Description: Integrated Ocean Drilling Program (IODP) Expedition 342 recovered exceptional Paleogene to early Neogene sedimentary archives from clay-rich sediments in the northwest Atlantic Ocean. These archives present an opportunity to study Cenozoic climate in a highly sensitive region at often unprecedented resolution. Such studies require continuous records in the depth and time domains. Using records from multiple adjacent drilled holes, intervals within consecutive cores are typically spliced into a single composite record on board the R/V JOIDES Resolution using high-resolution physical properties data sets acquired before the cores are split. The highly dynamic nature of the sediment drifts drilled during Expedition 342 and the modest amplitude of variance in the physical property records made it possible to construct only highly tentative initial working splices, which require extensive postexpedition follow-up work. Postexpedition, high-resolution X-ray fluorescence (XRF) core scanning data enabled the construction of a preliminary composite depth scale and splice. Here, we present the revised composite depth scale and splice for IODP Site U1406, predominantly constructed using detailed hole-to-hole correlations of newly generated high-resolution XRF data and revisions of the initial XRF data set. The revised composite depth scale and splice serve as a reference framework for future research on Site U1406 sediments.

Description: Astronomical tuning of sediment sequences requires both unambiguous cycle-pattern recognition in climate proxy records and astronomical solutions, and independent information about the phase relationship between these two. Here we present two different astronomically tuned age models for the Oligocene-Miocene Transition (OMT) from Integrated Ocean Drilling Program Site U1334 (equatorial Pacific Ocean) to assess the effect tuning has on astronomically calibrated ages and the geologic time scale. These alternative age models (from ~22 to ~24 Ma) are based on different tunings between proxy records and eccentricity: the first age model is based on an aligning CaCO3 weight (wt%) to Earth's orbital eccentricity, the second age model is based on a direct age calibration of benthic foraminiferal stable carbon isotope ratios (d13C) to eccentricity. To independently test which tuned age model and associated tuning assumptions is in best agreement with independent ages based on tectonic plate-pair spreading rates, we assign our tuned ages to the magnetostratigraphic reversals identified in deep-marine magnetic anomaly profiles. Subsequently, we compute tectonic plate-pair spreading rates based on the tuned ages. The resultant, alternative spreading rate histories indicate that the CaCO3 tuned age model is most consistent with a conservative assumption of constant, or linearly changing, spreading rates. The CaCO3 tuned age model thus provides robust ages and durations for polarity chrons C6Bn.1n-C6Cn.1r, which are not based on astronomical tuning in the latest iteration of the Geologic Time Scale. Furthermore, it provides independent evidence that the relatively large (several 10,000 years) time lags documented in the benthic foraminiferal isotope records relative to orbital eccentricity, constitute a real feature of the Oligocene-Miocene climate system and carbon cycle. The age constraints from Site U1334 thus provide independent evidence that the delayed responses of the Oligocene-Miocene climate-cryosphere system and carbon cycle resulted from highly nonlinear feedbacks to astronomical forcing.