Frentzevka Fm

Partizansk depression of southern Primorye Basin (S-12; E of Vladivostok). Locally the upper formation of the Suchan Gr.

The upper member (Frentsevka Fm) of the generalized SevernySuchan Fm (Severny Suchan Fm) (135-430 m in type section) is composed of fine-grained sandstones with marine fauna, sandstones, siltstones and silty mudstones.

The Frentsevka fossil plant assemblage identified in the upper member (¼Frentsevka Formation) is diverse (55 taxa) and is characterized by domination of ferns (18 taxa), subdomination of conifers (13 taxa) and presence of cycadophytes (5 taxa). The typical taxa of the assemblage are represented by ferns Osmunda denticulata, Anemia dicksoniana, Birisia onychioides, Vargolopteris rossica, Teilahardia tenella, Lobifolia novopokrovskii, and conifers Athrotaxopsis expansa, Athrotaxites berryi, Sequoia ambigua, S. reichenbachi, Podozamites tenuinervis, Elatocladus obtusifolius, Sphenolepis kurriana, cycadophytes Nilssonia densinervis (Volynets, 2005). The characteristic feature of the assemblage is the domination of ferns (35%) and conifers (23%), decrease of cycadophytes (9%) and permanent presence of early angiosperms (14%). It is dated as middle-upper Albian (Volynets, 2005). This assemblage is subdivided into two assemblages corresponding to the lower and upper parts of the member (Volynets, 2005). The assemblage from the upper part of the member differs by the presence of angiosperms.