A synthetic view of FMS interpretation and core- and log-defined units for Hole 1109D is given in Figure F28. Hole 1109D was not cored above 355 mbsf, and therefore the upper lithologic and structural units are defined in Hole 1109C. Further details on shipboard units can be found in figures F1 (lithostratigraphy), F50 and F52 (structures), F88 (logging), and F92 (synthesis) of Shipboard Scientific Party (1999c).
An obstruction at 351 mbsf, due to clay swelling, required two FMS runs to log Hole 1109D: an upper run, covering 351-115 mbsf, and a lower run with the drill pipe lowered below the obstruction, covering 781-380 mbsf (see the "Operations" and "Downhole Measurements" sections in Shipboard Scientific Party, 1999c). The data from both runs are shown, together with the data gap in the 351- to 380-mbsf interval (Fig. F28).
The structural measurement orientation is shown on stereographic projection and on strike and dip histograms for bedding (Fig. F29), fracture (Fig. F30), and unknown structures (Fig. F31).
The 471 bedding measurements show that most dips are <10° (Fig. F29). This agrees with the 120 core measurements (figs. F51 and F53 in Shipboard Scientific Party, 1999c). The south-southwest dip direction (Fig. F29) confirms that obtained on fewer shipboard FMS measurements (fig. F103 in Shipboard Scientific Party, 1999c). The density of bedding measurement varies as a function of depth according to how clearly bedding is defined (Fig. F28). Six depth intervals where bedding deviates from subhorizontal were identified: 190-202, 218-223, 240-252, 255-266, 310-320, and 670-680 mbsf (Fig. F28, column 7). These intervals are further analyzed below. They are all located below structural domain II (26-83 mbsf; Hole 1109C), where soft sediment deformation was observed in core.
The 44 fractures seen on the FMS images are located within the bottom dolerite except for one located at 220 mbsf (Figs. F28, F30). Core observations did not find evidence of brittle deformation in Hole 1109C (i.e., above 370 mbsf) and located three fracture zones in Hole 1109D. The uppermost zone (domain IVb; 359-370 mbsf) is present within the FMS data gap, the middle one (domain Vb; 676-684 mbsf) where no fractures are detected on FMS images, and the lower one (domain VII; 766-802 mbsf) corresponds to the massive dolerite. The last two fracture zones are further discussed below.
The depth shown on the FMS images is consistent with that of the conventional logs (see "Appendix").
The FMS images show little structure and dull bedding boundaries (Fig. F32), and therefore only a few structural measurements are available in the 115- to 170-mbsf interval that corresponds to lithologic Unit II (83-170 mbsf). This interval corresponds to the upper part of logging Unit L1 (82-219 mbsf), where neutron and density porosity separation indicate a high clay content with a few sandy or carbonate cleaner beds.
Thicker resistive beds appear as lithologic Unit III (170-247 mbsf) is entered, but initially their boundary remains dull and the structural measurements sparse (Fig. F33). Below 190 mbsf, the thickness and occurrence rate of resistive beds increases and their boundary and resistivity contrast becomes sharper, yielding denser structural measurements. Log analysis described the 192- to 197- and 197- to 200-mbsf intervals as sands and sandy carbonates, respectively (fig. F94 in Shipboard Scientific Party, 1999c); the respective FMS images show numerous resistive beds in the first interval (Fig. F34) and a uniform facies in the second one (Fig. F35).
Dipping structures are identified in the 190- to 202-mbsf interval on the FMS images (Fig. F28), both in the sandy upper part of the interval (Fig. F34) and at the very bottom of the lower carbonate part (Fig. F35). The fact that these dipping surfaces are found between horizontal bedding and seem related to varying bedding thickness suggests depositional structures. Gravity flow and drilling-induced fracturing were observed in core from this low-recovery interval. The orientation plot is consistent with a cylindrical structure with a horizontal axis trending N60°E (Fig. F36) that may be related to the depositional slope.
This interval is the second most resistive interval of the borehole as seen on the static FMS image (Fig. F28). It corresponds to logging Unit L2 (219-234 mbsf), defined by a characteristic log signature: neutron and density porosity convergence and high density, resistivity, and seismic velocity, which suggests calcareous sands (see fig. F94 in Shipboard Scientific Party, 1999c). This formation, which was barely recovered and therefore defined on the basis of logs only, also corresponds the major seismic reflector, Light Green 1, that can be traced to the similar logging Unit L2 in Hole 1118A (Goodliffe et al., this volume). Very resistive layers at 219.5 (Fig. F37) and 233-234 (Fig. F38) mbsf correlate with PEFL peaks on the logs, which indicates increased carbonate content.
The dynamic image shows a massive 223- to 234-mbsf lower section with rare bedding (Fig. F38) and a facies similar to that of the carbonate at 197-200 mbsf (Fig. F35) but for higher overall resistivity.
On the contrary, dipping structures are identified within the 218- to 223-mbsf upper section (Fig. F37). The resistive layer at 219.5 mbsf is cut by a steeply dipping discontinuity that suggests the only fault identified in the sediments on the FMS image from this hole. The orientation plot shows bedding and unknown planes compatible with a cylindrical structure with a horizontal axis trending N8°E (Fig. F39).
This interval corresponds to logging Unit L3 (234-293 mbsf), where neutron and density porosity divergence indicates an increased clay content (Figs. F28, F38). Core recovery is nearly complete in this interval but is affected by drilling-induced fractures.
The conductivity increases progressively downward in the 234- to 247-mbsf interval (Fig. F3), which corresponds to the bottom of lithologic Unit III, is similar to the bottom of logging Unit L1 (Fig. F32), except for thinner resistive beds, and yields numerous bedding orientations.
The 247- to 293-mbsf interval, which corresponds to the upper part of lithologic Unit IV (247-362 mbsf), is characterized by a conductive static image (Fig. F3) and by a lower contrast of the dynamic image where the clear thin resistive beds observed above are replaced by thicker beds with dull boundaries (Fig. F40).
Two intervals with dipping structures are observed on the FMS images.
In the upper 240- to 252-mbsf interval, dip is <25° and the orientation plot suggests a weakly constrained cylindrical structure with a horizontal axis trending N152°E (Fig. F41).
The lower low bedding contrast 255- to 266-mbsf interval shows steeply dipping (up to 60°) structures (Fig. F40). Most of these structures define intervals of consistent orientation and are interpreted as bedding, whereas a few discordant boundaries are classified as unknown. Steeply dipping fractures were observed in cores from this interval (Cores 180-1109C-28X and 29X), but no clear criterion allows to relate them to either type of dipping structures on the FMS image. The orientation plot shows a main southwest dip direction but no simple organization (Fig. F42).
The static FMS images show higher resistivity (Fig. F28) in the 293- to 330-mbsf interval, which corresponds to logging Unit L4 (293-330 mbsf), where intervals of neutron and density porosity convergence indicate the presence of clean beds. This correlates with a better contrast in the dynamic image that better constrains structural measurements (Fig. F43).
Moderately dipping beds are found in the 310- to 320-mbsf interval. Again, the dipping beds seem to be present between flat-lying beds, as seen at ~311 mbsf (Fig. F43), suggesting depositional structures. The orientation plot shows a poorly constrained cylindrical structure with a horizontal axis striking N75°E (Fig. F44).
The static FMS image is relatively conductive within the 430- to 570-mbsf interval (Fig. F28), which corresponds to lithologic Unit VI (388-570 mbsf) and most of logging Unit L6 (390-599 mbsf). However, detailed dynamic images show highly contrasted decimetric resistive beds with sharp boundaries (Fig. F45). This is consistent with the observation of well layered sandstones in cores from Unit VI and with the frequent neutron density porosity convergence in Unit L6, which indicates clean intervals. The increasing photoelectric effect below 540 mbsf, indicative of an increasing carbonate content, is correlated with an increasing resistivity in the static FMS image (Fig. F28).
This interval corresponds to lithologic Unit VII (570-672 mbsf), mainly composed of sandstones and carbonates. However, contrary to the mixing or alternating beds seen in most other units, three thick units with distinct lithologies are distinguished on the basis of logs and can therefore be correlated with FMS facies.
In the lower part of logging Unit L6, neutron density porosity separation and high PEFL indicate high clay and carbonate content, with the intercalation of a radioactive sand marked by high gamma ray and lower PEFL in the 593- to 598-mbsf interval. The dynamic FMS reflects this transition: above 592 mbsf (Fig. F46) it is similar to that of the carbonates at 197-200 and 233-234 mbsf (Figs. F35, F38); below that depth, grainy, more conductive layers are intercalated in the previous facies.
Logging Unit L7 (599-643 mbsf) is marked by lower PEFL, neutron density porosity convergence, and high gamma ray, which indicates a massive sand that was poorly recovered in core. The static FMS image is slightly more conductive than in Unit L6 above (Fig. F28) and the dynamic image displays a distinct grainy facies with less distinct bedding below 599 mbsf (Fig. F46).
Logging Unit L8 (643-673 mbsf), with high PEFL, neutron density-porosity convergence, and low gamma ray, corresponds to a massive carbonate that was also poorly recovered in core. The FMS static image is very resistive (Fig. F28). The dynamic image at the transition from logging Unit L7 to L8 (Fig. F47) shows alternating sandy (644-648 mbsf) and carbonate (642-643 mbsf) facies. The latter becomes dominant below 648 mbsf, where bedding disappears completely.
Lithologic Unit VIII (672-705 mbsf) and logging Unit L9 (673-714 mbsf) correspond to a lagoonal alternating organic-rich claystone and siltstone deposit with abundant shell and wood fragments. On the FMS images, a facies change from the carbonates of Unit L8 is seen at 675 mbsf (Fig. F48). The static image becomes slightly more conductive, and the dynamic image shows thin (5 cm thick), dipping conductive layers in the 675- to 678-mbsf interval.
Despite good core recovery, the FMS and core observations remain difficult to match; the dipping beds seen on the FMS did not stand out in the core and the steeply dipping fractures observed in core, defining fracture zone 2 (domain Vb; 676-686 mbsf), are not seen on the FMS (Fig. F48). Even though the 25% borehole wall coverage by the FMS pads lowers the odds of detecting steep structures, the complete absence of discontinuity within the massive resistive facies of this interval suggests that the fractures observed in core do not generate a resistivity contrast and therefore are not open. The orientation plot of the structure within the 674- to 680-mbsf interval does not define a clear structure (Fig. F49).
Below 681 mbsf, the facies changes again to a generally more conductive formation with resistive pieces and many intervals are washed out. This could be correlated with the increased clay content observed in core below 685 mbsf. FMS images from non-washed out intervals show alternating conductive and resistive layers consistent with the alternating sandstone and claystone described in core (Figs. F50, F51). In most instances a weak layering can be inferred, but a few intervals with nonplanar contacts suggest either possible conglomerate clasts or complex depositional structures (689-691 mbsf) (Fig. F50).
This interval corresponds to the poorly recovered dolerite conglomerate of lithologic Units IX (705-737 mbsf) and X (737-773 mbsf) and logging Units L10 (714-762 mbsf) and L11 (762-781 mbsf). Hole conditions are degraded by washouts in the upper interbedded conglomerate but become good in the more massive lower conglomerate, where high-resistivity pebbles can be seen on the images (Fig. F52).
The massive dolerite of lithologic Unit XI (773-802 mbsf) and logging Unit L11 is sharply defined by the highest resistivity on the static image for this hole (Fig. F28). Only the upper 5 m of the 50 m of cored dolerite (Units L11 and XI) could be reached and logged with the FMS. It is densely fractured (Fig. F53). The static image allows definition of the relative aperture of the fractures. A few of the widest fractures can be unambiguously traced on all four pads and are labeled as fracture 1. The orientation plot for the fractures is that of Figure F30, except for the single fracture outside this interval (labeled #37). The dip direction is scattered, with a weak north-northeast trend that is compatible with the main Moresby fault trend. The 126 core measurements showed a complex dip distribution with three peaks: 0°-5°, 20°-30°, and 60° (fig. F58A in Shipboard Scientific Party, 1999c). The 43 FMS measurements are compatible with the first two peaks but underestimate those of the steeply dipping structures around 60° (Fig. F30). This can be due in part to small borehole wall coverage but also to the fact that the logged interval represents only the upper part and a tenth of the length of the recovered dolerite cores.