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1.
Kevin Kiernan 《The Australian geographer》1990,21(1):1-17
Comparison of the degree of post‐depositional erosion and weathering to which different landforms and sediments have been subject over time provides a valuable aid to age differentiation of Quaternary deposits. A variety of parameters, including erosional modification both of depositional and older erosional landforms, the weathering of surface clasts and the weathering of subsurface clasts and matrix, has proven useful to Quaternary workers. However, time is only one of a number of factors that control the amount of weathering and erosion that occurs at a site. Examples from the glacial deposits of Tasmania show that if results useful for dating are to be obtained, it is essential to minimise the influence of other factors which may obscure a time‐dependent sequence. 相似文献
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Antarctic polar deserts can be of considerable scientific interest, but can also exhibit great environmental sensitivity. A variety of factors, including Australia's legal obligations under the Madrid Protocol, public expectations, certain research opportunities and ethical considerations, demand a very high standard of environmental protection. A survey outside the Davis Station limits in the Vestfold Hills, East Antarctica, identified 66 sites at which past human activities had left long term impacts on the physical environment. Nearly half of all observed impacts were the result of geoscientific research that had left old pit and trench sites, vehicular tracks, partly excavated palaeontological material, rock sampling and drilling sites, localised slope instability caused by disturbance, and discarded equipment and markers. Comparisons between rehabilitated sites and others where little, if any, rehabilitation appears to have been attempted suggest natural processes alone are generally insufficient to heal the damage, but that effective rehabilitation is often possible if undertaken immediately after the initial disturbance. 相似文献
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Duanne A. White Ole Bennike Simon L. Harley Kevin Kiernan Bernd Wagner 《Quaternary Research》2009,72(1):80-90
The presence of glacial sediments across the Rauer Group indicates that the East Antarctic ice sheet formerly covered the entire archipelago and has since retreated at least 15 km from its maximum extent. The degree of weathering of these glacial sediments suggests that ice retreat from this maximum position occurred sometime during the latter half of the last glacial cycle. Following this phase of retreat, the ice sheet margin has not expanded more than ∼ 1 km seaward of its present position. This pattern of ice sheet change matches that recorded in Vestfold Hills, providing further evidence that the diminutive Marine Isotope Stage 2 ice sheet advance in the nearby Larsemann Hills may have been influenced by local factors rather than a regional ice-sheet response to climate and sea-level change. 相似文献
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Daniel L. Codiga Heather E. Stoffel Christopher F. Deacutis Susan Kiernan Candace A. Oviatt 《Estuaries and Coasts》2009,32(4):621-641
Low dissolved oxygen events were characterized in Narragansett Bay (NB), a moderate-size (370 km2) temperate estuary with a complex passage/embayment geometry, using time series from 2001 to 2006 at nine fixed-site monitoring
stations. Metrics for event intensity and severity were the event-mean deficit relative to a threshold (mg O2 l−1) and the deficit-duration (mg O2 l−1 day; product of deficit and duration [day]). Hypoxia (threshold 2.9 mg O2 l−1) typically occurred intermittently from late June through August at most stations, as multiple (two to five per season) events
each 2 to 7 days long with deficit-duration 2 to 5 mg O2 l−1 day. Conditions were more severe to the north and west, a pattern attributed to a north–south nutrient/productivity gradient
and east–west structure of residual circulation. Spatial patterns for suboxic and severely hypoxic events (thresholds 4.8
and 1.4 mg O2 l−1) were similar. The view that different processes govern event variability in different regions, each influenced by local
hydrodynamics, is supported by both weak spatial synchronicity (quantified using overlap of event times at different sites)
and multiple linear regressions of biological and physical parameters against event severity. Interannual changes were prominent
and season-cumulative hypoxia severity correlated with June-mean river runoff and June-mean stratification. Benthic ecological
implications for areas experiencing events include: NB hypoxia classifies as periodic/episodic on a near-annual basis; highest
direct mortality risk is to sensitive and moderately sensitive sessile species in the northern West Passage and western Greenwich
Bay, with some risk to Upper Bay; direct risk to mobile species may be ameliorated by weak spatial synchronicity; and indirect
impacts, including reduced growth rates and shifts in predator–prey balances, are very likely throughout the sampled area
due to observed suboxic and hypoxic conditions. 相似文献
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D. Ward-Thompson P. A. R. Ade H. Araujo I. Coulson J. Cox G. R. Davis Rh. Evans M. J. Griffin W. K. Gear P. Hargrave P. Hargreaves D. Hayton B. J. Kiernan S. J. Leeks P. Mauskopf D. Naylor N. Potter S. A. Rinehart R. Sudiwala C. R. Tucker R. J. Walker S. L. Watkin 《Monthly notices of the Royal Astronomical Society》2005,364(3):843-848
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Kevin Kiernan 《The Australian geographer》1990,21(2):113-125
The Mt Anne massif is characterised by spectacular erosional landforms of glacial origin. Evidence of at least two separate Pleistocene glaciations is preserved in valleys that extend east and south of the massif, and also on nearby Schnells Ridge. There is evidence of a much older glaciation beneath the western slopes of the Mt Anne massif. Dense vegetation in the eastern valleys has inhibited mapping of the Quaternary geology there. These glaciations have influenced postglacial evolution of the landscape, including the advent of prominent karst features and Holocene landslip activity. 相似文献
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Moraines on Schnells Ridge, southwest Tasmania, have been dated using in situ 10Be. An age of 19,400 ± 600 yr is indicated for the well-preserved innermost moraine from consistent measurements on four large quartzite boulders. This corresponds closely with exposure ages reported by T.T. Barrows et al. (2002, Quaternary Science Reviews 21, 159–173) for Last Glacial Maximum glacial features farther north in Tasmania and southeast Australia. In contrast, ages between 39,000 and 141,000 yr were obtained from a series of boulders on a more extensive outer moraine, indicating that this has had a more complex history. 相似文献