The Central English Channel troughs: major source-to-sink remnants or giant tidal scours?

• Published in: Marine and petroleum geology 2023-07, Vol.153, p.106303, Article 106303
• Main Authors: Paquet, F., Thinon, I., Dugué, O., Tessier, B., Benabdellouahed, M., Lasseur, E., Briais, J., Couëffé, R., Guennoc, P., Gaullier, V.
• Format: Article
• Language: English
• Subjects: Central English Channel; Neogene; Paleovalleys; Sciences of the Universe; Tidal scours; Troughs
• ISSN: 0264-8172; 1873-4073
• DOI: 10.1016/j.marpetgeo.2023.106303

The Central English Channel troughs correspond to elongated incisions up to 250 m-deep, at several locations at the bottom of this sea corridor. Depending on their location, they are usually interpreted as part of the submerged quaternary paleovalley network or as resulting from megaflood events. Shedding light on these features, their age, and the processes underlying their development is key for understanding their significance in terms of event geology. The interpretation of a dense grid of high-resolution marine seismic data acquired in the Bay of Seine area reveals that the extensive Quaternary paleovalley and trough network commonly as associated to the “Channel River” system is actually subdivided into at least two superimposed and unrelated incised networks. The overlying network corresponds to fluvial incisions developing during low sea-level conditions of Pleistocene time and connects to the present day fluvial network. The underlying network corresponds to the troughs and appears as a complex, deeper, relatively discontinuous and isolated network. This older network shows unexpected local incision depth up to c.350-400 m-deep and complex sedimentary infill involving several sedimentary processes and environments from fluvial to tidal and shallow-marine. We discuss these observations and their implications for understanding the origin, age and development of the troughs all over the English Channel, from the Dangeard Troughs in the Dover Strait to the Hurd Deep at the western end. We also raise questions about the significance of these large incised features in terms of source-to-sink system of northwestern Europe. •Seismic data interpretation shows two incision networks over the English Channel.•The older network corresponds to troughs with incision depth reaching up to 350 m.•The younger network corresponds to the well documented quaternary paleovalleys.•Age and origin of troughs are discussed using possible scenarios and analogs.•We propose that troughs develop as a set of giant tidal scours during Neogene.