Uppermost Samples Research Articles

Tectonic evolution of the eastern margin of the Southern Patagonian Andes fold-thrust belt: U-Pb detrital zircon geochronology and kinematic-structural modelling

We present a multidisciplinary study in the Austral-Magallanes basin combining U-Pb geochronology and provenance analysis with structural modelling to unravel the evolution of the fold-thrust belt and related foreland basin sedimentation. Our approach is innovative for the studied area, where the foreland stratigraphic record comprises a stack of marine deposits exceeding 5000 m in thickness. Using zircon U-Pb geochronology from 13 samples distributed through the foreland deposits in the Southern Patagonian Andes at 51°20′S latitude, we calculated maximum depositional ages and analyzed regional variations in provenance. The older sample, with an age of 96.0 ± 1.5 Ma, corresponds to the first sandstone beds of the Punta Barrosa Formation, whereas the uppermost sample, with an age of 17.9 ± 0.4 Ma stems from the Santa Cruz Formation. Furthermore, the presented data help to complete the geochronological information existing for the South Patagonian Andes, by informing the regional geodynamic framework and timing variations. Linking new and previously published data regarding detrital zircon provenance, maximum depositional ages analysis, thermochronology and stratigraphic data with a balanced structural cross section, we propose a step-by-step model combining the kinematic evolution of the fold-thrust belt orogenic front with the basin history. A wedge-top setting for the Late Cretaceous is recognized, as well as two minor uplift events by Eocene time, followed by a major Miocene tectonic exhumation event.

Response of Larix chinensis Radial Growth to Climatic Factors Using the Process-Based Vaganov–Shashkin-Lite Model at Mt. Taibai, China

The Qinling Mountains are located on the dividing line between the north and the south of China. Mt. Taibai, the study site, is the highest peak in the Qinling Mountains and also the highest peak in eastern mainland China. At Mt. Taibai, several dendroecological studies have been conducted on the relationship between tree-ring indices and climatic factors using traditional statistical methods. In this study, the response of Larix chinensis Beissn radial growth to climatic factors was explored in the treeline area of Mt. Taibai using the process-based Vaganov–Shashkin-Lite (VSL) model for the first time. The conclusions were obtained according to the analysis of the L. chinensis tree-ring samples collected from both the northern and southern slopes of Mt. Taibai. The VSL model showed that temperature limits L. chinensis growth during the entire growing season, while the model did not indicate precipitation as a limiting factor. The model showed significant positive correlations between the simulated and observed tree-ring chronologies for 1959–2013, excluding the uppermost sample site on the northern slope. However, the model performance deteriorated with increasing altitude, which may be due to the decreased sensitivity of radial growth to climatic factors above the treeline.

Increased juvenile native fish abundance following a major flood in an Arizona river

Spring floods trigger spawning in many native fishes of the desert Southwest (USA), but less is known about fish community response when native fishes are rare. Here, we document change to native and nonnative fish captures and instream habitat features following a decade-high flooding event (2019) in the Verde River (AZ) where native fish captures were rare in the years pre-flood. Using prepositioned areal electrofishing devices (PAEDs), we sampled the fish community at 90 sampling units pre-flood (2017) and resampled those same units post-flood (2019) to compare and identify changes to catch and habitat features. Relative abundance of native fishes increased from 0.6% pre-flood (0.01 fish/PAED) to 53.0% post-flood (1.66 fish/PAED) and was largely attributable to the presence of juvenile Roundtail Chub Gila robusta (≤ 70 mm total length (TL)) and juvenile Sonora Sucker Catostomus insignis (≤ 100 mm TL). Juvenile Desert Sucker Catostomus clarkii experienced a lesser increase. One adult native fish was captured in 2017 and adult native fishes were absent from 2019 sampling. The catch of adult/subadult Common Carp Cyprinus carpio (> 100 mm TL) declined; however, this could be related to reservoir management and not the flood. The abundance of all size-classes of Black Bass Micropterus spp., Red Shiner Cyprinella lutrensis and other nonnative fishes did not change. The majority (97%) of juvenile native fishes were captured at the uppermost sampling reach. A 54% reduction to canopy cover across all sampling reaches and an increase of fine sediments at the most downstream reach demonstrates how floods can restructure the river environment. This case-study adds evidence that protection of spring floods is vital to the persistence and recolonization of fishes native to the desert Southwest, especially where they are rare. The continued presence of nonnative species may preclude juvenile native fishes from recruiting to adults.

Nephrolepidina and unispiralled Miogypsinidae from the Oligo-Miocene toe-of-slope succession of Gran Sasso (L'Aquila, Central Apennines - Italy): biometric and evolutionary remarks

A biometric analysis was performed on twelve Nephrolepidina and ten Miogypsina and Miogypsinoides populations, coming from the Tre Valloni section, an Oligo-Miocene calcarenitic toe-of-slope succession outcropping in the southern sector of Gran Sasso (L'Aquila, Central Apennines - Italy). Miogypsina populations are investigated applying two essential parameters, i.e., the number of the nepionic chambers and the protoconch diameter. Previously detected evidences of reworking in the same material suggested to use some cautions to avoid misleading results. A mixed typological-statistical methodology is used, leading from starting "disordered" assemblages to final "virtual but reliable" populations, cleaned up from reworked specimens, in order to implement the accuracy of the biostratigraphic results. This goal is reached for the lower part of the succession only. According to the biometric limits proposed for the various chronospecies in the recent literature, the resulting populations are referred to Miogypsinoides ex. interc. complanatus-formosensis up to Md. bantamensis, and to Miogypsina basraensis up to M. ex. interc. gunteri-tani. This sequence of taxa, in general, is in agreement with the principle of nepionic acceleration, with a progressive reduction in the average number of nepionic chambers (X), arranged in a single spiral, just peculiar in the more primitive populations. Miogypsinoides bantamensis and Miogypsina basraensis are recognized biometrically for the first time in the Central Apennines. Nephrolepidina populations are investigated applying the recently introduced biometry of the fifth stage of the neanic equatorial chamberlets, supplying additional data about parameters and factors that had already demonstrated to have taxonomic-biostratigraphic significance. The biometric analysis of the embryo-nepionic stages was performed as an integration of the data obtained in a previous study, excluding the uppermost samples in which Nephrolepidina is clearly reworked, being characterized by primitive morphology, i.e., almost isolepidine embryo, few adauxiliary chamberlets, and ogival equatorial chamberlets. The neanic data evidence that the "Degree of stolonic distalization" (Factor FD5) and the "Shape Index" (Factor SI5), at the 5th nepionic stage of the population have a very good fitting with the previously evidenced Neanic acceleration, as the overall trend to modify the shape of the equatorial chambers, connected with a gradually more distal position of the radial stolons. Unispiralled Miogypsina, associated with Nephrolepidina at an advanced evolutionary stage, suggest a continuous reworking of primitive miogypsinids, without an involvement of more evolute bispiralled forms. The biostratigraphic assessment of the Venacquaro and Glauconitic Calcarenite formations is improved, assigning the Venacquaro Formation to the Chattian-lowermost Aquitanian (SBZ22B-basal SBZ24) and the base of the Glauconitic Calcatenite to the Aquitanian (SBZ24 p. p.). The investigated sedimentary succession was deposited along a slope to toe of slope characterized by a mixture of taxa displaced from shallow-water environments and reworked primitive specimens eroded along channels.

Palynomorphs in southern Western Australian lake sediments: evidence of climate change and hypersalinity during the Cenozoic

This study focuses on five cores in and around three of the hundreds of shallow ephemeral hypersaline lakes distributed in chains along traces of ancient drainages that dominate the southern Western Australian landscape. Cores within and on the shore of Lake Aerodrome (LA1-09, LA2-09), Prado Lake (PL1-09, PL2-09), and Gastropod Lake (GLE1-09) in the Cowan Paleodrainage were drilled as part of a multidisciplinary study to understand the evolution of the lakes. Lithological and palynomorph data provide insights into the region’s the depositional history, and floristic and climate evolution of the region. The nearly 60 m deep LA2-09 core provides the most comprehensive data. The basal ∼15 m interval of this core comprises two distinct lignite units with a clay interbed that preserve a rich palynomorph assemblage of the Werillup Formation. This assemblage is characterized by the first appearance datum (FAD) and last appearance datum (LAD) of key late Eocene taxa that correlate with the Middle Nothofagidies asperus Zone, and is indicative of freshwater swamp surrounded by subtropical to temperate rainforest. Above the upper lignite (except the topmost sample), evaporitic-siliciclastic units preserve a depauperate palynomorph assemblage comprising mostly long-ranging sclerophyllic-xerophilous-halophilic taxa. The pollen Myrtaceidites lipsis constrains the age of the upper ∼23 m interval as Pliocene to Recent. This younger assemblage also preserves reworked palynomorphs from the Werillup Formation and older units, and is identified in the other four cores. The presence of the halophilic green alga Dunaliella in the younger assemblage is used as a proxy for aridity and hypersaline conditions during post-Eocene deposition in southern Western Australia. Its absence in the neutral-alkaline lake water and uppermost core samples of GLE1-09 is either due to predation by the acidophobic gastropod Coxiella residing in the lake, or the fact that the type of Dunaliella preserved in the core samples is acidophilic.

Middle Miocene foraminifera from Canals (Valencia, western Mediterranean). Biostratigraphic and palaeoenvironmental aspects

The age and the palaeoenvironmental conditions of the tap marls outcroppings near the locality of Canals in the south of the Valencia Province (E Spain) are discussed. Based on the planktonic foraminifera assemblages, mainly the species Globorotalia praemenardii, these tap marls are dated as Serravallian in age (middle Miocene). The analysis of the foraminiferal assemblages suggests a relatively well-ventilated uppermiddle bathyal environment, with only a moderate oxygen deficiency throughout most of the studied section. The rather cool waters indicated by the planktonic foraminifera(e.g. Globigerina bulloides) are compatible with the decreasing temperatures trend during the middle Miocene due to the extension of the Antarctic Ice Cap. The abundant diatoms and radiolaria, and the highly diverse benthic foraminiferal assemblages are also consistent with prevailing upwelling conditions and a high surface productivity and carbon flux. The apparent warming trend throughout the short section analysed, together with the sharp decrease in diversity and the rise of dysoxic species like Globobulimina affinis at the uppermost sample, might indicate either a short-term warming episode or a restriction of upwelling currents, eventually resulting in more sluggish bottom circulation and less well-oxygenated waters.

Biometric study of late Oligocene larger benthic Foraminifera (Lepidocyclinidae and Nummulitidae) from the Qom Formation, Central Iran (Tajar-Kuh section)

AbstractThe Oligocene strata of the Qom Formation from the Tajar-Kuh section, Central Iran, are rich in various Larger Benthic Foraminifera (LBF). Morphometric studies of the internal features of the LBF tests were carried out based on matrix-free specimens from seven samples. The LBF assemblage studied in 24 populations mainly contains representatives of two nummulitid (the reticulateNummulites bormidiensisTellini, 1888, only in the lower three samples, and the radiateNummulites kecskemetiiLess, 1991 in all samples) and of two lepidocyclinid lineages. Of the latter,Nephrolepidina praemarginata(R. Douvillé, 1908) occurs in all the samples, whereasEulepidina formosoidesH. Douvillé, 1925 is present in the lower six samples. In the upper sample, the slightly more advancedEulepidinaex. interc.formosoidesH. Douvillé, 1925 etdilatata(Michelotti, 1861) is recorded. Due to the very similar taxonomic composition of the Tajar-Kuh section with their coeval faunas of the Mediterranean, the age was evaluated in the frame of the Western Tethyan Oligo-Miocene shallow benthic zonation (SBZ). Although the presence ofE. formosoidessuggests late Rupelian (SBZ 22A Zone) age, the occurrence ofHeterostegina assilinoides,N. kecskemetii,N. bormidiensis, andPlanolinderinasp. preferably represents the SBZ 22B Zone of the early Chattian. Based on the obtained results, at least the lower six samples can indicate the very basal part of the Chattian. More advancedEulepidinafrom the uppermost sample suggests a slightly younger but still early Chattian age.

Fusulinids from slope debris flow beds in the Word Formation (Guadalupian, Middle Permian), Gilleland Canyon, northwestern Glass Mountains, West Texas

Three Guadalupian allochthonous debris flow beds in a slope-to-basin facies succession in northern Gilleland Canyon of the northwest Glass Mountains were sampled for fusulinid biostratigraphic age-dating. The deeper water allochthonous debris flow beds underlie the shelf-margin packstone-grainstone facies of the Willis Ranch Member of the Word Formation (3rd Word Limestone Bed of King 1931) (middle Guadalupian, early Wordian), which forms a distinct bench all along the west wall of Gilleland Canyon (114–169m above base of measured section). The uppermost GV-RC1 sample, from 104 m in the measured section, contained the fusulinids Parafusulina sellardsi, P. antimonioensis, P. deliciasensis, P. rothi, P. trumpyi, and P. boesei. SampleGV-CM1, from 83min the section, contained P. sellardsi, P. deliciasensis, P. rothi, P. boesei, and P. lineata. The lowest sample GV-CM20, from 76 m in the section, contained only P. deliciasensis and P. wildei. According to previous studies, most of these species appear in Roadian-aged strata and range upward into early Wordian-aged strata, but the common occurrence of P. sellardsi in the upper two samples, and the occurrence of P. antimonioensis in the uppermost sample confirm an early Wordian age.

Comparative Lower-Middle Ordovician conodont oxygen isotope palaeothermometry of the Argentine Precordillera and Laurentian margins

Stratigraphic, palaeontologic, and palaeomagnetic data support a hypothesis that argues for the Argentine Precordillera rifting from the southwestern margin of Laurentia in low latitudes during the Cambrian, migrating across the Iapetus Ocean, colliding with the Gondwanan margin in the late Middle Ordovician, and receiving glaciogenic sediments in the Late Ordovician. An alternative model proposes that the Precordillera originated as a low-latitude segment of Gondwana, migrated southward through major transform faulting toward high latitudes in the late Middle Ordovician, to reach its present position in the Devonian. New conodont oxygen isotope compositions (δ18Ophos) have been determined by ion microprobe SHRIMP II using samples from both the Precordillera and Laurentia (Marathon area of Texas, Wilcox Pass in Alberta, and western Newfoundland). Significantly, the δ18O values of conodonts from all four widely separated areas show a consistent pattern of a cyclic but overall increasing trend in δ18O (ca. 16 to 18‰) hence ocean cooling through the Early and Middle Ordovician. An apparent change occurs at the basal Late Ordovician, where δ18O values obtained from conodonts in the uppermost sample from the Precordillera are significantly higher (+1.5‰) than those from Laurentia. Albeit from a single sample, this higher value implies significantly cooler conditions, as would be anticipated with a southerly (poleward) migration of the Precordillera (irrespective of either hypothesis). The virtual absence of conodont-bearing carbonates in most of the Precordilleran Upper Ordovician precluded analysis of younger samples. When combined with existing macrofaunal and palaeomagnetic data, the oxygen isotope data would tend to favour the model of a drift of the Precordillera from tropical to higher latitudes during the Ordovician; however, further studies are needed to determine unequivocally whether the Precordillera originated from southern Laurentia (Ouachita embayment). These new oxygen isotope values provide the best and regionally most consistent data through the Early-Middle Ordovician.

Possible climatic controls on the accumulation of Peru's most prominent alluvial fan: The Lima Conglomerate

AbstractSediment accumulation can occur in response to a change in either tectonic or climatic driving forces. Here, we explore these controls on the deposition of the Lima Conglomerate, Peru. We use a combination of quantitative methods to explore the age of sediment accumulation, the provenance of the material and the paleo‐erosion rates recorded by these deposits. Isochron burial dating with cosmogenic 10Be and 26Al yield an age of c. 500 ka for the base (490 ± 70 ka) and the uppermost sample situated c. 30 m higher upsection (490 ± 80 ka). Results of paleo‐erosion rate estimates with concentrations of in situ 10Be show a c. 60% increase from 105 ± 10 mm ka‐1 for the base to 169 ± 14 mm ka‐1 for the uppermost sample. Finally, provenance tracing with in situ U/Pb ages on detrital zircon implies that the material has been derived from the entire drainage basin. The combination of results suggests that sediment accumulation occurred in response to an erosional pulse, which affected the entire basin within a short time interval. Because 10Be data represents a large spatial record of erosion, we exclude the possibility where a breakout of a lake or a focused release of material in response to earthquakes, were responsible for the large material flux. Instead, the erosional pulse was likely to have occurred at the scale of the entire basin, supporting the idea of a larger‐scale, most likely climate driven control. In this context, the accumulation age of c. 500 ka falls into an orbital cycle fostering the emerging picture in the literature that sediment routing in the Andes have most likely been driven by climate and cyclic changes. We suggest that the Andean mountain range offers an ideal laboratory to explore the erosional history in relation to climate patterns, at least in Peru. © 2018 John Wiley & Sons, Ltd.

Infaunal and epifaunal benthic foraminifera species as proxies of organic matter paleofluxes in the Pelotas Basin, south-western Atlantic Ocean

Abstract One late Quaternary sediment core from the continental slope of the northern sector of Pelotas Basin (southern Brazilian continental margin, 2091 m water depth) was analyzed in order to evaluate the influence of the organic matter influx in the benthic foraminiferal assemblage composition on a regional scale. This study investigated the relationship between epifaunal species (Epistominella exigua and Alabaminella weddellensis) and infaunal species (Uvigerina peregrina and Angulogerina angulosa) integrated in a relative abundance based index, the “Organic Input Index” (OrgIn). The correlation of these species with abiotic data is also discussed, including mud content, total organic carbon (TOC) and carbon stable isotope (δ13C) in Uvigerina peregrina. The age model based on one radiocarbon dating of planktonic foraminifera and oxygen isotope composition of benthic foraminifera (Uvigerina) revealed the record spans the last 112,500 yr, covering the Marine Isotope Stages (MIS) 5 to 3. The dominance of infaunal species, mainly Globocassidulina subglobosa, boliviniids and buliminiids throughout the entire core is interpreted as an indicator of an increase of organic matter supply and dominance of the eutrophic conditions in this study area. The variations found in the proportion of the epifaunal and infaunal species indicate distinctive inputs of organic matter (phytodetritus input versus bacterial activity, respectively). An increasing trend in the importance of epifaunal species from the base of the core to uppermost samples (MIS 5 to MIS 3) was also observed, which is assumed to be evidence of the higher productivity of the surface water masses in this sector of the South Atlantic during the glacial periods.

Late Quaternary climate and environmental reconstruction based on leaf wax analyses in the loess sequence of Möhlin, Switzerland

Abstract. We present the results of leaf wax analyses (long-chain n-alkanes) from the 6.8 m deep loess sequence of Möhlin, Switzerland, spanning the last ∼ 70 kyr. Leaf waxes are well preserved and occur in sufficient amounts only down to 0.4 m and below 1.8 m depth, so no paleoenvironmental reconstructions can be done for marine isotope stage (MIS) 2. Compound-specific δ2Hwax analyses yielded similar values for late MIS 3 compared to the uppermost samples, indicating that various effects (e.g., more negative values due to lower temperatures, more positive values due to an enriched moisture source) cancel each other out. A pronounced ∼ 30 ‰ shift towards more negative values probably reflects more humid conditions before ∼ 32 ka. Radiocarbon dating of the n-alkanes corroborates the stratigraphic integrity of leaf waxes and their potential for dating loess–paleosol sequences (LPS) back to ∼ 30 ka.

Influence of Aquatic Plant Photosynthesis on the Reservoir Effect of Genggahai Lake, Northeastern Qinghai-Tibetan Plateau

AbstractTerrestrial plant remains in the sediments of lakes from semi-arid and arid regions are rare and therefore the establishment of a sediment chronology depends on accurate assessment of the reservoir effect of the lake water. In a study of Genggahai Lake in the Gonghe Basin, northeastern Qinghai-Tibetan Plateau, we used accelerator mass spectrometry radiocarbon (AMS 14C) dating to determine the age of (1) dissolved inorganic carbon in the water (DICLW), (2) macrophyte remains in the uppermost samples of core sediments, (3) living P. pectinatus in the lake, and (4) dissolved inorganic carbon of spring water in the catchment. The results show that the ages of the DICLW (910 14C yr BP on average) were much younger than the ages of the groundwater (6330 14C yr BP on average), which may result mainly from CO2 exchange between the lake water and the atmosphere. In addition, the 14C ages of DICLW and macrophyte remains in the uppermost core sediments varied from site to site within the lake, which we ascribe to the different photosynthesis rates of Chara spp. and vascular plants. The higher photosynthesis rate of Chara spp. decreases lake-water pCO2, which leads to more atmospheric CO2 being absorbed by the lake water, and thereby greatly reducing the age of carbon species in areas dominated by Chara spp. Although Genggahai Lake is well mixed, the differences between the apparent ages of the lake water are significantly modulated by the photosynthesis intensity of submerged plants.

The bony horncore of the common eland (Taurotragus oryx): composition and mechanical properties of a spiral fighting structure.

Horns are permanent structures projecting from the head of bovids, consisting of a bony horncore covered with a layer of skin and then a sheath of keratinous material showing variability of growth intensity based on nutrition. From the point of view of the horn's mechanical properties, the keratin sheath has been widely studied, but only a few studies have considered the complete structure of the horn and fewer studies have focused on the bony horncore and its characteristics. The latter showed the important role of the bony core, when cranial appendages are subject to mechanical stress (as happens during fighting). The mechanical properties of bone material, along with its mineral profile, are also important, because they can show effects of different factors, such as nutrition and mineral deficiencies in diet. For this reason, eight horncores of captive common eland male were sampled at four positions along the vertical axis of the horn. The main aim was to study variation in mechanical properties and the mineral content along the vertical axis of the horncores. We further analysed whether the spiral bony ridge present on eland horncores differs in any of the studied properties from adjacent parts of the horncore. In other antelopes, spiral ridges on the horns have been proposed to increase grip during wrestling between males. Cross-sections of the horncores were performed at four positions along the longitudinal axis and, for each position, two bone bars were extracted to be tested in impact and bending. Moreover, in the first sampling position (the closest position to the base) two bars were extracted from the spiralled bony area. The resulting fragments were used to measure ash content, bone density and mineral content. Results showed that horn bone decreased along the vertical axis, in ash (-36%), density (-32%), and in impact work 'U' (marginally significant but large effect: -48%). The concentration of several minerals decreased significantly (Mg, Cr, Mn and Tl by -33%, -25%, -31%, -43%, respectively) between the basal and the uppermost sampling site. The bone tissue of the horncore spiral compared with non-spiral bone of the same position showed a lower ash content (53% vs. 57%), Mg and Mn; in addition to showing approximately half values in work to peak force 'W', bending strength 'BS' and 'U', but not in Young's modulus of elasticity 'E'. In conclusion, similarly to the results in a totally different fighting bony structure, the antlers, the horncore of eland shows advantageous parameters in bone tissue of the base in respect to the tip, with higher values for mechanical properties, density and mineral profile. Moreover, the spiral bone tissue showed lower material mechanical properties. Probably the spiral tissue of the horn may have a role in deflecting potential cross-sectional fractures during wrestling. In addition, it may serve to improve the grip during wrestling, and we propose that it may also prevent risk of rotation of sheath with respect to internal bone not only in this, but also in other straight bovid horns.

The palynology and geology of the Lower Cretaceous (Aptian–Albian) of Munday’s Hill Quarry, Bedfordshire, UK

Early Cretaceous sediments of Aptian–Albian age outcrop at Munday’s Hill Quarry, Bedfordshire, England. Previous papers describing the section have resulted in different terminologies being applied. The Lower Cretaceous in Bedfordshire is represented by sediments belonging to the Lower Greensand Group and the Gault Clay Formation. Within the Lower Greensand Group in the study area the Woburn Sands Formation, are of Aptian–Albian age. Selected samples have been analysed for palynology. The analysis reveals diverse palynomorph assemblages, including well-preserved dinoflagellate cysts and sporomorphs. Comparison of the assemblages with published records indicates that the lower samples are of Late Aptian age. Forms recorded include common Kiokansium unituberculatum, Cerbia tabulata, Aptea polymorpha and Cyclonephelium inconspicuum. An Early Albian age is indicated for the uppermost sample.

Short-term Creep Properties and Fracture Surface of 18 Ni (300) Maraging Steel Plasma Nitrided

Plasma nitriding of a solution annealed and aged 300 grade maraging steel was studied aiming to increase the creep resistance. The surface microhardness reached 1,140 HV, producing 50 µm layer composed of e-Fe3N and γ'-Fe4N nitrides at the uppermost sample layer. The inner core remained unaltered presenting typical plate-like martensite microstructure of maraging steels with average microhardness of 604 HV. Surface RMS roughness in the nanometric scale increase from 52 nm to 71 nm. The continuous layer of iron nitrides seems to behave as a barrier for oxidation and for inward oxygen diffusion improving the creep resistance by reducing the steady-state creep rate (es) in 52-65% when compared with the literature results. Dominant creep mechanism is controlled by dislocations climb. Fracture surfaces of specimens presented ductile failure consisting of equiaxed and bi-modal dimples in the fibrous zone surrounded by 45o shear lip. Nitrided sample presented a reduced ductility, associated to the hard surface layer.

Paleoenvironmental reconstruction of the coal- and oil shale-bearing interval in the lower Cretaceous Muling Formation, Laoheishan Basin, northeast China

The Laoheishan Basin in northeast China has been filled with Lower Cretaceous coal- and “oil shale”-bearing sediments. The basin fill includes from base to top alluvial conglomerate (lower member of Muling Formation), fan delta sediments interbedded with coal and oil-prone mudstone (denominated as “oil shale”) layers in the upper member of Muling Formation, and volcaniclastic rocks (Dongshan Formation). In the present study, the maturity of organic matter, oil shale quality, and paleoenvironment of the coal and oil shale accumulation are investigated based on macro- and micropetrographic data, proximate and ultimate analyses, bulk geochemical parameters, biomarkers analysis and stable isotope geochemistry.In the Laoheishan Basin, both coal and “oil shale” layers are derived from land plant organic matter. This contrast the “oil shale” of this basin from oil shale/coal intercalations in fault-related basins, in which oil shale has been found to be of algal origin. The coal is sub-bituminous in rank, hydrogen-rich and oil-prone. The “oil shale” is of low-medium grade and the relatively low oil yield may relate to the abundant resinite and sporinite, because of their lower generation potential compared with alginite. Accumulation of the high-ash coal commenced in low-lying mire, drowned during frequent floodings. Subsequently high-ash, low-sulfur coal was deposited in a stable low-lying mire, under oxic conditions and limited bacterial activity. Afterwards the mire was drowned and formed a freshwater, dysoxic to oxic shallow lake, in which “oil shale” layers accumulated. Finally, the depositional environment returned to low-lying mire but probably with a brackish influence, as indicated by elevated sulfur contents in the uppermost samples. Petrography- and biomarker-based proxies indicate that gymnosperms dominated the paleovegetation of the mire, accompanied by variable amounts of herbaceous plants, such as ferns.

Compositional variation within thick (>10 m) flow units of Mauna Kea Volcano cored by the Hawaii Scientific Drilling Project

Geochemical analyses of stratigraphic sequences of lava flows are necessary to understand how a volcano works. Typically one sample from each lava flow is collected and studied with the assumption that this sample is representative of the flow composition. This assumption may not be valid. The thickness of flows ranges from <1 to >100m. Geochemical heterogeneity in thin flows may be created by interaction with the surficial environment whereas magmatic processes occurring during emplacement may create geochemical heterogeneities in thick flows. The Hawaii Scientific Drilling Project (HSDP) cored ∼3.3km of basalt erupted at Mauna Kea Volcano. In order to determine geochemical heterogeneities in a flow, multiple samples from four thick (9.3–98.4m) HSDP flow units were analyzed for major and trace elements. We found that major element abundances in three submarine flow units are controlled by the varying proportion of olivine, the primary phenocryst phase in these samples. Post-magmatic alteration of a subaerial flow led to loss of SiO2, CaO, Na2O, K2O and P2O5, and as a consequence, contents of immobile elements, such as Fe2O3 and Al2O3, increase. The mobility of SiO2 is important because Mauma Kea shield lavas divide into two groups that differ in SiO2 content. Post-magmatic mobility of SiO2 adds complexity to determining if these groups reflect differences in source or process. The most mobile elements during post-magmatic subaerial and submarine alteration are K and Rb, and Ba, Sr and U were also mobile, but their abundances are not highly correlated with K and Rb. The Ba/Th ratio has been used to document an important role for a plagioclase-rich source component for basalt from the Galapagos, Iceland and Hawaii. Although Ba/Th is anomalously high in Hawaiian basalt, variation in Ba abundance within a single flow shows that it is not a reliable indicator of a deep source component. In contrast, ratios involving elements that are typically immobile, such as La/Nb, La/Th, Nb/Th, Ce/Pb, Sr/Nd, La/Sm, Sm/Yb, Nb/Zr, Nb/Y and La/Yb, are uniform within the units, and they can be used to constrain petrogenetic processes. Nevertheless all elements are mobile under some conditions. For example, a surprising result is that relative to other samples, the uppermost sample collected from subaerial flow Unit 70, less than 1m below the flow surface, is depleted in P, HREE and Y relative to all other samples from this flow unit. This result is complementary to the P, REE and Y enrichment found in subaerial lava flows from several Hawaiian shields, e.g., Kahoolawe and Koolau Volcanoes. These enrichments require mobilization of REE and followed by deposition a P-rich mineral.

Radiocarbon dating of fossil bats from Dobšina Ice Cave (Slovakia) and potential palaeoclimatic implications

Although Dobsina Ice Cave (DIC, Carpathians, Slovakia) is located outside the high-mountain area, it hosts one of the most extensive blocks of perennial subterranean ice, the volume of which is estimated at more than 110,000 m 3 . Frozen bat remains were found in the lowermost part of the perennial ice block. They belong to Myotis blythii (Tomes) and the M. mystacinus morpho-group. The radiocarbon dating of bat soft tissues yielded ages of 1266–1074 cal. yr BP and 1173–969 cal. yr BP. The undetermined bat, found in the same part of the ice section in 2002, was previously dated at 1178–988 cal. yr BP (Clausen et al. , 2007). The dates testify that the ice crystallized at the turn of the Dark Ages Cold Period and the Medieval Warm Period. The calculated accumulation rate of cave ice varies between 0.7 cm/year and 1.4 cm/year at that time, and is similar to the present ice accumulation rate in DIC. Constant crystallization of ice during the Medieval Warm Period is hypothesized to reflect dry summer seasons since the supply of relatively warm water in the summer is one of the key factors causing the erosion of cave ice. The uppermost sample was covered with 20.6 m of ice. Between ca 1065 cal. yr BP and the present day, the ice grew faster than between ca 1210 yr BP and ca 1065 yr BP by a factor of 1.3–1.8. This may have resulted from conditions favourable for ice accumulation during the Little Ice Age.

Approaches to quantitative reconstruction of woody vegetation in managed woodlands from pollen records

There has been increasing interest in developing quantitative methods for reconstructing the dynamics of cultural landscapes over the last 15years. This paper adds to this literature by using various approaches to reconstruct the vegetation of two woodlands subject to rotational coppicing (the periodic cutting of broadleaved trees and shrubs for wood products). Pollen deposition at ground level was determined at both sites using ‘Tauber’ traps placed near to the centre of 14 compartments of differing age in the coppice rotation. For the main woody taxa, Relative Pollen Productivity (RPP) estimates were derived using linear regression for pollen influx data and Extended R-value analysis for percentage data. The vegetation around three ponds was reconstructed by applying four methods (inverting the two RPP estimate approaches, the modern analogue technique and correction for pollen productivity using the linear regression estimated RPP values) to pollen data obtained from the uppermost sample of sediment from the ponds. To determine whether these methods gave better estimates of the vegetation composition than the original pollen proportions, the results were compared with the surveyed vegetation around each pond using the Bray–Curtis Index. Linear regression of pollen influx produced RPP values which are comparable with previous European studies, whilst for some taxa the Extended R-value analysis produced estimates which are orders of magnitude different both from values derived from the linear regression and previous work. No single approach performed equally well at reconstructing the vegetation around the ponds, and at two of the three locations the uncorrected pollen proportions were most similar to the surveyed vegetation. We conclude that applying quantitative reconstruction methods to individual small sites is, currently, not likely to be useful in complex cultural landscapes. In the context of coppiced woodland, deficiencies in our understanding of pollen taphonomy and the impact of the practice on pollen production first need to be rectified, and we identify strategies to address this situation.