Two different cruises provided the seismic reflection data for Detroit Seamount: Ocean Drilling Program (ODP) Leg 197 (JOIDES Resolution) and the USGS GLORIA Mapping Program cruise F-2-87-AA (Farnella) (USGS, 1987) (Fig. F2). Leg 197 data were collected in two separate surveys, referred to as Survey 1203 (around ODP Site 1203) and Survey 1204 (around ODP Sites 883/1204). Lines 1203-1, 1203-3, and 1203-6 intersect at Site 1203; Lines 1204-1 and 1204-3 intersect at Site 883, ~500 m northwest of Site 1204. The two F-2-87-AA lines (Lines F41 and F43) are subparallel, separated by ~25 km. Line F41 intersects Lines 1204-1 and 1204-3, and Line F43 passes within 1 km of Lines 1203-3 and 1203-4, allowing limited correlation with these data sets (Fig. F2).
To assist detailed analysis of Detroit's stratigraphic record and effectively correlate sediment horizons from one data set to another, we attempted to process both the Leg 197 and the F-2-87-AA data sets equivalently. The different source signatures of the Leg 197 and F-2-87-AA data sets (nonminimum phase water gun vs. minimum phase air gun, respectively) and different frequency contents (Leg 197 peaks between 40 and 45 Hz and F-2-87-AA data peaks at 22 and 44 Hz with a 30-Hz notch) limited the degree to which the processing results could be matched. We attempted a source-signature deconvolution during both Leg 197 surveys (in order to convert the data to minimum phase) prior to predictive deconvolution. The lack of a true far-field source-signature recording of the water gun source and a significant loss of signal-to-noise ratio due to source-signature deconvolution artifacts rendered source-signature deconvolution impractical for Survey 1204 data. A persistent receiver ghost, prominent just below the seafloor in the Survey 1203 data, required a signature deconvolution for which we simulated the far-field source-receiver signature using the water-bottom reflection by stacking 40 traces from a thick (~ 800 ms two-way traveltime [TWT]) part of the sediment cap.
Further discussion of the seismic data from Detroit Seamount is reported and discussed in Kerr et al. (2005). Seismic sections from Lines 1203-1, 1204-1, F41, and F43 are shown in Figures F5, F6, F7, and F8, respectively. Acquisition parameters and data processing flows for Surveys 1203, 1204, and F-2-87-AA are listed in Table T1. See Table T2 for drill site locations and line crossing information from these seismic surveys.
Tarduno, Duncan, Scholl, et al. (2002) report that two different types of acoustic basement are present in the vicinity of Site 1205 that produce distinctly different seismic signatures (Fig. F9). The first type appears as laterally coherent, low-frequency, west-dipping reflections near Site 1205. These reflections coincide with a sequence of dominantly alkalic basalt lava flow units interbedded with soil layers (Fig. F9). Locally, this section continues nearly to the bottom of Hole 1205A. The second type appears more massive, lacks laterally coherent internal reflections, and gently slopes upward to the southeast. The strongly reflective sequence of lava flows and interbedded soils thins to the southeast. Below 203 mbsf, which roughly corresponds to 1.88 s TWT, laterally coherent reflections cease to occur at Site 1205. Acquisition parameters and the data processing flow for Survey 1205 are listed in Table T1. See Table T2 for drill site and line crossing locations from Survey 1205.
Figure F10 shows the most prominent feature on Koko Seamount: a 200-m-thick sediment drift (assuming a sediment velocity of 1700 m/s). On the southeastern flank, a series of wavy reflections is present in the upper part of the sediment cap. The right side of Figure F10 also shows sediment horizons onlapping onto basement in a westerly direction. Kerr et al. (2005) discuss the possible origin of these features. Acquisition parameters and the data processing flow for Survey 1206 are listed in Table T1. See Table T2 for drill site and line crossing locations from the Survey 1206.