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991.
对黄土高原定边、西峰、渭南三个剖面中古土壤层S1的定向连续古地磁样品作了详细的岩石磁学和古地磁学研究,均未发现Blake极性事件.在对其成因进行了分析研究后,提出如下看法:(1)六盘山以东黄土高原北部边缘的风成沉积可能存在局部的不连续性,因而没有记录Blake极性事件;(2)黄土沉积物的主要载磁矿物力磁铁矿,次生磁性矿物对剩磁的贡献可能大于原生磁铁矿,故在六盘山以东黄土高原北部边缘没有发现Blake极性事件;(3)六盘山以东黄土高原中部和南部地区,强烈的成土作用掩盖了持续时间较短的Blake极性事件;(4)六盘山以西的黄土高原具高速稳定沉积的特点,且成土作用弱,可记录Blake极性事件. 相似文献
992.
陈中强 《沉积与特提斯地质》1995,15(3):34-39
本文根据华南层序地层学分析,着重研究了晚二叠世的淹没事件。研究表明,晚二叠世海平面变化曲线不同于C.A.Ross和J.R.Ross(1987)的海平面变化曲线。根据华南地区和世界其它地区的古生物分析和层序地层分析,晚二叠世海平面变化结论如下:(1)二叠纪末期,全球发生海泛淹没事件,海平面急剧上升,而不是下降,(2)晚二叠世晚期的海进开始于吴家坪末期,至长兴期末期(二叠纪末期)达到高峰时期。 相似文献
993.
994.
南通地震台数字水准仪观测效果的分析 总被引:1,自引:0,他引:1
陆盛泉 《地震地磁观测与研究》2009,30(6):65-70
从南通地震台短水准背景出发,介绍了DiNi12数字水准仪代替原有光学水准仪在南通地震台应用的效果,论述了数字水准仪在台站形变观测中发挥的作用及注意事项。文章结合实例对数字水准仪与Ni002A仪器观测的资料进行了对比分析,验证了数字水准仪的优点和实用价值。 相似文献
995.
吉林南部的通化、柳河和白山地区的太古宙表壳岩系和TTG杂岩中,广泛存在钾化、钾长石脉、钾长石石英脉和钾质伟晶岩脉,显示在地质历史时期中该区曾经发生过广泛的钾事件。经野外地质调查、显微镜观察以及电子探针、X射线衍射及稳定同位素综合分析,确定出:①不同产状的钾长石的主要氧化物含量稳定;②从变黑云钾长花岗岩、黑云长英片麻岩到花岗伟晶岩脉,钾长石三斜度和有序度略显增高,但变化幅度较小;③不同产状钾长石的δ18O值较集中,变化于(4.90~8.49)×10-3。认为,该区的钾长石是来自于同一个岩浆源的物质在同一岩浆作用过程中不同阶段、不同就位方式的产物。 相似文献
996.
据赤道经向风剖面及热带西太平洋岛屿站测风资料来诊断厄尔尼诺(ElNino)事件,试图从观测事实方面来跟踪与预测ElNino的发生。分析结果得出:气候监测公报中850hPa风指数对监测、诊断已发生的ElNino事件较好,但不能用来预测ElNino事件的发生,而热带西太平洋岛屿站月平均纬向风对ElNino事件的发生有一定的指示意义。从越赤道气流的演变特征进一步证明,ElNino事件对应于弱季风,而拉尼娜(LaNina)事件对应于强季风。 相似文献
997.
Palaeoclimatic cycles, global environmental changes and new glacial periods induced by the impact of extraterrestrial bodies 总被引:1,自引:1,他引:0
In terms of Earth-Sun geometry, the Milankovitch theory has successfully explained most of the cyclic palaeoclimatic variations
during the history of the Earth, especially in the Quaternary. In this paper, the authors suggest that the impact of extraterrestrial
bodies on the Earth may be another mechanism to cause palaeoclimatic cycles, global environmental changes and new glacial
periods. Based on geological and geochemical records in the boundary layers produced by six huge Cenozoic bolide-impact events
(65, 34, 15, 2.4, 1.1, 0.73 Ma B.P.), including those at 34, 15, 1.1 and 0.73 Ma B. P. which are represented by four famous
tektite-strewn fields, the process and mechanics of palaeoclimatic cycles and global environmental catastrophes induced by
extraterrestrial impact are discussed in detail. Impact-generated dust, soot and aerosol floating in the stratosphere could
result in short-term (<1 year), rapid drop in temperature immediately after impact. Through self-regulation of the Earth’s
climate system, the temperature at the surface slowly went up within 100a and maintained stable for a long time at 250K. If
there were no other factors leading to the break-down of the newly-established equilibrium, a new glacial pound would be initiated.
Estimating from the thickness of δ13C and δ18O anomalies in sediments across the impact boundary layer and deposition rate, the duration of two stages of the palaeoclimate
cycle in the form of cold weather—greenhouse effect—normal weather was 104 – 105a, respectively. The conclusion deduced from the above model is supported by palaeotemperature change recorded by oxygen isotope
in sediments across the impact boundary layer.
The study was granted by the Scientific and Technological Bureau of Resources and Environment, Chinese Academy of Sciences
(KZ952-J1-031) and the National Natural Science Foundation of China. 相似文献
998.
The impact of El Niño on the precipitation in China for different seasons are investigated diagnostically. It is found that El Niño can influence the precipitation in China significantly during its mature phase. In the Northern winter, spring and autumn, the positive precipitation anomalies are found in the southern part of China during the El Niño mature phase. In the Northern summer, the patterns of the precipitation anomalies in the El Niño mature phase are different from those in the other seasons. The negative precipitation anomalies appear in both southern and northern parts of China, while in between around the lower reaches of the Yangtze River and the Huaihe River valleys the precipitation anomalies tend to be positive. In the Northern winter, spring and autumn, the physical process by which El Niño affects the precipitation in the southern part of China can be explained by the features of the circulation anomalies over East Asia during the El Niño mature phase (Zhang et al., 1996). The appearance of an anticyclonic anomaly to the north of the maritime continent in the lower troposphere during the El Niño mature phase intensifies the subtropical high in the western Pacific and makes it shift westward. The associated southwesterly flow is responsible for the positive precipitation anomalies in the southern part of China. In the Northern summer, the intensified western Pacific subtropical high covers the southeastern periphery of China so that the precipitation there becomes less. In addition, the weakening of the Indian monsoon provides less moisture inflow to the northern part of China. 相似文献
999.
Wang Huijun 《大气科学进展》1999,16(3):361-366
Studies have revealed that predictability of the atmospheric general circulation is generally high in the tropics throughout the year and that there is some predictability in the Northern extra-tropical winter at-mospheric circulation through some patterns of tele connection. Predictability of the general circulation at the polar regions has still remained as a ‘cold’ topic and little has been known about this question. Based on a preliminary study on the predictability by using the Institute of Atmospheric Physics (IAP) general circulation model, it is found that the SST-related predictability of the Southern winter lower atmospheric circulation in Antarctica is reasonably high and that there is some predictability in the 500 hPa and 200 hPa geopotential height fields over Europe and the Okhotsk Sea region during the Northern winter. It is sug-gested that more researches on this issue based on data analysis and model simulations are needed to obtain better understanding. 相似文献
1000.
西太平洋暖池次表层海温一场与ENSO关系的CGCM模拟结果 总被引:19,自引:4,他引:15
全球大气与热带太平洋相耦合的数值模式(CGCM) 很好地模拟了ENSO ( 厄尔尼诺和拉尼娜) 型海表水温(SST) 异常, 进一步分析多年的模式积分结果, 清楚地表明赤道中东太平洋SST 异常与西太平洋暖池次表层( 深100 ~200 m) 的海温异常有密切的关系。在El Nino 事件发生之前的半年到一年左右, 西太平洋暖池次表层海温有明显正异常,并向东传播; 而在La Nina 发生之前的半年到一年左右, 暖池次表层海温有明显负异常, 并向东传播。因此, 西太平洋暖池次表层海温异常及其东传对El Nino (La Nina) 的发生有极重要作用。 相似文献