The Xiagou Formation is the middle unit of the Xinminpu Group. It is named for its type site in Xiagou, in the Changma Basin of Gansu Province, northwestern China and is considered Early Cretaceous in age. ( is a province located in the northwest of the People's Republic of China. The Early Cretaceous ( timestratigraphic name or the Lower Cretaceous ( logstratigraphic name is the earlier of the two major divisions of the Cretaceous It is known outside the specialized world of Chinese geology as the site of a lagerstätte in which the fossils were preserved of Gansus yumenensis, the earliest true modern bird. Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit A Lagerstätte ( German; literally place of storage; plural Lagerstätten) is a sedimentary deposit that exhibits extraordinary fossil Gansus is a Genus of aquatic Birds that lived during the Albian stage of the Early Cretaceous period (around 110 million The laminated yellowish mudstones of the Xiagou Formation are the lithified remnants of varves that were laid down as extremely fine silt settled to the bottom of a tranquil freshwater lake. Mudstone (also called mudrock) is a fine grained Sedimentary rock whose original constituents were Clays or Muds Grain size is up A varve is an annual layer of Sediment or Sedimentary rock. The word 'varve' is derived from the Swedish word varv whose Silt is Soil or rock derived Granular material of a Grain size between sand and clay The result was dense anoxic bottom sediment, where the lack of bacteria slowed the processes of decay, preserving uncompressed fossils in details that include feather impressions and remnants of the webbing between the bird's toes.
Other fossils from the Xiagou will permit detailed recreation of an Early Cretaceous lake ecology. There are fossils of abundant fish fauna, Charophyta and Ostracods. The Charophyta are a division of Green algae, including the closest relatives of the Embryophyte plants Ostracoda is a class of the Crustacea, sometimes known as the seed shrimp because of their appearance
See also
- List of fossil sites (with link directory)
References
- "Early Cretaceous Ostracods From The Xiagou Formation In Xiagou, Gansu Province" in Acta Micropalaeontologica Sinica part 2, 2005
- Bureau of Geology and Mineral Resources of Gansu Province,Regional Geology of Gansu Province (Geological Publishing House, Beijing, 1989), pg. This is a worldwide list of important and/or well-known localities where Fossils have been found 692
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