Asociaciones de foraminíferos bentónicos en secciones Holocenas del estuario de Bahía Blanca (Buenos Aires, Argentina

CALVO MARCILESE, L; CUSMINSKY , G. C.; GÓMEZ, E

AMEGHINIANA

ASOCIACION PALEONTOLOGICA ARGENTINA

Lugar: Buenos Aires; Año: 2011 p. 210 - 225

0002-7014

Abstract. ASSEMBLAGES OF BENTHIC FORAMINIFERA IN HOLOCENE SECTIONS FROM THE BAHÍA BLANCA ESTUARY (BUENOS AIRES, ARGENTINA). Benthic foraminifera associations from two holocenic sections, Canal Tres Brazas (38º 55´ S-62º 14´ O) and Canal del Medio (38º 49´ S-62º 17´ O), placed in the Bahía Blanca estuary, Buenos Aires province, are described. From the micropaleontological analysis it is shown that both sections represent estuarine environments, from low intertidal to subtidal zones, affected by sea-level variations during the late Holocene. Within the hyaline foraminifera Buccella frigida (Cushman) dominates both sections, mainly associated to Elphidium gunteri Cole and other species of Elphidium. Also present, but in low proportions are Ammonia tepida (Cushman) and Ammonia parkinsoniana (d´Orbigny) with bolivinids as Bolivina striatula Cushman and Bolivina pseudoplicata Heron-Allen & Earland. Among the most conspicuous miliolids are Miliolinella subrotunda (Montagu) and Quinqueloculina seminulum (Lineé). The Canal del Medio profile, dated in about cal. 3700 years B.P. represents a low intertidal to shallow subtidal estuarine environment, where it is possible to observe energy oscillations from the depositional environment attributed to the cyclical action of tides. Characteristics of these deposits indicate that mean sea level was located at a similar position than the present one at 3831-3610 years B.P. The Canal Tres Brazas profile whose base was dated in cal. 1589-1371 years B.P., shows a typical shallow intertidal fauna that gradually passes towards environments with greater continental influence, and without microfosiliferous content.