SSP1.10 | Restricted marine gateways and salt giants: oceanographic, climatic and biotic consequences
EDI

Straits linking the open ocean to marginal basins play an important role in driving global thermohaline circulation through the exchange of heat and salt. When these marine gateways allow only very limited exchange, typically during early stage opening and the final stages of closure, the marginal seas can experience extreme fluctuations in salinity, from brackish to hypersaline conditions, with knock-on consequences for the density contrast across the gateway. Restricted gateway exchange can result in the formation of “salt giants”, marginal basins characterized by the precipitation of large volumes of evaporites. In addition to their profound local impact, these salt giants can be sufficiently large to change the chemistry of the ocean, impact the carbon cycle and marine ecosystems, and modify climate on a global scale.
This session has been triggered by the upcoming IODP Expedition 401 which is part of the first land-2-sea project, IMMAGE. This project will recover Late Miocene gateway successions on either side of the Gibraltar Strait (IODP) and onshore records (ICDP) from the two fossil gateways that are preserved on land in Morocco and Spain. The contouritic sediments preserved in and oceanward of these gateways will provide a unique record of the Atlantic-Mediterranean exchange before, during and after the formation of the world’s most recent salt giant, which was deposited during the Messinian Salinity Crisis. IMMAGE will also directly test whether the representations of overflows in general circulation models (GCMs) are effective outside the range of validation provided by the modern ocean.
We welcome presentations from a wide range of researchers investigating the opening or closing of marine gateways, modern or ancient, and their climatic consequences. Our aim is to build a global community of scientists including physical oceanographers, climate modelers and geologists who wish to share and integrate established and novel approaches to studying marine connectivity and who will benefit from the samples and insights generated by upcoming IMMAGE drilling.

Convener: Dan Valentin PalcuECSECS | Co-conveners: Konstantina Agiadi, Rachel Flecker, Giovanni Aloisi, Claudia BertoniECSECS
Orals
| Wed, 26 Apr, 10:45–12:30 (CEST)
 
Room -2.21
Posters on site
| Attendance Tue, 25 Apr, 16:15–18:00 (CEST)
 
Hall X3
Posters virtual
| Attendance Tue, 25 Apr, 16:15–18:00 (CEST)
 
vHall SSP/GM
Orals |
Wed, 10:45
Tue, 16:15
Tue, 16:15

Orals: Wed, 26 Apr | Room -2.21

Chairpersons: Konstantina Agiadi, Dan Valentin Palcu, Giovanni Aloisi
10:45–10:50
Part1
10:50–11:00
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EGU23-15310
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SSP1.10
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On-site presentation
Guillermo Booth-Rea, Cesar Ranero, Jose Miguel Azañón, Carlos J. Garrido, and Fernando García-García

Paleogeographic reconstructions of the Western Mediterranean are often based on the present location of sedimentary outcrops. However, most geodynamic and biogeographic models for the region have highlighted the importance of up-to-hundreds of km of horizontal displacements of the terrains forming the western Mediterranean orogenic arcs since the early Miocene until the Pliocene. Here we update the known paleogeographic evolution for the westernmost Mediterranean, considering published biogeographic and recent new geological constraints, including paleontological, stratigraphic, tectonic kinematic data, seismic reflection lines, low-temperature thermochronological dating, detrital zircon age populations, among others. During the Burdigalian to Langhian the rocks of the Betic hinterland, corresponding to the Alboran domain, where exhumed in a forearc setting as far East as Mallorca, now located 450 to 700 km of their present outcrops. Those exhuming rocks floored sedimentary basins among an island archipelago. The land connection between Mallorca and Alboran domains continued until the Serravallian as attested by the shared fossils of vertebrate insular fauna and biogeographic data of different taxa including trap-door spiders, beetles and fresh-water planarians. The westward migration of the Alboran forearc archipelago and its overlying basins (currently forming the Betic intramontane and western Alboran basins) was concomitant to the Langhian to Tortonian opening of the Algero-Balearic back-arc basin and the retreat of the Betic-Rif subducted slab. At a smaller scale, the Granada supra-detachment intramontane basin moved > 100 km between the Tortonian and Present, implying that previously interpreted, emerged domains, like the Sierra Nevada island where either inexistent or in a different location during the Tortonian. Sediment interpreted to represent marine gateways around and through the Alboran archipelago in the westernmost Mediterranean, may have being partially deposited as far East as Mallorca, and probably migrated westwards from the Langhian to the late Pliocene in the Gibraltar straits. Of particular interest, is the Late Messinian to Late Pliocene westward migration of the Gibraltar straits documented by sedimentary onlap over erosive channels in the Western Alboran basin and marine terraces along its Betic and Rif shores. The above proposals are evolving questions concerning the Neogene paleogeographic evolution of the Western Mediterranean that may be tested by future work and drilling.

How to cite: Booth-Rea, G., Ranero, C., Azañón, J. M., Garrido, C. J., and García-García, F.: Migrating straits, basins and archipelagos: open questions about the Neogene paleographic evolution of the Westernmost Mediterranean, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15310, https://doi.org/10.5194/egusphere-egu23-15310, 2023.

11:00–11:10
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EGU23-7273
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SSP1.10
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On-site presentation
Olmo Miguez Salas and Francisco Rodríguez Tovar

Neoichnology of high energy deep-sea environments: A tool to improve gateways characterization

 

Olmo Miguez-Salas1, Francisco J. Rodríguez-Tovar2

 

1Department of Marine Zoology, Senckenberg Research Institute and Natural History Museum, 60325 Frankfurt, Germany.

2 Department of Stratigraphy and Paleontology, University of Granada, 18071 Granada, Spain

 

 

Evolution of ocean gateways determines significant changes in deep-water dynamics affecting depositional and ecological conditions. Particularly, variations in deep-water circulation associated to closing and opening gateways induce changes in hydrodynamic energy, rate of sedimentation, organic matter availability, salinity, oxygenation, etc., affecting benthic community. Modern biogenic structures (lebensspuren), as reflecting the behavior of the tracemaker to environmental conditions (i.e., depositional and ecological) reveal as a useful tool to interpret processes affecting deep-sea depositional settings. The exploration of these deep-sea environments and the in-situ observation of tracemakers require the expensive and time-consuming deployment of short-range observation gear, in many cases with inherent limitations, such as restricted fields of view in both spatial and temporal scales. However, in recent years neoichnological information from marine epibenthic lebensspuren (i.e., traces on the seafloor) has been obtained from videos or still images captured by cameras on autonomous and remotely operated underwater vehicles transiting on or above the seafloor. This new information reveals of major interest, especially in high-energy deep-sea environments, which can be correlated with those related to gateways and paleo-gateways.

In this study we present three cases that exemplify how lebensspuren features are related to deep-sea environments that have high-energy conditions: 1) Rosette-shape traces (RST) related to echiuran feeding activities. We study two locations of the Porcupine Abyssal Plain (NE Atlantic) where the seafloor consistency is different due to sporadic high energetic gravity flows as well as the local dominant megabenthos feeding group (e.g., suspension vs. deposit feeders). The seafloor consistency appeared not to affect RST morphology while the dominant feeding group seemed to control rosette areal coverage. 2) At an abyssal site in the NE Pacific ('Station M'), high-energy periods associated with benthic storms have been related to the impoverishment of lebensspuren abundance and diversity. The local-scale erosion and re-suspension of unconsolidated surface sediment inhibits the formation of previous softground traces and led to the redistribution of organic matter resources but the trace maker remained in the deep-sea station. These findings offer a new perspective where absence of traces may not imply tracemakers absence during quick (<1 day) energetic episodes at the deep-sea. 3) At an abyssal site with a dune field in the Bering Sea, lebensspuren abundance and diversity varies from the abyssal area to the dune field. Changes in the abundance of dwelling structures seem to be related to the high energetic conditions typical of deep-sea dunes.

 

How to cite: Miguez Salas, O. and Rodríguez Tovar, F.: Neoichnology of high energy deep-sea environments: A tool to improve gateways characterization, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7273, https://doi.org/10.5194/egusphere-egu23-7273, 2023.

11:10–11:20
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EGU23-12101
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SSP1.10
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On-site presentation
Or M Bialik, Jesus Reolid, Denise K Kulhanek, Carola Hincke, Nicolas D Waldmann, and Christian Betzler

During the early and middle Miocene, the Mediterranean became a restricted marginal sea with the contraction of the Mesopotamian Gateway and ultimate loss of connectivity to the Indian Ocean. Leading to the transformation of the Mediterranean into a restricted marginal marine sea . Low latitude circumglobal circulation through the basin characterized the basin for most of the Cretaceous and Paleogene. With the loss of this supply of surface and subsurface waters, dramatic changes occurred to the heat, energy, and nutrient budgets across the Mediterranean. The most affected area was the eastern basin. , As is well evidenced by the onset of sapropel formation, many other aspects of the sedimentary system changed in response to this ocean circulation rearrangement. Hemipelagic successions in southwestern Cyprus offer a window into the changes in the subsurface waters occurring in the Eastern Mediterranean through the closure of the gateway to the Indian Ocean. Dated to the late Aquitanian to the early Serravallian (22.5–14.5 Ma), this sequence is carbonate-dominated and overall continues. It exhibits sedimentation with mass transport contribution from shallow water carbonates to deeper facies. The succession exhibits fluctuation of bottom current activity, which was disrupted in the early Burdigalian by mass transports and temporarily halted during the Langhian. Phosphates are present through the entire succession, but most notably in the Langhian. Combined, these lithological characteristics indicate changes in bottom current energy and seafloor ventilation that point to two key intervals of connectivity restriction through the Mesopotamian gateway.

How to cite: Bialik, O. M., Reolid, J., Kulhanek, D. K., Hincke, C., Waldmann, N. D., and Betzler, C.: The impact of Indian Ocean - Mediterranean gateway closure on the current and nutrient regime in the Eastern Mediterranean during the early to middle Miocene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12101, https://doi.org/10.5194/egusphere-egu23-12101, 2023.

11:20–11:30
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EGU23-15668
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SSP1.10
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Virtual presentation
F. Javier Hernández-Molina, Zhi. L Ng, Debora Duarte, Estefanía Llave, Cristina Roque, Francisco J. Sierro, Wouter de Weger, Sandra de Castro, Sara Rodrigues, F. Javier Rodríguez-Tovar, Luis Miguel Fernández-Salas, Margarita García, Álvaro Arnaiz, David Roque, Miguel Bruno, and Ricardo F. Sánchez-Leal

Contourite depositional systems (CDS) represent the sedimentary records of paleoceanographic circulation and paleoclimatic changes throughout the geological timescale. These records offer expanded but contingent information relative to their adjacent marine gateways, documenting changes in the intensity and the direction of modern-day and paleo-current pathways on multi-centennial, millennial and million-year timescales. This study investigates the late Miocene to Quaternary CDSs from the Gulf of Cadiz towards the West Iberian margin after the exit of the past Betic and Rifian corridors and most recent Strait of Gibraltar, the key gateways for the Mediterranean – Atlantic exchange trough time. A summary of the key results is presented as a representative study case for decoding the long- and short-term behaviour of oceanographic processes related to gateways and their associated overflows.

In the study area, it is well known that the Mediterranean Outflow Water (MOW) has generated a complex CDS since the full opening of the Strait of Gibraltar in the early Pliocene (5.3 Ma). Recently, an ancient CDS has also been discovered in the late Miocene, which is separated from the Pliocene-Quaternary CDS by a period of quiescence representing the restriction of bottom water circulation across the Mediterranean-Atlantic exchange during the late Messinian (~6.4 - 5.3 Ma). The late Miocene CDS was established after the final closure of the Indian Gateway (IG) and the Neo-Tethys Ocean in the Middle Miocene, followed by the inception of the Mediterranean Sea (~13.8 - 11 Ma). The final closure of the IG conditioned a wide gateway configuration for the connection between the Mediterranean Sea and the Atlantic Ocean, with the full establishment of an anti-estuarine circulation similar to the present day as opposed to its previous situation.

Interestingly, both the late Miocene and the Pliocene-Quaternary CDSs have a long common evolution that could be simplified into two stages, with an initial- and growth-drift stages. The late Miocene CDS is then buried under dominantly hemipelagic late Messinian (~6.4 - 5.3 Ma) deposits, whereas the buried-drift stage is absent for the Pliocene-Quaternary system due to the ongoing nature of the CDS’s evolution. The long-term development of these CDSs can be correlated with a coeval shallowing of sills, which determined a change from an outflow to an overflow setting across the gateways through time. These long-term variations (>5-10 My) in paleo-circulation are thus driven by the by the tectonic control on the evolution of oceanic gateways. The internal sedimentary architecture of the late Miocene and Pliocene-Quaternary CDSs indicates a complex stratigraphic stacking pattern of deposits bounded by internal discontinuities and hiatuses in response to the intermittent behaviour of the MOW at different temporal scales, which have been attributed to tectonic pulses, climatic and eustatic changes and oceanographic processes that have caused deepening/shoaling or weakening/strengthening of bottom currents through time, exerting a major effect on deepwater sedimentation and the benthic habitat.

This project was funded by the JIP#1 within the framework of “The Drifters” Research Group at Royal Holloway University of London and related to the projects, CTM2016-75129-C3 (INPULSE) and PID2021-123825OB-I00 (ALGEMAR).

How to cite: Hernández-Molina, F. J., Ng, Zhi. L., Duarte, D., Llave, E., Roque, C., Sierro, F. J., de Weger, W., de Castro, S., Rodrigues, S., Rodríguez-Tovar, F. J., Fernández-Salas, L. M., García, M., Arnaiz, Á., Roque, D., Bruno, M., and Sánchez-Leal, R. F.: Late Miocene to Quaternary Contourites Depositional Systems in the Gulf of Cadiz and West Portugal related to the Mediterranean - Atlantic exchange evolution: decoding bottom currents behaviour and oceanographic processes associated with gateways, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15668, https://doi.org/10.5194/egusphere-egu23-15668, 2023.

11:30–11:40
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EGU23-7864
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SSP1.10
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On-site presentation
Zohar Gvirtzman, Hanneke Heida, Daniel Garcia-Castellanos, Oded Bar, Elchanan Zucker, and Yehouda Enzel

The extreme Mediterranean sea-level drop during the Messinian salinity crisis has been known for >50 years, but its amplitude and duration remain a challenge. Here we estimate its amplitude by restoring the topography of the Messinian Nile canyon and the vertical position of the Messinian coastline by unloading of post-Messinian sediment and accounting for flexural isostasy and compaction. We estimate the original depth of the geomorphological base level of the Nile River at ~600-m below present sea level, implying a drawdown 2-4 times smaller than previously estimated from the Nile canyon and suggesting that salt precipitated under 1-3-km deep waters. This conclusion is at odds with the nearly-desiccated basin model (>2 km drawdown) dominating the scientific literature for 50 years. Yet, a 600-m drawdown is ca. five times larger than eustatic fluctuations and its impact on the Mediterranean continental margins is incomparable to any glacial sea-level fall.

How to cite: Gvirtzman, Z., Heida, H., Garcia-Castellanos, D., Bar, O., Zucker, E., and Enzel, Y.: Limited Mediterranean sea-level drop during the Messinian salinity crisis inferred from the buried Nile canyon, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7864, https://doi.org/10.5194/egusphere-egu23-7864, 2023.

Part2
11:40–11:50
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EGU23-16940
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SSP1.10
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ECS
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On-site presentation
Laetitia Guibourdenche, Hanneke Heida, Federico Andreetto, and Giovanni Aloisi

At the end of the Miocene, the restriction of the Atlantic-Mediterranean seaway led to the deposition of a basin-wide salt giant (of up to 2.5km in thickness) in the Mediterranean. Drawdown(s) of the water level of the Mediterranean during this Messinian Salinity Crisis (MSC) have been proposed to have occurred. However, their number, timing and amplitude are still largely debated, with estimates ranging from 200m to 2km. While an important sea level fall could have efficiently blocked the Mediterranean outflow to the Atlantic Ocean, a limited drawdown would have allowed huge export of salt from the Mediterranean to the Atlantic Ocean, and in turn to the global ocean.  These two scenarios would thus have had opposite effects on thermohaline circulation and consecutively on climate. It is therefore crucial to estimate the water level of the Mediterranean during the MSC to understand its climatic and environmental effects both on a regional and global scale.

Here we investigated the deposits drilled by ODP and DSDP expeditions that characterize the terminal phase of the MSC in deep basins of the Mediterranean.  We measured the sulfur isotopic composition (both in sulfide and sulfate bearing minerals) in these deposits to constrain the maximal depth under which they formed, building on the observation that sea level is an important factor controlling sedimentary sulfur isotopic composition. We then used these maximal depths of deposition in a paleo-bathymetric reconstruction to constrain the amplitude of the base level fall that characterized the end of the Messinian Salinity Crisis. The result of this approach suggests a minimal water level drop of 1.1km in the western Mediterranean and a 1.7km drawdown at least in the eastern Mediterranean. This imply that these two basins were disconnected at the end of the MSC, and supports the findings of studies using independent seismic markers.

How to cite: Guibourdenche, L., Heida, H., Andreetto, F., and Aloisi, G.: Late Messinian Mediterranean base level fall : insights from sulfur isotopic variations coupled with isostasy-based paleo-depth estimates, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16940, https://doi.org/10.5194/egusphere-egu23-16940, 2023.

11:50–12:00
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EGU23-9969
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SSP1.10
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ECS
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On-site presentation
Hana Jurikova, Fernando Gázquez, Oscar Branson, David Evans, Matthew Dumont, Eszter Sendula, Robert Bodnar, Mebrahtu Weldeghebriel, Tim Lowenstein, and James Rae

The boron isotope composition of the ocean is homogeneous, but varies on multi-million year time scales, given its residence time of approximately 10 million years. To date, the secular evolution of the oceanic boron isotope budget has been difficult to constrain. The lack of knowledge on past boron isotope composition of seawater (δ11Bsw) poses a major uncertainty for reliable boron-based pH and CO2 reconstructions from Earth’s geologic past and critically limits our understanding of the global biogeochemical cycling of this important element through time. Evaporitic minerals bearing fluid inclusions – and halites in particular – present a highly appealing archive for reconstructing δ11Bsw given their direct origin from seawater. However, the interpretation of their boron isotope signatures is not straightforward due to the possibility of fractionation during evaporation and crystallisation. Here we present first insights into boron isotope evolution during evaporite formation from laboratory experiments and natural modern evaporitic settings. These data enable us to place constraints on boron fractionation in ancient evaporites, offering new insights into δ11Bsw during some of the key periods of the Phanerozoic.

How to cite: Jurikova, H., Gázquez, F., Branson, O., Evans, D., Dumont, M., Sendula, E., Bodnar, R., Weldeghebriel, M., Lowenstein, T., and Rae, J.: Secular evolution of boron isotope composition of seawater archived in evaporites?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9969, https://doi.org/10.5194/egusphere-egu23-9969, 2023.

12:00–12:10
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EGU23-9065
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SSP1.10
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On-site presentation
Francesca Lanterna, Iuliana Vasiliev, Francisco Javier Sierro, and Andreas Mulch

In the Mediterranean region, the end of the Miocene is marked by the Messinian Salinity Crisis (MSC; 5.97 - 5.33 Ma), a peculiar event that governed environmental modifications in the region, causing the deposition of large thicknesses of evaporitic rock units, dramatic hydrological and ecological crises that affected both water and land-based habitats. The onset of the MSC has been proven to be synchronous over the Mediterranean basin as demonstrated by astronomical tuning of the pre-evaporitic sedimentary successions. Among these, the Sorbas Basin plays a pivotal role for the understanding of the palaeoceanographic evolution of the Western Mediterranean Sea before the onset of the MSC. Its location within proximity of the Atlantic gateway renders the Sorbas Basin an exceptional recorder of palaeoceanographic changes just prior to the MSC. The pre-evaporitic sequence starts with Tortonian calcarenites (belonging to the Azagador Member) followed by early Messinian clays and diatomites (belonging to the Abad Member). The Lower Abad Member, consists of indurated whitish marls and softer grey marls which contrast sapropel and diatomite alterations of the Upper Abad Member. Here, we present biomarker-based sea surface temperatures (SST) using TEX86 paleotemperatures recorded in the Sorbas basin for the time interval between 7.3 and 6.1 Ma. The TEX86 SST estimates show a generally decreasing trend, with a 7.26 Ma to 7.11 Ma warm phase (averaging 27 °C). This warm phase is followed by ~5°C cooling (to values averaging 22 °C) after 7.11 Ma, with two distinct colder peaks, one centred around 7.09 Ma and one around 6.95 Ma. The cooling after 7.11 Ma follows shallowing and restriction in the Betic and Rifian marine gateways and is most likely controlled by global cooling characterizing the latest Miocene. In a second step, we couple the TEX86 SST estimates with oxygen stable isotope ratios (δ18O) measured on the surface-dwelling planktonic foraminifera Orbulina universa to reconstruct sea surface salinity (SSS) variations at the corresponding stratigraphic levels for the study interval. The newly acquired SST and SSS data from the Sorbas Basin provide a previously unavailable record of changed environmental conditions recorded in the Western Mediterranean Basin that permit direct comparison across the Mediterranean Basin with the recently acquired Messinian Eastern Mediterranean SST and SSS changes.

How to cite: Lanterna, F., Vasiliev, I., Sierro, F. J., and Mulch, A.: Sea Surface Temperatures variations during the Messinian in the Sorbas Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9065, https://doi.org/10.5194/egusphere-egu23-9065, 2023.

12:10–12:20
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EGU23-2922
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SSP1.10
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ECS
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On-site presentation
Francesca Bulian, Francisco J. Jiménez-Espejo, Nils Andersen, Juan C. Larrasoaña, and Francisco J. Sierro

At present, the Mediterranean is connected to the Atlantic Ocean through the narrow Strait of Gibraltar (only 13 km wide). The latter, in the late Miocene, most probably did not exist, and the Mediterranean – Atlantic water exchange took place through the Betic (Southern Spain) and Rifian (Northern Morocco) corridors. Studying the evolution of such gateways is fundamental when investigating the extraordinary event known as the Messinian Salinity Crisis (5.96 – 5.33 Ma), when the connection between the Mediterranean Sea and Atlantic Ocean significantly diminished or even ceased. In this work we present a new high resolution geochemical (XRF and stable isotope) record of the Tortonian – Messinian interval of the Montemayor-1 and Huelva-1 cores located in the Betic corridor, current Guadalquivir Basin. Our new data enabled in the first place the high-resolution tuning of the 7.4 – 5.8 Ma time interval, and consequently to precisely date environmental changes and relate them to Mediterranean and global events.

Our results indicate that, at 7.17 Ma and in concomitance with a shallowing of the basin, the bottom water residence time, temperature and salinity increased. These changes have been associated with a reduction of the Mediterranean Outflow Water reaching the Guadalquivir Basin as a consequence of the restriction of the last strand of the Betic corridor connecting the Mediterranean and the Atlantic. This hypothesis is in line with the analogous changes observed in several Mediterranean Sea locations, where from 7.17 Ma a reduced Mediterranean – Atlantic connection is visible. Nonetheless, even if such reduction of the connection was feasible, the same changes in isotope record and analogous cyclicity observed both in the Guadalquivir and Alboran Basin record imply that the Mediterranean signal was still reaching the Betic gateway to some degree. In addition, the significant offset present between our and North Atlantic oxygen stable isotope records entails how the signal in the Guadalquivir basin could not have been purely Atlantic. Consequently, we conclude that a significant Mediterranean signal was still present in the Betic corridor during the Messinian.

How to cite: Bulian, F., Jiménez-Espejo, F. J., Andersen, N., Larrasoaña, J. C., and Sierro, F. J.: Evidence of Mediterranean water in the Atlantic margin during the Messinian, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2922, https://doi.org/10.5194/egusphere-egu23-2922, 2023.

12:20–12:30
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EGU23-8524
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SSP1.10
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ECS
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On-site presentation
Isabel van der Hoeven, Katharine Grant, Eelco Rohling, Diederik Liebrand, Lucas Lourens, Gert-Jan Reichart, and Rick Hennekam

Restricted basins are susceptible to develop anoxia because these land-locked basins can trap nutrients and the water column can easily become stratified. The Mediterranean basin has a limited connection to the open ocean and became increasingly restricted over time, making it suitable to study effect of basin configuration on anoxia development. Enhanced runoff, related to increased North-African monsoon intensity, regularly resulted in increased productivity and/or deep-water anoxia and deposition of organic-rich sediments, the so-called sapropels. Most depositional models for sapropel formation focus on the most recent sapropels (e.g. S1 and S5), outcrop samples or individual Pliocene sapropels from ODP leg 160. Until recently, continuous and high-resolution records were lacking, whereas such records can provide important constraints on the relationship between sapropel deposition and its environmental driving forces, such as climate and basin configuration. Here we present newly acquired XRF-scanning data of redox-sensitive trace elements and estimates for total organic carbon (TOC) from a 5 Myr record of the Eastern Mediterranean Sea (ODP Site 967), where reoccurring sapropels are recorded from 3.2 Ma onwards. Based on our geochemical proxies, we reconstruct (de)oxygenation and associated basin restriction over the last 5 Myr. This record allows us to elucidate which primary processes drove sapropel formation in this basin and whether these processes changed over time. We show that the first preserved Pliocene sapropels (~3.2-3.0 Ma) are highly enriched in redox-sensitive trace elements and have TOC values up to 25%, and likely formed in a much more open (i.e. with increased water renewal) depositional environment. Such a model of Mediterranean sapropel deposition differs significantly from that of the more recent sapropels, which are deposited in a much more restricted environment. Hence, the depositional model for recent sapropel formation cannot be directly extrapolated to these older sapropel deposits.

How to cite: van der Hoeven, I., Grant, K., Rohling, E., Liebrand, D., Lourens, L., Reichart, G.-J., and Hennekam, R.: A 5-million-year record of (de)oxygenation and associated changes in basin restriction in the Mediterranean Sea, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8524, https://doi.org/10.5194/egusphere-egu23-8524, 2023.

Posters on site: Tue, 25 Apr, 16:15–18:00 | Hall X3

Chairpersons: Dan Valentin Palcu, Konstantina Agiadi
X3.61
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EGU23-7669
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SSP1.10
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ECS
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Highlight
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Dan Valentin Palcu, Hanneke Heida, Ionut Sandric, Sergey Popov, Daniel Garcia Castellanos, and Wout Krijgsman
During the Messinian Salinity Crisis (MSC), as the Mediterranean realm experienced partial desiccation, water levels in Paratethys, a vast waterbody in the middle of Eurasia, remained largely unaffected except in its easternmost domain, the Caspian basin, which experienced a severe partial desiccation. Still, its relation and role in the dynamics of the MSC are controversial.Here we reconstruct the paleogeographic evolution of the Paratethys region during the MSC. We  show that the Paratethys realm irreversibly fragmented into smaller basins (Dacian, Black Sea, Caspian) triggering a reorganization of the Paratethys watershed during the MSC. 
The Paleo-Don River, the main river flowing in Paratethys, was captured by the Black Sea basin enhancing the excess of water was spilled in the Mediterranean and affecting the hydrology of the Mediterranean during the Lago Mare phase of the MSC. 
The Caspian basin, isolated and deprived of major river inflows, became partially desiccated, experiencing a ~400m base level drop. Extensive canyons developed and expanded in the central-northern Caspian Basin forming a new river - the Volga, that would later capture the eastern watershed of the Paleo-Don and partially refill the Caspian basin. 
These findings reveal that the MSC had extensive, continental consequences: destabilizing the Paratethys realm and reorganizing the river networks of Eastern Europe. This paleogeographic reorganization and the shifts in freshwater budgets may represent a key piece of the puzzle of the water balance in the Mediterranean basin during the MSC.

How to cite: Palcu, D. V., Heida, H., Sandric, I., Popov, S., Garcia Castellanos, D., and Krijgsman, W.: The demise of Paratethys in the time of the Messinian Salinity Crisis: impact on Eurasian paleogeography and Mediterranean environments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7669, https://doi.org/10.5194/egusphere-egu23-7669, 2023.

X3.62
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EGU23-17215
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SSP1.10
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Highlight
Konstantina Agiadi, Niklas Hohmann, Elsa Gliozzi, Danae Thivaiou, Alberto Collareta, Francesca Bosellini, Giovanni Bianucci, Laurent Londeix, Francesca Bulian, Francesca Lozar, Alan Maria Mancini, Stefano Dominici, Pierre Moissette, Ildefonso Bajo Campos, Enrico Borghi, George Kontakiotis, Stergios Zarkogiannis, Mathias Harzhauser, Angelo Camerlenghi, and Daniel Garcia-Castellanos

Physical connectivity between marine basins facilitates population exchange and hence controls biodiversity. The Mediterranean Sea is a semi-restricted basin with only a small two-way connection to the global ocean, and it is a region heavily impacted by climate change and biological invasions today. The massive migration of non-indigenous species into the basin through the Suez Canal, driven and enabled by climate warming, is drastically changing Mediterranean biodiversity. Understanding therefore the origin and cause(s) of pre-existing biodiversity patterns is crucial for predicting future impacts of climate change. Mediterranean biodiversity exhibits a west-to-east decreasing gradient in terms of species richness, but the processes that resulted in this gradient have only been hypothesized. By examining the fossil record, we provide evidence that this gradient developed 5.33 million years ago at the end of the Messinian Salinity Crisis, and it was therefore caused by the re-population of the basin by marine species with a dominating western source at the Mediterranean–Atlantic gateway.

How to cite: Agiadi, K., Hohmann, N., Gliozzi, E., Thivaiou, D., Collareta, A., Bosellini, F., Bianucci, G., Londeix, L., Bulian, F., Lozar, F., Mancini, A. M., Dominici, S., Moissette, P., Campos, I. B., Borghi, E., Kontakiotis, G., Zarkogiannis, S., Harzhauser, M., Camerlenghi, A., and Garcia-Castellanos, D.: Mediterranean biodiversity gradient initiated by basin restriction, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17215, https://doi.org/10.5194/egusphere-egu23-17215, 2023.

X3.63
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EGU23-9107
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SSP1.10
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ECS
Nevena Andrić-Tomašević, Oleg Mandic, Armin Zeh, Vladimir Simić, and Sejfudin Vrabac

The Central Paratethys Sea occupied the transition between the Alps, Dinarides and Carpathian mountains during Oligocene to Miocene times. However, its spatial and temporal evolution, i.e. southward expansion, subsequent salinity crisis, and governing mechanisms are poorly constrained. Here, we employ radiometric dating to construct the Middle Miocene absolute chronology of the evolution of the successions developed along the southwestern margin of the Central Paratethys flanking the NE Dinarides (NE Bosnia and Herzegovina) and governing mechanisms. We present three U-Pb zircon ages acquired by LA-ICP-MS from volcanic ash layers sampled in Tuzla marginal marine basin (two layers) and neighboring lacustrine Lopare Basin (one layer). Zircon grains from the lowermost ash of the playa lake in Lopare Basin yielded a U-Pb age of 15.143 ± 0.094 Ma. This indicates that despite the warm and humid global climate, the Lopare Basin and many lakes in the internal part of the Dinarides hosting similar salina-type successions recorded regional arid climatic conditions during Middle Miocene. Furthermore, this age implies synchronicity of arid with humid lakes (e.g., Sinj, Gacko) developed in the internal and external Dinarides, respectively which are orographically controlled. The U-Pb zircon age of the middle ash layer (14.12 ± 0.077 Ma) places new constraints on the marine flooding in the Tuzla Basin, i.e. along the southwestern margin of the Central Paratethys. Considering age data from previous studies the new age implies south-southeastward marine expansion of the Central Parathetys over a period of 3-4 Myrs, along the N, NE-ward flanks of the Dinarides. The demise of the Dinarides affected by the rift climax in the neighbouring Pannonian Basin and associated block rotations provided a space for the S/SE-ward marine expansion. Deposition of the uppermost ash layer sampled at the top of marine salt succession in Tuzla Basin is constrained by a U-Pb zircon age of 13.88 ± 0.11 Ma. This indicates that Salinity Crisis in Badenian was affecting the entire Central Parathehys coevally. Therefore, we correlate the evaporitic event in the Tuzla basin with the sea-level fall controlled by the global climatic Mi3b event.

How to cite: Andrić-Tomašević, N., Mandic, O., Zeh, A., Simić, V., and Vrabac, S.: Middle Miocene events in the peripheral basins of Central Paratethys (Central Europe): inferences from Tuzla and Lopare basins, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9107, https://doi.org/10.5194/egusphere-egu23-9107, 2023.

X3.64
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EGU23-13297
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SSP1.10
Iuliana Vasiliev, Konstantina Agiadi, Jens Fiebig, and Andreas Mulch

Between 5.97-5.33 Ma, kilometre-thick evaporite units were deposited in the Mediterranean Basin during the so-called Messinian Salinity Crisis (MSC). The MSC was marked by a strongly negative hydrological budget, with a net evaporative loss of water exceeding precipitation and riverine runoff. Knowledge about the contemporary changes in continental and marine circum-Mediterranean environments are still limited to qualitative descriptions in terms of temperature and humidity. Here we reconstruct continental mean annual temperatures (MAT) using branched glycerol dialkyl glycerol tetraether (brGDGT) biomarkers for the time period corresponding to MSC Stage 3 (5.55-5.33 Ma) and compare them with values obtained from Δ47 clumped isotope geochemistry measured on paleosol carbonate nodules found at few locations in the Mediterranean basin. Additionally, for the same time interval, we estimate sea surface temperatures (SSTs) of the Mediterranean Sea using the isoprenoidal GDGT-based TEX86 proxy. The excellently preserved organic biomarkers were extracted from outcrops onshore (Malaga, Sicily, Cyprus) and offshore (DSDP core holes 124 and 134 from the Balearic abyssal plane, hole 374 from the Ionian Basin and hole 376 drilled west of Cyprus) covering a rather vast portion of the Mediterranean Basin.

Calculated MATs for the 5.55 to 5.33 Ma time interval show values around 16 to 19 ºC for the Malaga, Sicily and Cyprus outcrops. The MAT values calculated for DSDP Leg 13 holes 124, 134 and Leg 42A holes 374 and 376 are lower, around 13 to 16 ºC. Comparing the brGDGT-MAT values with Δ47-MAT values from carbonate nodules, shows high congruence between both approaches. For the northern Mediterranean Δ47-MAT is 20 ºC and brGDGT-MAT is 19 ºC. For Cyprus Δ47-MAT is 21 ºC and brGDGT-MAT is 18 ºC. Given the very different type of the used paleoproxies, the similarity of the obtained MAT values provides a strong indication of their (cross)validity in sampled sections. Additionally, the measured δ18O values of ~33‰ (VSMOW) for the carbonate nodules used for the Δ47-MAT indicate highly evaporative conditions for the two onland sites where these were collected (Northern Apennines and Cyprus).

For samples where the branched and isoprenoid tetraether index was lower than 0.4 we could calculate TEX86 derived SSTs averaging around 27 ºC for all sampled locations, reaching the higher end of the values obtained in the Mediterranean region for the pre-MSC through Uk37 and TEX86 derived SSTs of Tzanova et al. (2015), Vasiliev et al. (2019) and Kontakiotis et al. 2022. Independent of pitfalls that may arise in using molecular biomarkers as temperature proxies, both SST estimates independently hint towards much warmer Mediterranean Sea water during the latest phase, Stage 3 of the MSC. These elevated temperatures coincide with higher δ2H values measured on alkenones and long chain n-alkanes (both records indicating more arid and/or warmer conditions than today between 5.55 and 5.33 Ma). We conclude that between 5.55 to 5.33 Ma the temperatures in the Mediterranean region was similar to present-day conditions, yet the region has suffered from excess evaporation as indicated by combined high δ18O values from carbonate nodules δ2H values from biomarkers.

How to cite: Vasiliev, I., Agiadi, K., Fiebig, J., and Mulch, A.: A drier Mediterranean region at the Miocene to Pliocene transition, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13297, https://doi.org/10.5194/egusphere-egu23-13297, 2023.

X3.65
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EGU23-1186
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SSP1.10
Konstantina Agiadi, Iuliana Vasiliev, Geanina Butiseaca, George Kontakiotis, Danae Thivaiou, Evangelia Besiou, Stergios Zarkogiannis, Efterpi Koskeridou, Assimina Antonarakou, and Andreas Mulch

The restriction of the Mediterranean–Atlantic marine connection over the Messinian stage, which led to a salinity crisis and the deposition of the youngest salt giant on Earth, impacted the composition and structure of marine biota in unprecedented ways, but its effects on the biological functions of marine organisms remains unchartered territory. By analyzing the stable oxygen and carbon isotopic composition of the otoliths of two carefully selected fish species, a pelagic (surface) and a benthic (bottom-dwelling) one, we were able to infer not only the sea surface and bottom salinity and oxygenation conditions, but also the fishes’ metabolic response to the paleoceanographic changes in the eastern Mediterranean from 7.2 to 6.5 Ma. The high salinity and stratification of the Mediterranean water column during this interval hampered the ability of the marine fishes to grow, particularly those dwelling in the sea bottom. A first event (6.82–6.81 Ma) of high temperature and salinity induced an increase in the metabolism of fishes across the water column, meaning that they consumed and respired more. Subsequent warming, increased salinity and stratification at 6.70–6.69 Ma further intensified the environmental stress for bottom-water fishes. To cope with these extreme conditions at the sea floor, benthic fishes show increased metabolic carbon despite low food availability, which implies that fishes metabolized (i.e. consumed) their own tissue to survive. The disappearance of benthic fishes in the study area after 6.8 Ma further reinforces this conclusion. Our study promotes the importance of otoliths stable isotopic analyses as tools for reconstructing complex paleoenvironmental histories.

How to cite: Agiadi, K., Vasiliev, I., Butiseaca, G., Kontakiotis, G., Thivaiou, D., Besiou, E., Zarkogiannis, S., Koskeridou, E., Antonarakou, A., and Mulch, A.: Fish starved to death by Mediterranean water-column stratification and high salinity in pre-evaporitic Messinian, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1186, https://doi.org/10.5194/egusphere-egu23-1186, 2023.

X3.66
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EGU23-17219
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SSP1.10
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Highlight
Rachel Flecker and Olivia Gaitonde and the IMMAGE Co-I Team

Marine gateways play a critical role in the exchange of water, heat, salt and nutrients between oceans and seas. The advection of dense waters helps drive global thermohaline circulation and, since the ocean is the largest of the rapidly exchanging CO2 reservoirs, this advection also affects atmospheric carbon concentration. Changes in gateway geometry can therefore significantly alter both the pattern of global ocean circulation and associated heat transport and climate, as well as having a profound local impact.

Today, the volume of dense water supplied by Atlantic-Mediterranean exchange through the Gibraltar Strait is amongst the largest in the global ocean. For the past five million years this overflow has generated a saline plume at intermediate depths in the Atlantic that deposits distinctive contouritic sediments in the Gulf of Cadiz and contributes to the formation of North Atlantic Deep Water. This single gateway configuration only developed in the early Pliocene, however. During the Miocene, a wide, open seaway linking the Mediterranean and Atlantic evolved into two narrow corridors: one in northern Morocco; the other in southern Spain. Formation of these corridors permitted Mediterranean salinity to rise and a new, distinct, dense water mass to form and overspill into the Atlantic for the first time. Further restriction and closure of these connections resulted in extreme salinity fluctuations in the Mediterranean, leading to the formation of the Messinian Salinity Crisis salt giant.

IMMAGE is a land-2-sea drilling project designed to recover a complete record of Atlantic-Mediterranean exchange from its Late Miocene inception to its current configuration. This will be achieved by targeting Miocene offshore sediments on either side of the Gibraltar Strait with IODP during Expedition 401 (December 2023-February 2024) and recovering Miocene core from the two precursor connections now exposed on land with ICDP. The scientific aims of IMMAGE are to constrain quantitatively the consequences for ocean circulation and global climate of the inception of Atlantic-Mediterranean exchange; to explore the mechanisms for high amplitude environmental change in marginal marine systems and to test physical oceanographic hypotheses for extreme high-density overflow dynamics that do not exist in the world today on this scale.

How to cite: Flecker, R. and Gaitonde, O. and the IMMAGE Co-I Team: Investigating Miocene Mediterranean-Atlantic Gateway Exchange (IMMAGE): the first land-2-sea drilling project, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17219, https://doi.org/10.5194/egusphere-egu23-17219, 2023.

Posters virtual: Tue, 25 Apr, 16:15–18:00 | vHall SSP/GM

Chairpersons: Konstantina Agiadi, Dan Valentin Palcu
vSG.9
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EGU23-13517
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SSP1.10
Francisco Javier Rodriguez Tovar, Francisco Javier Hernandez Molina, and Olmo Miguez-Salas

Closing and opening of ocean paleo-gateways strongly influenced the tectono-stratigraphic and sedimentary evolution of basins, affecting global ocean circulation, climate, sedimentary processes, and living biota. Particularly, closing and opening of ocean paleo-gateways determine significant changes in ocean dynamic affecting deepwater circulation, and then deepsea sedimentary facies and benthic community. Changes in bottom-current dynamic and their effects (e.g., erosion, nondeposition and variable rate of deposition) can cause changes in substrate features that might exert a major effect on the benthic habitat. To improve knowledge of paleo-gateways, involved oceanographic processes, and variations in the depositional systems, detailed analysis of the Contourite Depositional Systems and associated sediments controlled by deep-water circulation processes reveals of major interest. In this context an integrative ichnological and sedimentological approach is proved as a useful strategy.

This study focuses in the application of an integrative sedimentological (i.e., primary sedimentary structures, grain size analysis, microfacies, etc.) and ichnological approach to improve characterization of contourites and differentiation from other deep-sea facies associated to paleo-gateways. Examples from middle Miocene contourite deposits in Cyprus associated to the Indian Gateway, the late Miocene contourites Morocco related to the Rifian Corridor and from the Pliocene and Quaternary deposits in the Gulf of Cadiz related to the Strait of Gibraltar are presented. Changes in paleoenvironmental (ecological and depositional) conditions induced by gateways evolution, as hydrodynamic energy, rate of sedimentation, organic matter availability, affecting tracemaker community are interpreted based on integration of sedimentological and ichnological features.

How to cite: Rodriguez Tovar, F. J., Hernandez Molina, F. J., and Miguez-Salas, O.: Contourites and paleo-gateways: An integrative ichnological and sedimentological approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13517, https://doi.org/10.5194/egusphere-egu23-13517, 2023.

vSG.10
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EGU23-17206
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SSP1.10
Giovanni Aloisi, Jimmy Moneron, Laetitia Guibourdenche, Angelo Camerlenghi, Ittai Gavrieli, Gerard Bardoux, Pierre Agrinier, and Zohar Gvirztman

Hydrological restriction from the Atlantic Ocean and a negative freshwater balance transformed the Mediterranean Sea into a giant saline basin during the Messinian Salinity Crisis (MSC) (5.97 – 5.33 million years ago). After more than 50 years of research, it is still unclear if the deposition of nearly one million km3 of evaporite salts during this event was accompanied by a major (≥ 1.5 km) drawdown of Mediterranean sea level; and if halite deposition occurred only during this drawdown event, or also in a filled Mediterranean connected to the Atlantic.

We present evidence based on the chlorine stable isotope composition of halite for a sea level drawdown of 2 km in the eastern Mediterranean during the final stages of deposition of the Mediterranean halite layer. This is the largest sea level drop ever reported from the geological record and implies a short (~20 kyr), but nearly complete hydrological disconnection of the Mediterranean from the Atlantic. About half of the halite volume in the eastern Mediterranean was deposited during this drawdown event. Scant chlorine isotope data from the western Mediterranean, together with new estimates of western basin halite volume, suggest that the complete western halite deposit accumulated during the drawdown event. This mode of halite deposition - termed “evaporative drawdown” - had been already proposed as an evolution of the “deep-basin, shallow-water” scenario for the MSC (Hsü et al., 1973).

Chlorine isotopes indicate that the remaining half of the eastern Mediterranean halite volume accumulated prior to the drawdown, in a filled Mediterranean that received a continuous input of Atlantic waters. This halite accumulation phase lasted about 70 kyr and was driven by a restricted - but not fully blocked - outflow of deep western Mediterranean waters to the Atlantic. This model of halite deposition corresponds to the “deep-basin, deep-water” scenario for the MSC (Schmaltz, 1969). In summary, our results show that both the “deep-basin, deep-water” and the “deep-basin, shallow-water” modes of halite accumulation took place during the MSC, and that the complete deep-basin MSC halite deposit accumulated in less than 100 kyr.

 

Hsu, K., Ryan, W. & Cita, M. Late Miocene Desiccation of Mediterranean. Nature 242, 240–244 (1973).

Schmalz, R. F. Deep-water evaporite deposition, a genetic model. American Association of Petroleum Geologists Bulletin53, 798–823 (1969).

How to cite: Aloisi, G., Moneron, J., Guibourdenche, L., Camerlenghi, A., Gavrieli, I., Bardoux, G., Agrinier, P., and Gvirztman, Z.: Modes of deep basin halite accumulation during the Messinian Salinity Crisis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17206, https://doi.org/10.5194/egusphere-egu23-17206, 2023.