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Table T4. Key parameters for Hole 1256D and preliminary subdivisions of the upper oceanic crust at Site 1256 adopted for Expeditions 309 and 312.

Location: 6°44.163′N, 91°56.061′W
Water depth (m): 3634.7
Sediment thickness (m): 250
16 inch casing string (m): 269.5
Interval in Hole 1256D drilled during
   ODP Leg 206: 752 mbsf, 502 msb
   IODP Expedition 309: 1255.1 mbsf, 1005.1 msb
   IODP Expedition 312: 1507.1 mbsf, 1257.1 msb
Major lithologic zone Sublithology Top core, section, piece, interval (cm) Top igneous unit Depth (mbsf) Criteria
Lavas Lava pond 206-1256D-2R-1 (Piece 1, 0) 1256D-1(1256C-1 through 18) ~250 Massive ponded lava including overlying sheet flows.
Inflated flows 206-1256D-13R-1 (Piece 1, 0) 1256D-2 350.3 Massive sheet and pillowed flows with rare inflation features.
Sheet and massive flows 206-1256D-43R-1 (Piece 1, 0) 1256D-16 533.9 Sheet flows with subordinate massive flows.
Transition zone
309-1256D-117R-1 (Piece 6, 85) 1256D-40 1004.1 Sheet flows with breccias, rare dikes, and alteration at (sub-) greenschist facies conditions.
Sheeted dike complex Upper dikes 309-1256D-129R-1 (Piece 1, 0) 1256D-44a 1060.9 Massive basalts, common subvertical intrusive contacts. Elevated VP and TC.
Granoblastic dikes 312-1256D-192R-1 (Piece 1, 0) 1256D-78 1348.3 Granoblastic texture; equant grains; secondary clinopyroxene, orthopyroxene, plagioclase, hornblende, magnetite, and illite.
Plutonic section Gabbro 1 312-1256D-213R-1 (Piece 13, 52) 1256D-81 1406.6 Medium-grained gabbroic rocks intrude overlying dikes: gabbro, disseminated oxide gabbro, patchy gabbro, and quartz-rich oxide diorite.
Dike screen 312-1256D-225R-1 (Piece 1, 0) 1256D-90 1458.9 Fine-grained to cryptocrystalline basalt dike. Highly altered, granoblastic texture, secondary clinopyroxene, orthopyroxene, plagioclase, magnetite, ilmenite, and hornblende.
Gabbro 2 312-1256D-230R-1 (Piece 5, 15) 1256D-91 1483.1 Plutonic rock intrudes upper and lower dike screens; medium-grained gabbro, oxide-bearing quartz gabbro, oxide gabbro, orthopyroxene-bearing gabbro, trondjhemite; leucocratic-gabbro; all highly altered; stoped basalt.Gabbronorite of uncertain origin.Late dike Unit 1256D-95 at 1502.6 mbsf.

Note: TC = thermal conductivity.

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