North Atlantic palaeointensity stack since 75ka (NAPIS–75) and the duration of the Laschamp event

Abstract

Six relative palaeointensity records from the north Atlantic Ocean were stacked together to produce a new record for the last 75 kyr (NAPIS-75). Five of these records have been previously correlated at millennial scale and placed on the GISP2 age scale, the sixth record was tied to the others using magnetic susceptibility. From 75 ka the eld strength exhibits some oscillations, with a rst minimum ca. 65 ka, followed by a progressive increase to a broad maximum centred at ca. 48 ka. There is then a well-marked low at 40 ka, corresponding to the directional anomaly of the Laschamp event. Another intensity low, observed at ca. 34 ka, corresponds in age to the Mono Lake event. After a high at 33 ka and two lows at 30 and 24 ka with a broad maximum between, the eld strength seems to slowly increase to the upper limit of the studied interval. In the 10{20 kyr interval some di¬erences exist between individual records, and ne-scale details are not always resolved. In the 20{75 kyr interval, on the other hand, well-resolved millennial-scale features are superimposed to the broader trends. The duration of the Laschamp event, which is recorded directionally in ve cores, appears to be about 1500 years, consistent with a recent suggestion on the origin of geomagnetic excursions.

A high resolution authigenic 10Be/9Be record of geomagnetic moment variations over the last 300 ka from sedimentary cores of the Portuguese margin

“…The minimum VDM at 41 ka BP of interval I well corresponds to interval A identified as the Laschamps excursion recorded in lavas flows from France [43] and Iceland [44], as well as in lacustrine [45] and marine sediments [46].…”

Dominant Northern Hemisphere climate control over millennial-scale glacial sea-level variability

“…We correlated our GeoB 5844-2 magnetic paleointensity record to the North Atlantic paleointensity stack (NAPIS) (Laj et al, 2000;Stoner et al, 2002) (Fig. 3).…”

“…For paleomagnetic investigations, the sediment core has been sampled using cubic (20 Â 20 Â 15 mm) plastic boxes ARTICLE IN PRESS show 14 C-AMS datings and filled blue circles the correlation of our magnetic paleointensity record to the North Atlantic paleointensity stack (NAPIS) (Laj et al, 2000;Stoner et al, 2002) (Fig. 3 and Table 1).…”

“…3. Correlation of the GeoB 5844-2 magnetic paleointensity record to the North Atlantic paleointensity stack (NAPIS) (Laj et al, 2000;Stoner et al, 2002). Tie points used for the best fit are marked by vertical arrows and include the Laschamp event at $41 ka ($42 ka on the SFCP timescale), one paleointensity maxima at $47 ka BP (49 ka on the SFCP timescale), and a paleointensity minimum at $64.5 ka BP (66 ka on the SFCP timescale) that has been previously found in several North Atlantic records and described as Norwegian-Greenland Sea event (Nowaczyk and Frederichs, 1999).…”

Radiocarbon calibration ? past, present and future

“…200‰ on the general trend of the data. This could be a geomagnetic excursion like Mono Lake [24]. At older ages, the D 14 C tends to go to zero which means there is no extra 14 C in the atmosphere compared with the present.…”