中国南海北部陆架区更新世晚期沉积物年代学及古环境研究 ——以DG钻孔为例     

张志亮  刘金瑞  张浩博  张中保  哈广浩  闵伟  聂军胜  任治坤 《地震地质》2021,43(6):1351-1367

大陆架作为海陆相互作用的关键地区,对于研究大陆的构造演化、海陆变迁、海平面升降以及气候变化具有重要意义.然而由于不同研究方法的局限性,目前对大陆架沉积物年代学及其蕴含地质信息的认识仍然不足.南海是西太平洋最大的边缘海,是全球海洋沉积作用最为活跃的地区之一,也是海陆相互作用最为典型的区域.作为东亚大陆物质的主要沉积区,南海已经受到了学术界越来越多的关注.然而,目前的研究工作主要集中于沉积连续、信号记录稳定但沉积速率较慢、总体分辨率较低的深海区沉积物.相对而言,沉积速率较快、分辨率较高的浅海大陆架沉积为高分辨率年代学和古环境的研究提供了重要的地质材料,但由于大陆架沉积环境动荡导致沉积信号记录不稳定甚至缺失.针对南海大陆架沉积,尤其是对钻孔沉积物高分辨率年代学研究仍相对较少,限制了对南海构造与气候演化过程的认识.为了更好地限定南海北部陆架区更新世晚期沉积物的年代,研究其中蕴含的古环境信息,探讨东亚地区气候变化的驱动机制问题,同时为南海海域活动构造研究提供年代学框架,文中以南海北部DG钻孔为研究对象,在微体古生物化石和碳同位素年龄(14C)数据的基础上,利用大陆架沉积物磁化率与深海氧同位素的对比对其沉积物年代学进行了系统研究.基于此,结合色度和孢粉结果,对其古气候意义进行了初步探讨.结果表明,该钻孔沉积物的磁化率可对应于深海氧同位素的阶段1—阶段9(MIS 1—MIS 9),底部年龄约为300ka,磁化率低值区间对应于冰期,高值区间对应于间冰期.这与该钻孔沉积物中的孢粉和色度所记录的古环境信息相吻合.冰期时气候较为寒冷,水体变浅,沉积物搬运距离相对增大,矿物以氧化作用为主,主要形成弱磁性的磁性矿物(如赤铁矿),导致磁化率较低;间冰期时,气候相对暖湿,水体变深,沉积物搬运距离相对缩短,矿物以还原作用为主,主要形成强磁性的磁性矿物(如磁铁矿等),导致沉积物的磁化率显著增强.因此,南海大陆架北部更新世晚期沉积物的磁化率变化可以反映东亚地区更新世晚期以来冰期—间冰期气候旋回.磁化率与深海氧同位素的对比作为一种晚第四纪松散沉积物的相对定年方法,在南海北部陆架区更新世晚期沉积物定年方面是适用且可靠的,可为海洋大陆架沉积物定年和对比研究提供新的参考.  相似文献   

Association between Tropical Convection and Boreal Wintertime Extratropical Circulation in 1982／83 and 1988／89     

Ja-Yeon MOON  Kyung-Ja HA 《大气科学进展》2003,20(4):593-603

Boreal wintertime extratropical circulation is studied in relation to the tropical convection during the 1982/83 El Nino and 1988/89 La Nina. The anomaly structure of 1982/83 and 1988/89 over the extratropics reveals remarkably different features as the longitudinal tropical forcing region changes. The Rossby wave source (Positive) shows the largest maximum over East Asia in both years due to the persistent heating from the western Pacific warm pool area. However, the sink term shows contrasting features over the subtropics and extratropics between the two years. In the El Nino year, enhanced tropical convection over the eastern Pacific produces the Rossby wave sink at 10?N and shifted eastward over the North Pacific, while in the La Nina year, the sink area is shifted westward over the North Pacific. The contrasting features between the two events in mean-eddy interaction appears especially over the downstream area of the East Asian Jet. The extension (retraction) of the meanflow eastward (westward) to  相似文献   

2002年3月21-22日影响韩国的沙尘天气分析   总被引：1，自引：0，他引：1  

金正润  牛生杰  河惠卿 《南京气象学院学报》2007,30(5):643-647

利用气象卫星、天气形势场和NCEP/NCAR再分析资料,分析了2002年3月21-22日影响韩国沙尘天气的原因. 结果表明:影响韩国沙尘天气的沙尘主要源地是蒙古国和中国内蒙古地区.沙尘天气发生在地面冷锋后部,高压伸展的前面;19日和20日沙尘暴发生后,沙尘沿着西北风输送,21日早晨影响韩国;PM10最高值达到 2 778.2 μg/m3,由于西北风较强,沙尘暴发生后很快影响到韩国,但在韩国持续的时间较短.  相似文献   

构造成矿理论的研究进展及在金矿找矿中的应用   总被引：8，自引：0，他引：8  

陈广浩  张湘炳  王岳军  彭渤  肖拥军  许德如 《地质科学》2002,37(4):462-472

本文综述了构造成矿学研究的基础,以及在区域构造成矿学、构造成矿流体、构造成矿定位机制、构造成矿动力学机制等方面研究的主要内容和最新进展及发展趋势.从构造成矿学的角度,深刻理解构造成矿学研究在成矿规律研究和找矿预测中的重要性.以江西洋鸡山金矿的找矿实践为例,阐述构造成矿学研究在实际工作中的成果,为今后进一步深入研究提供了依据.  相似文献   

沙丘背风侧气流的变化特征及其意义   总被引：6，自引：1，他引：6  

哈斯  王贵勇 《地理科学》2000,20(6):573-576

对腾格里沙漠东南缘格沙丘主、副梁和新月形形沙丘表面气流的野外发现分离流、附着未偏向流和附着偏向流等３种背风坡次生气流。前者以弱的反向流为特征，多发生在横向气流条件下，坡度较陡的背风坡上；后二者具有相对高的风速，多发生在坡度缓和的背风坡上，其方向在横向气流条件下保持原来的方向，在斜向气流作用下发生偏转，且其强度为原始风入射角的余统函数，根据３种次生气流强度，方向等特征，阐述了其相应的风成沉积过程和可能产生的层理类型，并对利用风成交错层理恢复古气流环境中的有关问题作了初步探讨。  相似文献   

"美丽冰冻圈"融入区域发展的途径与模式   总被引：2，自引：0，他引：2  

杨建平  哈琳  康韵婕  肖杰  陈虹举  贺青山 《地理学报》2021,76(10):2379-2390

在探讨“美丽冰冻圈”内涵的基础上,从自然属性与社会经济两个层面、致利与致害两条线,分析了“美丽冰冻圈”与区域可持续发展的关系,“美丽冰冻圈”、区域社会经济发展、人类福祉构成冰冻圈—人类社会经济复合命运共同体。基于中国冰冻圈要素及其变化影响的区域差异性,选取祁连山—河西地区、青藏高原三江源地区、横断山大香格里拉地区,分别代表冰冻圈水资源影响区、冰冻圈灾害影响区、冰冻圈旅游经济区,围绕冰冻圈水资源服务与绿洲经济、雪灾害风险与畜牧业经济、冰雪旅游与区域经济等核心问题,从冰冻圈资源服务与灾害风险视角,详细阐述了冰冻圈融入不同区域发展的途径与模式。在干旱半干旱内陆地区,冰冻圈主要以水源涵养、水量供给与径流调节服务,融入绿洲社会经济发展,是一种冰冻圈水资源支撑型区域发展模式;在青藏高原高寒区,冰冻圈生态环境决定了畜牧业经济的脆弱性,冰冻圈灾害负向影响畜牧业经济,是一种冰冻圈生态支撑+灾害影响型区域发展模式;在冰冻圈旅游经济区,直接依托冰雪资源发展冰雪旅游业,是一种基于冰冻圈资源的旅游经济驱动型区域发展模式。  相似文献   

增强弱磁异常信号的HILBERT变换方法     

贾建秀  王光杰  黄航 《吉林地质》2008,27(1)

在油气勘探中,与油气相关的磁异常由于其信号非常弱,通常很难从干扰中分离出来,可以证明希尔伯特变换滤波方法增强弱磁异常是一种有效方法,广东三水盆地的剖面处理解释说明了这一点。  相似文献   

NEW DISCOVERY OF RESHUI-TAOSTUO RIVER FAULT IN DULAN,QINGHAI PROVINCE AND ITS IMPLICATIONS          下载免费PDF全文

LI Zhi-min  REN Zhi-kun  LIU Jin-rui  HA Guang-hao  LI Zheng-fang  WANG Bo  WANG Lin-jian 《地震地质》1979,42(1):18-32

The 40km-long, NEE trending Reshui-Taostuo River Fault was found in the southern Dulan-Chaka highland by recent field investigation, which is a strike-slip fault with some normal component. DEM data was generated by small unmanned aerial vehicle(UAV)on key geomorphic units with resolution<0.05m. Based on the interpretation and field investigation, we get two conclusions:1)It is the first time to define the Reshui-Taostuo River Fault, and the fault is 40km long with a 6km-long surface rupture; 2)There are left-handed dislocations in the gullies and terraces cut by the fault. On the high-resolution DEM image obtained by UAV, the offsets are(9.3±0.5) m, (17.9±1.5) m, and(36.8±2) m, measured by topographic profile recovery of gullies. The recovery measurements of two terraces present that the horizontal offset of T₁/T₀ is(18.2±1.5) m and the T₂/T₁ is (35.8±2) m, which is consistent with the offsets from gullies. According to the historical earthquake records, a M5 3/4 earthquake on April 10, 1938 and a M_S5.0 earthquake on March 21, 1952 occurred at the eastern end of the surface rupture, which may be related to the activity of the fault. By checking the county records of Dulan and other relevant data, we find that there are no literature records about the two earthquakes, which is possibly due to the far distance to the epicenter at that time, the scarcity of population in Dulan, or that the earthquake occurred too long ago that led to losing its records. The southernmost ends of the Eastern Kunlun Fault and the Elashan Fault converge to form a wedge-shaped extruded fault block toward the northwest. The Dulan Basin, located at the end of the wedge-shaped fault block, is affected by regional NE and SW principal compressive stress and the shear stress of the two boundary faults. The Dulan Basin experienced a complex deformation process of compression accompanying with extension. In the process of extrusion, the specific form of extension is the strike-slip faults at each side of the wedge, and there is indeed a north-east and south-west compression between the two controlling wedge-shaped fault block boundary faults, the Eastern Kunlun and Elashan Faults. The inferred mechanism of triangular wedge extrusion deformation in this area is quite different from the pure rigid extrusion model. Therefore, Dulan Basin is a wedge-shaped block sandwiched between the two large-scale strike-slip faults. Due to the compression of the northeast and southwest directions of the region, the peripheral faults of the Dulan Basin form a series of southeast converging plume thrust faults on the northeast edge of the basin near the Elashan Fault, which are parallel to the Elashan Fault in morphology and may converge with the Elashan Fault in subsurface. The southern marginal fault of the Dulan Basin(Reshui-Taostuo River Fault)near the Eastern Kunlun fault zone is jointly affected by the left-lateral strike-slip Eastern Kunlun Fault and the right-lateral strike-slip Elashan Fault, presenting a left-lateral strike-slip characteristic. Meanwhile, the wedge-shaped fault block extrudes to the northwest, causing local extension at the southeast end, and the fault shows the extensional deformation. These faults absorb or transform the shear stress in the northeastern margin of the Tibet Plateau. Therefore, our discovery of the Dulan Reshui-Taostuo River Fault provides important constraints for better understanding of the internal deformation mode and mechanism of the fault block in the northeastern Tibetan plateau. The strike of Reshui-Taostuo River Fault is different from the southern marginal fault of the Qaidam Basin. The Qaidam south marginal burial fault is the boundary fault between the Qaidam Basin and the East Kunlun structural belt, with a total length of ~500km. The geophysical data show that Qaidam south marginal burial fault forms at the boundary between the positive gravity anomaly of the southern East Kunlun structural belt and the negative gravity anomaly gradient zone of the northern Qaidam Basin, showing as a thrust fault towards the basin. The western segment of the fault was active at late Pleistocene, and the eastern segment near Dulan County was active at early-middle Pleistocene. The Reshui-Taostuo River Fault is characterized by sinistral strike-slip with a normal component. The field evidence indicates that the latest active period of this fault was Holocene, with a total length of only 40km. Neither remote sensing image interpretation nor field investigation indicate the fault extends further westward and intersects with the Qaidam south marginal burial fault. Moreover, it shows that its strike is relatively consistent with the East Kunlun fault zone in spatial distribution and has a certain angle with the burial fault in the southern margin of Qaidam Basin. Therefore, there is no structural connection between the Reshui-Taostuo River Fault and the Qaidam south marginal burial fault.  相似文献   

遥感解译与断裂构造频率     

陈广浩 《华东地质学院学报》1992,(2)

新疆青河县克孜勒他乌地区,分布一系列金的矿点、矿化点。这些矿点、矿化点与构造,尤其是断裂构造有着密切的联系。本文试图用断裂构造频率来研究这种关系,并用遥感解译的方法获取断裂构造频率分布图,从中揭示出断裂构造与成矿的关系。这种方法比野外填图或从地质图中获取断裂构造频率的方法更简便,结果更可靠,是其他方法所不及的。  相似文献   

利用全球温盐观测剖面计划资料估算太平洋上层跨等密度面混合     

邓增安  韦广昊  于婷  魏红宇  康林冲  韩璐遥 《海洋学报(英文版)》2016,35(1):46-52

基于全球多年来积累的大量温盐观测剖面计划资料,利用精细尺度参数化方案估算了太平洋上层600米区域内的跨等密度面混合系数。结果表明,在不同季节跨等密度面混合系数的整体分布类似,但是细节上存在很大的不同。跨等密度面混合系数的加强与底部摩擦、海表面近惯性能量输入、赤道效应等因素密切相关。由于粗糙的地形,混合在东北太平洋门多西诺断裂带附近存在明显加强。同时,在南大洋西风带区域,由于大风引起的近惯性能量输入也导致了混合的强化。 与前人的研究结果相比,本文的估算具有更好的空间覆盖率以及更高的分辨率,更重要的是我们的结果体现了季节性变化。由于我们给出的是网格化产品,非常适合在数值模式中的应用。  相似文献