Precessional Drivers of Late Miocene Mediterranean Sedimentary Sequences: African Summer Monsoon and Atlantic Winter Storm Tracks

Abstract

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.

Precessional Cyclicity of Seawater Pb Isotopes in the Late Miocene Mediterranean

“…These relationships suggest that while fluvial inputs may have influenced seawater Pb isotope compositions, they are not responsible for the more radiogenic compositions at insolation minima. This is consistent with the relatively small changes in the hydrologic budget across precessional cycles expected for the Western Mediterranean (Marzocchi et al, ; Modestou et al, ).…”

“…Moreover, there are significant differences in the temporal occurrence of several proxies between Mediterranean sub‐basins; for example, sapropels in the Western Mediterranean are often less distinct, spatially less extensive, and sometimes missing entirely in the Plio‐Pleistocene compared to the Eastern Mediterranean (Murat, ). The east‐west spatial discrepancy is due to the fact that the intense increase in monsoon‐driven runoff during insolation maxima is primarily channeled into the eastern basin (Marzocchi et al, ; Emeis, Struck, et al, ; Rossignol‐Strick, ), suggesting different processes are responsible for sapropel development in the west (Emeis, Struck, et al, ; Murat, ). Finally, substantial changes in salinity occurred in the Mediterranean during the Messinian Salinity Crisis (MSC; 5.971–5.333 Ma; Krijgsman et al, ; Lourens et al, ; Manzi et al, ), which obscured normal marine sedimentation and the biological activity moderating organic proxies altogether.…”

The Miocene: The Future of the Past

“…In the study of Goldner et al (2014a) for the early to middle Miocene, orbital changes were found to improve the model-data mismatch, although the improvement was small and localized. The role of orbital forcing in the late Miocene climate (8 Ma) has been investigated in three coupled climate model studies (Marzocchi et al, 2019(Marzocchi et al, , 2015D. Simon et al, 2017).…”

“…(2014a) for the early to middle Miocene, orbital changes were found to improve the model‐data mismatch, although the improvement was small and localized. The role of orbital forcing in the late Miocene climate (8 Ma) has been investigated in three coupled climate model studies (Marzocchi et al., 2019, 2015; D. Simon et al., 2017). They found that the orbital forcing does not change the mean global surface temperature greatly, but can have substantial regional impact on both precipitation and temperature.…”

Mediterranean Overflow Over the Last 250 kyr: Freshwater Forcing From the Tropics to the Ice Sheets

“…Northward latitudinal migrations of the Intertropical Convergence Zone (ITCZ) and intense monsoons in Africa and Asia have been related to large summer Nile discharges (Castañeda et al, 2016;Revel et al, 2010) and sapropel formation (Rohling & Hilgen, 1991;Rohling et al, 2015;Rossignol-Strick et al, 1982). Events of enhanced Nile discharge were also synchronous to periods of increase annual rainfall in the northern and southern Mediterranean catchment areas (Bar-Matthews et al, 2000;Toucanne, Minto'o, et al, 2015;Tzedakis, 2005;Tzedakis et al, 2002Tzedakis et al, , 2009Wagner et al, 2019;Zanchetta et al, 2007), showing the strong coupling between the low and midlatitude hydrological cycle (Bosmans et al, 2015(Bosmans et al, , 2020Kutzbach et al, 2014;Marzocchi et al, 2019). Our data thus confirms the strong link between precession minima, instense Asian and African monsoons, sapropels and weak MOW at Gibraltar.…”