西南极利文斯顿岛晚三叠世遗迹化石及其环境意义

TRACE FOSSILS AND THEIR ENVIRONMENTAL SIGNIFICANCE IN THE MIERS BLUFF FORMATION, LIVINGSTON ISLAND, WEST ANTARCTICA

西南极利文斯顿岛晚三叠世迈尔斯陡崖组形成于海底浊积扇中扇的上、下部分 ,发育着许多海相遗迹化石。在采集到的样品中鉴定共有 1 5个遗迹属、1 6个遗迹种 ,其中有1 0个可以鉴定到遗迹种、两个比较种 ,4个只鉴定到遗迹属 ,未鉴定到遗迹种 ;并建立了 1个新遗迹属及新遗迹种是文献中从未发现的。除新遗迹属种外 ,其余 1 4个遗迹属 ,1 5个遗迹种都曾经在深海相浊积岩内发现过 ,Belorhaphe、Glockerichnus、L ophoctenium、Rhabdoglyphus、Pale-odictyon、Sublorenzinia、Spirophycus、Strobilorhaphe、Tuberculichnus、Cochlichnus等属于浊流前产生在深海相泥岩内的高度分异的雕画迹 (Graphoglyptida) ,它们产于泥岩却保存为上覆砂岩底面的铸型凸起。Fucusopsis和 N eonereites却产生在砂岩内代表浊流后形成的沉积后遗迹组合。这些遗迹化石属深水的 Nereites遗迹相 。

The Miers Bluff Formation in the Hurd Peninsula, Livingston Island, West Antarctica, has been interpreted to be a sequence of turbidites, which may represent sedimentation upper and lower mid-fan settings. Its thickness is more than 3 000 m (base unknown), in age of Late Triassic. Many trace fossils of the whole succession were found in the turbidites of the Miers Bluff Formation. All of these trace fossils are deep sea ichnofossils. There are fifteen ichnogenus, sixteen ichnospecies. They are Belorhaphe ichnosp., Cochlichnus ichonosp., Fucusopsis annulata Palibin, Glockerichnus ichnosp., Halyminidium sublumbricoides( Azpeitia), Lophoctenium comosum Richter, Neonereites uniserialis Seilacher, Paleodictyon ichnosp., Paleaichnus antarctics ichnogen. et ichnosp. nov., Planolites montanus Richter, Rhabdoglyphus grossheimi Vassoevich, Spirophycus bicornis Heer, Strobilorhaphe ichnosp., Sublorenzinia cf . plana Ksiazkiewicz, Tuberculichnus meandrinus Ksiazkiewicz, Tuberculichnus bulbosus Ksiazkiewicz.. We, moreover, found a new trace fossil and propose a new ichnogenus and new ichnospecies Paleaichnus antarctics ichnogen. et ichnosp. nov.. Except the new ichnogenus and ichnospecies, others had been found in deep sea turbidites. Some are in mudstone, preserved in the cast convex of overlying sandstone sole. They formed before turbidity flows occurred and belong to the high differentiated Graphoglyptida of abyssal mudstone, for example, Belorhaphe, Glockerichnus, Lophoctenium, Rhabdoglyphus, Paleodictyon, Sublorenzinia, Spirophycus, Strobilorhaphe, Tuberculichnus and Cochlichnus et al. Others as Fucusopsis and Neonereites are preserved in sandstones and stand for trace assemblages after turbidity sedimentation. These trace fossils are typical members of abyssal “Nereites” ichnofacies, and provide for the depositional environment of the Miers Bluff Formation.