|
Core, section |
Depth (mbsf) | Unit/Subunit |
Eruption unit* |
Unit name | Thickness (m) |
Position of unit boundaries in core |
Lava type (inferred) |
Lobes/ subunits (number) |
Notes | ||
|---|---|---|---|---|---|---|---|---|---|---|---|
Top
|
Bottom
|
Curated
|
Calculated
|
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| 197-1206A- | |||||||||||
| 1W | 0.00 | 57.00 | SEI | Fossiliferous vitric-lithic sandstone and breccia | 2.31 | 57.00 | The base of Sedimentary Unit 1 is inferred to be at 57.0 mbsf. | Resedimented volcaniclastics rich on unaltered lapilli tephra clast | Sandstone matrix-supported lapilli breccia consisting of basalt lava lithic and unaltered tephra fragments. | ||
| 2R-1 to 4R-5 | 57.00 | 75.10 | 1 | I | Sparsely to moderately olivine-phyric basalt | 14.67 | 16.40 | The top of Unit 1 is taken to be at 57.0 mbsf. The Unit 1/2 boundary is inferred to be at 73.4 mbsf (midway between Sections 4R-5 and 5R-1). | Compound pahoehoe | 13 | Highly vesicular lava with three-fold division and smooth glassy pahoehoe surfaces. |
| 5R-1 to 6R-1 | 75.10 | 87.21 | 2a-2c | I | Hyaloclastite olivine-basalt breccia | 6.78 | 13.81 | The top of Unit 2 is at 73.4 mbsf. The Unit 2/3 boundary is in Section 7R-2 (87.21 mbsf). | Flow-foot breccia to Unit 1 | 1 | Hyaloclastite breccia formed by disintegration of lava by quenched fragmentation upon contact with water intercalated with small pillowlike lobes. This unit represents a classic lava delta sequence. |
| 7R-2 | 87.21 | 87.33 | 3 | Coralline limestone | 0.12 | 0.12 | Thin limestone interbed. The Unit 3/4 boundary is in Section 7R-2 (87.33 mbsf). | Benthic foraminifers—nearshore environment. | |||
| 7R-2 to 14R-2 | 87.33 | 126.65 | 4 | II | Sparsely to highly olivine-phyric basalt | 11.57 | 39.32 | The Unit 4/5 boundary is inferred to be at 126.65 mbsf (midway between Sections 14R-2 and 15R-1). Paleomagnetic reversal across Core 8R to 9R?? | Compound pahoehoe | >12 | Highly vesicular lava with three-fold division and smooth glassy pahoehoe surfaces. It is possible that there is more than one eruption unit in this interval. |
| 15R-1 to 16R-1 | 126.65 | 133.72 | 5 | III | Moderately olivine-plagioclase-phyric basalt | 4.14 | 7.07 | The Unit 5-6 contact is defined by a flow boundary (thin flow base breccia) at Section 16R-1, 52 cm. | A'a lava? | 1 | Strongly flow-foliated lava with thin basal breccia. |
| 16R-1 to 19R-1 | 133.72 | 155.00 | 6 | IV | Moderately to highly olivine-phyric basalt | 12.42 | 21.28 | The Unit 6-7 contact is defined by a distinct change in igneous lithology across lobe margins at Section 19R-1, 120 cm. | Compound pahoehoe | >14 | Highly vesicular lava with three-fold division and smooth glassy pahoehoe surfaces. This interval most likely consists of two eruption units. |
| 19R-1 to 21R-1 | 155.00 | 172.00 | 7 | V | Aphyric to moderately olivine-phyric basalt | 9.32 | 17.00 | The Unit 7-8 contact is defined by a distinct change in volcanic lithology at Section 21R-1, 20 cm. | Compound pahoehoe | 5 | Highly vesicular lava with three-fold division and smooth glassy pahoehoe surfaces. |
| 21R-1 to 22R-3 | 172.00 | 184.73 | 8a-8o | V | Hyaloclastite olivine basalt breccia and moderately olivine-phyric basalt | 10.06 | 12.73 | The primary depositional contact between Units 8 and 9 is at Section 22R-3, 33 cm. | Flow-foot breccia to Unit 7, composed of hyaloclastite breccia and intercalated pillow lava horizons | 15 | Classic lava delta sequence. Hyaloclastite breccia formed by disintegration of lava by quenched fragmentation upon contact with water and pillows by lava advancing directly into the sea. |
| 22R-3 | 184.73 | 185.42 | 9 | Volcaniclastic and sedimentary interbed | 0.69 | 0.69 | The primary contact between Units 9 and 10 is at Section 22R-3, 103 cm. | Bedded lithic-vitric sandstone and gravelstone overlying limestone | Coarse-grained nature, cross-bedding, and presence of fossil shell fragments and benthic foraminifers indicate a high-energy nearshore environment. The low maturity of the clast population is indicative of high sedimentation rates. | ||
| 22R-3 to 25R-2 | 185.42 | 206.15 | 10 | VI | Aphyric to sparsely olivine-phyric basalt | 12.91 | 20.73 | The Unit 10/11 boundary is inferred to be at 206.15 mbsf (midway between Sections 25R-2 and 26R-1). | Compound pahoehoe | 5 | Highly vesicular lava with three-fold division and smooth glassy pahoehoe surfaces. |
| 26R-1 to 30R-2 | 206.15 | 240.93 | 11a-11ae | VI | Hyaloclastite basalt breccia and aphyric to sparsely olivine-phyric basalt | 15.85 | 34.78 | The primary depositional contact between Units 11 and 12 is at Section 30R-2, 23 cm. | Flow-foot breccia to Unit 10, composed of hyaloclastite breccia and intercalated pillow lava horizons | 31 | Classic lava delta sequence. Hyaloclastite breccia formed by disintegration of lava by quenched fragmentation upon contact with water and pillows by lava advancing directly into the sea. |
| 30R-2 to 31R-1 | 240.93 | 249.00 | 12 | Calcareous lithic-vitric sandstone | 3.81 | 8.07 | The Unit 12/13 boundary is placed at Section 31R-1 (Piece 2, 10 cm); detrital limestone on lava. | Sedimentary interbed | Epiclastic sandstone overlying a thin detrital limestone interval. Nearshore depositional environment. | ||
| 31R-1 | 249.00 | 253.70 | 13 | VII | Aphyric to sparsely olivine-phyric basalt | 1.07 | 1.07 | The Unit 13/14 boundary is inferred to be at 253.7 mbsf (midway between Sections 31R-1 and 32R-1). | Not possible to determine due to poor recovery | ||
| 32R-1 to 34R-2 | 253.70 | 271.41 | 14a-14e | VII | Hyaloclastite basalt breccia and sparsely olivine-phyric basalt | 15.85 | 21.34 | The primary depositional contact between Units 14 and 15 is at Section 34R-2, 6 cm. | Flow-foot breccia to Unit 13, composed of hyaloclastite breccia and intercalated pillow lava horizons | 5 | Classic lava delta sequence. Hyaloclastite breccia formed by disintegration of lava by quenched fragmentation upon contact with water and pillows by lava advancing directly into the sea. |
| 34R-2 | 271.41 | 272.45 | 15 | Calcareous grainstone | 0.98 | 1.04 | The Unit 15/16 boundary is at Section 34R-2, 104 cm; conformable depositional contact. | Sedimentary interbed | Epiclastic sandstone overlying a thin detrital limestone interval. | ||
| 34R-2 to 36R-2 | 272.45 | 289.01 | 16 | Volcaniclastic grainstone | 14.48 | 16.56 | The Unit 16/17 boundary is placed at the top of Section 36R-3. | Sedimentary interbed | Epiclastic sandstone. Nearshore depositional environment. | ||
| 36R-3 to 40R-1 | 289.01 | 307.54 | 17a-17b | VIII | Highly olivine-phyric basalt | 18.58 | 18.53 | The primary depositional contact between Units 14 and 15 is at Section 40R-3, 104 cm. | A'a | 2 | Picrite basalt. |
| 40R-1 to 40R-3 | 307.54 | 309.88 | 18a | Red-brown weathered flow top with moderately olivine-phyric basalt clasts | 2.33 | 2.34 | The Unit 18a/18b boundary is inferred to be at the top of Section 40R-4. | Deeply weathered flow-top rubble | Deeply weathered flow top containing relict and slightly altered spinose and jagged clinker clasts of aphanitic sparsely olivine-phyric basalt. | ||
| 40R-4 to 41R-2 | 309.88 | 313.00 | 18b | IX | Aphyric basalt | 3.06 | 3.12 | The primary contact between Units 18b and 19 is at Section 41R-2, 43 cm. | A'a | 1 | Aphyric basalt containing microphenocrysts? |
| 41R-2 to 41R-3 | 313.00 | 315.04 | 19 | Volcaniclastic basalt breccia | 2.04 | 2.04 | The primary contact between Units 19 and 20 is at Section 41R-3, 100 cm. | A'a | Epiclastic breccia (i.e., resedimented basalt detritus). | ||
| 41R-3 | 315.04 | 315.19 | 20 | Volcaniclastic sandstone | 0.15 | 0.15 | The primary depositional contact between Units 20 and 21 is placed at Section 41R-3, 115 cm. | Sedimentary interbed | Epiclastic sandstone. Nearshore depositional environment. | ||
| 41R-3 to 45R-2 | 315.19 | 331.68 | 21 | X | Sparsely olivine-plagioclase-phyric basalt | 2.04 | 16.49 | The primary depositional contact between Units 21 and 22 is at Section 45R-2, 68 cm. | A'a | Flow-top rubble infiltrated by sand from the above sediment unit. | |
| 45R-3 to 45R-2 | 331.68 | 335.20 | 22 | Calcareous lithic-vitric sandstone | 1.76 | 3.52 | Unit 22 is the deepest, so there is no contact at its base (not reached). | Sedimentary interbed | Epiclastic sandstone. Nearshore depositional environment. | ||
Notes: * = lava units formed in the same eruption.