Core, section
|
Unit/Subunit
|
Unit name
|
Position of unit boundaries and comments
|
|---|---|---|---|
| 197-1205A- | |||
| 1R to 5R-1 | SEI | Fossilferous sandstone | The base of sedimentary Unit I is inferred to be at Section 5R-1, 62 cm. |
| 5R-2 | SEII | Conglomerate | The base of sedimentary Unit II is inferred to be at the bottom of Section 5R-2. |
| 6R-1 to 6R-2 | 1 | Moderately to highly plagioclase-phyric basalt | The base of Unit 1 is at Section 6R-3, 74 cm. |
| 6R-3 | 2 | Red soil | About 7 cm of red-brown soil was recovered at the base of Section 6R-3. Large increases in the rate of penetration at this depth may indicate the presence of a soil horizon of substantial thickness. The base of Unit 2 is between Sections 6R-3 and 7R-1. Part of the soil and flow-top breccia were not recovered. |
| 7R-1 to 7R-2 | 3a | Olivine-plagioclase-phyric basalt autoclastic breccia | Agglutinated autoclastic breccia from the lower part of the flow-top rubble. |
| 7R-2 to 14R-3 | 3b | Sparsely to moderately olivine-plagioclase-phyric basalt | Glassy lobe margins and soil on the bottom piece of Section 14R-3 defines the base of Unit 2. |
| No recovery | Part of the vitric sandstone and associated soils were not recovered. | ||
| 15R-1 | 4 | Reddish brown vitric sandstone | Laminated volcaniclastic sandstone. Unit 4 is a 0.25-m-thick interval at the top of Section 15R-1. |
| 15R-1 | 5a | Red soil | Piece 3 contains ~8 cm of grayish red silty clay (soil) situated above the smooth glassy flow top of Unit 5b. |
| 15R-1 to 17R-1 | 5b | Moderately plagioclase-olivine-phyric basalt | The base of Unit 5b is in Section 17R-1. |
| 17R-1 | Red soil | There is a fragment of oxidized silty clay adhering to coherent basalt in Piece 10. | |
| 17R-1 to 19R-4 | 6 | Moderately plagioclase-olivine-phyric basalt | The upper boundary is a weathered flow top in Section 17R-1. The base of Unit 6 is at the top of Section 19R-4. |
| 19R-4 | 7 | Red-brown soil | Unconsolidated red-brown silty clay mixed with angular (broken by drilling) lava fragments. Large increases in the rate of penetration at this depth may indicate the presence of a soil horizon of substantial thickness. The base of Unit 7 is in Section 19R-4. |
| 19R-4 to 21R-2 | 8a | Moderately plagioclase-olivine-phyric basalt | The base of Unit 8a is in Section 21R-2. |
| 21R-2 | 8b | Plagioclase-olivine basalt autoclastic breccia | Basal flow rubble. The base of Unit 8b is in Section 21R-2. |
| 22R-2 | Break in lava accumulation (soil?) | The unit boundary is indicated by presence of flow-base breccia in Pieces 3-5 and traces of red oxidized clay soil in Piece 6, along with a significant change in lithology between Units 8 and 9. | |
| 21R-2 to 22R-2 | 9 | Aphyric basalt | The base of Unit 9 is inferred to be at the top of Section 23R-2. |
| 22R-2 | Break in lava accumulation | There is a significant change in lithology between Cores 22R and 23R. | |
| 23R-1 to 25R-2 | 10 | Sparsely plagioclase-olivine-phyric to aphyric basalt | The base of Unit 10 is at Section 25R-2, 71 cm. |
| 25R-2 | 11a | Red-brown soil | Contact between Unit 11a and 11b is placed at the bottom of Section 25R-2 because the thin-bedded red-brown clay contains relict clasts that have groundmass texture similar to that of the underlying lava flow and are different from the unit above. |
| 26R-1 to 26R-3 | 11b | Aphyric basalt | The base of Unit 11b is at Section 26R-3, 79 cm. |
| 26R-3 | 12a | Red-brown soil | Red clay mixed with angular (broken by drilling) lava fragments represents soil produced by weathering of the underlying lava flow. The base is at Section 26R-3, 105 cm. |
| 26R-3 to 28R-1 | 12b | Aphyric basalt | Highly weathered basalt is present in Piece 17. The base of Unit 12b is at Section 28R-1, 3 cm. |
| 28R-1 | 13a | Red soil and weathered flow top | Piece 1B consists of dark reddish brown unconsolidated silty clay, and Piece 1C is glassy lava from the top of the underlying lava. The contact between Units 12a and 12b is placed at Section 28R-1, 10 cm. |
| 28R-1 to 28R-4 | 13b | Aphyric basalt | Pieces 7-10 in Section 28R-4 consist of lapilli-size glassy and hypocrystalline scoriaceous lava clasts, which is the basal rubble to Unit 13b. The base of Unit 13b is at Section 28R-4, 85 cm. |
| 28R-4 | 14a | Red soil and weathered flow top | This horizon contains soil formed by penetrative weathering of the top of the underlying lava flow. The base is at Section 28R-4, 135 cm. |
| 28R-4 to 29R-3 | 14b | Sparsely to moderately plagioclase-olivine-phyric basalt | The base of Unit 14b is at Section 29R-3, 3 cm. |
| 29R-4 | 15a | Red-brown soil | Piece 1 in Section 29R-4 consists of red-brown unconsolidated clay soil. The base is at Section 29R-4, 25 cm. |
| 29R-3 to 30R-1 | 15b | Sparsely to moderately plagioclase-olivine-phyric basalt | Basal flow rubble is present in Piece 19. The base of Unit 15b is at Section 30R-1, 97 cm. |
| 30R-1 | Weathered flow top | Piece 20 in Section 30R-1 is a weathered pahoehoe flow top of Unit 16. | |
| 30R-1 to 32R-3 | 16 | Sparsely to moderately plagioclase-olivine-phyric basalt | The upper boundary is a weathered flow top in Section 30R-1. Unit 16 has a smooth glassy pahoehoe base at Section 32R-3, 46 cm. |
| 32R-3 | Weathered flow top | Weathered flow top of Unit 17. Penetrative weathering of the flow top has formed a brown clay. Pieces of unaltered lava are present as 2- to 50-mm-sized fragments. | |
| 32R-3 to 33R-4 | 17 | Sparsely to moderately plagioclase-olivine-phyric basalt | Unit 17 is a weathered flow top (Pieces 3-7). The top is at Section 32R-3, 46 cm, and the base at Section 33R-4, 25 cm. |
| 33R-4 | 18a | Red soil and weathered flow top | Weathered flow top of Unit 18. Penetrative weathering of the flow top has formed a red-brown clay. Vesicular basalt lava at the top of Piece 7 in Section 33R-4 is similar to the basalt of Unit 17 and contains altered glassy lobe margins in contact with soil. 1- to 2-cm-sized fragments of highly altered aphanitic basalt (similar to those of Unit 18b) are present in the clay. |
| 33R-4 to 35R-1 | 18b | Aphyric to moderately olivine-phyric basalt | The base of Unit 18b is at Section 35R-1, 55 cm. |
| 35R-1 | 19a | Weathered flow top | Weathered flow top of Unit 19. Penetrative weathering of the flow top has formed a brown clay. Subrounded to angular domains of olivine phyric basalt are present as 2- to 40-mm-sized fragments. |
| 35R-1 to 35R-4 | 19b | Moderately to highly olivine-phyric basalt | The base of Unit 19b is at Section 35R-4, 131 cm. |
| 35R-5 to 36R-1 | 19c | Olivine basalt breccia | The base of Unit 19c is at Section 36R-1, 20 cm. |
| 36R-1 | Weathered flow top | Weathered flow top of Unit 20. Penetrative weathering of the flow top is situated below the flow base rubble of Unit 19. | |
| 36R-1 to 37R-2 | 20 | Sparsely to moderately olivine-phyric basalt | The base of Unit 20 is at Section 37R-2, 20 cm. |
| 37R-2 | Weathered flow top | Weathered flow top of Unit 20. Penetrative weathering of the flow top has formed a brown clay. Subrounded to angular centimeter-sized fragments of the underlying lava are present in the clay. | |
| 37R-2 to 38R-1 | 21 | Moderately to highly plagioclase-olivine-phyric basalt | The base of Unit 21 is inferred to be at the top of Section 38R-1. |
| 38R-1 | Break in lava accumulation | There is a significant change in lithology between Cores 37R and 38R-40R. | |
| 38R-1 to 40R-2 | 22 | Moderately olivine-plagioclase-phyric basalt | The base of Unit 22 is at Section 40R-2, 83 cm. |
| 40R-2 | 23 | Red-brown soil | This horizon is red-brown soil. The base is at Section 40R-2, 109 cm. |
| 40R-2 to 41R-3 | 24a | Aphyric basalt | The base of Subunit 24a is at Section 41R-3, 73 cm. |
| 41R-3 | 24b | Aphyric basalt breccia | The base of Subunit 24b is at Section 41R-3, 115 cm. |
| 41R-3 | 25 | Red brown soil | This horizon is a red-brown soil. The base is at Section 43R-3, 123 cm. |
| 41R-3 to 41R-5 | 26a | Aphyric to sparsely plagioclase-phyric basalt | The base of Unit 26a is at Section 41R-5, 115 cm. |
| 42R-1 | 26b | Aphyric basalt breccia | The base of Unit 26b is at Section 42R-1, 31 cm. |
| 42R-2 | Red soil and weathered flow top | There is 3-4 cm of red-brown soil on top of an eroded flow surface and deeply weathered flow top. | |
| 42R-1 to 43R-4 | 27 | Aphyric to moderately plagioclase-phyric basalt | The top of Unit 27 is defined by a weathered flow top capped by 2-3 cm of soil. The base of Unit 27 is at Section 43R-4, 78 cm. |
| 43R-4 | Weathered flow top | Weathered flow top of Unit 28. Penetrative weathering of the flow top has formed a brown clay. 5- to 30-mm-sized fragments of less-altered olivine-phyric basalt are present. | |
| 43R-4 to 44R-2 | 28a | Moderately olivine-plagioclase-phyric basalt | The top of Unit 28 is defined by a deeply weathered flow top. The base of Unit 28 is at Section 44R-2, 66 cm. |
| 44R-2 | 28b | Olivine-plagioclase basalt-breccia | Basal breccia to Unit 28a. There is 1 cm of soil attached to Piece 3. The base of Unit 28b is at Section 44R-2, 74 cm. |
| 44R-2 | Brown soil? | Soil is present on the edges of Pieces 2 and 3. Unit 28b breccia is cemented by zeolites, whereas interclast voids in Unit 29a breccia are partly filled by laminated detrital silt and clay. | |
| 44R-2 | 29a | Olivine basalt breccia | Flow-top breccia to Unit 29b. There is soil (2 cm) attached to top of Piece 4, and breccia is infiltrated by detrital silty clay. The base of Unit 29a is at Section 44R-2, 84 cm. |
| 44R-2 | 29b | Moderately olivine-phyric basalt | The base of Unit 29b is at Section 44R-2, 134 cm. |
| 44R-2 | 29c | Olivine basalt breccia | Basal breccia to Unit 29b. The base of Unit 29c is at Section 44R-2, 84 cm. |
| 44R-2 | Break in lava accumulation | Unit 29c breccia is cemented by zeolites, whereas the voids in the Unit 30a breccia are partly filled by laminated detrital silt and clay. | |
| 44R-2 | 30a | Olivine-plagioclase basalt breccia | Flow-top breccia to Unit 30b. The base of Unit 30a is taken to be at the top of Section 44R-3. |
| 44R-2 to 45R2 | 30b | Aphyric to moderately olivine-plagioclase-phyric basalt | The base of Unit 30b is taken to be at the bottom of Section 45R-2. |