土耳其-高加索-喜马拉雅一线白垩纪大洋红层对比

通过收集土耳其、高加索和特提斯喜马拉雅地区的白垩纪地层资料,着重对比研究上白垩统大洋红层的分布格局和沉积特征,为进一步进行全球大洋红层对比提供基础数据和资料。对比分析表明:它们具有环特提斯该时代近于同期地层的一般特征,其时代一般为Turonian Campanian期,在特提斯喜马拉雅地区跨度较大,为Albian Campanian期,岩性主体为灰岩,颜色与Fe2O3 的含量密切相关,富含浮游有孔虫及其组合,沉积速率低,沉积环境一般为半深海,沉积深度为500~1 000 m。

Correlation of Cretaceous oceanic red beds in Turkey, Caucasus and Himalaya

This paper provides basic data for global Cretaceous Oceanic Red Beds (CORB) correlation. It shows that some common features have been shared by the CORB with coeval strata around the Peri-Tethys in Turkey, Caucasus and Tethys Himalayas. The CORB are widely exposed in the Rhodope-Pontide and the Eastern Pontides area of Turkey, in the Carbonate Daghestan of Caucasus, in the Karamba Complex and Zanskar Range of Ladakh (Northern Indian) and in the Gyangze of Tibet of the Himalayas Tethys. The CORB is rich in planktonic foraminifera, e.g. Helvetoglobotruncana Helvetica, Marginotruncana coronata, Globotruncana ventricosa, Globotruncana sp., Globotrancanita elevata, Globotruncanidae,Heterohelicidae,Globigerinidae, etc. On the basis of biostratigraphic correlation, the CORB are generally from the Turonian through to the Campanian in Turkey and in the Caucasus. However, in Tethysides of the Himalayas, ages vary from Albian to Campanian. The sedimentary characteristics of the CORB in these areas are discussed, including lithology, thickness, colour, clay mineral composition and sedimentary structure, etc. The main rock type of the CORB is limestone, but in Tethys Himalayas it is shale and marlstone. The thickness of the CORB is generally several dm to 100 m, but in Zanskar area, it varies from 3 m (Hompatta section) to 140 m (Sneaste section). The color of the CORB is red, reddish or pink, which may be related to the content of Fe_2O_3. In general, Fe~(3+)of marine deposit comes from weathered continental deposit and volcanics. In the CORB of the studied area, Fe~(3+) content is high and total organic carbon (TOC) content is very low, which indicates that the CORB was formed in oxidized bottom water rich in dissolved oxygen, and that Fe~(3+) resulted mainly from oxidation of Fe~(2+) during the early diagenetic stage. Sedimentation rate of the CORB is low. Clay mineral composition of the CORB is illite and montmorillonite. The CaCO_3 content of limestone is more than 80%. There are finely laminated and subtle grading in pelagic carbonate and slump structure in marlstone, so sedimentary environment of the CORB is generally bathyal. The depositional depth is lower than marginal break, which may be from 500 m to 1000 m.