Denudational isostatic rebound of intraplate highlands: The lachlan river valley,Australia     

Paul Bishop  Roderick Brown 《地球表面变化过程与地形》1992,17(4):345-360

A range of evidence from the Lachlan valley in the southeast Australian highlands is consistent with Neogene isostatic rebound in response to denudational unloading. This evidence is found along the inland edge of the highlands in the transition zone between the highlands proper and the Lachlan's inland alluviated valley and the intracratonic Murray Basin. The amounts and rates of uplift indicated by offsets of suballuvium bedrock profiles and the long profiles of Tertiary valley-filling basalts are consistent with modelling of denudational rebound using known rates of highland denudation and basinal sedimentation, and reasonable crustal properties. The modelling shows that weak to moderately strong strong lithosphere (effective elastic thickness, T_e = 1-25 km) and strong lithosphere (T_e = 100 km) are all consistent with the observed amounts of rebound. Strong lithosphere must be broken, however, to be consistent with the field data. Even in the Australian setting, which is characterized by very low rates of denudation, isostatic rebound in response to denudational unloading must be a significant factor in maintaining highland elevation and must be incorporated in models of long-term landscape evolution. It would be expected that denudational isostatic rebound would be an even more significant component of long-term landscape evolution in areas of higher denudation rates.  相似文献   

Balanced Sediment Fluxes in Southern California’s Mediterranean-Climate Zone Salt Marshes   总被引：1，自引：0，他引：1  

Jordan A. Rosencranz  Neil K. Ganju  Richard F. Ambrose  Sandra M. Brosnahan  Patrick J. Dickhudt  Glenn R. Guntenspergen  Glen M. MacDonald  John Y. Takekawa  Karen M. Thorne 《Estuaries and Coasts》2016,39(4):1035-1049

Salt marsh elevation and geomorphic stability depends on mineral sedimentation. Many Mediterranean-climate salt marshes along southern California, USA coast import sediment during El Niño storm events, but sediment fluxes and mechanisms during dry weather are potentially important for marsh stability. We calculated tidal creek sediment fluxes within a highly modified, sediment-starved, 1.5-km² salt marsh (Seal Beach) and a less modified 1-km² marsh (Mugu) with fluvial sediment supply. We measured salt marsh plain suspended sediment concentration and vertical accretion using single stage samplers and marker horizons. At Seal Beach, a 2014 storm yielded 39 and 28 g/s mean sediment fluxes and imported 12,000 and 8800 kg in a western and eastern channel. Western channel storm imports offset 8700 kg exported during 2 months of dry weather, while eastern channel storm imports augmented 9200 kg imported during dry weather. During the storm at Mugu, suspended sediment concentrations on the marsh plain increased by a factor of four; accretion was 1–2 mm near creek levees. An exceptionally high tide sequence yielded 4.4 g/s mean sediment flux, importing 1700 kg: 20 % of Mugu’s dry weather fluxes. Overall, low sediment fluxes were observed, suggesting that these salt marshes are geomorphically stable during dry weather conditions. Results suggest storms and high lunar tides may play large roles, importing sediment and maintaining dry weather sediment flux balances for southern California salt marshes. However, under future climate change and sea level rise scenarios, results suggest that balanced sediment fluxes lead to marsh elevational instability based on estimated mineral sediment deficits.  相似文献   

Metropolitan land-use patterns by economic function: a spatial analysis of firm headquarters and branch office locations in Australian cities   总被引：1，自引：0，他引：1  

Thomas Sigler  Glen Searle  Kirsten Martinus  Matthew Tonts 《Urban geography》2016,37(3):416-435

This paper develops a comparative means by which to understand metropolitan spatial structure through the dynamics of economic activities. Clustering and suburbanization have been key processes within the contemporary urban landscape, but few scholarly accounts have systematically merged the two to explain the geographies of economic activity. Using firm location as a variable to discern sector- and industry-based locational requirements, we explore land-use and economic activity in Australia’s five largest metropolitan areas. Drawing upon the respective headquarters and branch office locations of a set of publically traded firms, we seek to establish general spatial patterns across Australian cities using two proxy measures for clustering and suburbanization, being well-established drivers of firm locational choice. Despite the complexity that post-industrial and suburbanizing processes add to metropolitan land-use patterns, we contend that certain patterns exist that can be generalized from one context to another across urban space, and that certain emerging trends such as the development of CBD-fringe precincts merit greater attention.  相似文献   

Effects of Recent Instability on Cultivated Area Along the Euphrates River in Iraq     

Glen R. Gibson  Nicole L. Taylor  Nolan C. Lamo  Jason K. Lackey 《The Professional geographer》2017,69(2):163-176

We used MODIS NDVI data to determine whether there was a significant change in cultivated area along the Euphrates River in Iraq after the Iraq War compared to before and during the war. Results revealed that mean cultivated area was largest during the pre–Iraq War period (2000–2003) with 99,115 Mha, reduced some during the early Iraq War period (2003–2006) to 83,480 Mha, reduced even further during the late Iraq War period (2007–2011) to 53,813 Mha due to drought, and increased slightly during the post–Iraq War period (2012–2015) to 69,161 Mha, although not returning to previous highs of the pre–Iraq War or early Iraq War periods. Statistical analysis with the Kruskal–Wallis test revealed that the small cultivated area during the post–Iraq War period was more closely related to the late Iraq War and drought period than previous periods, indicating that recent instability, such as political turmoil following the departure of U.S. troops, violent militant extremism, lack of economic investment, and environmental degradation, has had a similar effect on cultivated area as a devastating drought.  相似文献   

Interannual variability of the Kuroshio intrusion in the South China Sea   总被引：13，自引：1，他引：13  

Michael J. Caruso  Glen G. Gawarkiewicz  Robert C. Beardsley 《Journal of Oceanography》2006,62(4):559-575

The interannual variability of intrusions of the Kuroshio into the South China Sea (SCS) is investigated using satellite remote sensing data supported by in-situ measurements. The mesoscale circulation of the SCS is predominantly wind-forced by the northeast winter and southwest summer monsoons. Although the region has been studied extensively, considerable uncertainty remains about the annual and interannual mesoscale nature of the circulation. The frequency and characteristics of Kuroshio intrusions and their effect on circulation patterns in the northeast SCS are also not well understood. Satellite observations of Sea Surface Temperature (SST) from the Tropical Rainfall Measuring Mission (TRMM) and the Advanced Very High Resolution Radiometer (AVHRR) and Sea Surface Height Anomalies (SSHA) from TOPEX/ Poseidon for the period 1997–2005 are used here to analyze the annual and interannual variability in Kuroshio intrusions and their effects on the region. Analysis of SST and SSHA shows the formation and characteristics of intrusions vary considerably each year. Typically, the intrusion occurs in the central region of Luzon Strait and results in an anticyclonic circulation in the northeastern SCS. However, in some years, the intrusion is located in the northern portion of Luzon Strait and a cyclonic intrusion results. Wind stress and wind stress curl derived from the National Aeronautics and Space Administration (NASA) QuikSCAT satellite scatterometer are used to evaluate the relationship between wind stress or wind stress curl and the presence of winter Kuroshio intrusions into the SCS.  相似文献   

o,p′-DDT induction of vitellogenesis and its inhibition by tamoxifen in Nile tilapia (Oreochromis niloticus)     

Olga Leaos-Castaeda  Glen Van Der Kraak  Andrea Lister  Raúl Sim-Alvarez  Gerardo Gold-Bouchot 《Marine environmental research》2002,54(3-5)

In order to investigate the mechanism by which o,p′-DDT disrupts endocrine functioning of Nile tilapia in vivo, the estrogenicity of o,p′-DDT was investigated in conjunction with 17β-estradiol (E₂) and tamoxifen. Mature, male tilapia were treated intraperitoneally with o,p′-DDT (60 mg/kg, one dose) or E₂ (5 mg/kg, four doses) in the presence or absence of tamoxifen (5 mg/kg, six doses) for 12 days and then plasma vitellogenin (Vtg) (measured as alkaline-labile phosphorous), E₂, and testosterone (T) were measured. Vtg levels were increased dramatically by E₂ (1744±171 μg/ml) and moderately by o,p′-DDT (82±15 μg/ml) compared with controls (23±3.5 μg/ml). Tamoxifen alone had no effect on Vtg production, but inhibited both E₂ and o,p′-DDT stimulated vitellogenesis. T levels were reduced with E₂ administration (1688±383 pg/ml) and declined further with the combined treatment of E₂ and tamoxifen (281±70 pg/ml), compared with controls (6558±1438 pg/ml). Tamoxifen or o,p′-DDT alone did not affect T levels, but their combined treatment did (2069±647 pg/ml). The results of this study suggest that o,p′-DDT is weakly estrogenic in male tilapia, and that this activity may be mediated through the estrogen receptor.  相似文献   

Structure of the Cobar Basin,New South Wales,based on seismic reflection profiling     

R. A. Glen  B. J. Drummond  B. R. Goleby  D. Palmer  K. D. Wake‐Dyster 《Australian Journal of Earth Sciences》2013,60(4):341-352

The Cobar Basin in central western New South Wales is a mineral‐rich Early Devonian basin typical of those that characterize the Siluro‐Devonian history of the Lachlan Orogen of southeastern Australia. One hundred and seventy kilometres of seismic profiling in three lines across the basin have shown it to be asymmetrical in shape with an east‐dipping western margin that is steeper than the moderately west‐dipping eastern margin. Maximum basin thickness is around 6 km, but there are significant thickness changes, especially from south to north, which reflect the effect of synsedimentary faulting. Seismic profiling suggests that the basin deformed by thin‐skinned tectonics; postulated strike‐slip effects were not visible on the sections. The seismic profiling has, for the first time, imaged the western synrift basin margin which is generally not exposed. Strain variations during deformation along this edge were taken up by the formation of a major jog ('dog‐leg') which has propagated into the basin as a tear fault. Intrabasinal tears, as well as thrusts, which link into one or more detachments, provide potential pathways for mineralizing fluids during basin inversion.  相似文献   

The ARIEL Instrument Control Unit design     

M. Focardi  E. Pace  M. Farina  A. M. Di Giorgio  J. Colomé Ferrer  I. Ribas  C. Sierra Roig  L. Gesa Bote  J. C. Morales  J. Amiaux  C. Cara  J. L. Augurés  E. Pascale  G. Morgante  V. Da Deppo  M. Pancrazzi  V. Noce  S. Pezzuto  M. Frericks  F. Zwart  G. Bishop  K. Middleton  P. Eccleston  G. Micela  G. Tinetti 《Experimental Astronomy》2018,45(1):1-20

In this paper we present the electromagnetic modeling and beam pattern measurements of a 16-elements ultra wideband sparse random test array for the low frequency instrument of the Square Kilometer Array telescope. We discuss the importance of a small array test platform for the development of technologies and techniques towards the final telescope, highlighting the most relevant aspects of its design. We also describe the electromagnetic simulations and modeling work as well as the embedded-element and array pattern measurements using an Unmanned Aerial Vehicle system. The latter are helpful both for the validation of the models and the design as well as for the future instrumental calibration of the telescope thanks to the stable, accurate and strong radio frequency signal transmitted by the UAV. At this stage of the design, these measurements have shown a general agreement between experimental results and numerical data and have revealed the localized effect of un-calibrated cable lengths in the inner side-lobes of the array pattern.  相似文献   

Water storage dynamics in a till hillslope: the foundation for modeling flows and turnover times          下载免费PDF全文

Nino Amvrosiadi  Jan Seibert  Thomas Grabs  Kevin Bishop 《水文研究》2017,31(1):4-14

Studies on hydrology, biogeochemistry, or mineral weathering often rely on assumptions about flow paths, water storage dynamics, and transit times. Testing these assumptions requires detailed hydrometric data that are usually unavailable at the catchment scale. Hillslope studies provide an alternative for obtaining a better understanding, but even on such well‐defined and delimited scales, it is rare to have a comprehensive set of hydrometric observations from the water divide down to the stream that can constrain efforts to quantify water storage, movement, and turnover time. Here, we quantified water storage with daily resolution in a hillslope during the course of almost an entire year using hydrological measurements at the study site and an extended version of the vertical equilibrium model. We used an exponential function to simulate the relationship between hillslope discharge and water table; this was used to derive transmissivity profiles along the hillslope and map mean pore water velocities in the saturated zone. Based on the transmissivity profiles, the soil layer transmitting 99% of lateral flow to the stream had a depth that ranged from 8.9 m at the water divide to under 1 m closer to the stream. During the study period, the total storage of this layer varied from 1189 to 1485 mm, resulting in a turnover time of 2172 days. From the pore water velocities, we mapped the time it would take a water particle situated at any point of the saturated zone anywhere along the hillslope to exit as runoff. Our calculations point to the strengths as well as limitations of simple hydrometric data for inferring hydrological properties and water travel times in the subsurface.  相似文献   

What do we know about the labour market for seafarers?: A view from the UK     

David Glen 《Marine Policy》2008

This paper considers the evidence that exists on the global demand and supply of seafarers, and their age profiles. New information on the age profiles of deck and engine officers is presented, drawn from records held by the UK Maritime and Coastguard Agency. Detailed age profiles for certain countries are constructed and compared with that of the UK, as well as with estimates published elsewhere. Using the data derived from the MCA, it is shown that there is a significant positive correlation between the age profiles of seafarer supplying countries and their level of economic development, as measured by GDP per capita. This evidence is consistent with the view that the future supply of seafaring officers will increasingly be oriented towards countries at lower levels of development, as the existing pool of highly qualified officers from traditional maritime countries continues to diminish.  相似文献