A reference time scale for Site U1385 (Shackleton Site) on the SW Iberian Margin
Hodell, D.; Lourens, L.; Crowhurst, S.; Konijnendijk, T.; Tjallingii, R.; Jiménez-Espejo, F; Skinner, L.; Tzedakise, P.C. (2015). A reference time scale for Site U1385 (Shackleton Site) on the SW Iberian Margin. Global Planet. Change 133: 49–64. dx.doi.org/10.1016/j.gloplacha.2015.07.002
In: Global and Planetary Change. Elsevier: Amsterdam; New York; Oxford; Tokyo. ISSN 0921-8181; e-ISSN 1872-6364, more
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| Author keywords |
IODP; Iberian Margin; Stratigraphic correlation; Millennial climate variability; Oxygen isotopes; Pleistocene; Cyclostratigraphy |
| Authors | | Top |
- Hodell, D.
- Lourens, L.
- Crowhurst, S.
- Konijnendijk, T.
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- Tjallingii, R., more
- Jiménez-Espejo, F
- Skinner, L.
- Tzedakise, P.C.
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| Abstract |
Weproduced a composite depth scale and chronology for Site U1385 on the SWIberianMargin. Using log(Ca/Ti)measured by core scanning XRF at 1-cm resolution in all holes, a composite section was constructed to166.5 meter composite depth (mcd) that corrects for stretching and squeezing in each core. Oxygen isotopesof benthic foraminifera were correlated to a stacked d18O reference signal (LR04) to produce an oxygen isotopestratigraphy and age model.Variations in sediment color contain very strong precession signals at Site U1385, and the amplitude modulationof these cycles provides a powerful tool for developing an orbitally-tuned agemodel.We tuned the U1385 recordby correlating peaks in L* to the local summer insolation maxima at 37°N. The benthic d18O record of Site U1385,when placed on the tuned agemodel, generally agrees with other time scaleswithin their respective chronologicuncertainties.The age model is transferred to down-core data to produce a continuous time series of log(Ca/Ti) that reflectrelative changes of biogenic carbonate and detrital sediment. Biogenic carbonate increases during interglacialand interstadial climate states and decreases during glacial and stadial periods. Much of the variance in thelog(Ca/Ti) is explained by a linear combination of orbital frequencies (precession, tilt and eccentricity), whereasthe residual signal reflects suborbital climate variability. The strong correlation between suborbital log(Ca/Ti)variability and Greenland temperature over the last glacial cycle at Site U1385 suggests that this signal can beused as a proxy for millennial-scale climate variability over the past 1.5 Ma.Millennial climate variability, as expressed by log(Ca/Ti) at Site U1385, was a persistent feature of glacial climatesover the past 1.5Ma, including glacial periods of the early Pleistocene (‘41-kyrworld’)when boundary conditionsdiffered significantly from those of the late Pleistocene (‘100-kyr world’). Suborbital variability was suppressedduring interglacial stages and enhanced during glacial periods, especially when benthic d18O surpassed ~3.3–3.5‰. Each glacial inception was marked by appearance of strong millennial variability and each deglaciation |
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