Depositional environments and taphonomy of the bone-bearing beds of the Lower Cretaceous Kuwajima Formation, Tetori Group, Japan
Depositional environments and taphonomy of the bone-bearing beds of the Lower Cretaceous Kuwajima Formation, Tetori Group, Japan
复制标题
DOI：
--
复制
发表时间：
2005
期刊：
影响因子：
--
通讯作者：
S. Isaji
中科院分区：
文献类型：
--
作者：
S. Isaji
描述了下白垩统Kuwajima组（Tetori群）的含骨层。在河漫滩上形成的河道间沉积中，存在三种含骨层相（相一：碳质砂岩；相二：深灰色细粒粉质砂岩；相三：深绿灰色泥岩）。沉积物的粒度和各含骨层中出现的植物和软体动物化石表明，相I沉积于泥炭沼泽，相II沉积于浅湖，相III沉积于植被沼泽。孤立的小骨头和牙齿是最丰富的脊椎动物化石。相II的常见元素是水生脊椎动物，如鱼类和海龟。相III的特征是陆生蜥蜴、三齿纲突触类动物和哺乳动物的出现。II相和III相的脊椎动物化石组合虽然都是准地组合，但彼此之间并没有混合。相比之下，第一相为异位相，主要由第二相的再加工沉积物组成。含骨层的沉积环境与其化石组合的组成密切相关，表明不同相保存了浅湖与植被沼泽环境之间原有的动物区系差异。
Thebone-bearing beds of the Lower Cretaceous Kuwajima Formation (Tetori Group) are described. Three facies of bone-bearing beds (Facies I: carbonaceous sandstones; Facies II: dark grey fine-grained silty sandstones; Facies III: dark greenish-grey mudstones) are present in inter-channel deposits that originated on a floodplain. The grain size of the sediments, and plant and molluscan fossils occurring in each bone-bearing bed, indicate that Facies I was deposited in a peat marsh, Facies II in a shallow lake, and Facies III in a vegetated swamp. Isolated small bones and teeth are the most abundant vertebrate fossils. Common elements in Facies II are aquatic vertebrates such as fishes and turtles. Facies III is characterized by the occurrence of terrestrial lizards, tritylodontid synapsids and mammals. Vertebrate fossil assemblages in Facies II and III are not mixed with each other even though they both represent parautochthonous assemblages. In contrast, Facies I is allochthonous, and is composed mostly of reworked sediments from Facies II. Depositional environments of the bone-bearing beds are strongly correlated with the composition of their fossil assemblages, indicating that different facies preserve the original faunal differences that existed between the shallow lake and vegetated swamp environments.