浙闽地区白垩纪中期古土壤类型与古气候

对浙江西南和福建西南数个小型沉积盆地的11个剖面和观察点进行了地质调查,在中国大陆第一次识别了白垩纪中期三种古土壤类型,分别是粘土红壤、钙质土壤和铁质土壤型。粘土红壤型以发育红色(粉砂质)泥岩、生物潜穴、植物根系(根迹)为特点,钙质土壤型以发育紫灰色调钙质泥岩、钙质结核(含姜结石)为标志,铁质土壤型显示了紫红和橙黄色调泥岩、粉砂岩与铁质皮壳及结核组合。进而提出,白垩纪中期的阿普特期-阿尔布时期,在浙江西南金华—衢州—丽水盆地、中部的永康盆地大量发育钙质土壤,以横山组、中戴组、金华组、馆头组和朝川组为代表,属于亚热带干旱—半干旱气候产物;在闽西南地区出现丰富的铁质氧化型土壤,由板头组、均口组和沙县组为代表,反映热带半干旱气候;之后的白垩纪中期赛诺曼期(衢县组)在浙西局部地区气候变为亚热带温湿气候,古土壤变为粘土红壤型,开始产生较为丰富的生物活动,而闽西南主体气候格局可能不变,但沉积建造因区域构造断隆作用转变为巨厚的"丹霞"砾岩。

Paleosols of the mid-Cretaceous:A report from Zhejiang and Fujian,SE China.

An investigation on the mid-Cretaceous continental sediments was recently executed in both SW Zhejiang and SW Fujian provinces,SE China.It is the first time to report the Cretaceous paleosols in mainland China.Three types of paleosol are recognized as argillisol,calcisol,and oxisol based on the observation of eleven cross sections in field.The argillisol horizon is characterized by burrows and root traces within reddish(silty) mudrock,the calcisol is marked by calcareous concretion within pale purple calcareous mudrock,and the oxisol is the association of ferric tegument and concretion within reddish purple,grayish orange siltstone and mudrock.According to climate direction of paleosol type,it is proposed that it could have been in aridity or semi-aridity of subtropic during the Aptian-Albian epoch of the mid-Cretaceous in SW Zhejiang,where the calcisol was recorded in the Hengshan Formation,Zhongdai Formation,Jinhua Formation,Guantou Formation,and Chaochuan Formation;and at the same time,it was in semi-aridity of tropic in SW Fujian indicated by oxisol within the Bantou Formation,Junkou Formation,and Shaxian Formation.In the Cenomanian,it could have become more moisture in SW Zhejiang evidenced by the production of the argillisol within the Quxian Formation,whereas the paleoclimate in SW Fujian in the Cenomanian might have been similar to that in the Aptian-Albian even if the sediments were changed as huge conglomerates(so-called "Danxia Landorm") by tectonism.