The synthetic seismic expression of the Messinian salinity crisis from onshore records: Implications for shallow‐ to deep‐water correlations

Abstract

The onshore–offshore correlation of sedimentary successions is a common problem in basin analysis, but it becomes critical for the full understanding of the Messinian salinity crisis (MSC), a complex array of palaeoenvironmental events which affected the Mediterranean basin at the end of the Miocene. The outcrop records show that the Messinian stratigraphic architectures may be highly complex as the deposits of the different MSC evolutionary stages can be lithologically similar and separated by erosional surfaces and/or morphostructural highs. The correct definition of the nature and stratigraphic position of Messinian deposits in offshore areas through seismic data may be almost impossible, especially where core data are sparse. To bridge the gap between onshore and offshore records, we have built synthetic seismic sections from well‐constrained outcrop successions. Our results provide useful insights and warnings for the interpretation of offshore data, pointing out that MSC units having different age, nature and depositional settings, may show similar seismic facies and geometries. Conversely, the same deposit may result in different seismic facies, either with parallel and high‐amplitude reflections or even transparent or chaotic due to interference patterns of seismic reflections related to dominant frequency. It follows that a correct interpretation of the nature and age of deep‐seated Messinian deposits can only be obtained through the integration of seismic and core data, and considering the onshore record. The application of our approach to the Balearic Promontory results in an alternative interpretation with respect to previous models. We show that this offshore area has good analogues in the onshore of the Betic Cordillera and includes both shallow and intermediate depth sub‐basins that underwent a strong post‐Messinian subsidence.

Tectonic Inversion and Geomorphic Evolution of the Algerian Margin Since Messinian Times: Insights From New Onshore/Offshore Analog Modeling Experiments

“…For the experiment, we have imposed a 3.5 cm high and 12 mn long water drawdown to simulate a 1,500 m high sea‐level fall which is assumed to have lasted about 150 Kyr in Nature. Although these values may change according to the scenarios chosen, they are, to first order, in agreement with drawdown amplitude and duration generally assumed for the MSC and represent here upper bounds (CIESM, 2008; Clauzon et al., 1996, 2015; Gautier et al., 1994; Lofi, Déverchère, et al., 2011; Lofi, Sage, et al., 2011; Roveri et al., 2019; Ryan, 2011).…”

“…Stages refer to the time periods of the MSC proposed by Roveri et al. (2019) by onshore–offshore correlation of sedimentary successions. Bottom: for comparison, time seismic section interpreted off the central Algerian margin (location on Figure 2), modified from Lofi, Sage, et al.…”

“…As in the case of land rivers, the evolution of deltas is closely related to the relative sea (Lofi, Sage, et al, 2011); 3: microbeads manually deposited at the end of the sea-level drawdown, aiming at reproducing the halite deposition (MU) at the beginning of Stage 2 of the MSC; 4: well-sorted deltaic formation deposited during the sea-level low-stand, at the end of the MSC (Stage 3), featuring the last part of CU and at least part of the high-amplitude Upper Unit UU identified in the deep offshore of the Western Mediterranean Sea (Lofi, Déverchère, et al, 2011;Lofi, Sage, et al, 2011). Stages refer to the time periods of the MSC proposed by Roveri et al (2019) by onshore-offshore correlation of sedimentary successions. Bottom: for comparison, time seismic section interpreted off the central Algerian margin (location on Figure 2), modified from Lofi, Sage, et al (2011), showing that the angular relationships between sedimentary units are similar to the model, although the salt layer MU underwent significant diapirism and the late tectonic inversion has induced post-deposition folding and faulting.…”

“…They display an architecture similar to that of Gilbert‐type deltas resulting either from fluvial or from wave‐action dynamics (Clauzon et al., 1996; Duvail et al., 2005; Rubino et al., 2005). Although a final stratigraphic scenario is still not fully established and important controversial points remain, a chrono‐stratigraphic model with three main evolutionary stages of the MSC in a time span covering approximately 600 Kyr (CIESM, 2008; Clauzon et al., 2015; Roveri et al., 2019) is widely used and promoted in the international community and matches the available geological and geophysical data. Therefore, although we acknowledge that other hypotheses may exist and could be explored, we have adopted the following simple steps and timing to build the MSC scenario of our experiment: 1 [6.0–5.6 Ma]: formation of marginal basins with minor sea‐level fall; 2 [5.6–5.5 Ma]: significant subaerial erosion and sea‐level drawdown; and 3 [5.5–5.4 Ma]: sea‐level rise and fast reflooding.…”

New onshore/offshore evidence of the Messinian Erosion Surface from key areas: The Ibiza-Balearic Promontory and the Orosei-Eastern Sardinian margin

“…To conclude, during the MSC, both areas were moreover in post-tectonic context: post Betic compression for Ibiza and post-Tyrrhenian rifting for the Sardinia Eastern margin. Tectonic deformation exists locally but is regionally weak during the Late Miocene/Pliocene and, unlike proposed explanations (Roveri et al, 2019), vertical movements (uplift/subsidence) are not the main trigger mechanism, at least at large scale, to explain the present-day different depth of the MSC deposits. Nevertheless, isostatic rebound must be taken into account in the MSC scenario (as shown in Rabineau et al, 2014) and vertical movements will be carefully studied in the integrated project SALTGIANT -Understanding the Mediterranean Salt Giant [Marie Sklodowska-Curie Actions -Innovative Training Networks (ITN)].…”