Sedimentology and palaeontology of the Upper Jurassic Puesto Almada Member (Ca?ad¨®n Asfalto Formation, Fossati sub-basin), Patagonia Argentina: Palaeoenvironmental and climatic significance

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• 作者：Nora G. Cabaleri ; Cecilia A. Benavente ; Mateo D. Monferran ; Paula L. Narv¨¢ez ; Wolfgang Volkheimer ; Oscar F. Gallego ; Margarita D. Do Campo
• 关键词：Facies ; Palaeontology ; Palaeoclimatology ; Upper Jurassic ; Cañ ; adó ; n Asfalto Formation ; Patagonia
• 刊名：Sedimentary Geology
• 出版年：2013
• 出版时间：15 October, 2013
• 年：2013
• 卷：296
• 期：Complete
• 页码：103-121
• 全文大小：6972 K

文摘

Six facies associations are described for the Puesto Almada Member at the Cerro Bandera locality (Fossati sub-basin). They correspond to lacustrine, palustrine, and pedogenic deposits (limestones); and subordinated alluvial fan, fluvial, aeolian, and pyroclastic deposits. The lacustrine-palustrine depositional setting consisted of carbonate alkaline shallow lakes surrounded by flooded areas in a low-lying topography. The facies associations constitute four shallowing upward successions defined by local exposure surfaces: 1) a Lacustrine-Palustrine-pedogenic facies association with a ¡®conchostracan¡¯¨Costracod association; 2) a Palustrine facies association representing a wetland subenvironment, and yielding ¡®conchostracans¡¯, body remains of insects, fish scales, ichnofossils, and palynomorphs (cheirolepidiacean species and ferns growing around water bodies, and other gymnosperms in more elevated areas); 3) an Alluvial fan facies association indicating the source of sediment supply; and 4) a Lacustrine facies association representing a second wetland episode, and yielding ¡®conchostracans¡¯, insect ichnofossils, and a palynoflora mainly consisting of planktonic green algae associated with hygrophile elements. The invertebrate fossil assemblage found contains the first record of fossil insect bodies (Insecta-Hemiptera and Coleoptera) for the Ca?ad¨®n Asfalto Formation. The succession reflects a mainly climatic control over sedimentation. The sedimentary features of the Puesto Almada Member are in accordance with an arid climatic scenario across the Upper Jurassic, and they reflect a strong seasonality with periods of higher humidity represented by wetlands and lacustrine sediments.