四川武隆地区二叠—三叠系磁性地层学研究

四川武隆地区的p/T界线为一化石丰富、沉积连续的海相碳酸盐剖面。通过对岩石磁学的研究,鉴别出三叠系灰岩样品以磁铁矿为主,其中约70％为多畴磁铁矿。ChRM由单畴磁铁矿所携带。二叠系灰岩样品主要为单畴与超顺磁颗粒的磁铁矿,样品不同程度地遭受重磁化。然而,根据其退磁中NRM矢量变化的轨迹与极性有关,使确定绝大部分样品的极性成为可能。本文通过与国外剖面的对比,认为Illawarra反转起始于吴家坪阶上部,而Kiaman极性段中则存在着若干正向极性。     

HUANAN ALPS, NOT SOUTH CHINA PLATFORM

The notion that South China was a post-Caledonian platform is clearly proven incorrect by the ev-idence of Mesozoic deformation and igneous activities. Reinterpretation of map patterns suggested the pres-ence of Mesozoic orogenic belt comparable to Southern Appalachians in dimension and in style of de-formation. Field work in 1985 led to the discovery of possible flysch and rigid basement nappes, whichhave been thrust onto carbonate platform. A suture zone has been identified. The Huanan Alps owed itsorigin to Indosinian Orogeny, which eliminated a Paleo Tethyan Seaway, the Xiangganzhe (Hunan-Ji-angxi-Zhejiang) Ocean between the Yangtze and Huanan Terranes.     

皖南变质岩中古生物化石及其大地构造意义

安徽省南部浅变质岩区以往称作元古宙上溪群并与板溪群对比,它的分布区被称作“江南古陆”。最近先后在这个地区的变质岩中找到古生代的疑源类化石Baltisphaeridium sp。以及腕足类Lingulacea fam. et gen indent.,同时在其北缘原划归震旦纪的地层中找到石炭纪的具环三缝孢为主的孢粉组合和锥石类(?)Conulariid(?)等,证明本区变质岩的相当一部分为古生代地层。同时也说明这里的构造格局和演化过程与以往所说很不相同。     

是华南造山带而不是华南地台

华南是一个加里东期后地台的观念,已为中生代变形作用和火成活动的证据证明显然是错误的。地质图图型的重新解释指出了存在一个规模和交形样式均可与阿巴拉契亚南部相类比的中生代造山带。1985年的野外工作使我们发现了已经冲断到碳酸盐台地之上的可能的复理石和刚性基底。已经鉴定出一条缝合带。华南造山带是印支造山运动生成的,这次造山运动导致了杨子地体和华南地体之间的湘赣浙洋盆这个古特提斯海路的消失。     

Permo-Triassic Magnetostratigraphy in Wulong Area, Sichuan, China

The Permo-Triassic boundary in Wulong area, Sichuan Province, South China lies in a continuous marine carbonate succession with abundant fossil records. Two well-exposed sections were sampled for magnetostratigraphic studies. The experimental results of rock magnetism reveal that the samples from the Triassic limestones contain only magnetites among which 70% are multi-domain. The ChRM direction is carried by remaining 30% of single-domain magnetite. The Permian limestone samples are dominated by single-domain to superparamagnetic magnetites with little ChRM direction due to their fine-grained texture. Nevertheless, the polarity determination is still possible based on the NRM vector changes during thermal demagnetization. A Permo-Triassic polarity profile in Wulong area is established in the paper, and a tentative correlation with other known profiles is pursued. The authors suggest that the Illawarra reversal starts at the upper part of Wujiapingian, while some normal polarity events may exist in the     

The Fossils in Shangxi Group and Its Implication for Tectonics, Southern Anhui, China

The Shangxi Group is the local name in southern Anhui Province and it is believed to be the equivalence of the well-known Banxi Group in Hunan Province, southern China. So the area occupied by the Shangxi Group was regarded as a part of the "Jiangnan old land" of Presinian till it was challenged by the present authors years ago. After we postulated that there may be some strata of Palaeozoic Era in Shangxi Group, some microfossils and then macrofossils of Palaeozoic were found in some part of it. The macrof os-sils, Lingula sp. , Conulariid and the microfossils indicate that most units of the Shangxi Group are Palaeozoic strata. Based on the discovery of these fossils and the recognition of the tectonic-setting of the different tectono-petrologic units in the Shangxi Group, three different stratigraphic sequences (island-arc volcanics, back-arc sediments and the cover of passive margin of Yangtze Continental Plate) are established and the tectonic evolution of them is postulated in the present paper. Al