Where are all the crinoids? An enigma of the Lower Carboniferous (Mississippian) White Peak of midland England

A glut of fossil crinoids does not lead to a succession being recognised as rich in crinoids. Crinoid palaeontology relies on cups, crowns and complete specimens, not fragments. The Carboniferous Limestone of the White Peak is rich in crinoid fragments, but depauperate in named crinoids. Something needs to be done.     

Where are the remnants of a Jurassic ocean in the eastern Mediterranean region?

The subduction polarity of Tethyan oceanic lithosphere during Jurassic is a controversial topic in relation to the geodynamic evolution of the Alpine–Himalayan system. We present new geological, geochemical and zircon U–Pb data from four different regions of the Eastern Pontides Orogenic Belt, a key area of the Alpine–Himalayan system. We discuss the origin of the magmatism and also the existence of an ocean in the eastern Mediterranean region during the Jurassic period. Jurassic intrusions, predominantly gabbro, tonalite and minor diorite, are well exposed in the southern and axial zones of the orogenic belt. Thermobarometry indicates that high-pressure (6–10 kb) crystallization of these intrusions occurred at temperatures of 1183–1250 °C. Zircon U–Pb dating from 10 samples show ages between 195 and 165 Ma, indicating that magmatism occurred between Sinemurian and Callovian time. We characterize the intrusions from electron microprobe, zircon geochronology, and whole rock and Sr, Nd, and Pb isotopes. Our data show that the studied intrusions are broadly tholeiitic, except for two calc-alkaline bodies, and formed in an arc-related setting with minimal involvement of older crust or sediment.The most widely accepted model proposes that the ultramafic–mafic rocks exposed between the Pontide arc and the Tauride belt are remnants of a Jurassic Penrose-type and/or suprasubduction zone ophiolite. However, new zircon U–Pb age data from mafic lithologies cutting the Kop ultramafic massif do not support this model and clearly indicate that the ultramafic lithologies are Paleozoic or older in age and are not remnants of a Jurassic ocean that known as ‘’Northern Branch of Neotehtys”.     

On and Off the North China Craton: Where is the Archaean Keel?

Geophysical data indicate that the lithosphere beneath the NorthChina Craton (NCC) is     

Developing the water commons? The (post)political condition and the politics of “shared giving” in Montana

This paper chronicles the rhetorical mechanisms that fostered a potentially radical re-thinking of water rights and property in a most unlikely place: the libertarian Western U.S., and mobilized by the least likely of actors: state officials. There is growing interest, in geography and beyond, in the question of what constitutes the “properly political” in contexts where dissent is actively forestalled by those with power. Much has been written about the “properly political” as the disruption of the established order by previously excluded actors. Comparatively less research, however, has focused on the “conditions of possibility” that might exist within ostensibly “post-political” governing arenas. This paper deepens our understanding of this by examining a participatory water planning group in Montana, which was convened by the state to develop recommendations for a new state water plan. The group was inspired by an alternative drought-management model called “shared giving.” Imbued with principles of “collectivism” and “equality,” the model was strategically (and necessarily) promoted through the discursive shell of the existing prior appropriation system. This was accomplished not by an oppositional force of marginalized actors, but state officials that are rarely, if ever, deemed “disruptive,” and through tactics that are best characterized as post-political. We interpret this case as reflecting a hybrid governing assemblage that highlights both post-political closure and transformative possibilities simultaneously, and conclude by suggesting that the post-political concept, itself, risks foreclosing on conditions whereby fruitful outcomes might become possible from within established governing frameworks otherwise written-off as post-political.     

A chalk revolution: what have we done to the Chalk of England?

Inversion tectonic episodes are identified in the Upper Turonian - Lower Coniacian, Santonian - Lower Campanian and later Lower Campanian Chalk. It is suggested that episodic tectonism created the seabed topography on which sea levels and erosional currents acted. Marked differentiation into linear belts of local basins and swells with a greater variety of sediments is present in the Santonian and Lower Campanian. During this same period the locus of sedimentation shifts westwards from the southern margin of the Weald to Wessex as Weald Basin inversion increases. Tectonic episodes also produced synsedimenary fracturing of the Chalk and evolution of vein networks and stylolytes. Upper Cretaceous tectonic and sea-level events also affected the platform of Europe, the Carpathians and the Syrian Arc where sedimento-tectonic scenarios provide analogues for the Chalk. Linking sea-level oscillations and tectonic episodes with microtectonic studies suggests a frequency of events within the range of 0.35-1.5 Ma.     

Quartz-dominated Cenozoic gravels in southeastern Australia: where did all the quartz come from?

Upper Cenozoic fluvial gravels in the Canberra region are quartz-dominated (>95 vol% quartz), whereas modern bedload sediments contain less than 50 vol% quartz and a range of lithologies that broadly reflect the catchment geology. Potential reasons for the compositional difference include changes in catchment geology, sediment transport distance, post-depositional weathering and regolith history. Breakage of unsound clasts during transport does not explain the difference because sediment transport distances in the Cenozoic were similar to today. Post-depositional weathering of less resistant clasts is ruled out because the Cenozoic gravels are clast-supported and preserve original bedding. During much of the Cenozoic, rainfall was significantly higher than the present, and rainforest species were present in the local and regional vegetation. Weathering regimes were likely very different from today, and deep weathering of catchment lithologies may have favoured the supply of quartz-rich gravelly sediment to the river systems.     

Where are the Volcanic Calderas in the Xiangshan Volcanic Basin of Jiangxi? Implications from Anisotropy of Magnetic Susceptibility

<正>Objective As the world's third largest volcanic type uranium ore field,the Xiangshan volcanic basin has attracted much attention for its large industrial value.The ore hosting rocks are mainly the early Cretaceous rhyodacite and porphyroclastic lava,as well as small amounts of high level intrusive acidic rocks and metamorphic rocks.The vertical alteration of polymetallic mineralization-related     

Salts in the clay playas of China’s arid regions: gone with the wind

In China’s arid regions, aeolian salts are transported along with dust aerosols, but their contents and the emission rates are poorly understood. Using samples with undisturbed surfaces and artificially disrupted surfaces (to simulate human disturbances such as reclamation, planting, trampling by animals, and other activities), the transport rates for windblown material and the salt contents of clay playa surfaces were investigated in a wind tunnel. The results showed that under wind velocities ranging from 8 to 22 m/s, wind erosion rates ranged between 0.009 and 0.066 g/m²/s for the undisturbed surfaces and between 0.011 and 0.048 g/m²/s for the artificially disrupted playa surfaces. Although the amount of wind-transported material that was captured was too small to allow an analysis of individual salt contents using the available equipment, electrical conductivity measurements and correlation analysis revealed mean total salt contents of 9.59 g/kg in the transported materials collected above the sealed playa surfaces versus 3.38 g/kg in materials from the same surfaces that were artificially cracked after testing the sealed surfaces. Given the large areas containing clay playas in China’s arid regions, these results will improve our understanding of aeolian salt transport in arid China and will facilitate interpretation of the sources of aeolian salts.     

Where does the South Anyui suture go in the New Siberian islands and Laptev Sea?: Implications for the Amerasia basin origin

The South Anyui suture is a major tectonic boundary in NE Asia, believed to represent the remains of an ocean basin which separated Siberia from North America in Jurassic time. Its history also figures prominently in the Mesozoic reconstruction of the Arctic and the origin and evolution of the Amerasia basin. Three types of proposed trends of the South Anyui suture are evaluated. 1) The suture ends near the Kolyma River mouth where it meets the rotational transform. The paper, however, proves that the suture continues further westward up to Big Lyakhov Is. Consequently, a simple geometric rotational model for Amerasia basin origin must be rejected. 2) The suture trends from Big Lyakhov to the Anjou islands. The Anjou islands geology is examined, and it is concluded that the suture could not go through them. Hence, all proposed versions of the rotational hypothesis of the Amerasia basin opening are claimed to be invalid. 3) A proposed Taimyrian connection of the suture is examined, and it is concluded that this model must be rejected as well. The failure of all previously suggested models for the suture extent through the New Siberian islands and Laptev Sea means that in Early Mesozoic there was no oceanic basin that separated the New Siberian–Chukotka terrane from Siberia. Thus Siberia and North America formed a continuous continent in Jurassic time. This paper presents evidence that the South Anyui suture has instead turned back from Big Lyakhov island and followed a sinuous path designated as the Chroma Loop before connecting with the Kolyma Loop suture. On this model the South Anyui suture can be interpreted as a small segment of extensive boundary which separated the Amerasia Jurassic margin and terranes accreted to it from the Pacific. The modern boundary around the North Pacific is also quite sinuous. It was suggested that in Jurassic time it was straighter and the Amerasia ocean was originated as a common back-arc basin. Finally a new two-pole parallelogram hypothesis for the Amerasia basin opening is suggested and the approaches to its verification are outlined.     

Where were the Metal, Sulfur and Water from in the Postcollisional Porphyry Cu Deposit at Qulong in South Tibet?

正Objective Most porphyry Cu deposits(PCDs)were formed in association with subduction-related calc-alkaline magmas,which occurred widely in magmatic arcs worldwide.A widely accepted model is that such deposits were formed from hydrothermal fluids exsolved from hydrous,high oxygen fugacity,sulfur-rich arc magmas,derived from a     

Do low surface brightness galaxies have dense disks?

The disk masses of four low-surface-brightness (LSB) galaxies are estimated using the criterion of marginal gravitational stability. The constructed mass models are close to those for a maximum disk. The results show that the disks of LSB galaxies may be significantly more massive than is usually believed based on their brightnesses. In this case, their surface densities and masses are fairly typical for higher-surface-brightness spirals. Alternatively, it may be that LSB disks are dynamically overheated.     

What have natural and human changes wrought on the foraminifera of San Francisco Bay late Quaternary estuaries?

In this study we compare the foraminifera of modern South San Francisco Bay with fossils from sediments of a previous estuary at 125 ka to provide a basis for interpreting the impact of natural and human change on the benthic ecosystem. All the species found in the Pleistocene sediments of this study are estuarine and/or shallow-water species occurring commonly in San Francisco Bay today, except for the introduced foraminifer Trochammina hadai, a native of Japan that was not found in samples taken in San Francisco Bay before 1983. The biodiversity and species composition of the fossil and modern assemblages before the introduction of T. hadai are nearly identical, suggesting that the environmental and physical changes in the 125,000-year-old and modern estuaries have not had a significant effect on the meiofauna of the Bay. In contrast, modern anthropogenic change in the form of species introductions has impacted the modern foraminiferal assemblage: T. hadai began to dominate the modern assemblage a decade after its introduction. Similar to the recorded impacts of introductions of marine metazoan invertebrate species, the dominance of T. hadai changed species proportions in the post-1980s foraminiferal assemblage, however no known extinctions in the native foraminiferal fauna occurred.     

Israel’s Eastern border: Ask not ‘Where is the Green Line?’ Ask ‘What is the Green Line?’

The Green Line constituted the armistice line between Israel and Jordan during the period 1949-1967. This paper discusses the familiarity of Israeli students with the nature and geographical location of the Green Line by restructuring and analyzing their mental maps. The findings of this study show that students who are men, long-term residents, identify themselves on the left end of the political spectrum, and professional geographers, show better knowledge concerning the issue of borders. However, most students revealed a certain vagueness and even ignorance concerning both spatial perception of the Green Line and its essence. The reasons for the revealed phenomenon are also discussed in this paper, as well as the behavioral implications of the familiarity with the Green Line, both in spatial and political contexts.     

Do mature hydrocarbons have an influence on acid rock drainage generation?

The generation of acid rock drainage (ARD) is a biogeochemical process that causes severe ecological impacts, threatening human health worldwide. Microbes involved in acid drainage reactions are generally considered autotrophic but heterotrophic and mixotrophic microorganisms have often been identified at ARD sites. This raises questions about the role of organic matter naturally present at these sites, such as mature hydrocarbons, in promoting the microbial processes underpinning ARD generation. To investigate this, aerobic microcosm experiments were carried out using ARD samples collected at a well-characterised site in northern England (Mam Tor, Derbyshire). Organic analyses indicated the presence of substantial amounts of mature, petroleum-derived hydrocarbons and microbial analyses indicated that the sediment hosts acidophilic bacteria with the capability of degrading petroleum-derived compounds. However, the aerobic microcosm experiments indicated that these petroleum-derived hydrocarbons were not used by the bacterial community and, therefore, are not involved in the reactions that ultimately lead to ARD generation. These observations support a primary role for autotrophs in ARD generation.