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The 87Sr/86Sr ratio is a proxy of the hydrologic structure of marginal basins characterized by the mixing between marine and continental waters. This reliable paleoceanographic and paleoclimatic tool is considered a key to the reconstruction of high‐amplitude hydrologic changes that governed the evolution of the Mediterranean region during the Messinian salinity crisis (MSC), when reduced connections with the global ocean resulted in the deposition of the most studied Earth's salt giant. Paleohydrological dynamics leading to the deposition of the Primary Lower Gypsum during the first stage of the MSC were revealed by the study of the 87Sr/86Sr composition of 114 samples from the Vena del Gesso basin (Northern Apennines, Italy). The analysis of seven high‐resolution 87Sr/86Sr profiles from individual gypsum beds suggests a climatic influence of precessional‐scale orbital parameters during evaporite deposition. The variations of Sr isotope ratios over time indicate that gypsum precipitation started from a seawater body dominated by continental contributions, followed by a relative increase of marine input. The overall results show a gradual upward detachment from the global ocean 87Sr/86Sr curve, with crucial steps corresponding to the most extreme eccentricity minima, suggesting an orbital influence on the hydrological balance of the basin. Given the sedimentological and geochemical analogies shared by the Mediterranean marginal basins that hosted the Primary Lower Gypsum deposition, the 87Sr/86Sr evolution of the Vena del Gesso basin may be considered as indicative of Mediterranean‐scale hydrologic dynamics, driven by gradual reduction of exchanges with the Atlantic and variable freshwater input. High‐resolution Sr isotope data record orbitally forced climate control on basin hydrology at different time scales87Sr/86Sr profiles highlight recurrent precessional‐scale hydrological oscillationsThe stepwise divergence of the 87Sr/86Sr signal from the global ocean trend suggests gradual reduction of Mediterranean‐Atlantic exchanges

An integrated micropaleontologic, magnetostratigraphic and cyclostratigraphic investigation of the Tokhni composite section (Southern Cyprus Island, Eastern Mediterranean) refines the previously published age model and paleoenvironmental interpretation particularly concerning its uppermost pre-Messinian Salinity Crisis interval (pre-MSC), between 6.46 and 5.97 Ma. This section is characterized by a precessionpaced alternation of red shales and limestones, which correlate with insolation maxima and minima on the basis of their d18 O signatures and calcareous nannofossil assemblages. The planktonic foraminifer and magnetostratigraphic events permit the tuning of the sedimentary cycles to the 65° N summer insolation curve and to the Mediterranean pre-evaporitic reference sections. The upper bathyal sedimentary succession of the Tokhni composite section records paleoceanographic changes at 6.4 and 6.1 Ma, indicating increasingly stressed conditions both at the sea floor and in the water column. Compared to the Western Mediterranean pre-MSC successions, we observe less severe sea floor anoxic conditions at times of insolation maxima and higher salinity surface and bottom waters at times of insolation minima. Moreover, from 6.1 Ma to the MSC onset we observe a progressively increase of continental-derived waters, which was likely caused by a tectonic pulse. The MSC onset at 5.97 Ma is marked by the deposition of clastic carbonates rather than primary evaporitic facies and is approximated by the last recovery of foraminifera, the abundance peaks of Helico sphaera carteri and Umbilicosphaera rotula and the decrease of the87/86 Sr. The MSC onset is recorded two cycles below the Messinian erosional surface (MES, 5.60 Ma) and the overlying clastic evaporites, suggesting a hiatus of approximately 350 kyr.

We present a new 87Sr/86Sr curve for the time interval between 6.5 and 5.5 Ma of the Ain El Beida section (AEB, Atlantic side of Morocco). The location and the precessional‐scale resolution of our curve allow to investigate the possible relationships between global paleoclimatic and palaeoceanographic trends and the high‐amplitude hydrological changes of the Mediterranean during the Messinian salinity crisis (MSC). The values, obtained from planktic foraminifers, plot in the upper portion of the global ocean curve and show long‐ (at eccentricity scale) and short‐term (precessional scale) oscillations; the latter are more evident during the maximum of eccentricity for both the 100 and 400 ka components, between 6.00 and 5.85 Ma. Negative 87Sr/86Sr anomalies are observed at insolation minima in phase with δ18O maxima, marking the glacial stages from TG34 to TG26. It is unclear whether these oscillations originated from local (river runoff) or global (glacial/interglacial) climatic forcing. Conversely, the evaporites of the coeval Primary Lower Gypsum (5.97–5.62 Ma) accumulated in the Mediterranean at insolation minima show positive anomalies at glacial stages TG32, 30, 28, and 26. Such an opposite trend is possibly related to the greater sensitivity of the Mediterranean Sea to river runoff during insolation maxima compared to the global ocean, as recorded at the Moroccan Atlantic margin. These observations and the deviation toward lower values of the Mediterranean Sr isotope curve starting at around 6.5 Ma, support the hypothesis of a progressive restriction of the Atlantic connections since the early Messinian, leading to the MSC. A new planktic foraminifers‐based high‐resolution 87Sr/86Sr reference curve for the Atlantic (Ain El Beida section, Morocco) is providedLong‐ (at eccentricity scale) and short‐term (precessional scale) oscillations characterize the 87Sr/86Sr curveNegative 87Sr/86Sr anomalies are observed at insolation minima in phase with marine isotopic glacial stages from TG34 to TG26 A new planktic foraminifers‐based high‐resolution 87Sr/86Sr reference curve for the Atlantic (Ain El Beida section, Morocco) is provided Long‐ (at eccentricity scale) and short‐term (precessional scale) oscillations characterize the 87Sr/86Sr curve Negative 87Sr/86Sr anomalies are observed at insolation minima in phase with marine isotopic glacial stages from TG34 to TG26