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This paper presents a critical review of previous lichenometric and lichen growth studies in southern parts of West and East Greenland. These studies include classic work from around Søndre Strømfjord, Sukkertoppen, Sermilik and Angmagssalik. Particular emphasis is placed on those studies examining the role played by climatic continentality on the growth rate of crustose lichens in Greenland. The latter part of the paper presents new data on lichen growth rates from Sermilik, between 2001 and 2006, in 22 different lichen species. Measurements show that different species grow at different rates and growth rates vary from site to site. In this study Rhizocarpon geographicum generally grows slowly (<0.2 mm a−1 ) while other species such as Pseudephebe minuscula grow more rapidly (1.0 mm a−1 ) in the same environment. Comparison with other studies shows that taxa-specific growth rates are slightly greater in West than in East Greenland – probably as a result of the slightly more favourable climate and higher precipitation levels. It is suggested that recent climate change, most marked in southern Greenland, will probably result in changed growth curves (over time) for species such as Rhizocarpon geographicum . However, only more precise growth curves and lichenometric dating curves can demonstrate such a phenomenon. 相似文献
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BY VIKRAM GUPTA RUCHIKA SHARMA MADHO PRASAD SAH 《Geografiska Annaler: Series A, Physical Geography》2009,91(3):179-188
Four rock types (quartz mica gneiss, schist, quartzite and calc-silicate) located in the Satluj and Alaknanda valleys were used to test whether a Schmidt hammer can be used to distinguish rock surfaces affected by various natural and man-induced processes like manual smoothing of rock surfaces by grindstone, surface weathering, deep weathering, fluvial polishing and blasting during road construction. Surfaces polished by fluvial process yielded the highest Schmidt hammer rebound (R-) values and the blast-affected surfaces yielded the lowest R-values for the same rock type. Variations in R-value also reflect the degree of weathering of the rock surfaces. It has been further observed that, for all the rock types, the strength of relationship between R-values for the treated surfaces (manual smoothing of rock surface by grindstone) and the unconfined compressive strength (UCS) is higher than for the fresh natural surfaces. 相似文献
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BY TIMOTHY F. JOHNSEN HELENA ALEXANDERSON DEREK FABEL STEWART P.H.T. FREEMAN 《Geografiska Annaler: Series A, Physical Geography》2009,91(2):113-120
The overall pattern of deglaciation of the southern part of the Scandinavian Ice Sheet has been considered established, although details of the chronology and ice sheet dynamics are less well known. Even less is known for the south Swedish Upland because the area was deglaciated mostly by stagnation. Within this area lies the conspicuous Vimmerby moraine, for which we have used the terrestrial cosmogenic nuclide (10 Be) exposure dating technique to derive the exposure age of six glacially transported boulders. The six 10 Be cosmogenic ages are internally consistent, ranging from 14.9 ± 1.5 to 12.4 ± 1.3 ka with a mean of 13.6 ±0.9 ka. Adjusting for the effects of surface erosion, snow burial and glacio-isostatic rebound causes the mean age to increase only by c. 6% to c. 14.4± 0.9 ka. The 10 Be derived age for the Vimmerby moraine is in agreement with previous estimates forthe timing of deglaciation based on radiocarbon dating and varve chronology. This result shows promise for further terrestrial cosmogenic nuclide exposure studies in southern Sweden. 相似文献
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本篇分为三节:第一节论研究(竹廷)蜗之方法及其各部分之名称;并猎取古生物学家迄今历史之结果而加以批评。第二节专述中国北部已发见之(竹廷)蜗。第三节讨论本篇所述各种(竹廷)蜗生存之时代及其棲息流徙之情形。 相似文献
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INTRODUCTION One of the major structural features in north China is the great fault system in central Shensi and Shansi known as the Weiho (渭河) Graben and Fenho (汾河) Craben respectively (Fig. 1). Dr. Bailey Willis seems to 相似文献
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The dust of Peking is well known to every traveller, but its composition, texture and origin are yet little known. An attempt is made here to throw some light on these questions. 相似文献
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本篇之结论有下列数要点.(一)德人佛莱士谓棲霞石灰岩属下石炭纪之说完至错误,其时代决非下石炭纪二)棲霞石灰岩在长江流域分布甚广,凡燧石石灰岩之底部无处无之,但自此南北行均渐归绝迹.(三)棲霞石灰岩代表-古太平洋区之海浸,故其生物化石海与南美洲者较相近而与我国北流及其他各处者反无关.(四)据腕足类化石之研究,棲霞石灰岩之时代应属上石炭纪,但为时在Schwagerina 期之前.(五)在长江流域,燧石石灰岩(即巫山石灰岩下部)代表-连续之沈积;底为珊瑚层(即棲霞石灰岩),属上石炭纪;中为各纺锤虫层,大致相当于Schwagerina期,属下二叠纪;上为Oldhamina及Lyttonia层,完圣与印度?领之上及中长身贝石灰岩相当,属中二叠纪。 相似文献
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本文先略述苏联与我国过去对大气环流的研究状况,及其重要性.过去研究环流偏差的问题,常以月平均高空图及地面图对准平均图的偏差状况来讨论,如苏联坡戈香(Х.П.Погосян)也是如此**.但月平均图对该月的详细环流演变过程不能表示出来.本文设计用一种环流综合图,以求表示长时期中(月或季)高空西风带内环流演变的具体情况.采用七种符号,来表示逐日各经线上环流系统的性质及气流的运动.并把西风带分为南北两部分来处理,北带从北纬50°到65°,南带从北纬35°到50°.这样在一个月内逐日西风带环流的演变,就可以在同一张图上表示出来. 相似文献