国外^129I在水文地质中应用综述     

刘存富 《地质科技情报》1992,11(4):87-91

本文讨论了~(129)Ⅰ的三个起源:大气起源、地下起源和人工起源,通过三个实例,介绍了~(129)Ⅰ在石油勘探、水文地质研究和环境监测中的应用进展,并且指出了未来研究方向。  相似文献   

热剩磁偏离古地磁场的校正及其应用     

胡守云  阎桂林 《地球物理学进展》1993,8(3):114-121

根据含多畴磁铁矿岩石的热剩磁(TRM)及其磁化率各向异性(AMS)张量间的特征值的比值关系,推导出一种因AMS 而引起的TRM 方向偏离外磁场方向的具体校正公式,并将其成功地应用到中国月山闪长岩体及法国Flamanville 花岗岩体的古地磁研究中.  相似文献   

青藏高原东缘鲜水河断裂带磁组构特征及构造意义   总被引：2，自引：0，他引：2  

陈应涛  张国伟  鲁如魁  谢晋强  郭泱泱 《岩石学报》2013,29(3):977-989

为了探究鲜水河断裂带的几何学、运动学特征,在野外构造、显微构造分析基础上,研究了鲜水河断裂带296块构造岩定向样品的磁组构特征和热磁特征,结果显示样品的平均磁化率km值总体较小,属微弱磁性到弱磁性;热磁实验及其显微构造表明顺磁性的页硅酸盐(如黑云母)等矿物对糜棱岩类样品磁化率贡献较大;磁化率各向异性度PJ总体较大,表明鲜水河断裂带构造变形强烈;磁化率椭球体形状参数T总体大于0,扁率E总体在1附近分布,说明鲜水河断裂带磁化率椭球体以扁圆形为主,整体上磁面理较磁线理发育,进一步显示出鲜水河断裂带构造变形样式以剪切、压扁为主,伴有拉伸的构造变形,同时也反映出鲜水河断裂带多次变形的综合特征;最小磁化率主轴Kmin方位表明鲜水河断裂带北段和南段分别受近EW向和NE-SW向主压应力控制;同时Kmin方位及其倾伏角特征显示鲜水河断裂带总体以左行走滑剪切为主,北段两侧块体在鲜水河断裂带两次不同的构造活动时期,各自有一定的相对抬升,但抬升幅度均不大;南段则是SW块体相对NE块体抬升,抬升幅度较大;整个断裂带特征显示出鲜水河断裂带在向南发展逐渐转化为挤压构造,这可能与青藏高原物质的向东逃逸受阻以及鲜水河断裂带与龙门山断裂带在此交接的地质背景不无关系.  相似文献   

New insights into the deformation of a Middle Pleistocene glaciotectonised sequence in Norfolk,England through magnetic and structural analysis     

Edward J. Fleming  Carl T.E. Stevenson  Michael S. Petronis 《Proceedings of the Geologists' Association. Geologists' Association》2013

North Norfolk is a classic area for the study of glacial sediments with a complex glaciotectonic deformational history, but the processes leading to the formation of some structures can be ambiguous. Anisotropy of magnetic susceptibility (AMS) analyses, providing quantitative fabric data, have been combined with the analysis of visible structures and applied to the Bacton Green Till Member, exposed at Bacton, Norfolk. Thermomagnetic curves, low temperature susceptibility and acquisition of isothermal remanent magnetism (IRM) reveal that the magnetic mineralogy is dominated by paramagnetic phases. The magnetic foliation is parallel to fold axial planes and weakly inclined to bedding, whilst the magnetic lineation is orientated parallel to stretching, indicated by the presence of stretching lineations and the trend of sheath folds. Variations in the orientation of the magnetic lineation suggest that the Bacton section has been subject to polyphase deformation. After subaqueous deposition, the sequence was overridden by ice and glaciotectonically deformed which involved stretching initially north–south, then east–west. These results show that AMS can be used to detect strain in three dimensions through a glaciotectonite where paramagnetic mineralogy is dominant. This approach therefore provides further support to the use of AMS as a fast, objective and accurate method of examining strain within deformed glacial sediments.  相似文献   

The Late‐glacial reoccupation of the British Isles and the Creswellian     

R. N. E. Barton  R. M. Jacobi  D. Stapert  M. J. Street 《第四纪科学杂志》2003,18(7):631-643

This paper presents a review of AMS radiocarbon dating evidence for human occupation of Britain during the Late‐glacial Interstadial. The dates are all on humanly modified materials, including artefacts, and on human bone. The CalPal program is used to test whether the earliest evidence of human presence shows any correlation with more widespread climatic events, and if the British chronology differs significantly from that of neighbouring regions of northwest Europe. In the second part of the paper a number of well‐dated sites with British Late Upper Palaeolithic ‘Creswellian’ technology are examined and compared with lithic assemblages from The Netherlands and Belgium. The main conclusions of this work are that expansion of human populations into the northern edge of the upland zone just before or at the beginning of GI‐1 was followed by repopulation of the British Isles possibly with very little time‐lag. The British Creswellian sites offer evidence of this earliest resettlement, which is mainly focused on the upland margins of western and central Britain. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

江苏兴化ZK10孔第四纪多重地层研究     

劳金秀  杨祝良  于俊杰  蒋仁  彭博  曾剑威  刘晓燕 《地质通报》2016,35(10):1705-1714

通过对江苏兴化ZK10孔岩石地层、生物地层、磁性地层及年代地层的研究,确定了该孔第四纪年代地层序列:1第四纪底界置于松山/高斯极性世分界处,埋深212m,距今2.58Ma。下更新统包括五队镇组下段、中段及上段的中下部,对应孢粉组合Ⅰ-1和Ⅰ-2。2早、中更新世界线与布容/松山极性世界线吻合,距今0.78Ma,埋深约120m,位于孢粉Ⅰ-2与Ⅱ带的分界处。中更新统包括五队镇组上段顶部、小腰庄组下段及上段的中下部。五队镇组是包含下、中更新统的跨时岩石地层单位。3中、晚更新世界线埋深81.5m,120ka BP左右,置于孢粉带Ⅱ与Ⅲ-1的分界处,与小腰庄组和灌南组分界线基本吻合。上更新统包括小腰庄组上段上部及灌南组。小腰庄组是包含中、上更新统的跨时地层单位。上更新统包括Ⅲ-1、Ⅲ-2、Ⅳ和Ⅴ孢粉带。4晚更新世与全新世界线埋深12.25m,距今10ka BP左右,位于Ⅴ与Ⅵ孢粉带分界处。全新统为淤尖组,对应孢粉Ⅵ带。  相似文献   

渤海湾西南部平原DC01孔晚更新世以来的地质环境变化     

李建芬  王福  陈永胜  方晶  商志文  田立柱  施佩歆  姜兴钰  王宏 《地质通报》2016,35(10):1590-1599

通过对渤海湾西南部平原DC01孔的岩石地层学、生物地层学及年代地层学和地球化学研究,重建了该地区自晚更新世以来的地质环境演化过程。全新世之前,研究区经历了由河流-盐沼-潮间带上部/低盐沼-河口湾-泻湖-淡化泻湖的环境转化过程;进入全新世之后,该区经历了由湖沼到河流的环境转化过程。埋深22.4~12.7m发育近10m厚的弱海相沉积,AMS~(14)C年龄表明,该层沉积形成时间早于4.35ka cal BP,可能属于MIS 3早期(6.0~5.5ka cal BP)或更早的MIS 5期(12~8ka cal BP)。恢复了该时期的相对古海面,最高可达-13.31m。DC01孔缺失MIS 4~2或MIS 2时期的沉积。  相似文献   

Two Tephra Layers Bracketing Late Holocene Paleoecological Changes in Northern Germany     

Christel van den Bogaard  Walter Drfler  Rainer Glos  Marie-Jose Nadeau  Pieter M. Grootes  Helmut Erlenkeuser 《Quaternary Research》2002,57(3):314

Paleoecological records from two Holocene peat bogs in northern Germany are linked by two microscopic volcanic ash layers, correlated by petrology and geochemistry to explosive volcanism on Iceland. The younger “Microlite tephra” cannot be correlated to any known eruption, while the older tephra layer is identified as a deposit of the Hekla 3 eruption. The tephra layers are dated by an age–depth regression of accelerator mass spectrometry ¹⁴C ages that have been calibrated and combined in probability distributions. This procedure gives an age of 730–664 cal yr B.C. for the “Microlite tephra” event and 1087–1006 cal yr B.C. for the Hekla 3 event. Accordingly, the tephra layers were deposited during the late Bronze Age. At this time, human settlement slowly increased pressure on the environment, as indicated by changes in woodland pollen composition at the two bogs. The tephra-marker horizons further show that the palynologically defined transition from the Subboreal to the Subatlantic Period is synchronous in the investigated area. However, the macroscopic visible marker in peat, the change from fibrous to sapric peat, the “Schwarztorf-Weißtorf-Kontakt,” is asynchronous. Bog vegetation did not immediately react in unison to a climatic change at this pollen zone boundary; instead, the timing of vegetation change depended on the location within the bog.  相似文献   

Magnetic fabric and its significance in the Florianópolis dyke swarm, southern Brazil     

Maria Irene Bartolomeu Raposo 《Geophysical Journal International》1997,131(1):159-170

Magnetic fabric was determined by applying the anisotropy from the low-field magnetic susceptibility (AMS) technique in 62 mafic dykes from the Mesozoic Florianópolis (Santa Catarina Island) dyke swarm, southern Brazil. These dykes cut the crystalline basement rocks, which are mainly Proterozoic. They are vertical or subvertical in dip and trend mainly NE, although NW-trending dykes are also found. Dykes are tholeiitic in composition and are geochemically similar to those from the Ponta Grossa swarm. Thicknesses vary from 0.3 to 60 m. Polished sections show that titanomagnetites carry the AMS in these dykes. Hysteresis parameters show that the magnetic minerals fall in the PSD range. Two types of magnetic fabric are recognized. Type I is characterized by K ₁- K ₂ parallel to the dyke wall, representing magma flow within the dykes; type II, with K ₁- K ₃ parallel to the dyke wall, was found in four dykes. Type I is found in 94 per cent of the dykes, and approximately 20 per cent of these have K ₁ inclinations of less than 30°, suggesting horizontal or subhorizontal flow. About 80 per cent have K ₁ inclinations of greater than 30°, due to inclined to vertical flow. The comparison of AMS studies from both the Florianópolis and the Ponta Grossa dykes suggests a source position closer to Santa Catarina Island than the Ponta Grossa arch.  相似文献   

A deformed Pliocene-Quaternary alluvial and red paleosol succession in the Eastern Betics: Paleomagnetic,rock-magnetic and sedimentological pilot study     

Jaume Dinarès-Turell  Pedro Alfaro  Jesús Soria 《Studia Geophysica et Geodaetica》1995,39(4):405-419

Summary An integrated pilot paleomagnetic and sedimentological study has been conducted in the Neogene-Quaternary infilling materials of the Bajo Segura Basin (Eastern Betics, SE Spain). The studied sediments belong to the youngest (late Pliocene-Quaternary) lithostratigraphic unit of the basin (P-Q unit). The statistical analysis of tectonic striations and stylolitic dissolutions on the conglomerate limestone clasts indicates a NNW-SSE maximum compression direction. This is in accordance with the principal susceptibility axes, determined from the anisotropy of magnetic susceptibility measurements (AMS) of the interbedded siltstones where the Kmax axis group in a subhorizontal N 080° E direction.A total of 45 core samples have been collected from 16 stratigraphic siltstone levels encompassing the described section at Crevillente with the aim to establish a magnetochronology. Upwards in the section the NRM intensity and bulk susceptibility vary from 10^–2 to 10^–3 A/m and from 1550 to 100 × 10^–6 SI, respectively. The mean characteristic remanent magnetization (ChRM) after bedding correction (Dec/Inc = 10°/60°, ₉₅ = 8.7°, k = 15.9) is deviated slightly towards the E from the reference N direction, and could reflect a deflection related to the observed magnetic fabric although no clear correlation exists with AMS parameters. The derived magnetostratigraphy reveals only one reversal boundary within the upper third of the section, delimiting an upper reversal magnetozone which has been tentatively correlated with the Olduwai subchron close to the Plio-Pleistocene boundary.Pilot and preliminary rock-magnetic experiments and standard X-ray difraction (XRD) analysis have been performed on typical samples in order to establish the carriers of magnetization and characterize the sedimentological and magnetic-acquisition processes in these sediments. Magnetic carriers seem to be dominated by magnetite with a relative grain size within the PSD state (pseudo single-domain) threshold, but closer to the MD (multi domain) threshold, which favours the detrital origin for the magnetite.  相似文献