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91.
Zusammenfassung Quantitative Gefügediagramme können röntgenographisch mit einem Zählrohr-Textur-Goniometer gemessen werden. Diese Methode kommt besonders in Frage bei sehr feinkörnigen Gesteinen oder aber dann, wenn etwa bei einachsigen Mineralen auch die Regelung anderer Gitterrichtungen außer der c-Achsen-Richtung interessiert. Das beim Quarz anzuwendende Verfahren wird behandelt und gezeigt, wie man hier im Einzelfall Prismenregelungen nachweisen kann. Als praktische Beispiele werden Quarzitgefüge mit Prismenregelung aus kaledonischen Überschiebungszonen Schottlands und Norwegens abgebildet und ihre Entstehung diskutiert. Die Messungen scheinen darauf hinzuweisen, daß beim Quarz bevorzugt Translation mit (11¯20) als Gleitfläche und c als Gleitgerade maßgebend war. 相似文献
92.
93.
Alexandre Forest Jean-Éric Tremblay Yves Gratton Johannie Martin Jonathan Gagnon Gérald Darnis Makoto Sampei Louis Fortier Mathieu Ardyna Michel Gosselin Hiroshi Hattori Dan Nguyen Roxane Maranger Dolors Vaqué Cèlia Marrasé Carlos Pedrós-Alió Amélie Sallon Christine Michel Colleen Kellogg Jody Deming Elizabeth Shadwick Helmuth Thomas Heike Link Philippe Archambault Dieter Piepenburg 《Progress in Oceanography》2011,91(4):410-436
Major pathways of biogenic carbon (C) flow are resolved for the planktonic food web of the flaw lead polynya system of the Amundsen Gulf (southeast Beaufort Sea, Arctic Ocean) in spring-summer 2008. This period was relevant to study the effect of climate change on Arctic marine ecosystems as it was characterized by unusually low ice cover and warm sea surface temperature. Our synthesis relied on a mass balance estimate of gross primary production (GPP) of 52.5 ± 12.5 g C m−2 calculated using the drawdown of nitrate and dissolved inorganic C, and a seasonal f-ratio of 0.64. Based on chlorophyll a biomass, we estimated that GPP was dominated by phytoplankton (93.6%) over ice algae (6.4%) and by large cells (>5 μm, 67.6%) over small cells (<5 μm, 32.4%). Ancillary in situ data on bacterial production, zooplankton biomass and respiration, herbivory, bacterivory, vertical particle fluxes, pools of particulate and dissolved organic carbon (POC, DOC), net community production (NCP), as well as selected variables from the literature were used to evaluate the fate of size-fractionated GPP in the ecosystem. The structure and functioning of the planktonic food web was elucidated through inverse analysis using the mean GPP and the 95% confidence limits of every other field measurement as lower and upper constraints. The model computed a net primary production of 49.2 g C m−2, which was directly channeled toward dominant calanoid copepods (i.e. Calanus hyperboreus 20%, Calanus glacialis 10%, and Metridia longa 10%), other mesozooplankton (12%), microzooplankton (14%), detrital POC (18%), and DOC (16%). Bacteria required 29.9 g C m−2, a demand met entirely by the DOC derived from local biological activities. The ultimate C outflow comprised respiration fluxes (82% of the initial GPP), a small sedimentation (3%), and a modest residual C flow (15%) resulting from NCP, dilution and accumulation. The sinking C flux at the model limit depth (395 m) supplied 60% of the estimated benthic C demand (2.8 g C m−2), suggesting that the benthos relied partly on other C sources within the bottom boundary layer to fuel its activity. In summary, our results illustrate that the ongoing decline in Arctic sea ice promotes the growth of pelagic communities in the Amundsen Gulf, which benefited from a ∼80% increase in GPP in spring-summer 2008 when compared to 2004 – a year of average ice conditions and relatively low GPP. However, 53% of the secondary production was generated within the microbial food web, the net ecological efficiency of zooplankton populations was not particularly high (13.4%), and the quantity of biogenic C available for trophic export remained low (6.6 g C m−2). Hence it is unlikely that the increase in lower food web productivity, such as the one observed in our study, could support new harvestable fishery resources in the offshore Beaufort Sea domain. 相似文献
94.
Stable carbon isotope distribution of particulate organic matter in the ocean: a model study 总被引:4,自引:0,他引:4
Matthias Hofmann Dieter A. Wolf-Gladrow Taro Takahashi Steward C. Sutherland Katharina D. Six Ernst Maier-Reimer 《Marine Chemistry》2000,72(2-4)
The stable carbon isotopic composition of particulate organic matter in the ocean, δ13CPOC, shows characteristic spatial variations with high values in low latitudes and low values in high latitudes. The lowest δ13CPOC values (−32‰ to −35‰) have been reported in the Southern Ocean, whereas in arctic and subarctic regions δ13CPOC values do not drop below −27‰. This interhemispheric asymmetry is still unexplained. Global gradients in δ13CPOC are much greater than in δ13CDIC, suggesting that variations in isotopic fractionation during organic matter production are primarily responsible for the observed range in δ13CPOC. Understanding the factors that control isotope variability is a prerequisite when applying δ13CPOC to the study of marine carbon biogeochemistry. The present model study attempts to reproduce the δ13CPOC distribution pattern in the ocean. The three-dimensional (3D) Hamburg Model of the Oceanic Carbon Cycle version 3.1 (HAMOCC3.1) was combined with two different parametrizations of the biological fractionation of stable carbon isotopes. In the first parametrization, it is assumed that the isotopic fractionation between CO2 in seawater and the organic material produced by algae, P, is a function of the ambient CO2 concentration. The two parameters of this function are derived from observations and are not based on an assumption of any specific mechanism. Thus, this parametrization is purely empirical. The second parametrization is based on fractionation models for microalgae. It is supported by several laboratory experiments. Here the fractionation, P, depends on the CO2 concentration in seawater and on the (instantaneous) growth rates, μi, of the phytoplankton. In the Atlantic Ocean, where most field data are available, both parametrizations reproduce the latitudinal variability of the mean δ13CPOC distribution. The interhemispheric asymmetry of δ13CPOC can mostly be attributed to the interhemispheric asymmetry of CO2 concentration in the water. However, the strong seasonal variations of δ13CPOC as reported by several authors, can only be explained by a growth rate-dependent fractionation, which reflects variations in the cellular carbon demand. 相似文献
95.
Jashar?ArfaiEmail author Dieter?Franke Christoph?Gaedicke Rüdiger?Lutz Michael?Schnabel Stefan?Ladage Kai?Berglar Mario?Aurelio Jennie?Montano Nicole?Pellejera 《Marine Geophysical Researches》2011,32(3):349-362
Interpretation of deep 2-D multi-channel seismic data sheds insights into the geological evolution of the West Luzon Basin,
Philippines. This basin is a sediment-filled trough that is located between the island of Luzon and the outer arc high of
the west Luzon subduction zone. High-amplitude, low-frequency reflection bands mark the acoustic basement. The basement, at
about 6 s (TWT), is dissected by normal faults with some of them being inverted in a later phase of deformation. The sedimentary
successions, overlying the basement are stratified with partly chaotic structures and discontinuous reflectors. Five regional
unconformities separate major stratigraphic units. Grid calculations of our seismic data reveal variations in the sedimentation
pattern of the basin with a shift of the deposition centre from east to west and backwards during formation. A distinct bottom-simulating
reflector is commonly observed. Because the northern boundary of the continental fragments to the South of the West Luzon
Basin is unclear we speculate that the basin may be (partly) underlain by continental crust. The continental crust was affected
by rifting prior to and during the opening of the South China Sea and the basin was overprinted at a later stage by a forearc
structural setting when subduction was initiated. 相似文献
96.
97.
Changes in the water regime of the caspian sea 总被引:2,自引:0,他引:2
The article deals with issues of structure and dynamics of the Caspian Sea water balance. On the base of historical, paleogeomorphological
and other data the evolution history of the Caspian Sea and its basin has been observed for different time intervals down
to 400 thous. years ago. Presented are computerized data on water balance components in the current centenary obtained from
instrumental observations, revealed are causes of the sea-level fluctuations within that time interval and anthropogenic factor
contribution to this process. Based on the analysis of this material, an attempt has been undertaken to present a scenarion
of a possible sea-level position of the Caspian Sea with the expected versions of climatic changes at the end of the XX and
beginning of the XXI centuries. 相似文献
98.
Prof. Dr. Wolfgang Schott 《Contributions to Mineralogy and Petrology》1954,4(1-2):192-197
Zusammenfassung Durch Bestimmung der Foraminiferenanzahl in I g Sediment wird die biostratigraphische Untersuchungsmethode, die mittels einer qualitativen und quantitativen Erfassung der Foraminiferenfauna in den Tiefseekernen der deutschen Meteor-Expedition und schwedischen Albatroß-Expedition durchgeführt werden ist, auf ihre Richtigkeit hin geprüft. Die Untersuchung hat die Anwendbarkeit dieser stratigraphischen Methode bestätigt. Sie hat daneben wiederum gezeigt, daß die Verbreitung und Entwicklung der einzelnen Foraminiferenarten vor allem von der Temperatur des Meerwassers abhängig sind; andere Faktoren wie Phosphatgehalt des Wassers usw. scheinen in dieser Hinsicht eine mehr untergeordnete Rolle zu spielen. Unter gewissen Voraussetzungen können Tiefseekerne durch Bestimmung der Foraminiferenanzahl je 1 g Sediment in groben Zügen stratigraphisch gegliedert werden; auch kann die Individuenanzahl der einzelnen Foraminiferenarten aus der Foraminiferenanzahl in 1 g Sediment und aus der prozentualen Zusammensetzung der Gesamtfauna errechnet werden. Mit den hier gewonnenen Erkenntnissen wird versucht, die engen Bezichungen zwischen dem prozentualen Anteil der Warmwasserforaminiferen in der Gesamtfauna und dem CO2-Gehalt des Sedimentes, dieOvey im Kern 241 der schwedischen Albatroß-Expedition beobachtet hat, zu deuten.Herrn Professor Dr.Carl W. Correns zum 60. Geburtstag gewidmet. 相似文献
99.
100.
Prof. Dr. Thomas K. Rudel 《GeoJournal》1989,19(4):437-446
This paper argues that the process of establishing claims and control over resources, referred to as resource partitioning, structures frontier societies in ways which impede subsequent efforts at rural development. Conflicts over claims to resources create divisions among local elites which prevent the formation of coalitions to promote development. Struggles for control over the flow of resources out of a region cause regional development agencies to pursue transportation policies which retard development by isolating the region from all but one commercial center. A case study of resource partitioning and rural development efforts in the Ecuadorian Amazon illustrates the argument. 相似文献