In situ cosmogenic exposure ages from the Isle of Skye,northwest Scotland: implications for the timing of deglaciation and readvance from 15 to 11 ka     

David Small  Vincent Rinterknecht  William Austin  Derek Fabel  Maria Miguens‐Rodriguez  Sheng xu 《第四纪科学杂志》2012,27(2):150-158

We present 10 in situ cosmogenic exposure ages from two moraines on the Isle of Skye. The Strollamus medial moraine was deposited during deglaciation of the Devensian ice sheet and yields a mean exposure age from five samples of 14.3 ± 0.9 ka. The moraine age indicates that a significant ice mass existed on Skye at the time of a regional readvance recorded in Wester Ross, northwest Scotland. Taken at face value the ages suggest that deglaciation did not occur until well into Greenland Interstade 1. The Slapin moraine represents the local limit of the Loch Lomond Readvance (LLR) and yields a mean exposure age from five samples of 11.5 ± 0.7 ka, which is consistent with deposition relating to the LLR. These ages suggest that the maximum extent may have been reached late in the stadial and that some glaciers may have remained active until after the climatic amelioration that marks its end. This scenario is considered unlikely given the nature of the climate during this period, which leads us to call for a locally calibrated production rate. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Estimating long-term soil respiration rates from carbon isotopes occluded in gibbsite     

Paul A. Schroeder  Jason C. Austin  John F. Dowd 《Geochimica et cosmochimica acta》2006,70(23):5692-5697

Carbon occluded in the soil gibbsite crystal structure at the Panola Mountain Research Watershed, Georgia, U.S. is presumed to be in isotopic equilibrium with the CO₂ respired from soil organics by microbes and plant roots. Fitting of the stable carbon isotopic data to a Fickian diffusion-based depth function results in an estimate of 47 gC m⁻² y⁻¹ for the long-term soil respiration rate. A numerical model that includes depth-dependent production and diffusion terms results in estimates of 28-12 gC m⁻² y⁻¹. These values range from 15 to 50 times less than the average of modern values for mixed deciduous forests in wet temperate climates. This disparity has several implications for our understanding of the geologic record of climate change, which include: (1) evidence for a cooler and seasonally drier climate during the mid-Holocene in the southeastern U.S., or (2) fluxes of carbon from the soil pool as recorded by soil mineral proxies (i.e., long-term soil respiration rates) under estimate atmosphere annual carbon flux measurements (i.e., short-term measures), and (3) the need to refine soil respiration models used to relate paleosol stable carbon isotopic measurements to paleo-atmospheric estimates.  相似文献   

Small ion concentrations in and near clouds and fogs     

Austin W. Hogan  James R. Hickman 《Pure and Applied Geophysics》1965,60(1):176-182

Summary A mobile small ion and condensation nuclei laboratory was used to study small ion concentrations in and near orographic clouds, low cloud bases, and fogs. It was found that these areas of diminished visibility exist in a conductivity well, characterized by a small ion concentration of less than 200 small ions per cm³, surrounded by an area of increasing small ion concentration, until the concentration exceeds 400 small ions per cm³ 500 to 1000 feet below the base of the cloud. It was also observed that small ion concentration increases during the dissipation of fog, and oscillates with the passage of large patches of drifting fog.  相似文献   

Gulf of Mexico,ocean-color surface-truth measurements     

R. W. Austin 《Boundary-Layer Meteorology》1980,18(3):269-285

In October 1977, a major remote sensing experiment was conducted in the Gulf of Mexico, in preparation for the launch of NIMBUS-7 which carried the Coastal Zone Color Scanner. Two major vessels obtained surface-truth measurements, while two jet aircraft at altitudes of 12.5 and 19.5 km obtained images of the surrounding ocean in 10 spectral bands. Measurements obtained in the surface water from the NOAA vessel Researcher of the spectral downwelling irradiances, upwelling radiances, attenuation and scattering properties are described.  相似文献   

Zinc and copper levels in Belfast Lough     

M.S. McGrath  J. Austin 《Marine pollution bulletin》1979,10(3):86-88

A survey of dissolved zinc, copper, oxygen and biochemical oxygen demand in Belfast Lough has been carried out. Zinc and to a lesser extent copper occur at elevated levels compared with a non-industrialized area of the Irish Sea. Zinc levels are particularly high in the marginal waters of the north shore of the lough. Dissolved oxygen and biochemical oxygen demand levels indicate that pollution of the lough by oxygendemanding wastes is not a serious problem.  相似文献   

Book reviews     

Vecchione  Michael  Maples  Robert  Williams  Austin B.  Anderson  Franz E.  Herrgesell  Perry L. 《Estuaries and Coasts》1984,7(3):265-268

Estuaries and Coasts -  相似文献   

Strain localization in the Morcles nappe (Helvetic Alps, Switzerland)     

Nicholas Austin  Brian Evans  Marco Herwegh  Andreas Ebert 《Swiss Journal of Geoscience》2008,101(2):341-360

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Compositional variability of ice‐rafted debris in Heinrich layers 1 and 2 on the northwest European continental slope identified by environmental magnetic analyses     

John Walden  Emilie Wadsworth  William E. N. Austin  Clare Peters  James D. Scourse  Ian R. Hall 《第四纪科学杂志》2007,22(2):163-172

The composition of ice‐rafted debris (IRD) within a sediment core from the European continental slope (core OMEX‐2K; 49° 5′ N, 13° 26′ W) has been examined using environmental magnetic analyses. The data demonstrate compositional variability of the IRD within Heinrich layers 2 (H2) and 1 (H1) and these differences are most readily explained by changes in the contribution of different IRD sources to the core site. Some IRD within the main Heinrich layers show magnetic signatures that are similar to IRD derived from the Laurentide ice sheet found in cores from within the main North Atlantic IRD‐belt. In contrast, other IRD‐rich layers, both prior to and within the main Heinrich layers, demonstrate different magnetic behaviour, suggesting a contribution from a non‐Laurentide sourced IRD, most likely derived from ice streams discharging from northeast Atlantic ice sheets such as the British and Fennoscandian ice sheets. These data are consistent with published compositional data from the same core and, given the rapid, highly sensitive and non‐destructive nature of the method, suggest that environmental magnetic analysis has considerable potential for characterising IRD materials within Heinrich layers for the purposes of defining provenance. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Fine-scale acoustic tomographic imaging of shallow water sediments     

Dezhang Chu Dajun Tang Austin  T.C. Hinton  A.A. Arthur  R.I.  Jr. 《Oceanic Engineering, IEEE Journal of》2001,26(1):70-83

In acoustic tomographic system capable of performing in situ two-dimensional (2D) acoustic imaging of shallow water sediments is described. This system is capable of resolving inhomogeneities greater than 10 cm and differentiating sound-speed variations greater than 2%, A tomographic inversion is performed in a 2D vertical slice of about 1 m ² (1 m×1 m) using three identical probes, with each consisting of 70 evenly distributed transducers. In normal deployments, two of the probes are oriented vertically and are separated by about 1 meter, and the third is positioned horizontally right above the two vertical probes. The additional horizontal probe greatly improves the horizontal resolution of the system compared to conventional crosshole tomographic setups. Numerical simulations are performed to evaluate the influences of arrival time detection error and transducer position error on the performance of the tomography system. For an arrival time of 500 ns (standard deviation) and a position error of 4 mm (standard deviation), sound-speed anomalies of greater than 0.8% can be correctly predicted near the upper portion (close to the horizontal probe) and are resolvable near the lower portion. A controlled laboratory experiment was conducted to evaluate the performance of the system. The location of a polyurethane block (Conap EN22) used as a known target is correctly predicted while the inverted sound speed is about 9% lower than that from its actual value. Field data taken from a saturated muddy site are presented and analyzed. The inverted mean sound speed and attenuation are about 1480 ms^-1 and 20 dBm^-1, respectively  相似文献   

Modelling Holocene tides on the NW European continental shelf     

Roger M. Austin 《地学学报》1991,3(3):276-288

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