A giant catastrophic mud‐and‐debris flow in the Miocene Makran     

Jean‐Pierre Burg  Daniel Bernoulli  Jeroen Smit  Ashgar Dolati  Abbas Bahroudi 《地学学报》2008,20(3):188-193

We challenge the former interpretation of the ‘sedimentary mélange’ of the Makran accretionary complex as a tectonic mélange diapirically emplaced from below and provide evidence for its sedimentary gravitational emplacement from the north during Tortonian–Messinian times (between 11.8 and 5.8 Ma). It is an olistostrome that includes blocks of ophiolites and oceanic sediments derived from the ‘coloured mélange’ to the north, and reworked chunks of the turbidites on which it rests with an erosional truncation. The chaotic scattering of blocks of any size and lithology and the weak, soft‐sediment deformation of the matrix argue against a tectonic emplacement of the chaotic formation. Its size and internal structure, together with the size of the individual blocks, make the olistostrome a fossil equivalent of the large, gravitationally emplaced debris flows observed along present‐day continental margins and unstable volcanic edifices.  相似文献   

A new flow cytometry method enabling rapid purification of fossil pollen from terrestrial sediments for AMS radiocarbon dating     

RICHARD K. TENNANT  RICHARD T. JONES  FIONA BROCK  CHARLOTTE COOK  CHRIS S. M. TURNEY  JOHN LOVE  ROB LEE 《第四纪科学杂志》2013,28(3):229-236

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Contribution durant des épisodes hydrologiques extrêmes des apports atmosphériques et souterrains en ions majeurs à la qualité des eaux de surface*     

Daniel Cluis  René Langis  Pierre Couture 《大气与海洋》2013,51(3):437-448

Résumé

Le comportement des ions majeurs (Ca⁺², Mg⁺², Na⁺, K⁺, Cl^?, SO₄ ^?2) et de la conductivité en rivière en fonction des épisodes hydrologiques extrêmes est examiné. Plus précisément, les concentrations moyennes de chaque ion majeur, de même que la composition chimique globale des eaux en étiage et en crue sont confrontées aux valeurs obtenues dans les eaux de précipitation et les eaux souterraines. Il en ressort que, dans les eaux de la rivière Sainte‐Anne, même pour les épisodes d'étiage les plus sévères, la concentration des ions majeurs diffère sensiblement de celle des eaux souterraines. Par ailleurs, on observe que les concentrations sont significativement plus élevées en étiage qu'en crue pour l'ensemble des paramètres, ce qui est également mis en évidence par les relations concentration‐débit. Un bilan massique chimique par épisode a été esquissé, mais la contribution des eaux souterraines y apparaît généralement trop forte; on en déduit qu'une fraction seulement des eaux souterraines possède la concentration typique des eaux de puits ou que la nappe superficielle alimentant principalement l'écoulement en étiage, est bien moins chargée. Ces résultats mettent en évidence la complexité de l'évolution de la qualité même pour les éléments de comportement réputé simple.  相似文献   

Impact of salinity on early life history traits of three estuarine fish species in Senegal     

Maylis Labonne  Eric Morize  Pierre Scolan  Raymond Lae  Eric Dabas  Marcel Bohn 《Estuarine, Coastal and Shelf Science》2009,82(4):673-681

The adaptive mechanisms on the early life stages of fishes to hypersaline stress are still poorly understood and probably determine the resistance of a population to disruption, compared with other less plastic species. The Casamance River in Senegal is an ideal location to test the adaptation to salinity as a dam was built in 1998 to exclude saline water intrusion. This lowered the salinity from 70 to 5 upstream and 60 downstream. The salinity influence on the growth in the early life of three West African fish species (Ethmalosa fimbriata, Sarotherodon melanotheron, and Tilapia guineensis) was studied using the width of microstructures in the otoliths and the individual migratory behaviour analysed from strontium (Sr) to calcium (Ca) ratios in the otoliths. The Sr:Ca ratio was quantified along individual transects measured from the posterior edge of the otolith to the core. The fishes were sampled on both sides of the dam that separated water with low salinity upstream from metahaline and hyperhaline water downstream.The results showed that salinity has different influence on the growth of each species. Ethmalosa fimbriata has the highest growth during the first 180 days in the freshwaters, indicating growth inhibition in the hyperhaline areas. For the two other species no growth difference were found. The Sr/Ca ratio varied widely, in Tilapia and Sarotherodon from below the dam. Individual life histories were more heterogeneous than upstream and showed a crossing of the dam for some individuals which could reach half of the fishes analysed. On the contrary in E. fimbriata, despite the large range of salinity, identical Sr/Ca profiles were found both upstream and downstream. This indicated that Sr/Ca ratio was not appropriate to evaluate life history patterns linked to salinity for this specie.  相似文献   

Phytoplankton community adaptation to changing light levels in the southern Beaufort Sea,Canadian Arctic     

Atsushi Matsuoka  Pierre Larouche  Michel Poulin  Warwick Vincent  Hiroshi Hattori 《Estuarine, Coastal and Shelf Science》2009

The chlorophyll a specific absorption coefficient of phytoplankton, a_φ^∗(λ) is an important parameter to determine for primary production models and for the estimation of phytoplankton physiological condition. Knowledge of this parameter at high latitudes where nutrient rich cold water submitted to low incident light is a common environment is almost nonexistent. To address this issue, we investigated the light absorption properties of phytoplankton as a function of irradiance, temperature, and nutrients using a large data set in the southern Beaufort Sea during the open water to ice cover transition period. The a_φ^∗(λ) tended to increase from autumn when open water still existed to early winter when sea ice cover was formed, resulting from a biological selection of smaller-size phytoplankton more efficient to absorb light. There was no significant correlation between a_φ^∗(λ) and irradiance or temperature for both seasons. However, a_φ^∗(λ) showed a significant positive correlation with NO₃ + NO₂. Implications of the results for phytoplankton community adaptation to changing light levels are discussed.  相似文献   

Variability of nutrients and phytoplankton primary production in a shallow macrotidal coastal ecosystem (Arcachon Bay,France)     

Corine Glé  Yolanda Del Amo  Benoît Sautour  Pierre Laborde  Pierre Chardy 《Estuarine, Coastal and Shelf Science》2008

Seasonal and spatial variations of phytoplankton primary production were studied using a high frequency sampling strategy in the external (ENW) and internal (INW) part of Arcachon Bay, during 2002 and 2003. In order to better assess the availability of nutrients and their relationship with phytoplankton primary production, nutrient variability was studied in relation to environmental conditions and phytoplankton production. During winter, when primary production rates were the lowest, nutrient concentrations were maximal but did not show excessive levels compared to highly urbanised areas. Seasonal and spatial variations of nutrient concentrations (especially DIN-nitrate + nitrite + ammonium- and Si) were largely influenced by Leyre River loads coupled with high tidal exchange with the Atlantic Ocean creating a nutrient gradient between the INW and ENW. By February, diatom growth leads to an early severe nutrient depletion in the entire bay. Examination of nutrient ratios showed that the potential limiting nutrient during spring was P in 2003, and Si in 2002. During summer 2003, N and Si concentrations reached their lowest values, and nutrient ratios revealed a N-deficient environment, more pronounced in the INW. The high Si:N ratios during this period might be explained by (1) important N-uptake by all autotroph communities and (2) benthic-pelagic coupling with high Si regeneration. This study shows that nutrient levels in Arcachon Bay seem to play an important role in the control of phytoplankton primary production rates during the productive period and explain their spatial, seasonal and inter-annual variability. Our estimates of annual integrated phytoplankton primary production (103 g C m⁻² y⁻¹) place this bay within the low to moderate phytoplankton primary production systems.  相似文献   

Challenges to calibration: Facing an increasingly critical environment     

Olsthoorn TN  Kamps PT 《Ground water》2006,44(6):876-879

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Genesis and mineralization of gold-bearing quartz veins in the Xiao Qinling area, central China     

Jiwei Liang  Rongxi Li  Shaoni Zhang  Baoyun Chen  Lizhi Duan  Pierre Thibault 《中国地球化学学报》2012,31(4):441-448

Gold-bearing quartz veins of the Taihua Group consisting of Archean metavolcanic rocks are a main gold deposit type in the Xiao Qinling area,one of the three biggest gold production areas in China.The quartz veins experienced strong alteration characterized by a typical mesothermal hydrothermal altered mineral assemblage.The grade of gold is affected by the contents of sulphides,e.g.galena,pyrite and chalcopyrite.Results of minor elements analysis for the of gold-bearing quartz veins indicate higher contents of Au and high contents of Ag,Pb,Cu,Cd,W,and Mo.Abundant fluid inclusions were found in the gold-bearing quartz veins.Three types of fluid inclusions were identified:(1) aqueous inclusions;(2) CO 2-bearing inclusions;and(3) daughter crystal-bearing fluid inclusions.Homogenization temperatures ranged from 110 to 670℃ with low and high peaks appearing at 160 180℃ and 280 300℃,respectively.The salinity of aqueous inclusions varies between 1.8 wt% and 38.2 wt% NaCl.The homogenization temperature and salinity show a positive correlation.The H and O isotopes of fluid inclusions in the gold-bearing quartz veins indicate that magmatic solution and metamorphic hydrothermal solution,together with meteoric water,were involved in the formation of gold-bearing fluid.Mesozoic magma activities related to granite intrusions should be the main source of CO 2 fluid with higher temperature and salinity.  相似文献   

Astrodynamical Space Test of Relativity using Optical Devices I (ASTROD I)—a class-M fundamental physics mission proposal for cosmic vision 2015–2025: 2010 Update     

Claus Braxmaier  Hansj?rg Dittus  Bernard Foulon  Ertan G?klü  Catia Grimani  Jian Guo  Sven Herrmann  Claus L?mmerzahl  Wei-Tou Ni  Achim Peters  Benny Rievers  étienne Samain  Hanns Selig  Diana Shaul  Drazen Svehla  Pierre Touboul  Gang Wang  An-Ming Wu  Alexander F. Zakharov 《Experimental Astronomy》2012,34(2):181-201

ASTROD I is a planned interplanetary space mission with multiple goals. The primary aims are: to test General Relativity with an improvement in sensitivity of over 3 orders of magnitude, improving our understanding of gravity and aiding the development of a new quantum gravity theory; to measure key solar system parameters with increased accuracy, advancing solar physics and our knowledge of the solar system; and to measure the time rate of change of the gravitational constant with an order of magnitude improvement and the anomalous Pioneer acceleration, thereby probing dark matter and dark energy gravitationally. It is envisaged as the first in a series of ASTROD missions. ASTROD I will consist of one spacecraft carrying a telescope, four lasers, two event timers and a clock. Two-way, two-wavelength laser pulse ranging will be used between the spacecraft in a solar orbit and deep space laser stations on Earth, to achieve the ASTROD I goals.For this mission, accurate pulse timing with an ultra-stable clock, and a drag-free spacecraft with reliable inertial sensor are required. T2L2 has demonstrated the required accurate pulse timing; rubidium clock on board Galileo has mostly demonstrated the required clock stability; the accelerometer on board GOCE has paved the way for achieving the reliable inertial sensor; the demonstration of LISA Pathfinder will provide an excellent platform for the implementation of the ASTROD I drag-free spacecraft. These European activities comprise the pillars for building up the mission and make the technologies needed ready. A second mission, ASTROD or ASTROD-GW (depending on the results of ASTROD I), is envisaged as a three-spacecraft mission which, in the case of ASTROD, would test General Relativity to one part per billion, enable detection of solar g-modes, measure the solar Lense-Thirring effect to 10 parts per million, and probe gravitational waves at frequencies below the LISA bandwidth, or in the case of ASTROD-GW, would be dedicated to probe gravitational waves at frequencies below the LISA bandwidth to 100?nHz and to detect solar g-mode oscillations. In the third phase (Super-ASTROD), larger orbits could be implemented to map the outer solar system and to probe primordial gravitational-waves at frequencies below the ASTROD bandwidth. This paper on ASTROD I is based on our 2010 proposal submitted for the ESA call for class-M mission proposals, and is a sequel and an update to our previous paper (Appouchaux et al., Exp Astron 23:491?C527, 2009; designated as Paper I) which was based on our last proposal submitted for the 2007 ESA call. In this paper, we present our orbit selection with one Venus swing-by together with orbit simulation. In Paper I, our orbit choice is with two Venus swing-bys. The present choice takes shorter time (about 250?days) to reach the opposite side of the Sun. We also present a preliminary design of the optical bench, and elaborate on the solar physics goals with the radiation monitor payload. We discuss telescope size, trade-offs of drag-free sensitivities, thermal issues and present an outlook.  相似文献   

A DUAL mission for nuclear astrophysics     

Peter von Ballmoos  Jose Alvarez  Nicolas Barrière  Steve Boggs  Andrei Bykov  Juan Manuel Del Cura Velayos  Filippo Frontera  Lorraine Hanlon  Margarita Hernanz  Emmanuel Hinglais  Jordi Isern  Pierre Jean  Jürgen Kn?dlseder  Lucien Kuiper  Mark Leising  Beno?t Pirard  Jean-Pierre Prost  Rui M. Curado da Silva  Tadayuki Takahashi  John Tomsick  Roland Walter  Andreas Zoglauer 《Experimental Astronomy》2012,34(2):583-622

DUAL will study the origin and evolution of the elements and explores new frontiers of physics: extreme energies that drive powerful stellar explosions and accelerate particles to macroscopic energies; extreme densities that modify the laws of physics around the most compact objects known; and extreme fields that influence matter in a way that is unknown on Earth. The variability of these extreme objects requires continuous all-sky coverage, while detailed study demands an improvement in sensitivity over previous technologies by at least an order of magnitude. The DUAL payload is composed of an All-Sky Compton Imager (ASCI), and two optical modules, the Laue-Lens Optic (LLO) and the Coded-Mask Optic (CMO). The ASCI serves dual roles simultaneously, both as an optimal focal-plane sensor for deep observations with the optical modules and as a sensitive true all-sky telescope in its own right for all-sky surveys and monitoring. While the optical modules are located on the main satellite, the All-Sky Compton Imager is situated on a deployable structure at a distance of 30?m from the satellite. This configuration not only permits to maintain the less massive payload at the focal distance, it also greatly reduces the spacecraft-induced detector background, and, above all it provides ASCI with a continuous all-sky exposure.  相似文献