Seismic Coverage: MCS with 480 channels, 10 air guns; refraction shooting 20 air guns recorded on ocean-bottom hydrophones; 3.5-kHz reflection, Hydrosweep multibeam bathymetry: all acquired on Ewing cruise EW9903 (March–April, 1999). Site GUATB-03C is at the crossing of EW9903 lines 22 and 27.

Objectives:
1. Provide a reference with in situ samples of most or all of the extrusive section and possibly the upper dike section in normal, intact oceanic crust formed at very fast spreading rate at 15 Ma to constrain models of formation and alteration of oceanic crust.
2. Provide a "legacy hole" available for future deepening, possibly reaching the dike–gabbro transition in a single-leg return.

Drilling Program:
Hole A: APC/XCB core to top of basement. Jet-in test.
Hole B: RCB drill ahead to near basement, core to ~120 m into basement, log with triple combo, FMS/sonic, and if hole conditions permit, the BGR borehole magnetometer and UBI.
Hole C: Set a reentry cone with 20-in casing to ~80 m, set 16-in casing 20–110 m into basement, depending on observations made in Hole B. RCB core as deep as possible. If conditions require, log, set 13³/₈-in casing at intermediate depth, and then continue RCB coring. Log with triple combo, FMS/sonic, BGR borehole magnetometer, UBI, and WST-3.

Logging and Downhole: Triple-combo, FMS/sonic, BGR borehole magnetometer for oriented magnetic field measurements, UBI for acoustic borehole image, and WST for normal-incidence vertical seismic profiling.

Nature of Rock Anticipated: Pelagic sediment overlying basalt, dikes, and gabbro.

The seismic data for this site can be seen on Figures F8 and F9.