Late Quaternary climate change record from two long sediment cores from Guaymas Basin,Gulf of California     

Heather Cheshire  Jürgen Thurow  Alexandra J. Nederbragt 《第四纪科学杂志》2005,20(5):457-469

Modern Guaymas Basin (Gulf of California, Mexico) is a region of high diatom productivity where exceptional preservation factors maintain biannually alternating sediment deposition as annual varves. New sediment cores from Guaymas Basin (MD02‐2512 and MD02‐2515) present the opportunity to construct climate records from below the last glacial period. A low‐resolution age model has been constructed from oxygen isotope analysis, correlation with other dated short piston cores from Guaymas Basin and an estimate of sedimentation rate. MD02‐2512 from eastern Guaymas Basin has an age range from the Holocene to late marine isotope stage 6 (MIS 6); MD02‐2515 from western Guaymas Basin has an age range from ～8000 to 40 000 yr. Shipboard analyses of colour reflectance, magnetic susceptibility and sediment density are combined with continuous X‐ray fluorescence scans to reconstruct a picture of glacial climate in the Gulf of California. Eastern Guaymas Basin is affected by glacial sea level fall, which results in a drastic change in productivity rates and sediment type. The laminated record of MIS 5 allows comparison with the Holocene, showing a similarity of sedimentation patterns during deglaciation and a series of very rapid variations just prior to the last glaciation. In western Guaymas Basin there are a series of Younger Dryas‐like events during the glacial, typified by low productivity and high terrigenous input. Long‐term climate and productivity changes appear to be caused by the southward displacement of the Subtropical High pressure zone. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Geology and stratigraphy of King crater, lunar farside   总被引：1，自引：0，他引：1  

David J Heather  Sarah K Dunkin 《Icarus》2003,163(2):307-329

Clementine and photographic data sets have been used to investigate the crustal stratigraphy and geology of King crater on the lunar farside (120°E, 5.5°N). Pre-existing topographic regimes or stress fields dominate many structures in the crater, which has excavated materials from depths of up to 14 km. The upper crust in the area is noritic anorthosite, grading to a more anorthositic signature with depth. A possible batholithic intrusion is also present in a 15-km-wide band, extending from the southern crater floor to at least 50 km north of King, and from near-surface levels down to at least the excavation depth of the crater. It is generally feldspathic, but is cut by mafic dykes now visible in the north wall. King also shows evidence for the presence of a cryptomare, exposed in regions of the peaks and in dark halo craters within the ejecta blanket. Localized olivine-bearing mineralogies are observed on the central peaks, suggesting isolated pockets of troctolitic mineralogies to have been present at 8- to 14-km depths. Copious volumes of crystalline melt produced from the impact event cover King’s floor to a maximum thickness of 30-60 m, and have pooled in a number of natural depressions outside of the main crater. The main pool in the pre-existing A1-Tusi crater has a minimum depth of 150 m. Domes on the crater floor are verified as nonvolcanic in origin, and did not act as a source for any of the lava-like materials in King.  相似文献   

Scientific rationale for the D-CIXS X-ray spectrometer on board ESA's SMART-1 mission to the Moon     

S.K Dunkin  M GrandeI Casanova  V FernandesD.J Heather  B KellettK Muinonen  S.S RussellR Browning  N WalthamD Parker  B KentC.H Perry  B SwinyardA Perry  J FeradayC Howe  K PhillipsG McBride  J HuovelinP Muhli  P.J HakalaO Vilhu  N ThomasD Hughes  H AlleyneM Grady  R LundinS Barabash  D BakerP.E Clark  C.D MurrayJ Guest  L.C d'UstonS Maurice  B FoingA Christou  C OwenP Charles  J LaukkanenH Koskinen  M KatoK Sipila  S NenonenM Holmstrom  N BhandariR Elphic  D Lawrence 《Planetary and Space Science》2003,51(6):435-442

The D-CIXS X-ray spectrometer on ESA's SMART-1 mission will provide the first global coverage of the lunar surface in X-rays, providing absolute measurements of elemental abundances. The instrument will be able to detect elemental Fe, Mg, Al and Si under normal solar conditions and several other elements during solar flare events. These data will allow for advances in several areas of lunar science, including an improved estimate of the bulk composition of the Moon, detailed observations of the lateral and vertical nature of the crust, chemical observations of the maria, investigations into the lunar regolith, and mapping of potential lunar resources. In combination with information to be obtained by the other instruments on SMART-1 and the data already provided by the Clementine and Lunar Prospector missions, this information will allow for a more detailed look at some of the fundamental questions that remain regarding the origin and evolution of the Moon.  相似文献   

“Stone Decay Hazards”     

Siegfried Siegesmund  Heather Viles  Thomas Weiss 《Environmental Geology》2004,46(3-4):303-304

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Calcification rate and temperature effects on Sr partitioning in coccoliths of multiple species of coccolithophorids in culture     

Heather M. Stoll  Christine M. Klaas  Ian Probert  Jorge Ruiz Encinar  J. Ignacio Garcia Alonso   《Global and Planetary Change》2002,34(3-4)

Five common placolith-bearing coccolithophorid algae—Gephyrocapsa oceanica, Coccolithus pelagicus, Calcidiscus leptoporus, Umbilicosphaera sibogae (var. sibogae and var. foliosa), and Emiliania huxleyi—were cultured to investigate controls on Sr partitioning in coccolith calcite. For identical temperature and media composition, Sr partitioning varies by more than 30% in exponential phase cultures of the five species and is linearly related to rates of calcite production/cell (ρ=0.91). Exponential phase culture experiments with three strains of C. leptoporus and six strains of G. oceanica at varying temperatures show variations in Sr partitioning of 20% and 30%, respectively. With C. leptoporus, Sr partitioning is equally correlated with temperature and calcification rate (ρ=0.8), which themselves are highly correlated; the slope of the relationship between D_Sr and calcification rate is comparable to that observed in all species at constant temperature. However, in G. oceanica, increased temperature appears to enhance Sr incorporation by up to 2% to 1.6% °C⁻¹ in the range of 15 to 30 °C. The strong influence of calcification rate on Sr partitioning may be useful for inferring past variations in coccolithophorid productivity from Sr partitioning in coccolith sediments if the influence of temperature on Sr partitioning can be resolved. Because the relationship between calcite production and Sr partitioning is linear, a proportional change in calcification should be expressed much more strongly in the Sr/Ca ratio of large species with rapid calcite production than in smaller species, which produce calcite more slowly. Consequently, it may be possible to separate temperature and calcification influences on coccolith Sr/Ca by separately analyzing Sr/Ca in species that produce calcite rapidly and those that produce calcite slowly, if both undergo comparable relative changes in calcification rates.  相似文献   

The radial velocity dispersion profile of the Galactic halo: constraining the density profile of the dark halo of the Milky Way     

Giuseppina Battaglia  Amina Helmi  Heather Morrison  Paul Harding  Edward W. Olszewski  Mario Mateo  Kenneth C. Freeman  John Norris  Stephen A. Shectman 《Monthly notices of the Royal Astronomical Society》2005,364(2):433-442

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Quantifying Striped Bass (<Emphasis Type="Italic">Morone saxatilis</Emphasis>) Dependence on Saltmarsh-Derived Productivity Using Stable Isotope Analysis     

Henry?K.?Baker  James?A.?NelsonEmail author  Heather?M.?Leslie 《Estuaries and Coasts》2016,39(5):1537-1542

Each winter, populations of striped bass (Morone saxatilis) migrate north from the coastal mid-Atlantic region of the US to the coastal waters of New England. During this migration, striped bass spend significant time in estuaries and saltmarshes, presumably to forage. However, the extent to which saltmarsh productivity supports striped bass remains unresolved. We used a three-isotope Bayesian mixing model to determine the relative contribution of three primary producers [C4 saltmarsh cordgrass (Spartina spp.), phytoplankton, and benthic diatoms] to striped bass tissue. Phytoplankton (51 % contribution) and Spartina-derived sources (44 % contribution) are the primary sources of production to striped bass, while benthic diatoms made a relatively small contribution (5 %). Our results highlight the importance of saltmarshes to striped bass by showing that primary producers unique to saltmarsh ecosystems support a large proportion of striped bass production.  相似文献   

Climate change impacts on ecosystems and ecosystem services in the United States: process and prospects for sustained assessment     

Nancy B. Grimm  Peter Groffman  Michelle Staudinger  Heather Tallis 《Climatic change》2016,135(1):97-109

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Seismic site characterization with shear wave (SH) reflection and refraction methods     

Hunter  James A.  Crow  Heather L.  Stephenson  William J.  Pugin  André J.-M.  Williams  Robert A.  Harris  James B.  Odum  Jack K.  Woolery  Edward W. 《Journal of Seismology》2022,26(4):631-652

Journal of Seismology - Reflection and critically refracted seismic methods use traveltime measurements of body waves propagating between a source and a series of receivers on the ground surface to...  相似文献   

Second-degree Stokes coefficients from multi-satellite SLR   总被引：1，自引：1，他引：0  

Mathis Bloßfeld  Horst Müller  Michael Gerstl  Vojtěch Štefka  Johannes Bouman  Franziska Göttl  Martin Horwath 《Journal of Geodesy》2015,89(9):857-871

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