SciELO - Scientific Electronic Library Online

vol.9 número1Facies y geometrías de los depósitos aluviales cuaternarios en la quebrada del Portezuelo, Sierra de Mojotoro, provincia de Salta, ArgentinaAsociaciones de facies y correlación de las sedimentitas de la Formación Chenque (Oligoceno-Mioceno) en los alrededores de Comodoro Rivadavia, Cuenca del Golfo San Jorge, Argentina índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Servicios Personalizados




  • No hay articulos citadosCitado por SciELO

Links relacionados

  • No hay articulos similaresSimilares en SciELO


Revista de la Asociación Argentina de Sedimentología

versión impresa ISSN 1853-6360


IANTANOS, Nerina; ESTRADA, Enrique  y  ISLA, Federico. Tidal forms of the Ría del Deseado, Santa Cruz. Rev. Asoc. Argent. Sedimentol. [online]. 2002, vol.9, n.1, pp.43-52. ISSN 1853-6360.

Patagonian rivers flow across desert lands and between two plateaux of Mesozoic, Tertiary and Quaternary rocks. The original wide valleys were reduced by the deposition of terminal moraines which blocked some Atlantic watersheds at the headlands and were responsible for the changes in the outflow of the rivers. Strong westerly winds increase the evaporation. Those rivers that arrived to the Atlantic coast are subject to the action of large tidal ranges that contribute to change their inlets twice a day moving towards the headlands along manykilometers. These estuaries are called "rías" in the partial sense, and worlwide used, equivalent to "drowned river valleys" from Von Richtoffen, but where a structural control should not be discarded, as stated originaly for the "Rías Baixas" of Galicia. Patagonian rías have particular characteristics: river outflows and valley capacities diminished, and a Holocene sea-level fluctuation that affected the morphosedimentary evolution of the estuaries. The Deseado River estuary has a funnel shape oriented towards the northeast and changing to an eastward direction at the inlet. The river has excavated this inlet into piroclastic rocks of Jurassic age. Gorges and small canyons are indicating erosion features that cannot be justified by present-day processes. A sediment sampling was carried out at this estuary in order to recognize present sediment dynamics previous to any alteration induced by mariculture activity or harbour enviroments. At the inner estuary, extended tidal flats, marshes and tidal channels were recognized. Tidal-sand banks conforming a flood delta and elevated beaches (with shell middens on top) characterize the middle portion of the estuary. Salinity measurements and morphologic analysis indicate that the tidal excursion extends about 40 km. into the estuary. Non-operating tidal flats were recognized at the bottom of some canyons. The Cañadón del Puerto is a relict tidal flat originated by changes in the river dynamics or to the Mid-Holocene sea-level drop. Towards the estuary mouth, Puerto Deseado is emplaced on Pleistocene beach systems, composed mainly by gravel, and the ignimbrites, riolites and tuffs of the piroclastic Jurassic complex. Towards the headlands, at Paso Gregores, the river is recognized in an anastomosing design, with little freshwater flowing between bars composed of gravel and sand. Four different zones were discriminated along the ria with different kind of bottomcomposition, dynamics and salinity regime. The Outer Marine zone is characterized by the action of waves with tidal banks composed of medium to fine sands with shells, constituting a dissected flood-tidal delta. At the Estuarine Zone muds dominate over sands, but salinity is still indicating marine waters. At the Zone of Water Mixing, silts and clay dominate. The presence of non-operative tidal flats on the bottom of small canyons (cañadon del Puerto) is a relict feature indicating changes in the fluvial or tidal regimes, possibly associated to the sea-level regression of the last 5000 years.

Palabras clave : Estuary; Tidal flat; Deseado estuary.

        · resumen en Español     · texto en Español     · Español ( pdf )


Creative Commons License Todo el contenido de esta revista, excepto dónde está identificado, está bajo una Licencia Creative Commons