Cretaceous nonmarine dinoflagellates from northeast China

Abstract

Nonmarine Cretaceous dinoflagellates were recovered in the last decade from a number of basins in northeastern China, which are mostly oil-bearing. These dinoflagellates show close relationship to the water salinity of palaeoenvironments. Two types of dinoflagellate assemblages may be recognized, one from freshwater to slightly brackish and another from slightly brackish to brackish. The former is characterized by the high dominance of ceratioid cysts, particularly species of Nyktericysta and Vesperopsis whereas the composition of the latter is more varied with gonyaulacoid, peridinioid and ceratioid cysts, and varies with the water salinity.

New emendations are proposed to the genera Nyktericysta and Vesperopsis based on new information gained from these nonmarine species and specimens. One new genera Quantouendinium is proposed to accommodate its species formerly placed improperly in Nyktericysta. Detailed descriptions and combinations or special remarks are given to the following species: they are Vesperopsis glabra, V. sanjiangensis, V. jixianensis, Nyktericysta reticulata, N. puyangensis, N. beierensis, N. (Hastodinium). ramuliformis, N. (Hailaera). hailaerensis, N. (Hailaera). nebulosa, Contrangularia reticulata, C. granulata, Quantouendinium dictyophorum, Q. microreticulata, Q. spinosum, Tetrachacysta granulata, T. spinulosa, T. tuberculata and an acritarch Spicadinium akidoton. One new genus Quantouendinium and one new species Vesperopsis yanjiensis are described.

The palaeoecology of nonmarine dinoflagellates is discussed based on information gathered from China.