造山带隆起剥蚀过程与沉积记录

大别山造山带是中生代碰撞造山作用的产物，其隆起过程中形成了合肥盆地。本文对合肥盆地侏罗系碎屑岩进行了成分分析，发现砾岩中有两类榴辉岩，一类为高压变质榴辉岩，另一类为超高压变质榴辉岩。对砂岩中碎屑白云母的成分分析表明，指示高压变质作用的多硅白云母在较低层位已大量出现。重建的碎屑物注入顺序为：非超高压变质岩一高压变质岩一超高压变质岩。结合变质岩石学研究和地球物理观测资料重建的大别山造山带内部结构，可进一步重建大别山的剥蚀历史：大别山造山带最先（三尖铺组沉积初期）受到剥蚀的是非超高压变质的片岩、片麻岩及大理岩，高压变质岩折返到地表受到剥蚀不晚于中侏罗世初期（三尖铺组沉积早期），而超高压变质岩折返到地表经受剥蚀的时问稍早于中侏罗世中期（凤凰台组沉积初期）。天山是典型的陆内造山带，其隆起是新生代以来印度板块与欧亚板块碰撞的一种远程效应。本文对天山发育的花岗岩磷灰石裂变径迹分析，并对南侧的塔里木盆地北部古近系及新近系沉积岩进行了碎屑岩物源分析，在新的磁性地层学格架中讨论了天山的隆起剥蚀历史。砾石组分的突然变化发生在75-35Ma，26-17Ma和12-8Ma间，从中天山物源区逐渐变为南天山物源区，12Ma后变为以南天山为主要物源区。砂岩及重矿物组分变化表明，物源在124Ma、26（-24）Ma及15（-12）Ma时发生过变化。磷灰石裂变径迹则进一步揭示了天山的3阶段差异性隆起历史：天山的早期隆起发生在124-80Ma间，从中天山和南天山的交界处开始并向南扩展；第二次隆起发生在大约100-60Ma间，从中天山开始向南扩展；第三次隆起从大约50Ma开始，并向北南两侧扩展，至大约30Ma时扩展到北天山，约20Ma时扩展至南天山；其后，南天山在15（-12）Ma时发生了独立的隆起事件。本文的两个研究实例表明，盆地的充填符合计算机数据结构的堆栈过程，但造山带的隆起剥蚀却会出现明显的差异性。不能简单地说造山带的剥蚀和盆地的充填具镜像对称关系，这有可能导致错误的认识，一定要具体事例具体分析。

盆地动力学研究综述及展望

沉积盆地是地球系统的浅层组成部分,是壳-幔、岩石圈-软流圈两级圈层相互作用的浅部表现形式。沉积盆地分析不仅可以揭示不同类型化石能源、沉积型层控矿产、砂岩型铀矿等资源的分布规律,为矿产勘探提供直接依据,而且可以为大地构造演化过程、重大构造事件、全球环境变迁及气候演变提供丰富资料和详细证据。当代盆地分析不断从单一沉积学分析拓展到综合分析,从静态要素分析拓展到过程和动力机制分析。盆地动力学研究内容包括3部分,即以沉积学分析为主的盆地充填动力学、以构造地质学分析为主的盆地形成演化动力学和多学科交叉的盆地流体动力学研究。近10多年来,盆地动力学研究在深水沉积学、高精度层序地层学、源-汇系统、源区剥蚀过程及其深部响应、大陆边缘盆地动力学及盆地流体动力学等方面取得了长足的进展。

Sedimentary filling and sequence structure dominated by T-R cycles of the Nenjiang Formation in the Songliao Basin

The Nenjiang Formation in the Songliao Basin is a symmetrical sequence of progradation-retrogradation,and is formed in the transgression cycle and regression cycle(T-R cycles)of the base level of deposition.We analyzed the drilling,well logging,core data,and seismic profiles of basin level,and by using the sequence stratigraphy,identified one secondary sequence boundary,two third-order sequence boundaries,and eight fourth-order sequence boundaries in the Nenjiang Formation.These eleven sequence boundaries can be divided into structural unconformity,depositional unconformity,flooding surface,and forced regression surface.Therefore the Nenjiang Formation can be subdivided into one secondary sequence,three third-order sequences,and ten fourth-order sequences.We have restored the sedimentary filling evolution within the stratigraphic framework of fourth-order sequences in the Nenjiang Formation.The sedimentary period of the first member of the Nenjiang Formation was corresponded to the global transgression period,which is also the development period of transgression cycle(T cycle),when the lake basin had the largest scope and deepest sedimentary water,the SB07(the maximum flooding surface)was formed on the top of strata during this period;covering above the SB07,there developed a set of condensation layer-oil shale,which is distributed in the whole basin and is the important source bed and regional cover.Therefore,a retrogradation sequence was formed in the T cycle of the first member of the Nenjiang Formation,characterized by the retrograding delta at a low angle.The delta has a giant front,a small plain,and many underwater distributary channels.Meanwhile,large gravity flow channels and sublacustrine fans are developed in the front of the delta.During the depositional period of the second member of the Nenjiang Formation,the R cycle began to develop due to the compression of the pacific tectonic domain;the source direction rotated 90°along with the eastern uplifting of the basin,and formed a series of east-west prograded and forced retrogradations.The prograding delta at high angel was developed in the interior of the sequence;the delta had a small front,a giant plain,and fewer underwater distributary channels,with the collapse at the foreslope,forming a series of slump fans.The slump fans can be divided into three types:discrete type,superimposed type,and fluid type.We built a whole"triad model"of the slump fan.Pointed out that the sequence of forced retrogradation formed by R cycle is a good structural mark of basin optimization,and rejected the viewpoint of"transgression"in the Nenjiang Formation of the Songliao Basin.

Sedimentary fill history of the Huicheng Basin in the West Qinling Mountains and associated constraints on Mesozoic intracontinental tectonic evolution

The Qinling Orogenic Belt is divided commonly by the Fengxian-Taibai strike-slip shear zone and the Huicheng Basin into the East and West Qinling mountains, which show significant geological differences after the Indosinian orogeny. The Fengxian-Taibai fault zone and the Meso-Cenozoic Huicheng Basin, situated at the boundary of the East and West Qinling, provide a natural laboratory for tectonic analysis and sedimentological study of intracontinental tectonic evolution of the Qin- ling Orogenic Belt. In order to explain the dynamic development of the Huicheng Basin and elucidate its post-orogenic tecton- ic evolution at the junction of the East and West Qinling, we studied the geometry and kinematics of fault zones between the blocks of West Qinling, as well as the sedimentary fill history of the Huicheng Basin. First, we found that after the collisional orogeny in the Late Triassic, post-orogenic extensional collapse occurred in the Early and Middle Jurassic within the Qinling Orogenic Belt, resulting in a series of rift basins. Second, in the Late Jurassic and Early Cretaceous, a NE-SW compressive stress field caused large-scale sinistral strike-slip faults in the Qinling Orogenic Belt, causing intracontinental escape tectonics at the junction of the East and West Qinling, including eastward finite escape of the East Qinling micro-plate and southwest lateral escape of the Bikou Terrane. Meanwhile, the strike-slip-related Early Cretaceous sedimentary basin was formed with a fight-order echelon arrangement in sinistral shear zones along the southern margin of the Huicheng fault. Overall during the Mesozoic, the Huicheng Basin and surrounding areas experienced four tectonic evolutionary stages, including extensional rift basin development in the Early and Middle Jurassic, intense compressive uplift in the Late Jurassic, formation of a strike-slip extensional basin in the Early Cretaceous, and compressive uplift in the Late Cretaceous.