Chronostratigraphy and stable isotopes of IODP Site 339-U1385

DOI

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 166.5 meter composite depth (mcd) that corrects for stretching and squeezing in each core. Oxygen isotopes of benthic foraminifera were correlated to a stacked d18O 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 d18O 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 1.5 Ma. Millennial climate variability, as expressed by log(Ca/Ti) at Site U1385, was a persistent feature of glacial climates over the past 1.5 Ma, 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 d18O 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.

Supplement to: Hodell, David A; Lourens, Lucas Joost; Crowhurst, Simon J; Konijnendijk, Theodoor Yuri Martij; Tjallingii, Rik; Jiménez-Espejo, Francisco Jose; Skinner, Luke C; Tzedakis, Polychronis C (2015): A reference time scale for Site U1385 (Shackleton Site) on the SW Iberian Margin. Global and Planetary Change, 133, 49-64

Identifier
DOI https://doi.org/10.1594/PANGAEA.872083
Related Identifier https://doi.org/10.1016/j.gloplacha.2015.07.002
Related Identifier https://doi.org/10.25921/EK7W-V171
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.872083
Provenance
Creator Hodell, David A ORCID logo; Lourens, Lucas Joost ORCID logo; Crowhurst, Simon J; Konijnendijk, Theodoor Yuri Martij; Tjallingii, Rik ORCID logo; Jiménez-Espejo, Francisco Jose; Skinner, Luke C ORCID logo; Tzedakis, Polychronis C ORCID logo
Publisher PANGAEA
Publication Year 2015
Rights Creative Commons Attribution 3.0 Unported; https://creativecommons.org/licenses/by/3.0/
OpenAccess true
Representation
Language English
Resource Type Supplementary Publication Series of Datasets; Collection
Format application/zip
Size 14 datasets
Discipline Earth System Research
Spatial Coverage (-10.126W, 37.571S, -10.126E, 37.571N)