The Coal-Forming Plants of Early Cretaceous Resin Coals of the Southern Primorye (Russia) and Heilongjiang Province (China)

It has been established that the main coal-forming plants of the Lipovtsy Formation of the Razdolnaya Basin in the Southern Primorye region, Russia, the Dongning Formation of the Dongning Basin, and the Muling Formation of the Laoheishan Basin in the Heilongjiang Province of China were various ferns, bennettites Nilssoniopteris rhitidorachis and Pterophyllum sp., and conifers dominated by Miroviaceae. They produced resinites of this region. It is difficult to explain the phenomenon of the dominance of the Miroviaceae (plants characteristic of high-latitude floras) and the species diversity of the bennettites (thermophilic indicators). The paleoenvironments of the Razdolnaya, Dongning and Laoheishan basins in the Aptian were highly stressful, which follows from the dominance of Miroviaceae (characterized by adaptations to unfavorable living conditions), as well as finds of Tarphyderma (Cheirolepidiaceae) and the first angiosperms. The discovery of megaspores of aquatic fern Balmeisporites in the Dongning Formation section indicates accumulation of its deposits in fresh or brackish water bodies under warm and humid conditions. Small fragments of light-yellow resin were found in the coal-bearing interbed of the Dongning Formation. They were produced by conifers Pinaceae or Taxodiaceae. It is possible that coniferous forests, the resin producers, gained the wide distribution in the Aptian, being spread over the entire territory of present-day Northeast China and Transbaikalia. The comparison with coal-forming plants of Jurassic resinites of the Tkvarcheli deposit in the Republic of Abkhazia (South Caucasus) was conducted. Despite the difference in age, their proportions are the same as in the Far Eastern resinites: the dominance of Miroviaceae (Mirovia oskolica) at significant contribution of bennettites.