Sedimentación y pedogénesis cuaternaria en el noreste de la pampa bonaerense: la localidad Gorina como caso de estudio

the gorina locality is representative of the quaternary sedimentary record of the northeastern pampas of buenos aires province. the main goals of this contribution are to analyze the composition (grain-size and mineralogy) of the deposits and discuss their nature and provenance. the general balance and interaction of the sedimentation process with pedogenesis and erosion are also evaluated. the studied section (middle to late pleistocene and holocene) is a quarry exposure about 11 meters thick. it was sampled at approximately 25 cm intervals for grain size, mineralogical and micromorphological analyses. the micromorphological results are fully discussed in a separate contribution (zárate et al., 2000). pedological features are common throughout the succession. thus, a combined macromorphological and micromorphological approach was used to identify and differentiate paleosols. five pedological units (from top to bottom pu1, pu2, pu3, pu4, pu5), apparently representing four discrete paleosols plus the surface soil, were initially differentiated on the basis of field-scale morphological properties (i.e., color, texture, structure, consistency, boundaries) following the approach applied by other authors in the region. micromorphologically, the presence of excremental fabrics throughout the vertical column suggests that bioturbation processes were active as the sediment accreted with buildup of the surface resulting in conversion of a into b and c horizons (zárate et al., 2000). the micromorphological data do not support the field differentiation of pu4, pu3, and pu2. pedological features (e.g. excrements, secondary carbonate coatings, illuvial clay coatings) occur throughout without any obvious breaks or patterns that might warrant the separation into discrete paleosols. this ca. 8 m sequence is interpreted as an accretionary and/or welded pedocomplex with superimposition of secondary carbonate on illuvial clay features and illuvial clay coatings on excrements as the su