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171.
通过对水西沟群(J1-2sh)古植物、古孢粉化石组合特征等系统的研究,对八道湾组(J1b)、三工河组(J1s)、西山窑组(J1x)古气候类型进行了区分;并据此认为西山窑组(J1x)为一套气候地层层序,相应划分为四个体系域:即低水位、湖泊扩张,高水位及湖泊收缩体系域。再结合一些岩性岩相等特殊标志,对十红滩东部外围地层层序进行了划分,结果与十红滩矿区地层层序本质是一致的。 相似文献
172.
开滦矿区煤系地层上覆由于防水煤柱留设过大,造成了大量的煤炭储量呆滞。为了提高煤炭资源回收率,确保安全生产,开滦林南仓矿在西二采区进行了工作面采后的导高观测试验研究,测量导水裂隙带岩层的漏失情况,为提高开采上限提供了地质依据,防水煤柱由原来的65m缩小到53m,成功地在1221上工作面进行了试验开采。 相似文献
173.
根 据 某露 天 煤 矿 非工 作 帮 移 动监 测 的 多 年资 料 ,总 结 出 露 天矿 非 工 作 帮的 监 测 方 法,并 初 步探 讨 了 露 天 矿非 工作 帮 移动 滑坡 的 规律 性。 相似文献
174.
On the basis of different sets of aerial photos the dynamics of the reed bed areas of Lake Constance were investigated in relation to the dynamics of the water levels. The objectives of the study were to quantify the changes of reed areas due to different flood events in the last decades and their recovery in the time periods between these events. The results should given information of the relevance of water level variations on reed bed dynamics and the regeneration times of reed beds after extreme disturbance events.Following the extreme flood at Lake Constance in 1999 the reed belts of Lake Constance lost approximately 30 ha (24%) of the lakeside reed beds. The loss is comparable to the situation in the late 1960s, when approximately 40 ha died back due to the extreme flood in 1965 and the high spring water levels in the subsequent years. In the time period between the extreme floods of 1965 and 1999, the reed areas expanded to nearly 85% of the area before 1965. The expansion rates increased with increasing distance to the flood event of 1965. Especially in periods with series of years of low spring water level the expansion rates were high.The damage degrees of the reed areas in the years 2000 and 2002 showed a clear relation to the elevation (i.e. average water level) of the stands. The damage degree increased with decreasing elevation. Furthermore the regeneration process of severely damaged stands was related to the elevation level of the stands. Whereas stands at high elevation regenerate fast, those at low elevation died off completely in the years after the extreme flood. This supports the hypothesis that the water level flutuations play a major role in the reed dynamics of Lake Constance.As a consequence of the climate change an increase in the frequency of high spring water levels is expected. Thus, it seems unlikely that reed stands will ever expand again to the same area as before 1965. 相似文献
175.
Michael J. Simms 《地球表面变化过程与地形》2004,29(4):477-494
Denudation mechanisms differ fundamentally between limestone and silicate rock types, which are subject to very different rate thresholds and enhancers/inhibitors. Silicates are removed largely by erosion, the mechanical entrainment and transport of particles. This is a relatively high energy, and highly episodic, process which occurs only when a minimum threshold ?ow velocity is exceeded; it is inhibited by vegetation cover and favoured by strongly seasonal runoff. Limestone is removed largely by chemical dissolution at a rate directly proportional to runoff. Dissolution is a relatively low energy process that can occur at any ?ow velocity or in static water; in general it is enhanced by vegetation cover and non‐seasonality of runoff. These contrasting factors in the denudation of silicates versus limestone can produce strikingly uneven rates of surface lowering across a landscape, sometimes akin to the well known ‘tortoise and hare race’, where the slow and steady denudation of limestones may in the long term exceed the sometimes rapid, but often localized and episodic, erosion of silicates. Prolonged exposure of limestone to a humid temperate climate in a tectonically stable environment produces low‐relief corrosion plains in which limestone uplands are anomalous and, in most instances, due to recent unroo?ng from beneath a siliciclastic cover. In a highly seasonal or semi‐arid climate almost the exact inverse may develop, with ‘?ashy’ runoff and sparse vegetation favouring erosion rather than dissolution. Even under a constant humid climate progressive unroo?ng of a thick limestone unit within folded siliciclastics may lead to a topographic inversion over time, with the limestone outcrop always forming a topographic low ?anked by siliciclastic uplands. Valleys will be initiated on anticlinal crests, where the limestone is ?rst unroofed, but progressive lowering of the limestone causes these valleys to migrate to their ?nal position in the synclinal troughs. In humid climates isostatic compensation in response to slow, but continuous, denudation of extensive limestone outcrops may be a signi?cant factor in the development of relief on adjacent, more slowly eroding, silicate outcrops. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
176.
177.
山东省气候变化及其对冬小麦生产潜力的影响 总被引:11,自引:0,他引:11
利用全省 2 7个台站 1 96 1~ 1 998年的温度、降水、日照等基本气象要素资料 ,对山东省气候变化特点进行了分析 ,并对冬小麦生产潜力进行了计算、分析。结果表明 ,山东省年、季平均气温呈波动性增暖趋势 ,降水量呈减少趋势。气候变暖有利于生产潜力的提高 ,冬小麦气候生产潜力总的变化趋势是波动性的上升 ,但较光温生产潜力倾向率小 ,反映了小麦生育期内光、温、水的综合影响。 相似文献
178.
179.
180.
柴达木盆地近40a气候变化及其对农业影响的研究 总被引:7,自引:2,他引:7
利用柴达木盆地6个代表站逐日平均气温、逐月降水资料以及逐日最低气温资料。对盆地40a来的气候变化特征进行分析。同时分析了气候变化对农业生产的影响。为充分利用变化了的农业气候资源。减少不利因素带来的影响提出了对策和建议。 相似文献