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Variations in benthic foraminiferal assemblages in the Tagus mud belt during the last 5700 years: Implications for Tagus River discharge
- Source :
- Palaeogeography Palaeoclimatology Palaeoecology, Palaeogeography, Palaeoclimatology, Palaeoecology, Palaeogeography, Palaeoclimatology, Palaeoecology, Elsevier, 2018, 496, pp.225-237. ⟨10.1016/j.palaeo.2018.01.040⟩, Palaeogeography, Palaeoclimatology, Palaeoecology, 496, 225. Elsevier Saunders, Palaeogeography, Palaeoclimatology, Palaeoecology, 2018, 496, pp.225-237. ⟨10.1016/j.palaeo.2018.01.040⟩
- Publication Year :
- 2018
-
Abstract
- Accepted manuscript version. Published version available at https://doi.org/10.1016/j.palaeo.2018.01.040. Accepted manuscript version, licensed CC BY-NC-ND 4.0. We analyzed a 10-m sediment core retrieved at 82 m water depth off the coast of the Tagus River (Western Iberian Margin, Portugal) to investigate a linkage between variations in benthic foraminiferal assemblages and Tagus River discharge over the last 5700 years. Benthic foraminiferal assemblages were studied at high resolution in combination with the stable carbon and oxygen isotopic composition of fossil shells of Nonion scaphum, bulk and molecular organic matter properties (TOC, TN, C/N ratio, δ13CTOC, δ15Nbulk, and BIT index), magnetic susceptibility, and XRF analyses. Three periods of environmental changes were identified: 1) high Tagus River discharge in 5750–2200 calendar year before present (cal yr BP), 2) lower discharge characterized by intense upwelling conditions (2250–1250 cal yr BP), and 3) both intense upwelling and Tagus River discharge (1250 cal yr BP-present). The data reveal alternating intense upwelling periods, as shown by the dominance of Cassidulina carinata, Valvulineria bradyana, or Bulimina marginata, whereas periods of increased river discharge are indicated by increase of N. scaphum, Ammonia beccarii, and Planorbulina mediterranensis. The Tagus River discharge was the strongest during the first period, transporting riverine material further offshore and preventing the establishment of a mud belt on the mid-shelf (around 100 m depth). During the second period, a decrease in Tagus River discharge favored the formation of the Tagus mud belt and strongly influenced the benthic environment by creating an organic matter stock. During the third period, intense upwelling and increased Tagus River discharge were recorded by benthic foraminiferal distribution, with an increase of terrestrial elements present in the mud belt. Furthermore, our results showed that variations in benthic foraminiferal assemblages corresponded to the well-known climatic periods in the study area, such as the Roman Period, the Dark Ages, the Medieval Warm Period, and the Little Ice Age. Our study strongly suggests that benthic foraminiferal assemblages can be used as a bio-indicator to trace the influence of past river discharge.
- Subjects :
- 010506 paleontology
010504 meteorology & atmospheric sciences
Evolution
[SDE.MCG]Environmental Sciences/Global Changes
[SDU.STU]Sciences of the Universe [physics]/Earth Sciences
Oceanography
01 natural sciences
Behavior and Systematics
VDP::Matematikk og Naturvitenskap: 400::Geofag: 450
14. Life underwater
Holocene
Ecology, Evolution, Behavior and Systematics
0105 earth and related environmental sciences
Earth-Surface Processes
VDP::Mathematics and natural science: 400::Geosciences: 450
Ecology
Discharge
Palaeontology
ACL
Foundation (engineering)
Paleontology
Paleo-reconstruction
15. Life on land
Portuguese Margin
13. Climate action
Benthic zone
North Atlantic oscillation
North Atlantic Oscillation
Geology
Subjects
Details
- ISSN :
- 00310182
- Database :
- OpenAIRE
- Journal :
- Palaeogeography Palaeoclimatology Palaeoecology, Palaeogeography, Palaeoclimatology, Palaeoecology, Palaeogeography, Palaeoclimatology, Palaeoecology, Elsevier, 2018, 496, pp.225-237. ⟨10.1016/j.palaeo.2018.01.040⟩, Palaeogeography, Palaeoclimatology, Palaeoecology, 496, 225. Elsevier Saunders, Palaeogeography, Palaeoclimatology, Palaeoecology, 2018, 496, pp.225-237. ⟨10.1016/j.palaeo.2018.01.040⟩
- Accession number :
- edsair.doi.dedup.....c91fce9e6dd0e3cf9138292b7192cb7b