Submerged Marine Terraces Identification and an Approach for Numerical Modeling the Sequence Formation in the Bay of Biscay (Northeastern Iberian Peninsula)

Abstract

Submerged sequences of marine terraces potentially provide crucial information of past sea-level positions. However, the distribution and characteristics of drowned marine terrace sequences are poorly known at a global scale. Using bathymetric data and novel mapping and modeling techniques, we studied a submerged sequence of marine terraces in the Bay of Biscay with the objective to identify the distribution and morphologies of submerged marine terraces and the timing and conditions that allowed their formation and preservation. To accomplish the objectives a highresolution bathymetry (5 m) was analyzed using Geographic Information Systems and TerraceM R . The successive submerged terraces were identified using a Surface Classification Model, which linearly combines the slope and the roughness of the surface to extract fossil sea-cliffs and fossil rocky shore platforms. For that purpose, contour and hillshaded maps were also analyzed. Then, shoreline angles, a geomorphic marker located at the intersection between the fossil sea-cliff and platform, were mapped analyzing swath profiles perpendicular to the isobaths. Most of the submerged strandlines are irregularly preserved throughout the continental shelf. In summary, 12 submerged terraces with their shoreline angles between approximately: −13 m (T1), −30 and −32 m (T2), −34 and 41 m (T3), −44 and −47 m (T4), −49 and 53 m (T5), −55 and 58 m (T6), −59 and 62 m (T7), −65 and 67 m (T8), −68 and 70 m (T9), −74 and −77 m (T10), −83 and −86 m (T11) and −89 and 92 m (T12).Nevertheless, the ones showing the best lateral continuity and preservation in the central part of the shelf are T3, T4, T5, T7, T8, and T10. The age of the terraces has been estimated using a landscape evolution model. To simulate the formation and preservation of submerged terraces three different scenarios: (i) 20-0 ka; (ii) 128-0 ka; and (iii) 128-20 ka, were compared. The best scenario for terrace generation was between 128 and 20 Ka, where T3, T5, and T7 could have been formed.

The intrusive nature of the Châtelperronian in the Iberian Peninsula

“…During Marine Isotope Stage (MIS) 3, sea level was 60–70 m lower than today, with the coastline ca. 4 km further offshore according to recently obtained bathymetric surveys [ 17 ]. The site is located in an old sand quarry complex (Ollagorta-Aranbaltza) that exploited Pleistocene fluvial sand deposits overlaying Upper Cretaceous bedrock (marine marls and limestone alternating with intercalated volcanic layers) (Section SI-3 in S1 File ).…”

Terraced Landforms Onshore and Offshore the Cilento Promontory (South-Eastern Tyrrhenian Margin) and Their Significance as Quaternary Records of Sea Level Changes

“…With time, uplift determines the formation of terraced coastlines, often with a step-like profile, where older terraces are higher and farther from today's coastline [7]. In this work, we focused on understanding the occurrence of paleo, wave-cut shore platforms (forming marine terraces) within the submarine domain [22]. Here, it is important to note that phases of relatively high sea-level or stationary phases during transgressive periods, in the end, determine the most favorable condition for wave-cut shore platform formations on rocky cliffs (because they cause marine processes to prevail over sub-aerial processes).…”

“…A higher resolution of the DEM would also lead to a more effective morphometric analysis. The more accurate list of terraced surfaces that would result from the analysis, combined with an adequate reconstruction of late Quaternary environmental conditions that controlled formation of wave-cut shore platforms (e.g., wave climatology, as performed in [22]), would provide more precise information to confirm the ascription of the terraces to a defined high-stand period.…”

“…The geomorphological significance of submerged terraced landforms [9][10][11][12][13][14], as evidence of Quaternary sea-level variations, has been less investigated and has only recently gained attention [15], thanks to advances in seafloor mapping techniques [16] and the resulting recognition of Submarine Depositional Terraces (SDT) (defined as sedimentary bodies with a clinostratified internal structure and a prograding growth towards the sea [17][18][19][20][21]). Minor studies have investigated the possible erosive nature of submerged terraced landforms formed on bedrock outcropping on the shelf and their relationship to sea-level oscillations, among them Bilbao-Lasa et al [22]. Additionally, by taking into account both emerged and submerged terraces, a few investigations have integrated their findings to support an improved understanding of the tectono-geomorphological evolution of coastal areas and the physiography of the margin [15,23], as we have undertaken in our work for the Cilento Promontory.…”

Geomorphometric analysis of the natural and anthropogenic seascape of Naples (Italy): A high‐resolution morpho‐bathymetric survey

“…High-coast sectors are the result of prevailing landward retreat which leads to the formation of erosional geomorphological features as shore platforms or tidal notches that can be used to detect past relative sea level (RSL) variations (Bilbao et al, 2020;Duguet et al, 2021;Rovere et al, 2016). In particular, shore platforms are sub-planar surfaces dipping seaward and limited landward by the sea-cliffs (Bilbao et al, 2020). The inner margins of palaeoshore platforms are directly related to the ancient RSL and their formation is favoured by the wave action, often exacerbated by bio-erosion and weathering (Bird, 2000;Pappalardo et al, 2016;Sunamura, 1992;Trenhaile, 1987Trenhaile, , 2011.…”