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Sedimentary facies are described in a group of "facies descriptors" which must be distinct, reproducible and exhaustive. A reliable facies description of an outcrop in the field would include: composition, texture, sedimentary structure(s), bedding geometry, nature of bedding contact, fossil content and colour.
The unit represents a series of peritidal to intertidal facies of a Carbonate platform mostly of Obtusum–Oxynotum age, that gradually evolve to open marine/hemipelagic units Vale das Fontes Formation and Lemede formation. [2] [3] This unit is known for its fossil content, including Invertertebrate and vertebrate ichnofossils and fossils. [4] [5]
The lower facies comprises the Peterborough Member, a fossiliferous organic-rich mudstone. This facies and its rocks are commonly known as lower Oxford Clay. The upper facies comprises the middle Oxford Clay, the Stewartby Member, and the upper Oxford Clay, the Weymouth Member. The upper facies is a fossil poor assemblage of calcareous mudstones.
Scolicia de Quartrefages, 1849 is a parataxon of ichnofossils present in sedimentary rocks of marine, marginal lacustrine, alluvial, or fluvial facies. These fossil traces appear in a wide geological range, from the Cambrian to the present. [1]
Facies can be distinguished in a number of ways: the most common are by the lithology (for example: limestone, siltstone or sandstone) or by fossil content. Coral , for example, only lives in warm and shallow marine environments and fossils of coral are thus typical for shallow marine facies.
The Posidonia Shale (German: Posidonienschiefer, also called Schistes Bitumineux in Luxembourg) geologically known as the Sachrang Formation, is an Early Jurassic (Early to Late Toarcian) geological formation in Germany, northern Switzerland, northwestern Austria, southern Luxembourg and the Netherlands, including exceptionally well-preserved complete skeletons of fossil marine fish and reptiles.
The Wealden Group, occasionally also referred to as the Wealden Supergroup, is a group (a sequence of rock strata) in the lithostratigraphy of southern England.The Wealden group consists of paralic to continental (freshwater) facies sedimentary rocks of Berriasian to Aptian age and thus forms part of the English Lower Cretaceous.
Index fossils must have a short vertical range, wide geographic distribution and rapid evolutionary trends. Another term, "zone fossil", is used when the fossil has all the characters stated above except wide geographical distribution; thus, they correlate the surrounding rock to a biozone rather than a specific time period.