苏北盆地TZK9孔磁性地层及重矿物组合特征研究

MAGNETOSTRATIGRAPHY AND HEAVY MINERALS RECORDS OF TZK9 CORE IN SUBEI BASIN

通过对苏北盆地TZK9孔的磁性地层和重矿物组合分析,探索了该地区晚上新世以来沉积物的物源变化特征。古地磁结果显示,TZK9孔的M/G界线位于250.3 m,B/M界线位于78.5 m,并很好记录了2次正极性亚时（Jaramillo和Olduvai）,分别位于129.0-150.2 m与172.55-192.80 m,通过沉积速率外推获得该钻孔的底界年龄约为3.0 Ma。对TZK9孔重矿物组合、特征指数进行分析,并结合淮河及长江下游的重矿物组合特征,揭示在距今3.0-2.6 Ma其沉积物主要来自于淮河流域。而相比晚上新世,第四纪的磷灰石、锆石、金红石、电气石含量增加,表明该地区开始受到了长江流域的影响,而第四纪以来重矿物特征指数（ZTR）逐渐增大可能主要受控于全球气候变化。

The core TZK9 is located in the northeast Taizhou city（ N 32°35＇,E120°6＇）,the south of Subei Basin. The main kinds of lithology in the core are clay and silty clay. Some silt,sand and coarse sand are also found. In this study,382 samples at 30 ~ 60 cm intervals were taken for paleomagnetic measurements,and 17 samples for heavy minerals test. Magnetostratigraphic results show that, the M / G and B / M are found at the depth of 250. 3 and 78. 5 m, respectively.Extrapolation with accumulation rates suggest that the basal ages for sediments in this core is about3. 0 Ma. ATi index was from 50. 97 to 100,while GZI index was 11. 48 to 77. 81,indicating that the source was metamorphic and igneous rocks. During 3. 0 ~ 2. 6 Ma,the main heavy minerals of TZK9 core were ilmenite,epidote,magnetite,garnet and zircon. Comparing the heavy minerals of the TZK9 core with Huai river and Yangtze river,it shows that the sediment came from the Huai river during this time. During 2. 6 ~ 0 Ma,the main heavy minerals are ilmenite,epidote,zircon,apatite,garnet and magnetite. The content of zircon,apatite,tourmaline,rutile increases compared to the previous period,and it indicates that the Yangtze river begin to influence this area in this period. And the ZTR index gradually increased since 2. 6 Ma,which may be related to the change of global climate.