Reworked tsunami deposits by bottom currents: Circumstantial evidences from Late Pleistocene to Early Holocene in the Gulf of Cádiz

2016 ◽  
Vol 377 ◽  
pp. 95-109 ◽  
Author(s):  
Y. Takashimizu ◽  
R. Kawamura ◽  
F.J. Rodríguez-Tovar ◽  
J. Dorador ◽  
E. Ducassou ◽  
...  
2021 ◽  
Author(s):  
Johanna Schmidt ◽  
Anna Saupe ◽  
Jassin Petersen ◽  
André Bahr ◽  
Patrick Grunert

<p>Contourites occur where along-slope bottom currents induce large accumulations of sediments in the deep sea (Faugères and Stow, 2008). Distinguishing among contourites and other depositional facies on continental slopes is fundamental for paleoenvironmental reconstructions like bottom current velocities. Nonetheless, reliable and easily applicable diagnostic criteria to properly differentiate between contourites and other coarse-grained and/or graded deep-water deposits such as turbidites are still sparse (e.g., de Castro et al., 2020). The differentiation and interpretation of these deposits is particularly complex in areas where downslope and along-slope sedimentary processes co-occur.</p><p>The SW Iberian Margin represents an ideal natural laboratory to study the complex interaction of downslope and along-slope processes. Persistent bottom current activity of Mediterranean Outflow Water (MOW) since the early Pliocene (García-Gallardo et al., 2017) resulted in the deposition of thick contourite drift bodies in the Gulf of Cádiz (Hernández-Molina et al., 2014). At the same time, downslope transport, channeled through submarine canyons, occurs frequently. Extensive turbidite intervals - intercalated between contouritic layers and often reworked by bottom currents - have been identified in several Pleistocene and Pliocene sediments in this area (Stow et al., 2013).</p><p>The aim of this study is to define diagnostic criteria to differentiate normally graded contourites and turbidites as well as reworked turbidites based on microfaunal analyses. Benthic foraminiferal assemblages along Pleistocene contouritic (~0.5 Ma) and turbiditic (~0.9 Ma, ~1.1 Ma) sequences in the Gulf of Cádiz (IODP Site U1389) are evaluated to test if their faunal composition provides a reliable tool to distinguish these deposits and the underlying sedimentary processes.</p><p> </p><p> </p><p> </p><p>References:</p><p>de Castro, S., Hernández-Molina, F.J., de Weger, W., Jiménez-Espejo, F.J., Rodríguez-Tovar, F.J., Mena, A., Llave, E., Sierro, F.J., 2020. Contourite characterization and its discrimination from other deep‐water deposits in the Gulf of Cadiz contourite depositional system. Sedimentology. https://doi.org/10.1111/sed.12813</p><p>Faugères, J.C., Stow, D.A.V., 2008. Contourite Drifts. Nature, Evolution and Controls. Dev. Sedimentol. 60, 257–288. https://doi.org/10.1016/S0070-4571(08)10014-0</p><p>García-Gallardo, Á., Grunert, P., Voelker, A.H.L., Mendes, I., Piller, W.E., 2017. Re-evaluation of the “elevated epifauna” as indicator of Mediterranean Outflow Water in the Gulf of Cadiz using stable isotopes (δ13C, δ18O). Glob. Planet. Change 155, 78–97. https://doi.org/10.1016/j.gloplacha.2017.06.005</p><p>Hernández-Molina, F.J., Llave, E., Preu, B., Ercilla, G., Fontan, A., Bruno, M., Serra, N., Gomiz, J.J., Brackenridge, R.E., Sierro, F.J., Stow, D.A.V., García, M., Juan, C., Sandoval, N., Arnaiz, A., 2014. Contourite processes associated with the Mediterranean Outfl ow Water after its exit from the Strait of Gibraltar: Global and conceptual implications. Geology 42, 227–230. https://doi.org/10.1130/G35083.1</p><p>Stow, D.A.V., Hernández-Molina, F.J., Llave, E., Bruno, M., García, M., Díaz del Rio, V., Somoza, L., Brackenridge, R.E., 2013. The Cadiz Contourite Channel: Sandy contourites, bedforms and dynamic current interaction. Mar. Geol. 343, 99–114. https://doi.org/10.1016/j.margeo.2013.06.013</p>


2016 ◽  
Vol 378 ◽  
pp. 196-212 ◽  
Author(s):  
Desirée Palomino ◽  
Nieves López-González ◽  
Juan-Tomás Vázquez ◽  
Luis-Miguel Fernández-Salas ◽  
José-Luis Rueda ◽  
...  

2016 ◽  
Vol 378 ◽  
pp. 114-126 ◽  
Author(s):  
T. Vandorpe ◽  
I. Martins ◽  
J. Vitorino ◽  
D. Hebbeln ◽  
M. García ◽  
...  

2020 ◽  
Author(s):  
Christoph Cämmerer ◽  
Mike Frenken ◽  
Piero Bellanova ◽  
Max Chaumet ◽  
Jan Schwarzbauer ◽  
...  

<p>On the 1<sup>st</sup> November AD 1755, the tsunami, triggered by the 8.5 to 9 M<sub>W</sub> 1755 Lisbon earthquake, caused major inundations with sediment transport along the coastline of the Gulf of Cadiz. The study area, Conil de la Frontera (El Palmar de Vejer), located at the Gulf of Cadiz in southwestern Spain, was severely stuck by the AD 1755 Lisbon tsunami. Witness of the destruction and power of the tsunami inundation are the walls of Torre de Castilnovo, close to the study area, which got heavily destroyed. El Palmar de Vejer was chosen as a study area due to the topographical setting, characterized by the flat alluvial flood plain. With these peculiarities, the area presents good preconditions as a sedimentological archive for potential deposits of the AD 1755 tsunami.</p><p>First, geophysical methods were used to identify potential sandy layers attributed to the AD 1755 tsunami. Ground-penetrating radar (270 MHz antenna) was used to systematically scan the ground to a depth of ca. 3 m. The evaluation of these radargrams were taken into account for the selection of GeoSlicer drilling locations. Based on the samples obtained, granulometric analyses were carried out (1) to identify the potential sandy tsunami deposit; (2) to analyze the different sedimentological depositional environments before, during and after the tsunami; (3) to detect tsunami sublayers deriving from different waves within the wave-train of  the AD 1755 Lisbon tsunami, since 3 waves were reported.</p><p>Furthermore, both inorganic and organic geochemical investigations were performed on the samples. With the help of inorganic geochemical analysis of major elements (Si, Sr, Ti, Ca, N, S) as well as elemental ratios can identify a distinction between marine and terrestrial depositional environments and accumulate more information about the deposit facies. By the use of organic geochemistry for the analysis of biomarker, several different natural compounds were detected (e.g., n-alkanes, n-aldehydes). Biomarker results suggest a distinct differentiation between the AD 1755 tsunami deposit and the surrounding background sediment layers above and below. The tsunami deposits contrasts to the post and pre-tsunami layers by different concentrations of biomarkers and deviant occurrence of specific compounds. The n-alkanes are manifesting the difference of marine and terrestrial sources of the different layers. Results of this study analyzing the Iberian sedimentary archives at Conil de la Frontera present strong evidence that a multi-proxy approach with the inclusion of geochemical applications can confidently detect tsunami deposits, distinguish them from surrounding background sediments and subsequently characterize the internal structure and composition of the tsunami deposit.</p>


2016 ◽  
Author(s):  
Mary Lee King ◽  
◽  
Till J.J. Hanebuth ◽  
Francisco Lobo ◽  
Hendrik Lantzsch ◽  
...  

2021 ◽  
Vol 41 (3) ◽  
Author(s):  
Dolores Jiménez-López ◽  
Ana Sierra ◽  
Teodora Ortega ◽  
Sandra Manzano-Medina ◽  
M. Carmen Fernández-Puga ◽  
...  

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