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__NOTOC__ The Portezuelo Formation is a geologic formation outcropping in the Mendoza, Río Negro and Neuquén provinces of Argentina. It is the fourth-oldest formation in the Neuquén Group and the older of the two formations in the Río Neuquén Subgroup. Formerly that subgroup was treated as a formation, and the Portezuelo Formation was known as the Portezuelo Member.〔Sánchez ''et al.'' (2006)〕 The type locality of the Portezuelo Formation is the mountain range known as Sierra del Portezuelo in Neuquén province.〔Wichmann (1929)〕 This formation conformably overlies the Lisandro Formation of the Río Limay Subgroup. In the top layers it grades into the Plottier Formation, the younger formation within the Río Neuquén Subgroup. Sandstones and siltstones, probably deposited under fluvial conditions, make up the Portezuelo Formation. There are also occasional cemented claystone deposits, as well as numerous paleosols (fossil soils). The formation varies between 95 and 130 meters thick throughout its range.〔Leanza ''et al.'' (2004), Sánchez ''et al.'' (2006)〕 ==Age== Era: Mesozoic Period: Late Cretaceous Age: late Turonian to early Coniacian Absolute Age: ~91 to ~88 mya 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Portezuelo Formation」の詳細全文を読む スポンサード リンク
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