We report a high-resolution stable isotope, carbonate, magnetostratigraphic, and biostratigraphic record from a 175-m drill core from the Sale Briqueterie, which is part of the Bou Regreg section in northwestern Morocco. The Sale drill core spans the interval from paleomagnetic Chron C4n partim to C3r (earliest Gilbert), which represents the time leading up to and including the isolation and desiccation of the Mediterranean (i.e., the Messinian salinity crisis). During Chrons C3An and C3Ar (6.935 to 5.894 Ma) the isotope and carbonate signals display quasi-periodic variations with estimated periods of 40 and 100 kyr, respectively. We interpret the 40-kyr delta(18)O variations as reflecting changes in global ice volume caused by obliquity-induced changes (41 kyr) in solar insolation in polar regions. The 100-kyr carbonate variations probably represent long-term modulation of the amplitude of the precessional cycle (similar to 21 kyr), which is not resolved by our sampling frequency. The cyclic nature of the oxygen isotope signal permits us to extend the isotope nomenclature of Shackleton et al. (1994a) from stage TG24 in Chron C3r (earliest Gilbert) to stage C3Ar.delta(18)O.18 at the base of Chron C3Ar (6.935 Ma). A major change in paleoceanographic conditions is recorded across the Tortonian/Messinian boundary, which we correlate to Chron C3Bn at 7.04 Ma. Benthic foraminiferal delta(18)O values increased by an average of 0.4 parts per thousand in two steps at 7.17 Ma and 6.8 Ma and delta(13)C values decreased by 0.7-0.8 parts per thousand between 7.1 and 6.8 Ma, representing the late Miocene carbon shift. The first step in delta(18)O values coincides with an inferred reversal in deep water circulation through the Rifian Corridor, and the second correlates with the base of the Tripoli Formation and onset of ''crisis conditions'' in the Mediterranean. We suggest that the increase in delta(18)O values represents, at least in part, an increase in global ice volume that lowered sea level and contributed to the establishment of a negative water budget in the Mediterranean. Average delta(18)O values remained high throughout most of Chrons C3Ar and C3An, reaching maximum delta(18)O values during isotope stages TG20 and 22 in Chron C3r (earliest Gilbert). The glacio-eustatic falls associated with these events may have resulted in the complete isolation of the Mediterranean from the world ocean (Shackleton et al., 1994a). Following stage TG12 in the Sale record, there exists a trend toward progressively lower delta(18)O values that may represent a series of marine transgressions that eventually reflooded the Mediterranean and ended the Salinity Crisis.
Pv965Times Cited:81Cited References Count:99