FIRST LATE QUATERNARY PALEOSECULAR VARIATION (PSV) & RELATIVE PALEOINTENSITY (RPI) CURVE FROM SCOTLAND, UK

Abstract:

The first PSV curve for the UK covering the last 19,000 years has been generated by integrating state-of-the-art paleomagnetic, rock magnetic and geochemical studies with tephrochronology and radiocarbon dating of a sedimentary sequence from a small glacial lake in the Central Belt of Scotland. This also constitutes the first continuous record of relative paleointensities during The Holocene for Scotland, representing a valuable piece for the puzzle of the Geodynamo behaviour in the North Atlantic region.

Published PSV records from North America, North Atlantic and Northern Europe are consistent with direct observations and models of two regions of concentrated geomagnetic flux at the core-mantle boundary beneath Canada and Siberia; they imply that the Canadian flux lobe has weakened while the Siberian flux lobe has increased in strength at least for the last 2,000 years. Large fluctuations in RPIs joined by dramatic oscillations in declination for the Holocene section of our PSV curve (fig. 1 Anomalies A & B) agree with such North Atlantic records; furthermore, our results suggest that oscillations in strength between both flux lobes could have occurred for the last 10,000 years (fig. 1 Anomalies A to D); while the largest Holocene anomaly at ~4.5 ka to ~3.4ka (fig. 1 Anomaly B) could be related to the developing of a third low-latitude region of concentrated geomagnetic flux close to the Mediterranean, suggested by recent studies.

The present Scotland record exhibits two intervals of exceptional deviation in direction at ~18.3ka to ~16ka and ~15ka to ~12.8ka. The deepest interval displays anomalous shallow inclinations joined by the largest oscillation in declination, with a maximum of 77-degree deviation (fig. 1 Anomaly F), which agrees with the little known Hilina Pali Excursion (~22ka to ~17ka). The geomagnetic anomaly close to the end of The Pleistocene exhibits the largest drop of inclination, from present-day values to negative inclinations, while the declination presents oscillations over 50-degrees (fig. 1 Anomaly E). These abrupt and dramatic variations are consistent with the controversial Gothenburg Excursion, originally reported in sediments from the Scandinavian Glacial Interstadial and observed in North American glacial lakes (with poorly constrained ages from 14ka to 7.6ka).