Figure 2. Bathymetric map of the Middle America Trench and lower continental slope region off the Nicoya peninsula, Costa Rica. Dotted lines show the locations of 2D seismic Line CR-20, on which Sites 1039, 1040, and 1043 are positioned, and 3D lines and cross lines locating Sites 1041 and 1042. Bathymetry is from Hydrosweep data, shown with permission of R. von Huene and GEOMAR. Contour interval is 20 m.
Figure 3. 2D seismic reflection Profile CR-20, showing the locations of Sites 1039, 1043, 1040, and 1041 (geometrically projected). Note the high-amplitude reflection at the base of the sedimentary apron beneath Site 1041 (geometrically projected). Vertical scale is in two-way traveltime.
Figure 4. Depth migrated seismic Line CR-20, located in Fig. 2. Positions of Sites 1039, 1043, and 1040 are shown.
Figure 5. 3D seismic reflection Line CR3D-48, which crosses Site 1042. Profile is taken from depth-migrated 3D grid and is located near the southeast corner of the grid. Small escarpments on the seafloor are interpreted as the outcrop of normal faults that effect the uppermost ~100 m. At greater depth, the prism appears to be cut by thrust faults.
Figure 6. Graphical representation and summary plots of shipboard core and downhole measurements. LWD = logging while drilling, MST = multisensor track, SGR = spectral gamma ray (total counts), and CGR = computed gamma ray (total counts minus contribution of uranium). Gabbro contact was located ~40 m deeper in Hole C than in Hole B; it remains uncertain whether this is caused by a depth datum problem or by a local geological feature (fault; discontinuous gabbro layer). Difference of gabbro depth between Holes B and D (~15 m) can be attributed to measured deviation of Hole D from vertical.
Figure 7. Graphical representation and summary plots of shipboard core and downhole measurements. LWD = logging while drilling and SGR = spectral gamma ray (total counts).
Figure 8. Graphical representation and summary plots of shipboard core and downhole measurements.
Figure 9. Graphical representation and summary plots of shipboard core and downhole measurements. LWD = logging while drilling, SGR = spectral gamma ray (total counts), and CGR = computed gamma ray (total counts minus contribution of uranium).
Figure 10. Graphical representation and summary plots of shipboard core and downhole measurements. LWD = logging while drilling, SGR = spectral gamma ray (total counts), and CGR = computed gamma ray (total counts minus contribution of uranium).