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1.
目前,利用航磁数据圈定磁性地质体边界的方法主要有航磁ΔT化极法、航磁ΔT化极垂向一阶导数法、总梯度模法和斜导数法等4种。云南宣威-贵州赫章地区火山岩分布面积广泛,下二叠统峨眉山玄武岩具有强磁性,而其他地层岩石磁性很低;为了圈定研究区内磁性地质体的目的,利用该区1∶5万航磁测量数据,阐述了ΔT化极法、化极垂向一阶导数法、斜导数法和总梯度模法等4种数据处理方法的地质应用效果,认为应根据有效磁化方向与地磁场方向是否一致来选用不同的航磁数据处理方法,以达到有效圈定地质的目的。 相似文献
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利用地质调查结合高精度磁法测量进行地质填图,推断玄武岩的喷发特征及地质演化历史。从平面剖面图可知,玄武岩线型溢流特明显,所圈定的异常,总体走为NE向,磁异常幅值西南向东北递增,反映出玄武前后演化历史,北部玄武岩晚于南部,玄武岩流由南逐渐向北部高处延裂缝漫溢超覆;磁异常零乱,梯度极大,磁异常变化急剧,正负异常迅速交替变化,反映出玄武岩的磁性特征;总体分布规律明显,异常排列紧密,勾画出玄武岩层状岩流特征。 相似文献
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南海地层岩石磁性在横向上呈现较大差异,而目前常用的磁界面反演方法多是针对常磁性磁界面进行的,若直接将其应用于南海这样磁性差异较大的地区,则反演结果中必定会带进很大误差。通过引入滑动时窗,对较常用的磁界面迭代反演方法进行研究和改进,获取适用于变磁性磁界面深度反演的方法,提供了一个可用于解决此种情况的方法手段。 相似文献
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五大连池玄武岩磁性地层以市容正向斯磁性地层为主，分布较广；也存在有松山反向期磁性地层，还发现了拉尚及贾拉米洛磁性事件的地层。 相似文献
7.
新疆黄土岩石磁学特征与地层性质的对应关系具有鲜明的区域特征.本文选取沙湾黄土剖面进行较为系统的岩石磁学分析.研究结果表明,沙湾剖面的磁性矿物组成与黄土高原及新疆北部其他黄土剖面相似,以亚铁磁性矿物(如磁铁矿、磁赤铁矿)为主要的载磁矿物,同时含有一定量的不完全反铁磁性矿物(如赤铁矿、针铁矿)和顺磁性矿物.假单畴(PSD)和多畴(MD)为样品的主要磁畴特征,部分土壤样品中磁性矿物磁畴状态表现为单畴(SD).进一步分析发现,磁化率与地层对应关系较为复杂,剖面3m以上地层中的磁化率及其他相关磁学参数与成壤强度呈现正相关关系,全新世以来发育的古土壤中磁化率值较高,细颗粒磁性矿物含量也较高;而3m之下地层中磁学参数显著表现为风力强度驱动变化模式.古风场强度的变化可能对剖面整体磁学性质具有一定的影响,成壤作用受到风动力条件的制约,主要决定了较细颗粒磁性矿物的含量变化.xARM/SIRM参数与磁化率相比对地层成壤强度的指示作用更为明显. 相似文献
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通过与粉尘堆积,以及玄武岩和片麻杂岩风化剖面磁组构的对比,探讨了以贵州平坝白云岩之上红色粘土剖面磁组构特征及其成因指示意义。红色粘土的各向异性较弱,并且不具有明显的沉积磁组构;母岩的组构特征对红色粘土磁化率各向异性没有明显的控制“痕迹” ;红色粘土与粉尘堆积物之间磁组构特征的明显差异,表明它们在物源和形成机制方面是不同的;红色粘土磁化率及磁组构特征反映出红色粘土中磁性矿物的物质来源和成因具有一定的特殊性。 相似文献
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安徽青阳—芜湖地区是长江中下游成矿带重要地区之一。为进一步寻找新的矿产地,2017年在该区进行了1∶5万航空磁法测量。在岩性填图工作中,开展了系统的岩(矿)石的磁化率调查,经分类统计实测资料,总结区内地层、侵入岩等各类岩(矿)石的磁性特征。结果表明:沉积岩一般呈弱磁性或无磁性;火山岩不发育,仅在白垩系、奥陶系个别地层有凝灰岩出露,有一定磁性;侵入岩不同岩性间磁化率具有一定的差异,可引起强度不同的正异常。不同岩性间磁化率差异为航磁岩性填图提供了依据。将实测磁化率应用于航磁岩性填图,圈定了姚村、麻姑山(推测隐伏)、桥头埠(推测隐伏)等岩体。该研究结果为该地区进一步找矿提供了参考信息。 相似文献
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东海地区重磁场特征及其地质意义 总被引：1，自引：0，他引：1
重磁方法是地球物理研究中的重要分支,其以位场理论为基础,具有在水平方向上的高分辨率能力并能够提供地壳深部结构的信息,从而对于研究沉积盆地的形成演化过程起着经济有效的作用.文章以东海地区近年的重磁数据为基础,分析了重磁场特征,布格异常值介于-160～460 mGal,在正值背景上发育一些局部的重力低圈闭,布格重力异常的主体走向为NE向,磁力异常值介于-200～+ 500 nT,磁力异常的主体走向为NE向.同时,利用磁异常数据计算了东海的磁性基底界面,磁性基底深度在4～12 km之间变化,各个地区磁性基底深度起伏变化不同,结合前人研究成果,认为东海地区广泛存在中生界地层. 相似文献
11.
A. D. Shukla N. Bhandari Sheela Kusumgar P. N. Shukla Z. G. Ghevariya K. Gopalan V. Balaram 《Journal of Earth System Science》2001,110(2):111-132
Chemical analysis of nine Deccan flow basalts at Anjar, Kutch, western India, indicates that all, except the uppermost flow
F-9, are alkaline. In their major and trace element composition, the alkali basalts resemble Ocean island basalts (OIB). Similarities
of many diagnostic trace element ratios (e.g. Sm/Nd, Ba/Nb,Y/Nb and Zr/Nb) are similar to those found in the Réunion Island
basalts. The uppermost basalt is tholeiitic and chemically resembles the least contaminated Deccan basalt (Ambenali type).
The Anjar basalts have iridium concentration ranging between 2 and 178 pg/g. Some of these values are higher by about an order
of magnitude compared to the Ir concentration in other basalts of the Deccan. A synthesis of chemical, palaeomagnetic and
geochronologic data enables us to construct a chemical and magnetic stratigraphy for these flows.
The three flows below the iridium enriched intertrappean bed (IT III) show normal magnetic polarity whereas all except one
of the upper basalts show reversed magnetic polarity. The sequence seems to have started in polarity zones 31N and probably
continued up to 28R or 27R. The results presented here support the view that Deccan volcanism in Kutch occurred on a time
span of a few million years. 相似文献
12.
由于湖北建始龙骨洞洞穴沉积地层年代存在疑问,对建始龙骨洞沉积剖面的154块样品进行了磁性地层学再研究,并建立了磁极性序列,结果显示龙骨洞沉积地层记录了单一的反极性序列,仅在距顶部0.93m处存在一个短期的正极性事件。将龙骨洞剖面极性柱与国际标准极性柱对比,反极性序列应对应于松山反极性时,正极性事件可对应于Cobb Mountain或者留尼旺正极性事件。如果龙骨洞沉积中的哺乳动物年代偏向早更新世,后一种对比方案可能更合理。由此龙骨洞哺乳动物群年龄为1.945—2.581Ma,古人类化石年龄为2.148—2.581Ma。 相似文献
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L. M. Alva-Valdivia A. Goguitchaichvili J. Cobiella-Reguera J. Urrutia-Fucugauchi M. Fundora-Granda J. M. Grajales-Nishimura C. Rosales 《Cretaceous Research》2001,22(6):705
A palaeo- and rock-magnetic study was carried out on the Jurassic–Cretaceous Guaniguanico Cordillera (15 sites, 112 oriented cores) in order to define a preliminary magnetostratigraphy and to obtain some constraints on the tectonic evolution of western Cuba. Rock-magnetic experiments indicate Ti-poor titanomagnetites as principal remanence carriers. Two magnetic phases seem to be present in a few samples: some spinels, which saturate at moderate magnetic fields and goethite, with higher coercivity. The presence of hematite (or mixture of spinels and hematite) is apparent in two units. In most cases the characteristic palaeodirections could be determined above 300°C. Eleven sites yield normal magnetic polarity and four reverse. The polarity zones can be tentatively correlated to chrons CM29–C24 in the reference geomagnetic polarity time scale. The mean palaeodirection calculated from all sites is Dm=335.7°, Im=43.1°, K=11, α95=12.3 and N=15. The corresponding palaeopole is Plat=66.4°, Plong=205.8°, K=13, and A95=11.1. This pole is not significantly different from North American Jurassic–Cretaceous poles. This suggests that no major latitudinal displacements and deformation have occurred since the Jurassic, in contrast to some previously proposed tectonic models. 相似文献
14.
泥河湾盆地东谷坨剖面的环境磁学研究表明泥河湾盆地湖相地层的物源具有多重性,既有来自周边山地的风化碎屑,又有来自西北和北方沙漠地区的粉尘物质,导致了其古环境和气候记录的复杂性.湖相地层除记录了松山反极性时晚期和布容正极性时这两个大的极性时段以外,还记录了哈拉米洛极性亚时和另外3个短期极性漂移事件.磁组构参数表明东谷坨剖面的地层是在正常的重力分异条件下沉积的,且自沉积结束以来没有受到明显的后期扰动.磁化率最大轴的方位角显示东谷坨剖面处乃至泥河湾盆地东部的古水流方向主要(或大多数时候)为北北西-南南东向. 相似文献
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NEW MAGNETOSTRATIGRAPHIC AND SEDIMENTOLOGIC RESULTS FROM TERTIARY SEDIMENTS OF THE HOH XIL BASIN, NORTHERN QINGHAI-TIBET PLATEAU: IMPLICATIONS FOR THE CENOZOIC TECTONIC HISTORY OF THE TIBET PLATEAU 相似文献
16.
V. P. Rodionov 《Stratigraphy and Geological Correlation》2016,24(5):464-485
The available paleomagnetic data on the Verkhnyaya Lena Group from different areas of the southern Siberian Platform are revised. The group rests unconformably upon the Lower Cambrian strata and is overlain by Lower Ordovician rocks, which determines conditionally the age of its red-colored deposits. Paleomagnetic correlation of composite sections through the region using defined zones of normal and reversed magnetic polarity serves as a basis for development of the magnetostratigraphic scale for the Verkhnyaya Lena Group. The scale includes nine magnetic zones, which play the role of markers; seven of them are traceable in all the examined sections of the southern Siberian Platform. By the distribution of zones with normal (N) and reversed (R) polarity, the magnetostratigraphic scale is subdivided into three parts. Its lower part is represented by reversed polarity, which is characteristic of the second half of the Lower Cambrian. The middle part is characterized by frequently alternating zones with normal and reversed polarity corresponding to the Middle Cambrian. The upper part of the scale corresponds to the interval of reversed polarity characteristic of the Upper Cambrian and Lower Ordovician. The Middle–Upper Cambrian boundary is located near the last N–R reversal of the geomagnetic field in the Cambrian. The magnetostratigraphic scale includes nine orthozones united into three superzones, which are attributed to two hyperzones of magnetic polarity. 相似文献
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旱峡剖面新民堡群的古地磁学研究 总被引：1，自引：0，他引：1
根据岩石剩磁测试资料所反映的古地磁场极性变化特征,甘肃玉门旱峡剖面原先厘定为下白垩统的新民堡群包括7个正向极性亚时带和7个反向极性亚时带。通过与国际中生代极性年表和深海沉积物极性年表的对比,新民堡群实际上可分为两个地层单位:以第三个反向极性亚时带为界(从下往上数),下部层段属于上侏罗说(厚约460m),上部层段属下白垩统(厚约636m)。剖面玄武岩脉的喷溢时代应早于中新世,晚于旱白垩世,分为两期岩浆活动。 相似文献
18.
HAN Jian’en SHAO Zhaogang CHEN Qiguang XU Biao ZHANG Qianqian YU Ji MENG Qingwei ZHANG Xuefeng WANG Jin ZHU Dagang 《《地质学报》英文版》2018,92(6):2067-2078
The Xining basin is located in the northeastern margin of the Qinghai-Tibet Plateau. It is a rift basin formed in Mesozoic and Cenozoic and structurally belongs to the intersection of Kunlun and Qilian Mountains. Cenozoic fluvial and lacustrine sedimentary strata are continuous in the Xining basin, with a thickness of more than 800 m, completely recording the deformation uplifting, weathering and denudation history and climate change process of the northeastern plateau. Currently, early Miocene Xijia fauna, early Middle Miocene Danshuilu fauna and late Middle Miocene Diaogou fauna are discovered in the Xining basin, which provide an important basis for the stratigraphic correlation of the Cenozoic strata in the Xining basin. However, in the next few decades, there are no reports about the large mammal fossils in the Xining basin, especially about late Miocene fauna. The author discovered a large amount of mammal fossils in the Neogene sedimentary strata in Huzhu area, Xining basin. According to the identification results of the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, these fossils mainly included Hipparion dongxiangense, Chilotherium sp., Parelasmotherium sp., Stephanocemas sp. and Kubanochoerus sp. and their age was early Late Miocene. Since the discovery of this set of fossils directly filled the blank that there were no large mammal fossils in the Xining basin in Late Miocene, it was very important for studying the magnetic stratigraphic chronology of fossil-forming strata and establishing the paleomagnetic chronology scale plate of mammal fossils. In this paper, the paleomagnetic data of the fossil-forming stratigraphic profile, Banyan profile, were measured and the paleomagnetic records were collected through high density sampling, and finally the paleomagnetic polarity column of the profile was established. The results showed that five positive and five negative polarity segments were recorded in Banyan profile, which corresponded well to the polarity between C3Br.1n-C4n.2n in the standard polarity column. The age of profile top was about 7.25 Ma and profile bottom was about 8.4 Ma, with an age range of 1.15 Ma. The mammal fossils discovered this time were exposed between positive and negative polarities N5 and R5 at the bottom of the profile, corresponding to C4r.1r at negative polarity and C4n.2n at positive polarity in the standard polarity column. The age of mammal fossils was about 8.3 Ma. The paleomagnetic chronology of the strata and paleontological fossils determined the absolute age of late Miocene mammal fossils and expanded the upper age of late Miocene Xianshuihe Formation (N1xn) in the Xining basin, which had provided new basic data for further studying the stratigraphic deposition and correlation of late Cenozoic strata and regional environmental evolution. 相似文献
19.
通过对昆明滇池湖盆三个钻孔较密集的古地磁采样和系统的测量,获得了该区沉积500余米厚新生代地层的较为完整的磁极性剖面。自上至下测定出了三个极性带(布容、松山、高斯)。在松山反极性带内判别出了4个极性亚带(贾拉米洛、滇池、奥杜威、留泥汪);高斯正极性带内判别出了2个极性亚带(凯纳、猛犸);布容正极性带内分辨出了6~9个短暂的地磁极性变化。根据本文研究结果,参考孢粉、介形虫,腹足类化石及碳14测年资料,对照国际地磁极性年表,确定出滇池湖盆晚新生代地层包括了整个第四系和上新统晚期部分,并对该套地层进行了具体的划分和粗略的对比。 相似文献