A radiometric calibration of the SPECMAP timescale

摘要: The astronomical theory of climate change asserts that Earth's is affected by changes in its orbit, which vary the seasonal and latitudinal distribution solar radiation. This basis orbitally tuned SPECMAP timescale. A key constraint for this important chronology was mid-point Penultimate Deglaciation, initially dated to 127,000 years ago. Recent work suggests event may be considerably older, casting doubt on theory, timescale, accuracy chronologies. Difficulties with U/Th coral dating sea-level events have impeded progress problem, because most corals are not closed systems. Here, we use a new approach corrects open-system behavior produces curve sufficient resolution confidently correlate over last 240,000 years, permitting reassessment both critical central tenet theory. High-precision ages 24 oxygen isotope provide 240,000-year marine δ18O records independent orbital tuning assumptions. Although there appear significant differences between radiometric timescales near lastglacial maximum at Marine Isotope Stage 7/6 boundary, comparison identical suggest timescale quite accurate errors were, general, overestimated. Despite suborbital complexity, cyclicity clearly evident our record. High-amplitude oscillations periods greater than ∼20,000 very close phase summer insolation Northern Hemisphere. cannot uniquely tied specific season or latitude forcing, simplest explanation long-period, high-amplitude linked Hemisphere forcing. These results validate principles such generally robust.