Expedition 395 methods

Ross E. Parnell-Turner, Anne Briais, Leah J. Levay, Ying Cui, Anita Di Chiara, Justin P Dodd, Tom Dunkley Jones, Deepa Dwyer, Deborah E Eason, Sarah A Friedman, et al.

► To cite this version:

Ross E. Parnell-Turner, Anne Briais, Leah J. Levay, Ying Cui, Anita Di Chiara, et al. Expedition 395 methods. Reykjanes Mantle Convection and Climate, 395, 2025, Proceedings of the International Ocean Discovery Program, 978-1-954252-88-2. 10.14379/iodp.proc.395.102.2025. hal-05404805

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# Expedition 395 methods<fnref n="1" />

## Contents

1 Introduction

10 Lithology

16 Igneous petrology

23 Alteration petrology and structural geology

25 Micropaleontology

33 Physical properties

39 Stratigraphic correlation

42 Paleomagnetism

47 Geochemistry and microbiology

56 Downhole measurements

66 Age model

67 References

## Keywords

International Ocean Discovery Program, IODP, *JOIDES Resolution*, Expedition 395, Expedition 384, Expedition 395C, Reykjanes Mantle Convection and Climate, Earth Connections, Earth in Motion, Site U1554, Site U1555, Site U1562, Site U1563, Site U1564, Site U1602, contourite drifts, mantle plume, hydrothermal alteration, oceanic gateways, climate record, Northern Hemisphere glaciation

## Core descriptions

## Supplementary material

## References (RIS)

MS 395-102

Published 21 January 2025

Funded by NSF OCE1326927, ECORD, and JAMSTEC

R.E. Parnell-Turner, A. Briais, L.J. LeVay, Y. Cui, A. Di Chiara, J.P. Dodd, T. Dunkley Jones, D. Dwyer, D.E. Eason, S.A. Friedman, S.R. Hemming, K. Hochmuth, H. Ibrahim, C. Jasper, B.T. Karatsolis, S. Lee, D.E. LeBlanc, M.R. Lindsay, D.D. McNamara, S.E. Modestou, B. Murton, S. OConnell, G.T. Pasquet, P.N. Pearson, S.P. Qian, Y. Rosenthal, S. Satolli, M. Sinnesael, T. Suzuki, T. Thulasi Doss, N.J. White, T. Wu, and A. Yang Yang<fnref n="2" />

# 1. Introduction

This chapter provides an overview of the procedures and methods employed for coring operations and in the shipboard laboratories of the research vessel (R/V) *JOIDES Resolution* during International Ocean Discovery Program (IODP) Expeditions 384, 395C, and 395. Hereafter, the expeditions will be known jointly as Expedition 395 unless otherwise specified. The laboratory information applies only to shipboard work described in the Expedition Report section of the *Expedition 395 Proceedings of the International Ocean Discovery Program* volume that used the shipboard sample registry, imaging and analytical instruments, core description tools, and the Laboratory Information Management System (LIMS) database. Methods used by investigators for postcruise shore-based analyses of Expedition 395 project data will be documented in separate publications.

Shipboard and shore-based scientists contributed to this volume with the following primary responsibilities (authors are listed in alphabetical order; see **Expedition 395 scientists** for contact information):

* Summary chapter: Expedition 395 Scientists

* Methods and site chapters:

* Background and objectives: A. Briais, R. Parnell-Turner

* Operations: K. Grigar, L. LeVay

* Lithostratigraphy: H. Ibrahim, C. Jasper, D. LeBlanc, S. Lee, S. Modestou, S. OConnell, T. Thulasi Doss

* Igneous petrology: D. Eason, B. Murton, N. White, T. Wu

* Alteration petrology and structural geology: D. McNamara, G. Pasquet

* Micropaleontology: T. Dunkley Jones, B. Karatsolis, P. Pearson, T. Suzuki

* Physical properties: D. Dwyer, S. Hemming, K. Hochmuth, D. McNamara, M. Sinnesael, N. White

* Stratigraphic correlation: S. Hemming, M. Sinnesael

* Paleomagnetism: A. Di Chiara, D. Dwyer, S. Friedman, S. Satolli

* Geochemistry and microbiology: Y. Cui, J. Dodd, M. Lindsay, G. Pasquet

* Downhole measurements: K. Hochmuth, D. McNamara

* Age model: A. Di Chiara, T. Dunkley Jones, S. Friedman, B. Karatsolis, P. Pearson, S. Satolli, T. Suzuki

<footnote n="1">¹Parnell-Turner, R.E., Briais, A., LeVay, L.J., Cui, Y., Di Chiara, A., Dodd, J.P., Dunkley Jones, T., Dwyer, D., Eason, D.E., Friedman, S.A., Hemming, S.R., Hochmuth, K., Ibrahim, H., Jasper, C., Karatsolis, B.T., Lee, S., LeBlanc, D.E., Lindsay, M.R., McNamara, D.D., Modestou, S.E., Murton, B., OConnell, S., Pasquet, G.T., Pearson, P.N., Qian, S.P., Rosenthal, Y., Satolli, S., Sinnesael, M., Suzuki, T., Thulasi Doss, T., White, N.J., Wu, T., and Yang Yang, A., 2025. Expedition 395 methods. In Parnell-Turner, R.E., Briais, A., LeVay, L.J., and the Expedition 395 Scientists, Reykjanes Mantle Convection and Climate. Proceedings of the International Ocean Discovery Program, 395: College Station, TX (International Ocean Discovery Program). https://doi.org/10.14379/iodp.proc.395.102.2025</footnote>

<footnote n="2">²Expedition 395 Scientists’ affiliations.</footnote>
This introductory section provides an overview of drilling and coring operations, core handling, curatorial conventions, depth scale terminology, and the sequence of shipboard analyses. Subsequent sections of this chapter document specific laboratory instruments and methods in detail.

**1.1. Operations**

The IODP Environmental Protection and Safety Panel (EPSP) approved the six primary and seven alternate drilling sites for Expedition 395 described in the Scientific Prospectus (Parnell-Turner et al., 2020) and Scientific Prospectus Addendum (Parnell-Turner et al., 2023). The shipboard global navigation satellite system (GNSS) (WGS84 datum) was used to position the vessel at the Expedition 395 sites. Once the vessel was positioned at a site, the thrusters were lowered, and a seafloor positioning beacon was prepared for deployment in case it was needed. Dynamic positioning control of the vessel was constrained by the navigational input from the GNSS system (Figure F1). No seafloor positioning beacons were deployed during this expedition. The final hole position was calculated as the mean position of at least 1000 GNSS position fixes while the hole was occupied. The ship's position is resolved with an accuracy of less than 1 m, but the exact position of the hole is less well known because of the deviation of the pipe below the ship, which can vary depending on water currents, tides, and water depth; the hole position is thus known typically within 10 m accuracy. The precision depth recorder (PDR) was used to estimate the depth of the seafloor.

Drilling sites were numbered according to the series that began with the first site drilled by the drilling vessel (D/V) *Glomar Challenger* in 1968. Starting with Integrated Ocean Drilling Program Expedition 301, the prefix “U” designates sites occupied by *JOIDES Resolution*. When drilling multiple holes at a site, hole locations were offset from each other by ~10–20 m. A letter suffix distinguishes each hole drilled at the same site. The first hole drilled is assigned the site number modified by the suffix “A,” the second hole takes the site number and the suffix “B,” and so forth. During Expedition 395, six sites were occupied (U1554, U1555, U1562, U1563, U1564, and U1602) and 27 holes were drilled (see Table T1 in the Expedition 395 summary chapter [Parnell-Turner et al., 2025]).

<figure><img src="image_5.png" /><figcaption>**Figure F1.** IODP convention for naming sites, holes, cores, sections, and samples. Ship positioning while coring was accomplished with the global navigation satellite system. Cores from Hole 395-U1562C are used as an example; actual recovery percentages differ.</figcaption></figure>
**1.2. JOIDES Resolution standard coring systems**

The advanced piston corer (APC), half-length APC (HLAPC), extended core barrel (XCB), and rotary core barrel (RCB) systems were used during Expedition 395. These tools and other drilling technology are documented in Graber et al. (2002).

The APC and HLAPC systems cut soft-sediment cores with minimal coring disturbance relative to other IODP coring systems. After the APC/HLAPC core barrel is lowered through the drill pipe and lands above the bit, the inside of the drill pipe is pressured up until one or two shear pins that hold the inner barrel attached to the outer barrel fail. The inner barrel then advances into the formation at high speed and cuts a core with a diameter of 6.6 cm (2.6 inches) (Figure F2). The driller can detect a successful cut, or full stroke, from the pressure gauge on the rig floor because the excess pressure accumulated prior to the stroke drops rapidly. The depth limit of the APC system, often referred to as APC refusal, is indicated in two ways: (1) the piston fails to achieve a complete stroke (as determined from the pump pressure and recovery reading) because the formation is too hard or (2) excessive force (>60,000 lb) is required to pull the core barrel out of the formation. When a full stroke could not be achieved, one or more additional attempts were typically made, and each time the bit was advanced by the length of the core recovered (note that for these cores, this results in a nominal recovery of ~100%). When a full or partial stroke is achieved but excessive force is insufficient to retrieve the core barrel, it can be drilled over, meaning that after the inner core barrel was successfully shot into the formation the drill bit is advanced to total depth to free the APC barrel.

The standard APC system uses a 9.6 m long core barrel, whereas the HLAPC system uses a 4.7 m long core barrel. The HLAPC typically is deployed after the standard APC has repeated partial strokes. Occasionally, the HLAPC is interchanged with the APC to offset coring gaps for strati-

<figure><img src="image_6.png" /></figure>

**Figure F2.** APC system used during Expedition 395 (see Graber et al., 2002). The HLAPC uses the same equipment, but the core barrel is 4.7 m in length. ID = inner diameter.
graphic correlation. While using the HLAPC, the same criteria is applied in terms of refusal as for
the APC system.

The XCB system is typically used when the APC/HLAPC system has difficulty penetrating the formation and/or damages the core liner or core. The XCB system can also be either used to initiate holes where the seafloor is not suitable for APC coring or interchanged with the APC/HLAPC when dictated by changing formation conditions. For example, the XCB system was deployed during Expedition 395 to better recover the sediment/basement interface. The XCB system has a small cutting shoe that extends below the large APC/XCB bit (Figure F3). The smaller bit can cut a semi-indurated core with less torque and fluid circulation than the main bit, optimizing recovery. The XCB cutting shoe extends ~30.5 cm ahead of the main bit in soft sediment but retracts into the main bit when hard formations are encountered. It cuts cores with a nominal diameter of 5.87 cm (2.31 inches), slightly less than the 6.6 cm diameter of APC cores. XCB cores are often broken (i.e., torqued) into biscuits, which are disc-shaped pieces a few to several centimeters long with remolded sediment (including some drilling slurry) interlayering the discs and packing the space between the discs and the core liner. This type of drilling disturbance may give the impression that the XCB cores have the same diameter (6.6 cm) as the APC cores.

The bottom-hole assembly (BHA) used for APC and XCB coring during Expeditions 384 and 395C was composed of an 11⅞ inch (~29.05 cm) bit, a bit sub, a seal bore drill collar, a landing saver sub, a modified top sub, a modified head sub, a variable number of 8¼ inch control length drill collars, a tapered drill collar, two stands of 5½ inch transition drill pipe, and a crossover sub to the drill pipe that extended to the surface. The same BHA was used during Expedition 395 except for the drill bit, which was a 9⅝ inch polycrystalline diamond compact bit.

The RCB system is designed to recover firm to hard sediments and basement rocks. The BHA, including the bit and outer core barrel, is rotated with the drill string while bearings allow the inner core barrel to remain stationary (Figure F4).

<figure><img src="image_7.png" /><figcaption>**Figure F3.** XCB system used during Expedition 395 (see Graber et al., 2002).</figcaption></figure>
A typical RCB BHA includes a 9⅞ inch drill bit, a mechanical bit release, a bit sub, an outer core barrel, a modified top sub, a modified head sub, a variable number of 8¼ inch control length drill collars, a tapered drill collar, two stands of 5½ inch drill pipe, and a crossover sub to the drill pipe that extends to the surface.

Nonmagnetic core barrels were used for all APC, HLAPC, and RCB coring. APC cores were oriented with the Icefield MI-5 core orientation tool when coring conditions allowed (see Operations in each site chapter for more information). During Expedition 384, the FlexIT core orientation tool was also used (Blum et al., 2020). Formation temperature measurements were taken with the third-generation advanced piston corer temperature (APCT-3) tool (see **Downhole measurements**). Information on recovered cores, drilled intervals, downhole tool deployments, and related information are provided in Operations, Paleomagnetism, and Downhole measurements in each site chapter.

**1.3. Drilling disturbance**

Cores may be significantly disturbed by the drilling process and contain extraneous material because of the coring and core handling process. In formations with loose granular layers (e.g., sand, ash, foraminifer ooze, and clasts), granular material from intervals higher in the hole may settle and accumulate in the bottom of the hole because of drilling circulation and be sampled with the next core. The uppermost 10–50 cm of each core must therefore be examined critically for potential fall-in. Several cores recovered during Expedition 395 have large clasts at the top of the first section, which likely fell in from above.

Common coring-induced deformation includes the concave-downward appearance of originally horizontal bedding. Piston action may result in fluidization (flow-in) at the bottom of, or sometimes within, APC cores. Retrieval of unconsolidated cores from depth to the surface typically results to some degree in elastic rebound, and gas that is in solution at depth may become free and drive core segments in the liner apart. When gas content is high, pressure must be relieved for

<figure><img src="image_8.png" /><figcaption>**Figure F4.** RCB system used during Expedition 395 (see Graber et al., 2002). OD = outer diameter, ID = inner diameter.</figcaption></figure>
safety reasons before the cores are cut into segments. Holes are drilled into the liner, which forces some sediment and gas out of the liner. As noted above, XCB coring typically results in biscuits mixed with drilling slurry. Drilling disturbances are described in Lithostratigraphy in each site chapter and are indicated on the graphic core summary reports, also referred to as visual core descriptions (VCDs).

**1.4. Downhole measurements**

**1.4.1. Formation temperature**

Formation temperature measurements were taken with the APCT-3 tool (see **Downhole measurements**) embedded in the APC cutting shoe at specified intervals. These measurements were used to obtain temperature gradients and heat flow estimates. Information on downhole tool deployments is provided in Operations and Downhole measurements in each site chapter.

**1.4.2. Wireline logging**

During wireline logging operations, the logs were recorded with Schlumberger and IODP logging tools combined into tool strings, which were lowered into the hole after the completion of coring operations. Four tool strings were run across the three expeditions: the triple combination (triple combo), Formation MicroScanner (FMS)-sonic, Ultrasonic Borehole Imager (UBI), and Versatile Seismic Imager (VSI). A full description of the logging tools used can be found in Downhole measurements in each site chapter.

In preparation for logging, the boreholes were flushed of debris by circulating drilling fluid and were at least partially filled with seawater-based logging gel (sepiolite mud mixed with seawater). Only one hole, U1555I, was displaced with heavy mud (weighted with barite; density = ~1258 kg/m³) to help stabilize the borehole walls in sections where instability was expected from drilling and coring disturbance. The BHA was pulled up to a suitable depth below seafloor, where it protected the unstable upper part of the hole. For holes in which the RCB system was used, the bit was either dropped on the seafloor or at the bottom of the hole prior to setting the BHA at depth. The tool string was then lowered downhole on a seven-conductor wireline cable before being pulled up at a constant speed of 550 m/h (or 250 m/h for the UBI) to provide continuous log measurements of several properties simultaneously. Further details on the logging operations are described in Downhole measurements in each site chapter.

**1.5. Core and section handling**

**1.5.1. Whole-round cores**

When the core barrel reached the rig floor, the core catcher from the bottom of the core was removed and taken to the core receiving platform (catwalk). When coring sediment, a sample was extracted for paleontological (PAL) analysis from the core catcher (Figure F5). Next, the sediment core was extracted from the core barrel in its plastic liner. The liner was carried from the rig floor to the core processing area on the catwalk outside the core laboratory, where it was split into ~1.5 m sections. The exact section length was noted and entered into the database as created length using the Sample Master application. This number was used to calculate core recovery.

Once the core was cut into sections, whole-round sediment samples were immediately taken for interstitial water (IW) extraction and chemical analyses from the bottom of selected core sections. Headspace samples were taken from the top of a selected section (typically one per core) using a syringe for immediate gas analyses according to the IODP hydrocarbon safety monitoring protocol. Samples for microbiological analysis of sediment and basalt were also collected at this stage. The resulting sediment residues (squeeze cakes) from the IW analyses were used for bulk geochemistry measurements.

When catwalk sampling was complete for sediment cores, liner caps (blue = top, colorless = bottom, and yellow = top of section where a whole-round sample was removed) were glued with acetone onto liner sections, and the sections were labeled and laser engraved with their section identification numbers. The whole rounds were then placed in core racks for analysis. Oxygen probe measurements were taken from selected core sections (see **Geochemistry and microbiol-**
ogy). For the basalt intervals, the cores were brought directly from the catwalk to the core splitting room without adhering endcaps. The basalt cores were shaken out of the core liner into alcohol-cleaned split liner sections. Whole-round samples (~5 cm length) were selected for microbiological studies and photographed. The basalt pieces were marked for orientation, rinsed with freshwater, and placed in split liners. Core cut lines, or split lines, were drawn on the hard rock pieces and then aligned as working and archive halves.

The curated length of the sediment cores was set equal to the created length and was updated very rarely (e.g., in cases of data entry errors or when section length expanded by more than ~2 cm). The curated length of the hard rock is measured after the rock pieces are placed in individual bins in the core liner. Depth in hole calculations are based on the curated section length (see **Depth calculations**).

The workflow for the whole-round sediment and hard rock cores differs. Most sediment cores were immediately run through the Special Task Multisensor Logger (STMSL) to collect 5 cm resolution magnetic susceptibility (MS) and gamma ray attenuation (GRA) bulk density data for stratigraphic correlation. The whole-round sections were run through the Natural Gamma Radiation Logger (NGRL) and X-ray imaged using the X-Ray Linescan Logger (XSCAN) prior to thermal equilibration. When the core sections reached equilibrium with laboratory temperature (typically after 4 h), they were run through the Whole-Round Multisensor Logger (WRMSL) for MS, GRA bulk density, and P-wave velocity ($V_p$). Thermal conductivity measurements were taken once per core when the material was suitable. See **Physical properties** for more information.

Following the binning of hard rock sections, the cores were imaged using the Section Half Imaging Logger (SHIL) in 360° mode. The split core liners were then held together with electrical tape while the whole rounds were run through the NGRL and, following thermal equilibration, the WRMSL for MS and GRA bulk density.

## 1.5.2. Core section halves

After completion of whole-round analyses, the sections were split lengthwise into working and archive halves (Figure F5). Soft-sediment cores were split with a wire; investigators should note that older material can be transported upward on the split face of a section during splitting using this method. Harder sediment and hard rock were cut using a saw. Following cutting, the pieces of hard rock were dried and individual labels were adhered to each piece.

Discrete samples were then taken from the working half of each core for moisture and density (MAD), paleomagnetic (PMAG), carbonate (CARB), smear slide, and thin section analysis for the

<figure><img src="image_9.png" /></figure>

**Figure F5.** Overall flow of cores, sections, analyses, and sampling implemented during Expedition 395. All the measurements listed were implemented at some stage during the three expeditions. Refer to individual site chapters for more information. TCON = thermal conductivity, IC = ion chromatography.
sedimentary section. Samples for PMAG, thin sections, and inductively coupled plasma–atomic emission spectroscopy (ICP-AES) analyses were selected from the hard rock. PMAG samples from the hard rock were used for MAD analysis. Selected working half core sections were X-ray imaged and measured for thermal conductivity. $V_p$ was measured using the caliper and/or bayonets on the physical properties gantry.

During the expeditions, samples for personal postcruise research were taken only where they concerned ephemeral properties (e.g., IW and microbiology). Personal sampling of the sedimentary sections was deferred to a postcruise sampling party. During Expedition 395, personal sampling for hard rock was permitted to avoid having to cut samples at the postcruise sampling party.

The archive half of each core was scanned on the SHIL to provide linescan images and then measured for point MS (MSP) and reflectance spectroscopy and colorimetry on the Section Half Multisensor Logger (SHMSL). Hard rock cores were imaged with both wet and dry surfaces. Labeled foam pieces were used to denote missing whole-round intervals in the SHIL images. The archive halves were then described visually and by means of smear slide for sedimentology and thin section for petrology. Hard rock cores were point scanned using the portable X-ray fluorescence spectrometer (pXRF). Finally, the magnetization of archive half sections and working half discrete pieces was measured with the superconducting rock magnetometer (SRM) and spinner magnetometer.

When all steps were completed, cores were wrapped, sealed in plastic D-tubes, boxed, and transferred to cold storage space aboard the ship. At the end of Expedition 395, all the working half core sections were shipped to the IODP Bremen Core Repository (BCR) (Germany). The archive halves were sent to the IODP Gulf Coast Repository (GCR) in College Station (USA) for X-ray fluorescence (XRF) scanning, with the exception of archive halves collected at Site U1602, which were shipped to Scripps Institution of Oceanography (USA) for XRF scanning. All core sections from Expeditions 384 and 395C were shipped to the GCR for visual description and XRF scanning and partial U-channel sampling.

## 1.6. Sample identifiers

Sample naming in this volume follows standard IODP procedure. A full sample identifier consists of the following information: expedition, site, hole, core number, core type, section number, section half, and offset in centimeters measured from the top of the core section (Figure F1). For example, a sample identification of "395C-U1554E-5H-3W, 10–12 cm," represents a sample taken from the interval between 10 and 12 cm below the top of the working half ("W") of Section 3 of Core 5 ("H" designates that this core was taken with the APC system) of Hole U1554E during Expedition 395C. The archive half is designated by an "A" following the section number.

The drilling system used to obtain a core is designated in the sample identifiers as follows: H = APC, F = HLAPC, X = XCB, and R = RCB. Integers are used to denote the core type of drilled intervals (e.g., a drilled interval between Cores 2H and 4H would be denoted by Core 31, where 1 is the core type).

When working with data downloaded from the LIMS database or physical samples that were labeled on the ship, three additional sample naming concepts may be encountered: text ID, label ID, and printed labels.

### 1.6.1. Text ID

Samples taken on *JOIDES Resolution* are uniquely identified for use by software applications using a text ID, which combines two elements:

* Sample type designation (e.g., TSB for thin section billet) and

* A unique sequential number for any sample and sample type added to the sample type code (e.g., TSB22072522).

The text ID is not particularly helpful to most users but is critical for machine reading and troubleshooting.
**1.6.2. Label ID**

The label ID is used throughout the *JOIDES Resolution* workflows as a convenient, human-readable sample identity. However, a label ID is not necessarily unique. The label ID is made up of two parts: primary sample identifier and sample name.

The primary sample identifier is very similar to the full sample identifier described above, with
two notable exceptions:

* Section halves always carry the appropriate identifier (395-U1602B-22F-1-A and 395-U1602B-22F-1-W for archive and working halves, respectively).

* Sample top and bottom offsets, relative to the parent section, are indicated as “35/37” rather than “35–37 cm.”

**1.7. Depth calculations**

Sample and measurement depth calculations were based on the methods described in IODP
Depth Scales Terminology v2.2 (https://www.iodp.org/policies-and-guidelines/142-iodp-
depth-scales-terminology-april-2011/file). The definition of multiple depth scale types and
their distinction in nomenclature should keep the user aware that a nominal depth value at two
different depth scale types (and even two different depth scales of the same type) generally does
not refer to the exact same stratigraphic interval in a hole. The SI unit for all depth scales is meters.

Depths of cored intervals were measured from the drill floor based on the length of drill pipe deployed beneath the rig floor and referred to as drilling depth below rig floor (DRF); it is traditionally referred to with custom units of meters below rig floor (mbrf). The depth of each cored interval, measured on the DRF scale, can be referenced to the seafloor by subtracting the seafloor depth measurement (on the DRF scale) from the cored interval (on the DRF scale). This seafloor referenced depth of the cored interval is reported on the drilling depth below seafloor (DSF) scale. In the case of APC coring, the seafloor depth was calculated as the length of pipe deployed minus the length of the mudline core recovered.

Depths of samples and measurements in each core were computed based on a set of rules that result in the core depth below seafloor, Method A (CSF-A), depth scale. The two fundamental rules for this scale are that (1) the top depth of a recovered core corresponds to the top depth of its cored interval (top DSF depth = top CSF-A depth) regardless of type of material recovered or drilling disturbance observed and (2) the recovered material is a contiguous stratigraphic representation even when core segments are separated by voids when recovered, the core is shorter than the cored interval, or it is unknown how much material is missing between core pieces. When voids were present in the core on the catwalk, they were closed by pushing core segments together whenever possible. The length of missing core should be considered a depth uncertainty when analyzing data associated with core material.

When core sections were given their curated lengths, they were also given a top and a bottom
depth based on the core top depth and the section length. Depths of samples and measurements
on the CSF-A scale were calculated by adding the offset of the sample (or measurement from the
top of its section) to the top depth of the section.

Per IODP policy established after the introduction of the IODP Depth Scales Terminology v2, sample and measurement depths on the CSF-A depth scale may be referred to with the custom unit meters below seafloor (mbsf). In this volume, mbsf is not used. The reader should be aware that different depth scales may be assigned to the same stratigraphic interval. For example, a soft-sediment core from less than a few hundred meters below seafloor often expands upon recovery (typically by a few percent to as much as 15%), and the length of the recovered core exceeds that of the cored interval. Therefore, a stratigraphic interval in a particular hole may not have the same depth on the DSF and CSF-A scales. When recovery in a core exceeds 100%, the CSF-A depth of a sample taken from the bottom of the core will be deeper than that of a sample from the top of the subsequent core (i.e., some data associated with the two cores overlap on the CSF-A scale). To overcome the overlap problem, core intervals can be placed on the core depth below seafloor,
Method B (CSF-B), depth scale. The CSF-B approach scales the recovered core length back into the interval cored, from >100% to exactly 100% recovery. If cores had <100% recovery to begin with, they are not scaled. When downloading data using the *JOIDES Resolution* Science Operator (JRSO) LIMS Reports (http://web.iodp.tamu.edu/LORE), depths for samples and measurements are by default presented on both the CSF-A and CSF-B scales. The CSF-B depth scale can be useful for data analysis and presentations at sites with a single hole.

Wireline logging data are collected at the wireline log depth below rig floor (WRF) scale, from which a seafloor measurement is subtracted to create the wireline log depth below seafloor (WSF) scale. Immediately after data collection was completed, the wireline logging data were transferred to the Lamont-Doherty Earth Observatory Borehole Research Group (LDEO-BRG), where multiple passes and runs were depth matched using the gamma radiation logs. The data were returned to the ship at the wireline log matched depth below seafloor (WMSF) scale, which is the final and official logging depth scale type for investigators.

During Expedition 395, all core depths below seafloor were initially calculated according to the CSF-A depth scale. Unless otherwise noted, all depths presented are core depths below seafloor calculated as CSF-A and reported as "m CSF-A."

Core composite depth below seafloor (CCSF) depth scales are constructed for sites with two or more holes to create as continuous a stratigraphic record as possible through correlation between the various holes. This also helps to mitigate the CSF-A core overlap problem and the coring gap problem. Using shipboard core logger-based physical property data verified with core photos, core depths in adjacent holes at a site are vertically shifted to correlate between cores recovered in adjacent holes. This process produces the CCSF depth scale. The correlation process was achieved with the Correlator program Version 4.0 and resulted in affine tables, indicating the vertical shift of cores on the CCSF scale relative to the CSF-A scale. Once the CCSF scale is constructed, a splice can be defined that best represents the stratigraphy of a site by utilizing and splicing the most representative portions of individual sections and cores from each hole. Because of core expansion, the CCSF depths of stratigraphic intervals are typically 10%-15% deeper than their CSF-A depths. CCSF depth scale construction also reveals that coring gaps on the order of 1.0-1.5 m typically occur between two subsequent cores, despite the apparent >100% recovery. For more details on construction of the CCSF depth scale, see Stratigraphic correlation.

## 2. Lithology

This section outlines the procedures for documenting the sedimentology of cores recovered during Expeditions 384, 395C, and 395, including core description, smear slide description, and color spectrophotometry. All observations and data were uploaded directly to the IODP LIMS database using the GEODESC application. The LIMS Information Viewer (LIVE) is a graphic display for core data (e.g., digital images of section halves, principal lithology, and drilling disturbance) that was used for quality control of the uploaded data sets.

### 2.1. Core preparation and digital color imaging

Prior to core description and high-resolution digital color imaging, the quality of the split core surface of the archive half of each core was assessed and the surface was scraped lightly with a metallic or glass plate as needed. Cleaned core sections were then described in conjunction with images obtained by the SHIL, results of smear slide observations, and measurements obtained from the SHMSL (see Physical properties).

Cleaned archive halves were imaged with the SHIL as soon as possible to avoid sediment color changes caused by oxidation and drying. In cases of watery or soupy sediment, the surface was dried, either with the assistance of fans or by blotting with a paper towel, to avoid light reflection during scanning. Two images, a high-resolution JPEG image with grayscale and depth ruler and a low-resolution cropped JPEG image showing only the core section surface, were created from the high-resolution TIFF files. These images were uploaded to the LIMS database under Images >
Core sections, and the red-green-blue (RGB) colorimetry data was uploaded to the LIMS database under Physical properties > RGB channels.

**2.2. Smear slide summary**

Smear slide examination was used to determine the biogenic and terrigenous constituents and their relative abundances to aid in lithologic classification. Toothpick samples were taken from each lithology at a frequency of at least two per core. Slides were prepared by mixing the sediment with a drop of deionized water on a glass slide and drying on a hot plate at 80°C. A sufficient amount of Norland optical adhesive Number 61 was dropped onto the dried slide, and a cover slip was placed over the sediment. The coverslip was fixed to the slide in an ultraviolet light box. Smear slides were examined with a transmitted-light petrographic microscope equipped with a standard eyepiece micrometer. Biogenic and mineral components were identified following standard petrographic techniques as described in Rothwell (1989), Marsaglia et al. (2013), and Marsaglia et al. (2015). Several fields of view (FOVs) were examined with a 10× eyepiece and some combination of 5×, 10×, 20×, and 40× objectives in a transversal section to assess the abundance of detrital, biogenic, and authigenic components. The relative abundance percentages of the sedimentary constituents were visually estimated using the techniques of Rothwell (1989). Type and relative abundance of biogenic and terrigenous components were estimated for each smear slide. Data were entered in the LIMS database using a custom template in GEODESC. Biogenic components observed in smear slides were categorized as follows:

* T = trace (<1%).

* R = rare (1% to <5%).

* C = common (5% to <20%).

* A = abundant (20% to <50%).

* D = dominant (≥50%).

**2.3. Lithologic description and classification of sediments and sedimentary rocks**

The principal lithologic name was assigned on the basis of the relative abundances of biogenic and terrigenous clastic grains. The name assigned to a sediment/rock with <50% biogenic grains was based on the grain size characteristics of the terrigenous clastic fraction (Figure F6). Sediment/rocks with >50% biogenic material were named based on the type and abundance of biogenic material and degree of lithification/diagenesis. Sediments were also characterized by degree of lithification as follows: (1) soft biogenic sediments that deformed under finger pressure were classified as oozes, (2) diagenetic/lithified carbonate sediments (which no longer deform under finger pressure) were described as chalk, and (3) solid/lithified carbonate sediments were described as limestone. The suffix “-stone” was also added to predominantly terrigenous beds which had become lithified. Sediments were classified using the Wentworth (1922) scale to define grain size classes as follows:

* The principal name of a sediment with <50% biogenic grains was based on the predominant grain size of both the terrigenous and biogenic grains. Grain size was largely determined by analysis of smear slides.

<figure><img src="image_10.png" /><figcaption>**Figure F6.** Lithologic classification based on percentage terrigenous and percentage biogenic in the sediment core, Expedition 395.</figcaption></figure>
* The principal name of a sediment with ≥50% biogenic grains was classified as an ooze, modified by the most abundant specific biogenic grain type that formed 50% or more of the sediment. For example, if nannofossils exceeded 50%, then the sediment was classified as a nannofossil ooze. Biogenic constituents of similar composition were grouped together to exceed this 50% abundance threshold. For example, if nannofossils were 40% of the sediment and foraminifers were 20%, then the sediment was termed carbonate ooze or, in the case where the two components were clearly distinguishable and of relatively equal proportions, foraminifer-nannofossil ooze.

Major and minor modifiers were applied to any of the principal granular sediment names as follows:

* Minor modifiers were those components with abundances between 10% and <30% and were used in the lithology suffix preceded by “with.” When more than one minor modifier was present, the component with the higher abundance was followed by the component with less abundance and so forth. When several biogenic components were present and in total exceeded 10%, the term “biogenics” was used. For example, a sediment with 35% silt, 45% clay, 6% nannofossils, 6% foraminifers, 6% diatoms, and 2% sponge spicules was classified as “silty clay with biogenics.”

* Major modifiers were those components with abundances between 30% and 50% and were used in the lithology prefix. For example, a sediment with 35% nannofossils, 30% silt, and 35% clay would be classified as a nannofossil silty clay.

Component abundances and the resulting principal lithologic name were noted in the microscopic and macroscopic sediment templates in GEODESC DataCapture (Figure F7). For cores collected during Expeditions 384 and 395C and described at the GCR, sediments within the range of silty clay to clayey silt were described using the combined term “silty clay or clayey silt” for the following holes:

* Holes U1554A–U1554F,

* Holes U1555H and U1555I,

* Holes U1562A and U1562B,

* Hole U1563A, and

* Holes U1564A–U1564C.

Where a given site was revisited during Expedition 395 and the same sedimentary sequences were recovered, intervals of sediment originally classified as “silty clay or clayey silt” were reexamined.

<figure><img src="image_11.png" /><figcaption>**Figure F7.** Ternary diagram used to determine the name of the lithology of terrigenous sediment, Expedition 395.</figcaption></figure>
This additional analysis allowed for refinement of the “silty clay or clayey silt” lithology to either “silty clay” or “clayey silt” at most sites. In most instances, refinement to “silty clay” was prevalent. This refinement has been applied where possible to the lithologic summaries documented in this volume.

**2.4. Sedimentary structures**

The presence of sedimentary structures was noted in the macroscopic sediment template in GEO-DESC Data Capture as follows:

* Fault: a discrete surface or zone of discrete surfaces separating two sedimentary units across which one mass has slid past the other. An offset is clearly observed based on textures and/or colors.

* Fracture: any separation in the sediment core, inclusive of faults and joints, when there was no clear offset on either side of the feature.

* Soft-sediment deformation: sediment which appears waved or otherwise deformed by post-depositional physical movement.

* Graded bed: a layer that displays a gradual and progressive change, either in color or in particle size. If the bed was only graded by color, it was noted in the sedimentary structure comments.

* Contacts: contacts between lithologies were described and assigned to the base of the interval in which they appeared. Contacts include, but are not limited to, color transitions and other boundaries disturbed by bioturbation, as well as obvious lithologic boundaries.

**2.5. Clast abundance**

Clasts that were visible on the surface of the cores were documented. Clasts between 0.5 and 2 cm were counted, and their depth within the section was recorded. If a clast was more than 2 cm long on its major axis, it was removed from the section half, cleaned, examined and put back before the section was imaged on the SHIL. If removal of the clast would cause obvious disturbance to the core material, the clast was removed after imaging. The size, composition, and depth in core were also recorded for clasts >2 cm.

**2.6. Spectrophotometry and colorimetry**

The SHMSL employs multiple sensors for the measurement of bulk physical properties in a motorized and computer-controlled section-half logging machine. The sensors included in the SHMSL are reflectance spectroscopy and colorimetry, MS, and a laser surface analyzer. Spectrophotometry and MS were measured at 2 or 2.5 cm resolution. Reflectance spectroscopy (spectrophotometry) was carried out using an Ocean Insight QE-Pro spectrophotometer. This instrument measures the reflectance spectra of the split core from the ultraviolet to near-infrared range. Colorimetric information is extracted from the reflectance data to the L*a*b* color space system. The L*a*b* color space expresses color as a function of lightness (L*) and color values, where a* reflects the balance between red (positive a*) and green (negative a*) and b* reflects the balance between yellow (positive b*) and blue (negative b*). When a* and b* are 0, there is no color and L* determines grayscale. MS was measured on the SHMSL with a Bartington MS2 meter and MS2K contact probe. Additional instrument details and instrument resolution for each hole are given in **Physical properties**.

Accurate spectrophotometry using the SHMSL demands a direct and level contact between the instrument sensors and the split core surface. A built-in laser surface analyzer aids the recognition of irregularities in the split core surface (e.g., cracks and voids), and data from this tool were recorded to provide an independent check on the fidelity of SHMSL measurements.

**2.7. Visual core description and standard graphic report**

Information from macroscopic standard sedimentologic observations for each core was recorded directly into GEODESC DataCapture. Two templates were constructed (drilling disturbance and macroscopic sediment), and data entry columns were customized to include relevant descriptive information categories. For the macroscopic sediment template, these categories include lithology,
sedimentary structures, bioturbation intensity, Munsell color, macrofossils, and clast counts. A
summary description was created for each core.

A simplified one-page graphical representation of each core, referred to as a VCD (Figure F8), was generated using the LIMS2Excel application and the commercial program Strater (Golden Software). VCDs are presented with the CSF-A depth scale; age; shipboard samples; split core photographs; graphic lithology; and columns for core disturbance, bioturbation, sedimentary structures, color reflectance (L*a*b*), clast count (including only clasts with a long axis greater than 2 cm), MS, GRA bulk density, and natural gamma radiation (NGR) counts. The graphic lithologies, sedimentary structures, and other visual observations are represented on the VCDs by graphic patterns and symbols (Figure F9). Each VCD also contains the summary description for the core. Only major lithologies are shown on the summary figure for each chapter.

**2.8. Shipboard samples**

Samples for shipboard analyses were taken from the working half of cores, from the residues of whole-round IW squeeze cakes, or from the whole-round core catcher section. These samples are indicated in the shipboard samples column on the VCDs as follows:

<figure><img src="image_12.png" /><figcaption>**Figure F8.** Example VCD, Expedition 395.</figcaption></figure>
* CARB = sample to measure weight percent calcium carbonate.

* HS = headspace sample, to measure formation gas concentrations (see **Geochemistry and microbiology**).

* IW = interstitial water sample, whole round removed from the core; residues from this sample were often used for other analyses such as XRD (see below).

* MAD = moisture and density sample.

* SED = smear slide sample.

* PAL = portion of core catcher for biostratigraphy.

* PMAG = paleomagnetic cube taken for postcruise research.

* NANNO = smear slide taken to identify nannofossils (in addition to PAL samples).

* FORAM = sample taken to identify foraminifers (in addition to PAL samples).

* XRD = sample taken for shipboard XRD analysis, usually a split of the IW residue (see **Geochemistry and microbiology**).

* NOTESTS = whole-round sample, not generally used for analyses as taken, but split into samples for other analyses previously listed in instances when IW samples were not collected.

## 2.9. Bioturbation

Bioturbation was noted in the macroscopic sediment template in GEODESC DataCapture. Four levels of bioturbation where identified:

* Absent: no visible bioturbation. This could mean no bioturbation or complete homogenization of the sediment from bioturbators.

* Sparse: 1%–10% of split core surface area contains visible bioturbation.

* Moderate: >10%–50% of split core surface area contains visible bioturbation.

* Abundant: >50% of split core surface area contains visible bioturbation.

## 2.10. Drilling disturbance

Deformation and disturbances of sediment that clearly resulted from the coring process were described in a separate template in GEODESC DataCapture. Deformation and disturbances of

<figure><img src="image_13.png" /><figcaption>**Figure F9.** VCD legend, Expedition 395.</figcaption></figure>
sediment are illustrated in the Disturbance type column of the VCDs, and the intensity of the drilling disturbance is plotted in the Drilling disturbance intensity column (Figure F9). Drilling disturbance intensity was classified into four categories:

* Absent (<1%),

* Slightly disturbed (1%–10%),

* Moderately disturbed (>10%–50%), and

* Highly disturbed (>50%–100%).

The definitions of drilling disturbance terms are consistent with nomenclature of Jutzeler et al. (2014) and the method of Expedition 339 Scientists (2013) unless otherwise noted and are as follows:

* Biscuiting: breakage of semilithified core into disc-shaped pieces, often separated by remolded mud (also known as gravy) that is a mixture of pulverized sediment and drilling fluid.

* Brecciated: firm sediments that are pervasively broken and may be displaced or rotated.

* Deformed: soft-sediment bedding contacts that are disturbed and bent.

* Fall-in: debris in the top of a core that fell into the borehole from shallower depths during the coring process.

* Fragmented: indurated sediment displaying breakage.

* Uparching: soft-sediment layers in the plastic core liner bending down around the cut periphery due to friction between the sediments and core liner; this is generally observed in piston cores.

* Soupy: intervals that are water saturated and have lost all aspects of original bedding.

* Void: an interval that has no core material. A polystyrene foam spacer may be added to the core after splitting to preserve the integrity of the remaining material.

## 2.11. Expeditions 384 and 395C

Because of the COVID-19 pandemic, only IODP technical staff sailed on Expeditions 384 and 395C. A simplified workflow was adapted for shipboard measurements including all physical properties measurements and imaging with the track systems. A subset of the Expedition 395 science party traveled to the GCR for core description after these two expeditions in 2022. As a result of the time lapse between core collection and description, significant sediment oxidation may have occurred. Consequently, color descriptions may not be consistent between Expedition 395 and Expeditions 384 and 395C. Moreover, additional scraping of core surfaces was required for cores from Expeditions 395C and 384 prior to description.

## 3. Igneous petrology

We adapted rock core description procedures from Expeditions 367/368 (Sun et al., 2018) and 385 (Teske et al., 2021) with the primary goal of systematically describing the physical appearance, petrology, mineralogy, and alteration of recovered igneous rock material. Phenocryst abundance and appearance, vesicularity, extent of alteration, igneous textures, and morphological characteristics were first described at a macroscopic level and then investigated in more detail using thin sections.

Because of COVID-19 protocols during Expeditions 384 and 395C, cores from these expeditions were described at the GCR during May 2022. One benefit of this approach is that it allowed most of the petrology team to visually examine the cores together and reach a general consensus regarding methods and observations. To the extent possible, we used the same procedures and terminology for shipboard core description during Expedition 395 (Site U1564). The resulting core description data were entered into the customized GEODESC software application.

### 3.1. Core description

For all igneous rock cores, we conducted a visual core description, thin section sampling and description, digital color imaging, and color reflectance spectrophotometry. During Expeditions
395 and 395C, we also measured $V_p$ and conducted shipboard pXRF and ICP-AES analysis (see **Geochemistry and microbiology**). Prior to splitting the cores into working and archive halves, each whole-round section was subjected to nondestructive physical properties analysis (see **Physical properties**). During Expedition 384, additional whole-round samples were taken from Holes U1555F and U1555G for engineering tests (Blum et al., 2020) and whole-round imaging was not conducted. During Expeditions 395C and 395, each whole-round section was imaged using the SHIL (see **Physical properties**) on a wet surface at four different angles (0°, 90°, 180°, and 270°). These images were then combined to create a 360° whole-round image for each core section. Whole-round core samples selected for microbiological analysis and partial sampling were photographed using a high-resolution digital single-lens reflex camera. This step was necessary because the whole-round microbiological sample—generally ~5 cm in length, depending on the abundance of veins and amygdules—was taken before the core sections were imaged (see **Geochemistry and microbiology**). Following subsampling of the microbiological whole-round core pieces, the leftover material was returned and the presampling photograph was used to help reconstruct the section interval. After microbiological sampling, splitting lines were drawn using a wax crayon by a shipboard technician (Expeditions 384 and 395C) and/or a petrologist (Expedition 395) to preserve compositional and structural features in archive and working halves. The cores were then split using a diamond-impregnated saw along the splitting lines. Afterward, fragments of igneous rock that fit together were assigned a joint number and labeled with a letter in consecutive order downsection (e.g., 1A, 1B, and 1C). Plastic spacers were mounted in the split liners to separate pieces with different numbers. For single pieces that showed no evidence of rotation, an arrow pointing to the top of the section was added to the labels to indicate orientation.

We used the archive half for macroscopic investigation and the working half for sampling (either shipboard or at the core repository, as required). Scanning the cut dry and wet archive-half surfaces using the SHIL produced high-resolution color images. Then, color reflectance and MSP were measured at steps of 2 or 2.5 cm on the archive-half surfaces using the SHMSL (see **Physical properties**), and pXRF analyses were conducted (see **Geochemistry and microbiology**). The working halves were sampled for destructive shipboard analyses such as paleomagnetic and MAD measurements, thin section preparation, and geochemical analyses using ICP-AES. Most of the samples chosen for ICP-AES analyses were from the same piece taken for thin section petrography.

We first examined the archive-half sections of each core at the macroscopic level (aided by a 10× magnification field hand lens and a binocular microscope), describing primary (igneous) and secondary (alteration) petrologic characteristics. Afterward, the sampled thin sections were observed and described using a petrographic microscope (up to 40× magnification). For both macroscopic and microscopic observations, we used GEODESC to record igneous characteristics (e.g., groundmass, phenocryst mineralogy, and vesicle size and abundance) and alteration features (e.g., color, vesicle filling, secondary minerals, and vein/fracture fillings; see **Alteration petrology and structural geology**).

**3.2. Macroscopic visual core description**

VCDs present select macroscopic core observations and features. For consistency, we used the same VCD format for all three expeditions. The hard rock VCDs include the following features, from left to right (Figures F10, F11):

* CSF-A depth scale (meters below seafloor);

* Core length scale from 0 to 150 cm;

* Location of shipboard samples, including thin sections (TS), inductively coupled plasma spectroscopy (ICP), cubes for magnetics (PMAG), microbiological samples (MBIO), and engineering samples (ENG);

* Scanned digital image of the archive half;

* Graphic representation of lithology;

* Symbol “G” (next to the graphic lithology), which indicates the presence of volcanic glass in the glassy rind of chilled margins or as fragments (e.g., in volcanic breccia);

* Igneous lithologic unit number;
* Symbols denoting vein type and connectivity, as well as the location of major vesicle bands;

* Graphic representation of average vesicle abundance;

* Stacked line chart displaying percent phenocryst abundance for olivine (OL; green line), plagioclase (PLAG; red line), and clinopyroxene (CPX; blue line), if present;

* Line chart displaying groundmass grain size categorization;

* Line chart displaying alteration intensity;

* Color bar denoting alteration color;

* Plot showing whole-round MS measurements; and

* Description summary of the section and each igneous lithologic unit identified therein.

<figure><img src="image_14.png" /><figcaption>**Figure F10.** Example igneous rock VCD. See Figure F11 for legend.</figcaption></figure>
**3.3. Igneous lithologic units**

Igneous units were classified on the basis of primary modal composition, groundmass texture, and any identifiable flow morphology. We defined igneous lithologic unit boundaries when there were significant changes in rock type (e.g., a transition from basalt to a sediment-rich horizon) or phenocryst assemblage (e.g., olivine phyric to plagioclase phyric). In practice, most sites exhibited minimal variations in mineral assemblage at the hand specimen scale, so the majority of lithologic unit divisions were based on the presence of significant carbonate mudstone or peperite horizons. Closely intercalated intervals were grouped to avoid repetitive entry at the small-scale level with dubious significance (e.g., a pillow lava unit with multiple horizons of intercalated peperite near the top or bottom, grading to sediment-poor basalts).

Because of incomplete recovery and a general lack of well-defined contacts, these unit boundary locations are approximate and preliminary. All igneous units were numbered downhole (i.e., Igneous Lithologic Unit 1, 2, 3, and so on).

**3.3.1. Rock classification and description**

Igneous rocks were classified based on the International Union of Geological Sciences (IUGS) system (Le Maitre et al., 2002). We assigned rock names based on macroscale observations of groundmass texture/color and dominant phenocryst phases, if present. All basement rocks recovered during Expeditions 384, 395C and 395 were classified as basalt because of their dark gray color and micro- to cryptocrystalline groundmass with minor amounts of olivine and plagioclase; this designation was later confirmed through geochemical analysis. Porphyritic rocks were named by phenocryst type and relative abundances as follows:

* Aphyric: phenocrysts constitute <1% of the rock volume.

* Sparsely phyric: phenocryst content ranges 1% to <5%.

* Moderately phyric: phenocryst content ranges 5%–10%.

* Highly phyric: phenocryst content >10%.

When phenocrysts were observed, we documented the mineral, abundance, and shape (e.g., anhedral, subhedral, and euhedral).

**3.3.1.1. Groundmass**

We characterized the groundmass of all igneous rock core sections based on average grain size and extent of crystallization. All rock core intervals were described macroscopically, and a subset was assessed microscopically where thin sections were taken (see **Microscopic description**).

<figure><img src="image_15.png" /><figcaption>**Figure F11.** Igneous rock VCD legend, Expedition 395.</figcaption></figure>
The average grain size was assigned at the macroscale using the following schema, with more
detailed description of groundmass texture provided through thin section observation:

* Cryptocrystalline ($<$0.1 mm),

* Fine grained ($>$0.1–1 mm),

* Medium grained ($>$1–2 mm), and

* Coarse grained ($>$2 mm).

Groundmass crystallinity was characterized using the following categories:

* Holohyaline (vitric; only glass),

* Hypohyaline (comprising both crystals [minor component] and glass),

* Hypocrystalline (comprising both crystals [major component] and glass), and

* Holocrystalline.

When glass was present in an interval, we estimated the proportion of fresh and altered glass and noted the form of its occurrence (e.g., thin glass rinds, shards, or larger fragments). Other features of interest, such as particularly abundant fresh glass, devitrification, or gradations in grain size, were noted in the groundmass comments for that interval.

**3.3.1.2. Vesicularity**

Vesicles were primarily characterized by their size and abundance. Vesicles were often filled with secondary minerals, which were described in more detail during alteration logging (see Alteration petrology and structural geology). Abundance categories were defined as follows:

* Nonvesicular ($<$1% of the rock volume),

* Sparsely vesicular (1%–$<$10%),

* Moderately vesicular (10%–20%), and

* Highly vesicular ($>$20%).

Additional observations regarding vesicle shape (e.g., spherical, irregular vugs, and pipe vesicles) and general distribution were also noted. Vesicle concentration can vary significantly within a single lava flow or pillow lobe, and we commonly encountered bands and patches with higher vesicle concentrations in the core sections. We estimated the vesicle abundance within these bands and noted their location to distinguish them from the lower overall vesicularity of the interval.

**3.3.2. Rock interpretation**

To examine the nature of volcanic processes in the recovered core sequence, we further categorized basaltic intervals by their flow morphology. We applied the following classification scheme for lava flow types (for example images, see Figure F12):

* Pillow lava: 0.1–1 m in thickness with curved chilled margins (often glassy), spherulitic textures, and cryptocrystalline groundmass that decreases in grain size toward the glassy rims.

* Sheet/massive flows: thicker flows (1–3 m or more) that are more texturally uniform, sparsely vesicular, and characterized by a gradual increase in grain size toward the center of the flow. In addition to sheet flows associated with high-discharge rates, this category may include ponded lavas and similar forms in which individual lobes tend to coalesce.

* Lava: a generic term used when flow morphology is ambiguous and/or transitional between pillow lavas and sheet flows. This category likely includes many large pillows or lobate flows (1–2 m thick).

* Lava breccia: lava clasts within a sedimentary matrix. This category includes peperite, a sediment-matrix igneous breccia likely formed by lava mingling with or intruding into wet and/or unconsolidated sediment (after White et al., 2000).

**3.3.3. Contact types**

Glassy margins, chilled margins, and contact boundaries were documented for the top and bottom of each interval when observed. Contacts may be curved, irregular, or planar in shape, with sharp or gradational boundaries. We also noted whether they were (sub)horizontal, inclined, steeply dipping, or vertical. The following contact types were defined and described:
* Baked contact: boundary with sediments overprinted (baked).

* Chilled contact: lava that has clearly chilled against sediment or another rock unit.

* Chilled margin: rapidly chilled margin, for example with a cryptocrystalline border, or incomplete variolitic to glassy selvage.

* Contact not recovered.

We also noted our interpretation of contacts during the core description (e.g., the top or bottom of a lava flow, a unit boundary, the edge of a pillow lobe, and so on). Because it can be difficult to distinguish the top of a flow or lobe from the top of an eruptive unit, particularly in core sections with abundant pillow basalts and incomplete recovery, we caution that contacts designated as the top of a flow should not be interpreted as a boundary between eruptive units (although some likely are).

**3.4. Microscopic description**

We used thin section observations to complement and refine macroscopic rock core observations (Figure F13). Thin section descriptions include both primary (igneous) rock-forming minerals (including phenocrysts and groundmass) and a brief description of the nature and extent of alter-

<figure><img src="image_16.png" /></figure>

**Figure F12.** Sheet flows, pillow lavas, and peperite, Expedition 395. Orange line = transition from fairly continuous pieces of sheet flow lava to small pillow lava fragments.
ation. For each thin section, we documented the minerals present, their abundance (modal volume percent), size, shape, habit, and textural relationships. We also described the groundmass mineralogy and texture, vesicularity (abundance, size, and shape), glass abundance, and alteration. All thin section observations were entered into GEODESC using a customized thin section template.

Thin section descriptions include the following terms:

* Thin section domain: a summary description of the thin section or of each domain on the slide if it contains multiple domains (e.g., a slide that shows a large sedimentary vein [25% of the slide] in a basaltic matrix [75% of the slide]).

* Mineral shape: the dominant (>50% of crystals) shape of the olivine (ol), plagioclase (plag), and clinopyroxene (cpx) crystals in euhedral, subhedral, and anhedral shapes.

* Mineral habit: the dominant (>50% of crystals) habit of olivine, plagioclase, clinopyroxene crystals in equant, subequant, tabular, rounded, elongate, skeletal, acicular, hopper, or swallowtail.

* Plagioclase zoning: not observed, variable extinction, undulose extinction, oscillatory, sector zoning, patchy zonation, and other related observations.

* Plagioclase extinction: when measured, extinction angles are provided along with the estimated anorthite (An) content.

* Clinopyroxene habit: description of (groundmass) clinopyroxene, including interstitial, dendritic, mesostasis, and subophitic texture.

Additional features such as glomerocrysts and other aggregated clusters, alteration features and extent, and inclusions are also noted in the comments.

## 3.5. Chemical analysis

A handheld pXRF unit was used to conduct rapid in situ chemical analysis of rock surfaces (archive half) during Expeditions 395C and 395 (see **Geochemistry and microbiology**). Previous

<figure><img src="image_17.png" /><figcaption>**Figure F13.** Example igneous rock thin section report, Expedition 395.</figcaption></figure>
IODP expeditions demonstrated the utility of pXRF to provide quick chemical characterization of igneous rocks encountered in the core (e.g., Reagan et al., 2015; Ryan et al., 2017). Such data can be valuable for assessing broad chemical variations, determining potential unit boundaries, and helping target areas of interest for sample selection. In addition, samples were taken for shipboard ICP-AES analyses, usually coincident with thin section sampling (average of 1 sample per ~10 m when material was suitable). See **Geochemistry and microbiology** for pXRF and ICP-AES analytical procedures and calibrations.

# 4. Alteration petrology and structural geology

This section describes the procedures used for visual observations of alteration style, mineralogy, fracturing, and fracture and vesicle filling mineralogy in basalt cores from Expeditions 384, 395C, and 395. Descriptions were based on visual assessment of split cores, optical microscopy of sampled thin sections, and analysis using a scanning electron microscope (SEM) coupled with energy dispersive spectrometry (EDS) on selected thin sections. The resulting alteration observations, structural features, and thin section descriptions were recorded in GEODESC and are summarized in the site chapters.

## 4.1. Alteration

Estimates of the degree of alteration of the basalt core are reported for Holes U1554E, U1554F, U1555F–U1555I, U1562A, U1562B, U1563A, U1563B, and U1564F. Degree of alteration is assessed based on a visual estimate of the percentage of a core interval that has been altered to a secondary mineral assemblage; it is then assigned a corresponding rank (Table T1).

For a given core interval, the total percent of altered core is divided by the relative proportions of bulk disseminated alteration, alteration occurring in patches, or alteration occurring as a halo around a fracture (termed background, patch, and halo, respectively). A descriptive color is assigned to the alteration of the core interval. If more than one color is observed, the reported color is the dominant alteration color. Alteration mineralogy (Fe-oxide/oxyhydroxide, chlorite, clay, celadonite, quartz/silica, zeolite, carbonate, and sulfide) is visually assessed and presented as a modal percent of the total degree of alteration. It should be noted that for Sites U1554, U1555, U1562, and U1563, chlorites and different clays have been grouped together and described under the term “phyllosilicate.”

Finally, vesicles and vug spaces in a given core interval are visually assessed for the percent of these spaces that are filled with secondary minerals, the dominant color of these mineral fills, and secondary mineral assemblage where identifiable. For the latter, vesicles and vugs that show multiple mineral fills or variable color in their mineral fill are reported as zoned.

<table><caption>**Table T1.** Core alteration, Expedition 395. Download table in CSV format.</caption><thead><tr><td>Percent of core altered</td><td>Descriptor</td><td>Rank</td><td>Description</td></tr></thead><tbody><tr><td>0</td><td>Fresh</td><td>1</td><td>Core interval is fresh and contains no visible secondary mineralization or is basaltic glass.</td></tr><tr><td>&gt;0 to ≤25</td><td>Slightly altered</td><td>2</td><td>Core interval displays mostly preserved texture and mineral composition, with small amounts of secondary mineralization weakly disseminated throughout the core or concentrated in small patches or as narrow halos around a fracture/vein. Core may display slight color variations from its original fresh state.</td></tr><tr><td>&gt;25 to ≤50</td><td>Moderately altered</td><td>3</td><td>Core interval displays weak preservation of primary texture and mineral composition. Secondary mineral assemblages are more pervasive throughout the sample or as large patches or wide halos around fractures/veins. Core displays a color different from that of fresh rock.</td></tr><tr><td>&gt;50 to ≤75</td><td>Highly altered</td><td>4</td><td>Core interval displays limited preservation of original texture or mineral composition, and secondary mineralization is pervasive or exists as very wide alteration halos around fractures/veins that comprise most of the observable core. Core color is markedly changed from its fresh color.</td></tr><tr><td>&gt;75 to ≤100</td><td>Completely altered</td><td>5</td><td>Core interval shows little to no primary texture or mineral composition preservation, and secondary mineralization dominates the core composition. Core color is markedly different from that of fresh basalt core.</td></tr></tbody></table>
## 4.2. Structural geology

The term fracture is used here to refer to any observed mineral vein or any natural break in the core. The latter are identified only when a broken surface shows mineralization, slickensides, or observable and traceable offset geologic features across it. Top and bottom depths of each fracture are recorded as they occur in the core assuming that all core pieces are in their in situ orientation with respect to the borehole axis. Fracture properties were individually assessed for Holes U1554E, U1554F, U1555F–U1555I, U1562A, U1562B, U1563A, and U1563B. Individual fracture measurements are detailed in Table T2.

For Holes U1554E, U1554F, U1555F–U1555I, U1562A, U1562B, U1563A, and U1563B, individual fractures were visually assessed to identify alteration minerals present and estimate the percent abundance of the total fracture fill. Mineral species visibly assessed with confidence from core are carbonate, phyllosilicates (or clay and chlorite), epidote, Fe-oxides/oxyhydroxides, quartz/silica, celadonite, and zeolite. Finally, the width (to the nearest millimeter) and color of alteration halos around fractures are reported where present.

## 4.3. Thin section analysis

Thin sections of basalt core sampled from Holes 395C-U1554F, 395C-U1555I, 395C-U1562B, 395C-U1563B, and 395-U1564F were examined and described for alteration using a Zeiss Stereo binocular microscope. Thin sections of basalt core from Holes 384-U1555F and 384-U1555G were unavailable for examination during Expedition 395 and were therefore described on shore using a Nikon LV150ND optical microscope. Thin sections were examined under plane-polarized light (PPL), cross-polarized light (XPL), and reflected light (RL). PPL and XPL permit the identification of most minerals in the alteration mineral assemblage, and RL allows investigation and identification of optically opaque minerals. Alteration descriptions of the thin sections focused on identifi-

<table><caption>**Table T2.** Fractures, Expedition 395. Download table in CSV format.</caption><thead><tr><th>Fracture descriptor group</th><th>Description</th><th>Fracture descriptors</th></tr></thead><tbody><tr><td>Fracture type</td><td>Degree of mineral fill in structure</td><td>Unknown: only one side of the fracture is observable (unmated), which is mineralized or bears slickenlines<br>Partially open: the fracture is not completely mineralized; some open space remains<br>Vein: the fracture is completely mineralized; no open space remains</td></tr><tr><td>Fracture color</td><td>Dominant mineral fill color</td><td></td></tr><tr><td>Fracture width (mm)</td><td>Measured perpendicular across structure (true width)</td><td>Measured with ruler in mm when width is ≥1 mm; recorded as 0.5 for fractures &lt;1 mm wide<br>Null value when only one side of a structure is observable (unmated fractures)</td></tr><tr><td>Fracture shape</td><td>Morphology of individual fractures</td><td>Planar: single, isolated fracture has a simple planar structure<br>Curviplanar: single, isolated fracture has a simple curviplanar structure<br>Parallel: single planar to curviplanar fracture has a parallel to near-parallel orientation to another nearby single planar to curviplanar fracture<br>Anastomosing: single fracture has a complex morphology<br>Y-shaped: single fracture displays a single Y-shaped splay morphology at either or both ends<br>T-shaped: single fracture displays a single T-shaped splay morphology at either or both ends<br>Splayed: single fracture displays multiple morphologically complex splays at either or both ends<br>Stepped: single fracture displays a stepped-like morphology along its length<br>En echelon: single fracture displays an en echelon morphology</td></tr><tr><td>Fracture connectivity</td><td>How a structure interacts with other structures on the drill core</td><td>Crosscut: single fracture observed to cut across or be cut across by another fracture<br>Network: single fracture forms a morphologically complex network with more than one other fracture<br>Single: single fracture with no connection to another fracture</td></tr><tr><td>Fracture mineral texture</td><td>Macroscopic appearance of mineral fill</td><td>Amorphous: vein fill appears amorphous<br>Crypto-microcrystalline: vein fill is crystalline but not large enough to measure<br>Crystalline: vein fill is crystalline with crystal sizes ≥0.5 mm<br>Layered: vein fill shows obvious layering of one or more minerals</td></tr><tr><td>Fracture attitude</td><td>Visual description of the orientation of a structure with respect to the core axis</td><td>Horizontal: fracture oriented 80°–90° to core axis<br>Subhorizontal: fracture oriented 60°–80° to core axis<br>Inclined: fracture is oriented 30°–60° to core axis<br>Subvertical: fracture is oriented 10°–30° to core axis<br>Vertical: fracture is oriented 0°–10° to core axis</td></tr><tr><td>Average fracture mineral<br>crystal size (mm)</td><td>Average crystal size of observable vein fill</td><td>Measured to the nearest mm if crystals are obviously ≥0.5 mm to the naked eye, otherwise a null value is reported</td></tr></tbody></table>
cation of the alteration mineral assemblages of both the groundmass and phenocrysts, as well as
description of minerals found within vesicles and fractures.

4.4. Scanning electron microscope and energy dispersive spectrometry

During Expedition 395, an SEM with an EDS detector was used to perform analyses on a selection of basalt core thin sections sampled from Holes 395C-U1554F, 395C-U1555I, 395C-U1562B, and 395C-U1563B (SNE-4500M Plus SEM with a Bruker Quantax EDS detector). The SEM scans the surface of a thin section with a focused electron beam generated from a tungsten filament under vacuum. This beam causes the sample to emit electrons, which are collected by detectors in the SEM and used to produce an image. The same electron beam that images the thin section surface excites the sample, causing it to dissipate absorbed energy by ejecting a core-shell electron. This ejected electron is replaced by a higher energy outer-shell electron, releasing energy as an X-ray as it does so. The X-ray generated by this process has a characteristic spectrum based on the elemental atom it comes from. The positions of the peaks in the generated X-ray spectrum identify a sample's elemental composition, and the intensity of the signal corresponds to concentration of the element. As the electron beam is rasterized across a zone of interest on the sample surface, it generates a map of approximate elemental abundances that, for geologic samples, can be used to identify mineralogy and texture.

Selected basalt thin sections were carbon coated via a single carbon thread evaporation in a Leica EM ACE200 under vacuum using 15 pulses to generate a sufficiently thick coating. The Nanoeye software was used for SEM operation. Thin sections were imaged and analyzed with EDS at a working distance from the electron beam of 6 mm using an accelerating voltage of 15 kV and an emission current of 110 µA. Images were acquired using a secondary electron detector.

Once an image was captured, the Esprit Compact software was launched to perform EDS data acquisition. The EDS detector was configured for pulse throughput, maximum energy (which was set automatically for Expedition 395 analyses), and dwell time (which was set at 16 µs).

For the analyses performed during Expedition 395, we selected Si, O, Mg, Fe, Al, Ca, Na, K, S, Cl, Ti, Mn, Sr, and Ba. Carbon (C) was automatically detected and can be useful for characterizing carbonate minerals in samples but has a strong presence across the entire sample due to the carbon coating.

During Expedition 395, specific elements were chosen to define specific minerals: Si for quartz or
amorphous silica, Mg for olivine, Al for plagioclase, Fe for oxides or groundmass pyroxene, Ca for
calcite, and K for celadonite. Other altered phases like saponite or chlorite were shaded based on
Mg abundance. Also, minor elements were useful to display zonation in a single phase and/or
mineral.

Multiple options for EDS data acquisition were available: “map mode” collects EDS across the entire imaged portion of the sample, “object mode” collects EDS data from single points and defined polygons of the imaged sample, and “line mode” generates EDS data along a defined line across a region of interest on the imaged sample. This SEM-EDS methods guide was adapted from the SEM-EDS Bruker Quick Start Guide available on the Laboratory Manuals, Guides, and Resources page on the *JOIDES Resolution* Laboratories website (https://tamu-eas.atlas-sian.net/wiki/spaces/LMUG/pages/7341015792/SEM-EDS+Bruker+Quick+Start+Guide).

**5. Micropaleontology**

Biostratigraphy was based on calcareous nannofossils, planktonic foraminifers, and bolboforms that were studied in core catcher samples from all sites. Additional samples were taken from section halves at some sites to provide more refined age determinations or investigate particular levels of interest. Because of the COVID-19 pandemic, samples from Expedition 395C were shipped to participating micropaleontology laboratories for processing and study at the end of the expedi-
tion rather than being studied shipboard. Samples from Expedition 395 were processed and analyzed for microfossil content on board during the expedition.

Biostratigraphy focused mainly on the identification of biostratigraphic horizons (biohorizons) in the cores, generally the top (T) or base (B) of the stratigraphic range of a species but also including top common (Tc) and base common (Bc) occurrences. For nannofossils, we used the top acme (Ta), base acme (Ba), base paracme (Bpa), top paracme (Tpa), and crossover in abundance between two species (X). For planktonic foraminifers, we used coiling direction changes ($X_{d-s}$ for dextral to sinistral and $X_{s-d}$ for sinistral to dextral, as viewed upsection) in certain species. Biohorizons are assumed to result from biological events (bioevents) such as migrations, extinctions, and evolutionary transitions. These biohorizons have been assigned absolute ages based on calibrations from other sites, mainly referenced to the paleomagnetic reversal sequence. These ages may or may not be accurate for the study sites because of diachrony and/or imprecise calibration, especially when applying tropical or subtropical calibrations to these high-latitude successions. Identification of biohorizons in stratigraphic order allowed the identification of biostratigraphic zones (biozones, often referred to simply as zones). Details of the schemes for calcareous nannofossils, foraminifers, and bolboforms are provided in **Calcareous nannofossils, Planktonic foraminifers, and Bolboforms**, respectively.

For each site and each fossil group, a table of biohorizon depths was prepared. These tables were used in conjunction with the paleomagnetic reversal records to construct age versus depth plots for each site (see **Age model**).

For each site, the paleomagnetic and biostratigraphic data were collated on a common geologic timescale (see **Age model**). For the Paleogene, calibrated ages from Agnini et al. (2014) for calcareous nannofossils and Wade et al. (2011) for planktonic foraminifers were updated to the geomagnetic polarity timescale (GPTS) of Speijer et al. (2020).

For division of the formal series of the timescales and their geochronologic equivalent epochs, we use informal subseries/subepoch terms such as upper Pliocene when referring to strata and late Pliocene when referring to time. These have a lower case modifier to emphasize their informal status.

## 5.1. Calcareous nannofossils

Calcareous nannofossil assemblages were examined and described from standard smear slides made from core catcher samples (at about 10 m intervals) during Expedition 395 in multiple holes at each site. Additional toothpick samples were taken between core catcher samples from section halves, where possible, to refine the stratigraphic position of bioevents. Standard smear slides were made from bulk sediment. Slides were fixed with Norland optical adhesive Number 61 and cured under UV light for immediate biostratigraphic examination using a Zeiss Axioscope. Samples were analyzed under plane-transmitted, cross-polarized, phase contrast, and/or circular-polarized light using oil immersion at 1000× magnification. All photomicrographs were taken using a Spot Flex camera with IODP Image Capture 3.0 and Spot commercial software. Additional observations of sediment samples from some sites were made with a Hitachi TM3000 tabletop SEM to identify *Emiliania huxleyi* and verify the preservation state of calcareous nannofossils.

Nannofossil taxonomy follows Perch-Nielsen (1985), Young (1998), and Young and Bown (2014) as compiled in the online Nannotax 3 (https://www.mikrotax.org/Nannotax3) database. The zonal scheme of Martini (1971) was used for calcareous nannofossil biostratigraphy (Neogene NN code; Paleogene NP code) (Figure F14; Table T3). This zonation represents a general framework for the biostratigraphic classification of middle- to low-latitude nannofossil assemblages. The zonal scheme of Backman et al. (2012) as modified by Raffi et al. (2020) (CNPt-CNPI-CNM code), along with that of Agnini et al. (2014) for the Paleogene (Oligocene CNO code), providing a secondary framework that is more detailed in some intervals, is also shown. Zone NN13/14 is undifferentiated due to difficulties placing base common occurrence *Discoaster asymmetricus* and the poor calibration of this event (see discussion in Backman et al., 2012).
Biohorizons and bioevents, including age assignments, follow the latest compilation of Raffi et al. (2020) (Table T3). To this compilation we add two markers for the Oligocene/Miocene boundary: the top of *Cyclicargolithus abisectus* larger than 11 µm and top *Reticulofenestra bisecta*. Although neither of these bioevents are well calibrated and both may show some degree of latitudinal diachrony, they do have a long history of being used to broadly mark the Oligocene/Miocene boundary and/or as a temporal equivalent of the calcareous nannofossil Zone NP25/NN1 boundary across the Southern Ocean, equatorial Atlantic and Indian Oceans, and the Mediterranean Sea. Okada and Bukry (1980) noted an acme of large *C. abisectus* morphotypes at the top of the Oligocene in the Pacific and used the top of this event (the last common occurrence) as a subzonal marker. In the Indian Ocean, the top of these large forms, defined as >10 µm, consistently falls close to top *Furcatolithus ciperoensis* (24.35 Ma on timescale of Speijer et al., 2020) and top *R. bisecta* (Ocean Drilling Program [ODP] Sites 707–710 and 714), and at all these sites it falls below base *Sphenolithus delphix* (23.73 Ma) (Rio et al., 1990). A larger size cutoff of 11 µm was suggested for the biostratigraphic use of *C. abisectus* (Olafsson, 1992) based on the detailed morphometric

<figure><img src="image_18.png" /><figcaption>**Figure F14.** Biostratigraphic framework used during Expedition 395 (0–35 Ma). Bioevent calibrations for nannofossils and planktonic foraminifers are adjusted to those of *Geologic Time Scale 2020* (Gradstein et al., 2020). (Continued on next page.)</figcaption></figure>
study of ODP Site 667A in the equatorial Atlantic and ODP Site 709C in the equatorial Indian Ocean. With this size definition, Bown and Dunkley Jones (2012) determined the top common occurrence of *C. abisectus* to be immediately below top *F. ciperoensis* at eastern equatorial Pacific Integrated Ocean Drilling Program Site U1334, and this is the size definition we use herein. Similarly, although rare occurrences of *C. abisectus* >10 µm were recorded into the lower Miocene at ODP Site 900A on the Iberian margin, the last consistent occurrence of *C. abisectus* (>10 µm) is at the top of Zone NP25 (de Kaenel and Villa, 1996). From the same study, it is also noted that top *R. bisecta* (<10 µm) is coincident with top *F. ciperoensis* with the conclusion that this event can be of use in approximating the Oligocene/Miocene boundary. In the Mediterranean, Fornaciari and Rio

<figure><img src="image_19.png" /><figcaption>Figure F14 (continued).</figcaption></figure>
(1996) find the top common occurrence of *R. bisecta* between top *F. ciperoensis* and base *S. delphix*. Although some latitudinal diachrony has been suggested for top *R. bisecta* (Wei and Wise, 1989; Fornaciari et al., 1993), Berggren et al. (1995) places this event in Subchron C6Cn.2r (23.040–23.212 Ma) at high midlatitude ODP Site 703 (47°S) (based on the study of Wei [1991]), which is only slightly younger than its position in low- and midlatitude locations. In summary, although there is not a definitive calibration age for the two events in question, their consistent stratigraphic position relative to each other and between top *F. ciperoensis* and base *S. delphix* gives some confidence in using the age range of the later two bioevents (23.73–24.35 Ma) as an age constraint for both top *R. bisecta* and top *C. abisectus*.

<table><caption>**Table T3.** Cenozoic calcareous nannofossil bioevents, Expedition 395. B = base, Bc = base common, Ba = base acme, Bpa = base paracme, T= top, Tc = top common, Ta = top acme, Tpa = top paracme, X = abundance crossover. **Download table in CSV format.**</caption><thead><tr><th>Bioevent</th><th>Event</th><th>Age (Ma)</th><th>Zone base (Martini, 1971; Sissingh, 1977) and Agnini et al. [2014])</th><th>Zone/Subzone base (Raffi et al. [2020] after Backman et al. [2012])</th><th>Calibration references</th></tr></thead><tbody><tr><td>1</td><td>Bc Emiliania huxleyi</td><td>0.09</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>2</td><td>Ta Gephyrocapsa caribbeanica</td><td>0.28</td><td></td><td></td><td>Baumann and Freitag (2004)</td></tr><tr><td>3</td><td>B Emiliania huxleyi</td><td>0.29</td><td>NN21</td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>4</td><td>T Pseudoemiliania lacunosa</td><td>0.43</td><td>NN20</td><td>CNPL11</td><td>Raffi et al. (2020)</td></tr><tr><td>5</td><td>Ba Gephyrocapsa caribbeanica</td><td>0.56</td><td></td><td></td><td>Baumann and Freitag (2004)</td></tr><tr><td>6</td><td>T Reticulofenestra asanoi</td><td>0.91</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>7</td><td>T absence Gephyrocapsa (&gt;4 µm)</td><td>1.06</td><td></td><td>CNPL10</td><td>Raffi et al. (2020)</td></tr><tr><td>8</td><td>Bc Reticulofenestra asanoi</td><td>1.14</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>9</td><td>T Helicosphaera sellii (Atlantic)</td><td>1.24</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>10</td><td>T Gephyrocapsa (&gt;5.5 µm)</td><td>1.25</td><td></td><td>CNPL9</td><td>Raffi et al. (2020)</td></tr><tr><td>11</td><td>B Gephyrocapsa (&gt;5.5 µm)</td><td>1.59</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>12</td><td>T Calcidiscus macintyrei</td><td>1.60</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>13</td><td>B Gephyrocapsa (&gt;4 µm)</td><td>1.71</td><td></td><td>CNPL8</td><td>Raffi et al. (2020)</td></tr><tr><td>14</td><td>T Discoaster brouweri</td><td>1.93</td><td>NN19</td><td>CNPL7</td><td>Raffi et al. (2020)</td></tr><tr><td>15</td><td>T Discoaster pentaradiatus</td><td>2.39</td><td>NN18</td><td>CNPL6</td><td>Raffi et al. (2020)</td></tr><tr><td>16</td><td>T Discoaster surculus</td><td>2.53</td><td>NN17</td><td></td><td>Raffi et al. (2020)</td></tr><tr><td></td><td>Base Pleistocene</td><td>2.59</td><td></td><td></td><td></td></tr><tr><td>17</td><td>T Discoaster tamalis</td><td>2.76</td><td></td><td>CNPL5</td><td>Raffi et al. (2020)</td></tr><tr><td></td><td>Base upper Pliocene</td><td>3.60</td><td></td><td></td><td></td></tr><tr><td>18</td><td>T Sphenolithus spp.</td><td>3.61</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>19</td><td>T Reticulofenestra pseudoumbilicus</td><td>3.82</td><td>NN16</td><td>CNPL4</td><td>Raffi et al. (2020)</td></tr><tr><td>20</td><td>Bc Discoaster asymmetricus</td><td>4.04</td><td></td><td>CNPL3</td><td>Raffi et al. (2020)</td></tr><tr><td></td><td>Base Pliocene</td><td>5.33</td><td></td><td></td><td></td></tr><tr><td>21</td><td>T Discoaster quinqueramus</td><td>5.53</td><td>NN12</td><td>CNM20</td><td>Raffi et al. (2020)</td></tr><tr><td>22</td><td>Tpa Reticulofenestra pseudoumbilicus</td><td>7.10</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>23</td><td>Bc Discoaster surculus</td><td>7.88</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>24</td><td>B Discoaster quinqueramus</td><td>8.10</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>25</td><td>Bpa Reticulofenestra pseudoumbilicus</td><td>8.80</td><td></td><td>CNM15</td><td>Raffi et al. (2020)</td></tr><tr><td>26</td><td>Bc Discoaster pentaradiatus</td><td>9.37</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>27</td><td>B Discoaster brouweri</td><td>10.78</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>28</td><td>T Coccolithus miopelagicus</td><td>11.04</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td></td><td>Base upper Miocene</td><td>11.65</td><td></td><td></td><td></td></tr><tr><td>29</td><td>T Cyclicargolithus floridanus</td><td>~12.0</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>30</td><td>T Coronocyclus nitescens</td><td>12.45</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>31</td><td>T Calcidiscus premacintyrei</td><td>12.57</td><td></td><td>CNM9</td><td>Raffi et al. (2020)</td></tr><tr><td>32</td><td>B Calcidiscus premacintyrei</td><td>13.16</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>33</td><td>Tc Cyclicargolithus floridanus</td><td>13.33</td><td></td><td></td><td>Raffi et al. (2020)</td></tr><tr><td>34</td><td>T Sphenolithus heteromorphus</td><td>13.60</td><td>NN6</td><td>CNM8</td><td>Raffi et al. (2020)</td></tr><tr><td>35</td><td>T Helicosphaera ampliaperta</td><td>14.86</td><td>NN5</td><td></td><td>Raffi et al. (2020)</td></tr><tr><td></td><td>Base middle Miocene</td><td>15.99</td><td></td><td></td><td></td></tr><tr><td>36</td><td>Bc Sphenolithus heteromorphus</td><td>17.65</td><td></td><td>CNM6</td><td>Raffi et al. (2020)</td></tr><tr><td>37</td><td>X Helicosphaera euphratis-Helicosphaera carteri</td><td>20.98</td><td></td><td>CNM4</td><td>Raffi et al. (2020)</td></tr><tr><td>38</td><td>B Sphenolithus disbelemnos</td><td>22.90</td><td></td><td>CNM2</td><td>Raffi et al. (2020)</td></tr><tr><td></td><td>Base Miocene</td><td>23.04</td><td></td><td></td><td></td></tr><tr><td>39</td><td>T Reticulofenestra bisecta</td><td>23.73–24.35</td><td></td><td></td><td>See Methods text</td></tr><tr><td>40</td><td>T Cyclicargolithus abisectus</td><td>23.73–24.35</td><td></td><td></td><td>See Methods text</td></tr><tr><td>41</td><td>T Furcatolithus predistentus</td><td>26.93</td><td></td><td>CNO5</td><td>Agnini et al. (2014) updated to Speijer et al. (2020)</td></tr><tr><td></td><td>Base upper Oligocene</td><td>27.29</td><td></td><td></td><td></td></tr><tr><td>42</td><td>T Reticulofenestra umbilicus</td><td>32.02</td><td>NP23</td><td>CNO3</td><td>Agnini et al. (2014) updated to Speijer et al. (2020)</td></tr><tr><td>43</td><td>T Coccolithus formosus</td><td>32.96</td><td>NP22</td><td>CNO2</td><td>Agnini et al. (2014) updated to Speijer et al. (2020)</td></tr><tr><td></td><td>Base Oligocene</td><td>33.90</td><td></td><td></td><td></td></tr></tbody></table>
The following qualitative abundance codes were used in the GEODESC data entry program and uploaded to the LIMS database.

Total calcareous nannofossil abundance in the sediment was recorded as follows:

* D = dominant (>90% of sediment particles).

* A = abundant (>50%-90% of sediment particles).

* C = common (>10%-50% of sediment particles).

* F = few (1%-10% of sediment particles).

* R = rare (<1% of sediment particles).

* B = barren (none present).

Abundance of individual calcareous nannofossil taxa is based on specimens per FOV at 1000× magnification:

* V = very abundant (>100 specimens per FOV).

* A = abundant (10–100 specimens per FOV).

* C = common (1–9 specimens per FOV).

* F = few (1 specimen per 2–10 FOV).

* R = rare (1 specimen per 11–100 FOV).

* P = present (1 specimen per >100 FOV).

Preservation of calcareous nannofossils was recorded as follows:

* VG = very good (no evidence of dissolution and/or recrystallization; no alteration of primary morphological characteristics; specimens identifiable to the species level).

* G = good (little or no evidence of dissolution and/or recrystallization; primary morphological characteristics unaltered or only slightly altered; specimens identifiable to the species level).

* M = moderate (specimens exhibit some etching and/or recrystallization; primary morphological characteristics somewhat altered; however, most specimens identifiable to the species level).

* P = poor (specimens severely etched or overgrown; primary morphological characteristics largely destroyed; fragmentation has occurred; specimens often not identifiable at the species and/or generic level).

## 5.2. Planktonic foraminifers

Planktonic foraminifers were examined from core catcher samples and selected samples taken from split cores. Planktonic foraminifers were also examined from mudline samples from the top of selected holes. Mudline samples were stained with rose bengal to highlight living cells. Sample volumes of 10 or 20 cm³ were washed over 63 µm sieves. Harder samples were dried at ~40°C for ~12 h before washing in a sediment shaker. Some samples were treated with hydrogen peroxide. Very hard samples were frozen for 24 h and then placed in a freeze drier to remove all moisture before washing. Empty sieves were soaked in blue dye and then cleaned in an ultrasonic bath to minimize and identify any cross contamination between samples. Dried residues (>63 µm) were transferred to labeled glass vials, from which subsamples were examined on metal trays using a binocular Zeiss Discovery V8 stereomicroscope. Because the >63 µm residues are so variable in their nonforaminifer composition, a representative area of each residue was photographed. Apart from planktonic foraminifers, the following particle categories were recorded: siliceous plankton, spicules, quartz, rock fragments, glauconite/phosphate, pyrite, and tephra. For each of these, the following abundance categories relative to total sediment particles were estimated from visual examination of the dried sample in the >63 µm fraction as follows:

* D = dominant (>30% of sediment particles).

* A = abundant (10%-30% of sediment particles).

* F = few (5% to <10% of sediment particles).

* R = rare (1% to <5% of sediment particles).

* P = present (<1% of sediment particles).

* B = barren.
Planktonic foraminifer preservation as viewed under the light microscope was recorded as follows and is based on the Expedition 363 methods chapter (Rosenthal et al., 2018):

* E = excellent (most specimens have a glassy appearance, indicating very little recrystallization and very little evidence of overgrowth or dissolution, and little abrasion).

* VG = very good (some show minor evidence of diagenetic overgrowth, dissolution, or abrasion; recrystallization may or may not have occurred).

* G = good (some specimens show signs of significant overgrowth, dissolution, or abrasion and may show some infilling with cement or indurated sediment).

* M = moderate (most specimens show evidence of overgrowth, dissolution, and abrasion; tests generally infilled with cement or indurated sediment obscuring apertures).

* P = poor (substantial diagenetic overgrowth, dissolution, and abrasion; foraminifers can be fragmentary and difficult to identify because of major overgrowth and/or dissolution).

Most work focused on the sieved >150 µm size fraction for biostratigraphic purposes, but the 63–150 µm fraction was also examined for marker species, to assess fragmentation, and to scan for the smaller species. Selected specimens were imaged using a QImaging Image Capture system.

Abundances of planktonic foraminifer species in the >150 µm size fraction were estimated using the following scheme:

* D = dominant (>50% of the planktonic foraminifer assemblage).

* A = abundant (>20%–50% of the planktonic foraminifer assemblage).

* C = common (>10%–20% of the planktonic foraminifer assemblage).

* F = few (>5%–10% of the planktonic foraminifer assemblage).

* R = rare (1%–5% of the planktonic foraminifer assemblage).

* P = present (<1% of the planktonic foraminifer assemblage).

Abundances were not estimated for the 63–150 µm size fraction, for which species were simply recorded as present (P), even if they are numerically dominant.

Previous drilling in Pliocene to recent sediments of the high-latitude North Atlantic demonstrates that few of the standard planktonic foraminifer marker species used in the standard global tropical and subtropical biozonation are likely to be present at ~60°N, or if present they may occur only very rarely as occasional immigrants. Even in the warmer Miocene epoch, when latitudinal differences in assemblages are less marked, many tropical species are likely to be absent. As a result, there have been repeated efforts to develop regionally applicable biostratigraphic schemes for the North Atlantic based on endemic cold-water tolerant taxa (Poore and Berggren, 1975; Poore, 1979; Weaver and Clement, 1986; Spiegler and Jansen, 1989; Flower, 1999; Anthonissen, 2009; Sierro et al., 2009). We have reviewed these previous biostratigraphic schemes in light of a substantial body of work published on Mediterranean planktonic foraminifer biostratigraphy (e.g., Rio et al., 1984; Iaccarino, 1985; Lourens et al., 1996; Pasini and Colalongo, 2004; Hilgen et al., 2005; Lirer et al., 2019) and abstracted a list of 12 primary biohorizons covering the last 12 My. These biohorizons were numbered and, where necessary, recalibrated to the GPTS of Ogg (2020) with additions from Kochhann et al. (2016) as used herein, taking into account the errors produced by the sampling resolution of the biostratigraphy and paleomagnetics of the original published data. This biohorizon list was used to derive the Expedition 395 planktonic foraminifer biozonation, which is based principally on previous high-latitude biozonations of Poore and Berggren (1975) and Weaver (1987) with elements of the standard (sub)tropical biozonation of Wade et al. (2011) as updated by Raffi et al. (2020) combined with two new suggested zones (the *Globorotalia cibaoensis* and *Paragloborotalia continuosa* Zones) inserted to make a coherent scheme that is locally applicable. The list of datums is provided in Table T4. A detailed discussion of individual calibrations is reserved for a dedicated study. The list of biozone definitions is as follows (note that we use the terms bottom and top for the endpoints of stratigraphic ranges, rather than lowest occurrence, highest occurrence, first appearance datum, or last appearance datum):
* Neogloboquadrina pachyderma Partial Range Zone (PRZ), 1.82 Ma–recent.

* Definition: partial range of the nominate taxon between the bottom common occurrence of sinistral encrusted *N. pachyderma* and the recent (Weaver and Clement, 1986, modified).

* *Globoconella inflata* Lowest Occurrence Zone (LOZ), 2.06–1.82 Ma.

* Definition: biostratigraphic interval from the bottom occurrence of *G. inflata* to the bottom common occurrence of sinistral encrusted *N. pachyderma* (Weaver and Clement, 1986, modified).

* *Globigerina bulloides* PRZ, 2.26–2.06 Ma.

* Definition: partial range of the nominate taxon between the top occurrence of *Neogloboquadrina atlantica* and the bottom occurrence of *G. inflata* (Weaver and Clement, 1986).

* *Globoconella puncticulata*/*N. atlantica* Concurrent Range Zone (CRZ), 4.54–2.26 Ma.

* Definition: biostratigraphic interval between the bottom occurrence of *G. puncticulata* and the top occurrence of *N. atlantica* (Weaver and Clement, 1986, modified).

* *Globorotalia cibaoensis* LOZ, 9.44–4.54 Ma.

* Definition: biostratigraphic interval between the bottom occurrence of *G. cibaoensis* and the bottom occurrence of *G. puncticulata* (this study).

* *Paragloborotalia continuosa* PRZ, 10.54–9.44 Ma.

* Definition: partial range of the nominate taxon between the top occurrence of *Paragloborotalia mayeri* and the bottom occurrence of *G. cibaoensis* (this study).

* *Paragloborotalia mayeri* Highest Occurrence Zone (HOZ), 11.93–10.54 Ma.

* Definition: biostratigraphic interval between the top occurrence of *Fohsella fohsi* and the top occurrence of *P. mayeri* (Poore and Berggren, 1975, modified).

* *Fohsella fohsi* Taxon Range Zone (TRZ), 13.40–11.93 Ma.

* Definition: Total range of the nominate taxon (Wade et al., 2011).

<table><caption>**Table T4.** Calibration ages of North Atlantic planktonic foraminifer (F) and bolboform (B) bioevents from the upper Miocene to recent, Expedition 395. B = bottom, Bc = Base common, T = top, X = coiling reversal, d-s = dextral to sinistral. **Download table in CSV format.**</caption><thead><tr><th>Biohorizon</th><th>Marker species</th><th>GTS2020 age (Ma)</th><th>Calibration</th><th>(Sub)zone base</th></tr></thead><tbody><tr><td>F1</td><td>Bc Neogloboquadrina pachyderma (sin)</td><td>1.82</td><td>This study, based on Flower (1999), ODP Site 982</td><td>N. pachyderma PRZ</td></tr><tr><td>F2</td><td>B Globoconella inflata</td><td>2.06</td><td>This study, based on Flower (1999), ODP Site 982</td><td>G. inflata LOZ</td></tr><tr><td>F3</td><td>B Globigerina umbilicata</td><td>~2.07</td><td>This study, based on Rio et al. (1984), Mediterranean</td><td></td></tr><tr><td>F4</td><td>T Neogloboquadrina atlantica</td><td>2.26</td><td>This study, based on Flower (1999), ODP Site 982</td><td>G. bulloides PRZ</td></tr><tr><td>F5</td><td>B Globigerina cariacoensis</td><td>~2.26</td><td>This study, based on Poore and Berggren (1975), DSDP Site 116</td><td></td></tr><tr><td></td><td>Base Pleistocene</td><td>2.59</td><td></td><td></td></tr><tr><td></td><td>Base upper Pliocene</td><td>3.60</td><td></td><td></td></tr><tr><td>F6</td><td>B Globoconella puncticulata</td><td>4.54</td><td>This study, based on Weaver and Clement (1987), DSDP Site 609</td><td>G. puncticulata/N. atlantica CRZ</td></tr><tr><td>F7</td><td>B Globorotalia crassaformis</td><td>~4.60</td><td>This study, based on Weaver (1987), DSDP Site 606</td><td></td></tr><tr><td></td><td>Base Pliocene</td><td>5.33</td><td></td><td></td></tr><tr><td>F8</td><td>X d-s Neogloboquadrina atlantica</td><td>9.23</td><td>This study, based on Aksu and Kaminski (1989) and Shipboard Scientific Party (1987), DSDP Site 646</td><td></td></tr><tr><td>F9</td><td>B Globorotalia cibaoensis</td><td>9.44</td><td>Raffi et al. (2020), based on Chaisson and Leckie (1993), ODP Site 806</td><td>G. cibaoensis LOZ</td></tr><tr><td>F10</td><td>T Paragloborotalia mayeri</td><td>10.54</td><td>Raffi et al. (2020), based on Chaisson and Pearson (1997), ODP Site 925</td><td>P. continuosa PRZ</td></tr><tr><td>F11</td><td>B Neogloboquadrina acostaensis</td><td>10.57</td><td>Raffi et al. (2020), based on Lourens et al. (2004), Mediterranean sites</td><td></td></tr><tr><td></td><td>Base upper Miocene</td><td>11.65</td><td></td><td></td></tr><tr><td>F12</td><td>B Neogloboquadrina atlantica</td><td>11.76</td><td>This study, based on Neogloboquadrina group of Hilgen et al. (2003), Monte dei Corvi, Italy</td><td></td></tr><tr><td>F13</td><td>T Fohsella fohsi</td><td>11.93</td><td>Raffi et al. (2020) based on Pearson and Chaisson (1997), ODP Site 925</td><td>P. mayeri HOZ</td></tr><tr><td>F14</td><td>B Fohsella fohsi</td><td>13.40</td><td>Raffi et al. (2020) based on Pearson and Chaisson (1997), ODP Site 925</td><td>F. fohsi TRZ</td></tr><tr><td>F15</td><td>B Orbulina universa/O. suturalis</td><td>15.12</td><td>Raffi et al. (2020)</td><td></td></tr><tr><td></td><td>Base middle Miocene</td><td>15.99</td><td></td><td></td></tr><tr><td></td><td>Base Miocene</td><td>23.04</td><td></td><td></td></tr><tr><td>F16</td><td>Tc Chiloguembelina spp.</td><td>27.29</td><td>Wade et al. (2011) updated to Speijer et al. (2020)</td><td></td></tr><tr><td></td><td>Base upper Oligocene</td><td>27.29</td><td></td><td></td></tr><tr><td>F17</td><td>T Pseudohastigerina naguewichiensis</td><td>32.20</td><td>Wade et al. (2011) updated to Speijer et al. (2020)</td><td></td></tr><tr><td></td><td>Base Oligocene</td><td>33.90</td><td></td><td></td></tr><tr><td>F18</td><td>T Globigerinatheka index</td><td>34.50</td><td>Wade et al. (2011) updated to Speijer et al. (2020)</td><td></td></tr><tr><td></td><td>Base Pliocene</td><td>5.33</td><td></td><td></td></tr><tr><td>B1</td><td>T Bolboforma intermedia</td><td>5.85</td><td>This study, based on Spiegler (1999) and Drury et al. (2018)</td><td>B. costairregularis HOZ</td></tr><tr><td>B2</td><td>T Bolboforma metzmacheri</td><td>8.15</td><td>This study, based on Spiegler (1999) and Drury et al. (2018)</td><td></td></tr><tr><td>B3</td><td>B Bolboforma intermedia</td><td>8.18</td><td>This study, based on Spiegler (1999) and Drury et al. (2018)</td><td>B. intermedia TRZ</td></tr><tr><td>B4</td><td>B Bolboforma metzmacheri</td><td>9.89</td><td>This study, based on Spiegler (1999) and Drury et al. (2018)</td><td>B. metzmacheri LOZ</td></tr><tr><td>B5</td><td>T Bolboforma subfragoris</td><td>10.82</td><td>This study, based on Spiegler (1999) and Drury et al. (2018)</td><td>B. capsula PRZ</td></tr><tr><td></td><td>Base upper Miocene</td><td>11.65</td><td></td><td></td></tr></tbody></table>
**5.3. Bolboforms**

Bolboforms (members of genus *Bolboforma*) are an extinct group of small (generally <150 µm) mostly single-chambered microfossils, possibly produced by Chrysophyte algae (Spiegler and Spezzaferri, 2005). They occur in temperate to high-latitude sediments of both hemispheres and range in age from early Eocene to late Pliocene. Despite a somewhat patchy stratigraphic and geographic distribution, they provide a useful supplement to the biostratigraphy of the other main calcareous microfossil groups. They were studied in the samples taken for foraminifers using the same scales for preservation and relative abundance described in **Planktonic foraminifers**.

Bolboforms have been used to provide biostratigraphic age control at a number of sites across the North Atlantic, the most detailed record being that of Spiegler (1999) from ODP Site 982 in the Hatton-Rockall Basin. We used the record of Spiegler (1999) in combination with the updated interhole splice and astronomical age model for Site 982 of Drury et al. (2018) to calibrate a series of biohorizons to the expedition timescale (Table T4). The following bolboform biozonation is based on that of Spiegler (1999) adjusted to eliminate ambiguous “and/or” criteria in the biozone definitions:

* *Bolboforma costairregularis* HOZ, 5.85 Ma–? upper Pliocene, uncalibrated.

• Definition: biostratigraphic interval between the top occurrence of *Bolboforma intermedia* and the top occurrence of *B. costairregularis* (Spiegler, 1999, modified).

* Bolboforma intermedia TRZ, 8.18–5.85 Ma.

• Definition: total range of *B. intermedia* (Spiegler, 1999).

* *Bolboforma metzmacheri* LOZ, 9.89–8.18 Ma.

* Definition: biostratigraphic interval between the lowest occurrence of *B. metzmacheri* and the lowest occurrence of *B. intermedia* (Spiegler, 1999, modified).

* *Bolboforma capsula* PRZ, 10.82–9.89 Ma.

* Definition: biostratigraphic interval between the top occurrence of *Bolboforma subfragoris* and the lowest occurrence of *B. metzmacheri* (Spiegler, 1999, modified).

* *Bolboforma subfragoris* TRZ, ? upper Miocene, uncalibrated–10.82 Ma.

• Definition: total range of *B. subfragoris* (Spiegler, 1999).

**6. Physical properties**

Physical properties measurements are acquired to characterize the physical, chemical, and struc-
tural properties of the recovered sediment and basalt cores. The acquired data sets are also used
for correlation between holes from the same sites, as well as with downhole logging data. Physical
properties data sets include track scan measurements on whole-round sections (GRA bulk den-
sity, MS, P-wave logger [PWL], NGR, and X-ray imaging) and on section halves (MSP, color spec-
trometry [RGB], reflectance spectroscopy and colorimetry [RSC], and X-ray imaging). Discrete
MAD, thermal conductivity, and Vp caliper (PWC) measurements are made on specific sediment
core samples (Table T5). The data cleaning process is detailed in the description of each measure-
ment type and in **Note on data cleaning.**

**6.1. Laboratory workflow**

After initial curation, whole rounds from sedimentary depth intervals were first measured on the STMSL to provide MS and formation density data for stratigraphic correlation. During Expedition 395, measurements of O₂ concentration and temperature were performed on selected whole rounds after STMSL scanning. Cores were then left to equilibrate to room temperature (~4 h), during which X-ray images of the whole rounds were acquired on the XSCAN. Once the temperature was equilibrated, the core was measured on the WRMSL, which measures GRA bulk density, Vp, and MS, and then on the NGRL. Whole-round thermal conductivity measurements were typically made on core Section 4 after WRMSL scanning was complete; in deeper cores where sediment compaction made using whole-round cores impractical, thermal conductivity was measured on split core surfaces instead. Following completion of whole-round measurements, the core was split and moved to the SHIL and SHMSL, which measure RGB, MSP, and RSC. Subsequently, dis-
crete $V_p$ measurements were collected on section halves on the Section Half Measurement Gantry (SHMG). MAD was measured on samples collected from working halves.

For basalt core intervals, whole-round core was first cleaned and examined by the petrology team, and sections were prepared by the technicians and imaged in several orientations on the SHIL to construct a 360° view of the samples. Following imaging on the SHIL, the cores were placed back in the core liner before passing through a series of whole-round measurements on the WRMSL (GRA bulk density and MS) and the NGRL (NGR). The section halves were imaged using the XSCAN. Once the data were collected from the WRMSL and NGRL, thermal conductivity was measured on a piece of the split core. Discrete $V_p$ values and MAD were measured using the SHMG and pycnometer, respectively, on the cut sample cubes after magnetic measurements were made (See Paleomagnetism).

## 6.2. Multisensor core loggers

Expedition 384, 395C, and 395 STMSL measurements (MS and GRA bulk density) on the recovered sediments were made at 5 cm resolution (fast-track mode) to facilitate rapid stratigraphic correlation. Hard rock cores (lithified sediments and basement material) are sometimes recovered as disaggregated pieces rather than as continuous core, reducing the rock volume in the core liner. Therefore, GRA bulk density and MS measurements on these rock types may be underestimated but can still provide useful information for later stratigraphic correlation and can eventually be compared to discrete MAD and MSP measurements. QA/QC was monitored and maintained by running a core liner with freshwater through the STMSL after each full core length was measured.

<table><caption>**Table T5.** Measurement resolution, Expeditions 384, 395C, and 395. MSPOINT = MSP, PWB = P-wave bayonet, TCON = thermal conductivity. * = some variability in the measurement resolution that is dependent on the core recovery and changes in lithology. — = corresponding property was not measured. Download table in CSV format.</caption><thead><tr><th>Exp</th><th>Site</th><th>Hole</th><th>Type</th><th>GRA (cm)</th><th>MAD (m)</th><th>MS (cm)</th><th>MSPOINT (cm)</th><th>NGR (cm)</th><th>RGB (cm)</th><th>RSC (cm)</th><th>PWL (cm)</th><th>PWC (m)</th><th>PWB (m)</th><th>TCON (m)</th></tr></thead><tbody><tr><td>384</td><td>U1554</td><td>A</td><td>Sediment</td><td>5.0</td><td>~10</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>—</td><td>—</td><td>—</td></tr><tr><td>384</td><td>U1554</td><td>B</td><td>Sediment</td><td>2.5</td><td>~10</td><td>1.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>—</td><td>—</td><td>—</td></tr><tr><td>384</td><td>U1554</td><td>C</td><td>Sediment</td><td>2.5</td><td>—</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>—</td><td>—</td><td>—</td></tr><tr><td>395C</td><td>U1554</td><td>E</td><td>Sediment</td><td>2.5</td><td>~10</td><td>2.5</td><td>2.0</td><td>10</td><td>1</td><td>2.0</td><td>2.5</td><td>—</td><td>—</td><td>—</td></tr><tr><td>395C</td><td>U1554</td><td>F</td><td>Basalt</td><td>2.5</td><td>—</td><td>2.5</td><td>2.0</td><td>10</td><td>1</td><td>2.0</td><td>—</td><td>—</td><td>—</td><td>—</td></tr><tr><td>395</td><td>U1554</td><td>G</td><td>Sediment</td><td>2.5</td><td>~5</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.0</td><td>2.5</td><td>~10</td><td>~10</td><td>—</td></tr><tr><td>395</td><td>U1554</td><td>H</td><td>Sediment</td><td>2.5</td><td>—</td><td>2.5</td><td>2.5</td><td>10 or 20</td><td>1</td><td>2.0</td><td>2.5</td><td>~10</td><td>—</td><td>~10</td></tr><tr><td>384</td><td>U1555</td><td>F</td><td>Sediment</td><td>2.5</td><td>—</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>—</td><td>—</td><td>—</td></tr><tr><td>384</td><td>U1555</td><td>F</td><td>Basalt</td><td>2.5</td><td>—</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>—</td><td>—</td><td>—</td><td>—</td></tr><tr><td>384</td><td>U1555</td><td>G</td><td>Basalt</td><td>2.5</td><td>—</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>—</td><td>—</td><td>—</td><td>—</td></tr><tr><td>395C</td><td>U1555</td><td>H</td><td>Sediment</td><td>2.5</td><td>~10</td><td>2.5</td><td>2.0</td><td>10</td><td>1</td><td>2.0</td><td>2.5</td><td>—</td><td>—</td><td>~10</td></tr><tr><td>395C</td><td>U1555</td><td>I</td><td>Sediment</td><td>2.5</td><td>2 samples</td><td>2.5</td><td>2.0</td><td>10</td><td>1</td><td>2.0</td><td>~10*</td><td>—</td><td>—</td><td>~10*</td></tr><tr><td>395C</td><td>U1555</td><td>I</td><td>Basalt</td><td>2.5</td><td>—</td><td>2.5</td><td>2.0</td><td>10</td><td>1</td><td>2.0</td><td>—</td><td>~10</td><td>—</td><td>~10*</td></tr><tr><td>395C</td><td>U1562</td><td>A</td><td>Sediment</td><td>2.5</td><td>~10</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>—</td><td>—</td><td>~10</td></tr><tr><td>395C</td><td>U1562</td><td>A</td><td>Basalt</td><td>2.5</td><td>—</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>—</td><td>1 sample</td><td>—</td><td>1 sample</td></tr><tr><td>395C</td><td>U1562</td><td>B</td><td>Sediment</td><td>2.5</td><td>—</td><td>2.5</td><td>2.0</td><td>10</td><td>1</td><td>2.0</td><td>2.5</td><td>~1 per core</td><td>—</td><td>—</td></tr><tr><td>395C</td><td>U1562</td><td>B</td><td>Basalt</td><td>2.5</td><td>—</td><td>2.5</td><td>2.0</td><td>10</td><td>1</td><td>2.0</td><td>2.5</td><td>~1 per core</td><td>—</td><td>~10*</td></tr><tr><td>395</td><td>U1562</td><td>C</td><td>Sediment</td><td>2.5</td><td>—</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>~1 per core</td><td>—</td><td>~5–10</td></tr><tr><td>395C</td><td>U1563</td><td>A</td><td>Sediment</td><td>2.5</td><td>~10</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>—</td><td>—</td><td>~10</td></tr><tr><td>395C</td><td>U1563</td><td>A</td><td>Basalt</td><td>2.5</td><td>—</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>—</td><td>—</td><td>—</td><td>—</td></tr><tr><td>395C</td><td>U1563</td><td>B</td><td>Basalt</td><td>2.5</td><td>—</td><td>2.5</td><td>2.0</td><td>10</td><td>1</td><td>2.0</td><td>—</td><td>~10</td><td>—</td><td>~10</td></tr><tr><td>395C</td><td>U1564</td><td>A,B,C</td><td>Sediment</td><td>2.5</td><td>—</td><td>2.5</td><td>2.5</td><td>20</td><td>1</td><td>2.5</td><td>2.5</td><td>—</td><td>—</td><td>—</td></tr><tr><td>395</td><td>U1564</td><td>D</td><td>Sediment</td><td>2.5</td><td>~5</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>~10</td><td>~10</td><td>~10</td></tr><tr><td>395</td><td>U1564</td><td>E</td><td>Sediment</td><td>2.5</td><td>~5</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>~10</td><td>—</td><td>~10</td></tr><tr><td>395</td><td>U1564</td><td>F</td><td>Sediment</td><td>2.5</td><td>~5</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>—</td><td>~10</td><td>—</td><td>~10</td></tr><tr><td>395</td><td>U1564</td><td>F</td><td>Basalt</td><td>2.5</td><td>~10</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>—</td><td>~5</td><td>—</td><td>~5</td></tr><tr><td>395</td><td>U1602</td><td>A</td><td>Sediment</td><td>2.5</td><td>—</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>—</td><td>—</td><td>—</td></tr><tr><td>395</td><td>U1602</td><td>B</td><td>Sediment</td><td>2.5</td><td>~5</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>~10</td><td>~10</td><td>~10</td></tr><tr><td>395</td><td>U1602</td><td>C</td><td>Sediment</td><td>2.5</td><td>~5</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>2 samples</td><td>—</td><td>—</td></tr><tr><td>395</td><td>U1602</td><td>D</td><td>Sediment</td><td>2.5</td><td>~5</td><td>2.5</td><td>2.5</td><td>10 or 20</td><td>1</td><td>2.5</td><td>2.5</td><td>~10*</td><td>—</td><td>~10*</td></tr><tr><td>395</td><td>U1602</td><td>E</td><td>Sediment</td><td>2.5</td><td>~2–10</td><td>2.5</td><td>2.5</td><td>10</td><td>1</td><td>2.5</td><td>2.5</td><td>~10*</td><td>—</td><td>~10</td></tr></tbody></table>
Expedition 385, 395C, and 395 WRMSL measurement (MS, GRA bulk density, and PWL) resolution was 2.5 cm for both sediment and basalt cores. QA/QC was monitored and maintained by running a core liner with freshwater through the WRMSL after each full core length was measured. WRMSL measurements are most accurate on a liner completely filled with core that experienced minimal drilling disturbance. A core liner diameter of 66 mm is assumed for hard rock density (GRA bulk density) calculations, despite the fact that the liner is often filled less than 100%, usually resulting in underestimated values. WRMSL PWL measurements are susceptible to error depending on the quality of the coupling of the sensors with the core through the liner. When air or fluid is present around the rock in the liner, PWL measurements are of lower confidence. This issue is more common when the core is bisected during cutting with the XCB system or when using a RCB bit (e.g., lithified sediments and basalt core). Accordingly, WRMSL PWL was used only for the sediment intervals.

### 6.2.1. Gamma ray attenuation

The GRA densitometer on the WRMSL operates by passing gamma rays from a ¹³⁷Cs source down through a whole-round core section into a 75 mm × 75 mm sodium iodide detector located directly below the core. Gamma rays with an energy peak at 662 keV are attenuated by Compton scattering as they pass through the core (Evans, 1965; Harms and Choquette, 1965). The resultant gamma ray count is proportional to bulk density and shows clear variations with sediment composition and compaction and within the basalts. Calibration of the GRA densitometer is performed using core liners filled with seawater and aluminum density standards. Recalibration is performed as needed if the value of the freshwater QA/QC standard run, which is run as a pusher after every full core, deviates significantly (more than ~2%) from 1 g/cm³. The spatial resolution of the GRA densitometer is <1 cm.

GRA bulk density data were cleaned by removing values that coincide with foam pieces and physically improbable data such as values below water density (1 g/cm³). These spurious values were changed to NaN to designate not a number, and the cleaned data were used to generate the plots used in the Physical properties and Lithostratigraphy sections in the site chapters (see PHYSPROP in Supplementary material). Further evaluation of the measurements can be made by comparing the GRA bulk density and MAD measurements against density wireline logs.

### 6.2.2. Magnetic susceptibility

MS (k) is a dimensionless measure of the degree to which a material can be magnetized by an external magnetic field, given by

$$k = \frac{M}{H},$$

where M is the magnetization induced in the material by an external field strength H. MS responds to variations in the type and concentration of magnetic grains, making it useful for identifying compositional variations and alteration in sediment and hard rock core. In the case of sediments, MS can often be related to mineralogical composition (e.g., siliciclastic versus carbonate material). Water and plastics (e.g., core liner) have a slightly negative MS. Both the STMSL and WRMSL incorporate a Bartington Instruments MS2 meter coupled to an MS2C sensor coil with a diameter of 8.8 cm that operates at a frequency of 565 Hz (Bartington Instruments, 2011).

STMSL and WRMSL MS measurements are reported in instrument units (IU) because the core mass is not measured prior to data acquisition and the internal volume cannot be determined until the core is split. The correction for the volume does not change the order of magnitude of the measured susceptibility values, so the results are comparable with the susceptibility measured using the paleomagnetism equipment, which also reports data using instrument units.

The MS2C coil was calibrated with a homogeneous mixture of magnetite and epoxy in a 40 cm long piece of core liner to an accuracy of ±5%. The loop sensor averages across an interval of ~8 cm of a section, creating a smoothed data set for a continuous core section. A result of this smoothing is that MS is underestimated in sections that do not contain continuous core over a given 8 cm interval. MS data were cleaned post acquisition by removing unrealistic values ≤0 and data acquired on foam pieces and core gaps. Such erroneous data were set to NaN in the cleaned
data set. The cleaned data are presented in the figures here; however, note that the LIMS database
contains the uncleaned record.

**6.2.3. P-wave velocity**

The *V*<sub>p</sub> of whole-round sediment core was measured with the PWL, which is incorporated into the WRMSL. The PWL uses a 500 kHz compressional wave pulse transmitted across the core liner (orthogonal to depth) between two transducer-coupled calipers. Coupling between the calipers and the core liner is aided by water continuously dripping across the caliper surfaces. The pulse waveform is bandpass filtered between 0.4 and 1.0 MHz, stacked, summed, and ensemble-averaged to allow for automatic first arrival picking by the integrated WRMSL software. The PWL measurements were automatically corrected for the effects of the acrylic liner and calibrated using known velocities of a freshwater-filled liner and aluminum standards. XCB and RCB coring often yield core that does not fill the core liner, leading to air-filled voids, so WRMSL PWL measurements made on sediment cores collected using the XCB system should be treated with caution, and WRMSL PWL data were not measured on core recovered with the RCB system. WRMSL PWL data were cleaned by removing unrealistic *V*<sub>p</sub> measurements below that of water (1490 m/s), as well as measurements made on foam pieces and core gaps. Where erroneous data were removed, they were replaced in the cleaned data set by the value NaN as presented in the figures; the LIMS database contains the full, uncleaned record.

**6.2.4. Natural Gamma Radiation Logger**

NGR occurs primarily as the result of the decay of <sup>238</sup>U, <sup>232</sup>Th, and <sup>40</sup>K. The NGRL detector unit was calibrated using <sup>137</sup>Cs and <sup>60</sup>Co sources and identifying their peaks at 662 and 1330 keV, respectively. A single NGRL run consists of two sets of measurements by eight sensors, spaced 20 cm apart. The two sets of measurements are offset by 10 cm, which yields a total of 16 measurements equally spaced 10 cm apart over a 150 cm long section of core. In some instances, for operational reasons when time was limited, the core sections were only measured at one position (20 cm) in the NGRL for faster processing. For Expeditions 384, 395C, and 395, each measurement was acquired using 300 s of count, resulting in a measurement time of 600 s per core for most cores. The quality of the energy spectrum measured from a core depends on the concentration of radionuclides in the sample and on the counting time, with higher times yielding more clearly defined spectra. Sections less than 50 cm in length were not typically measured with the NGRL because of the constraints imposed by the sensor geometry.

**6.2.5. X-Ray Linescan Logger**

The XSCAN was installed aboard *JOIDES Resolution* in 2023 and was used during Expedition 395 but not during Expeditions 384 or 395C.

The XSCAN collects linescan X-radiographs from whole-round and split cores. The XSCAN source and detector can be rotated around the core material to produce linescans with different view angles to create pseudo-CT core scans. The XSCAN is comprised of an X-ray scanner with a 210 W, 160 kV, 1.3 mA constant potential X-ray source and linescan detector. The source is a Spellman XRBD 160PN210 Monoblock X-ray generator with a 0.5 mm focal spot. The beam angle is 90° × 12° and is located ~36 cm from the source. The detector is a Hamamatsu C12300-321, composed of a charge-coupled device sensor with a ~22 cm FOV using time-delayed integration and a resolution of 48 µm per pixel. Imaging acquisition and processing were completed in the IMS system (Version 14). Processing of images from Expedition 395 consisted of black and white correction and image cropping. XSCAN images can facilitate the imaging of geologic structures and objects such as fractures, ice-rafted debris, and materials with distinct densities (e.g., alteration zones and oxide and sulfide concentrations). Sediment cores were measured using energies between 90–100 kV and 0.80–0.90 mA, and basalt cores were measured using energies between 100–110 kV and 0.90 mA. Additional processing was applied to images of the basalt sections by modifying smoothing functions on the image histograms so that features such as veins, fractures, and altered zones are more apparent.
**6.3. Section Half Multisensor Logger**

Following core splitting, photography, and description, archive-half sections were passed through the SHMSL. The SHMSL nondestructively collects MSP, RGB, and RSC data. Measurements were made every 1.0, 2.0, or 2.5 cm for both sediment and basalt, as detailed in the site chapters (Table T5). SHMSL measurements are most accurate on cores that completely fill the liner and have a flat split surface with minimal drilling disturbance.

**6.3.1. Point magnetic susceptibility**

MSP was measured using a Bartington Instruments MS2E point sensor. A flush contact between the probe and the archive halves and protection of the probe and core is facilitated by covering sediment section halves with low-density polyethylene wrap. The instrument collects and averages three measurements made at 1 s intervals to an accuracy of 5%. Before each measurement, the probe is zeroed in air and a background magnetic field is measured and removed from the data. A built-in laser surface analyzer aids in the recognition of irregularities in the split core surface (e.g., cracks and voids) and provides an independent check on the fidelity of SHMSL measurements, which is especially crucial in the basalt sections. Differences may arise between the SHMSL and WRMSL MS data from differences in their frequency (Dearing et al., 1996), as well as the averaging point data compared to continuous loop sensor measurements, which averages across ~8 cm of core. Because it is difficult to isolate these factors, absolute differences between the two MS systems are expected. MSP data were cleaned by removing unrealistic values ≤0 and removing measurements made on foam pieces and over core gaps, which were replaced by the value NaN. The cleaned data are presented in the figures; the LIMS database contains the full uncleaned record.

**6.3.2. Digital imaging: color reflectance and colorimetry**

The reflectance of visible light from the archive halves of sediment and basalt cores was measured using an Ocean Optics USB4000 spectrophotometer mounted on the automated SHMSL. Measurements were taken at 1.0–2.5 cm spacing (resolution is specified in the site chapters; Table T5) to provide a high-resolution stratigraphic record of color variation for visible wavelengths. Empty intervals, voids, and cracks were skipped to avoid spurious measurements. Intervals where the tops of flat hard rock surfaces were below the level of the core liner were raised by adding support matting or foam beneath each hard rock piece to ensure good contact with the sensor. Each measurement was recorded in 2 nm wide spectral bands from 400 to 700 nm. The colorimetry and reflectance data are reported using the L*a*b* color system, in which L* is lightness, a* is redness (positive) versus greenness (negative), and b* is yellowness (positive) versus blueness (negative). The color reflectance spectrometer calibrates on two spectra, pure white (reference) and pure black (dark). Color calibration was conducted approximately once every 6 h. Data cleaning of these data sets consisted of removing unrealistic values, especially from intervals measured over foam pieces and core gaps. The cleaned color reflectance data are presented in the figures here; the LIMS database contains the full uncleaned record.

**6.4. Discrete measurements**

**6.4.1. Moisture and density**

Discrete (~10 cm³) sediment sample cubes were taken from the working halves of sediment cores for MAD measurements. In indurated sediment and basalt, discrete cubes were extracted for MAD analyses, which can also be used for discrete PWC measurements and paleomagnetism where desired. MAD samples were used to measure the wet and dry bulk density, grain density, water content, and porosity following methods presented in Blum (1997), which are briefly outlined below.

Preweighed and numbered 16 mL Wheaton glass vials were used to process and store the sediment samples. Following measurement of wet mass, samples were dried in a convection oven for 24 h at 105° ± 5°C. Dried samples were then cooled in a desiccator for at least 2 h before the dry mass and volume were measured. Wet and dry sample masses were measured to a precision of 0.005 g using a dual Mettler Toledo (XS204) electronic balances apparatus, with one balance act-
ing as a reference. A standard with a comparable mass to the sample was placed on the reference balance, and the computer averaging system compensated for the ship's motion by taking multiple measurements, typically 300 per sample.

Dry sample volumes were determined using the hexapycnometer system of a six-celled custom-configured Micrometrics AccuPyc 1330TC helium-displacement pycnometer. The system measures dry sample volume using pressurized He-filled chambers, where the precision of each cell is 1% of the full-scale volume. Volume measurements are preceded by three purges of the sample chamber with helium. For each measurement, five cells containing unknowns and one cell containing two stainless steel calibration spheres with a total volume of ~10 cm³ were run. Calibration spheres were sequentially cycled through the cells to identify any systematic error and/or instrument drift. The volumes occupied by the numbered Wheaton vials were calculated before the expedition by multiplying each vial's weight against the average density of the vial glass. The fundamental relation and assumptions for the calculations of all physical properties parameters such as wet bulk density (pwet), dry bulk density (pdry), sample grain density (psolid), porosity (φ), and void ratio (VR) were included in the MADMax shipboard program set with the Method C calculation process (Blum, 1997).

Because of time and staff constraints, MAD was not measured on core collected during Expedition 384. During Expedition 395C, one MAD sample was processed per recovered sediment core. During Expedition 395, MAD sample selection did not duplicate depths across the holes drilled during Expedition 395C.

### 6.4.2. Discrete P-wave velocity

Discrete triaxial $V_p$ was measured using the SHMG on working halves with a typical frequency of one measurement per 10 m of core. PWC was measured using Panametrics-NDT Microscan delay line transducers transmitting at 0.5 MHz. The signal received through the section half or discrete sample was recorded by the Velocity Gantry 2.0.5.0 IODP software, where the peak of the first P-wave arrival was either automatically or manually chosen. In case of a weak signal, manual picking of the first arrival was performed. The distance between transducers was measured with a built-in linear voltage displacement transformer (LDVT). Calibration was performed daily with a series of acrylic cylinders of differing thicknesses and a known $V_p$ of 2750 ± 20 m/s. The system time delay determined from calibration was subtracted from the picked arrival time to give a traveltime of the P-wave through the sample. The thickness of the sample (calculated using the LDVT, in meters) was divided by the traveltime (in seconds) to calculate $V_p$ in meters per second. A clean first P-wave arrival can be difficult to pick depending on the material; therefore, distilled water was applied to the contacts between section half or sample cube and calipers to improve the reading. PWC measurements were acquired on average once per 5 m of core. For the basalts, PWC was measured on the cut cubes in all orthogonal directions to determine any velocity dependent anisotropy.

### 6.5. Thermal conductivity

Thermal conductivity is the coefficient of proportionality relating conductive heat flow to a thermal gradient (Blum, 1997). Thermal conductivity was measured aboard *JOIDES Resolution* during Expeditions 395C and 395 using the transient needle probe method in whole- or half-space geometry (Von Herzen and Maxwell, 1959) on a Teka Bolin TK04 system. Thermal conductivity measurements made with the needle probe were typically taken on the third or fourth section of each sediment core after whole-round sections had equilibrated to room temperature and prior to core splitting. The needle probe method was used in full-space configuration for soft sediments (Von Herzen and Maxwell, 1959). The needle probe was inserted into the unconsolidated sediment through 2 mm diameter holes drilled into the core liner roughly once per core. To measure a representative undisturbed interval, WRMSL MS data were used to determine appropriate locations because MS is generally lower in carbonate-rich intervals and higher in clay-rich intervals. Both were targeted to assess the thermal conductivity of these end-member lithologies. During Expedition 395, the needle probe did not yield reliable data, so the decision was made to change to the half puck probe early on. The half puck probe was placed on the working-half section and secured with a Velcro strap to ensure good contact between the core and the probe during measuring.
<table><caption>**Table T6.** Edge effect cleaning, Expedition 395. Resolution denotes edges that were cleaned from the tops and ends of every section to account for soupy behavior and instrument response function. **Download table in CSV format.**</caption><thead><tr><td>Physical properties data</td><td>Edge effect cleaning resolution (cm)</td></tr></thead><tbody><tr><td>MS (WRMSL)</td><td>10</td></tr><tr><td>MS (SHMSL)</td><td>10</td></tr><tr><td>GRA (WRMSL)</td><td>10</td></tr><tr><td>P-wave logger</td><td>10</td></tr><tr><td>NGR</td><td>10</td></tr><tr><td>PWC</td><td>NA</td></tr><tr><td>PWL</td><td>NA</td></tr><tr><td>PWB</td><td>NA</td></tr><tr><td>MAD</td><td>NA</td></tr><tr><td>RGB (SHMSL)</td><td>5</td></tr><tr><td>Colorimetry (SHMSL)</td><td>5</td></tr></tbody></table>

For hard rock, thermal conductivity measurements were made on split core pieces ≥10 cm long. The split samples were first saturated in ambient temperature seawater for 4 h with a vacuum pump to aid in the full saturation of pore space. A puck with the measurement probe attached was placed on the split face of the core piece and secured with a rubber band. Three steps of heating and cooling were completed to make the thermal conductivity measurement, and the mean of these three values was used as the final thermal conductivity value.

Combining core thermal conductivity measurements of the sediments with downhole formation temperatures collected using the APCT-3 tool enabled calculation of an approximated heat flow. First, depth (using the CSF-A scale) was divided by the thermal conductivity estimate (W/[m·K]) to yield thermal resistance (m²K/W). A linear trendline was fit to the thermal resistance against temperature plot to estimate thermal resistance for depths where the formation temperature measurements were acquired. The heat flow (W/m²) was estimated as the slope of the thermal resistance against temperature (in K).

## 6.6. Note on data cleaning

Physical properties figures presented in each site chapter were cleaned to account for section edge effect (Table T6). In addition, the observations presented for the downcore figures for each whole round were also subjected to a secondary filtering process to remove anomalous and unreasonable values; these corrections were specific to sites and can be found in the respective site chapters. The cleaned data sets are available in PHYSPROP in **Supplementary material**.

## 7. Stratigraphic correlation

Many of the Expedition 395 scientific objectives depend on the recovery of complete stratigraphic sections. Such sections cannot be recovered from a single IODP borehole because core recovery gaps or additions occur between successive cores despite 100% or more nominal recovery (e.g., Ruddiman, Kidd, Thomas, et al., 1987; Hagelberg et al., 1995; Acton et al., 2002a). The construction of a complete composite section, referred to as a splice, therefore requires the combination of stratigraphic intervals from two or more holes cored at the same site over similar depths. To maximize the probability of bridging gaps between successive cores in individual holes, the starting depths below seafloor from which cores are recovered are offset between holes. This practice ensures that most missing sedimentary sections from intercore gaps in a given hole are recovered in one or more adjacent holes. Usually, at least two complete holes and a third partial hole must be cored to recover a complete section using the APC system at a site.

The composite section and splice construction methodology employed during Expedition 395 follows the basic strategy originally developed during ODP Leg 138 (e.g., Hagelberg et al., 1992, 1995) and later refined during many other ODP legs and IODP expeditions, specifically Expedition 397 (Abrantes et al., 2024). This strategy is now common practice on all high-resolution paleoceanographic expeditions. Assembly and verification of a complete composite stratigraphic section
requires construction of the core composite depth below seafloor, Method A (CCSF-A), depth scale. The CCSF-A depth scale provides a common scale for the holes at a site that is different from the original CSF-A depth scale, which uses drilling measurement as the top depth and curated length as the bottom depth. It is also different from the DSF depth scale because of deviations in the length of core recovery as a result of expansion (common), compression, and core loss. The DSF, CSF-A, and CCSF-A depth scales are unique to each hole.

**7.1. Depth scale for individual holes**

The depth to the top of each core is based on the DSF depth scale, which is determined by the length of drill string below the rig floor to the top of the cored interval minus the length of drill string from the rig floor to the mudline (assumed to be the seafloor). The depth to a point along the core is determined by adding the position at which the point occurs to the core top depth. This is referred to as the CSF-A depth scale, which is equivalent to the ODP mbsf depth scale.

The zero-depth point of the mbsf scale is defined by the mudline in the first core of each hole. However, it is often difficult to tell whether this empirical mudline recovers the true sediment/water interface. Some holes are inadvertently (or purposely) started below this interface. In this case, the zero-depth point on the mbsf scale may be substantially offset from the zero-depth point in adjacent holes that successfully recover the sediment/water interface. The mbsf scale may also be inaccurate because of ship heave, tidal variations in sea level, and other sources of error. Tidal influence on depth was first predicted during ODP Leg 138 (Hagelberg et al., 1995) and was proven by correlation of affine offset changes and tide height during ODP Leg 202 (Shipboard Scientific Party, 2003). Tidal influence was not considered for the construction of the splices during Expedition 395.

**7.2. Depth scale from composite holes**

The goal of constructing a composite depth scale is to place coeval, laterally continuous stratigraphic features onto a common depth. This objective is achieved by shifting the CSF-A depth scales of individual cores to optimize correlation between holes. On the CCSF-A depth scale, the depths of the individual cores can only be shifted by one tie point between any two cores; it is therefore not corrected for differential expansion or contraction of the relative depth scale between the holes. Ultimately, this approach provides a good first-order correlation between cores from different holes. The CCSF-A scale provides a basis on which higher order correlations can be built to connect off-splice cores to the splice.

The mudline for the CCSF-A scale is the top of the first core with the most representative or best-preserved mudline. This mudline establishes the top of the stratigraphic section, and the core with this mudline becomes the anchor for the CCSF-A scale. It is typically the only core for which the depths are the same on both the CSF-A and CCSF-A scales. Each core downhole is tied to the composite section by adding or subtracting a depth offset (a constant) that best aligns the observed lithologic variations to the correlative variations for cores from adjacent holes. Provided that gaps between cores do not occur at the same stratigraphic position in offset holes and recovery is high, it should be possible to correlate each successive core downhole to a core from an adjacent hole. Gaps common to all holes cored at a site can occur, in which case there is a gap in the splice. In this case, cores farther down the hole can be appended to the composite section with the depth offset for the appended core adjusted to convey an estimate of the true size of the coring gap. For example, one could use the average growth factor (i.e., expansion) of the CCSF-A scale relative to the CSF-A scale, or where logging is available one could use continuous logging data from a hole at the site or observations from other nearby sites.

In the process of constructing the composite section, the CCSF-A scale is nearly always expanded relative to the CSF-A scale. This expansion, which is typically ~5%–15%, is mostly caused by decompression of the cores as they are brought to the surface, by stretching that occurs as part of the coring process, and/or by the curation practice in which material that has fallen downhole or gas expansion voids are curated as part of the core (e.g., Hagelberg et al., 1995; Acton et al., 2002a).
**7.3. Goals**

The goals for stratigraphic correlation for Expedition 395, in order of priority, are as follows:

* Guide the drilling process to ensure recovery of the most complete possible stratigraphic section.

* Establish a composite depth scale.

* Define a stratigraphically complete and representative sampling splice.

This first-order ship-based correlation is expected to be refined postcruise with the generation of adjusted or revised composite depth scales based on XRF data, which may also be used to refine linkages between core and logging depths at sites where logging was done.

**7.4. Splice**

The splice is a composite stratigraphic section that represents the complete record through inter-vals at a site and is composed of core sections from adjacent holes such that coring gaps in one hole are filled with core from an adjacent hole. An effort is also made to minimize the inclusion of disturbed sections or intervals of sediment fall-in (typically the uppermost ~10–100 cm of a core) or flow-in. Disturbed sections are identified by examining the cores and their photographs and X-rays. The splice ultimately should guide core sampling for high-resolution studies.

We tried to adhere to the following guiding principles while making the splice:

* Tie points were defined, where possible, close to stratigraphic intervals that showed reduced variability to minimize the possibility that splice jumps occur during important climate transitions.

* Where possible, we avoided using the first and last sections of cores where disturbance due to drilling artifacts (even if not apparent in core logging data) is most likely.

* We attempted to incorporate those parts of the stratigraphic sequence that in our judgment were most representative of the holes recovered and appeared to be the least disturbed.

* Where possible, we also considered future XRF core scanning efforts by making the splice be-tween two holes only, even if more holes were available for the covered stratigraphy. Likewise, where possible, preference was given to records from Expedition 395 over Expedition 395C to allow for a spliced X-ray image record because those were not acquired during Expedition 395C. However, the highest priority was to not compromise the quality of the splice, so when needed, intervals of a third hole were included to ensure stratigraphic continuity.

**7.5. Measurements and methods specific to Expedition 395**

MS data from whole-round measurements were used for near real-time correlation during coring operations. These data often reveal strong contrasts between lithologic sequences, and the data can be obtained shortly after the core is recovered on deck at 5.0 cm resolution on the STMSL to guide operational decisions. The whole-round MS data collected at 2.5 cm resolution using the WRMSL were used to construct the final shipboard splices. Final correlation was always primarily based on the WRMSL MS profiles, but when in doubt it was occasionally supplemented by whole-round density, NGR, and paleomagnetic data.

Hole-to-hole correlations were accomplished using the Correlator software (Version 4.0.1). Using Correlator, we generated standard affine tables, which list the offset that is added to each core to place it in the CCSF-A scale, and splice tables, which give the intervals that comprise the splice. The tables were uploaded to the LIMS database using the Stratigraphic Correlator Data Manage-ment application SCORS, which will provide composite depths in the CCSF-A scale.

If overlapping small gaps in recovery between holes were identified but at least two holes could still clearly be correlated to each other and to the downhole logging data, the composite depth scale was extended using the estimated gap sizes relative to the logging profiles. When the correla-tion between different holes was no longer possible, the composite depth scale was stopped. To estimate the sizes of inferred gaps for Sites U1554, U1562, and U1564, the MS profiles from down-hole logging were compared with the MS data from the WRMSL. For Site U1602, the downhole
logging MS data could not be easily correlated with the MSP data measured on the cores and was
therefore not used to assess the size of potential gaps in the recovered cores. Comparison of the
lower resolution NGR signals from the downhole logging and core point measurements suggests
that there are no large stratigraphic recovery gaps for the spliced interval at Site U1602. However,
because of the relatively low resolution of both NGR records and the edge effect for NGR as mea-
sured on cores, it was difficult to estimate the sizes of the gaps in correlation. Consequently, when
it was not possible to tie to another core, the next core used in the composite was simply appended
without modifying the distance between cores. At Sites U1555 and U1563, single holes were cored
through the sedimentary sequence, and therefore splices and composite depth scales were not
constructed.

8. Paleomagnetism

Paleomagnetic investigations were conducted on archive-half sections during Expeditions 384, 395C, and 395. Discrete samples were collected and analyzed only during Expeditions 384 and 395. The primary objectives were to determine directions of natural remanent magnetization (NRM) components, including magnetic polarity, and downhole variation of magnetic properties. Shipboard polarities were used to infer magnetostratigraphy in near real-time to inform operational decision making.

Routine measurements were carried out on archive halves using in-line stepwise alternating field (AF) demagnetization on a 2G Enterprises Model-760R-4K SRM equipped with direct-current superconducting quantum interference devices (DC-SQUIDs) and an in-line, automated AF demagnetizer capable of peak fields of 80 mT. Measurements of archive halves were conducted using the SRM software (IMS-SRM Version 10.2 for Expeditions 384 and 395C; IMS-SRM Version 14.0 for Expedition 395) assuming a sample area of 17.5 cm² for conversion to volume-normalized magnetization units (A/m).

The spatial resolution for archive-half measurements is a function of the integrated response func-
tion, with effective lengths of 7.36 cm for the X-axis, 7.22 cm for the Y-axis, and 9.12 cm for the Z-
axis (Acton et al., 2017). The practical noise level of the SRM is ~1 × 10⁻⁹ Am² and is primarily
controlled by the magnetization of the core liner and the background magnetization of the mea-
surement tray. In soft sediments, discrete samples were collected with Natsuhara-Giken cubes (2
cm external edge length and internal volume of ~7 cm³) (Figure F15B). Cubes were hand-pushed
or extracted from the working half of the core with the up arrow on the cube pointing upcore. In
lithified sediments and hard rocks, 2 cm cubes (8 cm³ sample volume) were cut with a parallel saw.
All discrete samples were subjected to AF demagnetization treatments using the DTECH (model
D-2000) AF demagnetizer or thermally demagnetized using a thermal specimen demagnetizer
(ASC Scientific model TD-48SC) and were measured on a spinner magnetometer (AGICO JR-
6A). To avoid contamination by the ambient magnetic field prior to shipboard measurements, the

<figure><img src="image_20.png" /></figure>

**Figure F15.** A. IODP paleomagnetic sample coordinates (modified after Richter et al., 2007). B. Natsuhara-Giken sampling cubes (7 cm³ volume) with sample coordinate system. Red etched arrow is parallel to the up arrow (oriented toward the top of the core) on the sample cube and points in –z-direction. C. Measurement positions and coordinates used in the JR-6A spinner magnetometer aboard *JOIDES Resolution*. D. SRM coordinate system used aboard *JOIDES Resolution*.
discrete samples were stored inside a cylinder made of three mu-metal shields, providing a suit-
able low-field environment.

Ocean drilling cores generally carry secondary remanence components or overprints, such as a viscous remanent magnetization, resulting in a steep downward-pointing component imparted by the drilling process (Acton et al., 2002b). To separate these overprints from the characteristic remanent magnetization (ChRM), stepwise AF demagnetization was performed. Low AF values were selected to balance the competing goals of timely core processing and identifying and/or removing any drilling overprints, and preserving the NRM for high-resolution measurements during postcruise research. Archive-half and discrete data collected on the pass-through SRM and spinner magnetometer, respectively, were uploaded to the LIMS database.

Stepwise demagnetization data were analyzed using principal component analysis (PCA) to define the ChRM (Kirschvink, 1980). Zijderveld demagnetization plots (Zijderveld, 1967), intensity of magnetization versus demagnetization steps, and equal area projections and PCA were conducted using the PuffinPlot software (Version 1.4.1; Lurcock and Florindo, 2019).

**8.1. Magnetic measurements on archive-half sections**

The NRM of archive-half sections was measured using the SRM. Stepwise AF demagnetization was performed on most archive-half sections using the SRM in-line AF demagnetizer, which applies a field to the X-, Y-, and Z-axes of the SRM in this fixed order (Figure F15).

The response functions of the pick-up coils of the DC-SQUID sensors have a full width of 7.25–9.15 cm at half height. Therefore, data collected within ~4 cm of piece margins (or voids) can be affected by edge effects and are treated with caution. For this reason, basalt fragments with dimensions smaller than 8 cm were not analyzed.

The resolution and the demagnetization step sequence were modified during the three expedi-
tions because of time constraints imposed by the laboratory workflow. Resolution varied from 1 to
5 cm spacing for sedimentary material and from 1 to 2 cm spacing for basalts, with a tray speed of
10 cm/s. Demagnetization steps were variable, ranging from NRM-only measurements (when
multiple holes were drilled at the same depth intervals) to demagnetizations up to 40 mT. The
resolution, measurement sequence steps, and spacing of each hole can be found in Table T7.

Measurement of basalt NRM and subsequent demagnetization steps was either 1 or 2 cm. Demagnetization went up to 25 or 30 mT, and steps were mostly every 5 mT (Table T7). During Expeditions 395C and 395, to avoid flux jumps and an excessive load on the SRM, selected pieces of core (>8 cm) from each section were individually measured in the SRM. This procedure also prevented smaller pieces of basalts from being unintentionally demagnetized.

AF demagnetization results from sediments and basalts were evaluated as downhole variations with depth. Inclination data were plotted downcore together with the NRM intensity and the low-field MS (or κ) measured on archive halves using the SHMSL (see Physical properties). For the purposes of comparison, these MSP measurements are referred to as MS in Paleomagnetism in each site chapter.

**8.2. Magnetic measurements on discrete samples**

During Expedition 384, a small set of discrete samples were taken from the working-half sections for MAD and magnetic property measurements (Blum et al., 2020). During Expedition 395, one to three discrete samples per 10 m were collected from working halves for both the sediments and the basalts, only at depth intervals that were not previously cored during Expeditions 384 or 395C. For the sediments, discrete sample locations were chosen preferentially in fine-grained intervals where drilling deformation was minimal or not visible.

Incremental AF demagnetization was performed until samples were completely demagnetized, generally up to 45 mT for the lower coercivity samples and up to 100 mT for high-coercivity samples. Thermal demagnetization was performed up to 400°–600°C at 25°–50°C steps until complete demagnetization was reached.
During Expedition 384, the anisotropy of magnetic susceptibility (AMS) was measured on an AGICO KLY4 instrument at a field of 200 A/m using the SUFAR (AGICO) program. The AGICO KLY4 measures AMS by rotating the sample along three axes, stacking the data, and calculating the best-fit second-order tensor. Expedition 395 used an AGICO MFK2 instrument operating at a 425 A/m field. Both instruments also measure the volume-normalized calibrated bulk susceptibility (χ). Data processing occurred in the same manner across both expeditions. AMS is a second-order tensor that can be used as a proxy for the orientation of the paramagnetic (mainly phyllosilicates) and ferromagnetic minerals in the sediments. It can be interpreted in terms of depositional processes because settling particles typically produce an oblate magnetic fabric with the minimum axis of susceptibility (κ₃) at the pole of the depositional plane, and the maximum (κ₁)

<table><caption>**Table T7.** Demagnetization parameters, Expedition 395. * = basement half cores, † = basement intervals smaller than 8 cm were not discarded from these measurements. Download table in CSV format.</caption><thead><tr><th>Hole</th><th>Section(s)</th><th>Spacing (cm)</th><th>Demagnetization steps (mT)</th></tr></thead><tbody><tr><td colspan="4"><strong>384-</strong></td></tr><tr><td>U1554A</td><td>1H-1A to 1H-4A</td><td>1</td><td>0-2-4-6-8-10-12-14-16-18-20-25</td></tr><tr><td>U1554A</td><td>2H-1A to 8H-7A</td><td>1</td><td>0-2-6-10-15-20-25</td></tr><tr><td>U1554B</td><td>1H-1A to 8H-7A</td><td>1</td><td>0-2-6-10-15-20-25</td></tr><tr><td>U1554C</td><td>1H-1A to 2H-2A</td><td>1</td><td>0-2-4-6-8-10-12-14-16-18-20-22-25</td></tr><tr><td>U1554C</td><td>2H-3A to 8H-7A</td><td>1</td><td>0-2-6-10-15-20-25</td></tr><tr><td>U1555F¹</td><td>1R-1A to 1R-2A</td><td>1</td><td>0-2-6-10-15-20-25</td></tr><tr><td>U1555F¹</td><td>3R-1A to 9R-1A</td><td>1</td><td>0-5-10-15-20</td></tr><tr><td>U1555G¹</td><td>2R-1A to 27R-3A</td><td>1</td><td>0-5-10-15-20</td></tr><tr><td colspan="4"><strong>395C-</strong></td></tr><tr><td>U1554E</td><td>1H-1A to 25X-4A</td><td>1</td><td>0-10-15-20-25-35</td></tr><tr><td>U1554E</td><td>26X-1A to 34X-7A</td><td>2.5</td><td>0-15-20-25-35</td></tr><tr><td>U1554E</td><td>35X-1A to 61X-7A</td><td>2.5</td><td>0-15-20-25</td></tr><tr><td>U1554E</td><td>62X-1A</td><td>2.5</td><td>0-5-10-15-20-25-30</td></tr><tr><td>U1554F</td><td>3R-1A to 3R-3A</td><td>2</td><td>0-10-15-20-25</td></tr><tr><td>U1554F*</td><td>3R-4A to 32R-3A</td><td>2</td><td>0-10-15-20-25</td></tr><tr><td>U1555H</td><td>1H-1A to 20X-5A</td><td>1</td><td>0-10-15-20-25-35</td></tr><tr><td>U1555I</td><td>2R-1A to 3R-3A</td><td>1</td><td>0-10-15-20-25-35</td></tr><tr><td>U1555I</td><td>3R-4A</td><td>1</td><td>0-10-20-25-30</td></tr><tr><td>U1555I*</td><td>4R-1A to 41R-2A</td><td>2</td><td>0-5-10-15-20-25-30</td></tr><tr><td>U1562A</td><td>1H-1A to 57F-4A</td><td>2.5</td><td>0-10-15-20-25</td></tr><tr><td>U1562A</td><td>58X-1A to 65X-1A</td><td>2.5</td><td>0-15-20-25</td></tr><tr><td>U1562B*</td><td>2R-1A to 32R-2A</td><td>2</td><td>0-10-15-20-25</td></tr><tr><td>U1563A</td><td>1H-1A to 48X-1A</td><td>2.5</td><td>0-10-15-20-25</td></tr><tr><td>U1563A</td><td>48X-2A to 48X-4A</td><td>2.5</td><td>0-15-20-25</td></tr><tr><td>U1563B</td><td>2R-1A to 2R-3A</td><td>2</td><td>0-10-15-20-25</td></tr><tr><td>U1563B*</td><td>3R-1A to 28R-1A</td><td>2</td><td>0-10-15-20-25</td></tr><tr><td>U1564A</td><td>1H-1A to 1H-7A</td><td>5</td><td>0-15-20</td></tr><tr><td>U1564B</td><td>1H-1A to 3H-7A</td><td>5</td><td>0-15-20</td></tr><tr><td>U1564C</td><td>1H-11A to 75X-7A</td><td>5</td><td>0-15-20</td></tr><tr><td colspan="4"><strong>395-</strong></td></tr><tr><td>U1554G</td><td>1H-1A to 40X-7A</td><td>5</td><td>NRM only</td></tr><tr><td>U1554H</td><td>1H-1A to 7H-6A</td><td>2.5</td><td>NRM only</td></tr><tr><td>U1554H</td><td>8H-1A to 34X-2A</td><td>2.5</td><td>0-10-15-20</td></tr><tr><td>U1554H</td><td>34X-3A to 38X-7A</td><td>5</td><td>0-10-15-20</td></tr><tr><td>U1562C</td><td>1H-1A to 1H-4A; 12H-2A to 53F-4A</td><td>5</td><td>0-10-15-20</td></tr><tr><td>U1562C</td><td>2H-1A to 12H-1A</td><td>2.5</td><td>0-10-15-20</td></tr><tr><td>U1564D</td><td>1H-1A to 51X-4A; 56X-1A to 74X-2A</td><td>2.5</td><td>0-10-15-20</td></tr><tr><td>U1564D</td><td>51X-5A to 55X-CCA</td><td>2.5</td><td>0-10-15-20-25-30</td></tr><tr><td>U1564E</td><td>1H-1A to 28X-7A</td><td>5</td><td>0-10-15-20</td></tr><tr><td>U1564F</td><td>2R-1A to 44R-1A</td><td>2.5</td><td>0-10-15-20-25-30</td></tr><tr><td>U1564F*</td><td>44R-2A to 68R-3A</td><td>1</td><td>0-5-10-15-20-25-30-35-40</td></tr><tr><td>U1564F*</td><td>69R-1A to 76R-2A</td><td>1</td><td>0-5-10-15-20-25</td></tr><tr><td>U1602A</td><td>1H-1A to 1H-6A</td><td>2.5</td><td>0-10-15-20</td></tr><tr><td>U1602B</td><td>1H-1A to 38F-4A</td><td>2.5</td><td>0-10-15-20</td></tr><tr><td>U1602C</td><td>1H-1A to 33F-4A</td><td>2.5</td><td>NRM only</td></tr><tr><td>U1602C</td><td>34F-1A to 39F-3A</td><td>2.5</td><td>0-10-15-20-25</td></tr><tr><td>U1602D</td><td>1H-1A to 52X-5A</td><td>2.5</td><td>0-10-15-20</td></tr><tr><td>U1602D</td><td>47X-CCA; 48X-CCA; 49X-CCA; 50X-CCA; 51X-CCA; 52X-6A to 66X-1A</td><td>2.5</td><td>0-10-15-20-25</td></tr><tr><td>U1602E</td><td>2R-1A to 31R-3A; 40R-6A; 52R-1A to 52R-3A</td><td>2.5</td><td>0-10-15-20-25</td></tr><tr><td>U1602E</td><td>31R-4A to 40R-5A; 41R-1A to 51R-2A; 52R-4A to 71R-3A; 72R-2A to 73R-1A; 74R-2A</td><td>2.5</td><td>0-10-15-20-25-30</td></tr><tr><td>U1602E</td><td>72R-1A; 73R-2A to 74R-1A; 74R-3A to 88R-2A</td><td>2.5</td><td>0-5-10-15-20-30</td></tr></tbody></table>
and intermediate (κ₂) susceptibility axes are girdled (κ₁ ≈ κ₃), defining a planar, near horizontal, gravity-induced settling fabric. If sediments are deposited by flowing water, the resulting AMS ellipsoid is characterized by a magnetic foliation oriented with the current; it can be either a horizontal or tilted (imbricated) foliation, and/or characterized by clustering of the κ₁ parallel to the flow direction. Disturbance by slumping or other deformation may yield triaxial fabrics whereby the three axes have different values (κ₁ ≠ κ₂ ≠ κ₃).

During Expedition 395, a subset of discrete samples was measured for anhysteretic remanent magnetization (ARM) and isothermal remanent magnetization (IRM). An ARM of 50 µT bias AC field at a 100 mT demagnetizing DC was imparted along the Z-axis of the samples using the DTECH AF demagnetizer, and remaining magnetization was measured using the JR-6A spinner magnetometer. The acquired ARM and IRM were subsequently demagnetized with the DTECH AF demagnetizer using the same steps used to demagnetize the NRM.

IRM was imparted to discrete samples using the ASC Scientific IM-10 impulse magnetizer. Fields of 100, 300, 500, and 1000 mT were applied to the samples. After each step, the acquired magnetization of the cubes was measured with the SRM. After the 1000 mT step, samples were demagnetized with the DTECH AF demagnetizer using the same steps used for NRM. The remaining magnetization after each step was measured using the SRM. After their complete demagnetization, a -100 mT field along the Z-axis was applied and the remaining magnetization was measured using the SRM.

Thermal demagnetization was performed on a subset of basement discrete samples. After measuring the NRM using the JR-6A spinner magnetometer, samples were heated to 50° and 100°C using the ASC Scientific TD-48 SC oven. The remaining NRM was measured after each temperature step using the JR-6A spinner magnetometer. Samples were then subjected to the MAD protocol for physical properties tests (see Physical properties) and returned to the paleomagnetic laboratory for further heating at 25° or 50°C increments up to 600°C, when most samples were fully demagnetized.

**8.3. Coordinates**

All magnetic data are reported relative to IODP orientation conventions as follows: +x is into the face of the working half, +y points toward the left side of the face of the working half, and +z points downcore. The relationship of the SRM coordinates (X-, Y-, and Z-axes) to the data coordinates (x-, y-, and z-directions) is as follows: for archive halves, x-direction = X-axis, y-direction = -Y-axis, and z-direction = Z-axis; for working halves, x-direction = -X-axis, y-direction = Y-axis, and z-direction = Z-axis (Figure F15).

**8.4. Core orientation**

Orientation of APC cores was achieved with the FlexIT Tool 0937 for a subset of cores from Expedition 384 and an Icefield MI-5 (2007, 2043, or 2052) for all other cores. These tools consist of triaxial magnetometers and accelerometers. These sensors provide an azimuthal correction for the core barrel that, combined with the local magnetic declinations, allows the measured NRM declinations to be transformed into true geographic coordinates. In the orientation deployment, the tool is connected to the core barrel with the double lines on the core liner at a fixed and known angle relative to its sensors. After Expedition 384, misalignment of 180° for the Icefield MI-5 2043 was avoided by regularly checking the alignment of the keys and using each Icefield tool with a specific pressure barrel and end seal (Blum et al., 2020).

**8.5. Magnetostratigraphy reference scale and interpretations**

The magnetostratigraphy at each site was constructed by correlating observed polarity sequences with a reference GPTS. The GPTS used for Expeditions 395C and 395 (Table T8) is the GPTS2020 synthesis of astronomical tuning of Cenozoic through the latest Cretaceous polarity zones presented in Ogg (2020).
The magnetozones were established from pass-through measurements after AF demagnetization using the inclinations from the maximum demagnetization step. The geomagnetic polarity sequence was then verified by the inclination for the ChRMs from the discrete samples.

For Holes U1562A, U1564D, U1602D, and U1602E, the edge effect was removed to better refine the magnetostratigraphy (Richter et al., 2007). For sedimentary rocks that formed in high latitudes, no polarity ambiguity arises and inclination only can be used to estimate the magnetic

<table><caption>**Table T8.** Cenozoic magnetic polarity chron nomenclature and age model as used in the GPTS (Ogg, 2020). For consistency throughout this volume, we use the stage boundaries as documented in table 29.8 in Raffi et al. (2020), although we note that in places these are not fully consistent with the reversal ages that are associated with the stage boundary. GSSP = Global Boundary Stratotype Section and Points. Download table in CSV format.</caption><thead><tr><th>Period</th><th>Epoch</th><th>Age/stage</th><th>Base age (Ma)</th><th>Chron</th><th>Polarity chron/subchron</th><th>Base of chron/subchron (Ma)</th><th>Duration (My)</th><th>Remarks</th></tr></thead><tbody><tr><td rowspan="12">Quaternary</td><td rowspan="12">Pleistocene</td><td rowspan="3">late (Tarantian)</td><td>11.8 ka</td><td rowspan="3">C1</td><td>Present</td><td>0.000</td><td></td><td></td></tr><tr><td>0.13</td><td>C1n (Brunhes)</td><td>0.773</td><td></td><td>Base of Middle Pleistocene (Ionian) is base of Brunhes Chron</td></tr><tr><td>0.773</td><td>C1r.1r (Matuyama)</td><td>0.217</td><td></td><td></td></tr><tr><td rowspan="3">middle (Ionian)</td><td>1.80</td><td>C1r.1n (Jaramillo)</td><td>1.070</td><td></td><td></td></tr><tr><td></td><td>C1r.2r</td><td>1.180</td><td></td><td></td></tr><tr><td></td><td>C1r.2n (Cobb Mountain)</td><td>1.215</td><td></td><td></td></tr><tr><td rowspan="3">early (Calabrian)</td><td>1.775</td><td>C1r.3r</td><td>0.560</td><td></td><td></td></tr><tr><td></td><td>C2n (Olduvai)</td><td>1.934</td><td></td><td>Base of Calabrian is in lower part of Olduvai Chron</td></tr><tr><td></td><td>C2r.1r</td><td>2.116</td><td></td><td></td></tr><tr><td rowspan="3">early (Gelasian)</td><td>2.59</td><td>C2r.1n (Feni)</td><td>2.140</td><td></td><td>Formerly named Reunion</td></tr><tr><td></td><td>C2r.2r (Matuyama)</td><td>2.595</td><td></td><td>Base of Pleistocene is near base of Matuyama Chron</td></tr><tr><td></td><td>C2An.1n (Gauss)</td><td>3.032</td><td></td><td>Gauss Normal Chron (C2An) contains two reversed intervals: Kaena (Chron 2An.1r) and Mammoth (Chron 2An.2r)</td></tr><tr><td rowspan="12">Pliocene</td><td rowspan="3">late (Piacenzian)</td><td>3.60</td><td rowspan="3">C2A</td><td>C2An.1r (Keana)</td><td>3.116</td><td>0.084</td><td></td></tr><tr><td></td><td>C2An.2n</td><td>3.207</td><td>0.091</td><td></td></tr><tr><td></td><td>C2An.2r (Mammoth)</td><td>3.330</td><td>0.123</td><td></td></tr><tr><td rowspan="7">early (Zanclean)</td><td>5.33</td><td>C2An.3n (Gauss)</td><td>3.596</td><td>0.266</td><td>Base of Piacenzian is base of Chron C2An.3n</td></tr><tr><td></td><td>C2Ar (Gilbert)</td><td>4.187</td><td>0.591</td><td>Gilbert Reversed Chron spans Chrons C2Ar through C3r</td></tr><tr><td></td><td>C3n.1n (Cochiti)</td><td>4.300</td><td>0.113</td><td></td></tr><tr><td></td><td>C3n.1r</td><td>4.493</td><td>0.193</td><td></td></tr><tr><td></td><td>C3n.2n (Nunivak)</td><td>4.631</td><td>0.138</td><td></td></tr><tr><td></td><td>C3n.2r</td><td>4.799</td><td>0.168</td><td></td></tr><tr><td></td><td>C3n.3n (Sidufjall)</td><td>4.896</td><td>0.097</td><td></td></tr><tr><td rowspan="12">Neogene</td><td rowspan="3">late (Messinian)</td><td>7.246</td><td rowspan="3">C3A</td><td>C3n.3r</td><td>4.997</td><td>0.101</td><td></td></tr><tr><td></td><td>C3n.4n (Thvera)</td><td>5.235</td><td>0.238</td><td>Base of Pliocene is in uppermost Chron C3r</td></tr><tr><td></td><td>C3r (Gilbert)</td><td>6.023</td><td>0.788</td><td></td></tr><tr><td rowspan="12">Miocene</td><td rowspan="3">late (Tortonian)</td><td>11.65</td><td rowspan="3">C3B</td><td>C3An.1n</td><td>6.272</td><td>0.249</td><td></td></tr><tr><td></td><td>C3An.1r</td><td>6.386</td><td>0.114</td><td></td></tr><tr><td></td><td>C3An.2n</td><td>6.727</td><td>0.341</td><td></td></tr><tr><td rowspan="3">late (Tortonian)</td><td></td><td>C3Ar</td><td>7.140</td><td>0.377</td><td></td></tr><tr><td></td><td>C3Bn</td><td>7.214</td><td>0.110</td><td></td></tr><tr><td></td><td>C3Br.1r</td><td>7.262</td><td>0.048</td><td>Base of Messinian is in lowermost Chron C3Br.1r</td></tr><tr><td rowspan="12">Miocene</td><td rowspan="3">late (Tortonian)</td><td></td><td rowspan="3">C4</td><td>C3Br.1n</td><td>7.305</td><td>0.043</td><td></td></tr><tr><td></td><td>C3Br.2r</td><td>7.454</td><td>0.151</td><td></td></tr><tr><td></td><td>C3Br.2n</td><td>7.499</td><td>0.043</td><td></td></tr><tr><td rowspan="7">late (Tortonian)</td><td></td><td>C3Br.3r</td><td>7.537</td><td>0.038</td><td></td></tr><tr><td></td><td>C4n.1n</td><td>7.650</td><td>0.113</td><td></td></tr><tr><td></td><td>C4n.1r</td><td>7.701</td><td>0.051</td><td></td></tr><tr><td></td><td>C4n.2n</td><td>8.125</td><td>0.424</td><td></td></tr><tr><td></td><td>C4r.1r</td><td>8.257</td><td>0.132</td><td></td></tr><tr><td></td><td>C4r.1n</td><td>8.300</td><td>0.043</td><td></td></tr><tr><td></td><td>C4r.2r</td><td>8.771</td><td>0.471</td><td>Cryptochron C4r.2r-1 is within Chron C4r.2r (~8.661–8.699 Ma)</td></tr><tr><td rowspan="12">Miocene</td><td rowspan="3">late (Tortonian)</td><td></td><td rowspan="3">C4A</td><td>C4An</td><td>9.105</td><td>0.334</td><td></td></tr><tr><td></td><td>C4Ar.1r</td><td>9.311</td><td>0.206</td><td></td></tr><tr><td></td><td>C4Ar.1n</td><td>9.426</td><td>0.115</td><td></td></tr><tr><td rowspan="3">late (Tortonian)</td><td></td><td>C4Ar.2r</td><td>9.647</td><td>0.221</td><td></td></tr><tr><td></td><td>C4Ar.2n</td><td>9.721</td><td>0.074</td><td></td></tr><tr><td></td><td>C4Ar.3r</td><td>9.786</td><td>0.065</td><td></td></tr><tr><td rowspan="3">late (Tortonian)</td><td></td><td>C5n.1n</td><td>9.937</td><td>0.151</td><td></td></tr><tr><td></td><td>C5n.1r</td><td>9.984</td><td>0.047</td><td></td></tr><tr><td></td><td>C5n.2n</td><td>11.056</td><td>1.072</td><td></td></tr><tr><td rowspan="5">late (Tortonian)</td><td></td><td>C5r.1r</td><td>11.146</td><td>0.090</td><td></td></tr><tr><td></td><td>C5r.1n</td><td>11.188</td><td>0.042</td><td></td></tr><tr><td></td><td>C5r.2r</td><td>11.592</td><td>0.040</td><td>Subchron C5r.2r-1 is within Chron C5r.2r (~11.263–11.308 Ma)</td></tr><tr><td></td><td>C5r.2n</td><td>11.657</td><td>0.065</td><td>Base of Tortonian is near base of Chron C5r.2n</td></tr></tbody></table>
polarity. The quality of the paleomagnetic data was improved by removing those intervals affected by core disturbance (e.g., soupy or flow-in intervals). Any polarity changes occurring at the beginning and end of core sections are treated with caution.

The polarities were indexed in numerical order from the top to bottom of each hole with the prefixes *n* for normal and *r* for reversed polarities. When possible, the interpretation of magnetic polarity intervals was provided, adopting the naming and numbering convention of the reference GPTS (Ogg, 2020). For the younger part of the timescale (Pliocene–Pleistocene), the traditional names were used to refer to chrons and subchrons (e.g., Brunhes, Jaramillo, Olduvai).

# 9. Geochemistry and microbiology

A full suite of shipboard geochemical data were collected during Expeditions 395 and 395C; however, only hydrocarbon gas concentration data were collected during Expedition 384. Unless noted, methods were identical for Expeditions 395 and 395C. Routine measurements included headspace analysis of hydrocarbon gases, in situ pore water oxygen measurements, IW chemistry (e.g., salinity, pH, alkalinity, major cations and anions, nutrients, and major and minor elements), loss on ignition (LOI), total carbon (TC), total inorganic carbon (TIC), total sulfur (TS; Expedition 395 only), and elemental compositions of sediments and basement rocks using ICP-AES. Additional geochemical analyses of basement rock chemistry were conducted using a handheld pXRF. All data generated by shipboard analyses were uploaded to the LIMS database. Samples for microbiological analyses, focused on culture-independent approaches, were obtained alongside geochemical measurements for shore-based processing and analyses.

## 9.1. Headspace hydrocarbon gas chemistry

Routine analyses of hydrocarbon gas concentrations in sediment cores is standard IODP procedure and ensures safe drilling operations (Kvenvolden and McDonald, 1986; Pimmel and Claypool, 2001). During Expeditions 395 and 395C, sediment samples for headspace gas monitoring were typically taken from the top of Section 3 (below the IW sample taken from the base of Section 2), or from the same whole-round core used for IW or microbiological sampling. During Expedition 384, sediments for headspace gas analyses were taken from the top of Section 7. Soft-sediment sampling consisted of a ~5 cm³ plug collected using a graduated syringe and extruded into a 21.5 cm³ glass serum vial with a crimped-seal aluminum cap and fluoropolymer/silicone septum. Consolidated or lithified samples were collected as chips of sediment that were placed in the vial and sealed. Vials were then heated in an oven at 80°C for 30 min.

A 5 cm³ aliquot of the evolved hydrocarbon gas was extracted from the headspace vial with a standard gas syringe and then manually injected into an Agilent 7890 Series II gas chromatograph (GC) equipped with a flame ionization detector set at 250°C to quantify concentrations of methane ($C_1$), ethane ($C_2$), ethylene ($C_2$=), propane ($C_3$), and propylene ($C_3$=). The injector consists of a 1/16 inch Valco union with a 7 µm screen connected to a Valco-to-Luer lock syringe adapter. This injector connects to a 10-port Valco valve that was switched pneumatically by a digital valve interface. The injector temperature was set at 120°C. Samples were introduced into the GC through a 0.25 cm³ sample loop connected to the Valco valve. The valve can be switched automatically to back flush the column. The GC column (2 mm inner diameter; 6.3 mm outer diameter) was packed with 80/100 mesh HayeSept (Restek). The GC oven program was maintained at 80°C for 8.25 min with a subsequent heat-up to 150°C at 40°C/min. Helium was used as the carrier gas, and the initial helium flow in the column was 30 mL/min. The helium flow was then ramped to 60 mL/min after 8.25 min to accelerate elution of $C_3$ and $C_3$=. The run time was 15 min. The GC was also equipped with an electronic pressure-control module to control the overall flow into the GC. Data were collected and evaluated using the Hewlett Packard 3365 ChemStation data processing software. The chromatographic response was calibrated daily using nine gas standards with variable quantities of low-molecular weight hydrocarbons provided by MESA Calibration Gas Standards. Table T9 lists precision and detection limits for the headspace gas analyses during Expeditions 384, 395, and 395C. Concentrations of hydrocarbon gases are reported in parts per million by volume.
## 9.2. Interstitial water chemistry

Whole-round samples 5–20 cm in length were cut on the catwalk for IW extraction, immediately capped, and transferred to the chemistry laboratory for squeezing. IW samples were typically taken from the bottom of Section 2 (Expedition 395) or Section 4 (Expedition 395C). During Expedition 395, high-resolution IW sampling (bottom of Sections 1, 3, 4, 5, and 6) was conducted on 10 cm whole-round samples in the first core at each site (Holes U1564D, U1554G, and U1602B) for shipboard and shore-based measurements. Exposed surfaces of each whole-round sample were carefully scraped under ambient laboratory conditions using stainless steel knives to minimize contamination due to seawater, drilling disturbances, and/or sediment smearing along the insides of the core liners. When sampling sediment collected using the XCB or RCB systems, sediment for pore water extraction was carefully selected to avoid disturbed materials or infill. The selected sediment samples were transferred to titanium squeezers and put in a Carver hydraulic laboratory press where they were squeezed to extract IW at pressures up to 30,000 force pounds (~1.335 × 10⁶ N) (Manheim and Sayles, 1974). A minimum of 30 min of squeezing was required for all cores, and >12 h of squeezing was required to extract sufficient IW from deeper XCB or RCB cores. IW samples were first passed through a nanopure water-precleaned Whatman Number 1 filter above a titanium screen into a 60 mL high-density polyethylene (HDPE) syringe that had been acid-cleaned with 10% HCl. A 0.45 µm polyethersulfone membrane filter was attached to the syringe tip upon collection of IW from the squeezers. The collected fluids were then filtered through a 0.2 µm polyethersulfone membrane filter into appropriate containers and processed for shipboard and postcruise analyses. Following IW extraction, squeeze cake residues were sampled for shipboard analyses (e.g., TC, TS, and TIC). Total organic carbon (TOC) was determined by subtracting the TIC weight percent from the TC weight percent. The squeeze cake residues were

<table><caption>**Table T9.** Precision and detection limits for procedures used for IW, HS, and sediment geochemistry, Expeditions 384, 395, and 395C. * = calculated as 3× standard deviation of blank. † = based on replicate analyses of standards. RSD = SD/average. 100. ND = not determined, NA = not available. NGA-FID = natural gas analyzer with flame ionization detector, NGA-TCD = natural gas analyzer with thermal conductivity detector. Download table in CSV format.</caption><thead><tr><th>Instrument</th><th>Analyte</th><th>Unit</th><th>Limit of determination*</th><th>Precision (%)†</th><th>Standards</th></tr></thead><tbody><tr><td>Extec RE300 ExStik ORP Meter</td><td>eH</td><td>mV</td><td>ND</td><td>1.6</td><td>240 mV ORP Test Solution</td></tr><tr><td>Titrator</td><td>Alkalinity</td><td>mM</td><td>ND</td><td>2.0</td><td>100% IAPSO</td></tr><tr><td>Titrator</td><td>pH</td><td>None</td><td>NA</td><td>1.4</td><td>100% IAPSO</td></tr><tr><td>Ion chromatography</td><td>Na</td><td>mM</td><td>0.063</td><td>0.5</td><td>100% IAPSO</td></tr><tr><td>Ion chromatography</td><td>Cl<sup>-</sup></td><td>mM</td><td>0.0075</td><td>0.7</td><td>100% IAPSO</td></tr><tr><td>Ion chromatography</td><td>Br<sup>-</sup></td><td>mM</td><td>0.017</td><td>1.2</td><td>100% IAPSO</td></tr><tr><td>Ion chromatography</td><td>SO<sub>4</sub><sup>2-</sup></td><td>mM</td><td>0.027</td><td>0.7</td><td>100% IAPSO</td></tr><tr><td>Ion chromatography</td><td>K<sup>+</sup></td><td>mM</td><td>&lt;0.01</td><td>1.3</td><td>100% IAPSO</td></tr><tr><td>Ion chromatography</td><td>Ca<sup>2+</sup></td><td>mM</td><td>&lt;0.01</td><td>1.8</td><td>100% IAPSO</td></tr><tr><td>Ion chromatography</td><td>Mg<sup>2+</sup></td><td>mM</td><td>&lt;0.01</td><td>0.6</td><td>100% IAPSO</td></tr><tr><td>UV-Visible spectrophotometry</td><td>NH<sub>4</sub><sup>+</sup></td><td>µM</td><td>0.2</td><td>ND</td><td>NH<sub>4</sub>Cl</td></tr><tr><td>UV-Visible spectrophotometry</td><td>PO<sub>4</sub><sup>3-</sup></td><td>µM</td><td>0.5</td><td>ND</td><td>KH<sub>2</sub>PO<sub>4</sub></td></tr><tr><td>TECAN plate reader spectrophotometer</td><td>NH<sub>4</sub><sup>+</sup></td><td>µM</td><td>1.0</td><td>10</td><td>NH<sub>4</sub>Cl</td></tr><tr><td>TECAN plate reader spectrophotometer</td><td>PO<sub>4</sub><sup>3-</sup></td><td>µM</td><td>2.7</td><td>ND</td><td>KH<sub>2</sub>PO<sub>4</sub></td></tr><tr><td>Coulometry</td><td>TIC</td><td>wt%</td><td>NA</td><td>0.5</td><td>100% reagent grade CaCO<sub>3</sub></td></tr><tr><td>Coulometry</td><td>CaCO<sub>3</sub></td><td>wt%</td><td>NA</td><td>0.6</td><td>100% reagent grade CaCO<sub>3</sub></td></tr><tr><td>CHNS analyzer</td><td>C</td><td>wt%</td><td>ND</td><td>0.9</td><td>Buffalo River Sediment</td></tr><tr><td>CHNS analyzer</td><td>N</td><td>wt%</td><td>ND</td><td>8.6</td><td>Buffalo River Sediment</td></tr><tr><td>Coulometry/CHNS</td><td>TOC</td><td>wt%</td><td>NA</td><td>NA</td><td>NA</td></tr><tr><td>NGA-FID</td><td>Methane</td><td>ppmv</td><td>1</td><td>1.7</td><td>MESA Calibration Gas Mixture</td></tr><tr><td>NGA-FID</td><td>Ethane</td><td>ppmv</td><td>0</td><td>2</td><td>MESA Calibration Gas Mixture</td></tr><tr><td>NGA-FID</td><td>Ethane</td><td>ppmv</td><td>0</td><td>2.3</td><td>MESA Calibration Gas Mixture</td></tr><tr><td>NGA-FID</td><td>Propene</td><td>ppmv</td><td>0</td><td>2</td><td>MESA Calibration Gas Mixture</td></tr><tr><td>NGA-FID</td><td>Propane</td><td>ppmv</td><td>0</td><td>15</td><td>MESA Calibration Gas Mixture</td></tr><tr><td>NGA-FID</td><td>iso-butane</td><td>ppmv</td><td>0</td><td>11.7</td><td>MESA Calibration Gas Mixture</td></tr><tr><td>NGA-FID</td><td>n-butane</td><td>ppmv</td><td>0</td><td>3</td><td>MESA Calibration Gas Mixture</td></tr><tr><td>NGA-FID</td><td>iso-pentane</td><td>ppmv</td><td>0</td><td>7.4</td><td>MESA Calibration Gas Mixture</td></tr><tr><td>NGA-FID</td><td>n-pentane</td><td>ppmv</td><td>0</td><td>5.3</td><td>MESA Calibration Gas Mixture</td></tr><tr><td>NGA-FID</td><td>iso-hexane</td><td>ppmv</td><td>0</td><td>16</td><td>MESA Calibration Gas Mixture</td></tr><tr><td>NGA-FID</td><td>n-hexane</td><td>ppmv</td><td>0</td><td>10</td><td>MESA Calibration Gas Mixture</td></tr><tr><td>NGA-TCD</td><td>Nitrogen</td><td>ppmv</td><td>0</td><td>0.1</td><td>Laboratory air</td></tr><tr><td>NGA-TCD</td><td>Oxygen</td><td>ppmv</td><td>0</td><td>0.1</td><td>Laboratory air</td></tr></tbody></table>
also sampled for postcruise analyses and stored at 4°C. Squeezers were cleaned between samples
with tap water, rinsed with 18.2 MΩ deionized water, and dried with compressed air.

**9.2.1. Interstitial water analysis**

IW samples were analyzed on board following the protocols in Gieskes et al. (1991), Murray et al. (2000), and the IODP user manuals for shipboard instrumentation.

**9.2.1.1. Alkalinity, pH, Salinity, and Eh**

Alkalinity, pH, salinity, and Eh were measured immediately on IW extracted by squeezing, follow-
ing the procedures described in Gieskes et al. (1991). Salinity was measured with a Fisher Model
S66366 optical refractometer. International Association for the Physical Sciences of the Oceans
(IAPSO) standard seawater (salinity = 35) and 18.2 MΩ water (salinity = 0) were used to calibrate
salinity. IW pH and alkalinity were determined using a Metrohm 794 Basic Titrino Autotitrator
with a glass pH electrode. A 3 mL sample was titrated against 0.1 N HCl at 25°C to reach an end-
point of pH = 4.2. The IAPSO standard seawater (alkalinity = 2.325 mM; certified value) and labo-
ratory standards (5 to 100 mM Na₂CO₃ alkalinity, made by mixing different proportions of 0.7 M
KCl and 0.1 M Na₂CO₃) were used for calibration. The IAPSO standard was analyzed at the begin-
ning and end of the sequence and after every 10 samples. Repeated measurements of IAPSO sea-
water for alkalinity yielded precision better than 2.5%. Eh was measured on an Extec RE300 ExStik
ORP Meter (Cole-Parmer) on 2 mL of IW under ambient conditions. Calibration of Eh measure-
ments were made with repeat measurements of 18.2 MΩ water (Eh = 0 mV) and Hanna Instru-
ments H1702L ORP standard solution (Eh = 240 mV) (Table T9).

**9.2.1.2. Ion chromatography**

Sulfate (SO₄²⁻), chloride (Cl⁻), bromide (Br⁻), sodium (Na⁺), magnesium (Mg²⁺), potassium (K⁺), and calcium (Ca²⁺) concentrations were analyzed using ion chromatography (Metrohm 850 Professional IC) using 100 µL of squeezed IW diluted by 100 times with 18.2 MΩ water. For anions (Cl⁻, SO₄²⁻, and Br⁻), a Metrosep C6 column (100 mm long; 4 mm inner diameter) was used with 3.2 mM Na₂CO₃ and 1.0 mM NaHCO₃ solutions as eluents, whereas a Metrosep A Supp 7 column (150 mm long; 4 mm inner diameter) was used with 1.7 mM of HNO₃ and pyridine-2,6-dicarboxylic acid (PDCA) solutions as eluents for cations (Na⁺, K⁺, Mg²⁺, and Ca²⁺). The standards used were IAPSO in various dilutions (ranging 1%–150% IAPSO) to create a nine-point calibration curve. Reproducibility was checked on the repeated measurements of standard IAPSO and IAPSO dilution of 1:10 every 10 samples. Reproducibility (defined by standard deviation/average and relative standard deviation [RSD]) of repeated IAPSO measurements) of IAPSO measurements (n = 40) was ≤1.8% for Cl⁻, SO₄²⁻, Na⁺, Mg²⁺, K⁺, Br⁻, and Ca²⁺ (Table T9).

**9.2.1.3. Spectrophotometry of ammonium and phosphate**

Aliquots of IW samples were diluted with 18 MΩ millipore water for analysis of ammonium (NH₄⁺) and phosphate (PO₄³⁻) using an Agilent Cary 100 UV-Vis spectrophotometer. Ammonium concentrations were determined using a colorimetric by phenol diazotization and subsequent oxidation by sodium hypochlorite to yield a blue color measured spectrophotometrically at a wavelength of 640 nm. Ammonium chloride (NH₄Cl) was used for calibration and standardization. Phosphate concentrations were measured through the reaction of orthophosphate with Mo (VI) and Sb (III) in an acidic solution, which formed an antimony-phosphomolybdate complex and was then reduced by ascorbic acid to form a blue color. After adding the mixed reagent solution and letting the samples react for 30 min, the absorbance was measured at 885 nm (Gieskes et al., 1991). Table T9 lists precision and detection limits for ammonium and phosphate standards.

**9.2.1.4. Inductively coupled plasma–optical emission spectroscopy**

Selected major and minor elements (Na, Ca, Mg, K, Li, B, P, Si, Ba, Fe, Mn, and Sr) were analyzed using the shipboard Agilent 5110 with an Agilent SPS4 autosampler inductively coupled plasma-optical emission spectroscope (ICP-OES) in atomic emission spectroscopy (AES) mode and is referred to as ICP-AES in this volume and in the LIMS/LORE database. Shipboard ICP-AES analyses for IW were modified from ODP Technical Note 29 (Murray et al., 2000) with updates related to the specifications of the current Agilent ICP-AES instrument. Internal standards were used to correct for instrument performance variations across the spectral range of the elements of interest. A 500 µL aliquot of each IW sample was diluted to 5 mL with 100 µL of an internal standard
solution containing 100 ppm Be, In, and Sc; 200 ppm Sb; and 4.4 mL of 2% HNO₃. Each batch of samples analyzed on the ICP-AES included blanks and reference samples of known concentrations. Each sample was analyzed three times in a sample run. Following each instrument run, the measured raw intensity values were automatically corrected for instrument drift and blank values, and calibration curves were calculated using Agilent's ICP Expert software (Version 7.3.0.1.9507).

Calibration curves for major cations (Na⁺, K⁺, Mg²⁺, and Ca²⁺) were established using a series of dilutions of IAPSO standard seawater (from 1:1 to 1:100 IAPSO:2% HNO₃). Standards for minor and trace element analyses (K, Li, B, Si, Ba, Fe, Mn, and Sr) were made from a stock multielement solution prepared from ultrapure primary standards (1000 ppm; SPEX CertiPrep reference standards) in 2% HNO₃ with 35 ppt NaCl. This stock solution was diluted using 2% HNO₃ + NaCl to produce a set of standards ranging 1%–100% of the stock solution elemental abundances. For consistency, calibration standards were diluted for ICP-AES measurement in the same way as the samples, which were run at a 10:1 dilution factor. The 1:1 standard was repeatedly analyzed with each batch of samples during the expedition. The ICP-AES plasma was ignited at least 30 min before the sample run to allow the instrument to stabilize. Each sample was analyzed three times from the same solution. For each run, the wavelengths with calibration curves showing the highest correlation coefficient (r value) for each element were used to determine concentrations. At the beginning of each ICP-AES batch run, a complete set of in-house and IAPSO standard dilutions were analyzed. Furthermore, known solutions of the IAPSO standard were run every six to eight samples to monitor instrument drift and accuracy. The elemental concentrations reported for each sample were average values from three replicate integrations for each sample. Reproducibility was typically better than 5% for all elements and mostly around 1%–3% (Table T10).

## 9.3. Oxygen measurements

During Expedition 395, dissolved oxygen concentrations were measured in sediments from Holes U1554G, U1562C, U1564D, U1564F, and U1602B to determine pore water dissolved oxygen profiles at each site. No dissolved oxygen measurements were made during Expeditions 384 and 395C. Oxygen concentrations were measured using a FireSting-O₂ optical meter following manufacturer instructions (Pyroscience sensor technology, Germany). O₂ sensors were calibrated daily using a two-point calibration with air-saturated deionized water (100% oxygen saturation) and an OXCAL O₂ calibration capsule (Pyroscience) solution (0% oxygen saturation). Oxygen measurements were determined using whole-core sections prior to splitting. A ~3 mm diameter hole was drilled in the core liner using a hand drill, and the oxygen microsensor was inserted manually ~2.5 cm into sediments at the desired measurement locations. The microsensor was placed 25–30 cm beneath the top of Section 2 for each core, the temperature sensor was placed 10 cm above the microsensor (~15–20 cm beneath the top of the section), and the signal was allowed to equilibrate to a steady value (~1 min on average, but sometimes up to 5 min). All calibration and measurement data were processed using the FireSting Logger Software (Version 2.365). After arriving on

<table><caption>**Table T10.** Shipboard ICP-AES method precision and detection limits for elements analyzed in interstitial waters, with the specific spectral lines used for each element, Expedition 395. * = calculated as 3× standard deviation of the IAPSO blank. † = based on replicate analyses of 100% IAPSO and 100% in house standards. **Download table in CSV format.**</caption><thead><tr><th>Element (units)</th><th>Wavelength (nm)</th><th>Detection limit*</th><th>Precision (%)†</th></tr></thead><tbody><tr><td>B (µM)</td><td>249.772</td><td>1.6</td><td>0.5</td></tr><tr><td>Ba (µM)</td><td>455.403</td><td>0.012</td><td>0.7</td></tr><tr><td>Ca (mM)</td><td>313.933</td><td>&lt;0.001</td><td>0.6</td></tr><tr><td>Fe (µM)</td><td>238.204</td><td>0.24</td><td>0.8</td></tr><tr><td>K (mM)</td><td>766.491</td><td>&lt;0.01</td><td>0.6</td></tr><tr><td>Li (µM)</td><td>670.783</td><td>0.4</td><td>0.6</td></tr><tr><td>Mg (mM)</td><td>277.983</td><td>0.012</td><td>0.5</td></tr><tr><td>Mn (µM)</td><td>257.61</td><td>0.044</td><td>0.3</td></tr><tr><td>Na (mM)</td><td>330.298</td><td>0.13</td><td>0.5</td></tr><tr><td>P (µM)</td><td>178.222</td><td>6.4</td><td>1.5</td></tr><tr><td>S (mM)</td><td>180.669</td><td>&lt;0.001</td><td>0.2</td></tr><tr><td>Si (µM)</td><td>288.158</td><td>0.96</td><td>0.3</td></tr><tr><td>Sr (µM)</td><td>421.552</td><td>0.005</td><td>0.6</td></tr></tbody></table>