Long-Term Character of Paleomagnetic Secular Variation from the Southern Hemisphere over the last Glacial Cycle – Evidence from ODP Leg 202- Chile Margin

English Abstract:

Paleomagnetic secular variation (PSV) records from Sites 1233-1235, ODP Leg 202, Chile Margin (35°-40°S) provide a reproducible look at full-vector PSV variability (both intensity and directions) for the last 70,000 years. The paleointensity records correlate strongly with equatorial paleointensity records from Indonesia and mid-latitude Northern Hemisphere records from the Atlantic Ocean. But, beyond that, there are significant differences in the regional character of PSV in the various regions. Indonesia and the North Atlantic show a Laschamp excursion that is Class 1, characterized by out-of-phase millennial-scale cyclicity, while Chile sees a Laschamp Excursion that is Class II, characterized by in-phase directional variations and local full-polarity reversal. Indonesia and Chile see a Class 1 excursion in MIS 4 (~62, ka), but none is noted in the North Atlantic Ocean. PSV in Chile and the North Atlantic follows a distinctive decrease in amplitude for 30,000 years after the Laschamp Excursion; but it is not obvious that such is noted in Indonesia. These directional differences occur within a context of similar intensity variations. This spatial character should provide insight into the spatial-scale of coherent flux regeneration within the outer core.