南华北盆地青白口系—侏罗系层序界面时空分布特征研究

以位于秦岭—大别造山带之北、华北陆块南部、地跨华北陆块稳定块体、陆块南部边缘变形带的南华北盆地为研究对象,通过对研究区42条不同时代的野外剖面详细观测,运用层序地层学理论,把南华北盆地作为一个整体系统,对青白口系—侏罗系层序界面特征及时空分布规律进行了系统分析,共识别出了8种类型层序界面的物质表现形式,分别是不整合面、渣状层、古喀斯特作用面、冲刷侵蚀面、超覆面、岩性岩相转换面、最大海泛面、最大湖泛面。并重点讨论了各类型界面的时空分布特征。结果表明：在时间演化上,从早到晚由海相—海陆过渡相—陆相,层序界面经历了海相沉积不整合、古喀斯特作用面、渣状层到陆相不整合面、冲刷侵蚀面等;在空间上,同一层序界面在不同相带表现形式不同,同一种类型的界面可在不同相带出现,但不同相带表现特征有一定差异性。     

鲁西北西向断裂系与沂沭断裂带晚中生代演化关系及其动力学背景探讨

晚中生代是华北地块构造演化的转折时期。由出露于沂沭断裂带、鲁西地体、鲁东地体的中生代地层、岩浆,结合断裂活动年代学、区域地质等资料分析,可以将沂沭断裂带晚中生代构造演化划分出距今约160Ma、130～110Ma、90～80Ma等3个关键时期,并分别与左行压剪、左行张剪、右行压剪构造活动相对应。晚中生代沂沭断裂带与鲁西北西向断裂系间的几何学、运动学、年代学的共轭匹配关系表明,它们为特定构造动力学背景下形成的一组共轭断裂系。同时对鲁东地体晚中生代构造演化、鲁东北西向断裂系特征,以及沂沭断裂带、北西向断裂系晚中生代构造演化的动力学背景进行探讨。     

桐柏碰撞造山带及其邻区变形特征与构造格局

桐柏碰撞造山带及其邻区可以划分为九个大地构造单元,自北向南分别是:华北克拉通南缘岩石构造单元——宽坪岩群、具弧后盆地性质的二郎坪岩石构造单元、具岛弧性质的秦岭杂岩单元、龟山岩组和南湾岩组构成的俯冲前缘楔构造带、构造混杂岩带、桐柏北部高压岩片单元、桐柏核部杂岩单元、桐柏南部高压岩片单元以及随州构造变形带。根据详细的构造解析以及新的地质年代学资料,本文将中生代以来的构造变形划分为五幕,前两幕变形主要发育在构造混杂岩带以南的各个岩石构造单元中,之后的三幕变形则波及整个研究区。第一幕变形的时间约为255～238Ma,以发育区域上透入性的片理及北西西向的拉伸线理为主,并导致了高压岩片早期自西向东的挤出。第二幕变形的时间约为230～215Ma,以自北向南的逆冲推覆构造为主,使得高压岩片进一步垂向抬升。第三幕变形应早于下侏罗统,以近北西西向的宽缓褶皱为主要特征,该幕变形期间桐柏核部杂岩及其两侧高压岩片单元发生同步的抬升。第四幕变形大致发生在140～130Ma之间,主要表现为桐柏核部杂岩两侧走滑型韧性剪切带的活动,桐柏核部杂岩表现出向东的挤出。第五幕变形发生在120～80Ma,表现为北西向及北东向的脆性断裂活动,并切割以上所有构造形迹。桐柏高压岩片的抬升剥露受多幕变形控制,呈阶段性的抬升。     

华北及其以北地区晚古生代—早中生代构造格架主体特点

从全球尺度对原大西洋与古亚洲洋构造域大地构造旋回及其演化特征进行对比研究,有助于了解巨型构造域内的区域构造演化的关联性。建立古大陆构造单元属性"动态行为"的理念,将复合造山区与毗邻大地构造单元进行关联分析,揭示出华北前陆盆地的形成发展与毗邻复合造山区的构造演化进程密切相关。华北及其以北地区晚古生代—早中生代构造格架的主体特点是:1)蒙古—兴安复合造山区发育石炭纪—二叠纪陆表海盆地、裂陷槽和上叠盆地,及三叠纪的山间盆地;2)华北前陆盆地与复合造山区构造演化进程同步,在古陆上形成石炭纪海相和海陆交互相沉积,二叠纪—中三叠世的陆相沉积,以发育红层和局部形成膏盐为特点;3)原华北古陆北缘"构造岩浆活化带"属晚古生代—早中生代蒙古—兴安复合造山区最南端的构造单元,具有构造前锋带属性。     

华北克拉通中生代以来基性岩墙群的分布及研究意义

围绕岩石圈破坏和减薄这个主题,华北克拉通成为近10年来国内外研究的热点地区。华北克拉通中生代以来基性岩墙群分布广泛,然而对此仍缺乏系统的研究。通过对基性岩墙群的系统总结,在详尽的资料收集和已有研究的基础上,重点对华北克拉通中生代基性岩墙群的研究现状、分布和意义进行了汇总和讨论。随后,结合近年来的研究经验,提出了基性岩墙群定年中应注意的问题。     

中国晚侏罗世多瘤齿兽类哺乳动物的发现及其意义

多瘤齿兽是一类已绝灭的哺乳动物,其以后部牙齿上有很多小瘤(小的隆起,或者小尖)来适于咀嚼植物为特征。总的来说,它们的门齿和臼齿与那些啮齿类相似,但在演化时间上多瘤齿兽比新生代的啮齿类早的多。多瘤齿兽是杂食者,或者说是成功开拓了其它脊椎动物无法开拓的植食生境的植食者(可以树叶、种子、蕨类、裸子植物,再加上蠕虫和昆虫为食)。由于它们多种食性和运动方式,多瘤齿兽成为中生代数量最多的哺乳动物,几乎占侏罗纪和白垩纪时期所有哺乳动物种类的一半。它们的支系是哺乳动物历史上生存时间最长的支系,出现于170 Ma前,大约绝灭于35 Ma。但是,因为多瘤齿兽具有很多独特的、高度特化的牙齿和头骨特征,古生物学家们长期困惑于它们的进化起源。最近,中国辽西发现了一件产自晚侏罗世髫髻山组的多瘤齿兽类哺乳动物。由于其牙齿上发育明显的纹饰,如很多小的脊、沟、凹槽等,新发现的哺乳动物被命名为皱纹齿兽(Rugosodon)。另一方面,由于与皱纹齿兽亲缘关系最近的哺乳动物产自西欧的侏罗纪地层,因此其种名被命名为欧亚皱纹齿兽(Rugosodon eurasiaticus)。新发现为晚侏罗世时期欧洲和亚洲的哺乳动物具有高度的相似性提供了最新的证据。皱纹齿兽是一种夜行的哺乳动物,生活于气候温和的湖滨,与长羽毛的恐龙近鸟龙、翼龙类达尔文翼龙、大量节肢动物、其它几种哺乳动物共同生活于一起。根据与现生哺乳动物的比较,并依据欧亚皱纹齿兽手部比例、末端指节的形态等,推论欧亚皱纹齿兽很可能是地栖哺乳动物,或者说地栖比攀爬的可能性更大。这一发现对于研究多瘤齿兽早期的演化、食性分异、运动适应起源等具有重要的科学意义。     

论扬子板块东北缘的俯冲与回撤对山东地块的影响

通过对山东中生代侵入岩体的时空展布、岩石化学及同位素特征的综合分析研究,提出了扬子板块东北缘俯冲与回撤的演化机制,分析了在这种机制下的成岩、成矿演化规律。认为扬子板块东北缘的俯冲与回撤控制了山东中生代的地质演化过程,其回撤在岩石圈深部造成的真空,导致软流圈物质的隆升,是胶东金矿大规模成矿作用的内在控制因素。     

The late Mesozoic–Cenozoic tectonic evolution of the South China Sea: A petrologic perspective

This paper presents a review of available petrological, geochonological and geochemical data for late Mesozoic to Recent igneous rocks in the South China Sea (SCS) and adjacent regions and a discussion of their petrogeneses and tectonic implications. The integration of these data with available geophysical and other geologic information led to the following tectono-magmatic model for the evolution of the SCS region. The geochemical characteristics of late Mesozoic granitic rocks in the Pearl River Mouth Basin (PRMB), micro-blocks in the SCS, the offshore continental shelf and Dalat zone in southern Vietnam, and the Schwaner Mountains in West Kalimantan, Borneo indicate that these are mainly I-type granites plus a small amount of S-type granites in the PRMB. These granitoids were formed in a continental arc tectonic setting, consistent with the ideas proposed by Holloway (1982) and Taylor and Hayes, 1980, Taylor and Hayes, 1983, that there existed an Andean-type volcanic arc during later Mesozoic era in the SCS region. The geochonological and geochemical characteristics of the volcanics indicate an early period of bimodal volcanism (60–43 Ma or 32 Ma) at the northern margin of the SCS, followed by a period of relatively passive style volcanism during Cenozoic seafloor spreading (37 or 30–16 Ma) within the SCS, and post-spreading volcanism (tholeiitic series at 17–8 Ma, followed by alkali series from 8 Ma to present) in the entire SCS region. The geodynamic setting of the earlier volcanics was an extensional regime, which resulted from the collision between India and Eurasian plates since the earliest Cenozoic, and that of the post-spreading volcanics may be related to mantle plume magmatism in Hainan Island. In addition, the nascent Hainan plume may have played a significant role in the extension along the northern margin and seafloor spreading in the SCS.     

济阳坳陷桩海地区中生界同位素年代地层学研究

济阳坳陷中生界分布广泛,具有油气成藏的基本地质条件,并取得了一定的勘探发现,但其勘探程度和研究程度相对较低,包括地层划分、沉积体系、储层特征、控藏因素等。特别是地层时代、分层与分界等基本的地质问题尚存在不同的观点和认识。根据区内14口井的10个火山岩全岩样品和79个小于2μm的泥岩自生伊利石样品,开展K-Ar法同位素年代地层学测定,分别确定了中生界的坊子组、蒙阴组、三台组和西洼组的绝对年龄值,将坊子组划归下侏罗统,蒙阴组为中侏罗统,缺失上侏罗统,并明确了各组的接触关系。     

Archean to Recent aeolian sand systems and their sedimentary record: Current understanding and future prospects

The sedimentary record of aeolian sand systems extends from the Archean to the Quaternary, yet current understanding of aeolian sedimentary processes and product remains limited. Most preserved aeolian successions represent inland sand‐sea or dunefield (erg) deposits, whereas coastal systems are primarily known from the Cenozoic. The complexity of aeolian sedimentary processes and facies variability are under‐represented and excessively simplified in current facies models, which are not sufficiently refined to reliably account for the complexity inherent in bedform morphology and migratory behaviour, and therefore cannot be used to consistently account for and predict the nature of the preserved sedimentary record in terms of formative processes. Archean and Neoproterozoic aeolian successions remain poorly constrained. Palaeozoic ergs developed and accumulated in relation to the palaeogeographical location of land masses and desert belts. During the Triassic, widespread desert conditions prevailed across much of Europe. During the Jurassic, extensive ergs developed in North America and gave rise to anomalously thick aeolian successions. Cretaceous aeolian successions are widespread in South America, Africa, Asia, and locally in Europe (Spain) and the USA. Several Eocene to Pliocene successions represent the direct precursors to the present‐day systems. Quaternary systems include major sand seas (ergs) in low‐lattitude and mid‐latitude arid regions, Pleistocene carbonate and Holocene–Modern siliciclastic coastal systems. The sedimentary record of most modern aeolian systems remains largely unknown. The majority of palaeoenvironmental reconstructions of aeolian systems envisage transverse dunes, whereas successions representing linear and star dunes remain under‐recognized. Research questions that remain to be answered include: (i) what factors control the preservation potential of different types of aeolian bedforms and what are the characteristics of the deposits of different bedform types that can be used for effective reconstruction of original bedform morphology; (ii) what specific set of controlling conditions allow for sustained bedform climb versus episodic sequence accumulation and preservation; (iii) can sophisticated four‐dimensional models be developed for complex patterns of spatial and temporal transition between different mechanisms of accumulation and preservation; and (iv) is it reasonable to assume that the deposits of preserved aeolian successions necessarily represent an unbiased record of the conditions that prevailed during episodes of Earth history when large‐scale aeolian systems were active, or has the evidence to support the existence of other major desert basins been lost for many periods throughout Earth history?