“…This is consistent with the hypothesis that the structure of the atmospheric circulation over the Mediterranean remained largely unchanged during precession cycles despite changes in the sources and amount of moisture advection (Rogerson et al, 2019) and with the establishment of basin-wide ocean circulation and environmental conditions similar to today after the closure of the Indian Gateway (e.g. de la Vara and Meijer, 2016) in the early to middle Miocene (14 to 14.5 Ma) (e.g. Rögl, 1999) .…”
Section: Implications For the Interpretation Of The Sedimentary Recordsupporting
Cyclic sedimentary patterns in the marine record of the Mediterranean Sea have been consistently correlated with orbitally-driven shifts in climate. Freshwater input driven by the African summer monsoon is thought to be the main control of such hydrological changes, where the runoff signal is transferred from the eastern to the western Mediterranean. The geological record from the Atlantic margin also contains precession-driven dilution cycles that have been correlated with the sedimentary sequences in the western and eastern Mediterranean despite the lack of a direct connection with the basin. In these regions, Atlantic winter storms have also been invoked to explain the wet phases. In the absence of seasonally-resolved proxy data, climate simulations at high temporal resolution can be used to investigate the drivers of Mediterranean hydrologic changes both on precessional and seasonal timescales. Here, we use the results of 22 ocean-atmosphere-vegetation simulations through an entire late Miocene precession cycle. These show that the African summer monsoon drives the hydrologic budget in the Eastern Mediterranean during precession minima, while the western marginal basins are generally dominated by local net evaporative loss. During precession minima, the western Mediterranean and the Atlantic margin are also influenced by enhanced winter precipitation from the Atlantic storm tracks. We can, therefore, identify two different moisture sources affecting the circum-Mediterranean area, characterized by the same phasing with respect to precession, but with opposite seasonality. This supports the interregional correlation of geological sections in these areas, as we show for the Messinian and speculate for other time periods.
“…This is consistent with the hypothesis that the structure of the atmospheric circulation over the Mediterranean remained largely unchanged during precession cycles despite changes in the sources and amount of moisture advection (Rogerson et al, 2019) and with the establishment of basin-wide ocean circulation and environmental conditions similar to today after the closure of the Indian Gateway (e.g. de la Vara and Meijer, 2016) in the early to middle Miocene (14 to 14.5 Ma) (e.g. Rögl, 1999) .…”
Section: Implications For the Interpretation Of The Sedimentary Recordsupporting
Cyclic sedimentary patterns in the marine record of the Mediterranean Sea have been consistently correlated with orbitally-driven shifts in climate. Freshwater input driven by the African summer monsoon is thought to be the main control of such hydrological changes, where the runoff signal is transferred from the eastern to the western Mediterranean. The geological record from the Atlantic margin also contains precession-driven dilution cycles that have been correlated with the sedimentary sequences in the western and eastern Mediterranean despite the lack of a direct connection with the basin. In these regions, Atlantic winter storms have also been invoked to explain the wet phases. In the absence of seasonally-resolved proxy data, climate simulations at high temporal resolution can be used to investigate the drivers of Mediterranean hydrologic changes both on precessional and seasonal timescales. Here, we use the results of 22 ocean-atmosphere-vegetation simulations through an entire late Miocene precession cycle. These show that the African summer monsoon drives the hydrologic budget in the Eastern Mediterranean during precession minima, while the western marginal basins are generally dominated by local net evaporative loss. During precession minima, the western Mediterranean and the Atlantic margin are also influenced by enhanced winter precipitation from the Atlantic storm tracks. We can, therefore, identify two different moisture sources affecting the circum-Mediterranean area, characterized by the same phasing with respect to precession, but with opposite seasonality. This supports the interregional correlation of geological sections in these areas, as we show for the Messinian and speculate for other time periods.
“…Labelling of waters flowing in from the Indian Ocean with highly radiogenic Nd isotope signatures can explain the observed more positive ɛNd signatures found in the Maltese and northern Italian records during the Late Oligocene and Early Miocene. Based on inflow parameters obtained from modelling 6 and the Nd isotope compositions in each oceanic basin (Table S1), we calculate the ɛNd signatures of the Mediterranean waters using a simple box model including the effect of Nd addition from, or exchange with the volcanic source rocks (Fig. 3).…”
Section: Resultsmentioning
confidence: 99%
“…For this study, two isolated carbonate platform sites at both sides of the Tethyan Seaway were chosen (Fig. 1): The Maldives in the Indian Ocean and Malta in the Mediterranean.Figure 1Early to Middle Miocene paleogeography of the Mediterranean Sea and western Indian Ocean 13 : Arrows indicate surface circulation patterns 6,12,101 , with black arrow indicate surface waters and white intermediate to deep waters. Red numbers indicate potential source areas of runoff with positive εNd signatures.…”
Section: Geological Settingmentioning
confidence: 99%
“…The initial disconnection of the Mediterranean realm from the world oceans occurred at the eastern end of the present Mediterranean Sea and resulted in the termination of the low latitude circumglobal ocean circulation. This connection allowed transport of Indian Ocean surface waters to the Atlantic Ocean and at the same time subsurface waters were advected to the Indian Ocean 5,6 . The newly formed enclosed Mediterranean Sea subsequently experienced intervals of anoxic and suboxic conditions of its deep waters resulting in sapropel deposition.…”
The Tethys Ocean was compartmentalized into the Mediterranean Sea and Indian Ocean during the early Miocene, yet the exact nature and timing of this disconnection are not well understood. Here we present two new neodymium isotope records from isolated carbonate platforms on both sides of the closing seaway, Malta (outcrop sampling) and the Maldives (IODP Site U1468), to constrain the evolution of past water mass exchange between the present day Mediterranean Sea and Indian Ocean via the Mesopotamian Seaway. Combining these data with box modeling results indicates that water mass exchange was reduced by ~90% in a first step at ca. 20 Ma. The terminal closure of the seaway then coincided with the sea level drop caused by the onset of permanent glaciation of Antarctica at ca. 13.8 Ma. The termination of meridional water mass exchange through the Tethyan Seaway resulted in a global reorganization of currents, paved the way to the development of upwelling in the Arabian Sea and possibly led to a strengthening of South Asian Monsoon.
“…Through the Miocene fundamental shifts in phosphogenesis patterns (Auer et al, 2016;Föllmi et al, 2015), sedimentation patterns (Torfstein and Steinberg, 2020) and structure of shallow-water calcifying communities (Bosellini and Perrin, 2008;Pomar and Hallock, 2007) occurred. Modelling work suggests that the direct effects of the change in connectivity were the reversal of zonal circulation in the upper water column and reduced turnover of the lower water column (de la Vara, 2015;de la Vara et al, 2013;de la Vara and Meijer, 2016), which might have reduced ventilation. This shift also led to the rise of the modern Mediterranean Sea circulation.…”
During the early and middle Miocene, the Mediterranean had become a restricted marginal marine sea with diminishing and ultimate loss of connectivity to the Indian Ocean. This dramatically changed the heat, energy, freshwater and nutrient budgets across the Mediterranean and most notably in its eastern basin. While one of the most prominent lines of evidence of this change in the Eastern Mediterranean is the onset of sapropel formation, many other aspects of the sedimentary system changed in response to this rearrangement. Here we present a detailed analysis of a hemipelagic succession from southeastern Cyprus dated to the late Aquitanian to the early Serravallian (22.5 – 14.5 Ma). This sequence is carbonate-dominated and formed during the decoupling of the Mediterranean Sea and the Indian Ocean. It exhibits sedimentation with mass transport contribution from shallow water carbonates to deeper facies with phosphatization and bottom current (at intermediate depth) interactions. This succession traces both local subsidence and loss of a local carbonate factory. Additionally, it records a shift in bottom current energy and seafloor ventilation, which are an expected outcome of connectivity loss with the Indian Ocean.
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