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Closed Access item Late Pleistocene and Holocene geochemical record of the most recent turbidite lobe of the Almeria Fan (Alboran Sea)
Vázquez, J. T.
|Keywords:||Alboran Sea, turbidite lobe, sediment source, climatic events|
|Abstract:||Geochemical element abundances were analyzed with AVAATECH XRF core scanner on two piston cores recovered from the most recent turbidite lobe of the Almeria Fan (Alboran Sea). Core-Sagas 1 locates on the outer part of the lobe at 1759 m water depth and core-Sagas 2 locates in the lobe channel at 1762 m water depth. Statistical analyses (PCA and cluster) of 14 geochemical elements were performed and terrigenous proxies (Ti/Al, Rb/Al, Zr/Al and Si/Si+K ratios and Pb) were studied.
From bottom to top the cores are composed by two main sedimentary sequences: hemipelagite muds and coarse-grained turbidites. The hemipelagite sequence is chemically similar in both cores. The vertical distribution of terrigenous proxies allows discriminating the fluvial and eolian contributions. The Ti/Al, Rb/Al, Zr/Al ratios display vertically parallel profiles following the same tendencies and their low values indicate river inputs. The Si/Si+K index shows opposite trends to the previous ones and their high values indicate eolian input. The vertical distribution of Pb displays in a few samples high values within the upper part of the hemipelagite sequence. On the turbidite sequence, three major compositional types of turbidites have been identified. Type 1, rich in S, Cl and Br, correspond to organic-matter rich turbidites; type 2, rich in Ca and Sr, represents biogenic clastic turbidites, and type 3, rich in Si, Ti, Zr and Rb, relates to terrigenous clastic turbidites.
The lobe channel (core 2) shows numerous centimetric-thick sand deposits with sharp or erosive basal contacts (turbidites types 2 and 3). The channel was built by successive turbidite events depositing sands. In contrast, the outer part of the lobe (core 1) contains a metric-thick massive fine sand deposit (turbidite type 3). This unit is covered by a centimetric-thick medium massive sands (tubidite type 2). The outer part of the lobe is mainly built by two turbidite events related to crevasse-splay and/or from spillower processes. On other hand, some detrital components in the turbidites provide information about the source rocks and provenance since they are unaffected by early diagenesis. Thus, the abundance of Ti, Zr, Rb in the type 3 could be related to volcanism at the vicinity area. The different nature and composition of the drainage basin of the Andarax River and ground drainage water could control the Ca-Sr and S-Cl-Br assemblages.
The late Pleistocene-Holocene geochemical records provide information about different sediment inputs to the Almeria margin: i) eolian and fluvial suggested by fluctuations of terrigenous contributions from the hemipelagites; ii) anthropogenic suggested by the presence of Pb anomalies within the hemipelagites that could be related to mining activities in the Almeria region; and iii) fluvial and volcanic suggested by the biogenic and terrigenous compositions of turbidite sediments related to weathering of the different rocks present in the drainage systems.|
|Description:||IAS Meeting Meeting Sedimentology, Zaragoza 2011. Abstract Book, pp. 277|
|Appears in Collections:||(ICM) Comunicaciones congresos|
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