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Labechia carbonaria Smith 1932 in the Early Carboniferous of England;affinity,palaeogeographic position and implications for the geological history of stromatoporoid-type sponges

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Journal of Palaeogeography 2021年第1期10卷 1-18页

作者： Stephen Kershaw Consuelo Sendino Department of Life Sciences Brunel University LondonKingston LaneUxbridge UB83PHUK Department of Earth Sciences Natural History MuseumCromwell RoadLondon SW75BDUK

Stromatoporoid sponges were very abundant during the middle Palaeozoic Era and are thought to disappear at the end of the Devonian Period in the Hangenberg Crisis. However, there are records of organisms with stromatoporoid-type structure in Carboniferous strata, the subject of this study. The Viséan fossil Labechia carbonaria Smith 1932 has been discussed previously in literature and its affinity has not been confirmed. In this study, the type material of L. carbonaria collected from the middle part of the Frizington Limestone Formation(previously called Seventh Limestone), Holkerian Substage, stored in the Natural History Museum(London, UK) and british geological survey(Keyworth, UK) was re-examined. The Holkerian Substage, in which L. carbonaria was found, lies between ca 335–339 Ma, and the Frizington Limestone Formation ranges from topmost Arundian to upper Holkerian, so middle Frizington Limestone Formation is likely approximately 337 Ma. L. carbonaria comprises thick long pillars connected by thin curved cyst plates consistent with the structure of the stromatoporoid genus Labechia. However, a common opinion is that L. carbonaria fossils may be mistaken for fragments of rugose corals,but there are problems with assigning it to the Rugosa. In vertical section(VS) L. carbonaria could be mistaken for a transverse section(TS) of a Carboniferous rugose coral. However, in TS L. carbonaria shows the rounded cross sections of stromatoporoid pillars. If it was a coral, septal sheets of the VS of a coral should be seen. For a rugose affinity to still apply, a coral structure would have to be composed of free trabeculae, but these are not known after the middle of the Devonian Period;there are no corals of Early Carboniferous age with the structure of ***. Another interpretation, that L. carbonaria is a chaetetid, is discounted because it lacks calicles and is very different in structure from chaetetids. We conclude that L. carbonaria is a stromatoporoid. Becau

关键词： Stromatoporoids Holkerian Viséan Carboniferous Rugosa Labechia carbonaria Labechia conferta

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Zircon U-Pb-Hf constraints from Gongga Shan granites on young crustal melting in eastern Tibet

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Geoscience Frontiers 2019年第3期10卷 885-894页

作者： Nick M.W.Roberts Michael P.Searle NERC Isotope Geosciences Laboratory British Geological Survey Environment Science Centre Department of Earth Sciences University of Oxford

The Gongga Shan batholith is a complex granitoid batholith on the eastern margin of the Tibetan Plateau with a long history of magmatism spanning from the Triassic to the Pliocene. Late Miocene-Pliocene units are the youngest exposed crustal melts within the entire Asian plate of the Tibetan ***, we present in-situ zircon Hf isotope constraints on their magmatic source, to aid the understanding of how these young melts were formed and how they were exhumed to the surface. Hf isotope signatures of Eocene to Pliocene zircon rims(ε_(Hf)(t)=-4 to +4), interpreted to have grown during localised crustal melting, are indicative of melting of a Neoproterozoic source region, equivalent to the nearby exposed Kangding Complex. Therefore, we suggest that Neoproterozoic crust underlies this region of the Songpan-Ganze terrane, and sourced the intrusive granites that form the Gongga Shan batholith. Localised young melting of Neoproterozoic lower or middle crust requires localised melt-fertile lithologies. We suggest that such melts may be equivalent to seismic and magnetotelluric low-velocity and high-conductivity zones or "bright spots" imaged across much of the Tibetan Plateau. The lack of widespread exposed melts this age is due either to the lack of melt-fertile rocks in the middle crust, the very low erosion level of the Tibetan plateau, or to a lack of mechanism for exhuming such melts. For Gongga Shan, where some melting is younger than nearby thermochronological ages of low temperature cooling, the exact process and timing of exhumation remains enigmatic, but their location away from the Xianshuihe fault precludes the fault acting as a conduit for the young melts. We suggest that underthrusting of dry granulites of the lower Indian crust(Archaean shield) this far northeast is a plausible mechanism to explain the uplift and exhumation of the eastern Tibetan Plateau.

关键词： Tibet Himalaya Hf isotopes Zircon Crustal melting

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New Partnerships for Co-delivery of the 2030 Agenda for Sustainable Development

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International Journal of Disaster Risk Science 2020年第5期11卷 680-685页

作者： Adrian Bucher Andrew Collins Ben Heaven Taylor David Pan Emma Visman James Norris Joel CGill John Rees Mark Felling Marta Tufet Bayona Sonia Cassidy Virginia Murray UK Collaborative on Development Research London NW12BEUK Disaster and Development Network(DDN) Department of Geography and Environmental SciencesNorthumbria UniversityNewcastle-upon-Tyne NE18STUK Evidence Aid AbingdonOxfordshire OX135DBUK Global Health Medical Research Council SwindonSwindon SN21FLUK Department of Geography King's College LondonLondon WC2B 4BGUK VNG Consulting Limited Kent TN248DHUK Ordnance survey Southampton SO16 OASUK Global Geoscience British Geological SurveyKeyworth NG125GGUK Earth Hazards and Observatories British Geological SurveyNottingham NG123ENUK ALLFED LondonUK Global Disaster Risk Reduction Public Health EnglandLondon SE18UGUK

Partnerships have become a comer stone of contemporary research that recognizes working across disciplines and co-production with intended users as essential to enabling sustainable ***,research that addresses sustainable development challenges brings an urgent need to reflect on the ways that partnerships are supported,and for the disaster risk management and resilience communities,efforts to support realization of the wider 2030 Agenda for sustainable development bring particular *** November 2019,the UK Disasters Research Group(DRG)brought together a number of key stakeholders focused on disaster risk,resilience,and sustainability research relevant to Official DevelopmeAssistance to consider how fit for purpose existing partnership models are for the pace of change required to deliver the priorities of the wider 2030 *** were invited to discuss how research partnerships across three levels(individual and project-based;national and institutional;and international)could be improved based on elements that facilitate robust partnerships and learning from aspects that hinder *** the discussions,participanls emphasized the importance of effective communication mechanisms in building partnerships,co-designing projects,and establishing shared *** approaches to addressing equitable partnerships and funding more substantive timelines will be key to responding to the challenges of the 2030 Agenda.

关键词： 2030 Agenda for sustainable development Disaster risk reduction DRG Inter national development Partnerships Research fun ding

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The Jinshajiang suture zone: tectono-stratigraphic subdivision and revision of age

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Science China Earth Sciences 2000年第1期43卷 10-22页

作者：汪啸风 lan Metcalfe 简平何龙清王传尚 LYichang Institute of Geology and Mineral Resources Chinese Academy of Geological Sciences Yichang 443003China Asia Centre University of New England Australia

Integrated study of rock assemblage, tectonic setting, geochemical feature, fossil contained and isotopic geochronology on the metamorphic mixed bodies, exposed in the Jinshajiang suture zone, suggests that one informal lithostratigraphic unit, the Eaqing Complex, and three tectono-stratigraphic units, the Jinshajiang ophiolitic melange, the Gajinxueshan Group and the Zhongxinrong Group, can be recognized there. It is first pointed out that the redefined Eaqing Complex might represent the Meso- to Neo-Proterozoic remnant metamorphic basement or mi-crocontinental fragment in the Jinshajiang area. The original rocks of it should be older than (1627 ±192) Ma based on the geochronological study. The zircon U-Pb age of plagiogranites within the Jinshajiang ophiolitic assemblage is dated for the first time at (294 ± 3) Ma and (340 ± 3) Ma respectively. The Jinshajiang ophiolite is approximately equivalent to the Ailaoshan ophiolite in the formation age, covering the interval from the Late Devonian to the Carboniferous. Dating of U-Pb age from basalt interbeds indicates that the redefined Gajinxueshan Group and Zhongxinrong Group may be considered Carboniferous to Permian and latest Permian to Middle Triassic in age. In geotectonic terms the Jinshajiang suture zone is thought to be a back-arc basin in the eastern margin of the Paleo-Tethys. This back-arc basin started in the Late Devonian, and formed in the Devonian-Carboniferous. The collision event around the Permian/Triassic boundary to the Middle Triassic led to the closure of the back-arc basin and formation of suture.

关键词： Jinshajiang suture zone complex ophiolitic melange Paleo-Tethys.

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Carbon capture and storage,geomechanics and induced seismic activity

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Journal of Rock Mechanics and Geotechnical Engineering 2016年第6期8卷 928-935页

作者： James P.Verdon Anna L.Stork School of Earth Sciences University of Bristol

Injection of large volumes of carbon dioxide(CO) for the purposes of greenhouse-gas emissions reduction has the potential to induce *** of proposed projects must therefore take steps to reduce the risks posed by this induced *** this paper,we examine the causes of injection-induced seismicity(IIS),and how it should be monitored and modelled,and thereby *** US case studies are found where fluids are injected into layers that are in close proximity to crystalline basement *** investigate this issue further by comparing injection and seismicity in two areas where oilfield wastewater is injected in significant volumes:Oklahoma,where fluids are injected into a basal layer,and Saskatchewan,where fluids are injected into a much shallower *** suggest that the different induced seismicity responses in these two areas are at least in part due to these different injection *** go on to outline two different approaches for modelling IIS:a statistics based approach and a physical,numerical modelling based *** modelling types have advantages and disadvantages,but share a need to be calibrated with good quality seismic monitoring data if they are to be used with any degree of *** therefore encourage the use of seismic monitoring networks at all future carbon capture and storage(CCS) sites.

关键词： Carbon capture and storage(CCS) Induced seismicity Geomechanics

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Temporal and spatial distribution of microfractures in granites of different structures under triaxial compression and its significance in seismology

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Chinese Science Bulletin 1999年第14期44卷 1321-1325页

作者： Liqiang Liu Shengli Ma Jin Ma Xinglin Lei K. Kusunose O. Nishizawa L. Jouniaux China Seismol Bur Inst Geol Beijing 100029 Peoples R China Geol survey Japan Tsukuba Ibaraki 305 Japan Ecole Normale Super Geol Lab F-75231 Paris France CNRS URA 1316 Paris France

The temporal and spatial distribution of microfracturing activity in two kinds of granite under triaxial compression has been studied by using a new acoustic emission system. For Inada granite, there is no clear clustering of acoustic emission events in time and space, thus it is difficult to exactly deduce the time and position of the major fracturing. While for Mayet granite,acoustic emission events are clustered in time and space, so the time and position of the major fracturing can be exactly predicted according to microfracturing process. Such a difference may result from the difference in deformation mode caused by different rock structures.

关键词： rock structure acoustic emission microfracturing temporal and spatial distribution seismicity.

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A machine learning approach to tungsten prospectivity modelling using knowledge-driven feature extraction and model confidenc

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Geoscience Frontiers 2020年第6期11卷 2067-2081页

作者： Christopher M.Yeomans Robin K.Shail Stephen Grebby Vesa Nykanen Maarit Middleton Paul A.J.Lusty Camborne School of Mines College of EngineeringMathematics and Physical SciencesUniversity of ExeterPenryn CampusPenrynCornwallTR109FEUK british geological survey Environmental Science CentreKeyworthNottinghamshireNG125GGUK University of Nottingham Nottingham Geospatial InstituteInnovation ParkNottinghamNG72TUUK geological survey of Finland P.O.Box 77FI-96101RovaniemiFinland

Novel mineral prospectivity modelling presented here applies knowledge-driven feature extraction to a datadriven machine learning approach for tungsten *** method emphasises the importance of appropriate model evaluation and develops a new Confidence Metric to generate spatially refined and robust exploration *** data-driven Random ForestTM algorithm is employed to model tungsten mineralisation in SW England using a range of geological,geochemical and geophysical evidence layers which include a depth to granite evidence *** models are presented,one using standardised input variables and a second that implements fuzzy set theory as part of an augmented feature extraction *** use of fuzzy data transformations mean feature extraction can incorporate some user-knowledge about the mineralisation into the *** typically subjective approach is guided using the Receiver Operating Characteristics(ROC)curve tool where transformed data are compared to known training *** modelling is conducted using 34 known true positive samples with 10 sets of randomly generated true negative samples to test the random effect on the *** two models have similar accuracy but show different spatial distributions when identifying highly prospective *** analysis shows that the fuzzy-transformed model is a better discriminator and highlights three areas of high prospectivity that were not previously *** Confidence Metric,derived from model variance,is employed to further evaluate the *** new metric is useful for refining exploration targets and highlighting the most robust areas for follow-up *** fuzzy-transformed model is shown to contain larger areas of high model confidence compared to the model using standardised ***,legacy mining data,from drilling reports and mine descriptions,is used to further validate the fuzzy-transformed model and gauge the depth of potential *** of m

关键词： Machine learning Mineral prospectivity modelling Mineral exploration Random ForestTM Tungsten SW England

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Regional trends and petrologic factors inhibit global interpretations of zircon trace element compositions

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Geoscience Frontiers 2024年第5期15卷 300-307页

作者： Nick M.W.Roberts Christopher J.Spencer Stephen Puetz C.Brenhin Keller Simon Tapster Geochronology and Tracers Facility British Geological SurveyNottingham NG125GGUK Department of geological Sciences and geological Engineering Queen’s UniversityKingstonOntarioCanada 475 Atkinson Dr Suite 704HonoluluHI 96814USA Department of Earth Sciences Dartmouth CollegeHanoverNew HamphireUSA

The trace element composition of zircon reveals information about the melt that they are derived from,as such,detrital zircon trace element compositions can be used to interrogate melt compositions,and thus the evolution of the continental crust in time and ***,we present a global database of detrital zircon compositions and use it to test whether average global trends for five common petrogenetic proxies truly represent secular changes in continental *** demonstrate that the secular trend is broadly comparable across continental regions for Ti-in-zircon temperatures,but for other trace element ratios interrogated,secular trends are highly variable between continental *** trace element ratios result from multiple petrologic variables,we argue that these petrogenetic proxies can be overinterpreted if projected to global geologic *** particular,we caution against the interpretation of crustal thickness from trace elements in zircon,and we argue that our results negate current hypotheses concerning secular changes in crustal thickness.

关键词： Detrital zircon Trace elements Secular change Eu anomaly Crustal thickness

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Converted-wave Seismology in Anisotropic Media Revisited, Part I： Basic Theory

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Applied Geophysics 2005年第1期2卷 26-40,i001-i002页

作者： XiangyangLi JianxinYuan britishgeologicalsurvey WestMainsRoadEdinburghEH93LAUK Formerlyatbritishgeologicalsurvey nowatPGSInc. 10550RichmondAvenueSuite300HoustonTX77042USA

We have developed new basic theories for calculating the conversion point and the travel time of the P-SV converted wave (C-wave) in anisotropic, inhomogeneous media. This enables the use of conventional procedures such as semblance analysis, Dix-type model building and Kirchhoff summation, to implement anisotropic processing, and makes anisotropic processing affordable. Here we present these new developments in two parts: basic theory and application to velocity analysis and parameter estimation. This part deals with the basic theory, including both conversion-point calculation and moveout *** equations for calculating the PS-wave (C-wave) conversion point in layered media with vertical transverse isotropy (VTI) are strictly limited to offsets about half the reflector depth (an offset-depth ratio, x/z, of 0.5), and those for calculating the C-wave traveltimes are limited to offsets equal to the reflector depth (x/z=1.0). In contrast, the new equations for calculating the conversion-point extend into offsets about three-times the reflector depth (x/z=3.0), those for calculating the C-wave traveltimes extend into offsets twice the reflector depth (x/z=2.0). With the improved accuracy, the equations can help in C-wave data processing and parameter estimation in anisotropic, inhomogeneous media.

关键词：反向波各向异性介质地震波模型传播速度数学模型

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Converted-wave Seismology in Anisotropic Media Revisited, Part II: Application to Parameter Estimation

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Applied Geophysics 2005年第3期2卷 153-167,i0001,F0003页

作者：李向阳 Yuan Jianxin british geological survey West Mains RoadEdinburgh EH9 3LAUK PGS Inc. 10550 Richmond AvenueSuite 300HoustonTX 77042USA

In transversely isotropic media with a vertical symmetry axis （VTI）, the converted-wave （C-wave） moveout over intermediate-to-far offsets is determined by four parameters. These are the C-wave stacking velocity Vc2 , the vertical and effective velocity ratios γ0 and γeff, and the anisotropic parameter χeff. We refer to the four parameters as the C-wave stacking velocity model. The purpose of C-wave velocity analysis is to determine this stacking velocity model. The C-wave stacking velocity model Vc2, γ0, γeff, and χeff can be determined from P-and C-wave reflection moveout data. However, error propagation is a severe problem in C-wave reflection-moveout inversion. The current short-spread stacking velocity as deduced from hyperbolic moveout does not provide sufficient accuracy to yield meaningful inverted values for the anisotropic parameters. The non-hyperbolic moveout over intermediate-offsets （x/z from 1.0 to 1.5） is no longer negligible and can be quantified using a background γ. Non-hyperbolic analysis with a γ correction over the intermediate offsets can yield Vc2 with errors less than 1% for noise free data. The procedure is very robust, allowing initial guesses of γ with up to 20% errors. It is also applicable for vertically inhomogeneous anisotropic media. This improved accuracy makes it possible to estimate anisotropic parameters using 4C seismic data. Two practical work flows are presented for this purpose： the double-scanning flow and the single-scanning flow. Applications to synthetic and real data show that the two flows yield results with similar accuracy but the single-scanning flow is more efficient than the double-scanning flow.

关键词： converted wave anisotropic moveout velocity and seismology

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