湘中下石炭统痕迹化石及其环境分布

湘中下石炭统中发育有非常丰富的痕迹化石，本文报道了在其中鉴别出的１７种痕迹化石，并对其组合特征及环境分布进行分析，划分出Ｆｕｃｏｓｏｐｓｉｓ组合、Ｓｋｏｌｉｔｈｏｓ组合、ｐａｌａｅｏｐｈｙｃｏｓ组合、Ｒｈｉｚｏｃｏｒａｌｌｉｕｍ组合、Ｃｈｏｎｄｒｉｔｅｓ组合等。它们分别与潮坪－湖、障壁砂坝、滨外碎屑陆棚、滨外浅水碳酸盐陆棚及深水碳酸盐陆棚等环境相对应。文中还对区内几种常见的痕迹化石如Ｔｈａｌａｓｓｉｎｏｉｄｅｓ、Ｐｌａｎｏｌｉｔｅｓ、Ｚｏｏｐｈｙｃｏｓ及Ｃｈｏｎｄｒｉｔｅｓ等的环境意义做进一步探讨。

Trace fossils and their environmental distributions for the Lower Carboniferous of Central Hunan

Lower Carboniferous in Central Hunan, South China includes the Shaodong, Menggongao, Liujiatang, Shidengzi, Ceshui and Zimenqiao Formations. The Shaodong and Ceshui Formations consist mainly of elastic rocks and formed in the offshore muddy shelf and shoreline barrier-lagoon environments respectively. The other four formations consist mainly of carbonate rocks intercalated with the calcareous mudstone and shale, which were formed in the off shore carbonate shelf(ramp)system. The Menggongao and Shidengzi Formations mainly formed in the offshore shallow carbonate shelf, the Liujiatang Formation mainly formed in the deep shelf and shelf basin, and the Zimenqiao Formation formed in the petitidal and offshore shallow carbonate shelf environments. Abundant trace fossils were found in the Lower Carboniferous of Central Hunan. They are classified into five associations (Fig. 5): Fucusopsis Ass., Skolithos Ass., Palacophycos Ass., Rhizocorallium Ass, and Chondritcs Ass., which were formed in Lagoon-tidal flat, barrier sand bar, offshore muddy shelf, shallow carbondvte shelf, deep shelf and shelf basin environments respectively. In the Lower Carboniferous of Central Hunan, Thalassinoidcs, Planolites, Zoophycos and Chondrites are the most common trace fossils. The occurences of these trace fossils can reflect the situation of the oxygen contents of the bottom sediments and, furthermore, indicate the paleobathymetry. In general, the Thallatinoides and Planblites trace fossils are abundant at the shallower part of the ramp and the Zoophycos and Chondrites trace fossils often occur at the deeper part of the ramp.