STUDY ON THE BASIC IGNEOUS EVENT IN CENTRAL QIANGTANG, TIBET     

Li Cai  Yang Deming  Wang Tianwu  Yang Rihong  Liu ShenWT  ”BX 《地学前缘》2000,(Z1)

STUDY ON THE BASIC IGNEOUS EVENT IN CENTRAL QIANGTANG, TIBET  相似文献   

郯庐断裂带的脉动式伸展活动   总被引：22，自引：0，他引：22  

朱光  刘国生  宋传中  王道轩 《高校地质学报》2000,6(3):396-404

郯庐断裂带于晚白垩世至早第三纪经历了强烈的伸 展活动,普遍控制发育了断陷盆 地。断裂带中、南段的伸展活动起始于晚白垩世早期,而北段起始于早第三纪早期,具有明 显向北迁移的规律。断裂带的伸展活动呈脉动式渐进发展。现已发现在晚白垩 世至早第三纪该断裂带发生了6次伸展事件,在所控制的盆地内相应有明显的沉积响应。断 裂带伸展活动的影响和规模由早至晚逐渐扩大。这些伸展活动的迁移现象和脉动式发展与同 期的太平洋板块活动有关。  相似文献   

Reconstruction of palaeoceanographic conditions in the South Atlantic Ocean at the last two Terminations based on calcareous dinoflagellate cysts     

O. Esper  K. A. F. Zonneveld  C. Höll  B. Karwath  H. Kuhlmann  R. R. Schneider  A. Vink  I. Weise-Ihlo  H. Willems 《International Journal of Earth Sciences》2000,88(4):680-693

 Despite the increasing interest in the South Atlantic Ocean as a key area of the heat exchange between the southern and the northern hemisphere, information about its palaeoceanographic conditions during transitions from glacial to interglacial stages, the so-called Terminations, are not well understood. Herein we attempt to increase this information by studying the calcareous dinoflagellate cysts and the shells of Thoracosphaera heimii (calcareous cysts) of five Late Quaternary South Atlantic Ocean cores. Extremely high accumulation rates of calcareous cysts at the Terminations might be due to a combined effect of increased cyst production and better preservation as result of calm, oligotrophic conditions in the upper water layers. Low relative abundance of Sphaerodinella albatrosiana compared with Sphaerodinella tuberosa in the Cape Basin may be the result of the relatively colder environmental conditions in this region compared with the equatorial Atlantic Ocean with high relative abundance of S. albatrosiana. Furthermore, the predominance of S. tuberosa during glacials and interglacials at the observed site of the western Atlantic Ocean reflects decreased salinity in the upper water layer. Received: 9 November 1998 / Accepted: 26 October 1999  相似文献   

Sequence and isotope stratigraphy of Late Triassic distal periplatform limestones from the Northern Calcareous Alps (Kälberstein Quarry, Berchtesgaden Hallstatt Zone)     

H.-J. Gawlick  F. Böhm 《International Journal of Earth Sciences》2000,89(1):108-129

Received: 24 September 1998 / Accepted: 14 November 1999  相似文献   

旋回频率曲线在幕式聚煤作用研究中的应用-以西南地区上二叠统为例   总被引：4，自引：1，他引：3       下载免费PDF全文

郝黎明  邵龙义  时宗波  张鹏飞 《古地理学报》2000,2(4):12-19

海平面的变化是旋回性沉积作用的重要控制因素。在克拉通盆地滨海平原沉积背景中,海岸线附近的沉积环境受海平面变化影响最为明显,旋回性沉积作用易留下证据。而在远离海岸线的内陆或滨外较深水地区,海平面变化一般难以引起沉积环境的明显变化,因而其旋回性的沉积作用不甚明显。反映在旋回的数量上,海岸线附近的旋回数目比远离海岸线地区的旋回数目要多得多。海岸线附近一般是最有利的聚煤场所,所以某一时期的旋回频率曲线中的峰值所在地区即是该时期聚煤中心所在位置。在三级海平面变化范围内,从低位、海侵到高位层序组,旋回峰值区会随着海平面的变化而变化,据此我们可以识别聚煤中心的迁移规律。依据高分辨率层序地层学原理,本文将贵州西部晚二叠世含煤岩系划分为3个三级复合层序及15个四级层序,每个三级复合层序中又分为低位、海侵和高位层序组,在此基础上,进一步建立了不同层序组及不同复合层序的旋回频率曲线,并根据其峰值的位置分析了相应聚煤中心的变化。  相似文献   

渤海西北岸曹妃甸地区晚更新世末期以来古环境恢复     

王艳 《海洋科学进展》2000,18(3):47-53

通过孢粉和硅藻分析并结合沉积学以及14C测年等资料,重建了渤海湾西北岸曹妃甸地区晚更新世末期以来的古植被、古气候以及古地理等演变过程,细致刻划了渤海湾西北岸海平面变化和海陆变迁史.曹妃甸地区自晚更新世末期以来的古沉积环境经历了冲积平原或滨海平原、河口或近海湖沼环境、三角洲与砂坝-泻湖沉积环境、废弃三角洲与砂坝-泻湖沉积环境等4个阶段.气候和植被在不同阶段也发生了相应的变化.  相似文献   

四川省剑门关一带晚侏罗世沉积体系与古环境演化   总被引：2，自引：0，他引：2  

徐世球  佘继完 《地球科学》2001,26(3):235-240

晚侏罗世是龙门山前陆盆地演化的关键时期, 因而沉积体系与古环境演化研究具有重要意义.运用比较沉积学的方法, 通过对沉积序列与旋回的详细研究, 将研究区晚侏罗世沉积体系分为湖泊沉积体系、三角洲沉积体系、冲积扇沉积体系以及河流沉积体系; 基于沉积背景和演化的分析, 确定龙门山推覆构造带是研究区晚侏罗世古环境演化和沉积体系空间配置的控制因素; 依据古流和物源分析, 确定西北部的龙门山是本区主要物源区   相似文献   

晚上新世以来南海北部深部水团演化     

黄宝琦  翦知湣  赵泉鸿  汪品先 《地球科学》2005,30(5):529-533

对南海北部大洋钻探184航次1146站晚上新世以来底栖有孔虫属种组合的Q型因子分析, 发现底栖有孔虫组合以2.1Ma, 1.5Ma和0.7Ma为界, 分为Stilostomella-Globocassidulina subglobosa-Nodogenerina, Bulimina alazanensis, Uvigerina perigrina和Melonis barleeanus-Globobulimina affinis-Bulimina aculeata4个组合.结合底层水溶解氧含量和浮游、底栖有孔虫碳同位素分析, 认为底栖有孔虫组合的变化是南海底层水影响所致, 以及南海北部表层和底层海水营养盐含量变化的共同结果.   相似文献   

西昆仑阿卡阿孜山杂岩体的特征和成因   总被引：7，自引：2，他引：5  

谌宏伟  罗照华  莫宣学  詹华明 《现代地质》2005,19(2):189-197

阿卡阿孜山杂岩体位于西昆仑昆南地体南侧,被新藏公路横切出一条南北长约2 km的剖面。在剖面范围内可见二长闪长岩、石英二长闪长岩、花岗闪长岩、二长花岗岩、正长花岗岩和碱长花岗岩等多种岩石类型出露。通过详细研究岩体的野外地质特征、地球化学和同位素地球化学特征发现：岩体中出现不平衡矿物组合;镁铁质微粒包体中可见石英和长石捕虏晶;各岩石样品的痕量元素配分型式呈现相似性;岩体的Sr、Nd、Pb同位素体系同时具有地幔和下地壳的贡献等,认为岩体形成于壳幔岩浆混合作用,幔源岩浆底侵作用可能是混合作用的直接原因。由此推测,幔源岩浆底侵作用是西昆仑地区印支晚期岩浆活动的重要诱发机制。  相似文献   

Macrofossil evidence of alder (Alnus sp.) in Britain early in the Late Glacial Interstadial: implications for the northern cryptic refugia debate     

D. S. Young  C. P. Green  C. R. Batchelor  P. Austin  S. A. Elias  J. Athersuch  P. Lincoln 《第四纪科学杂志》2021,36(1):40-55

Wood macrofossil remains of alder and willow/poplar have been recovered from a sediment sequence in the valley of the Turker Beck in the Vale of Mowbray, North Yorkshire. These remains have yielded radiocarbon dates early in the Devensian Late Glacial (14.7–14k cal a bp ), equivalent to the early part of the Greenland Interstadial (GI-1e) of the GRIP ice-core record. These are the earliest dates recorded for the presence of alder in the Late Glacial in the British Isles. Associated biological remains have provided a palaeoenvironmental record for this early part of the Greenland Interstadial, generally indicative of open environments dominated by herbaceous taxa on both the wetland and dryland surfaces. However, stands of alder, birch and willow woodland were also present, and indicate the possibility that such tree species survived in cryptic refugia in Britain as elsewhere in northern Europe during the Last Glacial Maximum. The absence of alder pollen at Turker Beck, in a sequence in which its macrofossil remains are relatively abundant, lends support to the view that pollen can be a poor indicator of the presence of tree species in Late Glacial sequences in northern and western Europe.  相似文献