A reference time scale for Site U1385 (Shackleton Site) on the SW Iberian Margin

We produced a composite depth scale and chronology for Site U1385 on the SW Iberian Margin. Using log(Ca/Ti) measured by core scanning XRF at 1-cm resolution in all holes, a composite section was constructed to 166.5meter composite depth (mcd) that corrects for stretching and squeezing in each core....

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Bibliographic Details
Published in:	Global and planetary change Vol. 133; pp. 49 - 64
Main Authors:	Hodell, D., Lourens, L., Crowhurst, S., Konijnendijk, T., Tjallingii, R., Jiménez-Espejo, F., Skinner, L., Tzedakis, P.C., Abrantes, Fatima, Acton, Gary D., Alvarez Zarikian, Carlos A., Bahr, André, Balestra, Barbara, Barranco, Estefanìa Llave, Carrara, Gabriela, Ducassou, Emmanuelle, Flood, Roger D., Flores, José-Abel, Furota, Satoshi, Grimalt, Joan, Grunert, Patrick, Hernández-Molina, Javier, Kim, Jin Kyoung, Krissek, Lawrence A., Kuroda, Junichiro, Li, Baohua, Lofi, Johanna, Margari, Vasiliki, Martrat, Belen, Miller, Madeline D., Nanayama, Futoshi, Nishida, Naohisa, Richter, Carl, Rodrigues, Teresa, Rodríguez-Tovar, Francisco J., Roque, Ana Cristina Freixo, Sanchez Goñi, Maria F., Sierro Sánchez, Francisco J., Singh, Arun D., Sloss, Craig R., Stow, Dorrik A.V., Takashimizu, Yasuhiro, Tzanova, Alexandrina, Voelker, Antje, Xuan, Chuang, Williams, Trevor
Format:	Journal Article
Language:	English
Published:	Elsevier B.V 01-10-2015 Elsevier
Subjects:	Cyclostratigraphy Environmental Sciences Global Changes Iberian Margin IODP Millennial climate variability Oxygen isotopes Pleistocene Stratigraphic correlation IODP Cyclostratigraphy Iberian Margin Millennial climate variability Stratigraphic correlation Oxygen isotopes Pleistocene
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Summary:	We produced a composite depth scale and chronology for Site U1385 on the SW Iberian Margin. Using log(Ca/Ti) measured by core scanning XRF at 1-cm resolution in all holes, a composite section was constructed to 166.5meter composite depth (mcd) that corrects for stretching and squeezing in each core. Oxygen isotopes of benthic foraminifera were correlated to a stacked δ18O reference signal (LR04) to produce an oxygen isotope stratigraphy and age model. Variations in sediment color contain very strong precession signals at Site U1385, and the amplitude modulation of these cycles provides a powerful tool for developing an orbitally-tuned age model. We tuned the U1385 record by correlating peaks in L* to the local summer insolation maxima at 37°N. The benthic δ18O record of Site U1385, when placed on the tuned age model, generally agrees with other time scales within their respective chronologic uncertainties. The age model is transferred to down-core data to produce a continuous time series of log(Ca/Ti) that reflect relative changes of biogenic carbonate and detrital sediment. Biogenic carbonate increases during interglacial and interstadial climate states and decreases during glacial and stadial periods. Much of the variance in the log(Ca/Ti) is explained by a linear combination of orbital frequencies (precession, tilt and eccentricity), whereas the 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 be used as a proxy for millennial-scale climate variability over the past 1.5Ma. Millennial climate variability, as expressed by log(Ca/Ti) at Site U1385, was a persistent feature of glacial climates over the past 1.5Ma, including glacial periods of the early Pleistocene (‘41-kyr world’) when boundary conditions differed significantly from those of the late Pleistocene (‘100-kyr world’). Suborbital variability was suppressed during interglacial stages and enhanced during glacial periods, especially when benthic δ18O surpassed ~3.3–3.5‰. Each glacial inception was marked by appearance of strong millennial variability and each deglaciation was preceded by a terminal stadial event. Suborbital variability may be a symptomatic feature of glacial climate or, alternatively, may play a more active role in the inception and/or termination of glacial cycles. [Display omitted] •Construction of a state-of-the-art composite section and chronology for Site U1385 to underpin paleoceanographic studies•Evaluation of various age models used for the middle-to-late Pleistocene•Millennial-scale variability was an intrinsic feature of glacial climate over the past 1.5Ma.•Enhanced suborbital climate variability marks the onset and termination of each glacial–interglacial cycle.
ISSN:	0921-8181 1872-6364
DOI:	10.1016/j.gloplacha.2015.07.002