华北晚侏罗世风成沉积组合及古气候和古地理意义

Eolian depositional associations is a combination of eolian dune and fluvial-arid lake sedimentary deposition, which is mainly controlled by the coefficient arid-moisture climate cycles,the continuing subsiding of basin basement and ancient water table, therefore, eolian depositional associations recorded the information of ancient climate, extensional basin development and palaeogeographic settings. Furthermore, a combination of sources and sinks of eolian deposition system also indicates the paleogeography of regional basin and its provenance tectonic background.As early as the mid-Mesozoic international eolian depositional associations is mainly distributed in the America and Africa of the western hemisphere. However, in China, eolian deposits mainly formed during the Cretaceous. In recent years, the possible oldest and most typical aeolian deposits of the Late Jurassic,in northern Shanxi Province and western Shandong Province of China, so far were dicovered, which creates great opportunitie for a further study of the Jurassic paleoclimate, paleogeography, basin evolution and tectonic backgrounds in North China.This proposal will foucus on the Late Jurassic eolian depositional associations of North China, combined with the application of wind-water sedimentary cycle sequence, climate-sensitive rocks, mineral deposits, facies markers and multivariate geochemical index, to study Late-Jurassic arid-moisture paleoclimate replacement cycles. Furthermore, Through a comprehensive analysis of aeolian depositional associations’ source and sink system, combining paleocurrents and paleowind directions, debris components and multivariate analysis of isotopic geochronology of source tracing, to explore the Late Jurassic basin-mountain paleogeography and stretch or compressed paleotectonic setting in North China.

风成沉积组合系风成砂与河流-干旱湖泊沉积物的沉积组合，它们受控于干-湿气候旋回及盆地基底与古潜水面持续沉降的共同作用，因此，风成沉积组合记录了古气候、盆地发育与古地理背景信息，通过风成沉积组合源汇体系的分析也能揭示区域盆山古地理格局及物源区构造属性。国际上中生代早中期的风成沉积组合主要发育在西半球美洲和非洲，我国则主要发育白垩纪以来的风成沉积物。申请者近年在华北晋北和鲁西发现我国迄今最古老、最典型的晚侏罗世风成沉积组合，其为研究华北侏罗纪古气候、古地理以及盆地演化和构造背景创造了新契机和新途径。申请项目将以此华北晚侏罗世风成沉积组合为切入点，应用风-水沉积旋回序列，气候敏感类岩石、矿物和沉积标志与多元地球化学指标反演晚侏罗世干-湿古气候旋回更替规律；通过风成沉积组合源汇体系分析，结合古流和风向、碎屑组分及多元分析同位素年代学源区示踪，探讨华北晚侏罗世盆山古地理格局及伸展亦或挤压古构造背景。

全球变化和气候变暖是当代的主题和科学前沿，特别是全球气候变化更是与地球表层水圈和大气圈相互作用有关，直接关联着以行星风系为特征的古气候背景以及全球性的或区域性尺度的地球极端干旱或荒漠化事件，基于中生代地质历史时期风成沉积记录就可以反演深时期的全球或区域性大气环流环境，也是地球宜居性研究的核心内容。本项目重点聚焦华北晚侏罗世风成沉积，研究风-水沉积旋回序列，气候敏感类岩石、矿物和沉积标志与多元地球化学指标反演晚侏罗世干-湿古气候旋回更替规律。同时通过风成沉积组合源汇体系分析，结合古流和风向、碎屑组分及多元分析同位素年代学源区示踪，探讨华北晚侏罗世盆山古地理格局及伸展亦或挤压古构造背景。项目又拓展研究了华北三叠纪和整个华北地区早白垩世风成沉积和古气候环境。研究证实，1）中生代时期全球陆地环境普遍发育极端干旱导致的荒漠化或风成沉积物/风成砂沉积记录；2）中国北方侏罗纪时期由早至晚发生潮湿-干热古地理环境的演替及其古地磁数据表明，东亚地区存在从高纬度温暖湿润成煤气候带向低纬度赤道方向干旱炎热和风成气候带的块体移动；3）华北普遍发育晚侏罗世风成砂沉积符合和验证了侏罗纪大干旱事件的推断，它们可能影响着晚中生代陆地生物群的演替；4）华北北缘J/K过渡期也发育区域性的陆相红层和风成岩系与陆相动植物群，大规模基性岩脉或岩墙群揭示了同时期地壳伸展背景；5)华北范围白垩系普遍发育巨厚风成沉积，可能代表侏罗纪大干旱事件的持续演化的沉积响应，但它们究竟是同期地球真极移也或大气环流演变的动力驱动机制还需进一步研究讨论。本研究国内外期刊发表SCI检索12篇，中文核心4篇，多次参加国内外学术会议交流，培养研究生和博士后若干名。同时首次发现鄂尔多斯洛河组风成砂型含铀岩系新类型，暗示了中国华北侏罗系-白垩系风成沙漠沉积批量含铀的可能性，其对于铀矿的找矿意义是巨大，为下步深地铀矿勘探指明方向。