Erosion of continental margins in the Western Mediterranean due to sea-level stagnancy during the Messinian Salinity Crisis |
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Authors: | Janna Just Christian H??bscher Christian Betzler Thomas L??dmann Klaus Reicherter |
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Institution: | (1) Institute of Geophysics, University of Hamburg, 20146 Hamburg, Germany;(2) Institute for Geology and Paleontology, University of Hamburg, 20146 Hamburg, Germany;(3) Institute of Biogeochemistry and Marine Chemistry, University of Hamburg, 20146 Hamburg, Germany;(4) Department of Neotectonics and Natural Hazards, RWTH, 52056 Aachen, Germany;(5) Present address: Faculty of Geosciences, University of Bremen, Klagenfurter Strasse, 28359 Bremen, Germany |
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Abstract: | High-resolution multi-channel seismic data from continental slopes with minor sediment input off southwest Mallorca Island,
the Bay of Oran (Algeria) and the Alboran Ridge reveal evidence that the Messinian erosional surface is terraced at an almost
constant depth interval between 320 and 380 m below present-day sea level. It is proposed that these several hundred- to 2,000-m-wide
terraces were eroded contemporaneously and essentially at the same depth. Present-day differences in these depths result from
subsidence or uplift in the individual realms. The terraces are thought to have evolved during one or multiple periods of
sea-level stagnancy in the Western Mediterranean Basin. According to several published scenarios, a single or multiple periods
of relative sea-level stillstand occurred during the Messinian desiccation event, generally known as the Messinian Salinity
Crisis. Some authors suggest that the stagnancy started during the refilling phase of the Mediterranean basins. When the rising
sea level reached the height of the Sicily Sill, the water spilled over this swell into the eastern basin. The stagnancy persisted
until sea level in the eastern basin caught up with the western Mediterranean water level. Other authors assigned periods
of sea-level stagnancy to drawdown phases, when inflowing waters from the Atlantic kept the western sea level constant at
the depth of the Sicily Sill. Our findings corroborate all those Messinian sea-level reconstructions, forwarding that a single
or multiple sea-level stagnancies at the depth of the Sicily Sill lasted long enough to significantly erode the upper slope.
Our data also have implications for the ongoing debate of the palaeo-depth of the Sicily Sill. Since the Mallorcan plateau
experienced the least vertical movement, the observed terrace depth of 380 m there is inferred to be close to the Messinian
depth of this swell. |
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