Mauer – the type site of Homo heidelbergensis: palaeoenvironment and age     

Günther A. Wagner  Lutz Christian Maul  Manfred Löscher  H. Dieter Schreiber 《Quaternary Science Reviews》2011,30(11-12):1464-1473

The mandible of Homo heidelbergensis was found 1907 in the sand pit Grafenrain at Mauer in coarse fluvial sands 24 m below the surface, deposited in a former course of the Neckar River. These ‘Mauer sands’ are overlain by a series of glacial-climate loess deposits with intercalated interglacial palaeosols, which can be correlated with Quaternary climate history, thus indicating an early Middle Pleistocene age for H. heidelbergensis. The ‘Mauer sands’ are famous for their rather rich mammal fauna, which clearly indicates interglacial climate conditions. The faunal evidence – in particular the micromammals – place the ‘Mauer sands’ into MIS 15 or MIS 13 although most stratigraphic arguments favour correlation to MIS 15 and therefore to an age of ca 600 ka.  相似文献   

Why chromatic imaging matters     

Joel Sanchez-Bermudez  Florentin Millour  Fabien Baron  Roy van Boekel  Laurent Bourgès  Gilles Duvert  Paulo J. V. Garcia  Nuno Gomes  Karl-Heinz Hofmann  Thomas Henning  Jacob W. Isbell  Bruno Lopez  Alexis Matter  J-Uwe Pott  Dieter Schertl  Eric Thiébaut  Gerd Weigelt  John Young 《Experimental Astronomy》2018,46(3):457-473

During the last two decades, the first generation of beam combiners at the Very Large Telescope Interferometer has proved the importance of optical interferometry for high-angular resolution astrophysical studies in the near- and mid-infrared. With the advent of 4-beam combiners at the VLTI, the u ? v coverage per pointing increases significantly, providing an opportunity to use reconstructed images as powerful scientific tools. Therefore, interferometric imaging is already a key feature of the new generation of VLTI instruments, as well as for other interferometric facilities like CHARA and JWST. It is thus imperative to account for the current image reconstruction capabilities and their expected evolutions in the coming years. Here, we present a general overview of the current situation of optical interferometric image reconstruction with a focus on new wavelength-dependent information, highlighting its main advantages and limitations. As an Appendix we include several cookbooks describing the usage and installation of several state-of-the art image reconstruction packages. To illustrate the current capabilities of the software available to the community, we recovered chromatic images, from simulated MATISSE data, using the MCMC software SQUEEZE. With these images, we aim at showing the importance of selecting good regularization functions and their impact on the reconstruction.  相似文献   

Characteristics of the semidiurnal tide in the MLT over Maui (20.75°N, 156.43°W) with meteor radar observations     

A. Guharay  S.J. Franke 《Journal of Atmospheric and Solar》2011,73(5-6):678-685

Semidiurnal tidal features have been examined in the Mesosphere and Lower Thermosphere (MLT) from the long-term (2002–2007) meteor wind data over Maui (20.75°N, 156.43°W). Amplitude and phase obtained from the harmonic analysis exhibit large day to day variability. Mean amplitude obtained from the monthly mean data over the observation period is found to vary within ～8–28 m/s and 10–32 m/s for the zonal and meridional winds, respectively. The amplitude has revealed clear semiannual oscillation (SAO) pattern with maxima during solstices and altitudinal growth in both wind components. Significant resemblance in its variability with other observations carried out from the low latitude sites all over the globe is obtained. Vertical wavelength estimated from the phase gradients exposes large values (>90 km) in all seasons. Contribution of the semidiurnal tide to the total tidal variability in the MLT is found to vary over wide range throughout the year with generally higher influence during winter season over diurnal and terdiurnal components.  相似文献   

Uranium–lead ages of apatite from iron oxide ores of the Bafq District,East-Central Iran     

Heinz-Günter Stosch  Rolf L. Romer  Farahnaz Daliran  Dieter Rhede 《Mineralium Deposita》2011,46(1):9-21

Iron oxide–apatite (IOA) deposits, often referred to as Kiruna-type iron ore deposits, are known to have formed from the Proterozoic to the Tertiary. They are commonly associated with calc–alkaline volcanic rocks and regional- to deposit-scale metasomatic alteration. In the Bafq District in east Central Iran, economic iron oxide–apatite deposits occur within felsic volcanic tuffs and volcanosedimentary sequences of Early Cambrian age. In order to constrain the age of formation of these ores and their relationship with the Early Cambrian magmatic event, we have determined the U–Pb apatite age for five occurrences in the Bafq District. In a ²⁰⁶Pb/²³⁸U vs. ²⁰⁷Pb/²³⁵U diagram, apatite free of or poor in inclusions of other minerals plots along the Concordia between 539 and 527 Ma with four out of five samples from one deposit clustering at the upper end of this range. For this deposit, we interpret this cluster to represent the age of apatite formation, whereas the spread towards younger ages may reflect either minor Pb loss or several events of IOA formation. Apatite with inclusions of monazite (±xenotime) yields disturbed systems with inclusions having developed after formation of the iron ore–apatite deposits, possibly as late as 130–140 Ma ago. Obtained apatite ages confirms that (IOA) and the apatite-rich rocks (apatites) of the Bafq district formed coevally with the Early Cambrian magmatic (-metasomatic) events.  相似文献   

Biogenic carbon flows through the planktonic food web of the Amundsen Gulf (Arctic Ocean): A synthesis of field measurements and inverse modeling analyses   总被引：1，自引：0，他引：1  

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   

The continent-ocean transition at the southeastern margin of the South China Sea   总被引：2，自引：0，他引：2  

D. Franke  U. BarckhausenN. Baristeas  M. EngelsS. Ladage  R. LutzJ. Montano  N. PellejeraE.G. Ramos  M. Schnabel 《Marine and Petroleum Geology》2011,28(6):1187-1204

The South China Sea formed by magma-poor, or intermediate volcanic rifting in the Paleogene. We investigate the structure of the continent-ocean transition (COT) at its southern margin, off NW Palawan between the continental blocks of Reed Bank and the islands of Palawan and Calamian. Several surveys, recorded by the BGR from 1979 to 2008, established a comprehensive database of regional seismic lines, accompanied with magnetic and gravity profiles.We interpret two major rifted basins, extending in the NE direction across the shelf and slope, separated by a structural high of non volcanic origin.The continent-ocean transition is interpreted at the seaward limit of the continental crust, when magnetic spreading anomalies terminate some 80-100 km farther north. The area in between displays extensive volcanism - as manifest by extrusions that occasionally reach and cut the seafloor, by dykes, and by presumed basaltic lava flows - occurring after break-up.The COT is highly variable along the NW Palawan slope: One type shows a distinct outer ridge at the COT with a steep modern seafloor relief. The other type is characterised by rotated fault blocks, bounded by listric normal faults ramping down to a common detachment surface. Half-grabens developed above a strongly eroded pre-rift basement. The seafloor relief is smooth across this other type of COT.We suggest the pre-rift lithospheric configuration had major influence on the formation of the COT, besides transfer zones. Volcanic domains, confined to the north of competent crustal blocks correlate with the style of the COT.Gravity modelling revealed an extremely thinned crust across the shelf. We propose a depth-dependent extension model with crust being decoupled from mantle lithosphere, explaining the discrepancy of subsidence observed across the South China Sea region.  相似文献   

Atmospheric Circulation Changes in Response to an Observed Stratospheric Zonal Ozone Anomaly     

Dieter H. W. Peters  Andrea Schneidereit  Marianne Bügelmayer  Christoph Zülicke  Ingo Kirchner 《大气与海洋》2015,53(1):74-88

Abstract

In a sensitivity study, the influence of an observed stratospheric zonal ozone anomaly on the atmospheric circulation was investigated using the Fifth Generation European Centre Hamburg Model (ECHAM5) which is a general circulation model. The model was run from 1960 to 1999 (40 years) with a mean seasonal cycle of zonally symmetric ozone. In order to isolate the induced dynamical influence of the observed zonally asymmetric part of the three-dimensional stratospheric ozone, a second run was performed for the boreal extratropics using prescribed monthly means from the 40-year reanalysis dataset from the European Centre for Medium-range Weather Forecasts (ERA-40). The main findings are the interdecadal westward shift of the polar vortex at about 65°N and a significant increase in the number of stratospheric sudden warmings during the 1980–99 period. Under the action of zonally asymmetric ozone a decrease in the Arctic Oscillation was identified between the mid-1980s and the mid-1990s. The lag correlation between the mean Arctic Oscillation at the surface and the daily stratospheric northern annular mode increased in mid-winter. Furthermore, we examined the influence of the stratospheric zonal ozone anomaly on Rossby wave breaking in the upper troposphere and found a significant westward shift of poleward Rossby wave breaking events over western Europe in the winter. By this we show that the stratospheric zonal ozone anomaly has a strong influence on the tropospheric circulation as a result of enhanced dynamical coupling processes.  相似文献   

Pliocene climate change of the Southwest Pacific and the impact of ocean gateways     

Cyrus Karas  Dirk Nürnberg  Ralf Tiedemann  Dieter Garbe-Schönberg 《Earth and Planetary Science Letters》2011,301(1-2):117-124

The transition from the early Pliocene “Warmhouse” towards the present “Icehouse” climate and the role of Gateway dynamics are intensively debated. Both, the constrictions of the Central American Seaway and the Indonesian Gateway affected ocean circulation and climate during the Pliocene epoch. Here, we use combined δ¹⁸O and Mg/Ca ratios of planktonic foraminifera (marine protozoa) from surface and subsurface levels to reconstruct the thermal structure and changes in salinities from the Southwest Pacific Deep Sea Drilling Project (DSDP) Site 590B from 6.5 to 2.5 Ma. Our data suggest a gradual cooling of ~ 2 °C and freshening of the sea surface during ~ 4.6–4 Ma with an increased meridional temperature gradient between the West Pacific Warm Pool and the Southwest Pacific when the closing of the Central American Seaway reached a critical threshold. After ~ 3.5 Ma, the restricted Indonesian Gateway might have amplified the East Australian Current, allowing enhanced heat transport towards the Southwest Pacific with reduced meridional temperature gradients when the global climate gradually cooled. At the same time our data suggest a cooling and freshening of Subantarctic Mode Water (SAMW) or/and an increased northward flow of SAMW towards Site 590B, possibly a first step towards the present Antarctic Frontal System.  相似文献   

SUJETS A TRAITER POUR L'ASSEMBLÉE DE 1960     

Dr.-Ing. Dieter LAUTERBACH  Eberhard GLOS 《水文科学杂志》2013,58(3):9-12

ABSTRACT

The present paper reports on some practical experiences gained in computing unit hydrographs (UH) according to the “classical” linear theory. The sizes of the drainage basins varied from 50 to 800 km² of hilly country.  相似文献   

Altitude variation of the plasmapause signature in the main ionospheric trough     

Joseph M. Grebowsky  Robert F. Benson  Phillip A. Webb  Vladimir Truhlik  Dieter Bilitza 《Journal of Atmospheric and Solar》2009,71(16):1669-1676

The projection of the plasmapause magnetic-field lines to low altitudes, where the light-ion chemistry is dominated by O⁺, tends to occur near the minimum electron density in the main (midlatitude) electron density trough at night. With increasing altitude in the trough, where H⁺ emerges as the dominant ion on the low-latitude boundary, we have found cases where the plasmapause field lines are located on the sharp low-latitude side of the trough as expected if this topside ionosphere H⁺ distribution varies in step with the plasmapause gradient in the distant plasmasphere. These conclusions are based on near-equatorial crossings of the plasmapause (corresponding to the steep gradient in the dominant species H⁺) by the Explorer-45 satellite as determined from electric-field measurements by Maynard and Cauffman in the early 1970s and ISIS-2 ionospheric topside-sounder measurements. The former data have now been converted to digital form and made available at http://nssdcftp.gsfc.nasa.gov. The latter provide samples of nearly coincident observations of ionospheric main trough crossings near the same magnetic-field lines of the Explorer 45-determined equatorial plasmapause. The ISIS-2 vertical electron density profiles are used to infer where the F-region transitions from an O⁺ to a H⁺ dominated plasma through the main trough boundaries.  相似文献