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1.
撞击坑统计定年法的基本原理是首先得到月球表面撞击坑密度分布的一般规律(即产率函数),然后将其应用到Apollo和Luna任务采样的区域中,得到大干特定直径(常用1 km)的撞击坑密度,然后在该密度和样品的同位素年龄之间建立函数关系(即年代函数).在对没有样品的地质单元进行年龄分析时,首先从遥感影像解译撞击坑,然后根据产率函数求解大于指定直径撞击坑的密度,最后将其代入年代函数中求解该区域的地质年龄.根据其它行星与月球撞击环境的差异等因素,该方法已经推广到其它行星表面地质年龄的研究中.本文详细分析了撞击坑统计定年方法的原理,以及在应用中需要注意的问题. 相似文献
2.
通过撞击坑的大小频率计算月表的地质年龄是一种行之有效的方法,包括累积分布法和相对分布法。其中累计分布法在已知撞击坑直径范围的基础上,可分为3种年代函数计算月表的地层单元,分别是Melosh 和 Vickery 1989 (直径大于4 km 撞击坑), Neukum 1983(直径大于1 km撞击坑)和李坤等2012(直径小于1 km 撞击坑)。应用高分辨率影像SELENE TC(10m/pixel)数据,完成了Apollo 14及Apollo 16登月区域地层单元的解译,并应用撞击坑直径频率统计方法获取同一地层单元的形成年龄。通过与Apollo登月区域样品同位素年龄对照,得出Neukum 1983(直径大于1 km撞击坑)相对于其他几种方法更加准确,同时分析了撞击坑的退化、次级撞击坑影响等相关问题。 相似文献
3.
玉兔二号月球车在嫦娥四号着陆区发现了许多坑缘呈破碎石块状的小型撞击坑,其直径大多在亚米级,过去对于这种小尺度撞击坑的研究大多源于Apollo、Surveyor、Ranger系列任务,然而当时获取的影像质量较低,且并未覆盖月球背面.小尺度撞击坑在月球表面分布十分广泛,与月球最表层的演化密切相关,因此对其展开研究具有重要的意义.本文利用嫦娥四号任务获取的高分辨率全景影像,统计了8、9、11～15月昼影像中新鲜撞击坑的直径、频数、深度等信息,并根据这些撞击坑和周围石块的形态特征,推测这些坑应该形成于不同方向的二次撞击事件,这为揭示玉兔二号月球车行进途中观测物质的来源提供了重要信息.小型二次撞击坑从深径比中难以与一次撞击坑区分,且一般处于饱和状态,因此应避免使用小尺寸的撞击坑进行定年. 相似文献
4.
撞击坑统计定年法及对月球虹湾地区的定年结果 总被引：2，自引：0，他引：2
撞击作用是行星形成和表面重塑的重要地质过程,记录和揭示了行星的演化历史.撞击作用形成的撞击坑可用于研究天体表面地质单元形成的时间.依据内太阳系天体表面的撞击历史,总结了通过对撞击坑的直径和频率分布进行统计,计算天体表面模式年龄的原理和方法.在此基础上,利用美国“月球勘测轨道器(LRO)”广角相机获得的图像,对月球虹湾地区的撞击坑进行了直径-频率分布统计研究,获得其3个主要地质单元的绝对模式年龄分别为3.33 Ga、3.21 Ga和2.60 Ga,有效限定了本区主要地质事件发生的时间. 相似文献
5.
撞击坑统计技术在行星表面定年应用中的误区 总被引：1，自引：0，他引：1
撞击坑大小-频率统计技术在其理论基础与实际应用中存在一定的局限性,且尚未引起国内外行星地质学界的广泛关注.使用该技术分析行星表面的年龄时,应注意:(1)由于晚期大轰击事件的存在,该技术不能用于估算内太阳系天体表面老于~38亿年的地质体的年龄;(2)由于内、外太阳系的撞击历史不同,不能直接使用月球上的撞击坑的产生方程估算外太阳系天体表面地质单元的绝对模式年龄;(3)由于二次撞击坑的干扰,须谨慎使用小撞击坑统计估算年龄;(4)分析撞击坑统计的结果前,首先需分析统计区的饱和状态;(5)避免使用太阳入射角小的影像数据统计撞击坑,避免选择地形复杂的区域作为统计区.另外,建议优先使用相对分布法、并结合累积分布法分析撞击坑统计的结果. 相似文献
6.
在太阳系的形成和演化过程中,发生在天体物质间的撞击作用是最重要的地质过程之一.撞击构造是地外天体表面最常见的地貌单元,大部分天体的地貌演化主要受撞击作用控制.撞击过程产生的温度、压力和应变速率比岩石圈内的其他地质过程高多个数量级,形成广泛分布的撞击产物,如气化物、熔融物、冲击变质和变形等.虽然撞击过程转瞬即逝,撞击作用向天体注入能量并改变其内、外结构,对天体的圈层系统产生长远影响.持续撞击在天体表面累积了大量的撞击坑,撞击坑的空间分布反映了受外来撞击的历史.内太阳系在～3. 8 Ga前的撞击频率更高,但是大量撞击盆地是否灾变式的密集形成仍在持续争议;～3. 8 Ga以来的撞击频率趋于稳定,但是缺乏具有明确事件指代性的标定样品.在同一天体上,撞击坑的空间密度指示了相应地质单元的形成时间,因此撞击坑统计常被用于估算地外天体表面地质单元的相对年龄.基于月球软着陆探测任务返回的样品,前人已约束了不同直径的月球撞击坑的形成频率,进而建立了使用撞击坑统计估算月球表面地质单元的绝对模式年龄的方法.另外,内太阳系天体可能经历了相似的撞击历史,因此地-月系统的撞击频率已被缩放至其他类地行星.撞击坑统计是探索太阳系天体的撞击历史、遥估地外天体表面的相对和绝对年龄的主要方法,也是行星地质研究的基本工具.该方法的整体可靠性已得到大量实验的验证.同时,该方法在理论基础和技术细节上还存在大量的不确定性.修正该方法是完善太阳系撞击历史的重要研究内容,也是未来采样返回探测任务的重要科学目标. 相似文献
7.
撞击坑统计方法是估计行星表面年代的一种有效方法。利用小尺度撞击坑大小频率分布测定撞击年龄,并分析了计算模型的不确定性、撞击坑的退化、次级撞击坑影响等相关问题。选用嫦娥二号获取的虹湾地区高精度影像数据进行验证,确定该区域退化参数为350 m,直径小于30 m时次级撞击坑密集分布,使用350 m以上的撞击坑计算得到撞击年龄为3.16 Ga,误差控制在0.1 Ga以内。 相似文献
8.
撞击坑是月球表面广泛分布的重要构造形态,占据了月球表面的大部分面积。撞击坑的直径差别很大,从几微米到数百千米,其退化程度与形成年代具有密切关系。为了研究不同地质年代形成的撞击坑直径大小及其演化规律,需采用量化分级方法对大小不同的撞击坑进行定量分级和统计分析。本文在月表撞击坑数据库LU60645GT和Lunar_Impact_Crater_Database(2011)的基础上,结合数据库中撞击坑的直径、深度和年代信息,利用最优分割分级法对撞击坑直径进行定量化分级,并根据分级结果,综合分析撞击坑几何形态特征及其演化规律。研究结果表明,撞击坑形态特征的演化与年代有密切的关系。在相同级别、相同地体下,撞击坑形成的年代越早,其形态特征的精细结构退化程度越明显,只保留了大体的几何形状;而在不同级别、相同地体、相同年代下的撞击坑形态特征则由简单逐渐变为复杂,坑物质也逐渐变得复杂。 相似文献
9.
撞击坑是月表最典型的地质单元,其溅射物作为撞击坑的坑外组成部分可分布到距离坑中心10个直径距离之外的区域,因此撞击溅射物也是月球地质编图中最重要的表达要素之一。本文使用月球勘测轨道器(LRO)的激光高度计(LOLA)数据、广角相机(WAC)影像、窄角相机(NAC)影像以及Clementine的UVVIS多光谱数据,研究了哥白尼纪正面月海区直径31km的Kepler撞击坑和背面月陆区直径30km的Necho撞击坑。哥白尼纪撞击坑溅射沉积物可以分为三个相:连续溅射沉积相(CE)、不连续溅射沉积相(DE)和辐射纹(CR)。连续溅射沉积相分布在最大约2.6个半径范围之内,不连续溅射沉积相分布在最大近11个半径范围之内,辐射纹分布在最大近29个半径范围之内。本文强调了多源数据结合在识别撞击坑溅射沉积物中的作用,对Kepler坑和Necho坑溅射沉积物进行了填图,不对称分布的特征表明这两个坑可能形成于倾斜撞击。 相似文献
10.
应用中国首次月球探测工程所获得的嫦娥一号(Change-I)CCD影像数据、干涉成像光谱数据、数字高程模型(DEM)数据和数据分析处理结果等资料,开展了虹湾—雨海地区区域地质综合研究。通过对月球撞击坑及溅射堆积物分析,以及地层单元划分、构造单元划分、岩石类型划分、年代学和月球演化历史的集成分析,依据月坑的形态特征、充填物的多少和保留的程度等,将月球撞击坑划分出7种类型11个亚类,并将月球撞击坑堆积物系统划分为6种类型9个堆积岩组。根据TiO2的含量、分布及影像特征,将月海、月陆玄武岩划分为高钛玄武岩、中钛玄武岩和低钛玄武岩。应用ArcGIS地理信息系统,试点编制了1∶250万月球典型地区——虹湾幅(LQ-4)地质图,并建立了空间数据库,探索制定了月球数字地质图编制技术规范、流程和方法,为中国下一步应用嫦娥二号数据开展"全月球地质图"编制,以及未来其他天体的区域地质综合研究与地质编图工作奠定了基础。 相似文献
11.
Guboglo M. N. 《GeoJournal》1980,4(1):53-58
International unity is becoming ever stronger in this country owing to an increasing similarity in the development of the cultural environment. This comprises the provision of all the country's republics with a sufficient number of schools, theatres, and other institutions and cultural information media in accordance with the needs of the population. An important part is played by the rise in ‘the general educational level, as well as the level of professional qualifications and skills. Among all the Soviet nations and nationalities, this rise being more rapid among formerly backward peoples. Prominent among the factors of internationalization is the progressive development of the nationalities’ cultural resources, while professional culture is being increasingly brought within the reach of the masses.The implementation of the nationalities policy promotes the all-round development of all Soviet nations and nationalities, their drawing together, the upsurge of the individual capabilities of every Soviet citizen. 相似文献
12.
Jiayu Rong Michael Melchin S. Henry Williams Tatyana N. Koren Jacques Verniers 《《幕》》2008,31(3):315-318
The Global Stratotype Section and Point （GSSP） for the base of the Silurian System was defined in 1985. Since that time, a number of researchers have suggested that this section has serious deficiencies for use as a GSSP. As a result, in 2000, the Subcommission on Silurian Stratigraphy （SSS） proposed undertaking a formal restu@ of this GSSP, which was subsequently approved by the International Commission of Stratigraphy （ICS）. The result of this restudy was the formal proposal that the current GSSP, at 1.6 m above the base of the Birkhill Shale, at Dob＇s Linn, Scotland, should be maintained as the same locality and stratigraphic level, but the bios- tratigraphical definition of the boundary should be revised. The previously defined, basal Silurian grapto- lite zone, the Parakidograptus acuminatus Zone, should be subdivided into a lower Akidograptus ascensus Zone and a higher E acuminatus Zone. The base of the A. ascensus Zone, marked by the first appearance of A. ascensus, should be regarded as the biostratigraphic mark for the base of the Silurian. This proposal has now been formally approved by the SSS and ICS, and ratified by International Union of Geological Sciences. This is the first GSSP to undergo formal restudy and redefini- tion, and the proposal also included a recommended procedure for restudy of GSSPs. 相似文献
13.
Deviation of the major axis of the inertia ellipsoid of the Moon from the direction toward the Earth
B. P. Kondratyev 《Astronomy Reports》2017,61(8):709-714
It is known from observations that the center of mass of the Moon does not coincide with the geometric center of its figure, and the line connecting these two centers is not aligned with the direction toward the center of the Earth, instead deviating toward the Southeast. This stationary deviation of the axis of the inertia ellipsoid of the Moon to the South of the direction toward the Earth is analyzed. A system of five linear differential equations describing the physical libration of the Moon in latitude is considered, and these equations are derived using a new vector method taking into account perturbations from the Earth and partly from the Sun. The characteristic equation of this system is obtained, and all five oscillation frequencies are found. Special attention is paid to the fifth (zero) frequency, for which the solution of the latitude libration equations are stationary and represents a previously unknown additional motion of the rotational axis of theMoon in a cone with a small opening angle. In contrast to the astronomical precession of the Earth, the rotation of the angular-velocity vector is in the positive direction (counter-clockwise), with the period T 3 = 27.32 days. On this basis, this phenomenon has been named “quasi-precession.” This quasi-precession leads to a stationary inclination of the major axis of the inertia ellipsoid of theMoon to the South (for an observer on Earth), making it possible to explain one component of the observed deviation of the center of mass of the Moon from the direction toward the Earth. The opening angle of the quasiprecession cone is approximately 0.834″. 相似文献
14.
Important tendencies in development of the world mineral-resources sector at the beginning of the 21st century were an increase in production and consumption of mineral materials differentiated by types of metals and nonmetallic mineral raw materials, by countries and regions, as well as the concentration of the production of mineral raw materials in a small number of countries, and a reduction in industrial reserves of minerals in the world economy, even at the current stage of their extraction. These tendencies should be taken into account in working out a strategy for development of the Russian mineral raw-material base. 相似文献
15.
Fouad N. Ibrahim Dr. 《GeoJournal》1988,17(1):133-141
Taking the example of W Sudan, an analysis of the climatic incidents leading to the two recent famine disasters is made. On this natural background, the human side is investigated. Focus is directed towards the fragile economic structure of the famine-prone population groups. An early-warning system for famine in the Sahelian Zone is proposed taking grain production and storage, livestock development and the relationship between the prices of livestock and grain as major indicators. 相似文献
16.
东濮凹陷北部沙三中亚段广泛发育盐岩和烃源岩,这两个看似不能共存的物质却在这里互层共生。该时期研究区沉积特征为多盐韵律与多层烃源岩互层共生、连续沉积,单个盐韵律厚度从几米到十几米,烃源岩有机质丰度高、类型好。平面上,两者在湖盆沉积沉降中心共生;垂向上,高有机质丰度、好干酪根类型与高盐度地层具有较好的对应关系。因而成为恢复古气候和古环境的重要研究对象。通过岩石学、古生物学以及Sr/Ba、B/Ga、(V+Ni+Mn)、Fe/Mn、Sr/Cu、Mg/Ca、V/(V+Ni)、稀土元素含量和氯同位素等方法对凹陷北部沙三中亚段的沉积环境进行研究。结果表明,凹陷北部沙三中亚段为深水沉积的还原环境,古盐度较高,达到半咸水-咸水沉积;微量元素和孢粉化石特征表明研究区沙三中亚段为温暖潮湿的环境。 相似文献
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郯庐断裂南段研究进展与断裂性质讨论 总被引：13，自引：3，他引：13
据1：5万区域地质调查和专题研究资料，就郯庐断裂带是否南延与消失的原因，其与大别—苏鲁造山带交截形成的假位错效应，以及与中新生代沉积盆地形成演化的关系等作了新的阐述。在此基础上，讨论了郯庐断裂带是否为巨大的左行平移断层或转换断层。认为郯庐断裂带可能是在“古郯庐带”的基础上于早侏罗世重新活动、白垩纪强烈活动的地堑型枢纽断裂带。 相似文献
20.
The Importance of the Precipitation and the Susceptibility of the Slopes for the Triggering of Landslides Along the Roads 总被引：3，自引：1，他引：2
Clemente Irigaray Francisco Lamas Rachid El Hamdouni Tomás Fernández José Chacón 《Natural Hazards》2000,21(1):65-81
In order to characterise the influence of the heavyrains on the observed landslides during the 1996–1997hydrological cycle, rainfall records for the last 100years are analysed from 104 stations in easternAndalusia. Regarding the amounts of rain recordedbetween October 1996 and March 1997 in the 104stations studied, 31 presented new all-time records;15 presented values that were 80–100% of thepre-1995 record; 49 stations, 80–50%; and 9stations, < 50%. A map has been devised of thesusceptibility of the materials through which thesouth-eastern Andalusian road network crosses,together with an inventory of the damage caused byinstability phenomena on banks and cuttings of theroad network during the winter of 1996–1997. Therelationships between the rainfall during the studyperiod, the damage caused to the road network and thesusceptibility of the materials affected are analysed.The results indicate that there is a clearcorrespondence between the rainfall recorded and thesusceptibility of the materials with the inventorieddamage. It is concluded that the widespread seriousdamage caused in early 1997 to the roads andsurrounding areas in the Alpujarra region and thecoast of the Province of Granada was mainly caused bythe extraordinarily heavy rains. However, considerablyless damage was observed where the susceptibility ofthe terrain is low, thus highlighting the extremeusefulness of terrain-susceptibility maps for riskprevention and territorial planning. 相似文献