Correlation of late Miocene to early Pliocene sequences between the Mediterranean and North Atlantic

Ocean Drilling Program (ODP) Site 982 in the North Atlantic contains a complete latest Miocene to early Pliocene section that was tuned to the astronomical timescale by correlating the record of gamma ray attenuation (GRA) bulk density to summer insolation at 65 degreesN and the benthic delta O-18 signal to orbital obliquity for the interval from 4.6 to 7.5 Ma. The astronomical tuning of the Site 982 record permits a direct bed-to-bed correlation to the cyclostratigraphy of Messinian sections in the Mediterranean [Krijgsman et al., 1999a, 2001]. The benthic delta O-18 signal at Site 982 records a latest Miocene glacial period that lasted from similar to6.26 to 5.50 Ma and consisted of 18 glacial-to-interglacial oscillations that were controlled by the 41-kyr cycle of obliquity. Although the intensification of glaciation at 6.26 Ma may have contributed to the restriction of the Mediterranean, it preceded the depositional onset of the lower evaporite unit at 5.96 Ma by some 300 kyr. The transition from Stage TG12 to TG11 at 5.5 Ma marks the end of the latest Miocene glacial period and precedes the Miocene/Pliocene boundary by 170 kyr. Although benthic delta O-18 values are relatively low and delta O-18 of bulk carbonate reaches a minimum at the Miocene/Pliocene boundary at 5.33 Ma, there is no single "event" that would indicate deglaciation and sea level rise as the cause of the reflooding of the Mediterranean. We conclude that glacioeustatic changes alone were not responsible for either the start or end of evaporite deposition during the Messinian, suggesting that tectonic or local climate changes in the Mediterranean region were the dominant cause(s).