| Basement unit |
Unit type | Thickness (m) | Rock/flow type | Phenocryst/major minerals | Groundmass/minor minerals | Thin sections detailed in "Petrography and Primary Mineralogy" in "Igneous Petrology" | ||
|---|---|---|---|---|---|---|---|---|
| Total | Subunit | |||||||
| 1 | Plagioclase-phyric basalt | 6.1 | Massive | Plagioclase
(1%) Olivine (0%-8%) Clinopyroxene (<1%) |
Basaltic groundmass* | 25R-1,
105-106 cm 25R-3, 90-93 cm |
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| 2 | Aphyric basalt | 10.1 | A | 2.9 | Brecciated | Plagioclase
(20%-25%) Olivine (2%-5%) Clinopyroxene (2%-5%) |
Basaltic groundmass | 25R-4,
11-13 cm 25R-4, 33-35 cm 25R-4, 77-81 cm |
| B | 7.2 | Massive | Plagioclase
(<1%) Clinopyroxene (0%-1%) Olivine (0%-1%) |
Basaltic
groundmass Pentlandite (tr) |
25R-5,
113-115 cm 26R-1, 140-142 cm 26R-2, 7-8; 38-40 cm |
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| 3 | Plagioclase-phyric basalt | 16.6 | A | 9.6 | Vesicular | Plagioclase
(5%) Olivine (3%) |
Basaltic groundmass | 27R-2, 24-27 cm |
| B | 7 | Massive | Plagioclase
(1%) Clinopyroxene (0%-1%) Olivine (0%-0.5%) |
Basaltic groundmass | 27R-4,
66-68 cm 28R-4, 30-32 cm 29R-2; 35-38 cm |
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| 4 | Plagioclase-phyric basalt | 26.6 | Vesicular | Plagioclase
(11%-20%); Clinopyroxene (1.5%-5%); Olivine (0.5%-3%) |
Basaltic
groundmass Pentlandite (tr) |
29R-2,
71-74 cm 29R-4, 17-18 cm 31R-3, 3-5 cm 31R-4, 48-51 cm 32R-5, 73-75; 7, 48-50 cm |
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| 5 | Volcanic lithic sandstone | 4.4 | Medium Sandstone |
Lithic
fragments (75%) Feldspar (10%) Quartz (5%) |
Garnet
(1%) Brown hornblende (tr) |
33R-1,
121-124 cm 33R-3, 50-53 cm |
||
| 6 | Volcanic conglomerate | 31.0 | Clast | Trachyte | Sanidine
(20%) Plagioclase (4%)Clinopyroxene (2%) |
Feldspar Titanomagnetite Zircon |
33R-5, 10-12 cm | |
| Clast | Flow-banded rhyolite | Sanidine
(8%-15%) Plagioclase (1%-3%) |
Glass;
titanomagnetite Apatite; zircon; sulfide |
33R-5
19-25 cm 34R-2, 113-117 cm 34R-3, 119-122 cm |
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| Clast | Garnet-biotite gneiss | Feldspar
(55%); quartz (20%) Garnet (15%); biotite (10%) |
Zircon;
magnetite Amphibole |
35R-2, 46-47 cm | ||||
| Clast | Actinolite gneiss | Potassic
feldspar (70%) Quartz (22%) |
Microcline;
plagioclase Actinolite; magnetite Zircon |
34R-2, 100-103 cm | ||||
| Clast | Granite | Potassic
feldspar (50%) Plagioclase (40%) Quartz (12%) |
Titanomagnetite Zircon |
35R-2, 66-69 cm | ||||
| 7 | Plagioclase-phyric basalt | 13.0 | A | 5.8 | Brecciated | Plagioclase
(10%) Olivine (2%) |
Basaltic groundmass | 37R-5, 80-83 cm |
| B | 7.2 | Massive | Plagioclase
(5%-14%); Olivine (0.5%-2%); Clinopyroxene (<1%) |
Basaltic groundmass | 38R-3,
80-83 cm 39R-1, 112-115 cm 39R-2, 53-56 cm |
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| 8 | Plagioclase-phyric basalt | 10.6 | A | 3.4 | Vesicular | Plagioclase | Basaltic groundmass | |
| B | 7.6 | Massive | Plagioclase
(7%-9%) Olivine (3%-4%) |
Basaltic groundmass | 40R-2,
121-122 cm 41R-1 68-73 cm |
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| 9 | Crystal-vitric tuff | 14.9 | Tuff | Massive | Sanidine
(35%-40%) Plagioclase (2%-3%) Quartz (<2%) |
Oxidized
mafics (3-5%) Lithic clasts (<5%) Titanomagnetite (tr) Kaersutite (tr) Zircon (tr) |
41R-1,
127-128 cm 41R-2, 98-99; 3, 42-46 cm 43R-3, 42-44; 4, 57-60 cm 44R-4, 6-9; 44-46 cm |
|
| Clast | Garnet-biotite gneiss | Feldspar
(65%) Garnet (10%-15%) Biotite (5%-20%) |
Titanomagnetite Zircon, pyrite |
43R-4,
57-60 cm 44R-4, 44-46 cm |
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| 10 | Plagioclase-phyric basalt | 10.7 | A | 3.5 | Brecciated | Plagioclase
(10%-28%) Olivine (2%-5%) |
Basaltic groundmass | 44R-4,
71-72 cm 45R-1, 80-84 cm 45R-2, 7-10; 19-21; 77-80 cm |
| B | 7.2 | Massive | Plagioclase
(15%-25%) Clinopyroxene (1%-4%) Olivine (<1%) |
Basaltic
groundmass Pyrrhotite (tr) Chalcopyrite (tr) |
45R-4,
118-120 cm 46R-2, 95-96 cm |
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Note: * = plagioclase ± clinopyroxene ± titanomagnetite ± mesostasis (altered glass), tr = trace.