COLLABORATIVE RESEARCH: Mesozoic Nonmarine Sedimentary Record of Transition from Contractile to Extensional Deformation, Southern Mongolia

小行星9708207 蒙古南部中生代的构造演化包括一个鲜为人知的从收缩到伸展构造作用的转变和相关的沉积盆地的发展。 只有在其最广泛的轮廓，这种转变变得明显，近年来，作为一个主要的北向早中生代褶皱冲断带在邻近的中国中北部，在蒙古南部同构造粗粒地层的勘察描述，以及有限的地球物理和地质文件晚中生代裂谷盆地在蒙古南部的认可。 与构造转换相关的构造和沉积体系的运动学、速率和样式的主要方面仍未得到解决，并形成了本研究建议的基础。 从这些问题中衍生出一系列令人兴奋的问题：在非均匀地壳上形成的沉积盆地系统如何响应构造变形样式的根本变化？ 是否出现了以前未认识到的盆地类型，就像最近在中国西部的碰撞前陆盆地中所记录的那样？ 变质核杂岩在从收缩构造向伸展构造的转变中发挥了什么作用？变质核杂岩在中国中北部的边界上被记录下来，在拟议的油田地区与类似的结构（尽管没有记录）在结构上是连续的。 这些问题只是这项建议要解决的许多问题中的几个问题。 具体而言，该提案寻求三年的资金，以调查和记录从中生代早期挤压构造到中生代晚期伸展构造作用的快速和根本性转变的沉积反应。 在回答上述每个问题时，我们建议首先记录收缩和伸展系统的基本地质学，以填补目前在蒙古南部中生代地质认识中存在的巨大空白。 我们建议采用的主要调查工具和手段包括综合的构造和沉积地质方法，其中构造数据和详细绘图将作为详细沉积体系和地层结构分析、物源分析和勘测热年代学研究的背景。 重要的是，地下数据将被纳入调查，这要归功于从目前正在开发的一个小油田获得重要的核心材料。 在完成了对每个构造体系及其沉积记录的基本记录之后，就可以解决上面提出的重要的更广泛的科学问题。 除了其科学重要性，拟议的研究将使美国机构和蒙古科学院之间的持续科学交流成为可能。 该提案的一个重要的额外教育层面在于支持一名博士后研究助理，一名博士。学生，两个硕士。学生

9708207 Graham The Mesozoic tectonic evolution of southern Mongolia includes a poorly understood transition from contractile to extensional tectonism and associated sedimentary basin development. Only in its broadest outline has this transition become apparent in recent years, as a consequence of recognition of a major north-verging early Mesozoic fold-thrust belt in adjacent north-central China, reconnaissance description of syn-tectonic coarse-grained strata in southern Mongolia, and limited geophysical and geological documentation of late Mesozoic rift basins in southern Mongolia. Major aspects of the kinematics, rates, and styles of structural and sedimentary systems associated with the tectonic transition remain unresolved, and form the basis for this research proposal. From such issues stem a suite of exciting questions: How do sedimentary basin systems formed atop heterogeneous crust respond to fundamental changes in tectonic deformational style? Do previously unrecognized basin types occur, as recently documented for collisional foreland basins formed atop accreted terranes in western China? What role to metamorphic core complexes, documented across the border in north-central China and apparently structurally continuous with similar though undocumented structures in the proposed field area, play in the transition from a contractile to extensional tectonics? These questions are but several among many to be addressed by this proposal. Specifically, this proposal seeks three years of funding to investigate and document the sedimentary response to a rapid and fundamental transition from compressional tectonics of early Mesozoic age to extensional tectonism of late Mesozoic age. In answering each of the above questions, we propose first to document the fundamental geology of the contractile and extensional systems to fill the very large gaps which exist presently in the geologic understanding of Mesozoic southern Mongolia. The principal tools and means of investigation we propose to employ involve an integrated structural and sedimentary geologic approach in which structural data and detailed mapping will serve as backdrop for detailed depositional systems and stratigraphic architectural analysis, provenance analysis, and reconnaissance thermochronologic studies. Importantly, subsurface data will be incorporated into the investigation, thanks to access to vital core material from a small oil field currently in development. After fundamental documentation of each tectonic system and its sedimentary record has been completed, the important broader scientific questions posed above can be addressed. Beyond its scientific importance, the proposed research will enable continued scientific exchange between U.S. institutions and the Mongolian Academy of Sciences. An important additional educational dimension of the proposal lies in its support for one Post-doctoral Research Associate, one Ph.D. student, and two M.S. students.