“…9). This hiatus coincides with the time range where an increase in the strength of the bottom current is documented in the Galician Continental Margin related to the strengthening of the Mediterranean Outflow Water (MOW) (Petrovic et al 2019). Therefore, the hiatus of the core GC16 indicates an increase in the strength of the bottom current that causes erosion of the sediments (López-Pérez et al 2021a), and thus the exhumation of the FTB.…”
Section: Sedimentological Significance Of the Facies Classification For The Formation And Distribution Of The Ftbsupporting
confidence: 58%
“…The study of the most surficial sedimentary cover of the margin revealed the palaeoclimatic and palaeoenvironmental interest of this area to understand in detail the climatic, environmental and oceanographic changes during the Late Pleistocene and Holocene at these latitudes (e.g. Alonso et al 2008;Rey et al 2008;Bender et al 2012;Martins et al 2013Martins et al , 2015Hanebuth et al 2015;Plaza-Morlote et al 2017;Mena et al 2018;Petrovic et al 2019;López-Pérez et al 2019, 2021a.…”
Surficial sediments on the seafloor from passive continental margins can provide insight into recent Late Quaternary sedimentary dynamics acting over offshore sedimentary systems. This work focuses on the study of some particular ferruginous tubular structures resembling bioforms (FTB) located in the distal Galician Continental Margin (NW Iberian Margin) at water depths between ~ 1550 and ~ 2200 m. The characterisation of these structures made it possible to study in depth their formation environment and subsequent sedimentary evolution during the Late Pleistocene and Holocene. The FTB consist of goethite with a framboidal texture. They were interpreted as formed by an initial pyrite precipitation in reducing microenvironments conditioned by the activity of sediment-dwelling organisms during the early diagenesis. This is followed by the oxidation of pyrite by a combination of hydrothermal fluids and erosional processes, which triggers the formation of the framboidal oxyhydroxides. The data allowed obtaining a comprehensive understanding of the environmental context and the significance of these ferruginous tubules, as there are no previous studies in the scientific literature that describe these structures in a source-to-sink sedimentary system.
“…9). This hiatus coincides with the time range where an increase in the strength of the bottom current is documented in the Galician Continental Margin related to the strengthening of the Mediterranean Outflow Water (MOW) (Petrovic et al 2019). Therefore, the hiatus of the core GC16 indicates an increase in the strength of the bottom current that causes erosion of the sediments (López-Pérez et al 2021a), and thus the exhumation of the FTB.…”
Section: Sedimentological Significance Of the Facies Classification For The Formation And Distribution Of The Ftbsupporting
confidence: 58%
“…The study of the most surficial sedimentary cover of the margin revealed the palaeoclimatic and palaeoenvironmental interest of this area to understand in detail the climatic, environmental and oceanographic changes during the Late Pleistocene and Holocene at these latitudes (e.g. Alonso et al 2008;Rey et al 2008;Bender et al 2012;Martins et al 2013Martins et al , 2015Hanebuth et al 2015;Plaza-Morlote et al 2017;Mena et al 2018;Petrovic et al 2019;López-Pérez et al 2019, 2021a.…”
Surficial sediments on the seafloor from passive continental margins can provide insight into recent Late Quaternary sedimentary dynamics acting over offshore sedimentary systems. This work focuses on the study of some particular ferruginous tubular structures resembling bioforms (FTB) located in the distal Galician Continental Margin (NW Iberian Margin) at water depths between ~ 1550 and ~ 2200 m. The characterisation of these structures made it possible to study in depth their formation environment and subsequent sedimentary evolution during the Late Pleistocene and Holocene. The FTB consist of goethite with a framboidal texture. They were interpreted as formed by an initial pyrite precipitation in reducing microenvironments conditioned by the activity of sediment-dwelling organisms during the early diagenesis. This is followed by the oxidation of pyrite by a combination of hydrothermal fluids and erosional processes, which triggers the formation of the framboidal oxyhydroxides. The data allowed obtaining a comprehensive understanding of the environmental context and the significance of these ferruginous tubules, as there are no previous studies in the scientific literature that describe these structures in a source-to-sink sedimentary system.
“…This is due to the fact that climatic variability has an impact on palaeoceanographic and sedimentary conditions (e.g. Voelker et al ., 2006; Eynaud et al ., 2009; Voelker & de Abreu, 2011; Plaza‐Morlote et al ., 2017; Petrovic et al ., 2019) which also affects marine primary production and early diagenetic processes (e.g. Rey et al ., 2008; Salgueiro et al ., 2010, 2014; Andrade et al ., 2011; Martins et al ., 2018).…”
Section: Introductionmentioning
confidence: 99%
“…Numerous studies focused on magnetochemical and biological (microfossils) proxies demonstrated signatures of abrupt millennial climatic variability registered in the sediments of the Galician continental margin, providing valuable palaeoclimatic, palaeoceanographic and palaeoenvironmental information for the Late Pleistocene and Holocene epochs (e.g. Lantzsch et al ., 2009; Mohamed et al ., 2010; Salgueiro et al ., 2010, 2014; Andrade et al ., 2011, 2014; Voelker & de Abreu, 2011; Bender et al ., 2012; Hanebuth et al ., 2015; Martins et al ., 2015, 2018; Plaza‐Morlote et al ., 2017; Mena et al ., 2018; Petrovic et al ., 2019). A specific millennial climate oscillation signature is the recognition of ice‐rafted debris (IRD) within the sediment of this margin during the Last Glacial Period (LGP) (Alonso et al ., 2008; Rey et al ., 2008; Martins et al ., 2013; Plaza‐Morlote et al ., 2017; Mena et al ., 2018; López‐Pérez et al ., 2019).…”
Deep-sea sediments record palaeoenvironmental and oceanographic changes over time through variations in their magnetochemical and sedimentological properties. This study presents the Late Quaternary sedimentary reconstruction of three sediment cores extracted from a source-to-sink sedimentary system located in a high marginal platform of the north-west Iberian Margin. The aim of this reconstruction is to explore the palaeoclimatic, palaeoproductivity and diagenetic changes over the last 172 cal ka BP attending to geochemical, magnetic and sedimentological variations. The record is comprised of four sedimentary units consisting of pelagic, hemipelagic and detrital facies, the latter associated with ice-rafted debris events at Heinrich Stadials. These findings allowed the reconstruction of the lithostratigraphy attending to climatic changes, covering the last eleven Heinrich Stadials. These units and facies successions are controlled by the superposition of the Milankovitch and Dansgaard-Oeschger cycles. Low sedimentation rates have been reported, especially during cold periods. Palaeoproductivity was assessed using total organic carbon and calcium carbonate content, together with biogenic barium (Ba bio ) and organic phosphorus (P org ), both calculated via total digestion analysis using standard calculations. Mass accumulation rates for total organic carbon, Ba bio and P org were calculated. Furthermore, a sequential extraction was performed to explore the different phases of the barium within sediments: biogenic barite (Ba bar ), barium associated with iron and manganese oxides (Ba ox ) and Ba associated with aluminosilicates (Ba det ). Results display a limitation in the use of the biogenic barium and phosphorus and mass accumulation rates, suggesting detrital Ba (Ba detr ) contribution during Heinrich Stadials, which could mask the calculations. In contrast, only calcium carbonate fluctuates attending to glacial/interglacial cycles. Regarding some diagenetic proxies (i.e. Mn, Mn/Fe and Mn/Ti), they reveal oxidation fronts of different generations, suggesting that the early diagenesis has not reached steady-state, because the redoxcline fluctuates. This fact suggests an erosional activity that causes the continuous oxygenation of the sediment and non-steady-state conditions.
“…The location is known to be affected by northward bottom currents that interact with bathymetry to generate a contouritic drift along the basin. This setting provides a detailed record of Quaternary contourite deposits 13–16 . Contouritic facies appear as massive to coarsely laminated silt to very fine silty sand and, show varying degrees of bioturbation 17 .Figure 1Location of cores analysed in this study.…”
Although bioturbation is commonly recognized in contourites, only a few studies have analyzed the ichnological content of these deposits in detail. These studies have mainly focused on meso-scale bigradational sequence (a coarsening upward followed by a fining-upward sequence resulting from variations in current velocity). Here we present data from gravitational cores collected along the NW Iberian Margin showing systematic variation in ichnological content across proximal to distal depocenters within a large-scale elongated contourite drift. Data demonstrate that tracemakers’ behavior varies depending on the distance relative to the bottom current core. Trace fossils are already known to be a useful tool for studying of contouritic deposits and are even used as criterion for differentiating associated facies (e.g., turbidites, debrites), though not without controversy. We propose a mechanism by which the distance to the bottom current core exerts tangible influence on specific macro-benthic tracemaker communities in contourite deposits. This parameter itself reflects other bottom current features, such as hydrodynamic energy, grain size, nutrient transport, etc. Ichnological analysis can thus resolve cryptic features of contourite drift depositional settings.
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