桂林浅水相区D/C界线层的PAC旋回及地层对比意义     

沈健伟 《沉积与特提斯地质》1994,(4)

桂林地区晚泥盆世法门期末，海平面变化表现出高频率的特点，由此产生了５级旋回──ＰＡＣ（ｐｕｎｃｔｕａｔｅｄａｇｇｒａｄａｔｉｏｎａｌｃｙｃｌｅｓ）。ＰＡＣ是一种地层的幕式堆积方式，表现为间断加积的特点。本文讨论了桂林Ｄ／Ｃ界线层的ＰＡＣ，并认为ＰＡＣ中向上变浅之后出现的暴露面加上代表海水陡然加深的的页岩是短距离内不同相地层对比的极好标志，文中以额头村剖面新发现的可形刺：Ｐｓｅｕｄｏｐｏｌｙｇｎａｔｈｕｓｄｅｎｔｉｌｉｎｅａｔｕｓ和Ｐｓｅｕｄｏｐｏｌｙｇｎａｔｈｕｓｃｏｎｔｒａｖｅｒｓｕｓ作为参照物，对额头村剖面和南边村剖面的ＰＡＣ进行对比，从而提高浅水相Ｄ／Ｃ界线的精度。  相似文献   

松辽盆地白垩纪古气候特征及其变化机制   总被引：5，自引：0，他引：5  

张立平  王东坡 《沉积与特提斯地质》1994,(1)

本文综合研究了松辽盆地白垩纪古气候的沉积记录、孢份古植物群记录及碳、氧同位素地球化学特征，得出了松辽盆地白垩纪古气候的演变规律。并认为碳族国与古气候旋回有密切的对应关系，大气中ＣＯ＿２含量的变化是古气候变化的根本原因。每一温暖时期的开始都与大气中ＣＯ＿２含量的增加有关，随着固碳作用的增强，温室效应削弱。碳旋回是古气候变化的重要机制。  相似文献   

Correlation of the major late Jurassic —early Tertiary low- and highstand cycles of south-west Egypt and north-west Sudan     

Peter Wycisk 《International Journal of Earth Sciences》1994,83(4):759-772

The mainly continental deposits of northwest Sudan and south-west Egypt have been correlated with coeval shallow marine and marine deposits in northern Egypt along a north-south running cross-section, based on surface and subsurface data. The palaeodepth curve of northern Egypt illustrates the gradual seal-level rise, reaching its maximum during the Late Cretaceous with conspicuous advances during the Aptian and late Cenomanian. A general highstand is also recorded during the Campanian-Maastrichtian in north-west Sudan. A detailed facies correlation is given for the Aptian and late Cenomanian highstand in western Egypt. The correlation of the Cenomanian Bahariya and Maghrabi formations displays short-term relative sealevel fluctuations. The interpretation illustrates the extensiveness of related erosional processes in the hinterland, partly intensified by temporarily uplift of the Uweinat-Aswan High in the south. Regional uplift and constant erosion took place in south-west Egypt during Coniacian and Santonian times. The regional stratigraphic gaps and uncertain interpretation of the Bahariya Uplift are induced by the influence of the Trans-African Lineament, especially during the Late Cretaceous. Low-stand fluvial sheet sandstones characterized by non-cyclic sequence development and high facies stability occur, especially in the Neocomian and early Turonian. During the Barremian and Albian, fluvial architecture changes to more cyclic fluvial sequences and increasing soil formation, due to increasing subsidence, more humid climatic conditions and the generally rising sea level, culminating in the extensive shallow marine Abu Ballas and Maghrabi formations.  相似文献   

ANALYSIS OF SURFACE AIR TEMPERATURE RECORDED IN LAHORE AND MIANWALI OVER THE PAST THREE DECADES          下载免费PDF全文

Mian M. Munir  K. Hussain  M. S. Zafar 《Acta Meteorologica Sinica》1995,9(1):123-128

Surface air temperatures recorded over the past three decades at the weather stations located in Lahore (anindustrialized and densely populated city) and Mianwali (a small and sparsely populated city) were analyzed in order tostudy their climatic trend.Lahore,where meteorological data are recorded at two weather stations (city station and air-port station) indicates a cooling trend,of about 0.5℃ per record period of 1953—1992,for the airport station (31°31′N,74°24′E) and a slight warming trend,of about 0.2℃,for the city station (31°33′N,74°20′E) for the record period of 1950—1992.The Mianwali weather station (32°33′N,71°31′E) also shows a slight cooling trend,of about 0.4℃ per recordperiod of 1959—1992.The climatic variability at these stations was studied by computing seasonal and annual tempera-ture anomalies.The results are explained in terms of the local environmental conditions.  相似文献   

中国龙卷风的若干特征   总被引：32，自引：3，他引：32  

魏文秀  赵亚民 《气象》1995,21(5):36-40

应用数理统计方法和通过对观测资料的分析，研究了龙卷风的气候特征；根据近年天气资料，研究了龙卷风发生的天气系统，层结特征，风场和母体云团的特征。  相似文献   

CLIMATIC CHARACTERISTICS OF EARTH-ATMOSPHERE OUTGOING LONGWAVE RADIATION OVER CHINA^*          下载免费PDF全文

Weng Duming 《Acta Meteorologica Sinica》1995,9(2):228-236

ERBE and ISCCP data are used to investigate the cloud forcing and latitude and atmospheric temperature effects on outgoing longwave radiation(OLR) in the earth-atmosphere system,and the similarity of OLR field to 500 hPa and surface effective radiation fields.Also,discussion is taken up of the OLR distribution on a nationwide basis,indicating that the winter(summer) OLR pattern is roughly a zonal type(asymmetrical saddle) with the annual pattern analogous to the January one.In the end the yearly OLR variation features are addressed on a regional basis.  相似文献   

广西防城港市旅游气候资源评价及其利用     

许文龙  郭亮  李赛声  黄滢 《热带地理》2007,27(5):420-423

气候资源是旅游业开发中十分重要的资源之一,通过分析防城港市旅游资源和气候资源,并对其优势和人体舒适度进行了综合评价,指出防城港市具有旅游资源丰富、地理气候特征显著、适宜旅游时间长等优势;同时从舒适度分析得出,本市秋冬季节温暖舒适,是避冬的好地方,夏季高温时间少,是避暑的圣地。据此提出充分利用本地的旅游气候资源,打造本市旅游精品,开发以秋冬季为主的度假游,充分利用沿海的天然浴场,创建十万大山国家森林公园生态环保天然疗养院,做强做大防城港市旅游产业。  相似文献   

High-resolution climate variability of southwest China during 57-70 ka reflected in a stalagmite δ18O record from Xinya Cave   总被引：1，自引：0，他引：1  

Li TingYong  Yuan DaoXian  Li HongChun  Yang Yan  Wang JianLi  Wang XinYa  Li JunYun  Qin JiaMing  Zhang MeiLiang  Lin YuShi 《中国科学D辑(英文版)》2007,50(8):1202-1208

A 26-cm-long stalagmite (XY2) from Xinya Cave in northeastern Chongqing of China has been ICP-MS ²³⁰Th/U dated, showing a depositional hiatus at 2.3 cm depth from the top. The growth of the 2.3–26 cm interval determined by four dates was between 57 ka and 70 ka, with a linear growth rate of 0.023 mm/a. We have analyzed 190 samples for δ ¹⁸O and δ ¹³C, mostly in the 2.3–26 cm part. The δ ¹⁸O and δ ¹³C values between 57 ka and 70 ka reveal decadal-to-centennial climatic variability during the glacial interval of Marine Isotope Stage 4 (MIS4), exhibiting much higher resolution than that of the published Hulu and Dongge records during this interval. Speleothem δ ¹⁸O in eastern China, including our study area can be used as a proxy of summer monsoon strength, with lighter values pointing to stronger summer monsoon and higher precipitation, and vice versa. Two decreases in the δ ¹⁸O signature of XY2 record around 59.5 and 64.5 Ka are argued to correspond to the Dansgaard-Oeschger (D-O) events 17 and 18 respectively. The Heinrich event 6 (H6) can be identified in the record as a heavy δ ¹⁸O peak around 60 ka, indicating significant weakening of the monsoon in Chongqing during the cold period. The XY2 δ ¹⁸O record shows very rapid change toward to the interstadial condition of the D-O event, but more gradual change toward to the cold stadial condition. This phenomenon found in the Greenland ice core records is rarely observed so clearly in previously published speleothem records. According to SPECMAP δ ¹⁸O record, the glacial maximum of MIS 4 was around 64.5 ka with the boundary of MIS 3/4 around 60 ka. Unlike the marine record, the speleothem record of XY2, China, exhibits much high frequency variations without an apparent glacial maximum during MIS 4. However, the timing of MIS 3/4 boundary seems to be around 60 ka when the H6 terminated, in agreement with the marine chronology. The growth period of sample XY2 during glacial times probably reflects a local karstic routing of water, rather than having climatic significance. Supported by the National Natural Science Foundation of China (Grant Nos. 40672165, 90511004, 40672202) and the Academician Special Project of Chongqing Science Committee (Grant No. 2003-7835)  相似文献   

广东沿海强东北季风的气候统计特征   总被引：1，自引：0，他引：1  

梁健  李晓娟  毛绍荣  林镇国 《气象》2002,28(8):44-47

通过对1988－1997年冷空气造成的广东沿海强东北季风过程的气候统计分析，发现广东的强东北季风有明显的月分布规律，而年际变化有逐渐减少的趋势；强东北季风与地面因子相关程度较高，而与850hPa要素相关性较低；同时发现地面冷高压中心位置聚合度较高，但不同月份、不同时次，其中心位置有明显差异。  相似文献   

内蒙古地区2001年夏季气候特征及前兆信号分析     

马清霞 《气象》2002,28(12):11-14

2001年夏季，内蒙古地区发生了继1999、2000年连续两年的干旱之后的较为严重的全区性干旱。通过分析2001年内蒙古地区夏季气候特征及预测信息，研究内蒙古夏季（1739－2000年中西部地区、1774－2000年东部地区）旱涝气候变化规律，探讨影响内蒙古地区夏季干旱前期信息的变化特征。结果表明，严重干旱年多发生在La Nina事件峰值年次次，环流特征为北半球极涡强度前冬弱后冬强，自上年5月至当年4月呈现出鄂霍次克海高压偏强副高偏弱，并持续3－7个月，继而转成鄂霍次克海高压偏弱副高偏强，并持续2－6个月，可将这些特征作为内蒙古地区夏季严重干旱的前兆信号。  相似文献