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Javelina Formation
The Javelina Formation is a geological formation in Texas. Dating has shown that the strata date to the Maastrichtian stage of the Late Cretaceous, approximately 70 to 66.5 million years old.〔 The middle part of the formation has been dated to about 69 million years ago plus or minus 1 Ma and the top situated near the Cretaceous–Paleogene boundary (in the overlying Black Peaks Formation〔Woodward, H. N. (2005). Bone histology of the sauropod dinosaur Alamosaurus sanjuanensis from the Javelina Formation, Big Bend National Park, Texas.〕), dated to 66 Ma ago.〔Lehman, T.M., McDowell, F. and J. Connelly, J. (2006). "First isotopic (U-Pb) age for the Late Cretaceous ''Alamosaurus'' vertebrate fauna of West Texas, and its significance as a link between two faunal provinces." ''Journal of Vertebrate Paleontology'', 26: 922–928.〕 Dinosaur remains are among the fossils that have been recovered from the formation.〔Weishampel, David B; et al. (2004). "Dinosaur distribution (Late Cretaceous, North America)." In: Weishampel, David B.; Dodson, Peter; and Osmólska, Halszka (eds.): The Dinosauria, 2nd, Berkeley: University of California Press. Pp. 574-588. ISBN 0-520-24209-2.〕
==Age==
The exact age range of the Javelina Formation has been difficult to determine.〔Sullivan, R.M., and Lucas, S.G. 2006. "(The Kirtlandian land-vertebrate "age" – faunal composition, temporal position and biostratigraphic correlation in the nonmarine Upper Cretaceous of western North America )." New Mexico Museum of Natural History and Science, Bulletin 35:7-29.〕 Only one geological site in the Javelina Formation has thus far yielded the correct rock types for radiometric dating. The outcrop, situated in the middle strata of the formation about 90 meters below the K-Pg boundary and within the local range of ''Alamosaurus'' fossils and below two sites that have yielded ''Quetzalcoatlus'' fossils, was dated to 69.0 plus or minus 0.9 million years old in 2010.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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