Table T2. Summary of observed lithofacies, Site U1421.
| Main facies | Subfacies | Facies | Description | Marine microfossils | Lithostratigraphic unit | Tentative depositional environment/diagenesis |
|---|---|---|---|---|---|---|
| Mud | Massive mud with lonestones | F1a | (Very) dark gray to (very) dark greenish gray; Facies thickness from 1.49 to 9.92 m; With dispersed to abundant clasts; Occasionally diatom/biosiliceous-rich/bearing, some shell fragments; Bioturbation mostly absent but occasionally heavy (typically in intervals with high amounts of diatoms); Angular to rounded lonestones include siltstone, sandstone, argillite, mudstone breccia, metasandstone, gneiss, quartzite, basalt, rhyolite, mica schist, and slate; Occasional occurrence of pods of silt, sand, and granules; Trace amounts of volcanic ash in Core 341-U1421A-41X; Occasional occurrence of mud laminae (Section 1H-5); Mud with abundant clasts can be strongly consolidated (e.g., Cores 7H and 8H); May show signs of intense soft-sediment deformation (e.g., Core 61X); Interbedded with Facies F1c, F4f, F5a, F5b, and F5c | Diatoms, sponge spicules | I, II | Suspension fall-out, ice rafting, or sediment gravity flows |
| Massive mud without lonestones | F1b | Dark greenish gray to dark gray; Facies thickness from 5 cm to 5.95 m; Often diatom bearing; Occasional shell fragments, foraminifers, and black mottles; Bioturbation mostly absent but occasionally slight; May contain lamination (e.g., Core 341-U1421A-56X); Interbedded with Facies F1a, F4f, F5a, F5b, and F7 | Diatoms and rare foraminifers | I, II | Suspension fall-out or sediment gravity flows | |
| Diamict | Interbedded mud and diamict | F4d | Dark gray; Facies thickness from 24 cm to 1.31 m; Sandy clast-poor diamict interbedded with up to 4 cm thick mud beds and laminae; Diamict contains granules and pebbles of siltstone, granitoids, greenstone, and sandstone; Often irregular transitions between diamict and mud intervals; Bioturbation is absent, and shell fragments are rare; Interbedded with Facies F4f and F5a | Not documented | II | Suspension settling and ice rafting (icebergs and/or sea ice) |
| Clast-poor diamict | F4e | Very dark gray; Facies thickness from 13 cm to 4.65 m; Mostly silty or muddy matrix, occasionally sandy matrix; Subrounded to subangular granule and pebble clasts, including sandstone, basalt, siltstone, argillite, metasandstone, schist, chert, granite, rhyolite, granitoid, vein quartz, gneiss, marble(?), and greywacke; Occasional occurrence of shell fragments; Bioturbation absent; Interbedded with Facies F4f and F5b | Not documented | II | Suspension setting and ice rafting (mainly by icebergs) | |
| Clast-rich diamict | F4f | (Very) dark gray; Facies thickness from 3 cm to 3.44 m; Mostly muddy and silty matrix, often with sand; Subrounded to subangular granule and pebble clasts, including siltstone, sandstone, basalt, rhyolite, vein quartz, metasiltstone, greenstone, granitoid, gneiss, metasandstone, argillite, mudstone, granite, diorite, conglomerate(?), metasedimentary breccia, metaigneous rock, and chert; Very rare shell fragments; Bioturbation absent; Very rare trace amounts of ash; Interbedded with Faces F1a, F1c, F4d, F4e, F5b, and F7 | Not documented | II | Suspension setting and ice rafting (mainly by icebergs) | |
| Diatom ooze | F5a | Dark greenish gray; Facies thickness and 12 cm to 1.42 m; Laminated (millimeter-scale) or thin bedded without bioturbation or massive with slight to heavy bioturbation; Absent lonestones; Occasional shell fragments; Interbedded with Facies F1a, F1c, and F4d | Diatoms | I, II | High-productivity environment and/or low terrigenous input and/or better preservation | |
| Biosiliceous ooze; biosiliceous-rich/bearing mud and/or sand; mud with diatoms/biosilica | F5b | Dark greenish gray to (very) dark gray; Facies thickness from 19 cm to 5.95 m; Mud without clasts and mud with dispersed to abundant clasts; Mostly diatom bearing; Occasionally parallel lamination (Cores 341-U1421A-1H and 56X); Occasional shell fragments; Occasional black mottles; Bioturbation mostly absent but rarely slight or heavy; Rarely with foraminifers; Rare traces of volcanic ash; Interbedded with Facies F1a, F1c, F4e, F4f, and F7 | Diatoms, sponge spicules | I, II | Temporarily increased productivity and/or reduced suspension settling and/or better preservation | |
| Calcareous/ carbonate-bearing/rich mud, silt, sand, diamict, and/or diatom ooze | F5c | Grayish green; Facies thickness from 15 to 18 cm; One interval of diatom-rich mud with foraminifers; Slight bioturbation; Black mottles present; Interbedded with Facies F1a | Foraminifers, bivalve, gastropod | I | Temporarily increased productivity and/or reduced suspension settling and/or better preservation | |
| Volcaniclastic mud, sand, diamict, and/or ooze | F7 | Dark greenish gray to dark gray; Facies thickness from 46–67 cm; In diatom-bearing mud and clast-rich diamict; Bioturbation either absent (diamict) or heavy (mud); Interbedded with Facies F1c, F4f, and F5b | Not documented | II | Volcanic detritus either bioturbated or reworked/redeposited by sediment gravity flows |
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