Volcanogenic Cretaceous of Northeast Asia: Taphofloras of the Ul’ya and Urak Interfluve (on the Knowledge of E.L. Lebedev’s Legacy)

Abstract

In the 1970s, the geological mapping in Northeast Asia, in the Ul’ya–Urak interfluve was undertaken by the Aerogeologiya research and production enterprise, while E.L. Lebedev, an employee of the Geological Institute, USSR Academy of Sciences, collected plant fossils. Together with geologists of that enterprise, he developed a new stratigraphic chart of the region, which turned out to be incorrect, as appeared later, being based on ideas on the floral development in the mid-Cretaceous time. Lebedev made vast collections that include several thousand remains of ancient plants. However, this material turned out to be attributed to nonexistent stratigraphic units. This made it of little use for further study. Our investigation has demonstrated that the most representative collections made by Lebedev in the Ul’ya–Urak interfluve (taphofloras of the sites 101 and 107–110, 28, 20, 25, 27, 70–78, 153, 154) come from the first sequence of felsic volcanics of the homodromous succession of volcanism in the Okhotsk–Chukotka Volcanogenic Belt. In the Ul’ya Trough, this sequence was initially called the Amka Formation. It is shown that the previously collected palaeofloristic material is quite representative and in general is of a good preservation. In the future, it could be monographically studied and described as a large regional palaeofloristic and phytostratigraphic object—the Ul’ya flora.