CIM4-Vários
Permanent URI for this collection
Browse
Browsing CIM4-Vários by Author "Antón, L."
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- Benthic foraminifera on the Guadiana inner shelf as indicators of rainfall variability and human impacts on the river basinPublication . Mendes, Isabel; Lobo, F. J.; Ferreira, Óscar; Schönfeld, J.; Hanebuth, T.; Lebreiro, S.; Lantzsch, H.; Antón, L.; Reguera, I.Prodeltaic depositional systems can be used as high-resolution archives, since they sensitively record environmental changes occurred during their formation. On the inner shelf off the Guadiana River, northern Gulf of Cádiz, the recent deposition is mainly driven by river discharge, which reflects both climate variability and human-induced processes in the river basin. The purpose of this study is to unravel rainfall variability and human impacts on the river basin, recorded on the Guadiana prodeltaic wedge, over the past decades. A multiproxy study including the analyses of benthic foraminiferal assemblages, grain size and geochemical element distribution (X-ray fluorescence core scanning), constrained in a chronological framework (based on radiocarbon dating and Pb-210), was performed on core GeoB19522. This core was collected in March 2015, during the RV Poseidon cruise POS482 CADISED, on the Guadiana prodeltaic wedge at 13.5 m water depth, which is an area with high sedimentation accumulation rates and consequent detailed temporal resolution. The upper part of the sediment core (from 1.6 m depth to the top) is dominated by the silt-clay fraction (77-99%), occasionally with higher percentages of sand (0.2-23 %). The element ratios and the benthic foraminiferal fauna show significant temporal variations. Some of the identified species can be regarded as successful colonizers (Textularia earlandi, Reophax arctica) and others as opportunistic species linked with river discharges and the limits of productivity (Bolivina ordinaria, Hopkinsina atlantica). These variations point to changes in the environment, promoted by periods of increase or decrease sediment supply to the shelf.
- The record of a high-energy event in a mud entrapment on the inner shelf off the Guadiana riverPublication . Mendes, Isabel; Lobo, F. J.; Schönfeld, J.; Lebreiro, S. L.; Hanebuth, T.; Lantzsch, H.; Reguera, M. I.; Antón, L.; Ferreira, ÓscarRecent environmental changes associated with high-energy events and human impacts were investigated in a mud entrapment confined in the paleo-Guadiana incised valley. Those changes were recorded in a gravity core during the last 2500 years. An erosional event seems to have occurred at ca. 500 cal yr BP but it is not clear how much sediment was removed. This event was followed by an increase in river discharges until ca. 465 cal yr BP while the benthic foraminiferal faunas were dominated by species associated with shallow-water sandy sediments. Upward, sedimentological and benthic foraminiferal variations indicated environmental changes, promoted by variable sediment supplies to the shelf.