Trace fossil types from the Lower Cretaceous strata and palaeoclimates in the Minhe Basin

Seven ichnogenera are recog nized for the first time in the Lower Cretaceous strata of the Minhe Basin:Skolithos, Thalassinoides, Palaeophycus, Phycodes, Ancorichnus, Planolites and Scoyenia, which may be grouped into three assemblages:Skolithos-Planolites assemblage in the Zhujiatai Formation, Thalassinoides-Palaeophycus assemblage in the Yanguoxia Formation, and Planolites-Scoyenia assemblage in the Hongg ucheng Formation. These trace fossils occur mainly in the relatively higher-energy or lower-energy environments, and thus have nothing to do with water depth. On the contrary the palaeoclimates are believed to be the main controls on the ty pes and morphological fo rms of the trace fossils from the continental river and lake environments. The variations in palaeoclimatic conditions always have decisive effects on fluid flow, energy, salinity, temperature, oxygen and nutriments contents, and basement features.