四川省若尔盖县巴西—吉求地区晚三叠世遗迹化石及遗迹相  

FEATURES AND DISTRIBUTION OF VOLCANIC ROCK ASSOCI ATIONS OF VARIOUS AGES IN THE BEISHAN AREA, GANSU

作　　者：杨逢清[1,2] 王治平[1,2] 杨恒书 

机构地区：[1]中国地质大学地学院 [2]四川省地矿局川西北地质大队

出　　处：《中国区域地质》1997年第3期291-296,共6页Regional Geology of China

摘　　要：四川若尔盖巴西—求吉地区晚三叠世首次发现了丰富的遗迹化石，经鉴定有２２个遗迹属、３４个遗迹种。根据不同遗迹属在不同层位中的相对丰度，建立了４个遗迹组合：（１）Ｈｅｌｍｉｎｔｈｏｐｓｉｓ—Ｐｈｙｃｏｓｉｐｈｏｎ组合；（２）Ｄｅｎｄｒｏｔｉｃｈｎｉｕｍ—Ｎｅｏｎｅｒｅｉｔｅｓ组合；（３）Ｐａｌｅｏｄｉｃｔｙｏｎ组合；（４）Ｔａｅｎｉｄｉｕｍ—Ｃｏｓｍｏｒｈａｐｈｅ组合。上述遗迹组合大致相当于Ｓｅｉｌａｃｈｅｒ的Ｚｏｐｈｙｃｏｓ遗迹相和Ｎｅｒｅｉｔｅｓ遗迹相。依据遗迹化石进行了沉积环境分析，认为该区晚三叠世的沉积环境经历了大陆斜坡中下部—大陆斜坡下部—深海盆地的演变。On the basis of a large amount of data combined with field work in some ore districts and petrochemical work, the authors have compiled a map of volcanic rock associations and their distribution in the Beishan area, summarized the features of volcanic rock associations of various ages and their distribution in the Beishan area. It is suggested that the volcanic rocks in most horizons belong to the successively differentiated rock association of normal K Na type and dominantly calc alkaline, intermediate to acid compositions, while basic and bimodal volcanic rock associations of the tholeiite series are only developed in Proterozoic, Middle Ordovician, Upper Ordovician and Lower Permian strata. The alkaline series is scanty and no alkaline rocks (σ>9.0) occur in the study area. Intermediate acid rocks of the potassic type may appear in some ore districts such as Baishantang, Gongpoquan and Langwashan. The features of volcanic rocks reflect the tectonic evolution history of multiple 'openings' and 'closings' in the Beishan.

关 键 词：遗迹化石 遗迹相 晚三叠世 若尔盖县 古动物 

分 类 号：Q915.651[天文地球—古生物学与地层学]