河南泌阳凹陷古近纪核桃园组遗迹化石组合及其环境意义——兼论深水湖泊遗迹相特征

南襄盆地泌阳凹陷古近纪核桃园组湖泊沉积中发育大量遗迹化石,含5个遗迹组合,形成于从滨湖到深湖的不同沉积环境中。Taenidiumserpentinum遗迹组合反映稍有覆水并周期性暴露的低能滨湖环境;Skolithos linearis遗迹组合代表湖泊中上临滨环境;Planolites montanus遗迹组合与低能浅湖环境有关;Skolithos verticalis遗迹组合形成于浅湖的远源风暴沉积中;Semirotundichnus dongyingensis遗迹组合发育在贫氧的半深湖-深湖沉积环境中。

TRACE FOSSIL ASSEMBLAGES AND THEIR ENVIRONMENTAL SIGNIFICANCE FROM HETAOYUAN FORMATION OF PALAEOGENE IN BIYANG DEPRESSION OF HENAN PROVINCE

Abundant trace fossils are discovered from lacustrine sediments of Palaeogene Hetaoyuan Formation, Biyang depression, Nanxiang basin. They are preserved in the deposits in different sedimentary environments from marginal to deep lake and constitute 5 ichnoassemblages. Taenidium serpentinum ichnoassemblage is dominated by small, horizontal-distributed and meniscate backfilled burrows and consists of Taenidium serpentinum,Planolites montanus, P. beverleyensis, Helminthopsis ichnosp. and rhizoliths. It occurs in low energy, very shallow lacustrine environment and is indicative of periodic subaerial exposure. Skolithos linearis ichnoassemblage contains vertical and high-inclined trace fossils and is preserved in fine sandstones of upper and middle shoreface environment that displays relatively high wave or current energies. Planolites montanus ichnoassemblage comprises only one trace fossil, Planolites montanus, and is preserved in mudstone and siltstone of low energy, shallow lacustrine environment. Skolithos verticalis ichnoassemblage is often interbedded with Planolites montanus ichnoassemblage in shallow lacustrine sediments but it is related to storm-induced deposition. Semirotundichnus dongyingensis ichnoassemblage is characterized by abundant feeding trail Semirotundichnus dongyingensis, companying with the simple feeding burrows Planolites montantus,Helminthopsis ichnosp.,farming trail ?Paleodictyon sp., fish squamae and dark plant detritus that indicates oxygen-deficient environments of deeper lake.