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Table T5. Key parameters for Hole 1256D and preliminary subdivisions of the upper oceanic crust at Site 1256 adopted for Expedition 335.

Location: 6°44.163’N, 91°56.061’W
Water depth (m): 3634.7; 3645.4 mbrf
Sediment thickness (m): 250
Interval in Hole 1256C drilled during Leg 206: 338.5 mbsf, 88.5 msb
Casing in Hole 1256D:
Height of reentry cone: 2.4 m
Internal diameter of reentry cone: 3.5 m (11 ft, 5 inches)
20 inch casing string (m): 95.12
16 inch casing string (m) 269
Interval in Hole 1256D drilled during
Leg 206: 752 mbsf, 502 msb; basement advance (m): 502
Expedition 309: 1255.1 mbsf, 1005.1 msb; basement advance (m): 503
Expedition 312: 1507.1 mbsf, 1257.1 msb; basement advance (m): 252
Expedition 335: 1521.6 mbsf, 1271.6 msb; basement advance (m): 14.5
lithologic zone
Sublithology Top of lithology Top igneous unit Depth
Lavas Lava pond 206-1256D-2R-1, 0 cm 1256D-1 (1256C-1 through 1256C-18) ~250 Massive ponded lava including overlying sheet flows.
Inflated flows 206-1256D-13R-1, 0 cm 1256D-2 350.3 Massive, sheet, and pillowed flows with rare inflation features.
Sheet and massive flows 206-1256D-43R-1, 0 cm 1256D-16 533.9 Sheet flows with subordinate massive flows.
Transition zone   309-1256D-117R-1, 85 cm 1256D-40 1004.2 Sheet flows with breccia, rare dikes, and alteration at (sub)greenschist facies conditions.
Sheeted dike complex Upper dikes 309-1256D-129R-1, 0 cm 1256D-44A 1060.9 Massive basalt, common subvertical intrusive contacts. Elevated P-wave velocity and thermal conductivity.
Granoblastic dikes 312-1256D-192R-1, 0 cm 1256D-78 1348.3 Granoblastic texture; equant grains; secondary clinopyroxene, orthopyroxene, plagioclase, hornblende, magnetite, and ilmenite.
Plutonic section Gabbro 1 312-1256D-213R-1, 52 cm (Piece 13) 1256D-81 1406.62 Medium-grained, generally orthopyroxene-bearing gabbroic rocks intrude overlying dikes: olivine gabbro, gabbro, and (disseminated) oxide gabbro, intruded by oxide gabbro to oxide quartz diorite.
Dike Screen 1 312-1256D-225R-1, 0 cm (Piece 1) 1256D-90 1458.9 Fine-grained to cryptocrystalline basalt dikes. Highly altered; granoblastic texture; secondary clinopyroxene, orthopyroxene, plagioclase, magnetite, ilmenite, and hornblende.
Gabbro 2 312-1256D-230R-1, 15 cm (Piece 5) 1256D-91 1483.1 Plutonic rock intrudes dike screen; medium-grained disseminated oxide gabbronorite with subordinate oxide gabbro, intruded by oxide gabbro, (oxide) diorite, and oxide quartz diorite veins; all highly altered; stoped basalt.
Dike Screen 2 312-1256D-232R-2, 98 cm (Piece 9) 1256D-94 1494.9 Fine-grained granoblastic basalt (Unit 1256D-94) may have igneous or metamorphic origin. Unrecrystallized greenschist-facies late dike (Unit 1256D-95) at 1502.6 mbsf. Strongly to completely recrystallized granoblastic basalts containing minor oxide diorite patches; subordinate quartz diorite and tonalite (Unit 1256D-96). Also includes granoblastic basalts intruded by oxide gabbro to tonalite patches, veins, and dikelets and with minor (<3%) gabbroic rocks, from the “junkyards” at ~1500–1521.6 mbsf.

This table is available in ASCII and in Microsoft Excel format (see 101_T05.XLS in CHAPTER_101 in TABLES in “Supplementary material”).

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