Developing a Holocene Chronostratigraphic Template for the North Atlantic: Paleomagnetic, Radiocarbon and Tephra chronostratigraphies from Iceland (MD99-2269) and East Greenland (MD99-2322)
Abstract
For paleomagnetism to reach its full chronostratigraphic potential, precise knowledge of the temporal variability of the full geomagnetic vector is required. Towards this rarely achieved goal, we present high-resolution Holocene sediment paleomagnetic direction and intensity records from the NW Iceland (MD99-2269: Lat 66.37.53 N, Long 23.51.16 W, water depth 365 m, length 2530 cm) and East Greenland margins (MD99-2322: Lat 67.08.18 N, Long 30.49.67W, water depth 714 m, length 2635 cm). The natural remanent magnetization (NRM) studied by progressive alternating field demagnetization of u-channel samples, preserves a strong, stable, single component magnetization. Other than coring induced inclination shallowing of 4 degrees and a linear trend in declination in MD99-2269, the directions of both records are consistent with each other and regional comparisons support a geomagnetic origin. Normalized intensity records are not clearly geomagnetic in the upper part of MD99-2269 possibly as a result of coring. Normalized intensity from MD99-2322 shows a more typical Holocene pattern and older (9-12 ka) highest accumulation rate part of both cores show a very similar pattern that correlates with the inverted cosmogenic isotope records supporting a geomagnetic interpretation. The chronostratigraphy is based on a multilevel approach. Twenty-five AMS radiocarbon dates from MD99-2269 are augmented by an additional 18 AMS radiocarbon dates from MD99-2322. Paleomagnetic synchronization of the two cores allows the radiocarbon dates to be combined into a single age to depth profile. The accuracy of the calibrated chronology using the standard ( 400 yr) marine reservoir correction was tested using eight terrestrially dated Icelandic tephras identified in MD99-2269. Temporal offsets are generally less than 200 yrs and are corrected for in our final age model. Comparison between paleointensity and independently dated cosmogenic isotope records further attest to the accuracy of the chronology. The use of these records as a North Atlantic (and beyond) chronostratigraphic template will be discussed.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2004
- Bibcode:
- 2004AGUFMGP43B0851S
- Keywords:
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- 1521 Paleointensity;
- 1522 Paleomagnetic secular variation