Late Quaternary linkage of sedimentary records to three astronomical rhythms and the Asian monsoon, inferred from a coastal borehole in the south Bohai Sea, China

The Bohai Sea was formed by subsidence during the Cenozoic. Some 2000-3000. m of fluvial, lacustrine and marine sediments has been deposited in this basin. Previous studies focused mainly on the transgression history, with little examination of orbital variation in relation to other areas within the Asian monsoon domain.Here, we present the late Quaternary results of a new borehole in the south Bohai Sea. Optically stimulated luminescence and radiocarbon dating, which provide concordant age estimates, were employed to generate an initial chronology for the borehole. After refining the chronology through astronomical tuning, the results showed that: (1) the grain size variation represents Asian monsoon intensity which was dominated by both solar insolation (major) and global ice volume (minor) forcing; (2) the magnetic susceptibility indicates river incision processes which were sensitive to orbital tilt with influence from solar insolation; (3) the vegetation coverage responded to global ice volume coupled obliquity changes; and that (4) neither external nor internal factors could dominate the paleoenvironmental evolution on orbital timescales in an independent way, and they are both integrated in a complex pattern. We conclude that three different astronomical rhythms have affected coastal evolution, and that the sedimentary records in the south Bohai Sea, China, result from the nonlinear interaction and the complex response to driving processes.