Palaeoclimatic and regional implications of Older Dryas and Younger Dryas local glacier activity in the low-Arctic valley Finnkongdalen,Andøya,northern Norway

Continuous glacier margin and equilibrium-line altitude fluctuations of a former glacier on central Andøya, northern Norway, are reconstructed during the Lateglacial based on moraines and AMS ¹⁴C-dated sediments from the distal glacier-fed lake Ner-Finnkongdalsvatnet. The results indicate that a valley glacier occupied the entire valley during the Last Glacial Maximum (before 21 970±620 cal. a BP). The glacier remained large throughout the early Lateglacial until a significant glacier retreat took place about 14 300±330 cal. a BP. Major advances occurred during the Older Dryas (OD) and during the Younger Dryas (YD), while minor advances are suggested to have taken place during the Intra Allerød Cold Period and the Late Allerød Cooling. Additionally, three smaller glacier retreats/re-advances within the YD are suggested to have taken place, the latter being the largest. The glacier re-formations/advances during the Lateglacial are consistent with increases in temperature, and they are thus suggested to be the result of increased winter precipitation. Comparing the results with relevant glacier and sea-surface temperature records, a south–north migration of storm tracks may have occurred between 12 100–11 810±220 cal. a BP. The high temporal resolution of local glacier activity in Finnkongdalen improves our understanding of the climate forcing of the regional glacier fluctuations of the northwestern sector of the Scandinavian Ice Sheet during the Skarpnes- (OD) and Tromsø-Lyngen (YD) re-advances.     

Impact of Pleistocene–Holocene climate shifts on vegetation and fire dynamics and its implications for Prearchaic humans in the central Great Basin,USA

The effects of climate change during the Terminal Pleistocene–Early Holocene transition on ecosystems and early Prearchaic hunter-gatherers in the central Great Basin of North America are not well understood. We present a palynological reconstruction of regional vegetation and fire history in Grass Valley, central Nevada, from ~14 to ~7.5k cal a BP showing that Pinus-dominated woodlands were replaced by dry-adapted steppe and desert vegetation accompanied by an increase in regional fire activity at the beginning of the Holocene, in response to summer warming and a drying climate. Following a severe drought period peaking ~10.2–9.3k cal a BP, Pinus woodlands partially recovered contemporaneously with the 8.2k cal a BP climate anomaly. Local wetlands provided important resource patches for human foraging societies, and periodic declines of wetlands in response to changing local hydrological conditions may have necessitated adjustments in subsistence and settlement practices and technology.     

Seasonality in the North Sea during the Allerød and Late Medieval Climate Optimum using bivalve sclerochronology

Seasonal temperature patterns may have changed through time in response to current global warming. However, the temporal resolution of available proxy records is not sufficient to quantify paleotemperature seasonality prior to anthropogenic forcing of the climate. In the present study, we reconstructed seasonal and inter-annual temperature patterns of the North Sea during the last 140 years, the Allerød Interglacial and the Late Medieval Climate Optimum using sclerochronological and δ¹⁸O_aragonite data from bivalve shells, Arctica islandica. On average, the climate during 1278–1353 AD was ca. 1.1°C colder and seasonality was ca. 60% less than today. During the Allerød, long-term temperatures remained about 3.2°C below present values, and absolute summer and winter anomalies were ca. ?4 and ?2.7°C, respectively. However, seasonality was statistically indistinguishable from today. Long-term average temperatures compare well with existing data for the Late Medieval and Allerød, but detailed information on seasonality during the studied time intervals has never been presented before. Our data also demonstrated that annual instrumental and δ¹⁸O_aragonite-derived temperatures did not always match. This difference is explained by (1) NAO-driven salinity changes, which influence the temperature estimation from δ¹⁸O_aragonite and (2) food-driven changes in growth rates; portions of the shell that formed more rapidly are overrepresented in carbonate samples. Our study indicated that individual bivalve shells can open discrete, near-century long, ultra-high-resolution windows into the climate past. Such information can be vital for testing and verifying numerical climate models.     

Warming and environmental changes in the eastern North Sea Basin during the Palaeocene–Eocene Thermal Maximum as revealed by biomarker lipids

Analysis of sediments deposited at different latitudes around the world during the Palaeocene–Eocene Thermal Maximum (PETM; ∼56 Ma) have revealed a globally profound warming phase, regionally varying from 5–8 °C. Such records from Europe have not yet been obtained. We studied the variations in sea surface and continental mean annual air temperatures (SST and MAT, respectively) and the distribution patterns and stable carbon isotopes of higher plant derived n-alkanes in two proximal PETM sections (Fur and Store Bælt, Denmark) from the epicontinental North Sea Basin. A negative carbon isotope excursion (CIE) of 4–7‰ was recorded in land plant derived n-alkanes, similar to what has been observed for other PETM sections. However, differences observed between the two proximal sites suggest that local factors, such as regional vegetation and precipitation patterns, also influenced the CIE. The presence of S-bound isorenieratene derivatives at the onset of the PETM and increased organic carbon contents points to a rapid shift in depositional environment; from well oxygenated to anoxic and sulfidic. These euxinic conditions are comparable with those during the PETM in the Arctic Ocean. SSTs inferred from TEX₈₆ show relatively low temperatures followed by an increase of ∼7 °C across the PETM. At the Fur section, a remarkably similar temperature record was obtained for MAT using the MBT′/CBT proxy. However, the MAT record of the Store Bælt section did not reveal this warming.     

Hydrothermal mineralization in the sandstone–hosted Hangjinqi uranium deposit,North Ordos Basin,China

Tabular–type uranium ore deposits (the Hangjinqi and Daying deposits) have recently been found in the Middle Jurassic Zhiluo Formation, north of the Ordos Basin, China. Petrographic observations, the chemical composition of U minerals determined by EMPA and fs–LA–ICP–MS, whole rock geochemistry and the microthermometric study of fluid inclusions have been integrated to characterize the genetic conditions of the U mineralization in the Hangjinqi sandstone–hosted deposit. Two different groups of U minerals have been identified. One group includes coffinite(I) associated with vanadium–rich micas. Coffinite(I) is enriched in vanadium (V) and devoid of iron (Fe) and yttrium (Y) and has a LREE–enriched chondrite–normalized REE pattern. The U minerals of this group are similar to meteoric fluid infiltration related deposits. The second group has coeval coffinite(II) and coarsely crystalline calcite cement. Coffinite(II) is enriched in Y and Fe and depleted in V and is marked by a flat chondrite–normalized REE pattern, which is compatible with typical hydrothermal genetic deposits with high–salinity mineralizing fluids. The temperature and salinity of the primary aqueous inclusions in the ore–stage calcite are 120–180 °C and 8.00–16.34% (eq. wt% NaCl), respectively. These mineral assemblages, temperatures and salinities indicate that the Hangjinqi deposit was affected by two distinct types of ore–bearing fluids: low–salinity meteoric waters and high–salinity hydrothermal fluids. The meteoric fluids event began at 97 ± 5 Ma with the titling of the northern Ordos Basin and the uplift of the Hetao region to the north. Hydrothermal U mineralization occurred since 39 ± 2 Ma with the rifting of the Hetao graben. Thus, the previous biogenic model for the U mineralization should be modified in the uraniferous region of the north Ordos Basin.     

Late Carboniferous–Early Permian Sequence Stratigraphy and Depositional Evolution in the Northeast Ordos Basin, North China

Sequence stratigraphical analysis was applied to the Upper Carboniferous–Lower Permian sedimentary succession of the northeastern Ordos Basin, north China based on data acquired from ten entire logging curves and eight outcrops. The facies framework of the lithostratigraphical unit, the Taiyuan Formation comprises seven facies in two facies associations, varying from fluvio-delta to shelf-barrier islands. The facies are presented within a chronostratigraphical framework, linked by systems tract, which in turn are limited by flooding surfaces and sequence boundaries. Six third-order depositional sequences are recognised, bounded by six type 2 unconformities. An upwards-shallowing epicontinental sea sedimentary model is created, which consists of a sandstone, coal seam and carbonate succession.     

Meso–Cenozoic thermal regime in the Bohai Bay Basin,eastern North China Craton

This article discusses the Meso–Cenozoic thermal history, thermal lithospheric thinning, and thermal structure of the lithosphere of the Bohai Bay Basin, North China. The present-day thermal regime of the basin features an average heat flow of 64.5 ± 8.1 mW m^–2, a lithospheric thickness of 76–102 km, and a ‘hot mantle but cold crust’-type lithospheric thermal structure. The Meso–Cenozoic thermal history experienced two heat flow peaks in the late Early Cretaceous and in the middle to late Palaeogene, with heat flow values of 82–86 mW m^?2 and 81–88 mW m^?2, respectively. Corresponding to these peaks, the thermal lithosphere experienced two thinning stages during the Cretaceous and Palaeogene, reaching a minimum thickness of 43–61 km. The lithospheric thermal structure transformed from the ‘hot crust but cold mantle’ type in the Triassic–Jurassic to the ‘cold crust but hot mantle’ type in the Cretaceous–Cenozoic, according to the ratio of mantle to surface heat flow (q_m/q_s). The research on the thermal history and lithospheric thermal structure of sedimentary basins can effectively reveal the thermal regime at depth in the sedimentary basins and provide significance for the study of the basin dynamics during the Meso–Cenozoic.     

Arman’ Flora of the magadan region and development of floras in the North Pacific during the Albian-Paleocene

The Arman’ Flora from volcanogenic-sedimentary deposits in the Arman’ River basin and Naraula Formation in the Nel’kandzha-Khasyn interfluve includes 82 species of fossil plants comprising liverworts, horsetails, ferns, caytonealeans, cycadaleans, ginkgoaleans, czekanowskialeans, conifers, gymnosperms incertae sedis, and angiosperms. The Arman’ Flora appears to be of Turonian-Coniacian age, as it is close to the reliably dated Penzhina and Kaivayam floras from the Northwest Kamchatka and to Tyl’pegyrgynai Flora of the Pekul’nei Ridge. The dating is consistent with isotopic dates (⁴⁰Ar/³⁹Ar and U-Pb SHRIMP) characterizing the age of plant-bearing sequences. Based on the considered position of the Arman’ Flora in the scheme of Cretaceous florogenesis, a leading role in that florogenesis was played by the gradual invasion of floras by new, angiosperm dominated, plant communities. These communities initially populated unstable habitats in the coastal lowlands of Northeast Asia and Alaska, gradually invading with time the Asiatic intracontinental areas. The peculiar combination of Early and Late Cretaceous plants characteristic of the Arman’ Flora is strong evidence that Cenophytic plant communities dominated by angiosperms colonized areas still populated in the Late Cretaceous by Mesophytic communities. Absence of Mesophytic and Cenophytic taxa mixing in the Arman’ Flora burials suggests a replacement of plant communities as whole rather than of separate plants by more advanced taxa.     

Holocene fire occurrence and alluvial responses at the leading edge of pinyon–juniper migration in the Northern Great Basin,USA

Fire and vegetation records at the City of Rocks National Reserve (CIRO), south-central Idaho, display the interaction of changing climate, fire and vegetation along the migrating front of single-leaf pinyon (Pinus monophylla) and Utah juniper (Juniperus osteosperma). Radiocarbon dating of alluvial charcoal reconstructed local fire occurrence and geomorphic response, and fossil woodrat (Neotoma) middens revealed pinyon and juniper arrivals. Fire peaks occurred ~ 10,700–9500, 7200–6700, 2400–2000, 850–700, and 550–400 cal yr BP, whereas ~ 9500–7200, 6700–4700 and ~ 1500–1000 cal yr BP are fire-free. Wetter climates and denser vegetation fueled episodic fires and debris flows during the early and late Holocene, whereas drier climates and reduced vegetation caused frequent sheetflooding during the mid-Holocene. Increased fires during the wetter and more variable late Holocene suggest variable climate and adequate fuels augment fires at CIRO. Utah juniper and single-leaf pinyon colonized CIRO by 3800 and 2800 cal yr BP, respectively, though pinyon did not expand broadly until ~ 700 cal yr BP. Increased fire-related deposition coincided with regional droughts and pinyon infilling ~ 850–700 and 550–400 cal yr BP. Early and late Holocene vegetation change probably played a major role in accelerated fire activity, which may be sustained into the future due to pinyon–juniper densification and cheatgrass invasion.     

Phytoplankton,protozooplankton and nutrient dynamics in the Bornholm Basin (Baltic Sea) in 2002–2003 during the German GLOBEC Project

From March 2002 to until April 2003 we investigated the seasonal nutrient and phytoplankton dynamics in the central Bornholm Basin (Baltic Sea) within the framework of the German GLOBEC Project. We choose a nested approach consisting of vertical fluorescence profiles, phytoplankton counts and nutrient analyses. The Fluoroprobe (MultiProbe, BBE Moldaenke) is capable of distinguishing four algal groups (Cryptophyceae, Cyanophyceae, Chlorophyceae, Bacillariophyceae + Dinophyceae). Winter nutrient concentrations were about 5 μM NO₃ and 0.5 μM PO₄ in the central Basin. The spring phytoplankton bloom was dominated by the diatom Skeletonema sp. and reached a maximum of about 270 μg C/l before the onset of the seasonal stratification. Protozooplankton was dominated by the Mesodinium rubrum (a phototrophic ciliate = Myrionecta rubra) and reached a maximum biomass of about 200–300 μg C/l about 2 weeks after the demise of the diatom spring bloom. During summer, the water column was stratified and a subsurface maximum developed near the thermocline consisting of Bacillariophyceae, Cryptophycea and other phototrophic flagellates. Phytoplankton and protozooplankton biomass was generally low. Nutrient concentrations point towards a nitrogen limitation during this period. The stratification period ended during September and surface nutrient concentrations increased again. Protozooplankton reached a second maximum during September. With the Fluoroprobe small scale structures in the plankton community could be detected like a subsurface Cryptophyceae maximum near the thermocline that however, could not be confirmed by cell counts. The chlorophyll a estimate of the Fluoroprobe was in good agreement with the phytoplankton biomass estimated from counts. We conclude that only by combining modern sensing technology with microscopy, the small-scale dynamics and taxonomic spectrum of the plankton can be fully captured.     

From land to sea: provenance,composition, and preservation of organic matter in a marine sediment record from the North-East Greenland shelf spanning the Younger Dryas–Holocene

The organic matter content of marine sediments is often used to infer past changes in ocean conditions. However, the organic carbon pool preserved in coastal sediments is a complex mixture derived from different sources and may not reflect in situ processes. In this study, we combine taxonomic identification of reworked palynomorphs with pyrolysis organic geochemistry and reflected-light organic petrographic microscopy to investigate the provenance, composition and preservation of organic matter in a marine sediment core retrieved from the NE Greenland shelf. Our study reveals continuous yet variable input of land-derived organic carbon to the marine environment throughout the late Younger Dryas–Holocene, with the highest input of inert carbon in the late Younger Dryas. Although the sediments contain some recent marine palynomorphs, there is no other evidence of fresh marine organic carbon. In contrast, our results indicate that these shelf sediments represent a significant sink of recycled organic carbon. The results of pyrolysis geochemistry revealed that ~90% of the total organic carbon in the sediments is inert. The organic petrography analyses revealed that >70–84% of the organic carbon in the sediment core is terrigenous. Reworked dinoflagellate cysts showed a continuous provenance of Cretaceous land-derived material, most likely from the nearby Clavering Island. Our study points to the importance of constraining the organic matter origin, composition and preservation in marine sediments to achieve more accurate palaeoenvironmental reconstructions based on organic proxies.     

Geochronology,Mineralogy, and Geochemistry of the Tonsteins from the Permo–Carboniferous Benxi Formation,Ordos Basin,North China Craton

Tonstein layers are found worldwide in the Permo–Carboniferous coal-bearing strata. This study investigates the geochronology, mineralogy, and geochemistry of four tonstein samples from the Permo–Carboniferous Benxi Formation, Ordos Basin, North China Craton(NCC). The typical features of the studied tonsteins include thin beds, lateral continuity, angular quartz grains, and euhedral zircons with similar U-Pb ages, indicating a significant pyroclastic origin. In addition, the tonstein samples hav...     

Fault-block structure and state of stress in the Earth’s crust of the Gusinoozersky Basin and the adjacent territory,western Transbaikal region

The geological structure and tectonophysics of the Gusinoozersky Basin—a tectonotype of Mesozoic depressions in the western Transbaikal region—is discussed. New maps of the fault-block structure and state of stress in the Earth’s crust of the studied territory are presented. It is established that the Gusinoozersky Basin was formed in a transtensional regime with the leading role of extension oriented in the NW-SE direction. The transtensional conditions were caused by paths of regional tension stresses oriented obliquely to the axial line of the basin, which created a relatively small right-lateral strike-slip component of separation (in comparison with normal faulting) along the NE-trending master tectonic lines. The widespread shear stress tensors of the second order with respect to extension are related to inhomogeneities in the Earth’s crust, including those that are arising during displacement of blocks along normal faults. Folding at the basin-range boundary was brought about by gravity effects of normal faulting. The faults and blocks in the Gusinoozersky Basin remained active in the Neogene and Quaternary; however, it is suggested that their reactivation was a response to tectonic processes that occurred in the adjacent Baikal Rift Zone rather than to the effect of a local mantle source.     

Zoogeography and imperial defence: Tracing the contours of the Nearctic region in the temperate North Atlantic, 1838–1880s

This paper focuses on the ‘zoogeographic region’ and the ‘zoogeographical boundary-line’ as key biogeographical constructs of empire. More specifically, it investigates how army and navy officers stationed at Halifax and Bermuda on the North America and West Indies Station helped to create an imperial, militarized ‘New World’ region in the North Atlantic through zoogeography in the British post-emancipation era. The tracing of the boundary-line between the temperate (Nearctic) and tropical (Neotropical) North Atlantic involved designating Bermuda and Halifax as strategic winter and summer ‘homes’ on the Station, and highlighting the ‘natural’ connections between the two sites through mobile fauna, ocean currents, and weather systems. Making visible the geographic distribution of migratory animals, the Gulf Stream, and hurricanes – through maps, natural collections, sketches, and travel-writing – provided new ways of seeing and thinking about British imperial defence in the North Atlantic. This paper also considers the role of non-human mobilities in animating these regions.     

Drought and institutional adaptation in the Great Plains of Alberta and Saskatchewan, 1914–1939

Agriculture in the southern Great Plains of Canada has been particularly vulnerable to prolonged episodes of drought. Using climate data and a precipitation minus potential evapotranspiration index, the extent of the region’s exposure to drought is examined. Between 1914 and 1917, the Dry Belt was particularly vulnerable to drought, whereas after 1928, a much larger region known as the Palliser Triangle covering most of southern Alberta and Saskatchewan was much more exposed to drought. These droughts provoked major institutional adaptation, in particular the establishment of the Special Areas Board by the Government of Alberta, and the creation of the Prairie Farm Rehabilitation Administration by the Government of Canada. Both organizations have proved to be relatively permanent public adaptations to the natural hazard of drought in the region. Moreover, these earlier experiences with prolonged drought as well as institution-building may be of value in helping the residents of the Palliser Triangle adapt to predicted climate changes in the future as well as anticipate some of the barriers to effective institutional adaptation.     

Interpreting amenities,envisioning the future: common ground and conflict in North Carolina’s rural coastal communities

This paper contributes to ongoing discussions about the implications of rural change and amenity migration for members of diverse rural communities. We engage with recent amenity migration and political ecology literature that focuses on social constructions of nature and landscapes, and how these constructions affect the attitudes and opinions of community members. We use our case study of a mail-based survey in Down East, North Carolina to suggest that the ways in which people conceptualize the particular ‘natures’ and landscapes of a place matters in terms of shaping people’s attitudes with respect to ongoing processes of change. We find that people’s opinions about environment, culture, and land use are often superficially similar but that when conflicts arise or particular actions are considered, substantial differences in people’s underlying conceptual frameworks are revealed. In particular we find that despite widespread shared appreciation of the environment and culture Down East, differing interpretations of these key terms lead to potential misunderstandings and land use planning challenges.     

Crustal Poisson’s ratio anomalies in the eastern part of North China and their origins

Seismic tomography can provide both fine P-wave and S-wave velocity structures of the crust and upper mantle.In addition,with proper computation,Poisson’s ratio images from the seismic velocities can be determined.However,it is unknown whether Poisson’s ratio images have any advantages when compared with the P-wave and S-wave velocity images.For the purposes of this study,high-resolution seismic tomography under the eastern part of North China region was used to determine detailed 3-D crustal P- and S-wave seismic velocities structure,as well as Poisson’s ratio images.Results of Poisson’s ratio imaging show high Poisson’s ratio(high-PR) anomalies located in the Hengshan-North Taihang-Zhangjiakou(H-NT-Z) region,demonstrating that Poisson’s ratio imaging can provide new geophysical constraints for regional tectonic evolution.The H-NT-Z region shows a prominent and continuous high-PR anomaly in the upper crust.Based on Poisson’s ratio images at different depths, we find that this high-PR anomaly is extending down to the middle crust with thickness up to about 26 km.According to rock physical property measurements and other geological data,this crustal Poisson’s ratio anomaly can be explained by Mesozoic partial melting of the upper mantle and basaltic magma underplating related to the lithospheric thinning of the North China craton.