<table><caption>**Table T12.** Paleomagnetic age datums, Holes U1564C–U1564F. * = between 66X-4 and 67X. n = normal, r = reverse. Base of magnetic polarities and sections are shown in Figures F50–F53. Polarity subchron and base ages follow Ogg (2020). **Download table in CSV format.**</caption><thead><tr><th>Magnetic polarity</th><th>magnetic polarity CSF-A (m)</th><th>Core, section</th><th>Magnetic polarity</th><th>magnetic polarity CSF-A (m)</th><th>Core, section</th><th>Magnetic polarity</th><th>magnetic polarity CSF-A (m)</th><th>Core, section</th><th>Magnetic polarity</th><th>magnetic polarity CSF-A (m)</th><th>Core, section</th><th>Polarity subchron</th><th>Base of chron/ subchron (Ma)</th></tr></thead><tbody><tr><td>n1</td><td>50.13</td><td>395C-U1564C-6H-4</td><td>n1</td><td>48.10</td><td>395-U1564D-6H-1</td><td>n1</td><td>48.24</td><td>395-U1564E-6H-4</td><td></td><td></td><td></td><td>C1n (Brunhes)</td><td>0.773</td></tr><tr><td>r1</td><td>69.97</td><td>8H-4</td><td>r1</td><td>66.92</td><td>7H-CC-7H-CC</td><td>r1</td><td>67.31</td><td></td><td>8H-4</td><td></td><td></td><td>C1r.1r (Matuyama)</td><td>0.990</td></tr><tr><td>n2</td><td>79.62</td><td>9H-5</td><td>n2</td><td>78.56</td><td>9H-2</td><td>n2</td><td>79.35</td><td></td><td>9H-5</td><td></td><td></td><td>C1r.1n (Jaramillo)</td><td>1.070</td></tr><tr><td>r3</td><td>162.60</td><td>18F-3</td><td>r3</td><td>160.12</td><td>17H-6</td><td>r3</td><td>160.82</td><td></td><td>18H-3</td><td></td><td></td><td>C1r.3r</td><td>1.775</td></tr><tr><td>n4</td><td>196.70</td><td>26F-1</td><td>n4</td><td>196.91</td><td>21H-5</td><td>n4</td><td>195.56</td><td></td><td>21H-7</td><td></td><td></td><td>C2n (Olduvai)</td><td>1.934</td></tr><tr><td>r4</td><td>229.60</td><td>33F-1</td><td>r4</td><td>228.78</td><td>27F-3</td><td>r4</td><td>227.70</td><td></td><td>25X-2</td><td></td><td></td><td>C2r.1r</td><td>2.116</td></tr><tr><td>n5</td><td>233.75</td><td>33F-4</td><td>n5</td><td>232.87</td><td>28F-3</td><td>n5</td><td>231.60</td><td></td><td>25X-5</td><td></td><td></td><td>C2r.1n (Feni)</td><td>2.140</td></tr><tr><td>r5</td><td>294.65</td><td>41X-4</td><td>r5</td><td>301.83</td><td></td><td></td><td>36X-4</td><td></td><td></td><td></td><td></td><td>C2r.2r (Matuyama)</td><td>2.595</td></tr><tr><td>n6</td><td>372.65</td><td>49X-4</td><td>n6</td><td>379.92</td><td></td><td></td><td>45X-2</td><td></td><td></td><td></td><td></td><td>C2An.1n (Gauss)</td><td>3.032</td></tr><tr><td>r6</td><td>378.55</td><td>50X-2</td><td>r6</td><td>388.85</td><td></td><td></td><td>46X-1</td><td></td><td></td><td></td><td></td><td>C2An.1r (Keana)</td><td>3.116</td></tr><tr><td>n7</td><td>403.46</td><td>52X-5</td><td>n7</td><td>403.27</td><td></td><td></td><td>47X-5</td><td></td><td></td><td></td><td></td><td>C2An.2n</td><td>3.207</td></tr><tr><td>r7</td><td>410.12</td><td>53X-3</td><td>r7</td><td>424.88</td><td></td><td></td><td>49X-6</td><td></td><td></td><td></td><td></td><td>C2An.2r (Mammoth)</td><td>3.330</td></tr><tr><td>n8</td><td>463.80</td><td>58X-7</td><td>n8</td><td>466.53</td><td></td><td></td><td>54X-6</td><td></td><td></td><td></td><td></td><td>C2An.3n (Gauss)</td><td>3.596</td></tr><tr><td>r8</td><td>483.20</td><td>60X-7</td><td>r8</td><td>482.57</td><td></td><td></td><td>56X-3</td><td></td><td></td><td></td><td></td><td>C2Ar (Gilbert)</td><td>4.187</td></tr><tr><td>n9</td><td>486.40</td><td>61X-3</td><td>n9</td><td>487.29</td><td></td><td></td><td>56X-7</td><td></td><td></td><td></td><td></td><td>C3n.1n (Cochiti)</td><td>4.300</td></tr><tr><td>r9</td><td>493.80</td><td>62X-1</td><td>r9</td><td>493.64</td><td></td><td></td><td>57X-4</td><td></td><td></td><td></td><td></td><td>C3n.1r</td><td>4.493</td></tr><tr><td>n10</td><td>499.64</td><td>62X-5</td><td>n10</td><td>499.08</td><td></td><td></td><td>58X-1</td><td></td><td></td><td></td><td></td><td>C3n.2n (Nunivak)</td><td>4.631</td></tr><tr><td>r10</td><td>508.41</td><td>63X-4</td><td>r10</td><td>508.08</td><td></td><td></td><td>59X-1</td><td></td><td></td><td></td><td></td><td>C3n.2r</td><td>4.799</td></tr><tr><td>n11</td><td>515.50</td><td>64X-3</td><td>n11</td><td>511.65</td><td></td><td></td><td>59X-3</td><td></td><td></td><td></td><td></td><td>C3n.3n (Sidufjall)</td><td>4.896</td></tr><tr><td>r11</td><td>517.36</td><td>64X-4</td><td>r11</td><td>516.19</td><td></td><td></td><td>59X-7</td><td></td><td></td><td></td><td></td><td>C3n.3r</td><td>4.997</td></tr><tr><td>n12</td><td>528.10</td><td>65X-4</td><td>n12</td><td>522.80</td><td></td><td></td><td>60X-4</td><td></td><td></td><td></td><td></td><td>C3n.4n (Thvera)</td><td>5.235</td></tr><tr><td>r12</td><td>587.77</td><td>71X-5</td><td>r12</td><td>596.85</td><td></td><td></td><td>68X-2*</td><td></td><td></td><td></td><td></td><td>C3r (Gilbert)</td><td>6.023</td></tr><tr><td>n13</td><td>618.68</td><td>74X-7</td><td>n13</td><td>615.15</td><td></td><td></td><td>70X-1</td><td></td><td></td><td></td><td></td><td>C3An.1n</td><td>6.272</td></tr><tr><td>r13</td><td>619.60</td><td>75X-1</td><td>r13</td><td>617.72</td><td></td><td></td><td>70X-3</td><td></td><td></td><td></td><td></td><td>C3An.1r</td><td>6.386</td></tr><tr><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>C3An.2n</td><td>6.727</td></tr><tr><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>C3Ar</td><td>7.140</td></tr><tr><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>C3Bn</td><td>7.214</td></tr><tr><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>C3Br.3r</td><td>7.537</td></tr><tr><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>C4Br.2n</td><td>8.125</td></tr><tr><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>C4Ar.2r</td><td>8.771</td></tr><tr><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>C4Ar.2r</td><td>9.647</td></tr></tbody></table>

# 10. Geochemistry and microbiology

Cores taken during Expeditions 395C (Holes U1564A–U1564C) and 395 (Holes U1564D–U1564F) were analyzed for headspace gas, interstitial water (IW) chemistry, and bulk sediment/basalt geochemistry. The geochemistry of basalts at Site U1564 is described in **Igneous petrology**. Headspace gas analyses were conducted in Holes U1564A–U1564D and U1564F; methane concentrations range between ~0 and 1260 ppmv. Ethane is present at concentrations lower than 94.6 ppmv in Holes U1564C and U1564D and below 510.31 m CSF-A in Hole U1564F. Cores from Holes U1564D–U1564F were analyzed for IW chemistry and bulk sediment geochemistry. IW calcium ion (Ca²⁺) concentrations generally increase with depth, and magnesium ion (Mg²⁺) concentrations decrease. Sulfate ion (SO₄²⁻) concentrations decrease from seawater-like values at the top of the sediment column to <1 mM at 173.87 m CSF-A, with a small increasing trend in concentration below 607.12 m CSF-A. Calcium carbonate (CaCO₃) generally increases downhole, trending from an average of 13.3 ± 9.6 wt% through Sample 395-U1564D-52X-2, 141–151 cm (442.31 m CSF-A), to an average of 35.4 ± 20.6 wt% for the remaining sediment samples to the sediment/basement interface. Bulk sediment generally has low total organic carbon (TOC), total nitrogen (TN), and total sulfur (TS) content.

## 10.1. Volatile hydrocarbons

Methane concentrations throughout the sedimentary section of Site U1564 (Holes U1564A–U1564D and U1564F) increase from 1 ppmv in the shallowest sample (Section 395C-U1564A-1H-3; 3 m CSF-A) to a maximum concentration of 1263 ppmv in the sample from Section 395C-U1564C-35F-3 (~220 m CSF-A). Below that maximum, methane concentrations decrease with
depth but remain above detectable limits with 34.76 ppmv methane measured in the deepest
sample (395-U1564F-52R-2, 140–150 cm) collected from a sediment interval within the basalt at
1050.66 m CSF-A (Figure F57). Ethane is present in Holes U1564C, U1564D, and U1564F below
510.31 m CSF-A; the highest concentration is 94.6 ppmv at 853.14 m CSF-A (Section 395-U1564F-
28R-2).

**10.2. Interstitial water chemistry**

A total of 86 IW samples were squeezed from 5 to 20 cm long whole-round samples from 1.44 to 644.16 m CSF-A in Holes U1564D (Cores 1H-74X), U1564E (mudline), and U1564F (mudline and Cores 6R-22R and 52R). Bottom seawater in Hole U1564F was collected with a Niskin bottle above the sediment/water interface and was also analyzed for water chemistry. In Hole U1564F, the lowermost IW sample was collected from Sample 52R-2, 140-150 cm (1050.66 m CSF-A), which is within a sediment layer between basalts. Selected data acquired from analysis of IW in Holes U1564D and U1564F are shown in Figure F58. pH is near constant throughout the top ~400 m of the sediment column and then increases with depth to 9.039 at 558.67 m CSF-A (Sample 395-U1564F-64X-2, 137-149 cm). Alkalinity varies from near seawater values at the top of the sediment (Sample 395-U1564D-1H-1, 140-150 cm), increases to 10.36 at 145.36 m CSF-A (Sample 16H-2, 140-145 cm), and then decreases to 0.344 in the deepest sampled sediment at 1050.66 m CSF-A (Sample 395-U1564F-52R-2, 140-150 cm). IW Mg²⁺ concentrations range from 50.1 mM in the top sediments at the site (Sample 395-U1564D-1H-1, 140-150 cm) to 1.51 mM at 587.71 m CSF-A (Sample 67X-2, 130-150 cm). SO₄²⁻ concentrations range from 28.2 mM at the top of the

<figure><img src="image_61.png" /><figcaption>**Figure F57.** Composite gas analyses of methane concentrations, Holes U1564A–U1564D and U1564F.</figcaption></figure>

<figure><img src="image_62.png" /><figcaption>**Figure F58.** IW pH, alkalinity, and concentrations of selected ions, Holes U1564D–U1564F.</figcaption></figure>
sediment (Sample 1H-1, 140–150 cm; 1.4 m CSF-A) to 0.5 mM (Sample 28F-2, 145–150 cm; 232.74 m CSF-A). SO₄²⁻ concentrations trend to slightly increasing values below this depth, and the concentration of sulfate in the deepest sediment sample within the basaltic basement (Sample 395-U1564F-52R-2, 140–150 cm; 1050.66 m CSF-A) is 14.0 mM. Ca²⁺ concentrations range from 4.8 mM at 116.93 m CSF-A (Sample 395-U1564D-13H-2, 144–149 cm) to 53.1 mM at 1050.66 (Sample 395-U1564F-52R-2, 140–150 cm) and generally display an opposing trend with Mg²⁺. Sr²⁺ concentrations range from 76.2 µM at 69.47 m CSF-A (Sample 395-U1564D-8H-2, 146–151 cm) to 506.2 µM at 765.53 m CSF-A (Sample 395-U1564F-19R-2, 141–146 cm).

## 10.2.1. Bulk sediment geochemistry

### 10.2.1.1. Carbonate, nitrogen, carbon, and sulfur

Discrete sediment samples (n = 235) were collected from squeeze cake residues and working halves during sediment description of Cores 395-U1564D-1H through 73X (above 646.73 m CSF-A) and 395-U1564F-5R through 41X (below 629.15 m CSF-A) and from Sample 53R-1, 30–35 cm, which was collected from a thin sedimentary interval within basaltic basement. Samples were analyzed for total carbon (TC), TN, sedimentary TS, and total inorganic carbon (TIC). TOC and CaCO₃ were subsequently calculated from the TIC and TC measurements. TOC content is generally below 0.5 wt% (average = 0.27 ± 0.20 wt%; outliers above 1% were excluded; n = 6). CaCO₃ content is variable but increases with depth below ~450 m CSF-A (total range = 0.3–84.8 wt%). The average CaCO₃ content is 31.3 ± 20.8 wt%, and the highest CaCO₃ content was measured near the sediment/basement interface (Figure F59). Additional sediment samples were chosen so that the resulting geochemical information (e.g., CaCO₃ content) could be used to aid in lithologic description. Differences in the CaCO₃ content between the sampling strategies (Figure F59; open versus closed circles or triangles) reflects the sampling bias and variable sedimentary CaCO₃ content in different lithologic layers. TN ranges from below detection limit to 0.10 wt%. TS ranges from below detection limit to 1.91 wt% and is generally below 1.0 wt%.

## 10.3. Microbiology

Microbiological sampling of sediments from Holes U1564D and U1564F was focused on collecting samples for culture-independent approaches. A total of 69 sediment samples from Hole U1564D and 37 sediment samples from Hole U1564F, each 5 cm³, were collected with a sterile cut-end syringe or were aseptically sampled from the interior portion of IW whole-round samples for shore-based analyses. For samples where IW analyses were not conducted because of a lack of available pore water, a 5 cm whole-round sample was collected for microbiological analysis. A total of 36 whole-round samples of basalt were collected in Hole U1564F.

<figure><img src="image_63.png" /></figure>

**Figure F59.** CaCO₃ and TOC, Holes U1564D and U1564F. Open symbols = samples selected from working halves (W) for CaCO₃ to aid in lithologic description from intervals of suspected high CaCO₃ content, solid symbols = IW samples measured from squeeze cake residues.
# 11. Downhole measurements

Details on tools and logging procedures can be found in **Downhole measurements** in the Expedition 395 methods chapter (Parnell-Turner et al., 2025a), and only hole-specific procedures are detailed here. Downhole logging operations at Site U1564 were conducted in Holes 395C-U1564C and 395-U1564F. Hole U1564C was logged with the triple combo tool string (Magnetic Susceptibility Sonde [MSS], High-Resolution Laterolog Array [HRLA], APS, Hostile Environment Litho-Density Sonde [HLDS], and Hostile Environment Natural Gamma Ray Sonde [HNGS]) and the FMS-sonic tool string (FMS, DSI, General Purpose Inclinometry Tool [GPIT], and HNGS) (Table T13). Hole U1564F was logged with the triple combo tool string, FMS-sonic tool string, and UBI tool string (UBI, GPIT, and HNGS). During drilling in Holes U1564C, 395-U1564D, and 395-U1564E, formation temperature measurements were acquired at four depths per hole (Hole U1564C = 54.5, 92.5, 11.5, and 140.0 m DSF; Hole U1564D = 38.0, 66.5, 95.0, and 123.5 m DSF; Hole U1564E = 34.3, 62.8, 91.3, and 119.8 m DSF) using the APCT-3 tool.

## 11.1. Logging procedure and log data processing

### 11.1.1. Hole 395C-U1564C

Hole U1564C downhole logging consisted of a downhole pass (Data Set 016PUP), a repeat uphole logging pass (Data Set 011LUP), and a main uplog pass (Data Set 012LUP) with the triple combo tool string (Table T13). These logging runs were followed by two logging passes with the FMS-sonic tool string, a downhole logging pass (Data Set 038PUP) and the main uphole logging pass (Data Set 025LUP). Hole U1564C was cleaned by circulating the hole with heavy mud (sepiolite and barite), which was then displaced with seawater. The drill pipe was raised to 79 m WSF prior to the downhole logging pass of the triple combo tool string and for all logging runs of the FMS-sonic tool string. For the repeat and main uphole logging passes of the triple combo tool string, the drill pipe was raised slightly higher to 77.5 m WSF. During logging, the wireline heave compensator (WHC) was used to counter the ship's heave, which averaged between 0.25 and 0.5 m. The logging data sets were first depth matched using the natural radiation gamma log from the main uphole logging pass of the triple combo tool string, and then all logs were depth shifted to seafloor, which was determined from the gamma log of the main uphole logging pass of the FMS-sonic tool string (2219 m wireline log matched depth below seafloor [WMSF]). The logging seafloor depth differs by 0.5 m from the driller's seafloor depth (2219.5 m DSF).

<table><caption>**Table T13.** Logging passes in Holes 395C-U1564C and 395-U1564F and APCT-3 in situ formation temperature measurements in Holes 395C-U1564C, 395-U1564D, and 395-U1564E. NA = not applicable. **Download table in CSV format.**</caption><thead><tr><th>Hole</th><th>Tool string</th><th>Tool list</th><th>Logging pass</th><th>Logging data reference</th><th>From depth WMSF (m)</th><th>To depth WMSF (m)</th><th>Pipe depth WMSF (m)</th><th>Notes</th></tr></thead><tbody><tr><td rowspan="6">395C-U1564C</td><td rowspan="3">Triple combo</td><td rowspan="3">MSS-B/HRLA/APS/HLDS/HNGS</td><td>Downlog</td><td>016PUP</td><td>0</td><td>593</td><td>79</td><td>Caliper closed</td></tr><tr><td>Repeat (uplog)</td><td>011LUP</td><td>483</td><td>631</td><td>77.5</td><td>Recorded open hole</td></tr><tr><td>Main (uplog)</td><td>012LUP</td><td>0</td><td>632</td><td>77.5</td><td>Reference pass</td></tr><tr><td rowspan="2">FMS-sonic</td><td rowspan="2">FMS/DSI-2/GPIT/HNGS</td><td>Downlog</td><td>038PUP</td><td>0</td><td>596</td><td>79</td><td>Caliper closed</td></tr><tr><td>Uplog</td><td>025LUP</td><td>0</td><td>629</td><td>79</td><td></td></tr><tr><td>Formation temperature</td><td>APCT-3</td><td>NA</td><td>NA</td><td>26</td><td>140</td><td>NA</td><td>4 measurements (Cores 7H, 10H, 13H, and 15H)</td></tr><tr><td rowspan="10">395-U1564D</td><td>Formation temperature</td><td>APCT-3</td><td>NA</td><td>NA</td><td>38</td><td>123.5</td><td>NA</td><td>4 measurements (Cores 4H, 7H, 10H, and 13H)</td></tr><tr><td>Formation temperature</td><td>APCT-3</td><td>NA</td><td>NA</td><td>34.3</td><td>119.8</td><td>NA</td><td>4 measurements (Cores 4H, 7H, 10H, and 13H)</td></tr><tr><td rowspan="6">Triple combo</td><td rowspan="6">MSS-B/HRLA/APS/HLDS/HNGS</td><td>Downlog</td><td>025PUP</td><td>0</td><td>1160</td><td>55</td><td>Casing to 550 WMSF (m)</td></tr><tr><td>Repeat (uplog)</td><td>026PUP</td><td>1057</td><td>1160</td><td>55</td><td>Casing to 550 WMSF (m)</td></tr><tr><td>Uplog</td><td>027PUP</td><td>0</td><td>1160</td><td>55</td><td>Casing to 550 WMSF (m)</td></tr><tr><td>Downlog</td><td>060PUP</td><td>0</td><td>1169</td><td>55</td><td>Casing to 550 WMSF (m)</td></tr><tr><td>Repeat (uplog)</td><td>039LUP</td><td>539</td><td>1169</td><td>55</td><td>Casing to 550 WMSF (m)</td></tr><tr><td>Uplog</td><td>040LUP</td><td>528</td><td>1169</td><td>55</td><td>Casing to 550 WMSF (m)</td></tr><tr><td rowspan="3">FMS-sonic</td><td rowspan="3">FMS/DSI-2/GPIT/HNGS</td><td>Downlog</td><td>057PUP</td><td>0</td><td>1164</td><td>55</td><td>Casing to 550 WMSF (m)</td></tr><tr><td>Repeat (uplog)</td><td>050LUP</td><td>987</td><td>1164</td><td>55</td><td>Casing to 550 WMSF (m)</td></tr><tr><td>Uplog</td><td>051LUP</td><td>540</td><td>1164</td><td>55</td><td>Casing to 550 WMSF (m)</td></tr><tr><td>UBI</td><td>UBI/GPIT/HNGS</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td><td>NA</td></tr></tbody></table>
The entire length of Hole U1564C is wider than drilling bit size (>12 inches), and caliper data shows the borehole heavily widened or ovalized at various depths. The hole was closest to bit size (~11 inches) between 320 and 630 m WMSF, and intervals of enlargement of as much as 16 inches are observed above 320 m WMSF. Gamma log (HNGS), porosity (APS), and density (HLDS) data were corrected for these observed hole size variations, and APS data were further corrected for tool standoff. Density and porosity data were recorded at sampling intervals of 2.54 and 5.08 cm, respectively, in addition to the standard sampling interval of 15.24 cm. The DSI data between 131 and 593 m WMSF were deemed of acceptable quality by logging data processing carried out by the Lamont-Doherty Earth Observatory Borehole Research Group (LDEO-BRG). Above this depth, interval formation velocities are indistinguishable from that of the drilling mud used during cor- ing. Individual passes of the triple combo and FMS-sonic tool string data were compared to each other and show good repeatability.

### 11.1.2. Hole 395-U1564F

Hole U1564F downhole logging included three logging passes of the triple combo tool string: one downhole logging pass (Data Set 025PUP), and two uphole logging passes (a repeat pass [Data Set 026PUP] and a main pass [Data Set 027PUP]). All tool strings acquired a gamma log through pipe and casing from the seafloor. Because the casing is narrower in diameter than the drill pipe, the collected gamma log data are more reliable than the data collected through the pipe and show good agreement in large- and small-scale features with the open hole gamma log of nearby Hole U1564C. During the triple combo tool string downlog, the MSS malfunctioned, potentially affecting the APS and causing both tools to return unreliable data; therefore, there are no MS or porosity wireline logs for this hole. The FMS-sonic tool string acquired gamma log measurements, $V_p$ and shear wave velocity ($V_s$) data, and a Stoneley wave log in a downhole logging pass (Data Set 060PUP). FMS resistivity image logs were acquired during two uphole logging passes: a main pass (Data Set 039LUP) and a repeat pass (Data Set 040LUP). $V_p$, $V_s$, and Stoneley wave data were only acquired during the downhole logging pass because the DSI was damaged during this logging pass and was unavailable during the uphole logging passes. Finally, logging operations in Hole U1564F ended with the deployment of the UBI tool string, which acquired UBI image logs during a downhole (Data Set 057PUP) and repeat (Data Set 050LUP) pass of the entire basement and sediment-basement transition intervals and an uplog pass (Data Set 051LUP) of the entire open hole. To maximize data collection in the remaining logging time, the UBI tool string downlog and the sediment section of the UBI tool string uplog were collected at a lower resolution, allowing faster logging speeds compared to similar operations in the other holes. The two passes through the basement section and the sediment/basement interface were collected at a similarly high resolution as for the other holes.

## 11.2. Logging units

Logging units for Site U1564 are defined using logging data from Hole U1564C for Logging Unit L1 through Subunit L4a and logging data from Hole U1564F for Subunit L4b through Unit L8. Where the data sets overlap in open hole between 550 and 600 m WMSF, they show good agreement.

### 11.2.1. Logging Unit L1

Depth: 0–108 m WMSF

Unit L1 consists of the depth interval logged through the drill pipe in Hole U1564C and through the casing in Hole U1564F (Subunit L1a), as well as 77–108 m WMSF through open hole in Hole U1564C (Subunit L1b). In Hole U1564F, the bottom of Unit L1 is defined by an increase in the gamma log and an increase in Th measurements from the spectral gamma log, although these signals are not observable in Hole U1564F because the gamma log signals are repressed by the casing.

#### 11.2.1.1. Logging Subunit L1a

Depth: 0–77 m WMSF
Logging data collected in the uppermost 77 m of Hole U1564C were acquired through the drill pipe, and therefore only the suppressed gamma log data can be used to assess borehole lithology. Subunit L1a displays an average gamma radiation signal of ~5.3 ± 2.4 American Petroleum Institute gamma radiation units (gAPI) (Figure F60). Subunit L1a is entirely within Lithostratigraphic Subunit IA (0–135 m CSF-A) (see Lithostratigraphy).

### 11.2.1.2. Logging Subunit L1b

Depth: 77–108 m WMSF

<figure><img src="image_64.png" /><figcaption>**Figure F60.** Downhole logging data, Hole U1564C. in = inches.</figcaption></figure>
The top of Subunit L1b is marked by an increase in the gamma log (up to ~13 ± 3 gAPI) with respect to Subunit L1a due to the transition to the open hole. Resistivity values are invariant with depth in this subunit at ~0.8 Ωm. Density ranges 1.3–1.6 g/cm³, and porosity measurements are between 1.0 and 0.7. V_s averages ~332 m/s. MS typically fluctuates between ~35 and ~160 SI (Figure F60). Subunit L1b is entirely within Lithostratigraphic Subunit IA (see Lithostratigraphy).

### 11.2.2. Logging Unit L2

Depth: 108–318 m WMSF

The boundary between Unit L1 and Unit L2 is defined by an increase in the gamma log (average = 24 ± 5 gAPI) (Figure F60). The spectral gamma log shows several distinct Th peaks (up to ~5 ppm) in Unit L2, and resistivity is generally low (0.5–1 Ωm). Porosity averages 0.9 at 108–155 m WMSF, below which it decreases to an average of 0.6. Density varies between 1.56 and 1.83 g/cm³ throughout this logging unit. V<sub>p</sub> and V<sub>s</sub> steadily increase with depth from 1525 to 1655 m/s and from 300 to 560 m/s, respectively. MS fluctuates in short (2–4 m) wavelength cycles between 40 and 315 SI, with cycle wavelengths becoming longer (6–10 m) in the lowermost ~20 m of this logging unit. Unit L2 corresponds to the lowermost 28 m of Lithostratigraphic Subunit IA and almost the entirety of Lithostratigraphic Subunit IB (136–327 m CSF-A) (see Lithostratigraphy).

### 11.2.3. Logging Unit L3

Depth: 318–519 m WMSF

The top of Unit L3 is marked by a decrease in the gamma log and absence of the cyclical variability of Unit L2 (Figure F60). Two logging subunits are defined by a change in the MS wireline log. Unit L3 corresponds to Lithostratigraphic Subunit IC and the upper portion of Lithostratigraphic Subunit IIA (427–695 m CSF-A) (see Lithostratigraphy).

#### 11.2.3.1. Logging Subunit L3a

Depth: 318–463 m WMSF

Subunit L3a has variable gamma log measurement ranging 12–31 gAPI, the peaks of which are dominated by a high Th count (up to 3.6 ppm), as shown in the spectral gamma log. Deep electrical resistivity is ~0.8 Ωm in this subunit to 423 m WMSF, where a slight decrease to ~0.7 Ωm is observed. This subunit shows a gradual decrease in density with depth from ~1.9 to 1.7 g/cm³, and porosity shows a gradual increase with depth from 0.46 to 0.7. V<sub>p</sub> and V<sub>s</sub> increase throughout the subunit from ~1570 to ~1850 m/s and from ~383 to ~663 m/s, respectively. MS fluctuates throughout this subunit at the meter scale, ranging 24–350 SI.

#### 11.2.3.2. Logging Subunit L3b

Depth: 463–519 m WMSF

Subunit L3b is distinguished from Subunit L3a by the change in scale of fluctuation observed in the MS log, which occurs over submeter scales instead of meter scales. The gamma log and spectral gamma logging responses are similar to Subunit L3a, and deep electrical resistivity remains at 0.7 Ωm, which is consistent with the bottom part of the above Subunit L3a. Density (1.7 g/cm³) and porosity (0.7) in Subunit L3b are similar to those noted for the bottom of Subunit L3a, remaining invariant throughout this subunit. V<sub>p</sub> and V<sub>s</sub> increase with depth, reaching 1970 and 728 m/s, respectively.

### 11.2.4. Logging Unit L4

Depth: 519–700 m WMSF

Unit L4 is distinguished by a marked increase in the gamma log and an increase in spectral gamma K counts compared to the units above and below it (Figures F60, F61). Unit L4 is divided into two subunits and corresponds to the lower portion of Lithostratigraphic Subunit IIA (427–695 m CSF-A).
A) and upper portion of Lithostratigraphic Subunit IIB (695–856 m CSF-A) (see Lithostratigraphy).

### 11.2.4.1. Logging Subunit L4a

Depth: 519–585 m WMSF

The gamma log shows an initial increase and then decrease with depth in Subunit L4a, including an abrupt peak in gamma radiation that correlates to a sharp increase in spectral gamma U counts (~528 m WMSF). The spectral gamma log also shows fluctuations in Th counts similar to those observed in the logging units above it. Compared to the units above and below, deep electrical resistivity shows a slight decrease to between 0.6 and 0.7 Ωm. Density and porosity values are similar to those in Subunit L3b, as are $V_p$ and $V_s$ measurements, although the latter two show a slight increase toward the bottom of this subunit. MS is low in this subunit and lacks the large fluctuations noted in logging units above and below (68 ± 37 SI).

<figure><img src="image_65.png" /><figcaption>**Figure F61.** Downhole logging data, Hole U1564F. in = inches.</figcaption></figure>
#### 11.2.4.2. Logging Subunit L4b

Depth: 585–700 m WMSF

Natural gamma and spectral gamma characters for Subunit L4b are similar to those in Subunit L4a, although more U peaks are noted in the spectral gamma log in this subunit. The top of this subunit is marked by an increase in deep electrical resistivity that fluctuates between 0.7 to 1.2 Ωm, as well as an increase in density and decrease in porosity, both of which also fluctuate in this subunit. $V_p$ and $V_s$ fluctuate slightly at the top of this subunit before becoming relatively invariant with averages of 2035 and 794 m/s, respectively. MS measurements acquired for the top of this subunit (Hole U1564C) show cyclical fluctuating values ranging 13–498 SI.

#### 11.2.5. Logging Unit L5

Depth: 700–847 m WMSF

The top of Unit L5 is marked by a decrease in the gamma log that is matched by decreases in all three spectral gamma log responses (Figures F61). The gamma log measurements still show fluctuations matched to increases and decreases predominantly in the Th but also noted in the U counts from the spectral gamma logs. A deep electrical resistivity measurement of 1.3 Ωm is reported for this logging unit that is invariant with depth, which is in contrast to the fluctuating resistivity character of Subunit L4b. Density, $V_p$, and $V_s$ are also invariant with depth in this logging unit and average 2.1 g/cm³, 2303 m/s, and 1018 m/s, respectively. Unit L5 is entirely within Lithostratigraphic Subunit IIB (see Lithostratigraphy).

#### 11.2.6. Logging Unit L6

Depth: 847–962 m WMSF

The top of Unit L6 is marked by a sharp increase in the gamma log compared to Unit L5 that is reflected in the increase in K, U, and Th counts from the spectral gamma log (Figure F61). In Unit L6, the gamma log fluctuates, with peaks and troughs ranging 15–81 gAPI. Peaks in gamma radiation are related to either peaks in U, Th, or both measurements on the spectral gamma log, and a specifically high peak in gamma log is noted at the bottom of Unit L6, which sees sharp increases in all three spectral gamma log measurements (~960 m WMSF). Deep electrical resistivity, density, $V_p$, and $V_s$ are invariant with depth in Unit L6 with average values of 1.5 ± 0.2 Ωm, 2.23 ± 0.04 g/cm³, 2542 ± 120 m/s, and 1173 ± 94 m/s, respectively. Unit L6 covers the lower portion of Lithostratigraphic Subunit IIB and the uppermost 35 m of Lithostratigraphic Subunit IIC (see Lithostratigraphy).

#### 11.2.7. Logging Unit L7

Depth: 962–1000 m WMSF

The boundary between Unit L7 and Unit L6 is marked by sharp changes in most of the logging data recorded (Figure F61). The gamma log decreases and is mirrored by decreases in the spectral gamma counts, and formation resistivity, density, $V_p$, and $V_s$ increase compared to values in Unit L6. There is variation with depth in all logging responses, and there are fluctuations in the gamma log (3.6–34.1 gAPI) reflecting variable decreases and increases in U and Th counts from the spectral gamma log. Internal unit changes in gamma log are mirrored by formation resistivity, where the lower gamma readings from the top of the unit show increased resistivity and the higher gamma readings in the lower interval of Unit L7 show decreased resistivity. Density fluctuates between 2.3 and 2.8 g/cm³, $V_p$ fluctuates between 2440 and 5164 m/s, and $V_s$ fluctuates between 938 and 2562 m/s. Unit L7 is entirely within Lithostratigraphic Subunit IIC (see Lithostratigraphy).

#### 11.2.8. Logging Unit L8

Depth: 1000–1160 m WMSF

The top of Unit L8 is marked by a large drop in the gamma log, a large increase in resistivity, and increases in density, $V_p$, and $V_s$ where the wireline tools record the transition from sediments into
the basaltic basement in Hole U1564F (Figure F61). The wireline responses in Unit L8 (the basement logging unit) are variable, reflecting the presence of intercalated sediments within the lavas as reported during core logging (see **Igneous petrology**). In basaltic sections of the logging unit, the gamma log values can be as low as 1 gAPI, with the gamma signal dominated by U and in places the K counts from the spectral gamma log. In the intercalated sediments, gamma log measurements show peaks as high as 40.3 gAPI, which are instead dominated by Th counts from the spectral gamma log, similar to sediment gamma measurements in the sedimentary logging units lying above the basement. The intercalated sediments and lavas are also observed from the formation resistivity logs, with basalt lava showing high resistivity (up to 150 Ωm) and sediments showing lower resistivity (as low as 1.4 Ωm). In basalt intervals, formation resistivity shows separation between shallow and deep measurements. Density, $V_s$, and $V_p$ logs all show decreased values for sediment intervals and increased values for basalt intervals.

## 11.3. Borehole imaging

The image logs from Hole U1564C are of good quality (Figures F62, F63). The data collected in the sedimentary section in Hole U1564C show distinct alternating layers of higher and lower resistivity throughout the logging interval. FMS image logs of the sediments and basalt lavas logged in Hole U1564F are of excellent quality (Figure F61), showing alternating conductive and resistive layers in the sedimentary units. In addition, structural features such as fractures in the basalt lavas are resolved in detail, and somewhat intercalated layers of sediment in the basaltic basement are clearly defined. UBI image logs from Hole U1564F are variable in quality. In the sedimentary parts of the hole, image quality is poor and few geologic features are observable, although in places alternating high- and low-amplitude layering is noted. UBI image quality improves with depth, and more geologic features are observable, particularly from Unit L6 and deeper. In the basaltic basement (Unit L8), UBI image quality improves but still suffers from significant image log artifacts,

<figure><img src="image_66.png" /><figcaption>**Figure F62.** Wireline FMS data, Hole U1564C. in = inches.</figcaption></figure>
which obscure the clear observation of geologic features. Despite this issue, a number of geologic features are observable in the basaltic layers of the basement, which may represent fracturing. The UBI image log contains a large number of stick and pull artifacts, which are the main reason for the poor image log quality.

**11.4. Downhole temperature and thermal conductivity**

During drilling in Holes U1564C–U1564E, downhole temperature measurements were taken with the APCT-3 tool in Unit L1 and the uppermost portion of Unit L2 (Figures F64; Table T14). The

<figure><img src="image_67.png" /><figcaption>**Figure F63.** Wireline image data, Hole U1564F. in = inches.</figcaption></figure>
<figure><img src="image_68.png" /><figcaption>**Figure F64.** APCT-3 temperature-time series and projected formation temperature estimates, Holes U1564C–U1564E. Colored lines = observed temperature-time series, dashed lines = modeled heat pulse decay function (Hartmann and Villinger, 2002), colored dots = formation temperatures projected using a best-fitting heat pulse decay function. Time is normalized with respect to onset of heat pulse decay model.</figcaption></figure>

<table><caption>**Table T14.** Downhole logging units, Site U1564. Download table in CSV format.</caption><thead><tr><th>Logging unit</th><th>Depth WMSF (m)</th><th>Lithology</th></tr></thead><tbody><tr><td>L1a</td><td>0–77</td><td>Sediment (through drill pipe)</td></tr><tr><td>L1b</td><td>77–108</td><td>Sediment</td></tr><tr><td>L2</td><td>108–318</td><td>Sediment</td></tr><tr><td>L3a</td><td>318–463</td><td>Sediment</td></tr><tr><td>L3b</td><td>463–519</td><td>Sediment</td></tr><tr><td>L4a</td><td>519–585</td><td>Sediment</td></tr><tr><td>L4b</td><td>585–700</td><td>Sediment</td></tr><tr><td>L5</td><td>700–847</td><td>Sediment</td></tr><tr><td>L6</td><td>847–962</td><td>Sediment</td></tr><tr><td>L7</td><td>962–1000</td><td>Sediment</td></tr><tr><td>L8</td><td>1000–1160</td><td>Basalt</td></tr></tbody></table>
APCT-3 tool provided equilibration temperatures ranging from 6.07°C at 34.3 m DSF to 15.63°C at 130 m DSF (Figure F65A; Table T15). These measurements provide a thermal gradient in the upper sediment section of 36°C/km. Thermal conductivity under in situ conditions (K) was estimated from the combined laboratory-determined thermal conductivity measurements from Holes U1564D and U1564E using the method of Hyndman et al. (1974) (Figure F65B). The ther-

<figure><img src="image_69.png" /></figure>

**Figure F65.** Thermal gradient and heat flow estimates, Site U1564. A. Projected APCT-3 formation temperature in Holes U1564C-U1564E (open circles, diamonds, and triangles, respectively), gray line = linear least-squares fit, T(z) = thermal gradient. B. Observed thermal conductivity. C. Calculated thermal resistance (R) (black dots). Gray line = linear least-squares fit for resistance as a function of depth, R(z). D. Temperature as a function of thermal resistance (black dots) (i.e., Bullard plot). Gray line = linear least-squares fit, the gradient of which is vertical heat flow (q).

<table><caption>**Table T15.** APCT-3 measurements, Holes 395C-U1564C, 395-U1564D, and 395-U1564E. Download table in CSV format.</caption><thead><tr><th>Core</th><th>Depth DSF (m)</th><th>Formation temperature (°C)</th></tr></thead><tbody><tr><td colspan="3">395C-U1564C-</td></tr><tr><td>7H</td><td>54.5</td><td>8.65</td></tr><tr><td>10H</td><td>92.5</td><td>11.45</td></tr><tr><td>13H</td><td>111.5</td><td>13.93</td></tr><tr><td>15H</td><td>140</td><td>15.63</td></tr><tr><td colspan="3">395-U1564D-</td></tr><tr><td>4H</td><td>38</td><td>6.35</td></tr><tr><td>7H</td><td>66.5</td><td>8.86</td></tr><tr><td>10H</td><td>95</td><td>11.62</td></tr><tr><td>13H</td><td>123.5</td><td>13.09</td></tr><tr><td colspan="3">395-U1564E-</td></tr><tr><td>4H</td><td>34.3</td><td>6.07</td></tr><tr><td>7H</td><td>62.8</td><td>8.53</td></tr><tr><td>10H</td><td>91.3</td><td>11.16</td></tr><tr><td>13H</td><td>119.8</td><td>13.74</td></tr></tbody></table>
mal conductivity of the sediment measures between ~0.7 and ~1.2 W/(m·K). A linear function for depth-dependent thermal resistance (R) was obtained by integrating the inverse of the thermal conductivity over depth and applying a linear least-squares fit (Figure F65C). This function was used to estimate thermal resistance at each corresponding APCT-3 downhole temperature measurement depth. A heat flow of 33.5 mW/m² was obtained from a linear least-squares fit of the relationship between temperature and thermal resistance (Bullard, 1939), whose slope is the vertical heat flow (Figure F65D).

## 12. Age model

Seismic reflection profiles for Site U1564 show a relatively flat and laterally continuous series of reflections (see **Background and objectives**). The age model (Figure F66) is based mainly on a combination of paleomagnetic and biostratigraphic age determinations from Holes 395-U1564D and 395-U1564F with additional biostratigraphic constraints from Hole 395C-U1564C (see **Paleo-magnetism** and **Micropaleontology**). A list of age model tie points with interpolated ages for lithostratigraphic unit boundaries and the estimated depths of epoch and subepoch boundaries is given in Table T16.

Hole U1564D yielded an excellent series of paleomagnetic reversals to the base of Chron C3An.1r (6.386 Ma). This record is in good agreement with biostratigraphic age constraints from calcareous nannofossils and planktonic foraminifers. The paleomagnetic reversal succession continues downward through the upper part of Hole U1564F to the base of Subchron C4Ar.2r (9.647 Ma) at

<figure><img src="image_70.png" /><figcaption>**Figure F66.** Age model for the sedimentary succession, Holes U1564D and U1564F. Additional biostratigraphic constraints from Hole U1564C are shown.</figcaption></figure>
734.43 m CSF-A. Below this depth, a substantial magnetic drilling overprint prevents the identification of paleomagnetic reversals (see **Paleomagnetism**).

The paleomagnetic age model tie points help divide the stratigraphy into a series of intervals characterized by variations in estimated sedimentation rates. From the top of the hole to the Jaramillo Chron (1.070 Ma) at 78.56 m CSF-A, the average sedimentation rate is ~7.3 cm/ky. From this depth to the base of Gauss Subchron C2An.1n (3.596 Ma) at 466.53 m CSF-A, the average sedimentation rate is ~15.3 cm/ky. From this depth to the base of Thvera Subchron C3n.4n (5.235 Ma) at 522.80 m CSF-A, the average sedimentation rate is much lower (~3.4 cm/ky). From the base of Subchron C3n.4n to the base of Chron C3Ar (7.14 Ma) at 643.48 m CSF-A, the average sedimentation rate is ~6.3 cm/ky.

The age model for the lower part of the succession from ~730 m CSF-A to the igneous basement at 997.23 m CSF-A is based on selected biostratigraphic tie points. The average sedimentation rate declines downhole. From the base of Chron C3Ar (7.14 Ma) at 643.48 m CSF-A to the top of *S. heteromorphus* (13.60 Ma) at 783.65 m CSF-A, the average sedimentation rate is ~2.2 cm/ky. From this depth to the top common occurrence of *C. cubensis* (27.29 Ma) at 974.69 m CSF-A, the average sedimentation rate is ~1.4 cm/ky. From this depth to the top common occurrence of *R. umbilicus* (32.02 Ma) at 986.61 m CSF-A, the average sedimentation rate is ~0.3 cm/ky.

The age of the sediment in the lowermost part of the regular succession above igneous basement is lower Oligocene (between 32.02 and 32.20 Ma). This finding is in good agreement with the age of the basement estimated from regional magnetic surveys at 32.4 Ma (see **Background and objectives**). A further ~4 m thick nannofossil chalk unit occurs at 1049.25–1053.09 m CSF-A between basaltic flows in Core 395-U1564F-52R (see **Igneous petrology**). The chalk appears bedded and bioturbated and is therefore likely to have been deposited on the seafloor rather than injected into subseafloor fissures. Biostratigraphic evidence suggests that this sediment is also lower Oligocene but slightly older than that found at the base of the regular succession, having been deposited between 32.20 and 35.8 Ma (see **Micropaleontology**).

<table><caption>**Table T16.** Age model tie points and interpolated boundaries, Site U1564. Tc = top common. **Download table in CSV format.**</caption><thead><tr><th>Tie point</th><th>Hole</th><th>Event (base)</th><th>Age (Ma)</th><th>Depth CSF-A (m)</th></tr></thead><tbody><tr><td></td><td>395-</td><td></td><td></td><td></td></tr><tr><td>1</td><td>U1564D</td><td>Top of hole</td><td>0.000</td><td>0.00</td></tr><tr><td>2</td><td>U1564D</td><td>C1n (Brunhes)</td><td>0.773</td><td>48.10</td></tr><tr><td>3</td><td>U1564D</td><td>C1r.1n (Jaramillo)</td><td>1.070</td><td>78.56</td></tr><tr><td></td><td></td><td>Lithostratigraphic Subunit IA</td><td>1.44</td><td>135.93</td></tr><tr><td></td><td></td><td>Base Pleistocene</td><td>2.59</td><td>311.48</td></tr><tr><td></td><td></td><td>Lithostratigraphic Unit IB</td><td>2.69</td><td>326.71</td></tr><tr><td>4</td><td>U1564D</td><td>C2An.2r (Mammoth)</td><td>3.330</td><td>424.88</td></tr><tr><td></td><td></td><td>Lithostratigraphic Subunit IC</td><td>3.34</td><td>426.20</td></tr><tr><td>5</td><td>U1564D</td><td>C2An.1n (Base upper Pliocene)</td><td>3.596</td><td>466.53</td></tr><tr><td>6</td><td>U1564D</td><td>C3n.4n (Thvera)</td><td>5.235</td><td>522.80</td></tr><tr><td></td><td></td><td>Base Pliocene</td><td>5.33</td><td>531.53</td></tr><tr><td>7</td><td>U1564F</td><td>C3An.1r</td><td>6.386</td><td>628.58</td></tr><tr><td>8</td><td>U1564F</td><td>C3Ar</td><td>7.140</td><td>643.48</td></tr><tr><td>9</td><td>U1564F</td><td>C4r.2r</td><td>8.771</td><td>692.69</td></tr><tr><td></td><td></td><td>Lithostratigraphic Unit IIA</td><td>8.82</td><td>694.90</td></tr><tr><td>10</td><td>U1564F</td><td>C4Ar.2r</td><td>9.647</td><td>734.43</td></tr><tr><td></td><td></td><td>Base upper Miocene</td><td>11.65</td><td>759.37</td></tr><tr><td>11</td><td>U1564F</td><td>Top Sphenolithus heteromorphus</td><td>13.60</td><td>783.65</td></tr><tr><td></td><td></td><td>Base middle Miocene</td><td>15.99</td><td>817.00</td></tr><tr><td></td><td></td><td>Lithostratigraphic Subunit IIB</td><td>18.80</td><td>856.19</td></tr><tr><td></td><td></td><td>Base Miocene</td><td>23.04</td><td>915.38</td></tr><tr><td>12</td><td>U1564F</td><td>Tc Chiloguembelina cubensis</td><td>27.29</td><td>974.69</td></tr><tr><td></td><td></td><td>Base upper Oligocene</td><td>27.29</td><td>974.69</td></tr><tr><td>13</td><td>U1564F</td><td>Top Reticulofenestra umbilicus</td><td>32.02</td><td>986.61</td></tr><tr><td></td><td></td><td>Lithostratigraphic Unit IIC</td><td>&lt;33.8</td><td>997.23</td></tr></tbody></table>
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