News & Views     

Vicki Kretsinger Grabert  Dawn Samara Kaback  Beth L. Parker  Steven W. Chapman  John A. Cherry  Francis H. Chapelle  Michael A. Singletary  Murray D. Einarson  Doug M. Mackay  Peter J. Bennett 《Ground water》2010,48(6):799-808

  相似文献   

Electrical resistivity surveys as indicators of site potential: Examples from a rock shelter in Southwestern France and a cave in Southern Albania     

Brooks B. Ellwood  Francis B. Harrold  Karl M. Petruso  Muzafer Korkuti 《Geoarchaeology》1993,8(3):217-227

Electrical resistivity surveys have been conducted, in conjunction with follow-up auger and test excavations, to optimize the excavation potential within two European closed sites. The first site, Pont d'Ambon II rock shelter, is situated on the Dronne River in the Department of the Dordogne, southwestern France. It is located ∼100 m south of Pont d'Ambon I rock shelter, from which late Upper Paleolithic cultural material has been recovered. Auger testing within Pont d'Ambon II yielded results predicted by evaluation of the electrical data, including an area which contains cultural material. A second area contained a large, near-surface limestone block, which probably resulted from a rock fall. The second site is located in a cave near the town of Konispol, Albania, in the southernmost part of the country. Its cultural deposits range in age from the Iron Age to at least Late Paleolithic times. Interpretation of the electrical resistivity data from Konispol Cave indicates that thick, relatively undisturbed sediments cover the floor in central portions of the cave. Only in one area near the entrance are limestone blocks likely to impair excavation efforts. Results from a test excavation, associated with an anomaly in the electrical data, uncovered a large, carefully constructed hearth. These data indicate that preliminary geophysical surveys at many archaeological sites can optimize excavation potential. © 1993 John Wiley & Sons, Inc.  相似文献   

Simultaneous photometry and spectroscopy of the newly discovered γ Doradus variable HR 8330=HD 207223     

Anthony B. Kaye  Gregory W. Henry  Francis C. Fekel  Douglas S. Hall 《Monthly notices of the Royal Astronomical Society》1999,308(4):1081-1086

We present BV photometry and simultaneous high-resolution, high signal-to-noise ratio spectroscopy of the newly-discovered γ Doradus variable HR 8330 taken during the 1997 and 1998 observing seasons. We calculate power spectra for the B - and V -band data sets and for the time series defined throughout the observing season at each point across the Fe  ii λ 4508.289 and the Ti  ii λ 4501.278 line profiles to search for periodic variability. Period analysis reveals a single, 2.6-d period in both the photometric and the spectroscopic data, with a 237° phase lag between them. Based on the location of HR 8330 in the HR diagram and the characteristics of its photometric and spectroscopic variations, we conclude that HR  8330 is a bona fide γ Doradus-type pulsating variable.  相似文献   

A spatio-chemical survey of hydrogeothermal springs in Lake Elementaita, Kenya     

Francis Mwaura 《International Journal of Salt Lake Research》1999,8(2):127-138

The hydrochemistry of three areas of geothermal activity in the Lake Elementaita basin were surveyed. The results indicated warm temperatures between 30–40°C, high alkalinity (1,200 mg CaCO₃/l) and specific conductance (4,300–8,100 μS/cm). pH was above 9 with a high concentration of carbonates, chlorides and sulphates. Apart from playing a significant role in the lake chemistry, lacustrine springs provide a significant source of water supply, particularly during the dry season. However, there is a serious lack of scientific information on the hydrogeology and hydrochemistry of the thermal springs.  相似文献   

Depth to the apparent redox potential discontinuity (aRPD) as a parameter of interest in marine benthic habitat quality models     

Travis G. Gerwing  Kieran Cox  Alyssa M. Allen Gerwing  Charmaine N. Carr-Harris  Sarah E. Dudas  Francis Juanes 《国际泥沙研究》2018,33(2):149-156

The usefulness of the apparent redox potential discontinuity (aRPD) in assessments of marine benthic habitat quality was explored at two intertidal mudflats along the north Pacific coast of Canada. Two transects were established at each intertidal site, with three sediment biogeochemistry cores collected from each transect four times over the summer of 2016. Measurements of the sediment pore water dissolved oxygen (DO) content and redox (Eh) conditions were taken at the surface of the core (measured vertically), as well as at increasing depths (1 cm between readings) into the sediment (measured horizontally through predrilled holes in the biogeochemistry corer). While oxic, anoxic, oxidized, and reduced sediment pore water was observed above and below the aRPD, in general, sediment above the aRPD had higher DO content, and higher Eh values than sediment below the aRPD. Therefore, the aRPD depth can be used as a relative indicator of sediment pore water DO and Eh conditions: sediment with a deeper aRPD depth has more available DO, and the pore water has higher Eh values (more oxidized or less reduced) than sediment with a shallower aRPD depth. As such, the aRPD depth is a useful parameter to include in models that assess the quality of marine benthic habitats.  相似文献   

Trouble with Sense of Place in Working Landscapes     

Weston M. Eaton  Francis R. Eanes  Jessica D. Ulrich-Schad  Morey Burnham  Sarah P. Church  J. Gordon Arbuckle 《社会与自然资源》2019,32(7):827-840

The sense of place (SOP) conceptual framework offers theoretical and empirical evidence that links peoples’ multifaceted connections to place(s) to their engagement in pro-environmental and conservation behaviors. The bulk of this research has focused on peoples’ connection to high-amenity places and landscapes. Recent research applies SOP in working landscapes—however, these studies encounter “troubles” that include measurement challenges and mixed results in predicting statistical relationships with conservation outcome variables. As authors of some of these studies, we propose three opportunities and corresponding survey items for developing meaningful SOP measures in future working landscapes research: (1) modify existing SOP dimensions and items to better capture the working landscape dynamics; (2) address how scale may affect behavior and SOP dimensions; and (3) incorporate a conservation ethic dimension into the SOP framework in working lands.  相似文献   

Reclassification of four aubrites as enstatite chondrite impact melts: Potential geochemical analogs for Mercury     

Arya Udry  Zoë E. Wilbur  Rachel R. Rahib  Francis M. McCubbin  Kathleen E. Vander Kaaden  Timothy J. McCoy  Karen Ziegler  Juliane Gross  Christopher DeFelice  Logan Combs  Brent D. Turrin 《Meteoritics & planetary science》2019,54(4):785-810

We present petrologic and isotopic data on Northwest Africa (NWA) 4799, NWA 7809, NWA 7214, and NWA 11071 meteorites, which were previously classified as aubrites. These four meteorites contain between 31 and 56 vol% of equigranular, nearly endmember enstatite, Fe,Ni metal, plagioclase, terrestrial alteration products, and sulfides, such as troilite, niningerite, daubréelite, oldhamite, and caswellsilverite. The equigranular texture of the enstatite and the presence of the metal surrounding enstatite indicate that these rocks were not formed through igneous processes like the aubrites, but rather by impact processes. In addition, the presence of pre‐terrestrially weathered metal (7.1–14 vol%), undifferentiated modal abundances compared to enstatite chondrites, presence of graphite, absence of diopside and forsterite, low Ti in troilite, and high Si in Fe,Ni metals suggest that these rocks formed through impact melting on chondritic and not aubritic parent bodies. Formation of these meteorites on a parent body with similar properties to the EHa enstatite chondrite parent body is suggested by their mineralogy. These parent bodies have undergone impact events from at least 4.5 Ga (NWA 11071) until at least 4.2 Ga (NWA 4799) according to ³⁹Ar‐⁴⁰Ar ages, indicating that this region of the solar system was heavily bombarded early in its history. By comparing NWA enstatite chondrite impact melts to Mercury, we infer that they represent imperfect petrological analogs to this planet given their high metal abundances, but they could represent important geochemical analogs for the behavior and geochemical affinities of elements on Mercury. Furthermore, the enstatite chondrite impact melts represent an important petrological analog for understanding high‐temperature processes and impact processes on Mercury, due to their similar mineralogies, Fe‐metal‐rich and FeO‐poor silicate abundances, and low oxygen fugacity.  相似文献   

Shock‐induced microtextures in lunar apatite and merrillite     

Ana ernok  Lee Francis White  James Darling  Joseph Dunlop  Mahesh Anand 《Meteoritics & planetary science》2019,54(6):1262-1282

Apatite and merrillite are the most common phosphate minerals in a wide range of planetary materials and are key accessory phases for in situ age dating, as well as for determination of the volatile abundances and their isotopic composition. Although most lunar and meteoritic samples show at least some evidence of impact metamorphism, relatively little is known about how these two phosphates respond to shock‐loading. In this work, we analyzed a set of well‐studied lunar highlands samples (Apollo 17 Mg‐suite rocks 76535, 76335, 72255, 78235, and 78236), in order of displaying increasing shock deformation stages from S1 to S6. We determined the stage of shock deformation of the rock based on existing plagioclase shock‐pressure barometry using optical microscopy, Raman spectroscopy, and SEM‐based panchromatic cathodoluminescence (CL) imaging of plagioclase. We then inspected the microtexture of apatite and merrillite through an integrated study of Raman spectroscopy, SEM‐CL imaging, and electron backscatter diffraction (EBSD). EBSD analyses revealed that microtextures in apatite and merrillite become progressively more complex and deformed with increasing levels of shock‐loading. An early shock‐stage fragmentation at S1 and S2 is followed by subgrain formation from S2 onward, showing consistent decrease in subgrain size with increasing level of deformation (up to S5) and finally granularization of grains caused by recrystallization (S6). Starting with 2°–3° of intragrain crystal‐plastic deformation in both phosphates at the lowest shock stage, apatite undergoes up to 25° and merrillite up to 30° of crystal‐plastic deformation at the highest stage of shock deformation (S5). Merrillite displays lower shock impedance than apatite; hence, it is more deformed at the same level of shock‐loading. We suggest that the microtexture of apatite and merrillite visualized by EBSD can be used to evaluate stages of shock deformation and should be taken into account when interpreting in situ geochemically relevant analyses of the phosphates, e.g., age or volatile content, as it has been shown in other accessory minerals that differently shocked domains can yield significantly different ages.  相似文献   

基于砂-粉砂-黏土含量的沉积物命名方法     

王中波 《海洋地质前沿》2006,22(10):33-35

充分描述沉积物需要沉积物的许多性质特征,其中任一种沉积物样品的砂—粉砂—黏土含量比例是固定不变的,因此根据砂—粉砂—黏土的组成来对沉积物分类是非常重要的。砂、粉砂和黏土都有一个沉积物中值粒径划分的固定标准,1/256mm是粉砂和黏土的划分界线,1/16mm是粉砂和砂的划分  相似文献   

Currents in submarine canyon heads off north St. Croix,U.S. Virgin Islands     

Francis P. Shepard  Robert F. Dill 《Marine Geology》1977,24(3):M39-M45

Currents in the heads of two canyons off the north shore of St. Croix, U.S. Virgin Islands are characterized by slow velocity with high-frequency alternations of direction and occasional periods of relatively strong downcanyon flows; the latter occurred during falling tides. The downcanyon flows appear to be density driven by pulses of saline water coming out of either the estuary or harbor located shoreward of the canyon heads.  相似文献