Recent shallow marine ostracods from high latitudes: implications for late Pliocene and Quaternary palaeoclimatology   总被引：2，自引：0，他引：2  

ELISABETH M. BROUWERS  THOMAS M. CRONIN  DAVID J. HORNE  ALAN R. LORD 《Boreas: An International Journal of Quaternary Research》2000,29(2):127-142

New information about modern high-latitude marine ostracod faunas and about their occurrence in late Pliocene and Quaternary sequences promotes the application of these microfossils to palaeoenvironmental, palaeobiogeographical and palaeoclimatological problems. Five poorly known species (Cluthia cluthae, Finmarchinella logani, Roundstonia globulifera, Roundstonia macchesneyi and Semicytherura complanata) from North Atlantic, North Pacific and Arctic areas are confirmed as extant and are used to demonstrate the potential of marine ostracods as tools for palaeoclimate studies. The genus Bonnyannella Athersuch, 1982 is shown to be a junior synonym of Roundstonia Neale, 1973.  相似文献   

Mothballs?     

M. J. BENTON  C.J. CLEAL  D. EDWARDS  L.B. HALSTEAD  S.I. JUSYPIW  K.A. KERMACK  M.A. TAYLOR  B.A. THOMAS  W.A. WIMBLEDON  M.A. ROWLANDS  T.S. WESTOLL  FRS 《Geology Today》1985,1(5):135-136

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Evidence of the final drainage of the Baltic Ice Lake and the brackish phase of the Yoldia Sea in glacial varves from the Baltic Sea     

THOMAS ANDRÉN  GREGER LINDEBERG  ELINOR ANDRÉN 《Boreas: An International Journal of Quaternary Research》2002,31(3):226-238

A clay-varve chronology based on 14 cross-correlated varve graphs from the Baltic Sea and a mean varve thickness curve has been constructed. This chronology is correlated with the Swedish Time Scale and covers the time span 11530 to 10250 varve years BP. Two cores have been analysed for grain size, chemistry, content of diatoms and changes in colour by digital colour analysis. The final drainage of the Baltic Ice Lake is dated to c . 10800 varve years BP and registered in the cores analysed as a decrease in the content of clay. This event can be correlated with atmospheric Δ14 C content and might have resulted in an increase in these values recorded between 11565 and 11545 years BP. The results of the correlation between the varve chronology from the Baltic Sea, the Greenland GRIP ice core and the atmospheric Δ14 C record indicate that c . 760 years are missing in the Swedish Time Scale in the part younger than c. 10250 varve years BP. A change in colour from a brownish to grey varved glacial clay recorded c . 10770 varve years BP is found to be the result of oxygen deficiency due to an increase in the rate of sedimentation in the early Preboreal. The first brackish influence is recorded c . 10540 varve years BP in the northwestern Baltic Sea and some 90 years later in the eastern Gotland Basin.  相似文献   

Seasonal variations of nitric oxide flux from agricultural soils in the Southeast United States     

VINEY P. ANEJA  WAYNE P. ROBARGE  LEE J. SULLIVAN  THOMAS C. MOORE  THOMAS E. PIERCE  CHRIS GERON  BRUCE GAY 《Tellus. Series B, Chemical and physical meteorology》1996,48(5):626-640

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CO and CO₂ isotopic composition in Spitsbergen during the 1995 ARCTOC campaign     

THOMAS RÖCKMANN  CARL A. M. BRENNINKMEIJER 《Tellus. Series B, Chemical and physical meteorology》1997,49(5):455-465

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Use of a two-component exponential distribution in partial duration modelling of hydrological droughts in Zimbabwean rivers     

THOMAS R. KJELDSEN  ALLAN LUNDORF  DAN ROSBJERG 《水文科学杂志》2013,58(2):285-298

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Données isotopiques (8786/Sr) et changements hydrologiques depuis 15 000 ans sur l'Altiplano andin     

ANNE COUDRAIN  MICHEL LOUBET  THOMAS CONDOM  AMAL TALBI  PIERRE RIBSTEIN  BERNARD POUYAUD 《水文科学杂志》2013,58(2):293-306

Abstract

In catchments characterized by spatially varying hydrological processes and responses, the optimal parameter values or regions of attraction in parameter space may differ with location-specific characteristics and dominating processes. This paper evaluates the value of semi-distributed calibration parameters for large-scale streamflow simulation using the spatially distributed LISFLOOD model. We employ the Shuffled Complex Evolution Metropolis (SCEM-UA) global optimization algorithm to infer the calibration parameters using daily discharge observations. The resulting posterior parameter distribution reflects the uncertainty about the model parameters and forms the basis for making probabilistic flow predictions. We assess the value of semi-distributing the calibration parameters by comparing three different calibration strategies. In the first calibration strategy uniform values over the entire area of interest are adopted for the unknown parameters, which are calibrated against discharge observations at the downstream outlet of the catchment. In the second calibration strategy the parameters are also uniformly distributed, but they are calibrated against observed discharges at the catchment outlet and at internal stations. In the third strategy a semi-distributed approach is adopted. Starting from upstream, parameters in each subcatchment are calibrated against the observed discharges at the outlet of the subcatchment. In order not to propagate upstream errors in the calibration process, observed discharges at upstream catchment outlets are used as inflow when calibrating downstream subcatchments. As an illustrative example, we demonstrate the methodology for a part of the Morava catchment, covering an area of approximately 10 000 km². The calibration results reveal that the additional value of the internal discharge stations is limited when applying a lumped parameter approach. Moving from a lumped to a semi-distributed parameter approach: (i) improves the accuracy of the flow predictions, especially in the upstream subcatchments; and (ii) results in a more correct representation of flow prediction uncertainty. The results show the clear need to distribute the calibration parameters, especially in large catchments characterized by spatially varying hydrological processes and responses.  相似文献   

B.—U. N. E. S. C. O.     

F. MORTIER  R. G. THOMAS  N. Q. TRAC 《水文科学杂志》2013,58(1):7-11

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Evaluation of the Holocene environmental changes of the southwest coast, India: A palaeopalynological approach     

B AJAYKUMAR  K SREEDHARAN  MAHESH MOHAN  JOBY PAUL  A P THOMAS  P K K NAIR 《Journal of Earth System Science》2012,121(4):1093-1103

The climatic variability and the influence of temperature and sea level fluctuations on the earth??s surface configuration during the Holocene are being discussed all over the world. The present study evaluates the palaeo-environmental conditions of western coast of India during this epoch through the analysis of pollen grains embedded in a carbonaceous clay formation (? 0.4?C0.6?m) found sandwiched within the palaeodeposit of sand of Meenachil River basin. The carbon dating revealed that the clay formation has an age of 5786 ± 94 ¹⁴C yr BP, while the embedded wood samples have the age varying in between 2888 ± 78 and 5780 ± 95 ¹⁴C yr BP. The overall analysis suggests that the southwestern margin of India had experienced high intensity rainfall during the earlier part of the Atlantic chronozone due to then strengthened Asiatic monsoon, while water stagnation and hydrological modifications were observed during the later part. The dominance of weeds and lesser number of tree elements suggested a drier climate during the end of the Atlantic period. Besides, the morphometric rearrangement of the Meenachil River contemporaneous to the geomorphological modifications of the southwestern coast of India shall be classified into three categories: (1) Pre-Vembanad Lake formation, (2) Contemporaneous to lake formation and (3) Post-Lake formation.  相似文献   

Geochemistry of Holocene salt marsh and tidal flat sediments on a barrier island in the southern North Sea (Langeoog,North‐west Germany)     

KERSTIN KOLDITZ  OLAF DELLWIG  JAN BARKOWSKI  RAINER BAHLO  THOMAS LEIPE  HOLGER FREUND  HANS‐JÜRGEN BRUMSACK 《Sedimentology》2012,59(2):337-355

The barrier islands of the southern North Sea were formed during the Holocene sea‐level rise. These islands form part of a highly dynamic environment whose evolution continues today. Subjected to sea‐level changes, tides and storm events, the sedimentary record reflects processes occurring under varying energy conditions. This article presents geochemical, mineralogical and diatom investigations carried out in the salt marsh of the East Frisian barrier island of Langeoog, which is re‐exposed to a rising sea‐level due to de‐embankment. The major aim of this study is to improve the knowledge of the sedimentological and geochemical development of these deposits under the influence of sea‐level rise, with a special focus on the geochemistry and distribution of heavy mineral‐associated elements. Correlation diagrams between FeO, TiO₂ and MnO, as well as ternary plots (Al₂O₃–SiO₂–Zr or TiO₂), clearly indicate the variable appearance of heavy minerals in different lithological facies, comprising marsh soil, mixed and sand flat, and relocated beach sands. A dominating abundance of ilmenite followed by zircon, garnets and some other heavy minerals is evidenced by Scanning Electron Microscope‐Energy Dispersive X‐ray measurements. The data presented here suggests that these geochemical proxies are useful tools for characterizing depositional energy conditions. Increasing depositional energy is evident for the lithological units in the following order: marsh soil, mixed flat, sand flat and relocated beach sand. The energetic conditions during sediment deposition, as well as the sedimentary history, are confirmed by diatom analyses as an additional independent indicator. Depending on source rock composition, the geochemical parameters used in this study may also help to investigate depositional energy regimes of other siliciclastic sedimentary systems.  相似文献