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1.
Inna Safonova 《地学前缘(英文版)》2014,5(4):537-552
The paper reviews previous and recently obtained geological, stratigraphic and geochronological data on the Russian-Kazakh Altai orogen, which is located in the western Central Asian Orogenic Belt （CAOB）, between the Kazakhstan and Siberian continental blocks. The Russian-Kazakh Altai is a typical Pacific-type orogen, which represents a collage of oceanic, accretionary, fore-arc, island-arc and continental margin terranes of different ages separated by strike-slip faults and thrusts. Evidence for this comes from key indicative rock associations, such as boninite- and turbidite （graywacke）-bearing volcanogenic-sedimentary units, accreted pelagic chert, oceanic islands and plateaus, MORB-OIB-protolith blueschists. The three major tectonic domains of the Russian-Kazakh Altai are： （1） Altai-Mongolian terrane （AMT）; （2） subduction-accretionary （Rudny Altai, Gorny Altai） and collisional （Kalba-Narym） terranes; （3） Kurai, Charysh-Terekta, North-East, Irtysh and Char suture-shear zones （SSZ）. The evolution of this orogen proceeded in five major stages： （i） late Neoproterozoic-early Paleozoic subduction-accretion in the Paleo-Asian Ocean; （ii） Ordovician-Silurian passive margin; （iii） Devonian-Carboniferous active margin and collision of AMT with the Siberian conti- nent; （iv） late Paleozoic closure of the PAO and coeval collisional magmatism; （v） Mesozoic post-collisional deformation and anarogenic magmatism, which created the modern structural collage of the Russian- Kazakh Altai orogen. The major still unsolved problem of Altai geology is origin of the Altai-Mongolian terrane （continental versus active margin）, age of Altai basement, proportion of juvenile and recycled crust and origin of the middle Paleozoic units of the Gorny Altai and Rudny Altai terranes. 相似文献
2.
Parameter estimation for basin-scale ecosystem-linked population models of large pelagic predators: Application to skipjack tuna 总被引：2，自引：1，他引：1
A Spatial Ecosystem and Population Dynamic Model (SEAPODYM) is used in a data assimilation study aiming to estimate model parameters that describe dynamics of Pacific skipjack tuna population on ocean-based scale. The model based on advection–diffusion–reaction equations explicitly predicts spatial dynamics of large pelagic predators, while taking into account data on several mid-trophic level components, oceanic primary productivity and physical environment. In order to improve its quantitative ability, the model was parameterized through assimilation with commercial fisheries data, and optimization was carried out using maximum likelihood estimation approach. To address the optimization task we implemented an adjoint technique to obtain an exact, analytical evaluation of the likelihood gradient. We conducted a series of computer experiments in order to (i) determine model sensitivity with respect to variable parameters and, hence, investigate their observability; (ii) estimate observable parameters and their errors; and (iii) justify the reliability of the computed solution. Parameters describing recruitment, movement, habitat preferences, natural and fishing mortality of skipjack population were analysed and estimated. Results of the study suggest that SEAPODYM with achieved parameterization scheme can help to investigate the impact of fishing under various management scenarios, and also conduct forecasts of a given species stock and spatial dynamics in a context of environmental and climate changes. 相似文献
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4.
Modelling the impact of climate change on Pacific skipjack tuna population and fisheries 总被引：2，自引：0，他引：2
Patrick Lehodey Inna Senina Beatriz Calmettes John Hampton Simon Nicol 《Climatic change》2013,119(1):95-109
IPCC-type climate models have produced simulations of the oceanic environment that can be used to drive models of upper trophic levels to explore the impact of climate change on marine resources. We use the Spatial Ecosystem And Population Dynamics Model (SEAPODYM) to investigate the potential impact of Climate change under IPCC A2 scenario on Pacific skipjack tuna (Katsuwonus pelamis). IPCC-type models are still coarse in resolution and can produce significant anomalies, e.g., in water temperature. These limitations have direct and strong effects when modeling the dynamics of marine species. Therefore, parameter estimation experiments based on assimilation of historical fishing data are necessary to calibrate the model to these conditions before exploring the future scenarios. A new simulation based on corrected temperature fields of the A2 simulation from one climate model (IPSL-CM4) is presented. The corrected fields led to a new parameterization close to the one achieved with more realistic environment from an ocean reanalysis and satellite-derived primary production. Projected changes in skipjack population under simple fishing effort scenarios are presented. The skipjack catch and biomass is predicted to slightly increase in the Western Central Pacific Ocean until 2050 then the biomass stabilizes and starts to decrease after 2060 while the catch reaches a plateau. Both feeding and spawning habitat become progressively more favourable in the eastern Pacific Ocean and also extend to higher latitudes, while the western equatorial warm pool is predicted to become less favorable for skipjack spawning. 相似文献
5.
On Conditions of Phytoplankton Blooms in the Coastal Waters of the North-Western East/Japan Sea 总被引：1，自引：0，他引：1
Seasonal changes of abundance of the main phytoplankton groups of species (diatoms, dinoflagellates, chrysophytes, small flagellates
and cryptophytes) and a set of environmental parameters were investigated in coastal and preestuarine waters of Peter the
Great Bay (East/Japan Sea) in May-October of 1998 and 1999. Three periods of mass development were revealed: spring, summer
and autumn blooms, with successive change of species. The conditions favourable for each group of species were determined.
Driving mechanisms of the succession include nutrients transport through seasonal pycnocline by turbulent mixing, terrestrial
nutrients supply by monsoon floods, nutrients supply by upwellings, and light control by the thickness of upper mixed layer.
Summer succession could be explained by a simple SST-MLD diagram similar to Pingree S-kh diagram with sea surface temperature
as indicator of stratification (S) and mixed layer depth as indicator of light availability (kh). 相似文献
6.
Three observational data sets are used to construct a continuous record (1850-2001) of April ice edge position in the Barents Sea: two sets of Norwegian ice charts (one from 1850 to 1949 and the other from 1966 to 2001) and Soviet aircraft reconnaissance ice extent charts from 1950 to 1966. The 152-year April ice extent series is subdivided into three sub-periods: 1850-1899, 1900-1949 and 1950-2001. For each of these study sub-periods, a mean April ice edge and a set of anomalies (differences in position between a given April and the mean April ice edge) are computed. The calculations show the mean ice edge position retreated north-eastward over the 152-year period, with the greater retreat seen in the changes from the 1850-1899 sub-period to the 1900-1949 sub-period. The distribution of the standard deviation of the ice edge anomaly over the linear distance along the mean ice edge shows no substantial difference between any of the three periods of the study. Within each study period, the maximum variation is observed in the sector bounded by the 25°E and 49° E meridians, which covers the main pathway of the warmer water flow from the Norwegian Sea. 相似文献
7.
The paper presents a rigorously derived analytical method to describe and interpret the low-magnitude earthquakes caused by injection of the borehole fluids into surrounding porous reservoirs. Microseismicity is induced due to changes in the pore pressure, which, in turn, is influenced mainly by the low-frequency slow Biot (P2) wave. The classical Biot model is used to obtain the distribution of pore pressure in a reservoir. The constructed solution to the Biot system of equations and the spatio-temporal cloud of microseismic events allow one to assess the critical value of the pore pressure, sufficient for the generation of a microearthquake, and the values of hydromechanical parameters (e.g. permeability) of a saturated porous rock. 相似文献
8.
We present a compilation of published data(field,petrography,ages and geochemistry)from 73 ophiolitic complexes of the Central Asian Orogenic Belt.The ophiolitic complexes,ranging in age from Neoproterozoic to Triassic.have been geochemically classified as subduction-related and subductionunrelated categories applying recent,well-established discrimination diagrams.The subductionunrelated category is further subdivided into Mid-Ocean Ridge type(MOR),a common rift-drift stage and Plume type,and the subduction-related category is subdivided into Backarc(BA),Forearc(FA).Backarc to Forearc(BA-FA)and Volcanic Arc(VA)types.The four subduction-related types define highly different geochemical features,with the BA and FA types defining end members showing subduction influence of 10%-100%and 90%-100%subduction influence,respectively,and the two other types(BAFA and VA)define values between the two end members.The subduction-related category comprises79%of the examined ophiolites,of which the BA type ophiolites is by far the dominant group,followed by the BA-FA type,and with FA and VA types as subordinate groups.The Neoproterozoic and Ordovician complexes exhibit the highest,whereas those of Silurian age exhibit the lowest subduction-influence.Of the remaining 21% subduction-unrelated ophiolites,the MOR type dominates.Both the subductionrelated and subduction-unrelated types,in particular the latter,are commonly associated with alkaline basalts taken to represent ocean island magmatism.Harzburgite,dunite,gabbro and basalt are the common lithologies in all ophiolite types,whereas the BA-FA,FA and VA types generally contain intermediate to felsic rocks,and in the FA type boninites occur.The subduction-related ophiolites types generally show low metamorphic grade,whereas greenschist.amphibolite and blueschist grades occur in the subduction-unrelated and BA types.The highly different subduction contribution(from 0 to 100% in the MOR and FA,respectively),attest to variable dips of the subducting slab,as well as variable flux of subduction-related elements into the mantle above subducting slabs,from where the ophiolite magmas got their geochemical fingerprints.As most MOR ophiolites get subducted to the deep mantle,the subduction-related ophiolites have become a dominant ophiolitic type on Earth's surface through all times supporting the idea about the early start of Plate Tectonics. 相似文献
9.
An assessment of the potential and impacts of winter water banking in the Sokh aquifer, Central Asia
The dynamics of artificial recharge of winter surface flows coupled with increased summer groundwater use for irrigation in the Sokh aquifer (Central Asia) have been investigated. Water release patterns from the giant Toktogul reservoir have changed, as priority is now given to hydropower generation in winter in Kyrgyzstan. Winter flows have increased and summer releases have declined, but the Syr Darya River cannot pass these larger winter flows and the excess is diverted to a natural depression, creating a 40?×?109m3 lake. A water balance study of all 18 aquifers feeding the Fergana Valley indicated the feasibility of winter groundwater recharge in storage created by summer abstraction. This modeling study examines the dynamics of the process in one aquifer over a 5-year period, with four scenarios: the current situation; increased groundwater abstraction of around 625 million (M) m3/year; groundwater abstraction with an artificial recharge of 144 Mm3/year, equivalent to the volume available in low flow years in the Sokh River; and with a larger artificial recharge of 268 Mm3/year, corresponding to high flow availability. Summer surface irrigation diversions can be reduced by up to 350 Mm3 and water table levels can be lowered. 相似文献
10.
Daniel Paul Le Heron Micha M. Buslov Clare Davies Keith Richards Inna Safonova 《Sedimentary Geology》2008,208(1-2):45-60
The Mesozoic stratigraphy in the subsurface of the West Siberian Basin contains prolific hydrocarbon accumulations, and thus the depositional environments of marine and marginal marine Jurassic and Cretaceous age sediments are well-established. However, no information is currently available on strata of equivalent age that crop out along the SE basin margin in the Mariinsk–Krasnoyarsk region, despite the potential of these exposures to supply important information on the sediment supply routes into the main basin. Detailed sedimentological analysis of Jurassic–Cretaceous clastic sediments, in conjunction with palaeo-botanical data, reveals five facies associations that reflect deposition in a range of continental environments. These include sediments that were deposited in braided river systems, which were best developed in the Early Jurassic. These early river systems infilled the relics of a topography that was possibly inherited from earlier Triassic rifting. More mature fluvial land systems evolved in the Mid to Late Jurassic. By the Mid Jurassic, well-defined overbank areas had become established, channel abandonment was commonplace, and mudrocks were deposited on floodplains. Coal deposition occurred in mires, which were subject to periodic incursions by crevasse splay processes. Cretaceous sedimentation saw a renewed influx of sand-grade sediment into the region. It is proposed that landscape evolution throughout the Jurassic was driven simply by peneplanation rather than tectonic processes. By contrast, the influx of sandstones in the Cretaceous is tentatively linked to hinterland rejuvenation/ tectonic uplift, possibly coeval with the growth of large deltaic clinoform complexes of the Neocomian in the basin subsurface. 相似文献