Methods

Abstract

X-ray diffraction analyses Bulk sample XRD analyses were performed using a Bruker D-4 Endeavor X-ray diffractometer with a Vantec detector using Ni-filtered CuKα radiation. Instrument settings were Voltage = 40 kV. Current = 40 mA. Goniometer scan = 2°-70°2θ (air-dried samples). Step size = 0.01°2θ. Scan speed = 1.2°2θ/min. Count time = 0.5 s. Biostratigraphy Preliminary age assignments were based on biostratigraphic analyses of calcareous nannofossils, planktonic foraminifers, and radiolarians. Paleodepth interpretations were based on benthic foraminifers. The biostratigraphy is tied to the geomagnetic polarity timescale (GPTS) used for Expedition 342, which is based upon the timescale of Gradstein et al. (2012) (Fig. F5). The age of events based on the previous

Site U1405

“…S. delphix has a reported longevity of 100 k.y. (see Table T1 in the "Methods" chapter [Norris et al, 2014a]) and is found through a 27 m interval at Site U1405 (Samples 342-U1405A-19H-6, 46 cm, to 22H-4, 110 cm;175.66-201.80 mbsf). The Miocene/Oligocene boundary interval also contains at least one carbonate-rich layer with common to abundant Braarudosphaera (Fig.…”

“…The raw WRMS data for Hole U1405A were trimmed at section ends to remove edge effects; obviously spurious data points were also removed. We multiplied the WRMS data, which are in instrument units, by a factor of 0.577 × 10 -5 to convert to approximate SI volume susceptibilities (see "Paleomagnetism" in the "Methods" chapter [Norris et al, 2014a]). WRMS and DSMS data agree very well after this conversion, and we attribute small absolute differences to the fact that the conversion factor applied to the WRMS data is not constant downhole because of changes in core diameter and density; only discrete samples provide calibrated susceptibility values in SI units.…”

“…Plots of anisotropy of magnetic susceptibility vs. depth, Hole U1405A. Separation of eigenvalues is related to the shape and degree of the magnetic fabric (see "Paleomagnetism" in the "Methods" chapter [Norris et al, 2014a]). For example, if τ 1 and τ 2 are close or indistinguishable but distinct from τ 3 , then the bulk fabric is oblate.…”

Site U1404

“…Downhole variation in raw whole-round magnetic susceptibility (WRMS) and discrete sample magnetic susceptibility (DSMS) for Hole U1404A are shown in Figure F19. We multiplied the WRMS data, which are in instrument units, by a factor of 0.577 × 10 -5 to convert to approximate SI volume susceptibilities (see "Paleomagnetism" in the "Methods" chapter [Norris et al, 2014b]). WRMS and DSMS data agree very well after this conversion, and we attribute small absolute differences to the fact that the conversion factor applied to the WRMS data is not constant downhole because of changes in core diameter and density; only discrete samples provide calibrated susceptibility values in SI units.…”

“…Rew = reworked. See "Biostratigraphy" in the "Methods" chapter (Norris et al, 2014b) for preservation and abundance definitions. Table T8.…”