<figure><img src="image_398.png" /><figcaption>Figure F6. A. Lithostratigraphic summary of Hole U1504A with simplified lithology and unit descriptions. B. Lithostratigraphic summary of Hole U1504B with simplified lithology and unit descriptions. (Continued on next page.)</figcaption></figure>

Subunit IC is 39.19 m thick and composed of light greenish gray, greenish gray, light brownish gray, pale brown, and light gray nannofossil ooze with clay and greenish gray clay-rich nannofossil ooze (Figures F7, F9). These lithologies are intercalated with light gray nannofossil-rich foraminiferal ooze with clay, light brownish

gray foraminifer-rich nannofossil ooze, and foraminifer-rich nannofossil ooze with clay. The sediment color is more brownish downhole in the subunit. The sediment is well sorted and slightly consolidated. The average grain size is clay, and very fine sand is the maximum grain size.
<figure><img src="image_399.png" /><figcaption>Figure F6 (continued).</figcaption></figure>

Contacts between layers are normally planar and subhorizontal. The bioturbation in Subunit IC sediment is heavy. There are foraminifer-filled burrows, especially in the middle to upper portion of the subunit.

The boundary between Subunits IC and ID is characterized by a change in color from grayish to more brownish in Subunit ID (Figure F7).

## Subunit ID

Intervals: 368-U1504A-12R-1, 19 cm, to 12R-CC, 18 cm; 368-U1504B-2R-1, 0 cm, to 2R-CC, 17 cm

Depths: Hole U1504A = 104.99-112.66 m; Hole U1504B = 88.20-92.31 m

Age: early Miocene
Figure F7. Representative images of core sections from Unit I. Subunit IA (4R-3) includes dark greenish gray nannofossil-rich ooze with biogenic silica (0-70 cm) and nannofossil-rich clay (70-139 cm). Subunit IB (6R-2) consists of pale and light brown nannofossil ooze with varying amounts of foraminifers. Subunit IC (8R-3 and 10R-3) is composed of greenish gray and pale brown nannofossil ooze with clay. Subunit ID (12R-3) contains light brown nannofossil ooze with foraminifers.

<figure><img src="image_400.png" /><figcaption>Table T2. Mineral percentages, Site U1504. View table in PDF format. Download table in CSV format.</figcaption></figure>

Subunit ID is composed of light brown to yellowish brown nannofossil ooze with foraminifers intercalated with pink, pinkish gray, or brownish yellow foraminifer-rich nannofossil ooze (Figures F7, F9, F10). The nannofossil ooze is moderately consolidated and well sorted, with silt as the maximum grain size. Contacts are horizontal and planar. Millimeter-sized pyrite patches (burrows?) are developed on the core surface (Figure F10). There are two large (1-4 cm) pyrite nodules in Section 368-U1504A-12R-5. Pyritized burrows are found in Section 368-U1504B-2R-1.

Bioturbation is high throughout the subunit. The large circular to oval patches 1–4 cm in diameter in the lower portion of Subunit ID are identified as burrows.

The Subunit ID lithology is different from that of the underlying Unit II. The contact with Unit II was not cored due to low core recovery across this boundary.

## Unit II

Intervals: 368-U1504A-13R-CC, 0 cm, to 15R-1, 64 cm; 368-U1504B-3R-1, 0 cm, to 4R-1, 31 cm

Depths: Hole U1504A = 114.72–134.80 m; Hole U1504B = 97.90–107.91 m

Age: Eocene?

## Lithology and sedimentary structures

In Hole U1504A, Unit II is 20.08 m thick, but only 1.04 m of sediment was recovered. The upper part of Unit II in Hole U1504A is composed of pink bioclast-rich limestone with clasts of sedimentary and metamorphic origin (interval 368-U1504A-13R-CC, 0 cm, to 14R-1, 12 cm). The lower part is light brownish gray clast-supported limestone with large benthic foraminifers and common epi-dote grains (Figures F11, F12). The clast-supported limestone is overall poorly sorted and dominated by coarse sand but also contains pebble-sized sedimentary and metamorphic clasts. Shell fragments (bivalves) and large benthic foraminifers (as large as 15 mm) are the main biogenic components. The benthic foraminifers were identified as predominantly *Nummulites* and *Assilina* species that give a possible Eocene or slightly younger age for this unit. Some clasts have Fe-Mn coatings (Figure F11).

In Hole U1504B, only 47 cm of white and pink limestone was recovered. The limestone is mainly composed of coral fragments, shell fragments, and coated grains. The rock has high porosity and little matrix.

The contact between Units II and III was not recovered.

## Bulk mineralogy and chemistry

Compositional analyses of Unit II carbonates were made directly on the archive half of the core using the handheld pXRF (see *Igneous and metamorphic petrology* in the Expedition 367/368 methods chapter [Sun et al., 2018]) (Table T3). Four representative samples from Unit II and one black-coated clast were analyzed. The limestone has high CaO contents (38–48 wt%), SiO₂ contents of 6–19 wt%, and minor Fe₂O₃ (up to 7 wt%) and MgO (up to 4 wt%) abundances. Sr abundance varies between 183 and 402 ppm, and S abundance varies broadly from 148 to 11632 ppm. The analyses of the black-coated clast support the interpretation of an Fe-Mn coating with high Fe₂O₃ (~15 wt%) and MnO (~18 wt%) contents. The coating is enriched in trace elements like Ni (1604 ppm), V (1009 ppm), Cu (757 ppm), Sr (1111 ppm), Mo (491 ppm), and Pb (1103 ppm).
<figure><img src="image_401.png" /><figcaption>Figure F8. Bulk XRD mineralogy analysis data, Site U1504.</figcaption></figure>

The bulk mineralogy results of XRD analyses are listed in Table T2. One XRD sample from Unit II indicates that the bulk mineralogy of the limestone is calcite (64%) and plagioclase (22%), with minor amounts of quartz, K-feldspar, and chlorite (Figure F8).

## Unit III

Intervals: 368-U1504A-16R-1, 0 cm, to 21R-1, 40 cm; 368-U1504B-5R-1, 0 cm, to 20R-1, 98 cm

Depths: Hole U1504A = 136.40–163.70 m; Hole U1504B = 117.40–196.28 m

Age: unknown (older than Eocene?)

Unit III is 27.30 m thick in Hole U1504A and 78.69 m thick in Hole U1504B. The unit is divided into two subunits, IIIA and IIIB. Subunit IIIA is composed of greenish gray epidote-chlorite schist (with granofels clasts) and epidote-chlorite breccia, and Subunit IIIB is composed of calc-silicate schist (with granofels clasts), epidote-chlorite schist (with granofels clasts), and marble (see **Igneous and metamorphic petrology**). The schist contains angular, heavily veined granofels clasts. Brittle and ductile deformation structures were observed.

The fine- to coarse-grained rocks are fragmented due to drilling disturbance.

A more detailed macroscopic and microscopic description and interpretation of this unit is provided in **Igneous and metamorphic petrology**.

# Discussion

## Depositional environment of Unit I

Lithostratigraphic Unit I at Site U1504 was deposited in a deep-marine environment. The dominant lithology is nannofossil ooze

with variable amounts of clay and foraminifers and minor foraminiferal ooze. The top subunit, IA, contains siliceous microfossils, including diatoms, radiolarians, and sponge spicules, except in the lowermost meter below a prominent, steeply inclined silty interval (368-U1504A-5R-1, 100 cm). Lithologic changes between subunits likely reflect variations in the amount of terrigenous input into a relatively open ocean setting, as well as changes in climate and oceanographic conditions. The terrigenous input may be delivered as buoyant plumes from shallower shelf environments. There is little change in the composition of the terrigenous grains, suggesting a common source area throughout Unit I. Thin laminae of silt are found rarely throughout Subunit IA. Some are graded, and all have sharp bases; however, many are disrupted by bioturbation and interpreted as distal turbidites.

Soft-sediment deformation in Subunits IA and IB, including inclined bedding and irregular sediment color boundaries, indicates slumping downslope of parts of the sequence. Bedding below this interval is consistently horizontal, indicating the deformation was synsedimentary.

## Depositional environment of Unit II

The dominant lithologies in Unit II are bioclastic-rich limestone and clast-supported limestone with large benthic foraminifers. The major skeletal clasts include coarse sand- to pebble-sized corals, large benthic foraminifers (e.g., *Nummulites* and *Assilina*), bivalves, and epidote (Figure F11). *Nummulites* are tropical, shallow-water foraminifers (Beavington-Penney and Racey, 2004). The combination of poorly sorted, subangular, sand- to pebble-sized bioclasts, metamorphic and sedimentary rocks, coral fragments, and large benthic foraminifers suggests deposition in a shallow marine environment. The lithic clasts were most likely derived from adjacent
<figure><img src="image_402.png" /><figcaption>Figure F9. A. Dark greenish gray nannofossil-rich ooze, Subunit IA. B. Greenish gray nannofossil ooze with foraminifers (red) (Subunit IA; 0–9 cm) and pale brown nannofossil ooze with foraminifers (green) (Subunit IB; 9–145 cm). C. Light brownish gray nannofossil ooze with clay (Subunit IC). D. Light brown nannofossil ooze with foraminifers (Subunit ID).</figcaption></figure>

parts of the basement high. The Fe-Mn coating on some of the met-
amorphic and sedimentary clasts suggests there was a hiatus or re-
duction in the depositional rate following accumulation of the Unit
II sediment. Manganese nodules were also recovered in the Mio-

cene sequence of nearby IODP Site U1435 (Li et al., 2015). Manga-
nese deposits form in sediment-starved settings (Cronan, 1980),
which is consistent with the very low sedimentation rates (~0.5
cm/ky) at both Sites U1504 (see **Biostratigraphy**) and U1435.
Figure F10. Subunit ID. A. Brownish yellow layer with foraminifer-rich nannofossil ooze. B, C. Smear slide images of brownish yellow layer showing foraminifers and discoasters. D. Black pyrite nodule in yellowish brown foraminifer-rich nannofossil ooze. E. Smear slide image of pyrite nodule.

<figure><img src="image_403.png" /></figure>

## Preliminary correlation between Unit I subunits, Sites U1501 and U1504

Sites U1501 and U1504 are located 50.28 km apart on the OMH. Today's water depths are very similar at Sites U1501 and U1504 (2857 and 2816 m, respectively). The recovered Pleistocene to early Miocene/Oligocene sediment successions can be correlated based on their major lithologies and the age of deposition. We suggest a correlation between Pleistocene Subunit IA (Site U1504) and Pleistocene to Pliocene Subunits IA and IB (Site U1501), which are both dominated by dark greenish gray nannofossil-rich clay and clay-rich nannofossil ooze with siliceous microfossils. At Site U1504, a hiatus is apparent below Subunit IA (see Biostratigraphy). Middle Miocene Subunit IB (Site U1504) correlates well with late to middle Miocene Subunit IC (Site U1501). These subunits are both com-

Figure F11. Unit II. A. Bioclast-rich and clast-supported limestone. Lithic clasts of metamorphic schist (13–24 cm). B. Lithic clasts with iron manganese coatings. C. Clast-supported limestone. D. Large benthic foraminifer in clast-supported limestone.

<figure><img src="image_404.png" /></figure>

posed of greenish gray and light brownish gray nannofossil ooze with clay-rich and foraminifer-rich intervals. Middle Miocene Subunit IC (Site U1504) can be correlated to middle Miocene to Oligocene Subunits ID and IE (Site U1501). These subunits are characterized by greenish gray and gray nannofossil ooze with clay.
Figure F12. Limestone in Unit II (U1504A-15R-1, 21–23 cm [TS 55]). A, C, D. Large benthic foraminifers *Nummulites* (Num) and *Assilina* (Assi) and epidote (Ep) grains. B. Overview image. A: cross-polarized light (XPL); C, D: plane-polarized light (PPL).

<figure><img src="image_405.png" /><figcaption>Table T3. Major element oxides and minor elements in rocks, Site U1504.
**View table in PDF format. Download table in CSV format.**</figcaption></figure>

# Igneous and metamorphic petrology
## Metamorphic lithologic Unit 1

Intervals: 368-U1504A-16R-1, 0 cm, to 21R-1, 45 cm; 368-U1504B-5R-1, 0 cm, to 20R-1, 98 cm

Depths: Hole U1504A = 136.40–163.75 m; Hole U1504B = 117.40–196.28 m

Thickness: Hole U1504A = 27.35 m; Hole U1504B = 78.88 m

Lithology: epidote-chlorite schist with granofels clasts, epidote-chlorite breccia, calc-silicate schist with granofels clasts, chlorite granofels, epidote granofels, epidote-chlorite granofels, chlorite schist with epidote, epidote-chlorite gneiss clasts, and marble

Recovery: Hole U1504A = 19%; Hole U1504B = 21%

Age: unknown, older than late Eocene

Metamorphic lithologic Unit 1 (lithostratigraphic Unit III) (Figure F13) consists of a variety of metamorphic schistose rocks and granofels clasts. The clasts have variable lithologies but are generally termed granofels due to the lack of foliation. Weak foliation was observed locally in some clasts, but for the sake of simplicity and to mark the contrast with the schist, they were grouped with the unfoliated rocks and we applied the term granofels to those rocks as well. Lithologic changes were encountered with depth and also between the two holes (U1504A and U1504B). Recovery of Unit 1 was poor in both holes (averaging 18.5% and 21%, respectively), with only a limited number of coherent cores. Many of the recovered pieces are small and rounded and do not preserve their original orientation. Metamorphic lithologic Unit 1 is divided into two subunits based on a change in the metamorphic lithology. Subunit 1a was recovered in both Holes U1504A and U1504B and consists of epidote-

chlorite schist with granofels clasts and epidote-chlorite breccia. Subunit 1b is defined from interval 368-U1504B-10R-1, 22 cm, through Core 20R and consists of an alternation of calc-silicate schist and epidote-chlorite schist with granofels clasts, epidote and/or chlorite granofels, chlorite schist with epidote, epidote-chlorite gneiss, and minor marble.

## Metamorphic lithologic Subunit 1a

Intervals: 368-U1504A-16R-1, 0 cm, to 21R-1, 45 cm; 368-U1504B-5R-1, 0 cm, to 10R-1, 22 cm

Depths: Hole U1504A = 136.40–163.75 m; Hole U1504B = 117.40–141.72 m

Lithology: epidote-chlorite schist with granofels clasts and epidote-chlorite breccia

### Hole U1504A

Subunit 1a in Hole U1504A is composed of strongly deformed greenish gray, fine- to medium-grained epidote-chlorite schist with granofels clasts (Figure F14A). This unit is generally characterized by a mylonitic foliation with a wide geometrical and textural spectrum that is further described in Structural geology. Throughout Cores 16R–21R, the macroscopic mineral assemblage is made up of quartz, epidote, chlorite, and microcrystalline plagioclase (albite?).

The schist contains about 10% angular to rounded granofels clasts as large as 6 cm. These clasts are composed of dark greenish gray fine-grained minerals crosscut by abundant quartz veins that show reddish alteration in a few cases (Figure F14B). Minor horizons possibly representing clasts and/or veins have a coarse-grained (0.5–1 cm), patchy texture of epidote, quartz, and most likely chlorite (Figure F14C). Several intervals in Core 17R have small cavities likely resulting from dissolution (Figure F14D).

### Hole U1504B

Subunit 1a lithologies in Hole U1504B are generally similar to those in Hole U1504A and characterized by a greenish gray, microcrystalline to coarse-grained epidote-chlorite schist that contains dark greenish gray microcrystalline granofels clasts. The schist and granofels clasts have a comparable mineral assemblage that consists of epidote, chlorite, quartz, and potentially plagioclase ± other phyllosilicates and accessory minerals. Quartz does not usually form part of the original metamorphic assemblage of the granofels clasts but cuts them as veins. The steep (>50°) mylonitic foliation recorded in Hole U1504A was also observed in Hole U1504B, and the intensity of the deformation varies from moderate to strong (see Structural geology). However, Hole U1504B differs from Hole U1504A in several aspects. Isolated subhedral dark minerals can be observed locally within the epidote-chlorite schist (e.g., interval 5R-1, 117–124 cm; Figure F15B). Core 5R recovered epidote-chlorite breccia (Figure F15A) that is clast- to matrix-supported with angular, decimeter-sized clasts made of mainly quartz-veined granofels, although other lithologic varieties were also observed. The granofels clasts in the epidote-chlorite schist seem heterolithic. Notably, granofels clasts are more abundant in Hole U1504B; this finding is emphasized by the recovery of pieces (usually <10 cm) completely made up of such epidote-chlorite granofels clasts. These clasts have generally isotropic textures with only a weakly developed foliation and are either strongly veined as in Hole U1504A or devoid of macroscopic veining. Downhole, some clasts reveal more quartz or calcite veins and/or reddish alteration features (Cores 7R–9R).
<figure><img src="image_406.png" /><figcaption>Figure F13. Lithostratigraphic summary of metamorphic lithologic Unit 1 rocks showing recovered lithologies and their metamorphic division into Subunits 1a and 1b, Holes U1504A and U1504B.</figcaption></figure>

Microscopic observations

In thin sections, discontinuous, elongated, fine-grained (<100 µm), leucocratic aggregates and bands alternate with very fine grained assemblages of chlorite, epidote, phyllosilicates, and other finer grained minerals, together defining the foliation (Figure F16A,

F16B). In detail, the leucocratic bands contain feldspar (plagioclase) and quartz with sparse, very fine grained epidote and other fine-grained minerals such as chlorite. The thickness of the leucocratic and chlorite bands is highly variable in individual samples, resulting in either a more felsic or a mafic overall appearance. Within these
Figure F14. Textural diversity in epidote-chlorite schists in Subunit 1a, Hole U1504A. A. Typical medium-grained epidote-chlorite schist. B. Severely quartz-veined angular clast of chlorite-epidote granofels within the schist matrix. C. Domain (clast or vein) formed by patchy epidote and quartz in a chlorite-rich matrix. D. Strongly foliated variety of the schist with abundant small cavities, likely resulting from dissolution.

<figure><img src="image_407.png" /></figure>

bands, coarser grained euhedral epidote as large as 0.3 mm is also abundant, recrystallizing locally into fine-grained mineral aggregates (Figure F16B).

The fine-grained veined clasts within the schist consist of microcrystalline chlorite and epidote with no relics or indicators of a protolithic mineral assemblage and are accordingly termed chlorite-epidote granofels (Figure F16C). Dynamically recrystallized quartz veins crosscut the granofels clasts (see Structural geology for detailed microstructural observations).

In Sections 368-U1504B-5R-1 and 5R-2, dark euhedral-subhedral minerals have characteristics that are consistent with clino-and possibly orthopyroxenes (Figure F17). Clinopyroxenes may be replaced by chlorite (possibly mixed with serpentine) or crosscut by calcite veins.

## Metamorphic Subunit 1b

Interval: 368-U1504B-10R-1, 22 cm, to 20R-1, 98 cm

Depth: 141.72–196.28 m

Lithology: calc-silicate schist and epidote-chlorite schist with granofels clasts, epidote and/or chlorite granofels, epidote-chlorite gneiss, chlorite schist with epidote, marble

Subunit 1b is only found in Hole U1504B and is marked at interval 10R-1, 22 cm, by the appearance of calc-silicate schists with granofels clasts (Figure F15D) that alternate with the lithologies found in Subunit 1a. Two distinctive intervals were observed: (1) in interval 11R-1, 22–58 cm, an impure foliated marble with reddish brown minerals and minor epidote was identified within the schists (Figure F15C), and (2) in interval 17R-1, 38–92 cm, a locally foliated chlorite schist with epidote was recovered, but it is unclear whether this interval represents a clast (Figure F15E).

Figure F15. Lithologies in Subunits 1a and 1b, Hole U1504B. (A) Coarse-grained and (B) fine-grained variety of mafic granofels breccias. C. Foliated impure calcite marble. D. Typical calc-silicate schist with granofels clasts. Granofels clasts are mafic in nature, being highly phyric, possibly vesicular, and strongly altered. E. Deformed chlorite schist interpreted as a large "granofels" clast.

<figure><img src="image_408.png" /></figure>

The calc-silicate and epidote-chlorite schists are fine to coarse grained with a mostly inequigranular texture. The schistose sections reveal strong mylonitic foliation (see Structural geology). The calc-silicate schists are characterized by the assemblage of epidote, quartz, chlorite, carbonate (e.g., calcite), and plagioclase (possibly albite). Several of the schists show reddish-brown alteration. Late quartz-calcite veins crosscut the foliation of some schists (e.g., in Core 20R).

Subunit 1b is characterized by strong lithologic, grain size, and textural diversity of the clasts embedded in the schist. The clasts are (1) microcrystalline to medium-grained epidote-chlorite granofels like those found in Subunit 1a, either with or without quartz and/or calcite veins (e.g., Figures F14B, F18); (2) porphyritic "granofels" with unknown tabular euhedral to subhedral phenocrysts (possibly altered plagioclase) and in some cases probable vesicles; (3) deformed (epidote, calcite and/or quartz) veins; and (4) epidote-chlorite gneiss. Most of these clasts are locally deformed and foliated according to the mylonitic deformation observed in the surrounding schist and show diffuse boundaries between the clasts and the surrounding schists.

## Microscopic observations

Subunit 1b thin sections reveal the same metamorphic mineralogy as those of Subunit 1a and are dominated by feldspar-quartz, epidote, chlorite, calcite and phyllosilicate, and minor zeolites, ox-
Figure F16. Greenschist facies mineral assemblage and structural relationships of different minerals in epidote-chlorite schist, Subunit 1a. A. Alternating bands dominated by quartz and fine-grained chlorite + epidote, defining the foliation. B. Band dominated by chlorite and coarse-grained subhedral epidote. C. Clast of chlorite-epidote granofels with quartz veins.

<figure><img src="image_409.png" /></figure>

ides, and hydroxides (Figure F17). Based on three thin sections from Cores 368-U1504B-13R, 17R, and 19R, the amount of calcite is variable and may decrease downhole. Bands of phyllosilicate that alternate with commonly elongated and occasionally deformed lens-like aggregates and quartz-rich bands principally define the foliation. The aggregates can also consist of chlorite and some epidote ("epidosite"). Chlorite also occurs in bands and can have an intense brownish-yellow color. In some instances, chlorite (together with zeolite) has completely replaced mafic minerals. The origin of the aggregates or clasts is uncertain, although they seem to be heterolithic and may include various types of mafic igneous rock fragments (phyric or aphyric basalts? dike fragments?) and individual phenocrysts (potentially plagioclase). Epidote is disseminated throughout the matrix and often concentrated in veins, including those that dissect and disaggregate the leucocratic accumulations. The fine-grained chlorite schist with epidote in Core 19R has the same mineralogy and differs principally by its microcrystalline,

Figure F17. Greenschist facies mineral assemblage and textural variety in epidote-chlorite and calc-silicate schist in Subunits 1a and 1b, Hole U1504B. A. Epidote-chlorite schist with clinopyroxene crystal dissected by chlorite veins embedded in a matrix of quartz, albite, chlorite, and disseminated epidote. B. Calc-silicate schist with angular (upper half) and sigmoidally deformed (lower half) granofels clasts embedded in a poorly foliated matrix of quartz/albite, phyllosilicates, and epidote. Upper clast is cut by calcite-quartz vein. C. Microcrystalline chlorite schist with weaker foliation and rare large epidote grains.

<figure><img src="image_410.png" /></figure>

largely homogeneous texture and the weaker foliation due to the sparseness of phyllosilicate bands, lending a leucocratic appearance.

## Bulk mineralogy

XRD analyses of four metamorphic samples from different lithologies within metamorphic lithologic Unit 1 indicate that the bulk mineralogy is predominantly characterized by plagioclase (albite?) ± epidote ± chlorite ± quartz (Table T4). A Subunit 1a chlorite-epidote schist sample (368-U1504A-17R-2, 17–19 cm) contains plagioclase and chlorite. A Subunit 1b brown calc-silicate schist sample (368-U1504B-12R-2, 50–51 cm) contains plagioclase + calcite + epidote with trace amounts of chlorite and a clay mineral (illite-montmorillonite, smectite?). A gray granofels clast sample (368-U1504A-20R-1, 8–11 cm) contains plagioclase + epidote + dolomite
Figure F18. Granofels clasts enclosed in calc-silicate schists and epidote-chlorite schists in Subunit 1b, Hole U1504B. A. Veined and altered aphyric mafic granofels clast (left) and granofels clast interpreted as protolithic epidote vein (right). Both clasts are internally undeformed but show synkinematic deformation together with a mylonitic fabric at their rims. B. Highly phyric granofels clast, most likely of igneous origin, showing euhedral, probably replaced crystals and deformed epidote-calcite vein. C. Strongly deformed epidote chlorite gneiss interpreted as deformed "granofels" clast. D. Highly phyric igneous granofels clast with subhedral, probably replaced crystals. E. Slightly deformed phyric igneous granofels clast. F. Protolithic predominantly epidote vein forming a granofels clast.

<figure><img src="image_411.png" /></figure>

with trace amounts of chlorite. A crystal-rich granofels clast sample (368-U1504B-13R-1, 6-7 cm) contains plagioclase + chlorite with trace amounts of epidote, a clay mineral (illite-montmorillonite?), and mica.

## Chemical composition

The handheld pXRF was used to determine the compositional characteristics of the diverse clast and schist lithologies seen in the metamorphic rocks of Unit 1 in Holes U1504A and U1504B. Analyses were made directly on the archive half of the core (see **Igneous and metamorphic petrology** in the Expedition 367/368 methods chapter [Sun et al., 2018]). A total of 149 representative samples from metamorphic lithologic Unit 1 and two metamorphic clasts from lithostratigraphic Unit II were analyzed (Figure F19; Table T5). The average pXRF sample spacing was ~20 cm within the recovered core material. Unit 1 rocks have a broadly mafic composition with the following contents: SiO₂ = 50 ± 3 wt%, MgO = 7 ± 3 wt%, Fe₂O₃ = 11 ± 4 wt%, Al₂O₃ = 16 ± 3 wt%, TiO₂ = 1.9 ± 0.7 wt%,

<caption>Table T4. Mineral percentages, Site U1504. **View table in PDF format. Download table in CSV format.**</caption>

and CaO = 9 ± 3 wt%. In detail, the Subunit 1a rocks in Hole U1504B tend to have lower Al₂O₃ and higher MgO, MnO, and Fe₂O₃ contents compared to those in Hole U1504A (Figure F19A). Furthermore, the schist matrix of Subunit 1a rocks in Hole U1504B, in general, has high S contents (mean = 0.6 wt%; range from below detection limit to almost 3 wt%) compared to the Subunit 1a schists in Hole U1504A (S = <0.25 wt%). In contrast, S is at or below the detection limit (<0.02 wt%) in all Subunit 1b samples.

Within Hole U1504B, the schist matrix of the Subunit 1b rocks has lower MgO (5.5 ± 1.1 wt%) and Ni (20 ± 6 ppm) compared to the schist matrix of the overlying Subunit 1a rocks (MgO = 9.7 ± 2.1 wt%; Ni = 78 ± 40 ppm) (Figure F19C). In detail, Subunit 1b schists show a negative correlation between MgO and CaO (Figure F19B), with the brown foliated calc-silicate schists generally having higher CaO and lower MgO. Subunit 1b rocks are also typically more enriched in Zr relative to Ti (Figure F19D), which is seen in their lower Ti/Zr ratios (56 ± 22) compared to Subunit 1a rocks (85 ± 10).

The textural and mineralogical diversity of clasts within the schist is reflected in their chemical compositions (Figure F19). One lithologically distinctive group of clasts is the coarse-grained brown, dark-green, and yellow green clasts seen, for example, in intervals 368-U1504B-12R-2, 24-28 cm, and 15R-1, 116-122 cm (Figure F18A, F18F). These clasts are also compositionally distinct and have high Zr (390-1000 ppm), low TiO₂ (0.4-0.8 wt%), and low MgO (2-3 wt%) (Figure F19). Fine-grained gray granofels clasts ± white veins are common throughout Unit 1 (Figures F14B, F15A, F15D) and in general have compositional features similar to the surrounding schist material (Figure F19). In detail, there are some compositional differences between the granofels clasts in the different subunits and holes. The granofels clasts in Subunit 1a rocks in Hole U1504B have higher MgO and lower Al₂O₃ contents compared to those in Subunit 1a and 1b rocks in Holes U1504A and U1504B (Figure F19A). The Subunit 1b clasts in Hole U1504B have similar MgO concentrations to the Subunit 1a clasts in Hole U1504A, but they typically show higher MnO contents. A few of the Subunit 1a veined clasts in Hole U1504A have elevated Zr concentrations (as high as 500 ppm) relative to TiO₂ (Figure F19D).

## Interpretation

Metamorphic lithologic Unit 1 consists of mylonitic, greenschist facies metamorphic rocks, as indicated by the presence of epidote and chlorite. The present mineral assemblage consists of epidote + chlorite + feldspar (plagioclase) ± quartz ± carbonate. The exact protolith of these rocks cannot be determined from the macroscopic and microscopic observations because of the strong and pervasive metamorphic overprint of the samples. We can infer that the protolith most likely was a breccia based on the different clast sizes and observed deformation styles. The pXRF and XRD data indicate a mafic igneous composition for both clasts and schists but reveal a spread from ultramafic (Subunit 1a in Hole U1504B) to more felsic (in Subunit 1b) compositions that are variable within sections and between holes at this site. However, it is unclear if this breccia with mafic clasts has a sedimentary origin (e.g., volcaniclastic) or represents an altered (potentially hydrothermally) form of a basalt, gabro, or ultramafic protolith. Determination of the exact nature and origin of the clasts will require more detailed postexpedition research. The presence of marble layers is often used as an argument for a metasedimentary origin of a metamorphic sequence. However,
<figure><img src="image_412.png" /><figcaption>Table T5. Major element oxides and minor elements in rocks, Site U1504.
**View table in PDF format. Download table in CSV format.**</figcaption></figure>

the very localized occurrence of marble observed here, as well as its impure character, could also be explained by hydrothermal modification of the protolith. In this context, the calc-silicate schists, which have variable amounts of calcite, could also be consistent with a preexisting hydrothermal breccia matrix cemented by interaction with CO₂-rich fluids.

The timing of the metamorphism and its relation to the rifting of the SCS is uncertain. A key observation is that the observed mylonitic foliation is overlain by undeformed Eocene sediments from lithostratigraphic Unit II, which implies that the metamorphism is Eocene or older. Unit 1 could therefore represent an earlier metamorphosed part of the OMH and be a part of the prerift (continental) crust. Metamorphic basement rocks (schists and quartzites) have been recovered in industry wells in the western part of the offshore Pearl River Mouth Basin (Zhou and Yao, 2009) about 200 km west-northwest of Site U1504, where they are inferred to represent the offshore continuation of the early Paleozoic Caledonian fold belt in South China (Li et al., 1989). Metamorphic rocks are also found on the conjugate margin in the northern part of Palawan Island in the Philippines (e.g., Suggate et al., 2014). The Northern Palawan Continental Terrane contains upper Paleozoic to lower Mesozoic

metasedimentary rocks (including schists; Sales et al., 1997) that experienced medium-grade regional metamorphism (Suzuki et al., 2000). Alternatively, the metamorphic event might have been related to the SCS rifting. Therefore, metamorphic lithologic Unit 1 might represent either metamorphosed continental crust (sedimentary) or metamorphosed basalts (see **Structural geology**). Detailed petrological and geochemical examination and accurate dating of the samples will be needed to address the metamorphic history of these rocks.

## Structural geology

Site U1504 is located on a basement high ~45 km north of Site U1502 and 50 km east of Site U1501 in a water depth of 2827 m. This basement high may be interpreted as a continuation of the OMH cored at Sites U1501 and U1505.

### Lithostratigraphic Unit I structures

Lithostratigraphic Unit I shows evidence for variable bedding dips, locally dipping steeply, associated with possible folds such as those observed in Section 368-U1504A-5R-1 (Figure F20). Such patterns are related to mass movements of un lithified sediments (i.e., slump folding).
Figure F20. Convolutely bedded sequence indicative of mass transport deposition in Subunit IA, Hole U1504A.

<figure><img src="image_413.png" /></figure>

## Lithostratigraphic Unit II structures

No deformation structures were observed within lithostratigraphic Unit II.

### Lithostratigraphic Unit III structures

#### Macroscopic description

The mylonitic epidote-chlorite schists and calc-silicate schists that form the metamorphic basement at Site U1504 (see **Igneous and metamorphic petrology**) consist of epidote + chlorite + quartz + microcrystalline (plagioclase) feldspar ± calcite ± accessory minerals. The rocks preserve distinct deformation structures resulting from changes in the mode of deformation (brittle/ductile); the modal amount of quartz + feldspar governing the (local) rheological

behavior; the amount of accumulated strain; the occurrence of variably sized (up to decimeter scale), prekinematic, heterolithic clasts that mostly form rigid (i.e., internally weakly to undeformed) bodies within the ductile foliation; and/or superimposed multiple deformation phases.

In Hole U1504A, measurements of the epidote-chlorite schist mylonitic foliation were often hampered by strong drilling disturbance and poor recovery. Therefore, measurements were only possible in the few continuous pieces recovered in Cores 368-U1504A-16R through 21R. These pieces show evidence for a steeply dipping foliation (as steep as 75°) (Figure F21). This mylonitic foliation is characterized by distinct morphologies: (1) a widely spaced anastomosing foliation associated with leucocratic bands (Figure F22A) and (2) a tight, closely spaced foliation associated with more melanocratic variations. Locally, a crenulation cleavage was observed (i.e., interval 368-U1504A-16R-1, 118–129 cm) (Figure F22B). Because of the combined effects of drilling disturbance and steeply inclined foliation, stretching or intersection lineations were only observed in a few rare cases.

Along this unit, angular to rounded chlorite-epidote granofels clasts (see **Igneous and metamorphic petrology**) are recognized and form rigid bodies within the ductile foliation (Figures F20, F22). Such clasts are consistently dismembered by a network of mostly parallel and perpendicular quartz veins cutting each other. They often form apparently stretched, elongated bodies oriented parallel to the foliation (Figure F22A). This veining is limited to the clasts and is absent from the epidote-chlorite schist. A folded epidote vein was observed within the epidote-chlorite schist in Section 368-U1504A-16R-1 (Figure F22C).

In Hole U1504B, more coherent pieces were recovered, allowing for a more representative record of foliation dips (Figure F21). Throughout Cores 5R through 16R, the mylonitic foliation shows predominantly steep dips >50°, and it tends to be shallower in Cores 17R through 20R, with dips clustering around ~30°–40°. In places, subvertical inclinations were encountered.

Deformation structures in Cores 5R through 9R, which represent lithostratigraphic Subunit IIIA (see **Igneous and metamorphic petrology**), are generally comparable to those encountered in Hole U1504A, which represent the same subunit. The prominent crenulation cleavage, especially, is a reoccurring feature (Figure F23B). Locally, epidote-chlorite schist split parallel to the *xy*-plane of finite strain shows sigma clasts and a shear band cutting across a granofels clast, both indicating a normal sense of shear kinematic with the mylonitic foliation (Figure F23A).

Deformation in Subunit IIIB (Cores 368-U1504A-10R through 20R; see **Igneous and metamorphic petrology**) is presumably strongly controlled by an inherited (protolithic) brecciated structure. The characteristic feature of these mylonites is a tight microcrystalline to medium-grained foliation, locally folded, enclosing heterolithic clasts of various sizes up to the decimeter scale. The clasts most often form rigid, internally weakly to undeformed bodies showing isotropic textures with sharp boundaries with the enclosing foliation (Figure F23D, F23E). However, in some cases and especially at greater depths, the clasts tend to be ductily deformed and elongated within the mylonitic foliation (Figure F23C). These clasts often show diffuse clast boundaries, indicating mechanical and/or chemical clast-matrix interactions.

Another characteristic feature of Subunit IIIB is a general increase of various quartz, calcite, ± epidote veins that can be clearly distinguished between prekinematic (mostly epidote/quartz) veins that are ductily deformed together with the foliation (Figure F23C,
<figure><img src="image_414.png" /><figcaption>Figure F21. Corrected true dip angles of mylonitic foliation measured in metamorphic lithologic Unit 1/lithostratigraphic Unit III, Holes U1504A and U1504B. CRF = core reference frame.</figcaption></figure>

F23F) and late to postkinematic slightly deformed to undeformed (calcite) veins cutting the mylonitic foliation (Figure F23G).

**Microscopic observations**

In thin sections, the mylonitic fabric is defined by alternating bands dominated by fine-grained leucocratic (quartz ± cryptopla-

gioclase) and mostly chloritic aggregates. The leucocratic bands/aggregates form locally stretched sigma clasts and ductile boudins, whereas fine-grained quartz shows evidence for dynamic recrystallization through both bulging and subgrain rotation recrystallization (Figure F24B). In quartz- to feldspar-rich levels, an
Figure F22. Ductile deformation structures in epidote-chlorite schists in Subunit IIIA, Hole U1504A. A. Steep (~75°) widely anastomosing foliation in a quartz-rich variety of the rock. Arrow = extensively stretched veined clast of chlorite-epidote granofels, oriented parallel to the foliation. B. Tight foliation affected by crenulation cleavage in quartz-poor variety of the rock (top: core photo; bottom: interpretation). C. Folded epidote vein.

<figure><img src="image_415.png" /></figure>

anastomosing foliation was locally observed. Some bands are recognized as highly deformed and extensively stretched former chlorite-epidote granofels clasts that partially preserve the original veining (Figure F24A). Chlorite is very fine grained and most probably accommodates a large amount of strain. Within the fine-grained chlorite-dominated bands, coarse-grained subhedral epidote with grain sizes as large as ~0.3 mm is commonly wrapped by the foliation and affected by brittle boudinage and brittle deformation, suggesting a prekinematic to early synkinematic crystallization with respect to the mylonitic foliation (Figure F24C). These boudinaged grains show a prismatic habitus and are aligned within the foliation, whereas other grains are strongly fractured. Locally, the coarse-grained subhedral epidote seems to partially recrystallize into fine-grained minerals and possibly into a second generation of epidote parallel to the foliation (Figure F24D). In more phyllosilicate rich levels, a seemingly pervasive crenulation cleavage is recognized (Figure F24A) that was also macroscopically visible in interval 368-U1504A-16R-1, 118–128 cm (Figure F22B).

## Interpretation

The Cenozoic sediments encountered at Site U1504 are essentially devoid of deformation structures apart from Cores 368-U1504A-4R and 5R, which are characterized by a convoluted bedding sequence. The formation of this soft-sediment deformation structure most probably involved mass movements related to gravitational instabilities on a slope in close vicinity of the top of this basement-high.

Figure F23. Deformation structures, Hole U1504B. A. Epidote-chlorite schist with granofels clasts split parallel to the xy-plane of finite strain. Large granofels clast is crosscut by shear band within the epidote-chlorite schist. Several sigma clasts are observed right above the shear band. Both deformation structures indicate normal sense of shear. A late, postkinematic vein crosscuts both mylonitic foliation and granofels clast. B. Epidote-chlorite schist with crenulation cleavage. C. Long piece of core showing characteristic morphology of mylonitic foliation in calc-silicate schist, Subunit IIIB. Note steep inclination and anastomosing geometry enclosing heterolithic clasts that are strongly elongated, folded, and oriented parallel to the foliation. D, E. Rigid granofels clasts embedded in calc-silicate schist. Note deflection of the mylonitic foliation at the clast boundaries. F. Segmented and deformed composite epidote + quartz vein within the almost gneissose foliation of more leucocratic schist variation. G. Late kinematic (left) to postkinematic (i.e., undeformed; right) calcite veins crosscutting tight mylonitic foliation.

<figure><img src="image_416.png" /></figure>

The metamorphic basement recovered at Site U1504 (litho-stratigraphic Unit III) underwent a complex history of polyphase metamorphism and deformation. Formation of these rocks may have involved significant fluid-rock interactions that influenced both their chemical composition and rheological behavior.

The observed mylonitic fabric formed at greenschist facies conditions. The occurrence of a seemingly pervasive crenulation cleavage in macro- and microscopic observations on chlorite-rich samples may indicate either a reorientation of the local paleostress field during ongoing deformation or, alternatively, a polyphase structural evolution. A first brittle deformation phase is docu-
Figure F24. Metamorphic basement with focus on microstructural observations in metamorphic lithologic Unit 1/lithostratigraphic Unit III, Site U1504. Thin section domains are shown (left = PPL; right = XPL). A. Epidote-chlorite schist with minor modal quartz forming thin, discontinuous bands within foliation (black lines). Crenulation cleavage indicates a second deformation phase (white lines). Some quartz-rich aggregates are recognized as deformed chlorite-epidote granofels clasts preserving original veining. B. Sigma clast consisting of mainly quartz with minor chlorite and epidote probably representing deformed chlorite-epidote granofels clast preserving original veining. Sigma clast is synkinematic with respect to main mylonitic foliation and also affected by late crenulation cleavage. Tails of the sigma clast show clear evidence for subgrain rotation recrystallization. C. Prismatic, coarse, prekinematic epidote grain passively rotated into the foliation and underwent subsequent axial stretching and brittle boudinage. D. Coarse-grained epidotes showing irregular shapes, locally some crystals are observed to break down to fine-grained minerals.

<figure><img src="image_417.png" /><figcaption>Table T6. Distribution of diatoms, Site U1504. **View table in PDF format. Download table in CSV format.**</figcaption></figure>

mented by the presence of strongly veined clasts, indicating possibly an early cataclastic and/or hydrothermal deformation episode, although the clasts themselves might also form part of a coarse (meta-) sedimentary protolith (e.g., a metamorphosed, volcaniclastic conglomerate/breccia). The veining episode apparently post-dates a first metamorphic event because associated quartz veins clearly cut the chlorite-epidote granofels without any visible chemical interaction.

The origin of the encountered greenschist facies mylonites and their attribution to either SCS rifting or to Mesozoic or older tectonic events such as the Yenshanian orogeny (Hsieh, 1936) remains unknown at the moment, posing a challenging scientific question for postexpedition research (see **Igneous and metamorphic petrology**). Solving this question requires a determination of (1) the protolith of the rock, (2) its pressure-temperature (P-T) deformation history, and (3) accurate geochronological constraints. The present-day orientation of the mylonites with foliation dips as steep as 75°, however, seems too steep to represent a synrift, top-baseMENT, low-angle detachment fault that may have exhumed deep crustal levels.

Biostratigraphy

All core catcher samples from Site U1504 were analyzed for calcareous nannofossils, foraminifers, and diatoms. Additional samples were taken from intervals within the working-half core sections when necessary to refine the ages. Preservation of calcareous

microfossils is good to very good in Cores 368-U1504A-2R through 12R and Core 368-U1504B-2R and poorly preserved (recrystallization) deeper than Core 368-U1504A-12R, where reefal limestone was sampled. Diatoms were present but poorly preserved in Cores 368-U1504A-2R through 5R and absent from the rest of the samples (Table T6).

Planktonic foraminifers and calcareous nannofossils are abundant in Cores 368-U1504A-2R through 12R and Core 368-U1504B-2R and barren in Cores 368-U1504A-13R through 15R. Twenty biostratigraphic datums were identified in a succession from the late Pleistocene to the early Miocene (Tables T7, T8; Figure F25).

A possible hiatus between the early Pleistocene and late Miocene was determined within Core 368-U1504A-6R by abrupt changes in the planktonic foraminiferal and nannofossil assemblages. Based on the site's biostratigraphy, sedimentation rates are estimated to vary from ~6 mm/ky in the early middle Miocene to ~22 mm/ky during the Pleistocene.

Cores 368-U1504A-13R through 15R are mainly composed of reefal and larger benthic foraminiferal limestone that indicates a warm shallow-marine environment. In contrast, the abundant planktonic foraminifers and calcareous nannofossils in Cores 2R through 12R suggest a deep-sea environment overlying the reefal rocks since the early Miocene.
<table><caption>Table T7. Calcareous nannofossil biostratigraphic events, Site U1504. O = occurrence, T = top/last appearance datum, B = bottom/first appearance datum. Download table in CSV format.</caption><thead><tr><th rowspan="2">Epoch</th><th rowspan="2">Biozone (Martini, 1971)</th><th rowspan="2">Calcareous nannofossil event</th><th colspan="2">Top</th><th colspan="2">Bottom</th><th colspan="2">Age model</th></tr><tr><th>Core, section, interval (cm)</th><th>Depth CSF-A (m)</th><th>Core, section, interval (cm)</th><th>Depth CSF-A (m)</th><th>Depth (m)</th><th>Age (Ma)</th></tr></thead><tbody><tr><td rowspan="3">Pleistocene</td><td>NN21</td><td>B Emiliania huxleyi</td><td>368-U1504A-3R-CC</td><td>21.35</td><td>368-U1504A-4R-CC</td><td>31.75</td><td>26.55</td><td>0.29</td></tr><tr><td rowspan="2">NN19</td><td>T Pseudoemiliania lacunosa</td><td>3R-CC</td><td>21.35</td><td>4R-CC</td><td>31.75</td><td>26.55</td><td>0.44</td></tr><tr><td>B Gephyrocapsa spp. &gt;4 µm</td><td>5R-CC</td><td>38.53</td><td>6R-1, 60–61</td><td>47.10</td><td>42.82</td><td>1.73</td></tr><tr><td rowspan="4">middle Miocene</td><td>NN6</td><td>T Cyclicargolithus floridanus</td><td>5R-CC</td><td>38.53</td><td>6R-1, 60–61</td><td>47.10</td><td>42.82</td><td>11.85</td></tr><tr><td>NN5</td><td>T Sphenolithus heteromorphus</td><td>6R-CC</td><td>52.13</td><td>7R-CC</td><td>59.78</td><td>55.96</td><td>13.53</td></tr><tr><td>NN4</td><td>T Helicosphaera ampliaperta</td><td>7R-CC</td><td>59.78</td><td>8R-CC</td><td>73.56</td><td>66.67</td><td>14.91</td></tr><tr><td>NN4</td><td>B Sphenolithus heteromorphus</td><td>9R-CC</td><td>78.31</td><td>10R-CC</td><td>93.96</td><td>86.14</td><td>17.71</td></tr><tr><td rowspan="4">early Miocene</td><td rowspan="4">NN2</td><td>T Triquetrorhabdulus carinatus</td><td>9R-CC</td><td>78.31</td><td>10R-CC</td><td>93.96</td><td>86.14</td><td>18.28</td></tr><tr><td>B Sphenolithus belemnos</td><td>12R-1, 3–5</td><td>104.85</td><td>12R-1, 40–42</td><td>105.22</td><td>105.04</td><td>19.03</td></tr><tr><td>B Helicosphaera ampliaperta</td><td>12R-1, 3–5</td><td>104.85</td><td>12R-1, 40–42</td><td>105.22</td><td>105.04</td><td>20.43</td></tr><tr><td>O Sphenolithus disbelemnos</td><td>12R-CC</td><td>112.66</td><td></td><td></td><td>112.66</td><td>&lt;22.76</td></tr></tbody></table>

<table><caption>Table T8. Planktonic foraminifer events, Site U1504. T = top/last appearance datum, B = bottom/first appearance datum. Download table in CSV format.</caption><thead><tr><th rowspan="2">Epoch</th><th rowspan="2">Biozone (Blow, 1969)</th><th rowspan="2">Calcareous nannofossil event</th><th colspan="2">Top</th><th colspan="2">Bottom</th><th colspan="2">Age model</th></tr><tr><th>Core, section, interval (cm)</th><th>Depth CSF-A (m)</th><th>Core, section, interval (cm)</th><th>Depth CSF-A (m)</th><th>Depth (m)</th><th>Age (Ma)</th></tr></thead><tbody><tr><td rowspan="3">Pleistocene</td><td>N22</td><td>T Globigerinoides ruber (pink)</td><td>368-U1504A-</td><td></td><td>368-U1504A-</td><td></td><td></td><td></td></tr><tr><td>N22</td><td>B Globigerinoides ruber (pink)</td><td>4R-CC</td><td>31.75</td><td>2R-CC</td><td>7.85</td><td>3.93</td><td>0.12</td></tr><tr><td>N20–N21</td><td>B Globorotalia truncatulinoides</td><td>5R-CC</td><td>38.53</td><td>6R-CC</td><td>38.53</td><td>35.14</td><td>1.16</td></tr><tr><td rowspan="6">Miocene</td><td>N12</td><td>T Fohsella fohsi</td><td>5R-CC</td><td>39.53</td><td>6R-CC</td><td>52.13</td><td>45.83</td><td>11.79</td></tr><tr><td>N8</td><td>T Praeorbulina circularis</td><td>6R-CC</td><td>52.13</td><td>7R-CC</td><td>59.78</td><td>55.96</td><td>14.89</td></tr><tr><td>N8</td><td>B Praeorbulina glomerosa</td><td>9R-CC</td><td>78.31</td><td>10R-CC</td><td>93.96</td><td>86.14</td><td>16.27</td></tr><tr><td>N6</td><td>T Catapsydrax dissimilis</td><td>9R-CC</td><td>78.31</td><td>10R-CC</td><td>93.96</td><td>86.14</td><td>17.54</td></tr><tr><td>N5</td><td>T Globoquadrina binaiensis</td><td>12R-1, 3–5</td><td>93.96</td><td>12R-1, 40–42</td><td>105.22</td><td>99.59</td><td>19.09</td></tr><tr><td>N4</td><td>T Paragloborotalia kugleri</td><td>12R-1, 40–42</td><td>105.22</td><td>12R-CC</td><td>112.61</td><td>108.92</td><td>21.12</td></tr></tbody></table>

## Calcareous nannofossils

The calcareous nannofossil biostratigraphy for Site U1504 is based mainly on the analysis of all core catcher samples from Hole U1504A (Table T9). To better constrain biostratigraphic events, a number of samples from intervals within cores were analyzed.

Calcareous nannofossils are very abundant and well preserved in the upper part of the succession (Cores 2R through 12R; 7.85–112.66 m) and become barren from Sample 13R-CC (114.8 m) to the bottom of Hole U1504A. Reworking is common in samples from the Pleistocene, and overgrowth is common in those from early Miocene.

Eleven nannofossil biostratigraphic datums were recognized in the early Miocene through Pleistocene sediment sequence at Site U1504 (Table T7). The Pliocene and late Miocene nannofossil Zones NN18 through NN7 are missing in Hole U1504A, but some specimens of those periods, such as *Discoaster brouweri*, *Discoaster pentaradiatus*, *Discoaster quinqueramus*, *Discoaster berggrenii*, *Re-ticulofenestra pseudoumbilicus*, and *Sphenolithus* spp., were observed in the Pleistocene samples. The oldest nannofossil event identified at Site U1504 is the occurrence of *Sphenolithus disbelemnos* (its first occurrence datum [FAD] dates to 22.76 Ma), which was observed in the lowermost nannofossil-bearing sample at 112.66 m, indicating an early Miocene age of <22.76 Ma.

### Pleistocene

The top of Hole U1504A (Samples 2R-CC to 5R-CC; 7.85–38.53 m) is dated as late Pleistocene based on the presence of *Emiliania*

*huxleyi* (marker species for Zone NN21). The last occurrence datum (LAD) of *Pseudoemiliania lacunosa* in Sample 4R-CC (31.75 m) defines the top of Zone NN19. Zone NN19 is further divided by the FAD of medium *Gephyrocapsa* spp. (>4 µm) in Sample 5R-CC (38.53 m).

### Middle to early Miocene

Three events were observed in the middle Miocene strata of Hole U1504A. The top of Zone NN6 is marked by the LAD of *Cyclicargolithus floridanus* (11.85 Ma) in Sample 6R-1, 60–61 cm (47.1 m). The top of Zone NN5 is defined by the LAD of *Sphenolithus heteromorphus* (13.53 Ma) in Sample 7R-CC (59.78 m). The top of Zone NN4 is defined by the LAD of *Helicosphaera ampliaperta* (14.91 Ma) in Sample 8R-CC (73.56 m). The middle/early Miocene boundary is assigned between Samples 8R-CC (73.56 m) and 9R-CC (78.31 m).

Three events were observed in the early Miocene strata of Hole U1504A. The top of Zone NN2 is marked by the LAD of *Triquetrorhabdulus carinatus* (18.28 Ma) in Sample 10R-CC (93.96 m). The FADs of *Sphenolithus belemnos* (19.03 Ma) and *H. ampliaperta* (20.43 Ma) apparently co-occur in Sample 12R-1, 3–5 cm (104.85 m). The occurrence of *S. disbelemnos* (its FAD dated to 22.76 Ma) was observed in Sample 12R-CC (112.66 m), which lies immediately above the nannofossil-barren interval that extends down to the bottom of this hole, indicating an age younger than 22.76 Ma at this depth.

The sole sediment core catcher sample above a coral reef limestone in Hole U1504B (2R-CC; 92.37 m) yielded a nannofossil as-
<figure><img src="image_418.png" /><figcaption>Table T9. Distribution of calcareous nannofossils, Site U1504. **View table in PDF format. Download table in CSV format.**</figcaption></figure>

<caption>Table T10. Distribution of planktonic foraminifers, Site U1504. **View table in PDF format. Download table in CSV format.**</caption>

semblage similar to that of Sample 368-U1504A-12R-CC. An age of 20.43–22.76 Ma was assigned to this depth based on the occurrence of *S. disbelemnos* and the absence of *H. ampliaperta*.

## Planktonic foraminifers

All core catcher samples and two additional samples from the working-half cores from Holes U1504A and U1504B were processed for planktonic foraminiferal analyses (Table T10). Planktonic foraminifers are well preserved and abundant in samples from Cores 368-U1504A-2R through 12R and Core 368-U1504B-2R and barren in Cores 368-U1504A-13R through 15R.

Nine planktonic foraminiferal datums were recognized in Hole U1504A, spanning from the early Miocene (>21.12 Ma) to the late Pleistocene (Table T8). The planktonic foraminiferal biostratigraphy for Hole U1504A was established based on these events and

the planktonic foraminiferal assemblages at successive depth intervals.

The Pleistocene planktonic foraminifers are composed of *Globigerinoides ruber*, *Globigerinoides sacculifer*, *Globigerinoides conglobatus*, *Globorotalia menardii*, *Pulleniatina obliquiloculata*, *Neogloboquadrina dutertrei*, and *Orbulina universa*. The LAD of pink *G. ruber* (0.12 Ma) and the FAD of pink *G. ruber* (1.16 Ma) are placed within Sample 2R-CC and between Samples 4R-CC and 5R-CC, respectively. The FAD of *Globigerinoides truncatulinoides* (1.93 Ma) is located between Samples 5R-CC and 6R-CC. However, no Pliocene or late Miocene planktonic foraminiferal datum was recognized due to the distinct faunal changes between Samples 5R-CC and 6R-CC from the middle Miocene assemblage to the Pleistocene assemblage. The middle Miocene foraminiferal assemblages are dominated by *Dentoglobigerina altispira*, *Globoquadrina dehiscens*, *Globoquadrina venezuelana*, *Globoquadrina baroemoenensis*, and *Praeorbulina circularis/glomerosa*. The LAD of *Fohsella fohsi* (11.79 Ma) is located between Samples 5R-CC and 6R-CC. The LAD of *P. circularis* (14.89 Ma) is located between Samples 6R-CC and 7R-CC and marks the boundary of Zones N8 and N7. Both the FAD of *P. glomerosa* (16.27 Ma) and the LAD of *Catapsydrax dissimilis* occur
Figure F26. Larger benthic foraminiferal fragments (Nummulites sp.; 368-U1504A-14R-CC).

<figure><img src="image_419.png" /></figure>

Figure F27. Abundant larger benthic foraminifers (Nummulites sp. and Assi-lina sp.; 368-U1504A-15R-CC).

<figure><img src="image_420.png" /><figcaption>Table T11. Diatom event, Site U1504. T = top/last appearance datum. Download table in CSV format.</figcaption></figure>

<table><thead><tr><th rowspan="2">Epoch</th><th rowspan="2">Biozone<br>(Scherer et al.,<br>2007)</th><th rowspan="2">Calcareous<br>nannofossil<br>event</th><th colspan="2">Bottom</th><th colspan="2">Age model</th></tr><tr><th>Core,<br>section</th><th>Depth<br>CSF-A<br>(m)</th><th>Depth<br>(m)</th><th>Age<br>(Ma)</th></tr></thead><tbody><tr><td>Pleistocene</td><td>Fragilariopsis<br>doliolus</td><td>T Fragilariopsis<br>reinholdii</td><td>368-U1504A-<br>4R-CC</td><td>31.75</td><td>31.75</td><td>&lt;0.62</td></tr></tbody></table>

between Samples 9R-CC and 10R-CC, suggesting the middle/early Miocene boundary within Core 10R.

The early Miocene planktonic foraminifers are characterized by *G. dehiscens*, *G. venezuelana*, and *Paragloborotalia mayeri*. The LAD of *C. dissimilis* (17.54 Ma) is located between Samples 9R-CC and 10R-CC and indicates the boundary of Zones N7 and N6. The LAD of *Globoquadrina binaiensis* (19.09 Ma) is located between Samples 12R-1, 3–5 cm, and 12R-1, 40–42 cm. The LAD of *Paragloborotalia kugleri* (21.12 Ma) is located between Samples 12R-1, 40–42 cm, and 12R-CC and indicates the boundary of Zones N5 and N4.

In Hole U1504B, only one soft-sediment core was obtained above the coral reef limestone. The occurrence of *P. kugleri* and *G. dehiscens* in Sample 368-U1504B-2R-CC constrains the age between 21.12 and 22.44 Ma, which corresponds to the age of Sample 368-U1504A-12R-CC (Table T8).

## Benthic foraminifers

Larger benthic foraminifers were observed in samples from Core 368-U1504A-14R (Figure F26) and Sample 15R-1, 21–23 cm

(Figures F12, F27; see Lithostratigraphy), including *Nummulites* and other genera that indicate an Eocene or slightly younger age and a warm, shallow-marine environment.

## Diatoms

All of the core catcher samples from Hole U1504A and one from U1504B were processed into smear and strewn slides for diatom analysis. Three additional toothpick samples were taken from selected intervals of the working-half cores for better resolution. Samples 368-U1504A-2R-CC, 3R-CC, and 4R-CC are composed of between 10% and 90% diatoms with poor preservation. The rest of the core catcher samples from Cores 5R through 12R were barren of diatoms (Table T6). Samples 2R-CC, 3R-CC, and 4R-CC contain a typical late Pleistocene (Table T11) tropical-subtropical diatom assemblage such as *Fragilariopsis doliolus* and *Nitzschia interruptestriata*. *Fragilariopsis reinholdii* (LAD = 0.62 Ma) was not observed in Sample 4R-CC, suggesting an age younger than 0.62 Ma.

## Paleomagnetism
Shipboard measurements

Shipboard paleomagnetic investigations combined two complementary approaches (see **Paleomagnetism** in the Expedition 367/368 methods chapter [Sun et al., 2018]): (1) measurement and in-line AF demagnetization of archive-half sections on the pass-through 2G Enterprises SRM at 2.5 cm spacing and (2) measurement and AF demagnetization of oriented discrete samples on the spinner magnetometer (AGICO JR-6A). Thirteen representative discrete samples from sedimentary units and four from basement were collected for AF demagnetization.

We used scalar data from discrete samples from AF demagnetization up to 120 mT to assess the nature of the magnetic assemblage. We used the directional and intensity data of archive-half sections, measured after in-line AF demagnetization (up to 15 mT), to determine magnetic polarity along the core. Directional data were analyzed using Zijderveld diagrams (Zijderveld, 1967), and characteristic remanent magnetization (ChRM) direction(s) were calculated by principal component analysis (PCA) (Kirschvink, 1980) using PuffinPlot (version 1.03, April 23, 2015) (Lurcock and Wilson, 2012).

## Demagnetization behavior and implications for magnetic assemblages

### Sediment

Units: I and II

Depths: Hole U1504A = 17.50–134.80 m; Hole U1504B = 88.20–107.91 m

Sections 368-U1504A-3R-1 through 15R-1 and Cores 368-U1504B-2R through 4R

Most of the 13 discrete samples investigated show soft magnetic behavior characterized by loss of >50% of NRM below 20 mT (Figure F28). This low coercivity (soft behavior) justifies the steps chosen for in-line stepwise demagnetization (0, 5, 10, and 15 mT) on the SRM. Most discrete samples also display a gain in magnetization above 70 mT, up to 30% of the NRM, which is interpreted as resulting from GRM. Both greigite and pyrrhotite are known to display this behavior in marine sediments (e.g., Thompson, 1990; Roberts
Figure F28. AF demagnetization plots of (A) discrete samples and (B, C) archive-half sections of sedimentary rocks, Hole U1504A. Zijderveld plots: solid squares = declination, open squares = inclination. Stereographic plots: solid squares = positive (down) inclination, open squares = negative (up) inclination. Calculated ChRM (blue line; red squares = measurements used in calculation) using PCA is also shown. A. Soft demagnetization behavior up to 10 mT associated with removal of drilling overprint, followed by gradual demagnetization from 10 to 60 mT, characteristic of single-domain or pseudosingle-domain magnetite, and finally magnetization gain above 70 mT indicative of GRM, most likely due to greigite. B. Removal of drilling overprint in first step (5 mT). C. Soft demagnetization behavior and negative inclination of sample. MAD = maximum angular deviation.

A 368-U1504A-9R-1W, 100-102 cm, 76.50 m

<figure><img src="image_421.png" /></figure>

B 368-U1504A-3R-1A, 30 cm, 17.8 m

<figure><img src="image_422.png" /></figure>

C 368-U1504A-12R-1A, 87.5 cm, 105.675 m

<figure><img src="image_423.png" /></figure>

et al., 2011); however, greigite is more likely in shallow-marine sediments and has already been identified in lithostratigraphic Unit I in nearby Hole U1501C (see Paleomagnetism in the Site U1501 chapter [Larsen et al., 2018a]). Steep normal inclinations (≈60°) across all units suggest magnetic drilling overprint (Figure F29) that is easily removed by demagnetization to 10 mT (Figure F28). This behavior is consistent with the presence of a low-coercivity phase, such as relatively coarse grained titanomagnetite, in the sediments.

The core sections measured by in-line AF demagnetization on the SRM confirm the relatively soft demagnetization behavior observed on the discrete samples. Stepwise demagnetization up to 15 mT effectively removed the drilling overprint and allowed delineation of several reversals (Figure F29).

Basement rocks

Unit: III

Depths: Hole U1504A = 136.40–163.70 m; Hole U1504B =
117.40–196.28 m

Cores 368-U1504A-16R through 21R and 368-U1504B-5R
through 20R

NRM intensities of basement rocks were measured on the SRM
(archive-half Cores 368-U1504A-16R through 21R) and on the JR-

6A spinner magnetometer (four discrete cubes, 8 cm³ each). The in-
tensities of magnetization are low (average = 78 × 10⁻⁶ A/m). Some
of the discrete samples were not demagnetized because of their low
NRM intensity (Figure F29), which requires measurements in a
shielded laboratory.

Magnetostratigraphy

Inclination, declination, and intensity in Hole U1504A are re-
ported in Figure F29. We constructed the magnetostratigraphy
based on the polarity assigned to the archive-half cores, which was
corroborated by directions obtained from oriented discrete sam-
ples. A succession of nine normal and eight reversed intervals was
recognized. We tentatively correlated the magnetostratigraphic
data in Hole U1504A to the standard timescale (Ogg et al., 2016)
according to initial biostratigraphy age constraints reported in Table
T12 and Figure F25.

Anisotropy of magnetic susceptibility

Sediment

Units: I and II

Depth: Hole U1504A = 17.50–134.80 m

Cores 368-U1504A-3R-1 through 15R-1
Figure F29. Magnetic measurements, Hole U1504A. Inclination used to determine polarity. AFD = AF demagnetization. Magnetostratigraphic features are referred to as n1, etc., in a sequential manner for convenience and have no bearing on chron. GPTS2016 = geomagnetic polarity timescale of Ogg et al. (2016).

<figure><img src="image_424.png" /><figcaption>Table T12. Paleomagnetic age datums, Hole U1504A. *r* = reversed, *n* = normal. Download table in CSV format.</figcaption></figure>

<table><thead><tr><th>Magnetic polarity</th><th>Depth CSF-A at base of interpreted magnetic polarity (m)</th><th>Polarity chron</th><th>Base of chron (Ma)</th></tr></thead><tbody><tr><td>r1</td><td>29.11</td><td>C1r.1r</td><td>1.008</td></tr><tr><td>r2</td><td>57.48</td><td>C5ABr</td><td>13.739</td></tr><tr><td>r3</td><td>66.73</td><td>C5Bn.1r</td><td>15.032</td></tr><tr><td>n6</td><td>70.81</td><td>C5Bn.2n</td><td>15.160</td></tr><tr><td>r5</td><td>76.02</td><td>C5Cr</td><td>17.235</td></tr><tr><td>n7</td><td>77.45</td><td>C5Dn</td><td>17.533</td></tr><tr><td>r7</td><td>105.77</td><td>C6An.1r</td><td>20.439</td></tr><tr><td>n9</td><td>109.28</td><td>C6An.2n</td><td>20.709</td></tr></tbody></table>

The 13 discrete samples have magnetic susceptibilities (κ) ranging from ≈60 × 10⁻⁶ to 405 × 10⁻⁶ SI. These low κ values combined with the low NRM suggest that the magnetic susceptibility is controlled by both paramagnetic silicates (e.g., clays and chlorite) and ferromagnetic phases (e.g., greigite and magnetite). The degree of magnetic anisotropy (*P*') is moderate (~1.025), whereas the AMS fabric is strongly oblate as shown by shape parameter (*T*), most likely of depositional origin. The Fisher distribution of AMS principal axes also suggests an oblate fabric (Figure F30) with a nearly horizontal planar fabric. These sedimentary fabrics are consistent with deposition in a calm, pelagic environment with very limited traction on sedimentary particles.

## Basement rocks

Unit: III

Depths: Hole U1504A = 136.40–163.70 m; Hole U1504B = 117.40–196.28 m

Cores 368-U1504A-16R through 21R and 368-U1504B-5R through 20R

The four discrete basement samples show consistent AMS fabrics even though the core is azimuthally unoriented (Figure F31). These cubes show moderate to high degrees of magnetic anisotropy (*P*' ≈ 1.05–1.09), oblate (i.e., flattened) fabric symmetries (*T* ≈ 0.2–0.6), magnetic foliations with moderate to steep dip angles (44°–
81°), and variably plunging magnetic lineations. Based on these four samples, the direction of slip along the shear zone is most likely an

oblique slip motion (with a normal or reversed component to be determined).

Figure F30. AMS data, Hole U1504A sediments. A. Stereonet of AMS principal directions for 13 discrete samples (lower hemisphere, equal-area projection). $K_1$ = maximum axis, $K_2$ = intermediate axis, $K_3$ = minimum axis. Confidence ellipses at 95% level (same color convention) show dominantly planar and subhorizontal fabric (oblate), consistent with sedimentary fabric acquired in a calm pelagic environment. Tensorial means are shown with larger symbols of same color. B. Degree of magnetic anisotropy ($P'$) vs. magnetic susceptibility ($K_m$) showing a slight increase in $P'$ with $K_m$; increase typically occurs in materials in which AMS is controlled, at least in part, by ferromagnetic phases. C. Shape parameter ($T$) vs. $P'$ showing dominantly oblate symmetry of sedimentary fabric in Unit I and II.

<figure><img src="image_425.png" /></figure>

<figure><img src="image_426.png" /></figure>

<figure><img src="image_427.png" /></figure>

Figure F31. AMS data, Hole U1504A and U1504B basement. A. Stereonet of AMS principal directions for four discrete samples (lower hemisphere, equal-area projection). $K_1$ = maximum axis, $K_2$ = intermediate axis, $K_3$ = minimum axis. Confidence ellipses cannot be calculated due to low sample number. B. Degree of magnetic anisotropy ($P'$) vs. magnetic susceptibility ($K_m$). C. Shape parameter ($T$) vs. $P'$ showing oblate symmetry of basement rock fabric in Unit III. D. Stereonet of AMS foliations, defined by $K_1$–$K_2$ axes and plotted as a great circle with AMS lineations ($K_1$ axis) plotted as a square. Because RCB core is not azimuthally oriented, AMS fabrics of these samples can be rotated to any position about the vertical core axis. Because AMS foliation matches macroscopic foliation observed on core, both AMS fabrics can be arbitrarily reoriented to a common north–south foliation strike. After this vertical axis rotation, AMS lineations show variable plunges.

<figure><img src="image_428.png" /></figure>

<figure><img src="image_429.png" /></figure>

<figure><img src="image_430.png" /></figure>

<figure><img src="image_431.png" /></figure>
# Geochemistry

Hydrocarbon gases were not detected above background levels at Site U1504, and TOC, TN, and TS contents were low, likely reflecting poor preservation of organic matter. Instances of high carbonate content were associated with carbonate lithology. The upper part of the sediment was not cored. Interstitial water major cations and anions from the cored sediments are broadly comparable to other sites. Inductively coupled plasma-atomic emission spectroscopy analysis was not performed on samples collected at Site U1504.

## Headspace gas

Headspace gas samples were taken at a frequency of one sample per core or per 10 m of drilling advance for routine safety monitoring to Section 368-U1504A-18R-1 (149.18 m). After this depth, because of the absence of methane in previous samples and the nature of the metamorphic lithologies encountered (low porosity and organic carbon content), an operational decision was made to no longer make headspace gas measurements.

## Bulk sediment organic geochemistry

### Lithostratigraphic Unit I

TOC, TN, and TS levels are low in all samples collected from Unit I (TOC < 1 wt%, TN < 0.1 wt%, and TS is frequently below de-

tection limit) (Table T13; Figure F32). Subunit IA has TOC values >0.5 wt%, notable sulfur contents, and low carbonate contents. Other lithostratigraphic subunits within Unit I had higher carbonate contents and lower sulfur contents.

### Lithostratigraphic Unit II

Lithostratigraphic Unit II has a high carbonate content, and based on the results of the standard testing procedure used by IODP to determine TOC content by difference between total and inorganic carbon, it also has a TOC content as high as 1 wt%. Therefore, the higher TOC content could result from a carbon phase unamenable to acid digestion using a weak acid (in such a situation the proportion of inorganic carbon is underestimated and the proportion of organic carbon is overestimated). The TOC/TN ratio for the interval is high, indicating a nitrogen-poor material, which generally is interpreted as representing a terrestrial-derived source of organic matter (Hedges et al., 1988). It could, however, also result from organic matter being exposed and reworked in shallow water (e.g., a lagoon) or caused by overestimation of TOC.

## Summary

Overall, the organic matter at Site U1504 falls into two categories (Figure F33). Subunit IA has relatively high TOC and TS, indicating reducing conditions during early diagenesis (Berner and Raiswell, 1984), and, based on its low TOC/TN ratio (high nitrogen content), it is likely derived from aquatic organic matter (Hedges et al., 1988). The rest of the samples have higher carbonate content and higher TOC/TN ratios due to biological inputs of calcite and reworked or land/plant-derived organic matter.

<caption>Table T13. Carbon, nitrogen, and sulfur, Hole U1504A. View table in PDF format. Download table in CSV format.</caption>

<figure><img src="image_432.png" /><figcaption>Figure F32. TOC, TOC/TN ratio and carbonate, and TS in bulk sediments. OB = overburden.</figcaption></figure>
Figure F33. Geochemical parameters of bulk sediments: carbonate vs. TOC/TN ratio and TS vs. TOC. Solid circles = lithostratigraphic Subunit IA, open triangles = Subunits IB-ID, crosses = Unit II.

<figure><img src="image_433.png" /><figcaption>Table T14. Interstitial water analyses, Hole U1504A. View table in PDF format. Download table in CSV format.</figcaption></figure>

## Raman and surface enhanced Raman spectroscopy

Because of resource constraints, Raman measurements were not performed at this site.

### Interstitial water chemistry

Shipboard analyses were performed on interstitial waters squeezed from 5–10 cm long whole-round sediment samples from Hole U1504A. About 30 mL of interstitial water was squeezed per sample. Interstitial water geochemical parameters are listed in Table T14 and presented in Figure F34.

A maxima for alkalinity is observed in the uppermost sample (Section 368-U1504A-3R-2), and thereafter alkalinity decreases with increasing depth to the bottom of the hole. The phosphate and ammonium profiles are similar: both decrease with depth, likely due to degradation of organic matter. Typically, these changes occur rapidly at shallow depths (uppermost few meters), and it is notable that both substrates still appear to be actively consumed. Sulfate concentrations vary from 22.5 to 24.7 mM throughout the cored sediment; these are low values compared to the seawater value (28.9 mM), indicating sulfate reduction likely linked to organic matter degradation. The range of pH values observed is from 7.7 to ~7.9,

slightly lower than modern seawater; the variations of pH values show a similar trend to those of alkalinity.

Calcium concentrations increase with depth to a maximum at the bottom of the hole, whereas magnesium concentrations decrease with depth, likely because of carbonate dissolution and re-crystallization of new carbonate phases. Potassium concentrations decrease linearly with depth from 12.2 to 9.6 mM, which could be interpreted as the consequence of vertical diffusion. Sodium concentrations range between 480 and 487 mM throughout the core. Only small variations in Cl and Br content were observed, and their concentrations are similar to those of modern seawater: 559–567 mM for chloride and 0.86–0.88 mM for bromide.

## Discussion

Surface samples were not collected, which prevented evaluation of early stage diagenetic processes related to the breakdown of organic carbon. Hence, it cannot easily be verified if the site currently possess a sulfate–methane transition. However, it is notable that shallow sediments have high TS contents (solid-phase sulfur) that correspond to pyrite within the samples. This topmost-cored interval has low sulfate; thus, it is reasonable to assume that sulfate is converting to sulfide at some point and that this sulfide is now likely preserved in the sediments as pyrite. Methane may have been lost via oxidation to carbonate formation, diffusion, or other mass transfer processes. Relative to other Expedition 368 sites, the site has low organic carbon preservation with far more carbon sequestered as carbonate.
<figure><img src="image_434.png" /><figcaption>Figure F34. Interstitial water alkalinity, major cations, and anions.</figcaption></figure>

## Physical properties

Physical property measurements were performed on cores from Hole U1504A (17.50–165.5 m) and Hole U1504B (88.2–195.2 m). NGR, magnetic susceptibility, gamma ray attenuation (GRA) bulk density, and *P*-wave velocity were measured on the whole-round cores. Point magnetic susceptibility, red green blue (RGB), and color reflectance were measured on archive-half sections. All analyses were conducted at a sampling resolution of 2 cm. *P*-wave velocity was also measured using the *P*-wave caliper (PWC) system on split cores in liner and on individual pieces from working-half sections without liner. Thermal conductivity measurements were performed on Section 3 of each core. Moisture and density (MAD) measurements in Hole U1504A were performed on discrete samples, generally taken at a resolution of 1 sample every other section. MAD samples were not taken from Hole U1504B to preserve material for postcruise research.

Physical property measurements from Holes U1504A and U1504B are consistent between the two holes and compare well to the lithostratigraphic units (see also **Lithostratigraphy**). At Site U1504, four PP units were distinguished according to variations in physical properties: PP Unit 1 (17.50–45 m in Hole U1504A) is characterized by very low density (average of ~1.5 g/cm³), porosity (~75%), and *P*-wave velocity (~1500 m/s). PP Unit 2 (45–114 m in Hole U1504A and 88.2–93 m in Hole U1504B) has higher density (~1.7 g/cm³) and *P*-wave velocity (average = 1590 m/s) values than the overlying PP Unit 1. PP Unit 3 (114–135 m in Hole U1504A and 93–110 m in Hole U1504B) is marked by significant increases in *P*-

wave velocity and bulk density. However, very few physical property results were obtained from this unit because of poor core recovery. PP Unit 4 (135–165.5 m in Hole U1504A and 110–195.2 m in Hole U1504B) has the highest *P*-wave velocity and bulk density and the lowest NGR values compared with the three overlying units. A more detailed description of physical properties of different units is given below.

## Natural gamma radiation

NGR counts range between ~25 and 35 counts/s in PP Unit 1 and exhibit no noticeable trend with depth (Figure F35), which may be due to limited core recovery. PP Unit 2 is generally characterized by greater amplitude in NGR values (15–35 counts/s) than Unit 1. In PP Units 3 and 4, NGR values show a slightly increasing trend from ~5 to 20 counts/s with depth. NGR values are relatively high (~50 counts/s) at ~152 and ~168 m in Hole U1504B.

### *P*-wave velocity

In Holes U1504A and U1504B, *P*-wave velocity measurements are consistent between whole-round and split core sections (Figure F35). In PP Unit 1, *P*-wave velocity shows little variation with an average of 1500 m/s. PP Unit 2 is distinguished by a slight increase in velocity in the upper section to 1560 m/s and velocities that increase slowly with depth to ~1700 m/s. In contrast, PP Unit 3 is marked by an abrupt change to high *P*-wave velocities (~3000–5000 m/s). Similarly, the *P*-wave velocities of PP Unit 4 are high (~5000–6100 m/s) and represent the metamorphic rocks in lithostratigraphic Unit III (see **Lithostratigraphy**).
<figure><img src="image_435.png" /><figcaption>Figure F35. Physical properties for Holes U1504A and U1504B with petrophysical (PP) units. Note that in PP Units 3 and 4, the scattered GRA density measurements are less reliable due to void between core material and core liner. Descriptions and discussions in text are based on discrete samples of bulk density (MAD). cps = counts per second.</figcaption></figure>

## Thermal conductivity

Thermal conductivity measurements are well defined in the designated physical property units. In Hole U1504A, PP Unit 1 has lower thermal conductivity ranging from 0.970 to 1.047 W/(m·K) (Figure F35) followed by a higher thermal conductivity regime ranging from 1.089 to 1.204 W/(m·K) that corresponds to PP Unit 2.

Because of the small size of core pieces recovered from PP Unit 3, no thermal conductivity measurements could be taken from this unit. Finally, PP Unit 4 shows values from 1.752 to 3.004 W/(m·K) that include the highest thermal conductivity measurements from the cores recovered at Site U1504.

Similarly, in Hole U1504B, PP Unit 2 has lower thermal conductivity values and no measurements could be taken in PP Unit 3. PP
Figure F36. Bulk density (GRA and MAD), dry density, grain density, and porosity, Hole U1504A. Note that in PP Units 3 and 4, the scattered GRA density measurements are less reliable due to void between core material and core liner. Descriptions and discussions in text are based on discrete samples of bulk density (MAD).

<figure><img src="image_436.png" /></figure>

Unit 4 is characterized by a regime of higher thermal conductivity with values ranging from 2.353 to 3.475 W/(m·K).

## Density and porosity

GRA densities generally match the trend of discrete bulk density values in PP Units 1 and 2 (Figure F35); however, the GRA density values are more scattered than the discrete measurements in PP Units 3 and 4 because whole-round measurements are affected by space between the core and the core liner. Hence, descriptions of variations in density are only based on discrete measurements of Hole U1504A (Figure F36).

In PP Unit 1, bulk density increases slightly with depth and ranges from ~1.4 to 1.5 g/cm³. Dry densities in the upper portion of Unit 1 (18–30 m) remain relatively constant with an average of ~0.7 g/cm³ followed by an increase to ~0.8 g/cm³ at ~38 m. Porosity ranges from 70% to 75% and displays a negative correlation with bulk density, as expected. Grain density values are relatively uniform, averaging ~2.7 g/cm³.

In PP Unit 2, bulk density gradually increases with depth from ~1.6 g/cm³ at 47 m to ~1.8 g/cm³ at 110 m. Dry density similarly increases with depth, whereas porosity decreases downcore from 67% to 57%. Grain density is relatively constant at ~2.7 g/cm³.

Bulk density values in PP Unit 3 are higher than in the overlying Unit 2, ranging from ~2.3 to 2.7 g/cm³ followed by a sharp shift toward higher values (>2.8 g/cm³) at the boundary with PP Unit 4 (Figure F36). PP Unit 4 (135–165.5 m) represents the metamorphic basement and is characterized by very high bulk density (>2.9 g/cm³). PP Unit 4 grain density increases downcore from ~2.9 to 3.0 g/cm³, whereas porosity ranges from 2% to 5%.

## Color reflectance spectrophotometry

In PP Unit 1, reflectance parameters L*, a*, and b* remain relatively constant with mean values of 42, 2, and -1, respectively (Figure F37). At the uppermost portion of PP Unit 2 in Hole U1504A,

all parameters display a large increase to 63, 9, and 17, respectively. Over the rest of Unit 2 (48–114 m in Hole U1504A), L* values slightly decrease from ~60 to 50, whereas a* and b* show comparable larger variations between 65 and 114 m. In PP Units 3 and 4 in both holes, L*, a*, and b* values are relatively scattered. Unit 3 has a mean L* value of ~45 similar to Unit 4 but higher mean a* and b* values of ~5 compared with that of approximately -1 in Unit 4.

## Magnetic susceptibility

Magnetic susceptibility shows very limited changes between ~5 × 10⁻⁵ and 80 × 10⁻⁵ SI throughout all four petrophysical units (Figure F35). Nevertheless, magnetic susceptibility differences between different units are still recognizable. PP Unit 1 has a relatively high mean magnetic susceptibility of ~30 × 10⁻⁵ SI compared with that of ~20 × 10⁻⁵ SI for PP Unit 2. Unit 2 also contains two depth intervals (~46.5–47.0 and 56.5–57.0 m in Hole U1504A) showing magnetic susceptibility as high as 80 × 10⁻⁵ SI. The distribution of magnetic susceptibility within PP Units 3 and 4 is scattered, possibly due to the fragmented core materials and voids within the rock core samples. The mean magnetic susceptibility is as low as ~10 × 10⁻⁵ SI in Unit 3 but increases to ~35 × 10⁻⁵ SI in Unit 4.

## RGB

In Hole U1504A, RGB values are generally constant with depth in PP Units 1, 3, and 4 with small variations (Figure F38), but Units 3 and 4 have higher values than Unit 1 because Unit 1 consists of dark gray nannofossil ooze (see Lithostratigraphy). PP Unit 2 is marked by strong RGB intensity that corresponds to carbonate-rich lithology. All the units in Hole U1504B have value ranges similar to those of the corresponding units in Hole U1504A.

## Discussion and summary

Core materials in PP Units 1 and 2 consist of soft sediments. In general, compared with Unit 2, Unit 1 has higher average NGR (~30
<figure><img src="image_437.png" /><figcaption>Figure F37. Core color reflectance parameters L*, a*, and b*, Holes U1504A and U1504B.</figcaption></figure>

versus 20 counts/s), weaker color reflectance (mean L* of ~40 versus 50), and lower average RGB values (100 versus 150) (Figures F35, F37, F38). These changes in physical properties between Units 1 and 2 correspond to a change in sediment compositions from nannofossil-rich clay to nannofossil ooze (see Lithostratigraphy). General increases in bulk (from ~1.4 to 1.8 g/cm³) and dry (from ~0.7 to 1.2 g/cm³) densities and a downhole decrease in porosity (from 75% to 56%) in Units 1 and 2 mainly indicate sediment compaction with time. The boundary between Units 1 and 2 is marked by a relatively rapid increase in P-wave velocity and bulk density and a rapid decrease in porosity compared with the general trends mentioned above (Figures F35, F36). This physical property boundary corresponds to a clear unconformity in the seismic profile along this drilling site and to a large hiatus (see Biostratigraphy).

P-wave velocity and bulk density increase from ~3800 to 5000 m/s and from ~2.4 to 2.9 g/cm³, respectively, within PP Unit 3, corresponding to a transition in lithology from coral-rich limestone to clast-supported limestone (see Lithostratigraphy). Coral-enriched limestone in the upper portion of Unit 3 is also associated with a moderately high porosity of ~23% (Figures F35, F36). PP Unit 4 is characterized by a uniformly high velocity of ~5500 m/s, high bulk

<figure><img src="image_438.png" /><figcaption>Figure F38. Core RGB values, Holes U1504A and U1504B.</figcaption></figure>

density of ~2.9 g/cm³, and low porosity of ~3%, all of which correspond to epidote-chlorite schist (see Lithostratigraphy). A large increase in both velocity and density at the boundaries between Units 2 and 3 and between Units 3 and 4 is also recorded by two strong positive seismic reflectors (Figure F36). The gradual downhole increase in thermal conductivity values at shallow depths is likely due to progressive compaction of the sediments. The higher RGB intensity in Unit 2 reflects the higher carbonate content.

## Correlation to seismic data

We conducted two sets of analyses to correlate the core measurements (in meters below seafloor) to the time-based seismic data from Hole U1504A. First, we analyzed core data and investigated correlation to the seismic reflection profile. Second, we constructed synthetic seismograms using the core data of Site U1504 and compared the results with the traces in seismic profiles. Preliminary calculations were done during the expedition using a combination of Matlab scripts and Petrel software.

### Velocity and density data and comparison with seismic reflectors

Whole-round core measurements were conducted in Hole U1504A from 17.5 to 163.5 m for GRA density and from 17.5 to 112.7 m for P-wave logger (PWL) measurements (Figure F39). P-wave velocity was also measured along the x-axis with the PWC system on working-half sections. MAD measurements were performed on discrete samples, one every other section. Wireline
<figure><img src="image_439.png" /><figcaption>Figure F39. Comparison of a subset of physical properties (magnetic susceptibility [MS], velocity, density, and NGR) with seismic waveform (converted to depth scale using best-fitting TDR model) and seismic image (in timescale) in Hole U1504A. Red circles = reference points (discussed in text).</figcaption></figure>

logging was not conducted at Site U1504. With the outliers filtered out, the whole-round PWL velocity and GRA density data show a good match with the PWC velocity and MAD density of core samples, respectively.

Although no downhole logging was conducted at Site U1504, two distinct changes in the physical property data from the cores helped in building a velocity model for the time-depth correlation on the seismic profiles from Hole U1504A. The first major change

in $V_p$ and density was identified at ~112.7 m, coinciding with the lithologic change from sediment to limestone (Figure F39; see Lithostratigraphy). We hypothesized that a relatively strong reflector in the seismic traces at Site U1504 (two-way traveltime [TWT] = 3922 ms) might correspond to the noticeable changes in lithology and physical properties at 112.7 m we refer to as reference Point RP1. A second major change in $V_p$ and density, at ~134.2 m, is associated with a strong peak in the seismogram (TWT = 3944 ms) des-
ignated as reference Point RP2. Once the corresponding depths of the two reference points were assigned, the interval velocity at the 112.7–134.2 m depth range was calculated to be ~2 km/s. For the 134.2–163.5 m interval, an interval velocity of 5094 m/s was chosen, which corresponds to the average PWC values.

## Time-depth relationship

Hole U1504A PWC data were used to calculate the time-depth relationship (TDR) model of seismic waves. We assigned the first strong reflector (TWT = 3922 ms; reference Point RP1) to be associated with the major changes in $V_p$ and density at ~112.7 m. Similarly, we assigned the second strong reflector (TWT = 3944 ms; reference Point RP2) to be associated with the major changes in $V_p$ and density at ~134.2 m. For the 134.2–163.5 interval, the TDR was calculated assuming an interval velocity of 5094 m/s, which is the average PWC for this interval (Figure F40).

## Synthetic seismograms

To further illustrate the relationship between the core measurements in Hole U1504A and the seismic reflection profile, the “Seismic interpretation” module in Petrel was used to compute synthetic seismograms based on the relevant core measurements (Figure F41). Synthetic traces were generated by convolving the reflectivity from the density of core samples, an interval velocity model, and with the source wavelet that best fit the seismic data (“Ricker 2;” Figure F41).

Seismic impedance (SI) of a rock layer is the product of its average seismic velocity ($V_p$) and density ($\rho$) (i.e., $SI = V_p \times \rho$). The seismic reflection coefficient, in turn, equals the change in the seismic impedance between two adjacent rock layers. Thus, we can expect greater amplitudes in the modeled seismogram for rock interfaces with larger values of reflection coefficient. The resulting synthetic seismogram shows two strong reflectors at ~110–142 m (Figure F41), consistent with the observed depth range of the two strong seismic reflectors.

Using the best-fitting TDR model for Hole U1504A (Figure F40), we were able to convert the depth scale to a timescale for all

Figure F40. A. Site U1504 time-depth relation curve in Hole U1504A compared to Site U1501. Red circles = reference points at 112.7 and 134.2 m (RP1 and RP2), coinciding with noticeable changes in density and velocity. B. Hole U1504A PWC and interval velocity model. Interval velocity for 112.7–134.2 m was calculated using TWT and depth range values of RP1 and RP2; interval velocity for 134.2–163.5 m corresponds to average PWC for that interval.

<figure><img src="image_440.png" /></figure>

core measurements. This conversion enabled us to display the core measurements directly on top of the time-based seismic sections, facilitating identification of correlated features as illustrated in the example of Figure F42.
<figure><img src="image_441.png" /><figcaption>Figure F41. Synthetic seismogram, Hole U1504A. Panels from left to right: interval velocity and MAD density used in the calculation, resultant reflection coefficient (RC), real seismic traces with synthetic seismogram inserted in the center, and seismic source function "Ricker 2" used in modeling.</figcaption></figure>
<figure><img src="image_442.png" /><figcaption>Figure F42. Seismic section at Site U1504 with lithostratigraphic units overlain at Hole U1504A location. Also shown are selected core measurements converted to depth scale using best-fitting TDR model, including Hole U1504A PWC and PWL, MAD density, GRA density, porosity, MS, and NGR.</figcaption></figure>

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## Site U1505¹

<figure><img src="image_443.png" /></figure>

Check for updates

Zhimin Jian, Hans Christian Larsen, Carlos A. Alvarez Zarikian, Zhen Sun, Joann M. Stock, Adam Klaus, Jacopo Boaga, Stephen A. Bowden, Anne Briais, Yifeng Chen, Deniz Cukur, Kelsie A. Dadd, Weiwei Ding, Michael J. Dorais, Eric C. Ferré, Fabricio Ferreira, Akira Furusawa, Aaron J. Gewecke, Jessica L. Hinojosa, Tobias W. Höfig, Kan-Hsi Hsiung, Baoqi Huang, Enqing Huang, Xiao-Long Huang, Shijun Jiang, Haiyan Jin, Benjamin G. Johnson, Robert M. Kurzawski, Chao Lei, Baohua Li, Li Li, Yanping Li, Jian Lin, Chang Liu, Chuanlian Liu, Zhifei Liu, Antonio Luna, Claudia Lupi, Anders J. McCarthy, Geoffroy Mohn, Lachit Singh Ningthoujam, Michael Nirrengarten, Nobuaki Osono, David W. Peate, Patricia Persaud, Ning Qiu, Caroline M. Robinson, Sara Satolli, Isabel Sauermilch, Julie C. Schindlbeck, Steven M. Skinner, Susanne M. Straub, Xiang Su, Liyan Tian, Froukje M. van der Zwan, Shiming Wan, Huaichun Wu, Rong Xiang, Rajeev Yadav, Liang Yi, Cuimei Zhang, Jinchang Zhang, Yang Zhang, Ning Zhao, Guangfa Zhong, and Lifeng Zhong<fnref n="2" />

**Keywords:** International Ocean Discovery Program, IODP, JOIDES Resolution, Expedition 367, Expedition 368, Site U1505, northern South China Sea, continent-ocean transition zone, outer margin high, hyperextension, continental breakup, thinning, rifting, T60 unconformity, Oligocene, high sedimentation rate, greigite

## Site summary

### Background and objectives

Site U1505 (proposed Site SCSI-3D; Sun et al., 2016) is located at 2916.6 m water depth on a broad regional basement high (Figure F1). This site was an alternate to Site U1501, should time be left for drilling following completion of the high-priority sites included in the *Scientific Prospectus* (Sun et al., 2016). Site U1505 was included in Expedition 368 because it might complement findings at Site U1501 and it was within the operational limits of 3400 m drill string imposed by the failure of the drawworks.

Both Sites U1505 and U1501 are located on the same structural high at similar water depths and are 10.5 km apart (Figure F2). The seismic section at Site U1505 generally shows a more horizontal orientation of the seismic reflectors and concordant relationship of the strata than the one at Site U1501, indicating the sediment sequence at Site U1505 should be more complete. The key objective at Site U1505 was to sample the stratigraphic record above seismic unconformity T80 (inferred before drilling to be ~38 Ma in age), and spe-

cific goals were to constrain both (1) the sediment responses to the tectonic events and basin evolution since the Eocene and (2) Neogene paleoceanographic and paleoclimatological changes along the northern South China Sea (SCS) margin.

The relatively shallow 2916.6 m water depth at Site U1505 makes it one of the few Ocean Drilling Program (ODP)/Integrated Ocean Drilling Program/International Ocean Discovery Program (IODP) sites above the modern carbonate compensation depth (CCD) of the SCS. The site's hemipelagic deposits, rich in calcareous microfossils, enable the application of stable isotopes, faunal analyses, and other multidisciplinary methods. Key objectives were to reconstruct the east Asian monsoonal climate record in the SCS and upper- and deep-water variations in the western Pacific. Site U1505 will, for the first time, provide an almost continuous sequence of paleoceanographic studies at orbital and millennial timescales since the late Eocene in the SCS. We cored two holes at this site with the advanced piston corer (APC) system to obtain a continuous record of the Pliocene-Pleistocene interval for high-resolution paleoceanographic studies.

## Contents

1. Site summary

5. Background and objectives

6. Operations

9. Lithostratigraphy

14. Structural geology

14. Biostratigraphy

19. Paleomagnetism

22. Geochemistry

27. Physical properties

31. Downhole measurements

34. Correlation to seismic data

38. References

<figure><img src="image_444.png" /></figure>

<footnote n="1">¹ Jian, Z., Larsen, H.C., Alvarez Zarikian, C.A., Sun, Z., Stock, J.M., Klaus, A., Boaga, J., Bowden, S.A., Briais, A., Chen, Y., Cukur, D., Dadd, K.A., Ding, W., Dorais, M.J., Ferré, E.C., Ferreira, F., Furusawa, A., Gewecke, A.J., Hinojosa, J.L., Höfig, T.W., Hsiung, K.-H., Huang, B., Huang, E., Huang, X.-L., Jiang, S., Jin, H., Johnson, B.G., Kurzawski, R.M., Lei, C., Li, B., Li, L., Li, Y., Lin, J., Liu, C., Liu, C., Liu, Z., Luna, A., Lupi, C., McCarthy, A.J., Mohn, G., Ningthoujam, L.S., Nirrengarten, M., Osono, N., Peate, D.W., Persaud, P., Qui, N., Robinson, C.M., Satolli, S., Sauermilch, I., Schindlbeck, J.C., Skinner, S.M., Straub, S.M., Su, X., Tian, L., van der Zwan, F.M., Wan, S., Wu, H., Xiang, R., Yadav, R., Yi, L., Zhang, C., Zhang, J., Zhang, Y., Zhao, N., Zhong, G., and Zhong, L., 2018. Site U1505. *In* Sun, Z., Jian, Z., Stock, J.M., Larsen, H.C., Klaus, A., Alvarez Zarikian, C.A., and the Expedition 367/368 Scientists. *South China Sea Rifted Margin*. Proceedings of the International Ocean Discovery Program, 367/368: College Station, TX (International Ocean Discovery Program). https://doi.org/10.14379/iodp.proc.367368.109.2018</footnote>

<footnote n="2">² *Expedition 367/368 Scientists' addresses.*</footnote>

<footnote>MS 367368-109: Published 28 September 2018</footnote>

<footnote>This work is distributed under the **Creative Commons Attribution 4.0 International** (CC BY 4.0) license.</footnote>
Figure F1. Bathymetry with seismic lines, Site U1505. Note that the site is not at the exact crossing of seismic lines 04ec1555 and 15ecLW1. Seismic profiles across Site U1505 are shown in Figures F5 and F6. Common depth point (CDP) numbers are shown along seismic lines.

<figure><img src="image_445.png" /></figure>

## Operations

Four holes were cored with the APC and extended core barrel (XCB) systems at Site U1505. In Hole U1505A (18°55.0560′N, 115°51.5369′E; 2916.6 m water depth), Core 1H misfired and recovered only 0.3 m. In Hole U1505B (18°55.0562′N, 115°51.5370′E; 2918.6 m water depth), a 3.23 m long mudline core was recovered for future education and outreach activities. Hole U1505C (18°55.0570′N, 115°51.5370′E; 2917.4 m water depth) was cored with the APC system to 317 m and then cored with the XCB system to 480.2 m, recovering 480.15 m (100%). Hole U1505D (18°55.0485′N, 115°51.5501′E; 2917.5 m water depth) was cored with the APC system to 184.5 m and recovered 191.43 m (104%). Downhole logging with a modified triple combination (triple combo) tool string was conducted in Hole U1505C from 341.2 m uphole. The maximum drilling depth of 480.2 m was determined by the possible maximum total length (3400 m) of drill string deployment.

## Lithostratigraphy

The sediment succession recovered at Site U1505 extends from the Oligocene to the Pleistocene. Two sedimentary units (I and II) were observed (Figure F3). Lithostratigraphic Unit I is dominated by nannofossil ooze with varying amounts of foraminifers and clay, as well as biogenic silica in the upper interval of the hole. Unit I is divided into three subunits (IA–IC). Subunit IA (Hole U1505C = 0.00–27.76 m) is composed of dark greenish gray and greenish gray biosiliceous-rich clay with nannofossils, nannofossil-rich clay with biogenic silica, and nannofossil-rich biosiliceous ooze with clay. The abundance of biogenic silica decreases downhole. A pinkish gray, ~6 cm thick, slightly fining upward ash layer occurs at 20.8 m (Hole U1505C), and ash pods were observed at 20.3 m in Hole U1505D. Subunit IB (Hole U1505C = 27.76–273.39 m) is composed of gray to brown nannofossil ooze with minor silty intervals. The color change

Figure F2. Bathymetric maps showing Expedition 367/368 sites (stars), and (A) regional and (B) local coverage of multichannel seismic reflection data and OBS data. Thick blue and red lines are key seismic lines used for planning of the drilling transect. A. Magnetic isochrons (orange lines) from Briais et al. (1993). B. Magnetic picks (orange squares) from the same reference, extracted from the Seton et al. (2014) compilation. Chron labels for the picks correspond to the old edge of the normal polarity intervals (see Ogg et al. [2016] timescale for ages). Orange square = Leg 184 Site 1148, yellow squares = Expedition 349 Sites U1432 and U1435.

<figure><img src="image_446.png" /></figure>

reflects the varying abundance of foraminifers and clay. Subunit IC (Hole U1505C = 273.39–403.79 m) is composed of gray, greenish gray, and light brownish gray clay-rich nannofossil ooze (with foraminifers) and foraminifer-rich nannofossil ooze with clay and minor amounts of nannofossil-rich clay. Unit II (Hole U1505C = 403.50–480.54 m) is dominated by dark greenish gray, well-consolidated silty clay and clayey silt (with nannofossils).

## Biostratigraphy

All core catcher samples from Holes U1505A–U1505C were analyzed for calcareous nannofossils, planktonic foraminifers, and diatoms. Additional samples were taken from intervals within the
<figure><img src="image_447.png" /><figcaption>Figure F3. Lithostratigraphic and biostratigraphic summary, Site U1505.</figcaption></figure>

working-half sections when necessary to refine the ages. Hole U1505D was not sampled continuously for biostratigraphic analyses because of time constraints at the end of the expedition, but the sequence recovered spans from the late Miocene to the present (Figure F3). Preservation of calcareous microfossils is good in Cores 368-U1505C-1H through 48X and moderate to poor in Cores 49X through 64X. Planktonic foraminifers are abundant or common in Cores 1H through 56X and 59X through 62X and rare in Cores 57X,

58X, 63X, and 64X. Calcareous nannofossils are generally abundant to common in most samples from Hole U1505C, except for those from the upper part of Core 57X.

Forty-five biostratigraphic datums identified in Hole U1505C suggest a continuous succession from the early Oligocene to the Holocene (Figure F3). The Pleistocene/Pliocene boundary is placed within Core 7H, the Pliocene/Miocene boundary is placed between Cores 11H and 13H, and the Miocene/Oligocene boundary is
<figure><img src="image_448.png" /><figcaption>Figure F4. Data characterizing chemical anomalies associated with the T60 regional seismic marker, Site U1505.</figcaption></figure>

placed between Cores 54X and 55X. Sedimentation rates are ~7 mm/ky in the Oligocene, ~15 mm/ky during the Miocene-Pliocene, and ~24 mm/ky during the Pleistocene.

Relatively low abundances of planktonic foraminifers deeper than Core 57X indicate bathyal depths during the early Oligocene, whereas much higher abundances of planktonic foraminifers shallower than Core 56X suggest a deeper water environment since the late Oligocene.

## Paleomagnetism

Only natural remanent magnetization (NRM) was measured with the superconducting rock magnetometer (SRM) in Hole U1505C, except for Sections 1H-1 through 3H-1, which were in-line alternating field (AF) demagnetized in three steps. Most of the 55 AF demagnetized discrete samples show very soft magnetic behavior responsible for the acquisition of a strong, vertical drilling overprint (average inclination = ~81°) that was removed by demagnetization to 10–15 mT. This soft behavior shows that magnetic remanence is dominated by multidomain to pseudosingle-domain titanomagnetite or magnetite. The drilling overprint appears to impact discrete samples far less than core sections (Figure F19). The lower part of the hole (Cores 48X through 64X) is characterized by severe drilling disturbance, which causes a large scatter of NRM directions and inclinations.

Magnetostatigraphic data are based on polarities assigned to the archive-half sections and corroborated by directions obtained from oriented discrete samples. The lower boundary of the Brunhes (C1n) normal chron is at 37.4 m (0.781 Ma). The lower boundary (57.4 m) of the reverse polarity r1 is the base of Subchron C1r.3r with an age of 1.778 Ma.

## Geochemistry

Low but measurable hydrocarbon gases were detected only in Cores 368-U1505C-53X through 60X (371–438 m). The base of the hole has methane distributions similar to those at Site U1499, whereas the uppermost section is barren of methane, similar to Site U1501. Except for the shallowest 30 m of sediment, total organic carbon (TOC), total nitrogen (TN), and total sulfur (TS) contents are mostly low in lithostratigraphic Unit I, but TS and TOC are slightly higher in Unit II; however, in all cases they are typically <1 wt% (Figure F4). Interstitial water chemistry has two important features. The upper part of the hole exhibits patterns similar to those at Site U1501; inhibited sulfate reduction and low chlorine, bromine, and salinity suggest the presence of freshwater at depth. Freshwater at >400 m coincides with the presence of low quantities of methane and the T60 regional seismic unconformity.

## Physical properties and downhole measurements

Physical property data were acquired from cores from Holes U1505C (0–480.5 m) and U1505D (0–184 m), including density, magnetic susceptibility, P-wave velocity, natural gamma radiation (NGR), color reflectance, and thermal conductivity. Physical property trends allow us to define two physical property units, PP Units 1 (0–403 m) and 2 (403–480 m). The boundary between Units 1 and 2 displays a distinct color change from greenish and light brownish gray to dark greenish gray. This boundary, which corresponds to the seismic stratigraphic T60 unconformity, is associated with a sharp change in physical properties. In Unit 1, sediments in the upper part are composed of foraminifer-rich nannofossil ooze with clay that gradually changes to clay-rich nannofossil ooze in the lower part.
This change is well reflected in the NGR, which increases with depth. The higher NGR values in Unit 2 are related to sediment that primarily consists of silty clay. Magnetic susceptibility values overall gradually decrease with depth. The boundary between Units 1 and 2 shows that density and P-wave velocity values drop sharply from ~2.2 to ~1.8 g/cm³ and from ~2250 to 1750 m/s, respectively. Porosity values abruptly increase from ~35% to ~50%. Thermal conductivity also shows a sharp change at the boundary. Reflectance parameters L* and red, green, blue (RGB) data are well correlated with carbonate content.

Wireline logging was conducted in Hole U1505C using the triple combo tool string, which included the Hostile Environment Natural Gamma Ray Sonde (HNGS), Hostile Environment Litho-Density Sonde (HLDS), Dipole Sonic Imager (DSI), and magnetic susceptibility sonde (MSS). This logging string collected good data from 341.2 m (139.1 m above the bottom of Hole U1505C), which allows the definition of six logging units that mostly correlate with the lithostratigraphic units and core physical property data. Logging Unit 1 extends from the seafloor to the base of the drill pipe at 78 m. NGR is highly attenuated inside the drill pipe. Logging Unit 2 (base of the drill pipe to 96 m) exhibits NGR values that are ~50% lower than the underlying logging Unit 3. In Unit 3 (96–136 m), NGR increases with depth. Logging Unit 4 (136–220 m) exhibits relatively constant $V_p$ and $V_s$. In logging Unit 5 (200–296 m), resistivity increases with depth, whereas most of the other physical properties are relatively constant. Logging Unit 6 (296–341.2 m) has higher magnetic susceptibility values than logging Unit 5.

Four downhole temperature measurements were conducted in Hole U1505C using the advanced piston corer temperature tool (APCT-3). The temperature values range from 4.7°C at 36.7 m to 11.7°C at 122.8 m, giving a geothermal gradient of 84.6°C/km. A heat flow of 94.0 mW/m² was obtained from the linear fit between temperature and thermal resistance. The geothermal gradient and heat flow at Site U1505 are comparable to the relatively high values observed in a number of ODP and IODP sites in this part of the SCS.

## Background and objectives

Site U1505 is located at a water depth of 2917.4 m on a broad, regional basement high named the outer margin high (OMH) (Figure F1). This site was an alternate for Site U1501, should time be left for drilling following completion of the high-priority sites included in the *Scientific Prospectus*. Both Sites U1505 and U1501 are located on the same structural high at similar water depths and are only 10.46 km apart (Figure F2), so the two sites should have similar tectonic backgrounds and scientific objectives. The acoustic basement at Site U1501 consists of highly lithified sandstones and conglomerate, most likely of pre-Cenozoic age. However, the main target for Site U1505 was not the nature of the basement but the sediments within the small Cenozoic half-graben basins present on the OMH. According to the seismic profiles, the sediment sequences at the two sites should be similar to each other and the sedimentation rates should be suitable for high-resolution paleoceanographic and paleoenvironmental reconstructions. The seismic reflectors (Figures F5, F6) at Site U1505 are more distinctive and in general show a more horizontal orientation and concordant relationship of the strata, indicating the sediment sequence here would be more complete. Therefore, Site U1505 was selected for occupation following the failure to drill down below the cased hole at Site U1503 and the depth limit of 3400 m (water depth plus penetration) imposed by

the mechanical failure of the drilling equipment (see **Operations** in the Site U1503 chapter [Larsen et al., 2018b]).

Site U1505 is located near the crossing of seismic Lines 04ec1555 and 15ec1LW1 (Figure F1). The predrilling interpretation of the seismic unconformities (T30 to T83 and Tg reflector; see the **Expedition 367/368 methods** chapter [Sun et al., 2018]) around Site U1505 is shown in Figures F5 and F6. Using the velocity model (see **Physical properties** and **Correlation to seismic data**), the sedimentary sequence overlying the acoustic basement is ~1220 m thick. Because of the 3400 m depth limit, the maximum targeted drill depth at Site U1505 was 480 mbsf. The key objective at Site U1505 was to sample the stratigraphic record representing all stages since the T80 unconformity (including prerift sediments through synrift to postrift fill). The specific goal was to constrain the sediment responses to the tectonic events and basin evolution since the Eocene, as well as the Neogene paleoceanographic and paleoclimatological changes at the SCS northern margin.

Sampling sediments from the T80 unconformity (38.0 Ma; inferred age before drilling) to the T60 unconformity (23.0 Ma; in-

Figure F5. Site U1505 location and penetration depth on seismic dip Line 15ecLW1 (original predrilling interpretation). Seismic stratigraphic T30 (5.3 Ma), T32 (10.0 Ma), T50 (19.1 Ma), T60 (23.0 Ma), T80 (38.0 Ma), T82 (unknown age), and T83 (unknown age) unconformities and acoustic basement Tg reflector are shown (for inferred predrilling ages, see Seismic stratigraphic framework in the Expedition 367/368 methods chapter [Sun et al., 2018]).

<figure><img src="image_449.png" /></figure>
Figure F6. Site U1505 seismic strike location and penetration depth on Line 04ec1555 (original and predrilling interpretation). See Figure F5 for description of seismic interpretations. Dashed lines = unconformities, red solid lines = faults.

<figure><img src="image_450.png" /></figure>

ferred age before drilling) will help us determine the environment
before the SCS ocean basin formed, particularly the history of pale-
owater depth changes from shallow water to deep sea. The basin-
wide T60 unconformity is a strong negative reflector showing con-
formable relationships below and above Site U1505. The nature of
this profound reflector is an important objective together with the
post-T60 stratigraphic interval, which is also expected to provide
information to constrain the rate of thermal subsidence following
initial tectonic subsidence recorded within the Eocene to early Oli-
gocene sediments.

The younger stratigraphy above the T60 unconformity is the fo-
cus of the Neogene environmental development of the SCS and ad-
jacent landmasses of Southeast Asia. The relatively shallow water
depth of 2916.6 m at Site U1505 makes it one of the few ODP/IODP
sites above the modern CCD of the SCS. Its hemipelagic deposits
rich in calcareous microfossils enable the application of stable iso-
topes, faunal analyses, and other multidisciplinary methods. Key
objectives of this interval sampled by a number of ODP/IODP sites
are reconstruction of (1) the East Asian monsoonal climate changes
of the SCS and surrounding land and (2) upper and deep-water vari-
ations in the western Pacific. For the first time, Site U1505 will un-
derpin an almost continuous oxygen isotope sequence at the orbital

and millennial timescales since the late Eocene in the SCS. To
achieve this goal, relatively complete sediment sequences are re-
quired. Double APC holes were designed at this site to establish a
continuous record of the Pliocene to Pleistocene interval for high-
resolution paleoceanographic study.

Operations

Four holes were cored at Site U1505 (Table T1) using the APC and XCB systems with the objective of recovering a complete sedimentary succession from the early Miocene to Holocene that can supplement the interval sampled at Site U1501 for postexpedition paleoceanographic and paleoclimatological studies. In Hole U1505A (18°55.0560′N, 115°51.5369′E; 2916.6 m water depth), Core 1H misfired (shear pins) and recovered only 0.3 m. In Hole U1505B (18°55.0562′N, 115°51.5370′E; 2918.6 m water depth), Core 1H penetrated 3 m into the seafloor, recovering 3.23 m (107%). With a good mudline core, the hole was terminated. Hole U1505C (18°55.0570′N, 115°51.5370′E; 2917.4 m water depth) was cored to 480.2 m, recovering 480.15 m (100%). Hole U1505D (18°55.0485′N, 115°51.5501′E; 2917.5 m water depth) was cored to 184.5 m, recovering 191.43 m (104%). Downhole logging with a modified triple combo tool was conducted in Hole U1505C.

Transit to Site U1505

The R/V *JOIDES Resolution* began the transit from Site U1504 to Site U1505 at 1854 h on 28 May 2017 and arrived on site at 2112 h the same day. The thrusters were lowered, and the heading was controlled at 2148 h, beginning operations at Site U1505.

Holes U1505A and U1505B

An APC/XCB bottom-hole assembly (BHA) was made up, and a
precision depth recorder (PDR) measurement was taken to help de-
termine the seafloor depth. As the drill string was being lowered to
the seafloor, we deployed the subsea camera system to observe the
end of the pipe tag the seafloor. APC coring started in Hole U1505A
at 0545 h on 29 May 2017 at a water depth of 2916.6 m. With the bit
at 2911.2 m, the core barrel was recovered to the surface after an
apparent misfire (failed shear pins) of the APC. The barrel had 0.38
m of core, far less than anticipated, and the hole was terminated at
1200 h to attempt a better mudline.

The bit was spaced out to 2912.1 m below sea level (mblsl), and
coring in Hole U1505B started at 1235 h on 29 May. The core was
recovered with 3.23 m of sediment. With a good mudline core, Hole
U1505B was terminated at 1300 h.

Hole U1505C

The vessel was offset 20 m east, and the bit was spaced out to
2916.1 mblsl. Because of a leak in the newly replaced low clutch dia-
phragm, the decision was made to core with the APC system and
then core with the XCB system to refusal or to the maximum drill
string weight that could be lifted using the high clutch (whichever
came first). Hole U1505C (18°55.0570′N, 115°51.5370′E) was
started at 1340 h on 29 May 2017. Seafloor was calculated at 2917.4
mblsl based on recovery from Core 1H. The full-length APC system
was used to refusal at 207.1 m with APCT-3 temperature measure-
ments taken on Cores 4H, 7H, 10H, and 13H. All four deployments
produced good temperature data. APC refusal was determined after
partial strokes on five consecutive cores, beginning with Core 19H
and continuing through Core 23H. The half-length APC (HLAPC)
system was then deployed and used to recover Cores 24F through
<table><caption>Table T1. Site U1505 core summary. DRF = drilling depth below rig floor, DSF = drilling depth below seafloor. NA = not applicable. Core type: H = advanced piston corer (APC), F = half-length APC, XCB = extended core barrel. APCT-3 = advanced piston corer temperature tool. (Continued on next page.) Download available in CSV format.</caption><thead><tr><th>Core</th><th>Type</th><th>Top of interval DSF (m)</th><th>Bottom of interval DSF (m)</th><th>Interval advanced (m)</th><th>Core recovered length (m)</th><th>Curated length (m)</th><th>Recovery (%)</th><th>Time on deck UTC (h)</th><th>Time to cut core (min)</th><th>Core barrel</th><th>Mud pumped (bbl)</th><th>Driller's notes</th></tr></thead><tbody><tr><td colspan="13"><strong>Hole U1505A</strong></td></tr><tr><td>Latitude:</td><td></td><td>18°55.0506'N</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Longitude:</td><td></td><td>115°51.5369'E</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Seafloor (drill pipe measurement below rig floor, m DRF):</td><td></td><td>2916.57</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Time on hole (days):</td><td></td><td>0.59</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total depth (drill pipe measurement from rig floor, m DRF):</td><td></td><td>2928</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Distance between rig floor and sea level (m):</td><td></td><td>11.43</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total penetration (drilling depth below seafloor, m DSF):</td><td></td><td>0.3</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total length of cored section (m):</td><td></td><td>0.3</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total core recovered (m):</td><td></td><td>0.38</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Core recovery (%):</td><td></td><td>126.67</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Drilled interval (m):</td><td></td><td>NA</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total cores (no.):</td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td colspan="13"><strong>Hole U1505B</strong></td></tr><tr><td>Latitude:</td><td></td><td>18°55.0562'N</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Longitude:</td><td></td><td>115°51.5370'E</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Seafloor (drill pipe measurement below rig floor, m DRF):</td><td></td><td>2918.57</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Time on hole (days):</td><td></td><td>0.04</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total depth (drill pipe measurement from rig floor, m DRF):</td><td></td><td>2930</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Distance between rig floor and sea level (m):</td><td></td><td>11.43</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total penetration (drilling depth below seafloor, m DSF):</td><td></td><td>3</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total length of cored section (m):</td><td></td><td>3</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total core recovered (m):</td><td></td><td>3.23</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Core recovery (%):</td><td></td><td>107.67</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Drilled interval (m):</td><td></td><td>NA</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total cores (no.):</td><td></td><td>1</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td colspan="13"><strong>Hole U1505C</strong></td></tr><tr><td>Latitude:</td><td></td><td>18°55.0570'N</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Longitude:</td><td></td><td>115°51.5491'E</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Seafloor (drill pipe measurement below rig floor, m DRF):</td><td></td><td>2917.37</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Time on hole (days):</td><td></td><td>4.29</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total depth (drill pipe measurement from rig floor, m DRF):</td><td></td><td>2928.8</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Distance between rig floor and sea level (m):</td><td></td><td>11.43</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total penetration (drilling depth below seafloor, m DSF):</td><td></td><td>480.2</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total length of cored section (m):</td><td></td><td>480.2</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total core recovered (m):</td><td></td><td>480.15</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Core recovery (%):</td><td></td><td>99.99</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Drilled interval (m):</td><td></td><td>NA</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Total cores (no.):</td><td></td><td>64</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr></tbody></table>

<table><thead><tr><th>Core</th><th>Type</th><th>Top of interval DSF (m)</th><th>Bottom of interval DSF (m)</th><th>Interval advanced (m)</th><th>Core recovered length (m)</th><th>Curated length (m)</th><th>Recovery (%)</th><th>Time on deck UTC (h)</th><th>Time to cut core (min)</th><th>Core barrel</th><th>Mud pumped (bbl)</th><th>Driller's notes</th></tr></thead><tbody><tr><td colspan="13"><strong>368-U1505A</strong></td></tr><tr><td>1</td><td>H</td><td>0</td><td>0.3</td><td>0.3</td><td>0.38</td><td>0.38</td><td>127</td><td>5/29/2017 03:40</td><td></td><td></td><td></td><td></td></tr><tr><td></td><td></td><td colspan="6">Hole U1505A totals:</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td></td><td></td><td></td><td></td><td></td><td>0.3</td><td>0.38</td><td>127</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td colspan="13"><strong>368-U1505B</strong></td></tr><tr><td>1</td><td>H</td><td>0</td><td>3</td><td>3</td><td>3.23</td><td>3.23</td><td>108</td><td>5/29/2017 04:55</td><td></td><td></td><td></td><td></td></tr><tr><td></td><td></td><td colspan="6">Hole U1505B totals:</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td colspan="13"><strong>368-U1505C</strong></td></tr><tr><td>1</td><td>H</td><td>0</td><td>8.2</td><td>8.2</td><td>8.23</td><td>8.23</td><td>100</td><td>5/29/2017 06:05</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>2</td><td>H</td><td>8.2</td><td>17.7</td><td>9.5</td><td>9.54</td><td>9.54</td><td>100</td><td>5/29/2017 07:05</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>3</td><td>H</td><td>17.7</td><td>27.2</td><td>9.5</td><td>8.34</td><td>8.34</td><td>88</td><td>5/29/2017 08:05</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>4</td><td>H</td><td>27.2</td><td>36.7</td><td>9.5</td><td>9.97</td><td>9.97</td><td>105</td><td>5/29/2017 09:10</td><td>Nonmagnetic</td><td></td><td>APCT-3</td><td></td></tr><tr><td>5</td><td>H</td><td>36.7</td><td>46.2</td><td>9.5</td><td>9.81</td><td>9.81</td><td>103</td><td>5/29/2017 10:10</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>6</td><td>H</td><td>46.2</td><td>55.7</td><td>9.5</td><td>10.03</td><td>10.03</td><td>106</td><td>5/29/2017 11:10</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>7</td><td>H</td><td>55.7</td><td>65.2</td><td>9.5</td><td>10</td><td>10</td><td>105</td><td>5/29/2017 12:15</td><td>Nonmagnetic</td><td></td><td>APCT-3</td><td></td></tr><tr><td>8</td><td>H</td><td>65.2</td><td>74.7</td><td>9.5</td><td>9.75</td><td>9.75</td><td>103</td><td>5/29/2017 13:15</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>9</td><td>H</td><td>74.7</td><td>84.2</td><td>9.5</td><td>9.48</td><td>9.48</td><td>100</td><td>5/29/2017 14:10</td><td>Nonmagnetic</td><td></td><td>APCT-3</td><td></td></tr><tr><td>10</td><td>H</td><td>84.2</td><td>93.7</td><td>9.5</td><td>9.45</td><td>9.45</td><td>99</td><td>5/29/2017 15:25</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>11</td><td>H</td><td>93.7</td><td>103.2</td><td>9.5</td><td>9.08</td><td>9.08</td><td>96</td><td>5/29/2017 16:25</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>12</td><td>H</td><td>103.2</td><td>112.7</td><td>9.5</td><td>8.53</td><td>8.53</td><td>90</td><td>5/29/2017 17:20</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>13</td><td>H</td><td>112.7</td><td>122.2</td><td>9.5</td><td>10.01</td><td>10.01</td><td>105</td><td>5/29/2017 18:35</td><td>Nonmagnetic</td><td></td><td>APCT-3</td><td></td></tr><tr><td>14</td><td>H</td><td>122.2</td><td>131.7</td><td>9.5</td><td>10.03</td><td>10.03</td><td>106</td><td>5/29/2017 19:30</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>15</td><td>H</td><td>131.7</td><td>141.2</td><td>9.5</td><td>9.62</td><td>9.62</td><td>101</td><td>5/29/2017 20:35</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>16</td><td>H</td><td>141.2</td><td>150.7</td><td>9.5</td><td>9.7</td><td>9.7</td><td>102</td><td>5/29/2017 21:25</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>17</td><td>H</td><td>150.7</td><td>160.2</td><td>9.5</td><td>9.97</td><td>9.97</td><td>105</td><td>5/29/2017 22:25</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>18</td><td>H</td><td>160.2</td><td>169.7</td><td>9.5</td><td>10.08</td><td>10.08</td><td>106</td><td>5/29/2017 23:30</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>19</td><td>H</td><td>169.7</td><td>179.2</td><td>9.5</td><td>10.05</td><td>10.05</td><td>106</td><td>5/30/2017 00:25</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>20</td><td>H</td><td>179.2</td><td>188.7</td><td>9.5</td><td>10.06</td><td>10.06</td><td>106</td><td>5/30/2017 01:20</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>21</td><td>H</td><td>188.7</td><td>196.7</td><td>8</td><td>7.83</td><td>7.83</td><td>98</td><td>5/30/2017 02:10</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>22</td><td>H</td><td>196.7</td><td>203.1</td><td>6.4</td><td>3.36</td><td>3.36</td><td>53</td><td>5/30/2017 03:05</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>23</td><td>H</td><td>203.1</td><td>207.1</td><td>4</td><td>3.95</td><td>3.95</td><td>99</td><td>5/30/2017 03:55</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>24</td><td>F</td><td>207.1</td><td>211.8</td><td>4.7</td><td>5.08</td><td>5.08</td><td>108</td><td>5/30/2017 05:15</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>25</td><td>F</td><td>211.8</td><td>216.5</td><td>4.7</td><td>5.12</td><td>5.12</td><td>109</td><td>5/30/2017 06:10</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>26</td><td>F</td><td>216.5</td><td>221.2</td><td>4.7</td><td>5.04</td><td>5.04</td><td>107</td><td>5/30/2017 07:00</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>27</td><td>F</td><td>221.2</td><td>225.9</td><td>4.7</td><td>5.13</td><td>5.13</td><td>109</td><td>5/30/2017 08:05</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>28</td><td>F</td><td>225.9</td><td>230.6</td><td>4.7</td><td>5.03</td><td>5.03</td><td>107</td><td>5/30/2017 09:00</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>29</td><td>F</td><td>230.6</td><td>235.3</td><td>4.7</td><td>5.09</td><td>5.09</td><td>108</td><td>5/30/2017 09:45</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr><tr><td>30</td><td>F</td><td>235.3</td><td>240</td><td>4.7</td><td>5.02</td><td>5.02</td><td>107</td><td>5/30/2017 11:10</td><td>Nonmagnetic</td><td></td><td></td><td></td></tr></tbody></table>
<table><caption>Table T1 (continued).</caption><thead><tr><th>Core</th><th>Type</th><th>Top of interval DSF (m)</th><th>Bottom of interval DSF (m)</th><th>Interval advanced (m)</th><th>Core recovered length (m)</th><th>Curated length (m)</th><th>Recovery (%)</th><th>Time on deck UTC (h)</th><th>Time to cut core (min)</th><th>Core barrel</th><th>Mud pumped (bbl)</th><th>Driller's notes</th></tr></thead><tbody><tr><td>31</td><td>F</td><td>240</td><td>244.7</td><td>4.7</td><td>5.02</td><td>5.02</td><td>107</td><td>5/30/2017 11:55</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>32</td><td>F</td><td>244.7</td><td>249.4</td><td>4.7</td><td>5.04</td><td>5.04</td><td>107</td><td>5/30/2017 12:50</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>33</td><td>F</td><td>249.4</td><td>254.1</td><td>4.7</td><td>5.06</td><td>5.06</td><td>108</td><td>5/30/2017 13:45</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>34</td><td>F</td><td>254.1</td><td>258.8</td><td>4.7</td><td>5.07</td><td>5.07</td><td>108</td><td>5/30/2017 14:40</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>35</td><td>F</td><td>258.8</td><td>263.5</td><td>4.7</td><td>5.03</td><td>5.03</td><td>107</td><td>5/30/2017 15:35</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>36</td><td>F</td><td>263.5</td><td>268.2</td><td>4.7</td><td>5.03</td><td>5.03</td><td>107</td><td>5/30/2017 16:30</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>37</td><td>F</td><td>268.2</td><td>272.9</td><td>4.7</td><td>4.81</td><td>4.81</td><td>102</td><td>5/30/2017 17:20</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>38</td><td>F</td><td>272.9</td><td>277.6</td><td>4.7</td><td>5.05</td><td>5.05</td><td>107</td><td>5/30/2017 18:10</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>39</td><td>F</td><td>277.6</td><td>279.4</td><td>1.8</td><td>1.8</td><td>1.8</td><td>100</td><td>5/30/2017 20:00</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>40</td><td>F</td><td>279.4</td><td>284.1</td><td>4.7</td><td>5.04</td><td>5.04</td><td>107</td><td>5/30/2017 21:30</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>41</td><td>F</td><td>284.1</td><td>288.8</td><td>4.7</td><td>4.91</td><td>4.91</td><td>104</td><td>5/30/2017 22:30</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>42</td><td>F</td><td>288.8</td><td>293.5</td><td>4.7</td><td>5.03</td><td>5.03</td><td>107</td><td>5/30/2017 23:15</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>43</td><td>F</td><td>293.5</td><td>298.2</td><td>4.7</td><td>4.72</td><td>4.72</td><td>100</td><td>5/30/2017 00:00</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>44</td><td>F</td><td>298.2</td><td>302.9</td><td>4.7</td><td>5.01</td><td>5.01</td><td>107</td><td>5/31/2017 00:50</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>45</td><td>F</td><td>302.9</td><td>307.6</td><td>4.7</td><td>5.02</td><td>5.02</td><td>107</td><td>5/31/2017 01:40</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>46</td><td>F</td><td>307.6</td><td>312.3</td><td>4.7</td><td>3.14</td><td>3.14</td><td>67</td><td>5/31/2017 02:40</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>47</td><td>F</td><td>312.3</td><td>317</td><td>4.7</td><td>2.6</td><td>2.6</td><td>55</td><td>5/31/2017 03:35</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>48</td><td>X</td><td>317</td><td>326.8</td><td>9.8</td><td>9.93</td><td>9.93</td><td>101</td><td>5/31/2017 05:55</td><td></td><td></td><td></td><td></td></tr><tr><td>49</td><td>X</td><td>326.8</td><td>336.5</td><td>9.7</td><td>9.9</td><td>9.9</td><td>102</td><td>5/31/2017 08:15</td><td></td><td></td><td></td><td></td></tr><tr><td>50</td><td>X</td><td>336.5</td><td>346.1</td><td>9.6</td><td>9.62</td><td>9.62</td><td>100</td><td>5/31/2017 10:25</td><td></td><td></td><td></td><td></td></tr><tr><td>51</td><td>X</td><td>346.1</td><td>355.6</td><td>9.5</td><td>9.87</td><td>9.87</td><td>104</td><td>5/31/2017 13:20</td><td></td><td></td><td></td><td></td></tr><tr><td>52</td><td>X</td><td>355.6</td><td>365.2</td><td>9.6</td><td>9.38</td><td>9.38</td><td>98</td><td>5/31/2017 16:10</td><td></td><td></td><td></td><td></td></tr><tr><td>53</td><td>X</td><td>365.2</td><td>374.7</td><td>9.5</td><td>9.35</td><td>9.35</td><td>98</td><td>5/31/2017 18:15</td><td></td><td></td><td></td><td></td></tr><tr><td>54</td><td>X</td><td>374.7</td><td>384.3</td><td>9.6</td><td>9.23</td><td>9.23</td><td>96</td><td>5/31/2017 20:40</td><td></td><td></td><td></td><td></td></tr><tr><td>55</td><td>X</td><td>384.3</td><td>393.9</td><td>9.6</td><td>9.81</td><td>9.81</td><td>102</td><td>5/31/2017 23:10</td><td></td><td></td><td></td><td></td></tr><tr><td>56</td><td>X</td><td>393.9</td><td>403.5</td><td>9.6</td><td>9.94</td><td>9.94</td><td>104</td><td>6/1/2017 01:45</td><td></td><td></td><td></td><td></td></tr><tr><td>57</td><td>X</td><td>403.5</td><td>413.2</td><td>9.7</td><td>9.99</td><td>9.99</td><td>103</td><td>6/1/2017 03:40</td><td></td><td></td><td></td><td></td></tr><tr><td>58</td><td>X</td><td>413.2</td><td>422.8</td><td>9.6</td><td>6.38</td><td>6.38</td><td>66</td><td>6/1/2017 06:15</td><td></td><td></td><td></td><td></td></tr><tr><td>59</td><td>X</td><td>422.8</td><td>432.4</td><td>9.6</td><td>7.46</td><td>7.46</td><td>78</td><td>6/1/2017 09:40</td><td></td><td></td><td></td><td></td></tr><tr><td>60</td><td>X</td><td>432.4</td><td>442</td><td>9.6</td><td>9.91</td><td>9.91</td><td>103</td><td>6/1/2017 12:45</td><td></td><td></td><td></td><td></td></tr><tr><td>61</td><td>X</td><td>442</td><td>451.6</td><td>9.6</td><td>9.93</td><td>9.93</td><td>103</td><td>6/1/2017 15:20</td><td></td><td></td><td></td><td></td></tr><tr><td>62</td><td>X</td><td>451.6</td><td>461.1</td><td>9.5</td><td>9.86</td><td>9.89</td><td>104</td><td>6/1/2017 17:40</td><td></td><td></td><td></td><td></td></tr><tr><td>63</td><td>X</td><td>461.1</td><td>470.7</td><td>9.6</td><td>9.99</td><td>9.99</td><td>104</td><td>6/1/2017 20:00</td><td></td><td></td><td></td><td></td></tr><tr><td>64</td><td>X</td><td>470.7</td><td>480.2</td><td>9.5</td><td>9.84</td><td>9.84</td><td>104</td><td>6/1/2017 22:30</td><td></td><td></td><td></td><td></td></tr><tr><td></td><td></td><td colspan="3">Hole U1505C totals: 480.2</td><td colspan="2">480.15</td><td colspan="2">480.15</td><td colspan="3"></td><td></td><td></td></tr><tr><td>368-U1505D-</td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>1</td><td>H</td><td>0</td><td>4</td><td>4</td><td>3.95</td><td>3.95</td><td>99</td><td>6/2/2017 14:20</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>2</td><td>H</td><td>4</td><td>13.5</td><td>9.5</td><td>9.62</td><td>9.62</td><td>101</td><td>6/2/2017 15:15</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>3</td><td>H</td><td>13.5</td><td>23</td><td>9.5</td><td>9.78</td><td>9.78</td><td>103</td><td>6/2/2017 16:20</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>4</td><td>H</td><td>23</td><td>32.5</td><td>9.5</td><td>9.8</td><td>9.8</td><td>103</td><td>6/2/2017 17:35</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>5</td><td>H</td><td>32.5</td><td>42</td><td>9.5</td><td>9.92</td><td>9.92</td><td>104</td><td>6/2/2017 18:25</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>6</td><td>H</td><td>42</td><td>51.5</td><td>9.5</td><td>9.91</td><td>9.91</td><td>104</td><td>6/2/2017 19:20</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>7</td><td>H</td><td>51.5</td><td>61</td><td>9.5</td><td>10.01</td><td>10.01</td><td>105</td><td>6/2/2017 20:15</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>8</td><td>H</td><td>61</td><td>70.5</td><td>9.5</td><td>9.98</td><td>9.98</td><td>105</td><td>6/2/2017 21:10</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>9</td><td>H</td><td>70.5</td><td>80</td><td>9.5</td><td>9.91</td><td>9.91</td><td>104</td><td>6/2/2017 22:10</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>10</td><td>H</td><td>80</td><td>89.5</td><td>9.5</td><td>9.84</td><td>9.84</td><td>104</td><td>6/2/2017 23:05</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>11</td><td>H</td><td>89.5</td><td>99</td><td>9.5</td><td>10.1</td><td>10.1</td><td>106</td><td>6/2/2017 23:55</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>12</td><td>H</td><td>99</td><td>108.5</td><td>9.5</td><td>9.94</td><td>9.94</td><td>105</td><td>6/3/2017 00:45</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>13</td><td>H</td><td>108.5</td><td>118</td><td>9.5</td><td>9.78</td><td>9.78</td><td>103</td><td>6/3/2017 01:35</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>14</td><td>H</td><td>118</td><td>127.5</td><td>9.5</td><td>9.82</td><td>9.82</td><td>103</td><td>6/3/2017 02:25</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>15</td><td>H</td><td>127.5</td><td>137</td><td>9.5</td><td>9.17</td><td>9.17</td><td>97</td><td>6/3/2017 03:20</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>16</td><td>H</td><td>137</td><td>146.5</td><td>9.5</td><td>10.1</td><td>10.1</td><td>106</td><td>6/3/2017 04:10</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>17</td><td>H</td><td>146.5</td><td>156</td><td>9.5</td><td>9.66</td><td>9.66</td><td>102</td><td>6/3/2017 05:10</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>18</td><td>H</td><td>156</td><td>165.5</td><td>9.5</td><td>10.14</td><td>10.14</td><td>107</td><td>6/3/2017 06:05</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>19</td><td>H</td><td>165.5</td><td>175</td><td>9.5</td><td>10.18</td><td>10.18</td><td>107</td><td>6/3/2017 07:00</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td>20</td><td>H</td><td>175</td><td>184.5</td><td>9.5</td><td>9.82</td><td>9.82</td><td>103</td><td>6/3/2017 08:10</td><td></td><td>Nonmagnetic</td><td></td><td></td></tr><tr><td></td><td></td><td colspan="3">Hole U1505D totals: 184.5</td><td colspan="2">191.43</td><td colspan="2">191.43</td><td colspan="3"></td><td></td><td></td></tr><tr><td></td><td></td><td colspan="3">Site U1505 totals: 668.0</td><td colspan="2">675.19</td><td colspan="2">675.19</td><td colspan="3"></td><td></td><td></td></tr></tbody></table>

47F. All HLAPC cores were considered partial strokes, with the standpipe retaining pressure after each core. The residual pressure in the standpipe was bled off using the Cameron Orbit valve. HLAPC refusal was determined with recovery of 3.14 m and 2.60 m on Cores 46F and 47F, respectively. While bleeding pressure on Core 47F, the diaphragm on the pneumatic actuation for the Orbit

valve failed. The pressure was bled by manually opening the valve, and the valve was taken out of service and repaired.

The XCB system was then deployed and used to core to 480.2 m before reaching the maximum allowable drill string weight dictated the end of coring operations. The hole was displaced using heavy mud, and the bit was raised to 80.1 m in preparation for logging.
A modified triple combo tool string was rigged up and lowered into the hole. The tool string was exceptionally long, consisting of all tools typically run as part of the triple combo (MSS; High-Resolution Laterolog Array [HRLA]; HLDS, with source; HNGS; Enhanced Digital Telemetry Cartridge [EDTC]; and logging equipment head-q tension [LEH-QT]), with the addition of the DSI tool for acoustic velocity. The DSI was added to the first run in anticipation of potential hole problems that might prevent subsequent runs based on experience at nearby sites with similar lithology. The triple combo began collecting data a few meters above the seafloor and recorded continuously to the deepest point the tools could reach, a firm hole obstruction at 341.2 m. The tool string was unable to pass below that depth even after several attempts. Accordingly, the repeat pass was conducted from that depth for a length of ~110 m, and then the main pass was also conducted from that depth up to just above the seafloor. During the run, the triple combo collected NGR, density (with caliper), acoustic velocity, neutron porosity, and magnetic susceptibility data. The caliper indicated that the hole diameter was too large (>14 inches) for effectively collecting useful data with the Formation MicroScanner (FMS) and Versatile Seismic Imager tool strings. Therefore, the decision was made to end downhole logging operations in Hole U1505C. The tools were pulled to the surface after logging was completed and rigged down. The bit was then raised, clearing the seafloor at 1755 h on 2 June and ending Hole U1505C.

Total time spent on Hole U1505C was 103 h (4.3 days). The APC, HLAPC, and XCB systems were deployed in the hole, coring a 480.2 m interval and recovering 480.15 m (100%). The APC system was used to cut 23 cores over a 207.1 m interval with 100% recovery. The HLAPC system was used to cut 24 cores over a 109.9 m interval, recovering 112.9 m (103%). The XCB system recovered 160.4 m of sediment (98%) over a 163.2 m interval. Nonmagnetic core barrels were used on all cores from this hole. All full-length APC cores were oriented. APCT-3 temperature measurements were taken on Cores 4H, 7H, 10H, and 13H.

## Hole U1505D

The vessel was offset 20 m south, and the bit was spaced out to 2911.6 m. APC coring in Hole U1505D started at 2200 h on 2 June 2017. Seafloor was calculated at 2917.5 mbls based on recovery from Core 1H. The hole was cored to a total depth of 184.5 m using only the APC system. The bit was then recovered to the surface, clearing the seafloor at 1800 h and the rotary table at 2310 h on 2 June. The beacon was recovered while raising the pipe and was on deck at 1953 h. The thrusters were raised, and the rig floor was secured for transit. The vessel was underway to return to Site U1504 at 0048 h on 3 June, ending Hole U1505D and Site U1505. Our plan was to use the time remaining on the expedition to drill a second hole to basement at Site U1504.

Overall, 20 APC cores were taken in Hole U1505D over a 184.5 m interval, with 191.43 m recovered (104%). Nonmagnetic core barrels were used for all cores, and all cores were oriented using the Icefield MI-5 core orientation tool.

## Lithostratigraphy

We examined the lithostratigraphy in Holes U1505A, U1505C, and U1505D (Figure F7) and defined two lithostratigraphic units. In Hole U1505A, the mudline core misfired (see Operations), and therefore only a 0.33 m interval of the sediment section was recovered.

In Hole U1505B, only a mudline core was recovered for educational use, and the core was not described. Hole U1505C was cored to ~480 m using the APC and XCB systems and was used to define the lithostratigraphic unit boundaries. Hole U1505D only recovered the upper section of lithostratigraphic Unit I. Unit I is defined and divided into three subunits based on visual core description, smear slide and thin section inspection, and X-ray diffraction (XRD) analysis (see Lithostratigraphy in the Expedition 367/368 methods chapter [Sun et al., 2018]).

The sediment succession recovered at Site U1505 extends from 0.00 to 480.54 m (Cores 368-U1505A-1H, 368-U1505C-1H through 64X, and 368-U1505D-1H through 20H).

Unit I is dominated by nannofossil ooze with varying amounts of foraminifers and clay and, in the upper interval of the core, with biogenic silica. The change downhole to Unit II is marked by a sharp change from greenish gray nannofossil ooze (Unit I) to dark greenish gray silty clay and clayey silt with nannofossils (Unit II). The contact between Units I and II occurs between two full-recovery cores but may not have been fully recovered.

## Unit description

### Unit I

Intervals: 368-U1505A-1H-1, 0 cm, to 1H-1, 33 cm;

368-U1505C-1H-1, 0 cm, to 56X-CC, 37 cm;

368-U1505D-1H-1, 0 cm, to 20H-CC, 20 cm

Depths: Hole U1505A = 0–0.33 m; Hole U1505C = 0–403.79 m;

Hole U1505D = 0–184.82 m

Age: Pleistocene–late Oligocene

### Lithology and sedimentary structures

Lithostratigraphic Unit I is dominated by nannofossil ooze with varying amounts of foraminifers and clay. The upper part is biosiliceous-rich clay (Figure F8D) with minor nannofossil-rich biosiliceous ooze with clay. The unit is divided into three subunits, IA–IC, based on changes in the biogenic component of the sediment and color changes that coincide with subtle changes in the sediment components.

The boundary between Units I and II is marked by a sharp change in lithology from nannofossil ooze–dominated sediments to silt and clay–dominated sediments.

### Bulk mineralogy and chemistry

The bulk mineralogy results of XRD analyses are listed in Table T2 and shown in Figure F9, which also shows the downcore variations in the relative abundance of minerals in bulk sediments at Site U1505. Unit I sediment is composed mainly of calcite, quartz, plagioclase, halite, and pyrite, as well as K-feldspar and clay minerals, including smectite, illite, kaolinite, and chlorite. In general, the percentages of halite and most terrigenous minerals in Unit I, including quartz, plagioclase, K-feldspar, and clay minerals (illite, kaolinite, and chlorite) decrease downhole, whereas calcite and pyrite increase.

Compositional analyses of the nannofossil ooze in Sections 368-U1505C-56X-7 and 56X-CC (Subunit IC) were made directly on the archive half of the core using the handheld portable X-ray fluorescence spectrometer (pXRF) (see Igneous and metamorphic petrology in the Expedition 367/368 methods chapter [Sun et al., 2018]) to examine in detail the transition between Units I and II (Table T3). The 16 intervals analyzed in Unit I show no variation in composition, with CaO contents of ~30 wt%, SiO₂ contents of ~20–
<figure><img src="image_451.png" /><figcaption>Figure F7. Lithostratigraphic summary, Site U1505.</figcaption></figure>

24 wt%, and lower Al₂O₃ (~5 wt%), Fe₂O₃ (<3 wt%), and MgO (<2 wt%) abundances. The ooze has Sr contents between 700 and 800 ppm and Zr contents between 50 and 60 ppm.

## Subunit IA

Intervals: 368-U1505A-1H-1, 0–33 cm;
368-U1505C-1H-1, 0 cm, to 4H-1, 56 cm;
368-U1505D-1H-1, 0 cm, to 4H-3, 150 cm

Depths: Hole U1505A = 0–0.33 m; Hole U1505C = 0–27.76 m;
Hole U1505D = 0–27.50 m

Age: Pleistocene

Subunit IA spans the recovered uppermost 27.76 m in Hole U1505C and 27.50 m in Hole U1505D and is dominated by dark greenish gray and greenish gray biosiliceous-rich clay with nannofossils, nannofossil-rich clay with biogenic silica, and nannofossil-rich biosiliceous ooze with clay (Figure F8A). The abundance of bio-
Figure F8. Representative images of core sections from three subunits in Unit I, Hole U1505C. A. Dark greenish gray biosiliceous-rich clay with nannofossils. A vague lamination is disrupted by bioturbation. B. Slight variation in texture and color related to changes in the percentage of clay and foraminifers. Upper part is more clay rich than the lower section. C. Light brownish gray clay-rich nannofossil ooze (with foraminifers). As for B, the variation in color and texture in Subunit IC corresponds to variations in the lithology. Mottled color variation is due to bioturbation. D. Nannofossil-rich clay with nannofossils, sponge spicules, radiolarians, and terrigenous grains in Subunit IA.

<figure><img src="image_452.png" /><figcaption>Table T2. Mineral percentages, Site U1505. **View table in PDF format. Download available in CSV format.**</figcaption></figure>

genic silica decreases downhole. The fine-grained component comprises nannofossils, foraminifers, diatoms, sponge spicules, radiolarians, and terrigenous grains, including clay minerals, and rare quartz and feldspar (Figure F8D). The sediment is well sorted and unlithified. The average grain size is clay, and very fine sand is the maximum grain size. Bioturbation is heavy (Figure F8A).

A pinkish gray, ~6 cm thick, slightly normally graded ash layer was found in interval 368-U1505C-3H-3, 24–32 cm (Figure F10A), and ash pods were found at the corresponding depth in Hole U1505D in interval U1505D-3H-5, 83–86 cm (Figure F10B).

The base of Subunit IA is marked by both a color change from dark greenish gray to dark gray sediment in Subunit IB and by a lithologic change that reflects an increase in the percentage of foraminifers.

## Subunit IB

Intervals: 368-U1505C-4H-1, 56 cm, to 38F-1, 49 cm; 368-U1505D-4H-4, 0 cm, to 20H-CC, 20 cm

Depths: Hole U1505C = 27.76–273.39 m; Hole U1505D = 27.50–184.82

Age: Pleistocene to middle Miocene

Subunit IB is 245.63 m thick and comprises light gray, gray, grayish brown, light brownish gray, light brown, and brown nannofossil ooze with minor silty intervals (Figure F8B). The color change reflects the varying abundance of foraminifers and clay. The sediment is well sorted and slightly consolidated. The sediment structure is massive. The average grain size is clay, and medium sand is the maximum grain size. Boundaries are subhorizontal, horizontal, or inclined. Bioturbation is moderate to heavy. Thin, silty, fining-upward intervals with erosive bottom contacts are common in Subunit IB (Figure F11). One ~5 cm thick very dark greenish gray ash layer with a dispersed top and a sharp basal contact is found in interval 368-U1505C-8H-6, 47–52 cm (Figure F10C, F10D). Pyrite patches are common.

From Core 19H downhole, basal flow-in destroys the sediment structures (Figure F12).

The boundary between Subunits IB and IC is defined by the first occurrence of burrows of *Zoophycos*.

## Subunit IC

Interval: 368-U1505C-38F-1, 49 cm, to 56X-CC, 37 cm

Depth: 273.39–403.79 m

Age: middle Miocene to late Oligocene

Subunit IC is 130.40 m thick and composed of gray, greenish gray, and light brownish gray clay-rich nannofossil ooze (with foraminifers), foraminifer-rich nannofossil ooze with clay, and minor amounts of nannofossil-rich clay (Figure F8C). The sediment is well sorted and well consolidated. The average grain size is clay, and very fine sand is the maximum grain size.

Contacts between layers are often bioturbated or gradational, horizontal to subhorizontal, or inclined. The bioturbation in Subunit IC sediment is heavy to complete. Greenish reduction spots are common and are related to burrows. Burrows are often filled with foraminifers and are dark gray in color. The trace fossil assemblage includes *Chondrites*, *Thalassinoides*, *Planolites*, and *Zoophycos* (Figure F13).

Compositional analyses of the ooze in Subunit IC were made directly on the archive half of the core using the handheld pXRF instrument (see *Igneous and metamorphic petrology* in the Expedition 367/368 methods chapter [Sun et al., 2018]) (Table T3). The ooze (16 analyses) in Sections 368-U1505C-56X-7 and 56X-CC shows only minor variation in bulk composition. The major components are CaO (28–35 wt%), SiO₂ (18–25 wt%), and Al₂O₃ (4–6 wt%). The ooze has Sr contents of 730–840 ppm.

The boundary between Subunit IC and Unit II is characterized by a sharp change from greenish gray clay-rich nannofossil ooze to very dark greenish gray silty clay.

## Unit II

Interval: 368-U1505C-57X-1, 0 cm, to 64X-CC, 36 cm

Depth: 403.50–480.54 m

Age: Oligocene
<figure><img src="image_453.png" /><figcaption>Table T3. Bulk chemistry data obtained from shipboard handheld portable X-ray fluorescence analysis, Site U1505. [View table in PDF format. Download available in CSV format.]</figcaption></figure>

## Lithology and sedimentary structures

Unit II is dominated by dark greenish gray, well-consolidated silty clay and clayey silt (with nannofossils). The amount of nannofossils increases downhole (nannofossil-rich silty clay and clayey silt with nannofossils) to Core 368-U1505C-62X and then decreases in Cores 63X and 64X. The average grain size is silt and clay, and fine to medium sand is the maximum grain size. The sediment is thinly laminated. Bioturbation is heavy, and foraminifers and shell fragments are common (Figure F14E). Pyrite forms up to centimeter-sized patches, and rare concentrations of organic matter were also observed (Figure F14C, F14D). Glauconite grains are especially abundant in Sections 58X-4 (Figure F14A, F14B) and 59X-2.

## Bulk mineralogy and chemistry

The bulk mineralogy results of XRD analyses are listed in Table T2. Unit II sediments are composed mainly of glauconite, quartz, plagioclase, clay minerals (including smectite, illite, and kaolinite), and minor amounts of pyrite and calcite. Figure F9 shows the downhole variations in the relative abundance of minerals identified by XRD in bulk sediments at Site U1505. Compared to Unit I, Unit II shows distinctly higher percentages of glauconite, plagioclase, kaolinite, and illite. In contrast, Unit II sediments have lower percentages of calcite, halite, K-feldspar, chlorite, and smectite.

Compositional analyses of Unit II clay were made directly on the archive half of the core using the handheld pXRF instrument (see Igneous and metamorphic petrology in the Expedition 367/368 methods chapter [Sun et al., 2018]) (Table T2). The clay (eight analyses) in Section 368-U1505C-57X-1 shows little variation in bulk composition. The major components are SiO₂ (~45 wt%), Al₂O₃ (12–16 wt%), and minor MgO (2–4 wt%) and K₂O (~2 wt%). The clay has Sr contents of ~150 ppm and Zr contents of ~80 ppm.

# Discussion

## Depositional environment of Unit II

Unit II was most likely deposited in a moderately deep water (upper slope) marine-depositional environment based on the high clay content, abundance of nannofossils, and presence of glauconite. In general, the sediment is fine grained (silty clay) and dominated by terrigenous materials (quartz, feldspar, and clay minerals), with lesser calcareous microfossils, including nannofossils and foraminifers, minor authigenic glauconite and calcite, and rare radiolarians. Small shelly fragments, microfossils, and organic fragments are visible on the core surface, along with occasional macrofossils, including bivalves.

Glauconite grains are present between Sections 368-U1505C-58X-4 and 62X-6. The presence of glauconite indicates that the sediment was most likely deposited at temperatures ranging from 7°C to 15°C (Margielewski et al., 2017) in low oxygen conditions and in shelf to lower slope environments from 20 to 700 m water depth (e.g., Drzewiecki and Simo, 2002; Margielewski et al., 2017).

## Depositional environment of Unit I

Lithostratigraphic Unit I was deposited in a deep-marine environment. The dominant lithology is nannofossil ooze with variable amounts of clay and foraminifers. The top of Unit I is more clay rich and contains siliceous microfossils. Lithologic differences between subunits likely reflect changes in the amount of terrigenous input into a relatively open ocean setting, climate change, and changes in oceanographic conditions. The terrigenous input may be delivered as buoyant plumes from shallower shelf environments and rarely by weak (distal) turbidity currents. There is little change in the composition of the terrigenous grains through Unit I, so we envisage a similar source for these grains. Thin laminae of silt, often with pyrite, are found sparsely throughout Unit I. Some are graded, and all have sharp bases; however, many are disrupted by bioturbation and interpreted as distal turbidites.
Figure F10. A. Pinkish gray ash layer. B. Transparent glass shards dispersed in nannofossil-rich clay. C. Thin black ash layer and dispersed ash. D. Glass shards with clay minerals in the black ash shown in C.

<figure><img src="image_454.png" /></figure>

## Preliminary correlation between Units I and II at Sites U1501, U1504, and U1505

Site U1501 is located 50.28 km west of Site U1504 on the OMH. Site U1505 is in the vicinity of Site U1501 (10.46 km east). Today's water depths are very similar at Sites U1501, U1504, and U1505 (2857, 2816, and 2917 mbsl, respectively). The recovered Pleistocene to early Miocene/Oligocene sediment successions can be correlated based on their major lithologies and the age of deposition. We suggest a correlation between Pleistocene Subunit IA (Site U1505), Pleistocene Subunit IA (Site U1504), and Pleistocene to Pliocene Subunits IA and IB (Site U1501) because all are dominated by dark greenish gray nannofossil-rich clay and clay-rich nannofossil-ooze with siliceous microfossils. At Site U1504, there seems to be a hiatus below Subunit IA (see **Biostratigraphy**). Between Sites U1504 and U1501, middle Miocene Subunit IB (Site U1504) correlates well with late to middle Miocene Subunit IC (Site U1501). These subunits are both composed of greenish gray and light brownish gray nannofossil ooze with clay- and foraminifer-rich intervals. Middle Miocene Subunit IC (Site U1504) can be correlated with middle Miocene to Oligocene Subunits ID and IE (Site U1501). These subunits are characterized by greenish gray and gray nannofossil ooze with clay.

Despite being close to Site U1501, the lack of distinct boundaries in the lithology at Site U1505 makes correlation between these sites difficult. Pleistocene to late Oligocene Subunits IB and IC (Site

Figure F11. A. Fining-upward interval with foraminiferal silty sand grading upward to nannofossil-rich silty clay and then to nannofossil ooze with foraminifers. B. Two fining-upward intervals with nannofossil-rich silty clay grading upward into nannofossil ooze with clay. C. Fining-upward interval with pyrite-rich silty sand grading upward into clay-rich nannofossil ooze. The interval has been disrupted by bioturbation. Note the green reduced sediment in the silty sand interval and green reduction spots in the clay-rich nannofossil ooze. D. Detail of foraminiferal silty sand shown in A. E. Detail of silty sand shown in C.

<figure><img src="image_455.png" /></figure>

U1505) correlate in time to Subunits IC-IF at Site U1501 and Subunit IB and Unit II at Site U1504. In addition, although there is a change from brownish to grayish layers at Site U1505, as was observed at Sites U1501 and U1504, the color changes are more subtle and without clear boundaries, making correlation difficult. Therefore, a more detailed correlation of the post-Oligocene sediments between the three sites will require postexpedition research.

Unit II at Site U1505 correlates well with Unit II at Site U1501. There is an unconformity at the boundary between Unit I and Unit II at Site U1501 and a sharp lithologic boundary between the two units at Site U1505. The carbonate-to-clay ratio abruptly changes at this boundary at both sites, and Unit I has more abundant calcareous microfossils than Unit II. The sedimentation rate is very low below the Unit II/I boundary at both sites (see **Biostratigraphy**).
Figure F12. A, B. Destruction of sedimentary features caused by drilling disturbance (basal flow-in) that affected Cores 368-U1505C-19H through 47F.

<figure><img src="image_456.png" /></figure>

## Structural geology

Site U1505 is located on the OMH at a water depth of 2917 m roughly 10 km from Site U1501. The sedimentary and structural record at these two sites is very similar.

### Lithostratigraphic Unit I structures

Lithostratigraphic Unit I, which consists of nannofossil oozes, shows predominantly horizontal to subhorizontal bedding that in most cases is erased due to moderate to strong bioturbation and drilling disturbance. Unit I is devoid of any visible structures related to tectonic deformation.

Figure F13. Typical ichnospecies in Subunit IC. A. Large inclined burrow with uneven walls. B. *Chondrites* (Ch), *Planolites* (Pl), and *Zoophycos* (Zo). Note the foraminifers on the core surface. C. Combination of horizontal, vertical, and inclined burrows. D. Inclined *Zoophycos* burrow.

<figure><img src="image_457.png" /></figure>

Various burrows in clay-rich nannofossil ooze of Unit IC

### Lithostratigraphic Unit II structures

Lithostratigraphic Unit II is characterized by subhorizontal to gently dipping bedding as shallow as 10°. Similar to Site U1501, some minor deformation structures are heterogeneously distributed within Unit II. In Core 368-U1505C-60X (Figure F15), millimeter-scale normal faults and joints show comparable geometries to those described in *Structural geology* in the Site U1501 chapter (Larsen et al., 2018a). In most cases, these deformation structures are overprinted by drilling disturbance, making their recognition difficult.

## Biostratigraphy

All core catcher samples from Holes U1505A, U1505B, and U1505C were analyzed for calcareous nannofossils, planktonic foraminifers, and diatoms. Additional samples were taken from intervals within the working-half cores when necessary to refine the ages. Preservation of calcareous microfossils is good in Cores 368-U1505C-1H through 48X and moderate to poor in Cores 49X
Figure F14. Special features in Unit II. A. Thick lamination rich in glauconite grains interbedded with dark greenish gray silty clay with disseminated glauconite. B. Glauconite grains in silty clay. C. Diagenetic pyrite grains possibly replacing a burrow fill and lamination in heavily bioturbated nannofossil-rich silty clay. D. Organic matter in nannofossil-rich silty clay. E. Bivalve macrofossil in nannofossil-rich silty clay. Note the small shelly fragments on the core surface.

<figure><img src="image_458.png" /></figure>

through 64X. Planktonic foraminifers are abundant or common in Cores 1H through 56X and 59X through 62X and few or rare in Cores 57X, 58X, 63X, and 64X. Calcareous nannofossils are generally abundant to common in most samples from Hole U1505C, except in the upper part of Core 57X, where they are rare to absent.

Forty-five biostratigraphic datums identified in Hole U1505C suggest a continuous succession of early Oligocene to Holocene age (Tables T4, T5; Figure F16). The Pleistocene/Pliocene boundary was placed within Core 7H, the Pliocene/Miocene boundary between Cores 11H and 13H, and the Miocene/Oligocene boundary between Cores 54X and 55X. Sedimentation rates vary from ~7 mm/ky in the Oligocene to ~15 mm/ky during the Miocene-Pliocene and ~24 mm/ky during the Pleistocene.

Relatively lower planktonic foraminifer content below Core 57X indicates a shoaling marine environment during the early Oligocene, whereas much higher abundances of planktonic foraminifers above Core 56X suggest a deep-water environment since the late Oligocene.

Figure F15. Deformation structures made of en echelon millimeter-scale normal faults and fractures, Unit II. Structures resemble those observed in Subunit IIA at Site U1501 (see Figure F27 in the Site U1501 chapter [Larsen et al., 2018a]).

<figure><img src="image_459.png" /></figure>

## Calcareous nannofossils

Core catchers from Holes U1505A, U1505B, and U1505C were examined (Table T6). Calcareous nannofossil biostratigraphy for Site U1505 was based mainly on the analysis of all core catcher samples from Hole U1505C, and a number of samples from intervals within cores were analyzed to better constrain the biostratigraphic events.

Nannofossils are abundant to common in most samples from Hole U1505C with the exception of those from the upper part of Core 57X. They are barren in Samples 57X-1, 0–1 cm, and 57X-1, 24–25 cm, rare in Sample 57X-1, 144–145 cm, and resume common to abundant occurrences below Sample 57X-6, 1–2 cm. These occurrences indicate a significant change in nannofossil abundance between Samples 57X-1, 144–145 cm, and 57X-6, 1–2 cm.

Nannofossil preservation is good in most samples from Hole U1505C with the exception of Samples 52X-CC to 60X-CC. In this interval, discoasterids and *Sphenolithus* show slight to heavy overgrowth.

Twenty-seven nannofossil biostratigraphic datums were recognized in the Oligocene through Pleistocene sediment sequence (Table T4). The oldest nannofossil event identified at Site U1505 is the last appearance datum (LAD) of *Reticulofenestra umbilicus*, which occurs at 430.26 m in Hole U1505C and indicates an age older than 32.02 Ma.

### Pleistocene

The top of Hole U1505C (Samples 1H-CC to 2H-CC; 17.74 m) is dated as late Pleistocene based on the presence of *Emiliania huxleyi* (marker species for Zone NN21). The LAD of *Pseudoemiliania lacinosa* in Sample 4H-CC (37.17 m) defines the top of Zone NN19. Zone NN19 is further divided by two nannofossil events, the first appearance datum (FAD) of *Gephyrocapsa* spp. >4 µm reentrance in Sample 5H-CC (46.51 m) and the LAD of *Caldiscus macintyrei* in Sample 6H-CC (56.23 m).

### Pliocene

Pliocene nannofossil Zones NN16, NN15, and NN12 were recognized in Hole U1505C. Two events occur in the lower part of Zone NN16: the LAD of *Discoaster tamalis* (2.8 Ma) in Sample 7H-CC (65.70 m) and the LAD of *Sphenolithus* spp. (3.54 Ma) in Sample 8H-CC (74.95 m). The LAD of *Reticulofenestra pseudoumbilicus* (3.70 Ma) in Sample 9H-CC (84.18 m) defines the top of Zone
<table><caption>Table T4. Calcareous nannofossil biostratigraphic events recognized at Site U1505. T = top/last appearance datum, B = bottom/first appearance datum. Download available in CSV format.</caption><thead><tr><th rowspan="2">Epoch</th><th rowspan="2">Biozone (Martini, 1971)</th><th rowspan="2">Calcareous nannofossil event</th><th colspan="2">Top</th><th colspan="2">Bottom</th><th colspan="2">Age model</th></tr><tr><th>Core, section</th><th>Depth CSF-A (m)</th><th>Core, section, interval (cm)</th><th>Depth CSF-A (m)</th><th>Depth (m)</th><th>Age (Ma)</th></tr></thead><tbody><tr><td rowspan="3">Pleistocene</td><td>NN21</td><td>B Emiliania huxleyi</td><td>368-U1505C-2H-CC</td><td>17.74</td><td>368-U1505C-3H-CC</td><td>26.04</td><td>21.89</td><td>0.29</td></tr><tr><td rowspan="3">NN19</td><td>T Pseudoemiliania lacunosa</td><td>3H-CC</td><td>26.04</td><td>4H-CC</td><td>37.17</td><td>31.61</td><td>0.44</td></tr><tr><td>B Gephyrocapsa spp. &gt;4 µm reentrance</td><td>5H-CC</td><td>46.51</td><td>6H-CC</td><td>56.23</td><td>51.37</td><td>1.04</td></tr><tr><td>T Calcidiscus macintyrei</td><td>5H-CC</td><td>46.51</td><td>6H-CC</td><td>56.23</td><td>51.37</td><td>1.60</td></tr><tr><td rowspan="3">Pliocene</td><td>NN16</td><td>T Discoaster tamalis<br>T Sphenolithus spp.</td><td>6H-CC<br>7H-CC</td><td>56.23<br>65.70</td><td>7H-CC<br>8H-CC</td><td>65.70<br>74.95</td><td>60.97<br>70.33</td><td>2.80<br>3.54</td></tr><tr><td>NN15</td><td>T Reticulofenestra pseudoumbilicus</td><td>8H-CC</td><td>74.95</td><td>9H-CC</td><td>84.18</td><td>79.57</td><td>3.70</td></tr><tr><td>NN12</td><td>T Ceratolithus acutus</td><td>10H-CC</td><td>93.65</td><td>11H-CC</td><td>102.78</td><td>98.22</td><td>5.04</td></tr><tr><td rowspan="10">Miocene</td><td rowspan="5">late</td><td>NN11</td><td>T Nicklithus amplificus</td><td>12H-CC</td><td>111.73</td><td>13H-CC</td><td>122.71</td><td>117.22</td><td>5.94</td></tr><tr><td>NN11</td><td>B Nicklithus amplificus</td><td>14H-CC</td><td>132.23</td><td>15H-CC</td><td>141.32</td><td>136.78</td><td>6.91</td></tr><tr><td>NN11</td><td>B Discoaster berggrenii</td><td>16H-CC</td><td>150.90</td><td>17H-CC</td><td>160.67</td><td>155.79</td><td>8.29</td></tr><tr><td>NN10</td><td>T Discoaster bollii</td><td>17H-CC</td><td>160.67</td><td>18H-CC</td><td>170.28</td><td>165.48</td><td>9.21</td></tr><tr><td>NN9</td><td>T Discoaster hamatus</td><td>18H-CC</td><td>170.28</td><td>19H-CC</td><td>179.75</td><td>175.02</td><td>9.53</td></tr><tr><td rowspan="3">middle</td><td>NN9</td><td>B Discoaster hamatus</td><td>20H-CC</td><td>189.26</td><td>21H-CC</td><td>196.53</td><td>192.90</td><td>10.55</td></tr><tr><td>NN8</td><td>B Catinaster coalithus</td><td>21H-CC</td><td>196.53</td><td>22H-CC</td><td>200.06</td><td>198.30</td><td>10.89</td></tr><tr><td>NN6</td><td>T Cyclicargolithus floridanus</td><td>22H-CC</td><td>200.06</td><td>23H-CC</td><td>207.05</td><td>203.56</td><td>11.85</td></tr><tr><td rowspan="4">early</td><td>NN6</td><td>T Coronocyclus nitescens</td><td>24F-CC</td><td>212.18</td><td>25F-CC</td><td>216.92</td><td>214.55</td><td>12.12</td></tr><tr><td>NN6</td><td>B Reticulofenestra pseudoumbilicus</td><td>28F-CC</td><td>230.93</td><td>29F-CC</td><td>235.69</td><td>233.31</td><td>12.83</td></tr><tr><td>NN5</td><td>T Sphenolithus heteromorphus</td><td>28F-CC</td><td>230.93</td><td>29F-CC</td><td>235.69</td><td>233.31</td><td>13.53</td></tr><tr><td>NN4</td><td>T Helicosphaera ampliaperta</td><td>34F-CC</td><td>259.17</td><td>35F-CC</td><td>263.83</td><td>261.50</td><td>14.91</td></tr><tr><td rowspan="4">Oligocene</td><td rowspan="2">NP25</td><td rowspan="2">NN2</td><td>T Triquetrorhabdulus carinatus</td><td>46F-CC</td><td>310.74</td><td>47F-CC</td><td>314.90</td><td>312.82</td><td>18.28</td></tr><tr><td>B Helicosphaera ampliaperta</td><td>48X-CC</td><td>326.93</td><td>49X-CC</td><td>336.70</td><td>331.82</td><td>20.43</td></tr><tr><td rowspan="2">NP24</td><td rowspan="2">NP22</td><td>B Sphenolithus disbelemnos</td><td>53X-CC</td><td>374.57</td><td>54X-CC</td><td>383.95</td><td>379.26</td><td>22.76</td></tr><tr><td>T Reticulofenestra bisecta &gt;10 µm</td><td>54X-CC</td><td>383.95</td><td>55X-CC</td><td>394.11</td><td>389.03</td><td>23.13</td></tr><tr><td rowspan="2">Oligocene</td><td>NP25</td><td>T Sphenolithus ciperoensis</td><td>55X-CC</td><td>394.11</td><td>56X-CC</td><td>403.84</td><td>398.98</td><td>24.43</td></tr><tr><td>NP24</td><td>T Sphenolithus predistentus</td><td>56X-CC</td><td>403.84</td><td>57X-6, 1-2</td><td>411.07</td><td>407.46</td><td>26.93</td></tr><tr><td>NP22</td><td>T Reticulofenestra umbilicus</td><td>58X-CC</td><td>419.58</td><td>59X-CC</td><td>430.26</td><td>424.92</td><td>32.02</td></tr></tbody></table>

<table><caption>Table T5. Planktonic foraminifer events, Site U1505. T = top/last appearance datum, B = bottom/first appearance datum, Bc = bottom/first common appearance datum (acme). Download available in CSV format.</caption><thead><tr><th rowspan="2">Epoch</th><th rowspan="2">Biozone (Blow, 1969)</th><th rowspan="2">Calcareous nannofossil event</th><th colspan="2">Top</th><th colspan="2">Bottom</th><th colspan="2">Age model</th></tr><tr><th>Core, section</th><th>Depth CSF-A (m)</th><th>Core, section</th><th>Depth CSF-A (m)</th><th>Depth (m)</th><th>Age (Ma)</th></tr></thead><tbody><tr><td rowspan="4">Pleistocene</td><td>N22</td><td>T Globigerinoides ruber (pink)</td><td>368-U1505C-1H-CC</td><td>8.23</td><td>368-U1505C-2H-CC</td><td>17.74</td><td>12.99</td><td>0.12</td></tr><tr><td>N22</td><td>Bc Globigerinoides ruber (pink)</td><td>3H-CC</td><td>26.04</td><td>4H-CC</td><td>37.17</td><td>31.61</td><td>0.40</td></tr><tr><td>N23</td><td>T Globorotalia tosaensis</td><td>4H-CC</td><td>37.17</td><td>5H-CC</td><td>46.51</td><td>41.84</td><td>0.61</td></tr><tr><td>N20-N21</td><td>T Globorotalia multicamerata</td><td>6H-CC</td><td>56.23</td><td>7H-CC</td><td>65.70</td><td>60.97</td><td>2.18</td></tr><tr><td rowspan="2">Pliocene</td><td>N20-N21</td><td>T Sphaeroidinellopsis seminulina</td><td>7H-CC</td><td>65.70</td><td>8H-CC</td><td>74.95</td><td>70.33</td><td>3.59</td></tr><tr><td>N19</td><td>T Globoturborotalita nepenthes</td><td>9H-CC</td><td>84.18</td><td>10H-CC</td><td>93.21</td><td>88.70</td><td>4.37</td></tr><tr><td rowspan="10">Miocene</td><td>N17</td><td>T Globoquadrina dehiscens</td><td>17H-CC</td><td>160.67</td><td>18H-CC</td><td>170.28</td><td>165.48</td><td>5.92</td></tr><tr><td>N14</td><td>T Paragloborotalia mayeri</td><td>20H-CC</td><td>189.26</td><td>21H-CC</td><td>196.53</td><td>192.90</td><td>10.46</td></tr><tr><td>N13</td><td>B Globoturborotalita nepenthes</td><td>25H-CC</td><td>216.92</td><td>26H-CC</td><td>221.54</td><td>219.23</td><td>11.63</td></tr><tr><td>N12</td><td>T Fohsella fohsi</td><td>25H-CC</td><td>216.92</td><td>26H-CC</td><td>221.54</td><td>219.23</td><td>11.79</td></tr><tr><td>N8</td><td>T Praeorbulina circularis</td><td>33F-CC</td><td>254.46</td><td>34F-CC</td><td>259.17</td><td>256.82</td><td>14.89</td></tr><tr><td>N8</td><td>B Praeorbulina sicana</td><td>44F-CC</td><td>303.21</td><td>45R-CC</td><td>307.92</td><td>305.57</td><td>16.38</td></tr><tr><td>N6</td><td>T Catapsydrax dissimilis</td><td>47F-CC</td><td>314.90</td><td>48F-CC</td><td>326.93</td><td>320.92</td><td>17.54</td></tr><tr><td>N5</td><td>T Globoquadrina binaensis</td><td>49F-CC</td><td>336.70</td><td>49F-CC</td><td>336.70</td><td>336.70</td><td>19.09</td></tr><tr><td>N4</td><td>T Paragloborotalia kugleri</td><td>50F-CC</td><td>346.12</td><td>51F-CC</td><td>355.58</td><td>350.85</td><td>21.12</td></tr><tr><td rowspan="3">Oligocene</td><td>N4</td><td>T Globigerina ciperoensis</td><td>53X-CC</td><td>374.57</td><td>54X-CC</td><td>383.95</td><td>379.26</td><td>22.90</td></tr><tr><td>P21</td><td>T Paragloborotalia opima</td><td>56X-CC</td><td>403.84</td><td>57X-CC</td><td>413.49</td><td>408.67</td><td>26.93</td></tr><tr><td>P19</td><td>T Turborotalia ampliapertura</td><td>58X-CC</td><td>419.58</td><td>59X-CC</td><td>430.26</td><td>424.92</td><td>30.28</td></tr></tbody></table>

NN15. The LAD of *Ceratolithus acutus* (5.04 Ma) in Sample 11H-CC (102.78 m) defines the top of Zone NN12. The Pliocene/Miocene boundary in Hole U1505C was placed between Samples 11H-CC (102.78 m) and 13H-CC (122.71 m) based on the LADs of *C. acutus* and *Nicklithus amplificus*, respectively.

## Miocene

Seven events occur in the late Miocene strata of Hole U1505C. Zone NN11 includes three events: the LAD of *N. amplificus* (5.94 Ma) in Sample 13H-CC (122.71 m), the FAD of *N. amplificus* (6.91 Ma) in Sample 14H-CC (132.23 m), and the FAD of *Discoaster berg-*.
<figure><img src="image_460.png" /><figcaption>Table T6. Distribution of calcareous nannofossils, Site U1505. **View table in PDF format. Download available in CSV format.**</figcaption></figure>

grenii (8.29 Ma) in Sample 16H-CC (150.90 m). The LAD of *Discoaster bollii* (9.21 Ma) in Sample 18H-CC (170.28 m) falls within Zone NN10. The LAD (9.53 Ma) and FAD (10.55 Ma) of *Discoaster hamatus*, which occur in Samples 19H-CC (179.75 m) and 20H-CC (189.26 m), respectively, define Zone NN9. The FAD of *Catinaster coalitus* (10.89 Ma) was used to mark the base of Zone NN8, which occurs in Sample 21H-CC (196.53 m). The late/middle Miocene

boundary in Hole U1501C was assigned between Samples 21H-CC (196.53 m) and 23H-CC (207.05 m) based on the FAD of *C. coalitus* (10.89 Ma) and the LAD of *Cyclicargolithus floridanus* (11.85 Ma), respectively.

Five events are recorded in the middle Miocene strata of Hole U1505C. The top of Zone NN6 is marked by the LAD of *C. floridanus* (11.85 Ma) in Sample 23H-CC (207.05 m). Two additional events were found in Zone NN6: the LAD of *Coronocyclus nitescens* (12.12 Ma) in Sample 25F-CC (216.92 m) and the FAD of *R. pseudoumbilicus* (12.83 Ma) in Sample 28F-CC (230.93 m). The top of
Zone NN5 is marked by the LAD of *Sphenolithus heteromorphus* (13.53 Ma) in Sample 29F-CC (235.69 m). The top of Zone NN4 is defined by the LAD of *Helicosphaera ampliaperta* (14.91 Ma) in Sample 35F-CC (263.83 m). The middle/early Miocene boundary was assigned between Samples 35F-CC (263.83 m) and 47F-CC (314.90 m).

Three events were recognized in the early Miocene strata of Hole U1505C. The top of Zone NN2 is marked by the LAD of *Triquetrorhabdulus carinatus* (18.28 Ma) in Sample 47F-CC (314.90 m). The bottom of Zone NN2 is defined by the FAD of *Sphenolithus disbelemnos* (22.76 Ma), which occurs in Sample 53X-CC (374.57 m). One additional event, the FAD of *H. ampliaperta* (20.43 Ma) within Zone NN2, was found in Sample 48X-CC (326.93 m). The Miocene/Oligocene boundary was assigned between Samples 53X-CC (374.57 m) and 55X-CC (394.11 m) based on the FAD of *S. disbelemnos* (22.76 Ma) and the LAD of *Reticulofenestra bisecta* >10 µm (23.13 Ma), respectively.

## Oligocene

Four events were identified in the Oligocene strata of Hole U1505C. The top of Zone NP25 is marked by the LAD of *R. bisecta* (>10 µm; 23.13 Ma) in Sample 55X-CC (394.11 m). The LAD of *Sphenolithus ciperoensis* (24.43 Ma) within Zone NP25 occurs in Sample 56X-CC (403.84 m). The top of Zone NP24 was recognized by the LAD of *Sphenolithus predistentus* (26.93 Ma) in Sample 57X-6, 1–2 cm (411.07 m). The top of Zone NP22 is marked by the LAD of *R. umbilicus* (32.02 Ma) in Sample 59X-CC (430.26 m).

Nannofossil assemblages in Samples 59X-CC through 64X-CC are characterized by relatively abundant *Braarudosphaera bigelowii*, *Helicosphaera bramlettei*, *Helicosphaera compacta*, and *Pontosphaera* spp. In particular, a significant portion of the nannofossil assemblage is composed of some late Eocene or older species such as *Pontosphaera exilis*, *Pontosphaera pectinata*, *Pontosphaera pulchripora*, *Reticulofenestra erbae*, *Reticulofenestra cf. reticulata*, *Reticulofenestra isabellae*, and *Reticulofenestra westerholdii*, suggesting that the age of the bottom of Hole U1505C is possibly the late Eocene. This evaluation warrants quantitative study during postcruise research because the definition of the late Eocene nannofossil zonation is based on their changes in abundance.

## Planktonic foraminifers

All core catcher samples and several additional samples from the split cores from Holes U1505A, U1505B, and U1505C were processed for planktonic foraminiferal analyses (Tables T7). Planktonic foraminifers are well preserved and abundant in Cores 368-U1505C-1H through 48X and moderately preserved and few in Cores 49X through 64X, except for the poorly preserved and rare condition in Cores 57X to 58X.

Only mudline cores were recovered from Holes U1505A and U1505B. No pink *Globigerinoides ruber* specimens were found in Samples 368-U1505A-1H-CC and 368-U1505B-1H-CC. Compared to the planktonic foraminiferal occurrence in Hole U1505C, the bottom age of Holes U1505A and U1505B might be younger than 0.12 Ma.

Eighteen planktonic foraminiferal datums were recognized in Hole U1505C, spanning from the early Oligocene (>32.03 Ma) to the late Pleistocene (Table T5). The planktonic foraminiferal biostratigraphy for Hole U1505C was established by these events and the planktonic foraminiferal assemblages at successive depth intervals.

The Pleistocene planktonic foraminifers are composed of *G. ruber*, *Globigerinoides sacculifer*, *Globorotalia menardii*, *Pulleniatina*

<caption>Table T7. Distribution of planktonic foraminifers, Site U1505. **View table in PDF format. Download available in CSV format.**</caption>

*obliquiloculata*, and *Neogloboquadrina dutertrei*. The LAD of pink *G. ruber* (0.12 Ma) and the FAD of pink *G. ruber* acme (0.40 Ma) occur between Samples 368-U1505C-1H-CC and 2H-CC and Samples 3H-CC and 4H-CC, respectively. The LAD of *Globorotalia tosaensis* (0.61 Ma) is located between Samples 4H-CC and 5H-CC. The LAD of *Globorotalia multicamerata* (2.18 Ma) is located between Samples 6H-CC and 7H-CC.

The Pliocene planktonic foraminiferal assemblage is characterized by the higher content of *Dentoglobigerina altispira* and *Sphaeroidinellopsis seminulina*. The LAD of *S. seminulina* (3.59 Ma) is located between Samples 7H-CC and 8H-CC. The LAD of *Globoturborotalita nepenthes* (4.37 Ma) is located between Samples 9H-CC and 10H-CC and defines the boundary of Zones N20 and N19.

The late Miocene foraminiferal assemblage is dominated by *D. altispira*, *S. seminulina*, *G. menardii*, *Globoquadrina venezuelana*, and *Globoquadrina dehiscens*. The LAD of *G. dehiscens* (5.92 Ma) is located between Samples 17H-CC and 18H-CC and defines the boundary of Zones N18 and N17. The FAD of *Paragloborotalia mayeri* (10.46 Ma) is located between Samples 20H-CC and 21H-CC and defines the boundary of Zones N15 and N14.

The middle Miocene foraminiferal assemblage is dominated by *D. altispira*, *S. seminulina*, *G. venezuelana*, *G. dehiscens*, and *Praeorbulina* spp. The FAD of *G. nepenthes* (11.63 Ma) and the LAD of *Fohsella fohsi* (11.79 Ma) are both located between Samples 25H-CC and 26H-CC and define the boundary of Zones N13 and N12 (i.e., boundary of the late/middle Miocene). The LAD of *Praeorbulina circularis* (14.89 Ma) is located between Samples 33F-CC and 34F-CC.

The late Oligocene–early Miocene planktonic foraminifers are characterized by *G. dehiscens*, *G. venezuelana*, *Catapsydrax dissimilis*, and *P. mayeri*. The FAD of *Praeorbulina sicana* (16.38 Ma) is located between Samples 44F-CC and 45F-CC and marks the boundary of Zones N8 and N7. The LAD of *C. dissimilis* (17.54 Ma) is located between Samples 47F-CC and 48F-CC and indicates the boundary of Zones N7 and N6. The LAD of *Globoquadrina binaiensis* (19.09 Ma) is located between Samples 48F-CC and 49F-CC. The LAD of *Paragloborotalia kugleri* (21.12 Ma) is located between Samples 50X-CC and 51X-CC as the boundary of Zones N5/N4. The LAD of *Globigerina ciperoensis* (22.90 Ma) is located between Samples 53X-CC and 54X-CC and represents the Miocene/Oligocene boundary.

The early Oligocene planktonic foraminifers are characterized by *Paragloborotalia nana/opima*, *Turborotalia ampliapertura*, and *G. ciperoensis*. The LAD of *P. opima* (26.93 Ma) is located between Samples 56X-CC and 57-CC as the boundary of Zones P22/P21. The LAD of *T. ampliapertura* (30.28 Ma) is located between Samples 58X-CC and 59X-CC as the boundary of Zones P20/P19.

The relative abundance of planktonic foraminifers decreases below Core 56X, clearly indicating a shallower water environment during the late to early Oligocene.

## Diatoms

The core catcher samples from Hole U1505C were processed into smear and strewn slides for diatom analysis. A total of 28 additional toothpick samples were taken from selected intervals of the working-half cores for better resolution. Samples from the mudline to Sample 3H-CC are composed of between 1% and 50% diatoms
<caption>Table T8. Distribution of diatoms, Site U1505. View table in PDF format. Download available in CSV format.</caption>

<table><caption>Table T9. Diatom events, Site U1505. T = top/last appearance datum. Download available in CSV format.</caption><thead><tr><th rowspan="2">Epoch</th><th rowspan="2">Biozone<br>(Scherer et al., 2007)</th><th rowspan="2">Diatom event</th><th colspan="2">Top</th><th colspan="2">Bottom</th><th colspan="2">Age model</th></tr><tr><th>Core, section,<br>interval (cm)</th><th>Depth<br>CSF-A (m)</th><th>Core, section,<br>interval (cm)</th><th>Depth<br>CSF-A (m)</th><th>Depth<br>(m)</th><th>Age range<br>(Ma)</th></tr></thead><tbody><tr><td>Pleistocene</td><td>Fragilariopsis doliolus</td><td>T Fragilariopsis reinholdii</td><td></td><td></td><td>368-U1505C-<br>3H-3, 31</td><td>20.84</td><td>20.84</td><td>&lt;0.62</td></tr></tbody></table>

with poor preservation (Table T8). The rest of the samples, with the exception of Samples 63X-CC and 64X-CC, were barren of diatoms.

Samples 1H-CC, 2H-CC, and 3H-CC contain a typical late Pleistocene tropical-subtropical diatom assemblage such as *Fragilariopsis doliolus* and *Nitzschia interruptestriata* (Table T9). *Fragilariopsis reinholdii* (LAD = 0.62 Ma) was not observed in Sample 4R-CC, suggesting an age younger than 0.62 Ma.

Smear slides from Samples 63X-CC and 64X-CC are devoid of diatoms, but the washed residues for foraminiferal analysis contain a few specimens of large (~250 µm) heavily recrystallized diatoms that are similar to *Arachnoidiscus* in appearance.

## Paleomagnetism

### Shipboard measurements

Shipboard paleomagnetic investigations on Hole U1505C cores combined two complementary approaches (see **Paleomagnetism** in the Expedition 367/368 methods chapter [Sun et al., 2018]): (1) measurement of archive-half sections on the pass-through 2G Enterprises SRM at 2.5 cm spacing and (2) measurement and AF demagnetization of 55 oriented discrete samples on the spinner magnetometer (AGICO JR-6A). Additionally, the anisotropy of magnetic susceptibility (AMS) was measured on discrete samples with the KLY 4 Kappabridge.

Except for Sections 368-U1505C-1H-1 through 3H-1, which were in-line AF demagnetized in 3 steps (5, 10, and 15 mT), only NRM was measured with the SRM for Hole U1505C. This decision was made after a comparison of magnetization intensities between discrete samples and sections led us to suspect that the SRM was not properly calibrated (geometrically) for core sections. U-channel samples will be collected on shore to analyze and demagnetize this core.

Scalar data from discrete samples from AF demagnetization up to 120 mT were used to assess the nature of the magnetic assemblage and the directional and intensity data. Directional data were analyzed using Zijderveld diagrams (Zijderveld, 1967), and the characteristic remanent magnetization (ChRM) direction(s) were calculated by principal component analysis (PCA) (Kirschvink, 1980) using PuffinPlot (version 1.03, April 23, 2015) (Lurcock and Wilson, 2012).

### Demagnetization behavior and implications for magnetic assemblages

Units: lithostratigraphic Units I and II

Depth: 0.00-480.54 m

Sections 368-U1505C-1H-1 through 64X-CC

Most of the 55 discrete samples investigated show very soft magnetic behavior characterized by loss of more than 60% of NRM below 15 mT. This very low coercivity (soft behavior) is the reason for the strong vertical drilling overprint (average inclination ≈ 81°) that is particularly visible in the APC cores. The drilling overprint is easily removed by demagnetization to 10-15 mT (Figure F17). The soft behavior shows that magnetic remanence is dominated by titanomagnetite or magnetite. The contribution of greigite to the magnetic assemblages is visible in a few discrete specimens between Cores 368-U1505C-11H and 17H through a minute increase in magnetization above 70 mT. The lower part of the hole (Cores 48X through 64X) is characterized by severe drilling disturbance, resulting in destruction of the NRM vector, which is visible in the scatter of inclinations (Figure F18). The drilling overprint affects discrete samples (yellow squares in Figure F19) far less than core sections (blue crosses).

### Magnetostratigraphy

Inclination, intensity, and polarity for Hole U1505C are reported in Figure F19. We constructed the magnetostratigraphy based on the polarity assigned to the archive-half cores and corroborated by directions obtained from oriented discrete samples. A succession of two normal and three reversed polarities was recognized. We tentatively correlated the magnetostratigraphic data of Site U1505C with the standard timescale (Ogg et al., 2016) according to biostratigraphy age constraints as reported in Figure F16. The normal polarity Zone n1 is interpreted as the Brunhes Chron (C1n), with the lower boundary at 37.415 m with an age of 0.781 Ma. The lower boundary (57.365 m) of reversed Polarity r1 is the base of Subchron C1r.3r with an age of 1.778 Ma.

### Anisotropy of magnetic susceptibility

The 55 discrete samples have magnetic susceptibility (κ) values ranging from ≈ 60 × 10⁻⁶ to 628 × 10⁻⁶ SI (Figure F20). These low κ values combined with the low NRM suggest that both paramagnetic silicates (e.g., clays and chlorite) and minor ferromagnetic phases (e.g., titanomagnetite or magnetite) control the magnetic susceptibility. The degree of magnetic anisotropy (P') is moderate (~1.025), whereas the AMS fabric has a strongly oblate fabric, as shown by shape parameter (T), most likely of depositional origin. The Fisher distribution of AMS principal axes also suggests an oblate fabric with a nearly horizontal planar fabric. These sedimentary fabrics are consistent with deposition in a calm, pelagic environment with very limited traction on sedimentary particles.
Figure F17. AF demagnetization plots of (A) archive-half section and (B–D) discrete samples, Hole U1505C sedimentary rocks. Zijderveld plots: solid squares = declination, open squares = inclination. Stereographic plots: solid squares = positive (down) inclination, open squares = negative (up) inclination. Calculated ChRM (blue line; red squares = measurements used in calculation) using PCA is also shown. A. Removal of drilling overprint in first step (5 mT). B. Soft demagnetization behavior up to 10 mT associated with removal of drilling overprint, followed by gradual demagnetization from 10 to 60 mT, characteristic of single-domain and pseudosingle-domain magnetite, and negative inclination of sample. C. Soft demagnetization behavior. D. Soft demagnetization behavior. MAD = maximum angular deviation.

A 368-U1505C-1H-1A, 75 cm, 0.75 m

<figure><img src="image_461.png" /></figure>

B 368-U1505C-6H-4W, 13-15 cm, 50.83 m

<figure><img src="image_462.png" /></figure>

C 368-U1505C-7H-6W, 70-72 cm, 63.90 m

<figure><img src="image_463.png" /></figure>

D 368-U1505C-36F-2W, 60-62 cm, 265.6 m

<figure><img src="image_464.png" /></figure>