Abstract

PERALTA, Silvio H.  and  CASTRO DE MACHUCA, Brígida. The Stromatolites From The Pan De Azúcar Hill, Western Sierras Pampeanas, San Juan, Argentina. Correlations And Stratigraphic Significance. Ser. correl. geol. [online]. 2010, vol.26, n.1, pp.65-74. ISSN 1666-9479.

The occurrence of stromatolites ("bowl-shaped", Conocollenia? and planar cryptalgal laminites), in limestone beds exposed at the Pan de Azucar hill (31° 25' S - 67° 27' W), Western Sierras Pampeanas, San Juan province, Argentina, is reported. The stromatolite-bearing rocks are interlayered within retrograde greenschist facies metamorphic rocks related to the crystalline basement (Valle Fértil Complex) of the nearby Sierra de La Huerta. The stromatolitic structures are described and interpreted as domal-laminated, bowl-shaped and planar stromatolites. Stratigraphic correlations with the Upper Cambrian stromatolite levels of the La Flecha and Zonda formations and the Upper Cambrian-Early Tremadocian La Silla Formation of Eastern and Central Precordillera, and with the crystalline limestones of the Cambrian Angaco Formation, and the Neoproterozoic Difunta Correa Metasedimentary Sequence at the Pie de Palo range, are discussed herein. Also, the correlation with the Neoproterozoic stromatolite levels from the Tandilia System are considered. On the basis of the geochronologic and biostratigraphic correlation, a probable Late Proterozoic (Ediacaran)-Lower Cambrian age is suggested for the Cerro Pan de Azucar stromatolitic limestones.

Keywords : Stromatolites; Stratigraphic correlations; Western Sierras Pampeanas; San Juan.

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