Variación de las tasas de sedimentación en el Complejo Detrítico Superior del Delta del Llobregat (Barcelona): su relación con causas eustáticas, climáticas y antrópicas

Sediment accumulation rates have been calculated for the Llobregat Delta and compared to eustasy, climate and land use. Radiometric ages show slow (less than 1 mm/yr) sediment accumulations between 12180±60 BP (14565±715 cal BP) and ~4100 BP (4500 cal BP) and faster rates (12 to 25 mm/yr) younger than ~4100 BP (4500 cal BP). Within this trend of increasing sediment accumulation rates are two peaks of high sediment accumulation; one occurring during the Visigoth period (VI-VIII century) to Upper Medieval Age (X-XIV century) and the second during the economic recuperation (XVIII century). The initial slow sediment accumulation rate is attributed to high rates of accommodation produced by the rapid Holocene transgression and little sediment supply. Following a slower rate of creation of accommodation space, sediment started to accumulate at the mouth of the river and prograde on the shallow shelf. The pulses in sediment accumulation coincide with and are interpreted to increasing pressure anthropomorphic activity together with peaks of aridity

Arquitectura de facies de los deltas cuaternarios del río Llobregat, Barcelona, España

The Llobregat River has accumulated multiple deltas through Quaternary eustatic cycles. The rapid rises and step-wise, relatively slower falls in sea level have produced a bias towards preserving forced regressive system tracks and eroding the high-stand system tracks with the exception of the Holocene delta. Subsurface data indicates that the Quaternary deltas were feed by the Llobregat river and «rieras» derived from Garraf and Collserola, but the sediment was probably redistributed by long-shore currents to form a unique delta front. The Holocene Llobregat River high-stand delta progrades over older fluvial, flood-plain and shoreline deposits equivalent to the older deltas now preserved at the continental margin. A number of paleo-flow channels feeding the older Quaternary deltas illustrate the complexity for the exploitation and protection of groundwater found in these deposits