福島県相馬地域の小池石灰岩におけるネリネア類の産状
1989 年 1989 巻 37 号 p. 83-90
詳細
1989 年 1989 巻 37 号 p. 83-90
The ecology of nerineid gastropods from the Koike limestone, Fukushima Prefecture, northeast Japan, is discussed according to sedimentary facies and mode of occurrence. The Koike limestone is made up of six non-stratigraphic sedimentary facies : -1) calcareous sandstone, 2) oolite, 3) bioclast, 4) oolite-bioclast, 5) coral, and 6) lime mud facies.
The mode of occurrence of nerineids is divided into two types, Type A and B, based on shell size and accumulation geometry. Type A yields sporadic, large, well preserved individuals from a limited number of horizons. One or a few nerineid species occur mainly in the oolite and oolitebioclast facies together with large bivalves. This suggests that Type A nerineids may be autochthonous. Conversely, Type B (Nerinea bed) is represented by accumulations of small-sized nerineids with other organic debris. Nerineid shells in Type B are generally orientated parallel and are probably allocthonous.
