The fractures determined from the Hole 1114A FMS images correspond to either conductive or resistive features, depending on their filling material or on the surrounding formation.
Three major fracture zones (FZs) have been determined from the FMS images analysis: FZ1 (105-140 mbsf), FZ2 (180-215 mbsf), and FZ3 (270-285 mbsf). These fracture zones are clearly expressed on the fractures density (number of fractures per meter) vs. depth plot (Fig. F14). The three fracture zones are composed of structures displaying a wide range of dips, from ~10° to 80°. The orientations shown on stereonets for each fracture zone (Figs. F15, F16, F17) show a wide range of dip directions of random strike. However, the dip direction vs. depth plot of Figure F14 shows a change at 200 mbsf that suggests subdivision of FZ2 into an upper (FZ2a; 180-200 mbsf) (Fig. F18) and lower (FZ2b; 200-215 mbsf) (Fig. F19) section. In the upper section (FZ2a), orientations are concentrated around a 55° dip toward north (Fig. F18).
Between FZ1 and FZ2, no fractures were observed; there are only regular westward to northwestward dipping beds (Figs. F7, AF1), as described below in "Bedding." Between FZ2 and FZ3, the two washout zones do not present reliable FMS data. Below the washout zones, no structures, neither bed nor fracture, are observed because of the presence of a massive sandstone (Fig. F9).
Generally, fracture offsets are not visible in Hole 1114A FMS images. However, in three cases small reverse offsets can be observed. The corresponding faults define the set frac 2. Their orientation is shown on the stereonets (Figs. F15, F16). These three reverse faults are located (tadpole plot of Fig. AF1) within FZ1 at 131.5 mbsf and FZ2 at 194.5 and 196.8 mbsf along steep (70° in FZ1 and 42° and 60° in FZ2) northerly dipping fault planes that postdate earlier fault structures. The reverse fault observed in FZ1 at 131.5 mbsf is conductive and crosscuts earlier resistive faults on three FMS pads with a reverse offset of a few millimeters (Fig. F20). At the same depth, an array of reverse microfaults was observed on the recovered sandstones with a similar offset. In FZ2, the observed reverse faults are located at 194.5 and 196.8 mbsf in the upper section FZ2a (180-200 mbsf), where almost all the fractures dip northward (Fig. F18). The reverse faults are conductive and crosscut and shift thicker resistive beds (10-25 cm thick) with an offset of ~20-40 cm (Fig. F21). These zones of reverse faults are locally highly fractured within ~1 m around each reverse fault. Most of the observed events cannot be fitted by sinusoids either because they are not planar or because they are not visible on at least three pads.
Between these two short intervals there is no evidence of offset beds or fractures. It seems that within FZ2a the observed reverse faults are located in short (~1 m long), highly fractured sections and that the intervals between them correspond to ~1.5-m-thick fault-bounded blocks with many fewer fractures. Between 198 and 199.5 mbsf, three northward dipping, very resistive thin beds seem to be also offset with a reverse offset of ~20 cm. However, no associated reverse fault is observed on the FMS images. This succession of short, highly fractured and less fractured intervals can also be observed on the fractures density plot (Fig. F14) with a varying number of fractures with depth within FZ2.
FZ3 corresponds to the zone just above the sediment/tectonic breccia contact and is described below.
In the analyzed FMS section, bedding dips between 7° and 65° (Fig. F11). There is no evidence for a general either dip or dip direction vs. depth gradient (Fig. F22). However, the bedding dip direction is mainly northwest over all the logged interval except within FZ2 and suggests the definition of four intervals (B1, B2, B3, and B4) (Fig. F22) to present bed orientation on stereonets (Figs. F23, F24, F25, F26).
In the upper interval (B1; 100-180 mbsf), the bedding dip direction is globally northwest with two principal modes: N285° and N325°, though a wide spectrum of direction is in the northwest quarter (Fig. F23). The dips also present two modes: 15° and 35°. The widest range of dips and dip directions in this zone is located from the top of the FMS record down to ~140 mbsf, which corresponds to the location of FZ1.
The next interval (B2; 180-200 mbsf) is shorter and corresponds exactly to FZ2a. The bed orientations are more concentrated than in the previous interval around a 25° dip toward the northwest at N325° (Fig. F24). Even if this interval is highly fractured, it is very well organized, with a general northward dip direction for the fractures and a general northwestward dip direction for the beds.
Below (B3; 200-225 mbsf), the predominant bedding dip direction changes toward the southwest in the majority, with some beds having a westward dip direction (Fig. F25). The change of dip direction between B2 and B3 at 200 mbsf is very clear and sharp (Fig. F22). The west and southwest dip directions are present throughout the B3 interval except for two very local sets of beds dipping northward at ~205 mbsf and northwestward at 210 mbsf.
The lowest interval (B4; 225-300 mbsf) has ~20 m of washouts with no FMS data (Fig. F22). The beds average dip (45°) is the highest of the four intervals (Fig. F26). The dip direction is northwest in the majority, but a few beds that are parallel to the sediment/basement contact below dip southwestward.
Generally in the depth interval with FMS data, beds are well organized. Their dip direction is mainly northwest, except between 200 and 225 mbsf, where beds mainly dip southwestward. The different bed orientations and their variations seem to be clearly linked to the presence of fracture zones. In FZ1, fractures have an apparent random distribution of dip directions and beds have a wide range of dip and dip directions. In FZ2a, the upper section of FZ2, fractures and beds have a constant orientation. This implies that if the sediments have been rotated or tilted in this zone, this displacement was global. At the bottom of this section (200 mbsf), beds show a sharp change of dip direction that may be due to a stronger tilt of a sedimentary interval linked to this highly fractured 180- to 200-mbsf zone. Below the washout zone, beds recover the general orientation observed above 200 mbsf, with dips increasing with depth.
The sediment/basement contact observed on the FMS images at 291 mbsf corresponds to the sediment/tectonic breccia contact which, in turn, corresponds to a south-southwest-dipping fault zone observed on seismic sections and antithetical to the major Moresby detachment. The contact is seen very clearly on the statically normalized FMS image, with a strong resistivity contrast (Fig. F4). Indeed, the recovered breccia consists of highly brecciated metadoleritic basement rocks that form a steeply dipping extensional fault zone. These rocks are much more resistive than the overlying sediment. The dynamically normalized image shows that the tectonic breccia seems to have a centimeter-scale texture similar to the overlying sandstone. The sediment/breccia contact is present within or at the bottom of a washout zone (287-291 mbsf). The orientation of the washout zone boundaries very likely reflects the contact dip direction. The sediment/breccia contact is present along a surface dipping at 60° to the southwest, antithetical to the Moresby detachment. A few planar events (23) have been selected in the tectonic breccia on the FMS images. They have a wide range of dip and dip directions, but the majority of structures dip southwestward, which is consistent with the sediment/breccia contact orientation. This confirms the south-southwest dip direction of the whole fault zone.
The brecciated fault zone thickness is between 5 and 16.5 m from the combination of core and FMS results. The uncertainty is due to the low core recovery and to the washout zones and nearness to the bottom of the record for FMS data. The top of the fault zone may be located between 286 and 294.1 mbsf from cores and between 287 and 291.5 mbsf from FMS data. The bottom may be located between 287.35 and 303.54 mbsf from cores and at least at 296.5 mbsf from FMS data (bottom of the record).