Episodic postglacial deltaic pulses in the Gulf of Cadiz: Implications for the development of a transgressive shelf and driving environmental conditions

• Published in: Journal of Sedimentary Research
• Main Authors: Carrión-Torrente, Álvaro, Lobo, Francisco José, Puga-Bernabéu, Ángel, Mendes, Isabel, Martín Lebreiro, Susana, García, Marga, van Rooij, David, Luján, María, Reguera, María Isabel, Antón, Laura
• Format: Article in Journal/Newspaper
• Language: English
• Published: SEPM (Society for Sedimentary Geology) 2022
• Subjects: Atlantic Ocean; Cenozoic; clastic sediments; deltaic environment; fine-grained materials; Gulf of Cadiz; Holocene; last glacial maximum; marine environment; North Atlantic; paleoenvironment; Pleistocene; Quaternary; sand; sea-level changes; sediments; shelf environment; terrigenous materials; transgression upper; Guadiana River
• Online Access: http://hdl.handle.net/10261/341357; https://doi.org/10.2110/jsr.2021.110; https://api.elsevier.com/content/abstract/scopus_id/85149222613

The postglacial sea-level rise after the Last Glacial Maximum provided ideal conditions to study the transgressive sedimentary response to sudden shelf flooding driven by different rates of sea-level rise. In this study, a high-resolution seismic stratigraphic interpretation and sedimentological analysis were conducted on data from the northern Gulf of Cadiz continental shelf (SW Iberian Peninsula), in order to: 1) understand the succession of sedimentary processes during each shelf flooding episode and 2) explore the significance of variable rates of sea-level rise, sediment fluxes, and climatic conditions on the development of postglacial deposits. Four backstepping seismic postglacial transgressive units (PTUs; 4 to 1 from oldest to youngest) that are linked to the retreating mouth of the Guadiana River were interpreted. Together, these seismic units display a wedge-shape geometry, are located over the inner to middle shelf, and overlie a regional unconformity formed during the Last Glacial Maximum. Each PTU can be divided into several sub-units with distinctive seismic facies that have a similar stratigraphic organization. Each PTU contains lower sub-units that are composed of low-angle tangential-oblique clinoforms. The clinoforms are locally topped by a channelized sub-unit. The distal and/or lateral parts of the clinoforms are occasionally buried by sheet-like semitransparent subunits. The uppermost sub-units are present over the proximal and central parts of each seismic unit and are also sheet-like. PTUs can also be subdivided and described sedimentologically. Fine-grained sands with intercalated silty layers dominate the lower part of each PTU (lower clinoform sub-units). The upper part of each PTU (upper sheet-like sub-units) is characterized by reworked facies, composed of highly fragmented bioclasts within a mixture of silt and coarse to medium sand. Finally, mud deposits occur as a sediment drape over the PTUs. The internal structure of each PTU reveals several phases of development under a general ...