Abstract
Recent high-resolution data reveal centennial to millennial scale features of magneto-climato- stratigraphy across a geomagnetic reversal. A drill core from Osaka Bay documents two sea-level highstands correlated with precession-related geochemical records of marine isotope stage (MIS) 19. The Matuyama-Brunhes (MB) polarity transition began with a short normal polarity reversal episode that occurred before sea-level highstand 19.3, and terminated with multiple rapid reversals, predating lowstand 19.2. The thermal maximum occurred about 4,000 years after the highest 19.3 sea-level, just post- dating the MB reversal. Similar magnetostrati- graphic features are observed in MB transition records from Chinese loess sediments, Pleistocene deposits in Sangiran, Indonesia, and deep-sea sediments that document precession-related signals. The thermal maximum just postdating the MB reversal is also observed in Lake Baikal, the Jordan Valley, and on the Mediterranean coast. A very similar post-reversal warming, again delayed by ∼4,000yr, is observed across the Lower Jaramillo reversal in MIS31. We conclude that the delay in warming relative to sea-level highstand was due to a cloud-albedo effect induced by an increase in galactic cosmic ray flux during an extremely low magnetic field intensity interval.
