Response of Iberian Margin sediments to orbital and suborbital forcing over the past 420 ka
Article first published online: 27 MAR 2013
©2013. American Geophysical Union. All Rights Reserved.
Volume 28, Issue 1, pages 185–199, March 2013
How to Cite
2013), Response of Iberian Margin sediments to orbital and suborbital forcing over the past 420 ka, Paleoceanography, 28, 185–199, doi:10.1002/palo.20017., , , , , , , , and (
- Issue published online: 22 APR 2013
- Article first published online: 27 MAR 2013
- Accepted manuscript online: 27 JAN 2013 11:11PM EST
- Manuscript Accepted: 23 JAN 2013
- Manuscript Revised: 18 JAN 2013
- Manuscript Received: 4 SEP 2012
- Iberian Margin;
- orbital forcing;
- millennial variability
 Here we report 420 kyr long records of sediment geochemical and color variations from the southwestern Iberian Margin. We synchronized the Iberian Margin sediment record to Antarctic ice cores and speleothem records on millennial time scales and investigated the phase responses relative to orbital forcing of multiple proxy records available from these cores. Iberian Margin sediments contain strong precession power. Sediment “redness” (a* and 570–560 nm) and the ratio of long-chain alcohols to n-alkanes (C26OH/(C26OH + C29)) are highly coherent and in-phase with precession. Redder layers and more oxidizing conditions (low alcohol ratio) occur near precession minima (summer insolation maxima). We suggest these proxies respond rapidly to low-latitude insolation forcing by wind-driven processes (e.g., dust transport, upwelling, precipitation). Most Iberian Margin sediment parameters lag obliquity maxima by 7–8 ka, indicating a consistent linear response to insolation forcing at obliquity frequencies driven mainly by high-latitude processes. Although the lengths of the time series are short (420 ka) for detecting 100 kyr eccentricity cycles, the phase relationships support those obtained by Shackleton . Antarctic temperature and the Iberian Margin alcohol ratios (C26OH/(C26OH + C29)) lead eccentricity maxima by 6 kyr, with lower ratios (increased oxygenation) occurring at eccentricity maxima. CO2, CH4, and Iberian SST are nearly in phase with eccentricity, and minimum ice volume (as inferred from Pacific δ18Oseawater) lags eccentricity maxima by 10 kyr. The phase relationships derived in this study continue to support a potential role of the Earth's carbon cycle in contributing to the 100 kyr cycle.