| Autor: | Alfonso Yébenes Simón, Margarita Díaz Molina |
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| Rok vydání: | 1987 |
| Předmět: | |
| Zdroj: | Estudios Geológicos. 43 |
| ISSN: | 1988-3250 0367-0449 |
| Popis: | In this work we aim to resconstruct the paleoenvironmental context of the Galve archosaurs. The archosaurs remains are most frequently found in the lower 500 m of the Early Cretaceous succession. This succession is subdivided into four units which overly Kimmeridgian-Portlandian sediments. The first Cretaceous unit is characterized by the predominance of mudstones. The coarser terrigenous material (fine to medium sand) is not typically channalized, but it most frequently occurs in lenticular bedding, isolated dunes and sheets. This is interpreted as a muddy intertidal tlat deposit. The appearance of limestones marks the base of the following unit. The unit is formed by sequences composed of marls and micrites with abundant charophytes, bivalbes, gastropods, fish teeth and vertebrate remains. This facies corresponds to lacustrine deposits, formed in fresh to brackish water. The next unit is composed of mudstones, sands, sandstones and gravels. The sands and gravels are found in channels. The sandstones form thin sheets, interpreted as overbank deposits. Fluvially dominated channels predominate in the lower part of the unit. Towards the top the channels are tidally influenced. In the mudstones we find vertebrate remains, including Archosaurs and fish teeth, bioturbation and colours resulting from gleying. Also in the channels we find fragments of vertebrates and plant remains. This unit is interpreted as a multiple fluvial system, formed by channels of low sinuosity which evolve into a tidally influenced delta plain. The last unit presents a wide variety of lithologies, including conglomerates, sandstones, mudstones, marls and limestomes. The marls are the most abundant rock type, and occasionally lenticular bedding and charophytes occur withim them. The coarser terrigenous material is found in small channels containing oyster, or forms thin sheets. The limestones are predominantly micrites and wackestones containing abundant oysters and gastropods. This is interpreted as the most distal facies of the deltaic system, and it is transitional with bay sediments. The Archosaurs remains are found in several facies: in channel fills, in overbank deposits, within the flood plains, in lakes and in intertidal flats. |
| Databáze: | OpenAIRE |
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