Definition and global correlation of the Santonian-Campanian boundary     

A.S. Gale  P. Montgomery  W.J. Kennedy  J.M. Hancock  J.A. Burnett  J.M. McArthur 《地学学报》1995,7(6):611-622

Review of biostratigraphical evidence from different regions shows that criteria used by workers on various marine fossil groups to define the Santonian-Campanian boundary differ considerably in relative age and position. Probably the most widely recognizable of these criteria is the extinction of the distinctive crinoid Marsupites testudinarius (North America, Europe, Asia, north Africa, Australia), which, coincides exactly with two separate definitions of the boundary - appearances of the ammonite Placenticeras bidorsatum and the belemnite Gonioteuthis granulataquadrata - and may also coincide with a third - entry of the planktic foraminiferan Globotruncana elevata. A comparison of evidence from upper Santonian and lower Campanian successions in widely separated regions allows us to place a series of important biostratigraphical markers in correct order. Defining the boundary at the extinction of M. testudinarius corresponds to a ⁸⁷Sr/⁸⁶Sr of 0.707479, and a small positive excursion in δ¹³C. The base of magnetochron 33R, generally considered to coincide with, or fall just above the base of the Campanian, is shown to lie within the upper Santonian Uintacrinus socialis Zone.  相似文献   

Preface: Tectonics at the 26th IGC, Paris     

P.L. Hancock 《Journal of Structural Geology》1981,3(4):345

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Constraints on cosmological parameters from recent measurements of cosmic microwave background anisotropy     

Hancock  Rocha  Lasenby  & Gutiérrez 《Monthly notices of the Royal Astronomical Society》1998,294(1):L1-L6

A key prediction of cosmological theories for the origin and evolution of structure in the Universe is the existence of a 'Doppler peak' in the angular power spectrum of cosmic microwave background (CMB) fluctuations. We present new results from a study of recent CMB observations which provide the first strong evidence for the existence of a 'Doppler peak' localized in both angular scale and amplitude. This first estimate of the angular position of the peak is used to place a new direct limit on the curvature of the Universe, corresponding to a density of Ω = 0.7^+0.8_−0.5, consistent with a flat universe. Very low-density 'open' universe models are inconsistent with this limit unless there is a significant contribution from a cosmological constant. For a flat standard cold dark matter dominated universe we use our results in conjunction with big bang nucleosynthesis constraints to determine the value of the Hubble constant as H ₀ = 30 − 70 km s⁻¹ Mpc⁻¹ for baryon fractions Ω_b = 0.05 to 0.2. For H ₀ = 50 km s⁻¹ Mpc⁻¹ we find the primordial spectral index of the fluctuations to be n  = 1.1 ± 0.1, in close agreement with the inflationary prediction of n  ≃ 1.0.  相似文献   

10-GHz Tenerife cosmic microwave background observations at 8° resolution and their analysis using a new maximum entropy method     

Jones  Hancock  Lasenby  Davies  Gutiérrez  Rocha  Watson  & Rebolo 《Monthly notices of the Royal Astronomical Society》1998,294(4):582-594

The complete set of data from the Tenerife 10-GHz (8° FWHM) twin-horn, drift scan experiment is described. These data are affected by both long-term atmospheric baseline drifts and short-term noise. A new maximum entropy procedure, utilizing the time invariance and spatial continuity of the astronomical signal, is used to achieve a clean separation of these effects from the astronomical signal, and to deconvolve the effects of the beam-switching. We use a fully positive/negative algorithm to produce two-dimensional maps of the intrinsic sky fluctuations. Known discrete sources and Galactic features are identified in the deconvolved map. The data from the 10-GHz experiment, after baseline subtraction with MEM, are then analysed using conventional techniques, and new constraints on Galactic emission are made.  相似文献   

Geochemistry and extractable Fe and Al in cold‐temperature soils of northwestern Siberia     

William C. Mahaney  Volli Kalm  Ronald G. V. Hancock  Fred Michel  Barbara Kapran 《第四纪科学杂志》2010,25(2):178-189

The concentrations of major, minor and trace elements in three Cryosols from northwestern Siberia were analysed to determine profiles of geochemical uniformity, element mobility and the release and build‐up of extractable Fe and Al. The scope of this study involves weathering processes over all or part of the Lateglacial to the Holocene Epoch (<10 ka) in a cold environment. Iron and Al extracts are investigated to elicit information regarding profile age and palaeoclimate. ‘Free’ iron (Fe_d) relative to total Fe increases in the Ah + Bw horizons compared with the lower horizons, where oxidation is weaker. Low total Fe reflects reworked felsic deltaic and shallow marine deposits from the Permian to the early Tertiary, thereafter emplaced by episodic flooding of glacial meltwater from the Arctic Urals and/or the Kara Sea Ice Sheet. Organically complexed Al (Al_p), uniformly low in all soils, nevertheless shows trends indicating some downward movement, a rather unique occurrence in Arctic tundra soils. As indicated by the slow increase of oxihydrites, it may not be realistic to estimate the age of a profile by its physical characteristics. However, it appears possible to determine broad age ranges from the isotopic composition of water in soils. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Radium and radon radioisotopes in regional groundwater, intertidal groundwater, and seawater in the Adelaide Coastal Waters Study area: Implications for the evaluation of submarine groundwater discharge     

Sbastien Lamontagne  Corinne Le Gal La Salle  Gary J. Hancock  Ian T. Webster  Craig T. Simmons  Andrew J. Love  Julianne James-Smith  Anthony J. Smith  Jochen Kmpf  Howard J. Fallowfield 《Marine Chemistry》2008,109(3-4):318

The input of groundwater-borne nutrients to Adelaide's (South Australia) coastal zone is not well known but could contribute to the ongoing decline of seagrass in the area. As a component of the Adelaide Coastal Waters Study (ACWS), the potential for using the radium quartet (²²³Ra, ²²⁴Ra, ²²⁶Ra and ²²⁸Ra) and ²²²Rn to evaluate submarine groundwater discharge (SGD) was evaluated. Potential isotopic signatures for SGD were assessed by sampling groundwater from three regional aquifers potentially contributing SGD to the ACWS area. In addition, intertidal groundwater was sampled at two sand beach sites. In general, the regional groundwaters were enriched in long-lived Ra isotopes (²²⁶Ra and ²²⁸Ra) and in ²²²Rn relative to intertidal groundwater. Radium activity (but not ²²²Rn activity) was positively correlated to salinity in groundwater from one of the regional aquifers and in intertidal groundwater. Radium isotope ratios (²²³Ra/²²⁶Ra, ²²⁴Ra/²²⁶Ra and ²²⁸Ra/²²⁶Ra) were less variable than individual Ra isotope activities within potential SGD sources. Recirculated seawater (estimated from the intertidal groundwater samples with seawater-like salinities) also had distinctly higher Ra isotope ratios than the regional groundwaters. The activities for all radioisotopes were relatively low in seawater. The activity of the short-lived ²²³Ra and ²²⁴Ra were highest at the shoreline and declined exponentially with distance offshore. In contrast, ²²⁸Ra and ²²⁶Ra activities had a weak linear declining trend with distance offshore. Rn-222 activity was at or near background in all seawater samples. The pattern of enrichment in short-lived Ra isotopes and the lack of ²²²Rn in seawater suggest that seawater recirculation is the main contributor to SGD in the ACWS area. Preliminary modeling of the offshore flux of ²²⁸Ra and ²²⁶Ra suggest that the SGD flux to the ACWS area ranges between 0.2 and 3 · 10^− 3 m³ (m of shoreline)^− 1 s^− 1.  相似文献   

The use of digital elevation models in the identification and characterization of catchments over different grid scales     

G. R. Hancock 《水文研究》2005,19(9):1727-1749

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Michael Robert House (1930-2002) and the start of Devonian cyclostratigraphy     

Jake M. Hancock 《Proceedings of the Geologists' Association. Geologists' Association》2003,114(3):271-274

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Strontium isotope stratigraphy in the Late Cretaceous: intercontinentaI correlation of the Campanian/ Maastrichtian boundary     

J.M. McArthur  W.J. Kennedy  A.S. Gale  M.F. Thirlwall  M. Chen  J. Burnett  J.M. Hancock 《地学学报》1992,4(3):385-393

In the Boreal Chalk of northwestern Europe the base of the Maastrichtian Stage is defined by entry of the belemnite Belemnella . In the Kronsmoor section, in northwestern Germany, which is a standard section for the European Chalk, ⁸⁷Sr/⁸⁶Sr at the Campanian/ Maastrichtian (C/M) boundary is 0.707723±9 (10). An isotopic correlation of this boundary to the US Western Interior, for which a highly refined cephalopod biostratigraphy exists, suggests that this boundary, as defined at Kronsmoor, occurs within the Baculites jenseni zone. This correlationagrees with the latest placement based on biostratigraphic criteria. On⁸⁷Sr/⁸⁶Srcriteria the boundary at Kronsmoor correlates to the English Chalk at Trunch, Norfolk, UK, at a level 3.5 m lower than its position based on biostratigraphic criteria.
At Kronsmoor, ⁸⁷Sr/⁸⁶Sr increases in a quasi-linear manner through much of the section, suggesting that, averaged over intervals of 1 Myr, the gross sedimentation rate and temporal rate of change of ⁸⁷Sr/⁸⁶Sr were approximately constant through the section. For US samples, zonally-plotted values of ⁸⁷Sr/⁸⁶Sr define a quasi-linear trend, which suggests a moderate uniformity of zonal duration from the Baculites compressus zone (73.2±0.7 Ma, 10) to the Baculites grandis zone (70.1±0.7 Ma, 10).  相似文献   

Wind-Tunnel Simulation of the Wake of a Large Wind Turbine in a Stable Boundary Layer: Part 2, the Wake Flow   总被引：1，自引：1，他引：0  

Philip E. Hancock  Frauke Pascheke 《Boundary-Layer Meteorology》2014,151(1):23-37

Measurements have been made in the wake of a model wind turbine in both a neutral and a stable atmospheric boundary layer, in the EnFlo stratified-flow wind tunnel, between 0.5 and 10 rotor diameters from the turbine, as part of an investigation of wakes in offshore winds. In the stable case the velocity deficit decreased more slowly than in the neutral case, partly because the boundary-layer turbulence levels are lower and the consequentially reduced level of mixing, an ‘indirect’ effect of stratification. A correlation for velocity deficit showed the effect of stratification to be the same over the whole of the measured extent, following a polynomial form from about five diameters. After about this distance (for the present stratification) the vertical growth of the wake became almost completely suppressed, though with an increased lateral growth; the wake in effect became ‘squashed’, with peaks of quantities occurring at a lower height, a ‘direct’ effect of stratification. Generally, the Reynolds stresses were lower in magnitude, though the effect of stratification was larger in the streamwise fluctuation than on the vertical fluctuations. The vertical heat flux did not change much from the undisturbed level in the first part of the wake, but became much larger in the later part, from about five diameters onwards, and exceeded the surface level at a point above hub height.  相似文献