桂林泥盆纪碳酸盐台地礁组合的层序地层研究

桂林的泥盆系以发育碳酸盐台地和礁组合沉积为特征，岩相多样，地层对比和时代确定的难度较大。本文应用层序地层学原理，结合生物地层和岩石地层特征，研究桂林泥盆系露头的相结构及碳酸盐台地礁组合不同亚相的９个剖面中的不整合界面，识别出该区中、晚泥盆世地层的５个层序界面：（１）牙形刺下ｖａｒｃｕｓ亚带和中ｖａｒｃｕｓ亚带之间；（２）牙形刺ｈｅｒｍｍａｎｉ－ｃｒｉｓｔａｔｕｓ带和ｄｉｓｐａｒｉｌｉｓ带之间；（３）牙形刺下ｒｈｅｎａｎｅ亚带和上ｒｈｅｎａｎｅ亚带之间；（４）牙形刺ｅｘｐａｎｓａ带内部；（５）牙形刺ｐｒａｅｓｕｌｃａｔａ带和ｓｕｌｃａｔａ带之间。这些层序界面在岩石学上的特征为具有生物铸模溶孔的白云岩和不同规模的暴露溶蚀面。比较明显的大的海泛面有２次：（１）牙形刺ｅｎｓｅｎｓｉｓ带和ｖａｒｃｕｓ带之间；（２）牙形刺ｌｉｎｇｕｉｆｏｒｍｉｓ带和下ｔｒｉａｎｇｕｌａｒｉｓ亚带之间。     

滇黔泥盆纪露头层序地层的初步研究

通过露头层序地层学研究,滇黔泥盆系中可识别出三个Ⅰ类和二个Ⅱ类层序界面,以及三个Ⅰ类和一个Ⅱ类层序:洛霍柯夫—布拉克期为碎屑岩Ⅰ类层序,由低水位、海侵和高水位三个体系域构成层序;爱姆新—爱菲尔期为碎屑岩—碳酸盐岩Ⅱ类层序,由陆棚边缘、海侵和高水位三个体系域构成层序;吉维特早期和吉维特晚期—法门期为两个相似的碳酸盐岩为主的Ⅰ类层序,都由低水位、海侵和高水位三个体系域构成层序。由沉积体系域演化作出的泥盆纪海平面变化曲线,不同于威尔的全球泥盆纪海平面变化Ⅱ级旋回,表明滇黔地区泥盆纪海水进退和上升、下降受局部构造控制。     

西藏北部拉竹龙地区泥盆纪岩石地层单位划分与时代讨论

在详细描述西藏北部拉竹龙地区泥盆纪地层剖面的基础上,根据在前人所划的奥陶系兽形湖组中采集到的大量属于泥盆纪的腕足类化石,修订了兽形湖组的定义,从而将区内泥盆纪地层划分为兽形湖组、拉竹龙组,并根据生物化石资料讨论了各组的时代。     

Devonian to Triassic Successions of the Changning-Menglian Belt, Western Yunnan, China

Phanerozoic strata are distributed in several north-south trending zones in the central part of the Changning-Menglian Belt. Four types of Devonian to Triassic stratigraphic successions can be identified: (1) elastics with limestone lenses in the mid-section, changing up-section into alternations of fine elastics and cherts; (2) elastics with chert intercalations and limestone lenses, and topped by Permian basic volcanics; (3) elastics-basic volcanics-carbonates-clastics; and (4) limestones, dolomitic limestones-dark gray thin-bedded limestones, argillaceous limestones, mudstones and siliceous mudstones. Devonian to Triassic cherts occur in different horizons and different zones from east to west. These cherts are usually transitional to their neighboring elastics. There is no continuous Devonian to Middle Triassic chert sequence in the central zone of the Changning-Menglian Belt as Liu et al. (1991,1993) reported. Volcanics and the overlying carbonates described by some workers as "seamount" sequences     

海南岛抱板群内顺层侵位深熔花岗岩锆石U-Pb定年及其构造意义

原划前寒武纪抱板群混合岩化长英质片麻岩的岩相学、地球化学特征显示为顺层侵位于抱板群变质地层内的深熔花岗岩. 采用北京离子探针中心SHRIMP II对深熔花岗岩的锆石进行U-Pb定年, 获得206Pb/238U年龄为368±3.5 Ma(信度95%, MSDW=1.23), 这个年龄与抱板群变质成因锆石206Pb/238U年龄(362.9±6.1 Ma, 95%信度, MSDW=2.04)非常一致, 表明泥盆纪晚期海南岛曾经历过一次强烈的构造热事件, 这也是海南岛第一次发现的确凿的泥盆纪地质记录. 这次热事件很可能是冈瓦纳大陆在泥盆纪开始的裂解过程受来自深部的热动力影响的结果.     

藏北龙木错东部三岔口地区下奥陶统与泥盆系的不整合界面

在北羌塘三岔口一带采获丰富的腕足类:汉伯矮正形贝及比较种Nanorthis cf.hamburgensis(Walcott).建立了早奥陶世岩石地层单位--三岔口组,是羌塘地区目前有化石控制的最低层位.中、晚泥盆世拉竹龙组与下伏志留系、奥陶系不整合接触关系的进一步确定,证明了羌北-昌都板块与扬子板块的亲缘性,为羌北-昌都板块属性的确定提供了重要证据.     

藏北龙木错东部三岔口地区下奥陶统与泥盆系的不整合界面

在北羌塘三岔口一带采获丰富的腕足类:汉伯矮正形贝及比较种Nanorthis cf.hamburgensis(Walcott).建立了早奥陶世岩石地层单位--三岔口组,是羌塘地区目前有化石控制的最低层位.中、晚泥盆世拉竹龙组与下伏志留系、奥陶系不整合接触关系的进一步确定,证明了羌北-昌都板块与扬子板块的亲缘性,为羌北-昌都板块属性的确定提供了重要证据.     

Paleo—Latitude Variation of Guizhou Terrain from Devonian to Cretaceous

Over 800 paleomagnetic samples were collected from 79 sample localities, ranging in age from Devonian, Carboniferous, Permian to Jurassic for paleo-latitude research on the Guizhou terrain. The area sampled covers 13 counties with an area of about 50000 km². The paleomagnetic results obtained indicate that the Guizhou terrain was at 11.4°S in Devonian, 4.5°-9.3°S in Carboniferous, 2.6° − 4.5°S in Permian, 14.8°N in Triassic and 24.5° − 26.0°N in Jurassic. In the Cretaceous period, the paleo-latitude of the area was at 22.4 − 23.6°N. Therefore, a variation curve of paleo-latitude is established in this paper for the Guizhou terrain from Late Devonian to Late Cretaceous time.