|
Hole
|
BSR
depth (m) |
Depth range
of RAB or IR (m) |
Estimated hydrate from proxy in GHOZ/GHSZ (%)
|
|||
|---|---|---|---|---|---|---|
|
IR*
|
PCS*
|
Cl–*
|
RAB
|
|||
| Hydrate Ridge—away from summit | ||||||
| 204- | ||||||
| 1244B | 124 |
|
|
|
|
8.1/6.1 |
| 1244C | 124 | 45–125 | 3.2/2.0 | 0/0 | 2.2/2 |
|
| 1244E | 124 | 23–121 | 2.6/2.1 | 0.9/1.4 | 3.5/1.8 |
|
| 1245A | 134 |
|
|
|
|
3.1/1.9 |
| 1245B | 134 | 52–119 | 3.8/1.9 |
|
3.0/2.0 |
|
| 1245C | 134 | 44–120 | 2.9/1.6 | 4.0/6.0 |
|
|
| 1246A | 114 |
|
|
|
|
1.5/1.0 |
| 1246B | 114 | 16–117 | 5.6/5.0 |
|
2.3/1.7 |
|
| 1247A | 124 |
|
|
|
|
2.0/1.6 |
| 1247B | 130 | 16–116 | 1.9/1.5 | 1.3/2.6 | 1.5/0.8 |
|
| Hydrate Ridge—summit | ||||||
| 204- | ||||||
| 1248A | 115 |
|
|
|
|
17/7 |
| 1248C | 115 | 1–124 | 7.3 |
|
4.5 |
|
| 115 | 1–30 | 18 |
|
NB |
|
|
| 1249A | 115 |
|
|
|
|
73/75 |
| 1249F | 115 | 1–88† | 13.9 | 23 | NB |
|
| 115 | 1–30 | 23.6 | 43 | NB |
|
|
| 115 | 30–88 | 11.8 | 4.6 | 2 |
|
|
| 1250A | 114 |
|
|
|
|
26/5 |
| 1250C | 114 | 14–109 | 2.6 | 0.7 | 4.3 |
|
| 114 | 1–14 |
|
|
NB |
|
|
| 1250D | 114 | 7–114 | 1.8 | 1.4 |
|
|
| Slope basin | ||||||
| 204- | ||||||
| 1251A | 200 |
|
|
|
|
1.2/1.0 |
| 1251B | 200 | 41–188 | 1.6/1.2 | 0.5/0.5 | BD |
|
| 1251D | 200 | 34–205 | 5.2/4.5 | 0.2/0.2 | 2.8/1.7 |
|
| 1252A | 170 | 19–183 | 1.9/1.3 |
|
BD |
|
Notes: Table adapted from Tréhu et al. (2004a). * = corrected for percent recovery. Average gas hydrate content from infrared (IR) data was calculated as discussed in Tréhu et al. (2004a). Results are shown for integration over the gas hydrate occurrence zone (GHOZ), defined as the depth range over which indicators for gas hydrate were observed, and for the gas hydrate stability zone (GHSZ), defined as the region from the seafloor to the bottom-simulating reflector (BSR). At Site 1252, the projected depth of the BSR was used. For the summit region, the GHOZ and the GHSZ are the same because indicators of gas hydrate presence extend from the BSR to the seafloor. At these sites, the gas hydrate content of the shallow zone of massive hydrate is given separately. Each pressure core sampler (PCS)-derived result represents the average of 1–3 samples spaced at unequal intervals, each averaging gas hydrate content over ~1 m. No PCS data were acquired in Holes 1245B, 1246B, 1248C, or 1252A. Measurement uncertainties are discussed elsewhere. Chloride-derived estimates represent averages of 1–30 samples/hole spaced at unequal intervals, each averaging gas hydrate content over 5–10 cm of core length. Uncertainties due to uncertainties in the baseline are estimated to be ±0.5%. BD = any hydrate present was below the detection level of this technique. NB = no baseline could be estimated because of anomalously high Cl– concentration. Resistivity-at-the-bit (RAB)-derived averages were calculated from pore water saturation estimates based on electrical resistivity data and tabulated at ~15-cm intervals and include hundreds of data points. These data require no correction for core recovery. No RAB data were acquired at Site 1252. RAB data are from the "A" hole at all sites, except from Site 1244, where they are from the "B" hole. Holes characterized by RAB data are ~50 m away from other holes at that site. All measurements in the GHOZ or GHSZ were included in the average, including data points indicating no gas hydrate. † = 88 mbsf is the depth at the bottom of this hole, which is ~24 m above the BSR.