Rasgos micropaleontológicos de los depósitos de la transgresión Entrerriense-Paranense en la cuenca Chaco-Paranense y Noroeste Argentino

• Autores: Hugo Guillermo Marengo
• Localización: Serie correlación geológica, ISSN-e 1666-9479, ISSN 1514-4186, Vol. 14, Nº. 1, 2000
• Idioma: español
• Títulos paralelos:
  • Micropaleontological outlines of the Entrerriense-Paranense transgression beds in the Chaco-Paranense basin and the Northwest Argentina
• Enlaces
  • Texto completo (htm)
• Resumen

  • From the Middle Miocene to the Upper Miocene an extended transgression flooded a significant portion of the Argentinian territory, and it reached the south of Bolivia and Paraguay. This transgression has been generally known as the entrerriense or paranense transgression (TEP). This study summarizes all the available information about calcareous marine microfossils deposited by the TEP in the NW argentine region, Chaco-Paranense basin, and west Mesopotamia, Argentina. 66 cores recovered from four drillings on the Diamante area, Entre Ríos province, have been analyzed, and they constitute the first subsurface study, and the first study of the complete sequence of the Paraná Fm in its type area.

    Foraminiferal assemblages belong of the Protelphidium tuberculatum informal Zone. P. tuberculatum and Ammonia parkinsoniana are widely dominant in the studied areas. In almost all regions the microfaunas are typical of shallow and brackish waters, but in some localities of SW Entre Ríos province and central Santa Fe province, microfaunas that indicate normal marine conditions have been recognized. TEP foraminiferal assemblages are very similar to those wich live today in adjacent seas, with scattered specimens of warmer water species; consequently, the water temperature should have been the same, or just a few degrees higher than at the today adjacent seas. In the Diamante area, marine sedimentation was interrupted, in the lower and middle Paraná Formation, by prograding coastal systems (probably deltaics). To the top of the section, and taking account the richness and abundance of microfossils, the sea level had reached its higher level.

    The foraminiferal and ostracod geographical distribution indicate that the sea entered from the Atlantic through the Salado basin. The hypothesis here proposed argue against the faunal migration through an hypothetic intracontinental seaway connecting the Caribbean sea with the Plata region during TEP deposition, known as the "Arm of Tethys".