Effects of the oophagous bivalve Acesta oophaga on the morphology and fecundity of its deep‐sea tubeworm host,Lamellibrachia luymesi

The deep‐sea bivalve Acesta oophaga lives attached to the anterior end of the vestimentiferan tubeworm, Lamellibrachia luymesi, at cold methane seeps. The bivalve is found almost exclusively on female tubeworms, where it consumes the lipid‐rich eggs of L. luymesi that are spawned year round (Biological Bulletin, 209, 2005, 87). It is apparent that A. oophaga benefits directly from this close association, but the consequences for the tubeworm host may be more complicated than just a simple predator–prey interaction. Since A. oophaga completely surrounds the tube opening and plume of the worm, it is likely that its presence would limit oxygen uptake by L. luymesi, thereby inhibiting worm growth and reproduction. We hypothesized that occupied tubeworms would compensate for this by growing larger plumes for oxygen uptake. To explore the effects of bivalve presence/absence on female tubeworms, several morphological features, including body size, plume length, tube diameter, and tube segment length, as well as instantaneous fecundity, were compared. Results suggest that the mere presence of A. oophaga has a significant impact on the morphology of its host worm, as all measures of worm size, except for tube segment length, were significantly greater with clams present. Additionally, instantaneous fecundity was 3.5 times higher in occupied worms, implying that tubeworms are not oxygen‐deprived or energy limited as a result of bivalve presence. Our findings suggest that the association between these two deep‐sea organisms may be a more complex form of symbiosis than the simple predator–prey relationship, as previously thought.     

Size‐frequency distributions of Joania cordata and Argyrotheca cuneata (Brachiopoda: Megathyrididae) from the Central Tyrrhenian Sea

Size‐frequency distributions can support reliable inferences concerning population dynamics of brachiopods, but only a few data are available so far. In this study, length and width frequency distributions of dead specimens of the Recent brachiopods Joania cordata and Argyrotheca cuneata from the Marine Protected Area ‘Secche di Tor Paterno’, Central Tyrrhenian Sea, Italy (41°35′ N, 12°20′ E), are reported in order to add new data about size‐frequency distributions of brachiopods. The studied specimens came from death assemblages in the coralligenous substrate, in the Posidonia oceanica meadows, and in the sand channels. The observed patterns vary from left‐skewed (J. cordata) to right‐skewed (A. cuneata), indicating respectively a low and high mortality of smaller individuals. Significant differences between the coralligenous substrate and the P. oceanica meadow were observed for both species, revealing a variation among different habitats. All length and width distributions are clearly polymodal, but the biological meaning of the peaks is difficult to interpret, as the two species seem to have a 2‐year life span. A biometric analysis of shell sizes revealed that length and width are the most variable parameters during the growth of the animal.     

Cenozoic folding in the Cumuruxatiba basin,Brazil: An approach to the deformation trigger by the Abrolhos magmatism

The Cumuruxatiba basin is located in the central portion of the eastern Brazilian margin surrounded by Cenozoic magmatic highs that belong to the Abrolhos Magmatic Complex. This basin was formed by rifting, in the Neocomian followed by thermal subsidence during late Cretaceous like other basins along the Eastern Brazilian margin. In the Cenozoic, the Abrolhos magmatism took place as sills and dykes intruded the sedimentary section, primarily during the Paleogene. In that time, there was a strong NS contractional deformation in the basin represented by folds related to reverse faults coeval with Abrolhos magmatism activity. The structural restorations of regional 2D seismic sections revealed that most of the contractional deformation was concentrated at the beginning of the Cenozoic with maximum peak at the Eocene (up to 33% of total shortening and rate of 6 km/Ma). The Post-Eocene period was marked by a decrease in the strain rate that continues to the present day (around 4 km/Ma to less than 1). 3D structural modelling exhibited a major, well-developed E–W to NE–SW fold belt that accommodated most of the contractional Cenozoic deformation between Royal Charlotte and Sulphur Minerva magmatic highs. Volcanic eruptions and magmatic flows from the Abrolhos complex resulted in differential overburden on edge of the basin, acting as a trigger for halokinesis and the subsequent formation of fault-related folds. In general, such structures were developed close to adjacent magmatic highs, commonly exhibiting vergence towards the centre of the basin. Some magmatic features formed coeval with Cenozoic syn-deformation sediments clearly indicate that Abrolhos magmatism activity and contractional deformation development were associated. The study of the thickness variation of the syn-deformation section in relation to fault-related folds on deformation maps and maximum strain diagrams revealed that most folds were activated and re-activated several times during the Cenozoic without a systematic kinematic pattern. This lack of systematic deformation might be related to the variation of the magmatic pulse activity of adjacent magmatic highs resulting in a complex interference pattern of Cenozoic folds. These structural interpretations of the timing of fault-related folds that are potential Cenozoic traps in the Cumuruxatiba basin play a fundamental role in petroleum systems and exploration of low-risk hydrocarbon prospects.     

面向对象的连云港海岸带土地利用变化及驱动力分析

以连云港海岸带为研究区,基于1978年和2010年两期Landsat影像,提取土地利用信息,分析土地利用特征及其动态变化过程;面向土地利用变化基本单元,进行土地利用变化驱动力分析。结果表明:研究期初,该地区的主要土地类型为耕地和盐田,共占研究区面积的67.14%;32 a间共有37.17%的土地发生了变化,盐田和耕地面积快速减少,水产养殖区和工矿企业用地快速增加,有限的林地资源在减少,滩涂围垦达面积46.55 km2,土地利用程度加深;变化的土地中,38.95%由经济结构调整驱动,发展潜力大;27.75%由政策驱动,存在诸多的社会和生态问题;20.49%由政策或者经济结构调整与生产力水平共同驱动,取得较好经济和社会效益;12.81%的土地由政策、人口及经济发展共同驱动。连云港海岸带土地利用存在诸多不足之处,也具有巨大的发展空间。本研究对连云港市提高土地利用的社会效益和生态效益具有重要意义。     

Selection of Less Biased Threshold Angles for SAM Classification Using the Real Value–Area Fractal Technique

The accuracy of classification of the Spectral Angle Mapping (SAM) is warranted by choosing the appropriate threshold angles, which are normally defined by the user. Trial‐and‐error and statistical methods are commonly applied to determine threshold angles. In this paper, we discuss a real value–area (RV–A) technique based on the established concentration–area (C–A) fractal model to determine less biased threshold angles for SAM classification of multispectral images. Short wave infrared (SWIR) bands of the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) images were used over and around the Sar Cheshmeh porphyry Cu deposit and Seridune porphyry Cu prospect. Reference spectra from the known hydrothermal alteration zones in each study area were chosen for producing respective rule images. Segmentation of each rule image resulted in a RV–A curve. Hydrothermal alteration mapping based on threshold values of each RV–A curve showed that the first break in each curve is practical for selection of optimum threshold angles. The hydrothermal alteration maps of the study areas were evaluated by field and laboratory studies including X–ray diffraction analysis, spectral analysis, and thin section study of rock samples. The accuracy of the SAM classification was evaluated by using an error matrix. Overall accuracies of 80.62% and 75.45% were acquired in the Sar Cheshmeh and Seridune areas, respectively. We also used different threshold angles obtained by some statistical techniques to evaluate the efficiency of the proposed RV–A technique. Threshold angles provided by statistical techniques could not enhance the hydrothermal alteration zones around the known deposits, as good as threshold angles obtained by the RV–A technique. Since no arbitrary parameter is defined by the user in the application of the RV‐A technique, its application prevents introduction of human bias to the selection of optimum threshold angle for SAM classification.     

Controlling Factors,Accumulation Model and Target Zone Prediction of the Coal‐bed Methane in the Huanghebei Coalfield,North China

The Huanghebei Coalfield, one of the coal production bases in North China, was considered as a coalfield without coal‐bed methane (CBM) during past decades. In recent years, however, CBM has been discovered in coal‐bearing successions. In order to understand the CBM geological characteristics and accumulation process in this area, fifteen coal samples were collected and analyzed with respect to coal maceral and reflectance. The result shows that the gas distribution is uneven and the content varies in different areas even for the same coal bed. The storage of CBM is affected by geological factors such as burial depth, geological structures, and magmatic intrusion, among which the former two are more important in the formation of CBM. Deep burial of coal beds with the presence of cap‐rock mudstone can seal CBM. The CBM is also accumulated and preserved at the place where normal faults are distributed. Magmatic intrusion causes contact metamorphism and controls the CBM formation by heating the coal‐bearing successions. The obtained data indicate the geological conditions in northeastern Zhaoguan Mine are preferable for CBM formation and conservation; recent exploration estimates the CBM geological reserves up to 282.16 Mm³ and average of reserve abundance at 0.1662 × 10⁸ m³ km^?2. The Changqing Mine is a potential prospect in terms of CBM exploration since its geological conditions (structures and burial depth) are similar to the Zhaoguan Mine and its cap rock is even better.     

Calcium,Na, K and Mg Concentrations in Seawater by Inductively Coupled Plasma‐Atomic Emission Spectrometry: Applications to IAPSO Seawater Reference Material,Hydrothermal Fluids and Synthetic Seawater Solutions

We report a measurement procedure to determine simultaneously the major cation concentrations (Na, Ca, K and Mg) of seawater‐derived solutions by inductively coupled plasma‐atomic emission spectrometry. The best results were obtained when the IAPSO (‘standard’) seawater reference material was diluted by thirty times with Milli‐Q^® water. We obtained an average reference value r_K (the ratio of the mass fraction of potassium to that of chlorine, i.e., (g kg^?1)/(g kg^?1)) for IAPSO seawater of 0.0205 ± 0.0006 (2.9% RSD), not significantly different from 0.0206 ± 0.0005 (2.4% RSD) for seawater composition reported in the literature. The measured Na, Ca and Mg concentrations correspond to r_Na, r_Ca and r_Mg values of 0.5406 ± 0.0026 (0.5% RSD), 0.02192 ± 0.00048 (2.2% RSD) and 0.06830 ± 0.00047 (0.7% RSD), respectively, in line with previous values measured by wet‐chemistry and atomic absorption spectrophotometry or wet‐chemical titration. Our measurement procedure was used successfully on synthetic seawater solutions and high‐temperature hydrothermal fluids.     

Sulfur Concentration in Geochemical Reference Materials by Solution Inductively Coupled Plasma‐Mass Spectrometry

With implications for the origin of ore deposits, redox state of the atmosphere, and effects of volcanic outgassing, understanding the sulfur cycle is vital to our investigation of Earth processes. However, the paucity of sulfur concentration measurements in silicate rocks and the lack of well‐calibrated reference materials with concentrations relevant to the rocks of interest have hindered such investigations. To aid in this endeavour, this study details a new method to determine sulfur concentration via high mass resolution solution inductively coupled plasma‐mass spectrometry (ICP‐MS). The method is based on an aqua regia leach, involving relatively rapid sample preparation and analysis, and uses small test portion masses (< 50 mg). We utilised two independently prepared standard solutions to calibrate the analyses, resulting in 4% accuracy, and applied the method to eight geochemical reference materials. Measurements were reproducible to within ~ 10%. Sulfur concentrations and isotopes of six reference materials were measured additionally by elemental analyser‐combustion‐isotope ratio mass spectrometry to independently evaluate the accuracy of the ICP‐MS method. Reference materials that yielded reproducible measurements identical to published values from other laboratories (JGb‐1, JGb‐2 and MAG‐1) are considered useful materials for the measurement of sulfur. Reference materials that varied between studies but were reproducible for a given test portion perhaps suffer from sample heterogeneity and are not recommended as sulfur reference materials.     

Precise and Accurate In Situ Determination of Lead Isotope Ratios in NIST,USGS, MPI‐DING and CGSG Glass Reference Materials using Femtosecond Laser Ablation MC‐ICP‐MS

Lead isotope ratio data were obtained with good precision and accuracy using a 266 nm femtosecond laser ablation (fLA) system connected to a multi‐collector ICP‐MS (MC‐ICP‐MS) and through careful control of analytical procedures. The mass fractionation coefficient induced by 266 nm femtosecond laser ablation was approximately 28% lower than that by 193 nm excimer laser ablation (eLA) with helium carrier gas. The exponential law correction method for Tl normalisation with optimum adjusted Tl ratio was utilised to obtain Pb isotopic data with good precision and accuracy. The Pb isotopic ratios of the glass reference materials NIST SRM 610, 612, 614; USGS BHVO‐2G, BCR‐2G, GSD‐1G, BIR‐1G; and MPI‐DING GOR132‐G, KL2‐G, T1‐G, StHs60/80‐G, ATHO‐G and ML3B‐G were determined using fLA‐MC‐ICP‐MS. The measured Pb isotopic ratios were in good agreement with the reference or published values within 2s measurement uncertainties. We also present the first high‐precision Pb isotopic data for GSE‐1G, GSC‐1G, GSA‐1G and CGSG‐1, CGSG‐2, CGSG‐4 and CGSG‐5 glass reference materials obtained using the femtosecond laser ablation MC‐ICP‐MS analysis technique.     

Mud dispersal across a Cretaceous prodelta: Storm‐generated,wave‐enhanced sediment gravity flows inferred from mudstone microtexture and microfacies

Determining sediment transport direction in ancient mudrocks is difficult. In order to determine both process and direction of mud transport, a portion of a well‐mapped Cretaceous delta system was studied. Oriented samples from outcrop represent prodelta environments from ca 10 to 120 km offshore. Oriented thin sections of mudstone, cut in three planes, allowed bed microstructure and palaeoflow directions to be determined. Clay mineral platelets are packaged in equant, face‐face aggregates 2 to 5 μm in diameter that have a random orientation; these aggregates may have formed through flocculation in fluid mud. Cohesive mud was eroded by storms to make intraclastic aggregates 5 to 20 μm in diameter. Mudstone beds are millimetre‐scale, and four microfacies are recognized: Well‐sorted siltstone forms millimetre‐scale combined‐flow ripples overlying scoured surfaces; deposition was from turbulent combined flow. Silt‐streaked claystone comprises parallel, sub‐millimetre laminae of siliceous silt and clay aggregates sorted by shear in the boundary layer beneath a wave‐supported gravity flow of fluid mud. Silty claystone comprises fine siliceous silt grains floating in a matrix of clay and was deposited by vertical settling as fluid mud gelled under minimal current shear. Homogeneous clay‐rich mudstone has little silt and may represent late‐stage settling of fluid mud, or settling from wave‐dissipated fluid mud. It is difficult or impossible to correlate millimetre‐scale beds between thin sections from the same sample, spaced only ca 20 mm apart, due to lateral facies change and localized scour and fill. Combined‐flow ripples in siltstone show strong preferred migration directly down the regional prodelta slope, estimated at ca 1 : 1000. Ripple migration was effected by drag exerted by an overlying layer of downslope‐flowing, wave‐supported fluid mud. In the upper part of the studied section, centimetre‐scale interbeds of very fine to fine‐grained sandstone show wave ripple crests trending shore normal, whereas combined‐flow ripples migrated obliquely alongshore and offshore. Storm winds blowing from the north‐east drove shore‐oblique geostrophic sand transport whereas simultaneously, wave‐supported flows of fluid mud travelled downslope under the influence of gravity. Effective wave base for sand, estimated at ca 40 m, intersected the prodelta surface ca 80 km offshore whereas wave base for mud was at ca 70 m and lay ca 120 km offshore. Small‐scale bioturbation of mud beds co‐occurs with interbedded sandstone but stratigraphically lower, sand‐free mudstone has few or no signs of benthic fauna. It is likely that a combination of soupground substrate, frequent storm emplacement of fluid mud, low nutrient availability and possibly reduced bottom‐water oxygen content collectively inhibited benthic fauna in the distal prodelta.