Jurassic Flora and Palaeoecology of the Kamala Formation (Kansk-Achinsk coal basin), Central Siberia

Abstrakt

The Kansk-Achinsk Basin is one of the biggest reserves of brown coal in Russia. Jurassic coalcontaining terrestrial deposits bearing plant remains crop out in several localities. This work is focused on five localities of the Kansk Basin of the Middle Jurassic Kamala Formation within the

Rybinskaya Formational Zone containing fossil plants. The studied material comprises 30 plant morphospecies. They are assigned to: pteridophytes Equisetites, Coniopteris, Cladophlebis and

Raphaelia, Bennettitales Pterophyllum, Ginkgoales (Ginkgo, Sphenobaiera and Eretmophyllum),

Czekanowskiales (Czekanowskia and Phoenicopsis), Coniferales (Pityophyllum). There are several plant remains of uncertain systematic position such as roots (Redicites sp.), cones (Equisetostachys sp.) and fossil wood. Palaeoecological analysis identified three palaeoenvironments (facies): periodically flooded alluvial plain dominated by Czekanowskia-Phenicopsis, swamp-semiaquatic dominated by Equisetites, Coniopteris, Cladophlebis, Phenicopsis and slope and upland vegetation dominated by Sphenobaiera, Ginkgo, Eretmophyllum, Pityophyllum.

Palaeoclimatological conditions of the studied area are reconstructed as warm temperate climate with seasonal temperature variations.

Presence such index-species of flora as Coniopteric maakiana, in association with Phoenicopsis markovitchae and Czekanovskia kanensis indicate Early-Middle Jurassic age. Absence of typical for Jurassic Siberian flora Podozamites leaves among the plant remains presumabely demonstrate semi-isolated sedimentory basin for species invation. The composition of the plant-bearing Kamala

Formation allows us to conclude that the deciduous vegetation was growing in a temperate climate with annual fluctuations in temperature.