古代生物分子在第四纪研究中的应用   总被引：4，自引：1，他引：4  

赖旭龙  杨洪 《第四纪研究》2003,23(5):457-470

从第四纪化石和沉积物中获得的古代生物分子为第四纪研究者提供了丰富和独特的有关古代生物、遗传和古环境信息的定量和高分辨率的数据.过去10多年的研究证实来自第四纪材料中的各种古代生物分子的分离、鉴定和应用的能力在不断增加.文章总结了古代生物分子在第四纪研究中的最新进展,主要包括以下几个方面的内容:1)不同类型的古代生物分子在地质体中的保存和降解;2)古DNA和古蛋白序列中的生物遗传学信息;3)单体分子同位素与第四纪古环境和古气候研究;4)建于古代生物分子水平上的第四纪年代学.作者预见对第四纪地层中的原位和分散保存的古代生物分子的研究将在广度上以多分子综合研究而深度上与单体分子同位素技术相结合,为第四纪科学家们提供大量解决地质学和演化生物学问题的高精度数据.随着地球化学和分子生物学技术的不断改进以及人们对古代生物分子的降解过程和机制的进一步理解,对古代生物分子的研究无疑将进一步促进和推动第四纪科学研究的发展.  相似文献   

松辽盆地南部十屋断陷古构造对营城组扇三角洲发育的控制   总被引：2，自引：3，他引：2  

董福湘  刘立  何兴华  马艳萍 《吉林大学学报(地球科学版)》2003,33(4):464-468

在恢复古构造的基础之上，对比了松辽盆地南部十屋断陷营城组沉积时期的古构造格局与现令构造格局的异同。古构造对扇三角洲沉积体系的控制作用主要表现在：(1)主要基底断裂控制了扇三角洲的展布方向；(2)倾向与物源方向相反的断层和古地貌阻滞了扇三角洲的展布；(3)沉降中心控制了扇三角洲前缘的纵向叠置和发育。  相似文献   

陕甘宁盆地陇东地区长8油组厚层非均质砂体的沉积学解剖   总被引：15，自引：3，他引：15  

郑希民  宋广寿  王多云  李凤杰  王志坤  李树同  王峰  刘自亮 《沉积学报》2003,21(2):272-277

通过对延长统长8段厚层砂岩沉积岩石学和层序地层学研究,将其分为两类,一类是由多期单一成因的分流河道砂岩叠加构成;另一类是由三角洲前缘的水下分流河道、河口坝、坝顶席状砂和滑塌砂等多种沉积微相以不同的组合形式叠加构成。首次提出在“高可容纳空间,高沉积通量”背景下,只有经过特殊水动力条件(淘洗)改造后形成的被我们称之为坝顶席状砂的砂岩才有可能成为相对高孔、高渗的优质储层。  相似文献   

Determination of silica sand stiffness     

G. R. Lashkaripour  R. Ajalloeian 《Engineering Geology》2003,68(3-4):225-236

Site investigation and evaluation of properties of soil or rock are important aspects of geotechnical design. Determination of the ground stiffness is one of the important parameters in geotechnical engineering. Since the measurement of shear modulus is very sensitive to soil disturbance, especially for sand, determination of the stiffness of soil in the field is more reliable than in laboratory tests on sampled specimens. Measurement of shear modulus is one of the most common applications of self-boring pressuremeter testing. As an in situ device, the pressuremeter provides a unique method for assessing directly the in situ shear modulus of a soil. This paper describes a laboratory study of silica sand stiffness, which varies with stress level and strain amplitude. The results show that the elastic shear modulus value is mainly dependent on the value of the mean effective stress and relative density.  相似文献   

An experimental investigation of LNAPL migration in an unsaturated/saturated sand   总被引：4，自引：0，他引：4  

Radhey S. Sharma  Mostafa H. A. Mohamed 《Engineering Geology》2003,70(3-4):305-313

Accidental spills of hydrocarbons, such as Light Non-Aqueous Phase Liquids (LNAPLs), are one of the most common sources of subsurface contamination. Migration of LNAPL in a porous medium is influenced by various factors such as the number of fluids present in the unsaturated/saturated zones and the proportion of pores occupied by each fluid. The results for relationship between matric suction and degree of saturation are presented in this paper for water–air, water–LNAPL and LNAPL–air systems in a sand. A simple and reliable setup using Buchner funnel was designed to obtain these relations. It was found that the relationship between matric suction head and degree of saturation is hysteretic for all the fluid systems (water–air, water–LNAPL and LNAPL–air). Furthermore, the amount of hysteresis depended upon the fluid system, with the maximum hysteresis occurring for water–air system. The results suggest that the amount of trapped air depends upon the reversal degree of saturation from drying to wetting.  相似文献   

Wave-influenced deltas: geomorphological implications for facies reconstruction   总被引：5，自引：0，他引：5  

Janok P. Bhattacharya  Liviu Giosan† 《Sedimentology》2003,50(1):187-210

ABSTRACT A process‐based facies model for asymmetric wave‐influenced deltas predicts significant river‐borne muds with potentially lower quality reservoir facies in prodelta and downdrift areas, and better quality sand in updrift areas. Many ancient barrier‐lagoon systems and ‘offshore bars’ may be better reinterpreted as components of large‐scale asymmetric wave‐influenced deltaic systems. The proposed model is based on a re‐evaluation of several modern examples. An asymmetry index A is defined as the ratio between the net longshore transport rate at the mouth (in m³ year^?1) and river discharge (in 10⁶ m³ month^?1). Symmetry is favoured in deltas with an index below ≈ 200 (e.g. Tiber, lobes of the Godavari delta, Rosetta lobe of the Nile, Ebro), whereas deltas with a higher index are asymmetric (e.g. Danube – Sf. Gheorghe lobe, Brazos, Damietta lobe of the Nile). Periodic deflection of the river mouth for significant distances in the downdrift direction occurs in extreme cases of littoral drift dominance (e.g. Mahanadi), resulting in a series of randomly distributed, quasi‐parallel series of sand spits and channel fills. Asymmetric deltas show variable proportions of river‐, wave‐ and tide‐dominated facies both among and within their lobes. Bayhead deltas, lagoons and barrier islands form naturally in prograding asymmetric deltas and are not necessarily associated with transgressive systems. This complexity underlines the necessity of interpreting ancient depositional systems in a larger palaeogeographic context.  相似文献   

西藏纳木错晚更新世以来湖面变化和藏北高原古大湖的演化     

朱大岗  赵希涛  孟宪刚  吴中海  邵兆刚  马志邦  杨朝斌  王建平 《地质通报》2003,(Z1)

根据西藏纳木错及邻区发现的多处湖岸阶地和高位湖相沉积,确定了藏北高原古大湖的存在。水准测量表明,在纳木错沿岸发育了6级湖岸阶地,以及拔湖48～139.2m的高位湖相沉积;在拔湖26m以下,发育有8～30条湖岸堤;一条明显的湖蚀凹槽则集中出现在拔湖17.5～19.8m的高度上,与纳木错和仁错的分水垭口的高度相当。纳木错沿岸和邻区湖相或湖滨相沉积物的铀系年龄测定表明,高位湖相沉积形成于115.9～71.8kaB.P.的晚更新世早期;第6至第2级阶地形成于53.7～28.2kaB.P.的晚更新世中晚期;与湖蚀凹槽相当的湖滨相沉积则稍早于29.3kaB.P.;第2至第1级阶地,14C测定结果为2350～10390aB.P.。  相似文献   

粘粒含量对南京粉细砂液化影响的试验研究   总被引：16，自引：1，他引：16  

刘雪珠  陈国兴 《地震工程与工程振动》2003,23(3):150-155

南京粉细砂是一种以片状颗粒成分为主的粉细砂，与通常的圆形颗粒石英砂有一定区别，片状颗粒成分使得南京粉细砂具有各向异性的性质。通过对不同粘粒含量的南京粉细砂进行液化试验，分析其试验结果发现：对于粘粒含量ρc＝5％、10％和15％三种情况，在均压固结情况下，当南京粉细砂达到初始液化时，采用变形标准和孔压标准是一致的；而偏压固结时，只能采用变形标准作为南京粉细砂达到初始液化的标准，此时振动孔压仅达到围压的50％-70％。粘粒含量对南京粉细砂的抗液化强度影响很大，随粘粒含量增加，在不同固结比时，其抗液化强度并不是单调变化，而是在粘粒含量ρc＝10％左右处于一个低谷，其抗液化强度最低。  相似文献   

一次沙尘暴中尺度低压和沙尘输送的数值模拟   总被引：2，自引：0，他引：2  

王强  章克俭  张静  全建瑞 《干旱气象》1997,(4)

利用ＰＳＵ／ＮＣＡＲ中尺度数值模式（ＭＭ４），以常规观测资料为初始场，成功地模拟了造成“９４．４．５”沙尘暴天气的主要天气系统张掖热低压。并通过给原有的中尺度模式系统加入沙尘输送方程和驱动地面沙尘抬升参数化方案，用改进后的中尺度数值模式系统，成功地模拟了沙尘抬升和输送，与实况比较一致。  相似文献   

一次沙尘暴天气及沙尘输送过程的数值模拟   总被引：15，自引：3，他引：15  

刘毅 《南京气象学院学报》1997,20(4):511-517

动用ＭＭ４中尺度动力学模式结合沙尘气溶胶传输模式。模拟分析了１９９２年４月２２日发生的一次沙尘暴天气及沙尘输送过程。  相似文献