Fen ecosystem responses to water‐level fluctuations during the early and middle Holocene in central Europe: a case study from Wilczków,Poland          下载免费PDF全文

Mateusz Płóciennik  Andrzej Kruk  Jacek Forysiak  Dominik Pawłowski  Kamila Mianowicz  Scott Elias  Ryszard K. Borówka  Marek Kloss  Milena Obremska  Marek Krąpiec  Piotr Kittel  Sławomir Żurek 《Boreas: An International Journal of Quaternary Research》2015,44(4):721-740

This paper presents a palaeoenvironmental reconstruction of the Wilczków fen (central Poland). The fen developed in an inactive valley at the onset of the Holocene (~11 ka BP) and peat accumulation lasted until 5.7 ka BP. Multi‐proxy reconstructions were made on the basis of palaeobotanical, cladoceran, chironomid, beetle and geochemical analyses. A Kohonen self‐organizing map (SOM, unsupervised artificial neural network) of the biotic sequence distinguished four stages of fen history. Stage X₁ (11.0–10.7 ka BP) was relatively wet and cool. Organic matter started to accumulate but the habitat conditions remained unstable. Moss, sedge and fern communities then developed. Sedimentary changes reveal an intensive groundwater supply at that time. Numerous and diverse chironomid and cladoceran subfossils indicate nearly permanent aquatic conditions. During stage Y₁ (10.6–9.2 ka BP) conditions were dry and the upper peat layer desiccated. Cladocera nearly disappeared whereas chironomids were represented by semi‐terrestrial and predatory (Tanypodinae) species. Conditions started to be more reducing. All the remaining samples belonged to the interweaving stages X₂ and Y₂. Stage Y₂ (mostly 9.1–7.3 and 6.0–5.7 ka BP) was also dry but humidity increased towards the top. Oxidizing conditions occurred and the pH became more alkaline, favouring Cladium mariscus. The basin received mostly allochthonous matter input at that time. Stage X₂ (mostly 6.8–6.1 ka BP) was humid and warm. The groundwater supply remained low but there was an increase in precipitation, changing local conditions to ombrotrophic. Species‐rich chironomid and cladoceran communities were associated with temporary pools. Finally, conditions returned to those characteristic of stage Y₂. The presented reconstruction documents long‐term abiotic and biotic changes determined by water supply, including groundwater outflow, which have rarely been detected at a multi‐proxy scale. We show that inactivated valley fens are sensitive to climate‐driven hydrological fluctuations. Kohonen neural networks appear to be a promising method for analysing variability in multi‐proxy data.  相似文献   

Warnstorfia exannulata, an aquatic moss in the Arctic: seasonal growth responses     

Cai-Qing Guo  Ryszard Ochyra  Peng-Cheng Wu  Rodney D. Seppelt  Yi-Feng Yao  Lin-Gen Bian  Su-Ping Li  Cheng-Sen Li 《Climatic change》2013,119(2):407-419

The moss, Warnstorfia exannulata (Schimp.) Loeske, was first reported forming a carpet beside a water pool in Ny-Ålesund (78°56′N), Svalbard in 1959. Fifty years later, in 2008, it was found growing as an aquatic in a pool. The moss is sensitive to seasonal changes and exhibits a pattern of seasonal growth: summer stems with densely arranged leaves and lateral branches, and winter growth with short-leaved stems and no lateral branch. The mean daily increase in stem length is 0.68 mm in summer and 0.07 mm in winter. The longest specimens were up to 8 years old. The growth of the moss reflects closely seasonal temperature and growth conditions. World distribution is discussed and global distribution mapped.  相似文献   

Tithonian–Early Valanginian evolution of deposition along the proto-Caribbean margin of North America recorded in Guaniguanico successions (western Cuba)     

Andrzej Pszczółkowski  Ryszard Myczyński 《Journal of South American Earth Sciences》2010,29(2):225-253

In the Guaniguanico Mountains of western Cuba, the Late Jurassic–Early Cretaceous limestones occur in three stratigraphic successions, which have accumulated along the proto-Caribbean margin of North America. The Late Jurassic subsidence and shallow-water carbonate deposition of the Guaniguanico successions have no counterpart on the northeastern Maya block, but some distant similarities with the southeastern Gulf of Mexico may exist. Four facies types have been distinguished in the Tithonian–Lower Valanginian deposits of the Guaniguanico tectonic units. Drowning of the Late Jurassic carbonate bank of the Sierra de los Organos occurred at the Kimmeridgian/Tithonian boundary. During this boundary interval, sedimentation in the west Cuban area and southwestern margin of the Maya block (Mexico) has evolved in a similar way in response to a major second-order transgression.The Lower Tithonian ammonite assemblages of the Guaniguanico successions indicate, in general, the neritic zone. Presence of juvenile gastropods and lack of adult specimens suggest unfavorable environment for these molluscs, probably related to low oxygenation levels. The Early Tithonian transgressive phase terminated about the lower boundary of the Chitinoidella Zone. The Late Tithonian “regressive” phase is weakly marked, whereas the latest Tithonian–earliest Berriasian strata were deposited during a deepening phase. The latter transgressive phase has ended in the Late Berriasian Oblonga Subzone. We correlate the bioturbated pelagic biomicrites of the Tumbitas Member of the Guasasa Formation with a significant fall of the sea level during the latest Berriasian–Early Valanginian. The average sedimentation rate for the Tumbitas Member biomicrites was about three times faster than for the Berriasian Tumbadero Member limestones. Sedimentation rates for the Tumbitas Member and the Valanginian limestones at the DSDP Site 535 in the southeastern Gulf of Mexico were similar. In the Los Organos succession, the Late Valanginian transgressive interval is associated with radiolarian limestones and black chert interbeds in the lower part of the Pons Formation. In the Southern Rosario succession, the pelagic limestones pass into the radiolarian cherts of the Santa Teresa Formation indicating a proximity of CCD during Late Valanginian–Hauterivian times.  相似文献   

Complex exposure histories for meteorites with “short” exposure ages     

G. F. HERZOG  S. VOGT  A. ALBRECHT  S. XUE  D. FINK  J. KLEIN  R. MIDDLETON  H. W. WEBER  L. SCHULTZ 《Meteoritics & planetary science》1997,32(3):413-422

Abstract— We report measurements of ²⁶Al and ¹⁰Be activities in nine ordinary chondrites and of the light noble gas concentrations and ³⁶Cl and ⁴¹Ca activities in subsets of those meteorites. All but Murray have low ²¹Ne concentrations (<1.0 × 10^?8cm³STP/g) and have previously been used to estimate ²¹Ne production rates. Ladder Creek, Murchison, Sena, and Timochin have inventories of cosmogenic radionuclides that are compatible with a single stage of irradiation and give ²¹Ne production rates that are consistent with the standard L-chondrite value of 0.33 × 10^?8cm³STP/g/Ma. In contrast, Cullison, Guenie, Shaw, and Tsarev experienced complex irradiation histories. They and several other meteorites with low nominal exposure ages also have lower ³He/²¹Ne ratios than expected based on their ²²Ne/²¹Ne ratios. A general association between low ²¹Ne contents and ³He losses suggests that meteorites with short lifetimes often occupy orbits with small perihelia. However, meteorites with low ²¹Ne contents, one-stage exposure histories, and losses of cosmogenic ³He are rare. Possible explanations for the scarcity are (1) statistical, (2) that it is harder for more deeply buried protometeoroids to lose gas in a liberating collision, and (3) that it is harder to insert more deeply buried protometeoroids directly into orbits with small perihelia.  相似文献   

苏鲁超高压变质岩的构造热历史：中国大陆科学钻探工程(CCSD)主孔（MH）和先导孔（PP2）的磷灰石裂变径迹约束     

刘顺生  GLASMACHER Ulrich  许志琴  WEBER Ursul  WAGNER Günther  JONCKHEERE Raymon  殷秀兰 《岩石学报》2009,25(7):1612-1618

本文包括中国大陆科学钻（CCSD）主孔（MH）0~5000m和先导孔（PP2）0~1000m的磷灰石裂变径迹分折结果,先导孔PP2的裂变径迹表观年龄变化范围为79.5±5.1~50.4±6.2Ma,主孔的裂变径迹表观年龄变化范围为98.6±17.0~2.9±2.0Ma,主孔在4200m以下,磷灰石样品中实际上已不存在自发裂变径迹,表明裂变径迹时钟已经“置零”。实验资料表明,裂变径迹表观年龄值随样品深度的增加而逐渐减少,直到一定深度,即达到磷灰石的裂变径迹封闭温度（~120℃）以后,年龄值为零。根据主孔0~2000m和先导孔0~1000m的裂变径迹年龄剖面,作为一级近似,计算出超高压变质岩体在90~30Ma期间,平均隆升速度为~35m/Ma。对主孔测定了9个样品的约束径迹（Confined track）长度,样品约束径迹平均长度的变化范围约为13.1~7.4μm,总的变化趋势是：约束径迹平均长度随样品深度的增加而逐渐减少。样品的约束径迹长度分布都具有双峰型特征。根据裂变径迹年龄和约束径迹长度的资料,应用计算机模拟得到了样品的时间-温度（t-T）轨迹。结果表明,岩体从早白垩世（~120Ma）快速冷却以后,在晚白垩世和始新世又经历了两次加热作用,始新世末岩体所达到的温度大约是80℃,随后岩体则一直上升和缓慢冷却到现今所处的位置。在最后~30Ma岩体的平均隆升速度为~53m/Ma。  相似文献   

Ordovician passive continental margin magmatism in the Central-European Variscides: U–Pb zircon data from the SE part of the Karkonosze-Izera Massif, Sudetes, SW Poland     

Teresa Oberc-Dziedzic  Ryszard Kryza  Ksenia Mochnacka  Alexander Larionov 《International Journal of Earth Sciences》2010,99(1):27-46

Approximately 500-Ma-old orthogneisses are widespread in the eastern part of the Variscan belt and are commonly interpreted to have intruded mica-schist series of assumed Neoproterozoic age. New SHRIMP zircon ages of quartzofeldspathic metavolcanogenic rocks of the mica schist series in the eastern part of the Karkonosze-Izera Massif (SW Poland) indicate that they are late Cambrian/early Ordovician rather than Neoproterozoic in age, based on the zircon age spectra distributed mainly between ca. 500 and 660 Ma (with a few Proterozoic inherited minimum ages of ca. 970 and 1,825 Ma). Younger zircon dates, dispersed between ca. 412 and 464 Ma, are interpreted as a result of Pb-loss likely caused by subsequent metamorphism. Consequently, the felsic metavolcanogenic rocks appear to be roughly contemporaneous with the intrusion of ca. 500-Ma-old orthogneiss protoliths (with the pooled concordia age of 487 ± 8 Ma interpreted as the best approximation of the protolith intrusive age). Field relationships, petrological and geochemical features of the felsic and mafic rocks studied support a model in which the accompanying mica schist series are not the original country rocks to the ca. 500 Ma granite intrusions, and indicate that their recent close proximity is the result of tectonic juxtaposition. However, both the mica schists enclosing the bimodal metavolcanic rocks, and the orthogneisses, are interpreted to represent a Cambro-Ordovician passive continental margin sequence being part of the Saxothuringian domain. They are tectonically overlain to the east by HP/T metamorphic units, comprising MORB-type metaigneous rocks, and delineating a tectonic suture separating the Saxothuringian block in the west from an assumed continental block (Tepla-Barrandian) to the south-east.  相似文献   

Finite element modelling of thick plates on two‐parameter elastic foundation     

Ryszard Buczkowski  Witold Torbacki 《国际地质力学数值与分析法杂志》2001,25(14):1409-1427

This paper is intended to give some information about how to build a model necessary for bending analysis of rectangular and circular plates resting on a two‐parameter elastic foundation, subjected to combined loading and permitting various types of boundary conditions. The formulation of the problem takes into account the shear deformation of the plate and the surrounding interaction effect outside the plate. The numerical model based on an 18‐node zero‐thickness isoparametric interface element interacting with a thick Reissner–Mindlin plate element with three degrees of freedom at each of the nine nodes, which enforce C⁰ continuity requirements for the displacements and rotations of the midsurface, is proposed. Stiffness matrices of a special interface element are superimposed on the global stiffness matrix to represent the stiffening elastic foundation under and beyond the plate. Some numerical examples are given to illustrate the advantages of the method presented. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

CLIMATE CHANGE VULNERABILITY AND RESPONSE STRATEGIES FOR THE COASTAL ZONE OF POLAND     

Ryszard B. Zeidler 《Climatic change》1997,36(1-2):151-173

Four accelerated sea level rise scenarios, 30 and 100 cm by the year 2100, and 10 and 30 cm by the year 2030, have been assumed as boundary conditions (along with some wind climate changes) for the entire Polish coast, under two recent programmes completed in 1992 and 1995. Three adaptation strategies, i.e., retreat, limited protection and full protection have been adopted and compared in physical and socio-economic terms. Over 2,200 km² and 230,000 people are found vulnerable in the most severe case of 100-cm rise by 2100. The total cost of land at loss in that case is estimated at nearly 30 USD billion (plus some 18 USD billion at risk of flooding), while the cost of full protection reaches 6 USD billion. Particular features of vulnerability and adaptation schemes have been examined as well, including specific sites and the effects of not only sea level rise but also other climate change factors, and interactions with other climate change studies in Poland. Planning of coastal zone management facing climate change can be facilitated by the use of a GIS-supported coastal information and analysis system. An example of the application of such a system for a selected Polish coastal site is shown to illustrate the most recent smaller-scale research activities undertaken in the wake of the overall assessment of the vulnerability to climate change for the entire Polish coastal zone.  相似文献   

HYDRAULIC ANALYSES FOR A NEW BRIDGE OVER THE PARANA RIVER, ARGENTINA     

Andrés RODRIGUEZ  Daniel Farías  Héctor R.BRAVO  Edgar Castelló 《国际泥沙研究》2003,18(2)

1 INTRODUCTION The Parana River in South America ranks as the sixth largest in the world in terms of average discharge (22 x 103 m3/s according to Schumm and Winkley, 1994), and its Argentinean reach stretches from Puerto Iguazu on the north to the Rio de la Plata estuary in the south (Fig. 1). Its estimated average suspended load, bed load, and total load are 23 x 106, 2.2 x 106, and 25.2 x 106 metric tons per year, respectively (Paoli and Schreider, 2001.) The economic developmen…  相似文献   

世界大洋的矿物资源-21世纪全球经济的重要性   总被引：1，自引：0，他引：1  

崔汝勇 《海洋地质前沿》2002,18(2):22-26

1　世界矿物资源及开发程度在过去的 50年中 ,随着人类对矿物资源的需求和美国市场上金属价格的不断上涨 ,在人类文明的发展中矿物资源和能源的重要性越来越明显。大部分已知的和已勘探的资源 ,在不久的将来将逐渐消失。然而 ,不断增加的世界人口将消耗越来越多的从陆地富矿中获取的资源 ;因此 ,资源枯竭的情况必将出现。过量的开采已导致高品位矿床的枯竭 ,这一方面激起了对陆地低品位矿床的兴趣 ,另一方面也激发了对资源循环利用和从其它来源获取资源的兴趣。进入 2 1世纪 ,矿物资源利用的现代标准是什么以及矿物资源的全球潜力有多大是人…  相似文献