The Oaxaca transect, located off southern Mexico and drilled during Leg 66, sampled a truncated margin and subduction complex. In contrast, the Guatemala transect was selected because accretion was thought to have continued in this area during most of the Tertiary. Site surveys conducted by the University of Texas Marine Science Institute provided multichannel seismic records, among which profile GUA-13 was chosen as the location for Leg 67 drill holes. Selection of this transect arises in part from the fact that it includes a portion of the San José Canyon, thus layers of hemipelagic drape may have been stripped away by erosion, allowing quicker access to deep horizons. By studying the continental margin off Guatemala it was hoped to strengthen the tie between offshore and onshore geology, to describe the stratigraphic sequence from the continental slope to the subducting oceanic plate beneath, to recover in ash layers a record of Central American volcanism.

From 1983 until 1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions. At the time it was the most extended data compilation on ferromanganese deposits world wide. Initially published in a proprietary format incompatible with present day standards it was jointly decided by AWI and NOAA to transcribe this legacy data into PANGAEA. This transfer is augmented by a careful checking of the original sources when available and the encoding of ancillary information (sample description, method of analysis...) not present in the NOAA-MMS database.