La Fm. Lastres del Kimmeridgiense de Asturias: sedimentología y estudio paleobotánico inicial.

Abstract

The studied vegetable remains belong to four different sections of the Jurassic (Kimmeridgian) Lastres Formation. This formation is more than 500 meters thick and is formed by vertically stacked deltaic sequences. Delta systems were small and fluvially dominated. They were fed from the W and 8W and entered into a restricted tectonically controlled sub-basin (lagoon). The vegetable remains are mainly located in interchannel well-drained swamps and within abandoned channels. They appear both in growth position and as dragged fragments. Most of them were partially to fully replaced by pyrite or carbonate during diagenesis. It Ls concluded that the samples of foliated branches studied belong to Brachvphyiiurn Brongniart (1828) and those of fossilized wood, to Protoenpressinoxyion Eckhold (1922) and Agathoxylon Hartig (1848). From the structure of the latter and from the morphological characteristics of the former, it can be deduced that they lived under a rather warm and relatively dry paleoclimate, without strong seasonal fluctuations.