and 135 ± 1 Ma, respectively. Two subvolcanic rocks (granite porphyry) yielded zircon U–Pb ages of 137 ± 1 Ma and 137 ± 1 Ma. A quartz monzonitic porphyry dyke, which represented the final stage of magmatism at Xiangshan, also yielded a zircon U–Pb age of 136 ± 1 Ma. All these newly obtained precise U–Pb ages demonstrate that the entire magmatic activity at Xiangshan was rapid and possibly took place at the peak of extensional tectonics in SE China. The geochemical data indicate that all these samples from the volcanic-intrusive complex have an A-type affinity. Sr–Nd–Hf isotopic data suggest that the Xiangshan volcanic-intrusive complex derived mainly from remelting of Paleo-Mesoproterozoic crust without significant additions of mantle-derived magma. However, the quartz monzonitic porphyry, which has zircon Hf model ages older than the whole-rock Nd model ages, and which has eNd(T) value higher than the other rocks, may indicate involvement of a subordinate younger mantle-derived magma in its origin. Geochemical data indicate that the various rocks show variable REE patterns and negative anomalies of Ba, Nb, Sr, P, Eu and Ti in the trace element spidergrams, suggesting that these rocks may have undergone advanced fractional crystallization with separation of plagioclase, K-feldspar and accessory minerals such as allanite. We suggest that this Cretaceous volcanic-intrusive complex formed in an extensional environment, and the formation of the Xiangshan mafic microgranular enclaves can be explained by the injection of mafic magma from a deeper seated mantle magma chamber into a hypabyssal felsic magma chamber at the crustal emplacement levels.

Decrypting Cryptic Species: Morphological and Molecular Evidence for Recognizing <I>Navarretia linearifolia</I> as Distinct from <I>N. sinistra</I> (Polemoniaceae)

Abstract The unified species concept and a criterion of limited homogenizing gene flow as evidenced by genetic and morphological markers were applied to species delimitation within Navarretia sinistra. Concordant patterns of variation diagnose two morphologically cryptic species. As a consequence, the basionym Gilia linearifolia is here lectotypified and re-established for this long neglected epithet. Navarretia linearifolia shows strong differentiation from N. sinistra in allozyme data and DNA sequences from chloroplast regions, nrDNA, and introns of the low copy nuclear genes idhA, idhB, and g3pdh. In macroscopic features, N. linearifolia differs from N. sinistra primarily in tendencies, rather than absolute differences. Two finer-scale features are diagnostic: pollen sexine sculpturing and mature seed color. The combination Navarretia linearifolia subsp. pinnatisecta is made for the large flowered populations of this species geographically restricted to the NW region of the California floristic provinc...