Late Holocene temperature record from southwestern Australia: evidence of global warming from deep boreholes*     

SJ Appleyard 《Australian Journal of Earth Sciences》2013,60(1):161-166

A ground surface temperature history for the last 500 years was created from the inversion of geophysical temperature logs in four deep (?>?1400?m) boreholes on the Blackwood Plateau in southwestern Australia. Modelled temperature changes show close agreement with ground surface temperature histories from elsewhere in the world for this period and indicate that the Blackwood Plateau has experienced a 0.4 K increase in mean temperature between the beginning of the sixteenth century and the 1980s, with more than half of the increase having taken place after 1900. The modelling indicates that the highest temperatures in the region for the last 500 years were recorded during the twentieth century, and that the current rate of temperature change of more than 0.5° K per century is higher than at any other time during this time period.  相似文献   

Palaeogeographic,climatic and tectonic change in southeastern Australia: the Late Neogene evolution of the Murray Basin     

Sandra McLaren  Malcolm W. Wallace  Stephen J. Gallagher  John A. Miranda  Guy R. Holdgate  Laura J. Gow  Ian Snowball  Per Sandgren 《Quaternary Science Reviews》2011,30(9-10):1086-1111

The Murray Basin is a low-lying but extensive intracratonic depocentre in southeastern Australia, preserving an extraordinary record of Late Neogene sedimentation. New stratigraphic and sedimentologic data allow the long-term evolution of the basin to be re-evaluated and suggest a significant role for: (1) tectonism in controlling basin evolution, and (2) progressive and step-wise climatic change beginning in the early Pleistocene. Tectonic change is associated with regional uplift, occurring at approximately the same rate from the early Pliocene until the present day, and possibly associated with changing mantle circulation patterns or plate boundary processes. This uplift led to the defeat and re-routing of the Murray River, Australia’s major continental drainage system. Key to our interpretation is recognition of timing relationships between four prominent palaeogeographic features – the Loxton-Parilla Sands strandplain, the Gambier coastal plain, palaeo megalake Bungunnia and the Kanawinka Escarpment. Geomorphic and stratigraphic evidence suggest that during the Early Pliocene the ancestral Murray River was located in western Victoria, flowing south along the Douglas Depression. Relatively small amounts of regional uplift (<200 m) defeated this drainage system, dramatically changing the palaeogeography of southeastern Australia and forming Plio-Pleistocene megalake Bungunnia. At its maximum extent Lake Bungunnia covered more than 50,000 km², making it one of the largest known palaeo- or modern-lakes in an intracontinental setting. Magnetostratigraphic constraints suggest lake formation c. 2.4 Ma. The formation of Lake Bungunnia influenced the Pliocene coastal dynamics, depriving the coastline of a sediment source and changing the coastal system from a prograding strandline system to an erosional one. Erosion during this period formed the Kanawinka Escarpment, a palaeo sea-cliff and one of the most prominent and laterally extensive geomorphic features in southeastern Australia. Marine sediments c. 800 ka to c. 1.16 Ma represent the time of re-establishment of depositional coastal dynamics and of a permanent outlet for the Murray River. This age range is consistent with our best estimate of the age of the youngest Lake Bungunnia sediments and points towards an early Pleistocene age for the demise of the lake system. The youngest Lake Bungunnia sediment, present on a number of distinct terraces, suggests that progressive, step-wise climatic change played a role in the demise of the lake. However, in order for the ancestral Murray River system to have been able to breach the pre-existing tectonic dam, it is likely that tectonic change and/or temporarily enhanced discharge was also significant. This scenario indicates that the modern Murray River has only been in existence for at most 700 ka.  相似文献   

The uptake and solubility of water in quartz at elevated pressure and temperature     

J. Gerretsen  M. S. Paterson  A. C. McLaren 《Physics and Chemistry of Minerals》1989,16(4):334-342

The uptake of water in quartz at 1.5 GPa total pressure, 1173 K and high water fugacity, over times up to 24 h, has been investigated using a newly developed assembly to prevent microcracking. It is found that the uptake is small, and below the detectability of the presently used technique of infrared spectroscopy and serial sectioning. This observation reflects either a low value for the diffusivity or the solubility or a combination of both, and is in agreement with the observations of Kronenberg et al. (1986) and Rovetta et al. (1986). It brings into question the interpretation of the early experiments on water weakening by Griggs and Blacic (1964) and the recent estimates of the solubility and diffusivity by Mackwell and Paterson (1985). Rults of a combined T.E.M., light-scattering and infrared-spectroscopy investigation of ‘wet’ synthetic quartz before and after heating at 0.1, 300 and 1500 MPa total pressure and 1173 K, strongly suggest that the water in ‘wet’ quartz is mainly in the form of H₂O in inclusions, consistent with the solubility being low, possibly less than 100 H/10⁶Si. From these observations, water-containing inclusions appear to play a major role in the plasticity of quartz, while any role of water in solid solution remains to be clarified.  相似文献   

Aspects of the differences in the erodibility of the waste rock dump and natural surfaces, Ranger Uranium Mine, Northern Territory, Australia   总被引：3，自引：0，他引：3  

SJ Riley 《Applied geography (Sevenoaks, England)》1995,15(4)

Small-scale flume experiments on the waste rock dump of Ranger Uranium Mine, Northern Territory, Australia, show that the unmanaged surface of the dump is 10–100 times more erodible than adjacent natural hillslopes. Silt and clay are preferentially removed and their proportion of the total sediment load is enhanced over their content in surface sediment. There is strong evidence that a low threshold of erosion does not exist and that even the smallest of flows across the waste rock dump can erode and transport some surface material. The erodible dump surface and the preferential removal of silt-clay could degrade ecosystems both on the dump and off-site. Rehabilitation of the waste rock dump will require special attention to erosion and its management.  相似文献   

Distribution of Palaeozoic reworking in the Western Arunta Region and northwestern Amadeus Basin from ⁴⁰Ar/³⁹Ar thermochronology: implications for the evolution of intracratonic basins     

Sandra McLaren  Mike Sandiford†  W. James Dunlap  Ian Scrimgeour‡  Dorothy Close‡  Christine Edgoose‡ 《Basin Research》2009,21(3):315-334

The Centralian Superbasin in central Australia is one of the most extensive intracratonic basins known from a stable continental setting, but the factors controlling its formation and subsequent structural dismemberment continue to be debated. Argon thermochronology of K-feldspar, sensitive to a broad range of temperatures (∼150 to 350 °C), provides evidence for the former extent and thickness of the superbasin and points toward thickening of the superbasin succession over the now exhumed Arunta Region basement. These data suggest that before Palaeozoic tectonism, there was around 5–6 km of sediment present over what is now the northern margin of the Amadeus Basin, and, if the Centralian superbasin was continuous, between 6 and 8 km over the now exhumed basement. ⁴⁰Ar/³⁹Ar data from neoformed fine-grained muscovite suggests that Palaeozoic deformation and new mineral growth occurred during the earliest compressional phase of the Alice Springs Orogeny (ASO) (440–375 Ma) and was restricted to shear zones. Significantly, several shear zones active during the late Mesoproterozoic Teapot Orogeny were not reactivated at this time, suggesting that the presence of pre-existing structures was not the only controlling factor in localizing Palaeozoic deformation. A range of Palaeozoic ages of 440–300 Ma from samples within and external to shear zones points to thermal disturbance from at least the early Silurian through until the late Carboniferous and suggests final cooling and exhumation of the terrane in this interval. The absence of evidence for active deformation and/or new mineral growth in the late stages of the ASO (350–300 Ma) is consistent with a change in orogenic dynamics from thick-skinned regionally extensive deformation to a more restricted localized high-geothermal gradient event.  相似文献   

Ambiguous Hydraulic Heads and 14C Activities in Transient Regional Flow     

Franklin W. Schwartz  Edward A. Sudicky  Robert G. McLaren  Young-Jin Park  Matthew Huber  Mick Apted 《Ground water》2010,48(3):366-379

A regional flow and transport model is used to explore the implications of significant variability in Pleistocene and Holocene climates on hydraulic heads and ¹⁴C activity. Simulations involve a 39 km slice of the Death Valley Flow System through Yucca Mountain toward the Amargosa Desert. The long-time scale over which infiltration has changed (tens-of-thousands of years) is matched by the large physical extent of the flow system (many tens-of-kilometers). Estimated paleo-infiltration rates were estimated using a juniper pollen percentage that extends from the last interglacial (LIG) period (approximately 120 kyrbp) to present. Flow and ¹⁴C transport simulations show that groundwater flow changes markedly as a function of paleoclimate. At the last glacial maximum (LGM, 21 kyrbp), the recharge to the flow system was about an order-of-magnitude higher than present, and water table was more than 100 m higher. With large basin time constants, flow is complicated because hydraulic heads at a given location reflect conditions of the past, but at another location the flow may reflect present conditions. This complexity is also manifested by processes that depend on flow, for example ¹⁴C transport. Without a model that accounts for the historical transients in recharge for at least the last 20,000 years, there is no simple way to deconvolve the ¹⁴C dates to explain patterns of flow.  相似文献   

Recent developments at Canada-France-Hawaii Telescope   总被引：1，自引：0，他引：1  

Robert McLaren 《Astrophysics and Space Science》1989,160(1-2):255-262

Recent developments at CFHT are described with particular emphasis in the following areas: image quality, techniques for high-resolution imaging, computers, and communications.Paper presented at the Symposium on the JNLT and Related Engineering Development, Tokyo, November 29–December 2, 1988.  相似文献   

A comparison of the enzyme fluorometric and the peroxyoxalate chemiluminescence methods for measuring H2O2     

N. Beltz  W. Jaeschke  G. L. Kok  S. N. Gitlin  A. L. Lazrus  S. McLaren  D. Shakespeare  V. A. Mohnen 《Journal of Atmospheric Chemistry》1987,5(3):311-322

During September 25 to October 28, 1985, the enzyme fluorometric (Lazrus et al., 1985) and the peroxyoxalate chemiluminescence (Klockow and Jacob, 1986; Jaeschke, 1986) techniques for analyzing H₂O₂ were compared in laboratory studies at the National Center for Atmospheric Research in Boulder, Colorado, U.S.A. and under field conditions at the Whiteface Mt. field station of the Atmospheric Sciences Research Center, Albany, New York, U.S.A. Both methods showed excellent agreement, with a maximum deviation of ±5%. Only at unusually high concentrations of some potential atmospheric species could slight interferences be observed. During the experiments the detection limits were 1.3×10^-8 mol/l (0.44 ppbm) of H₂O₂ for the fluorometric instrument and 4×10^-8 mol/l (1.36 ppbm) of H₂O₂ for the chemiluminescence instrument. For the chemiluminescence technique, the response to methylhydroperoxide was approximately 80-fold less than that to an equivalent concentration of H₂O₂.  相似文献   

TEM investigation of a microcline from a nepheline syenite     

K. L. Smith  A. C. McLaren 《Physics and Chemistry of Minerals》1983,10(2):69-76

Chess-board (“tiled”) microcline crystals from a nepheline-bearing syenite from Ilimaussaq, W. Greenland, were investigated using transmission electron microscopy (TEM) and were found to consist of a mosaic of slightly misoriented domains, which bear no obvious relationship to the optical microstructure. Part of the misorientation of most pairs of neighbouring domains involves a small rotation about c. However, some are related to adjacent domains by the albite twin law, the pericline law, or diagonal association. This microcline could have crystallized with triclinic symmetry which could account for the differences between the microstructure of this microcline and M-twinned microcline. Metasomatism may explain both the optical microscope and TEM scale structures of this microcline. Examination of the electron diffraction patterns of areas of microcline which contain both diagonally associated and twinned domains draw attention to the fact that each of the few orientations in an M-twinned crystal is related to one of the other orientations by diagonal association. The formation of common cross-hatch twinned microstructures are discussed with reference to diagonal association.  相似文献