OCEAN DRILLING PROGRAM LEG 180 SCIENTIFIC PROSPECTUS WOODLARK BASIN Dr. Philippe Huchon Co-Chief Scientist, Leg 180 CNRS-Laboratoire de Geologie Ecole Normale Superieure 24 rue Lhomond 75231 Paris Cedex 05 France Dr. Brian Taylor Co-Chief Scientist, Leg 180 School of Ocean & Earth Science & Technology University of Hawaii 2525 Correa Road Honolulu, Hawaii 96822-2285 U.S.A. Dr. Adam Klaus Staff Scientist, Leg 180 Ocean Drilling Program Texas A&M University Research Park 1000 Discovery Drive College Station, Texas 77845-9547 U.S.A. ___________________ __________________ Jack Baldauf Adam Klaus Deputy Director Leg Project Manager of Science Operations Science Services ODP/TAMU ODP/TAMU February 1998 Material in this publication may be copied without restraint for library, abstract service, educational, or personal research purposes; however, republication of any portion requires the written consent of the Director, Ocean Drilling Program, Texas A&M University Research Park, 1000 Discovery Drive, College Station, Texas 77845-9547, U.S.A., as well as appropriate acknowledgment of this source. Scientific Prospectus No. 80 First Printing 1998 Distribution Electronic copies of this publication may be obtained from the ODP Publications Home Page on the World Wide Web at http://www-odp.tamu.edu/publications. D I S C L A I M E R This publication was prepared by the Ocean Drilling Program, Texas A&M University, as an account of work performed under the international Ocean Drilling Program, which is managed by Joint Oceanographic Institutions, Inc., under contract with the National Science Foundation. Funding for the program is provided by the following agencies: Australia/Canada/Chinese Taipei/Korea Consortium for Ocean Drilling Deutsche Forschungsgemeinschaft (Federal Republic of Germany) Institut Français de Recherche pour l¹Exploitation de la Mer (France) Ocean Research Institute of the University of Tokyo (Japan) National Science Foundation (United States) Natural Environment Research Council (United Kingdom) European Science Foundation Consortium for the Ocean Drilling Program (Belgium, Denmark, Finland, Iceland, Italy, The Netherlands, Norway, Portugal, Spain, Sweden, Switzerland, and Turkey) Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation, the participating agencies, Joint Oceanographic Institutions, Inc., Texas A&M University, or Texas A&M Research Foundation. This Scientific Prospectus is based on pre-cruise JOIDES panel discussions and scientific input from the designated Co-Chief Scientists on behalf of the drilling proponents. The operational plans within reflect JOIDES Planning Committee and thematic panel priorities. During the course of the cruise, actual site operations may indicate to the Co-Chief Scientists and the Operations Manager that it would be scientifically or operationally advantageous to amend the plan detailed in this prospectus. It should be understood that any proposed changes to the plan presented here are contingent upon approval of the Director of the Ocean Drilling Program in consultation with the Science and Operations Committees (successors to the Planning Committee) and the Pollution Prevention and Safety Panel. Technical Editor: Karen K. Graber ABSTRACT The lateral variation from active continental rifting to seafloor spreading within a small region makes the western Woodlark Basin an attractive area to investigate the mechanics of lithospheric extension. Earthquake source parameters and seismic reflection data indicate that low-angle (~25° to 30°) normal faulting is active in the region of incipient continental separation. A low-angle normal fault emerges along the northern flank of Moresby Seamount, a continental crustal block with greenschist metamorphic basement. Asymmetric basement fault blocks overlain by only minor ponded sediments characterize the margin to the south, whereas the margin to the north has a down flexed prerift sedimentary basin and basement sequence unconformably onlapped by synrift sediments. Leg 180 will drill a transect of three sites just ahead of the spreading tip: ACE-9a on the down flexed northern margin; ACE-8a through the rift basin sediments, the low-angle normal fault zone, and into the footwall; and ACE-3c near the crest of the footwall fault block (Moresby Seamount). The primary objectives at these sites are (1) to characterize the composition and in situ properties (stress, permeability, temperature, pressure, physical properties, and fluid pressure) of an active low-angle normal fault zone to understand how such faults slip, and (2) to determine the vertical motion history of both the downflexed hanging wall and the unloaded footwall as local groundtruth for input into regional models to determine the timing and amount of extension prior to spreading initiation. INTRODUCTION The processes by which continental lithosphere accommodates strain during rifting and the initiation of seafloor spreading are presently known primarily from the study of either (1) passive margins bordering rifted continents, where extensional tectonics have long ceased and evidence for active tectonic processes must be reconstructed from a record that is deeply buried in postrift sediments and thermally equilibrated; or (2) regions of intracontinental extension, such as the U.S. Basin and Range and the Aegean, where extension has occurred recently by comparison to most passive margin examples but has not proceeded to the point of continental breakup. One particularly controversial conjecture from these studies is that aerially large normal detachment faults dip at low angles and accommodate very large amounts of strain through simple shear of the entire lithosphere. The role of low-angle normal detachment faults has been contested strongly, both on observational and theoretical grounds. It has been suggested that intracontinental detachments are misinterpreted and actually form by rollover of originally high-angle features, or that they occur at the brittle/ductile boundary in a pure shear system. Theoretically, it has been shown that normal faulting on detachment surfaces would require that the fault be extremely weak‹almost frictionless‹to allow horizontal stresses to cause failure on low-angle planes. The growing evidence for a weak fault and strong crust associated with motion on the San Andreas Transform Fault supports the weak normal detachment fault model, and models abound in the literature in which low-angle detachment faulting is an essential mechanism of large-scale strain accommodation. Nevertheless, the mechanisms by which friction might be effectively reduced on low-angle normal fault surfaces are not understood. One possibility is that active shearing in the fault zone creates a strong permeability contrast with the surrounding crust (by opening cracks more quickly than precipitation can heal them), allowing pore pressures that are high and near to the fault-normal compressive stress within the fault zone, but that decrease with distance into the adjacent crust (Rice, 1992; Axen, 1992). Others have suggested that fluid-rock reactions form phyllosilicates in the fault zone that are particularly weak because of their well-developed fabrics (Wintsch et al., 1995). Alternatively, principal-stress orientations may be rotated into configurations consistent with low-angle faulting, although it has not been demonstrated that the magnitudes of reoriented stresses are sufficient to initiate and promote such slip (Wills and Buck, 1997). Testing for such fault-proximal high permeability and pore pressures, for the presence of weak phyllosilicates, and/or for local rotation of stress axes requires drilling into an active system. This would also allow determination of the properties of the fault rock at depth (do they exhibit reduced frictional strength at higher slip velocities, consistent with unstable sliding and observed earthquakes?) as well as studies of the mechanisms by which fluid-rock reactions affect deformation (constitutive response, frictional stability, long-term fault strength). See Hickman et al. (1993) and Barton et al. (1995) for extensive discussion of the mechanical involvement of fluids in faulting and Wernicke (1995) for a review of low-angle normal faulting. The continuum of active extensional processes, laterally varying from continental rifting to seafloor spreading in the western Woodlark Basin-Papuan Peninsula region of Papua New Guinea (Fig. 1) provides the opportunity to test these various models. Seafloor spreading magnetic anomalies indicate that during the last 6 m.y. the formerly contiguous, eastward extensions of the Papuan Peninsula (the Woodlark and Pocklington Rises) were separated as a westward propagating spreading center opened the Woodlark Basin about a pole close to Port Moresby (~9.5°S, 147°E). The current spreading tip is at 9.8°S and 151.7°E. Farther west, extension is accommodated by continental rifting, with associated full and half graben metamorphic core complexes and peralkaline rhyolitic volcanism. Earthquake source parameters and seismic reflection data indicate that low-angle normal faulting is active in the region of incipient continental separation (Figs. 2-5; Abers, 1991; Taylor et al., 1995, 1996; Mutter et al., 1996; Abers et al., 1997). Leg 180 will drill a transect of sites (just ahead of the spreading tip) above, below, and through a low-angle normal fault to determine the vertical motion and horizontal extension history prior to seafloor spreading and to characterize the composition and in situ physical properties of the active fault zone. BACKGROUND Recent Research Programs Several recent research programs have significantly improved our understanding of the regional geological and geophysical setting of rifting into the Papuan Peninsula (Figs. 1-3): 1.Sidescan and underway geophysical surveys have provided bathymetry, acoustic imagery, magnetization, and gravity maps that permit detailed reconstructions of the spreading history (Taylor et al., 1995, 1996; Goodliffe et al., 1997, and A. Goodliffe, unpubl. data). 2.Multichannel seismic reflection surveys reveal the upper crustal architecture of the rifting region, including the presence of low-angle normal faults (Figs. 3-5; Mutter et al., 1996; Taylor et al., 1996). 3.The PACLARK and SUPACLARK series of cruises in 1986-1991 (Binns et al., 1987, 1989, 1990; Lisitsin et al., 1991; Benes et al., 1994) included dredging, coring, camera and video observations, and seven Mir submersible dives. The bottom samples include normal mid-ocean ridge basalt (N-MORB) from the youngest spreading segments, as well as greenschist facies metamorphics from the lower north flank of Moresby Seamount. In contrast, a 1995 site survey dredged late Pliocene (synrift) sedimentary rocks from the upper south flank of Moresby Seamount‹apparently precluding a metamorphic core complex origin for this feature (Taylor et al., 1996). 4.Abers (1991) and Abers et al. (1997) determined source parameters and relocated earthquakes in the rifting region. The focal mechanisms are all extensional or strike-slip with northerly tension axes (T-axes; Fig. 2). Several are consistent with slip on shallow-dipping normal faults. 5.Studies of metamorphic core complexes on the Papuan Peninsula, D'Entrecasteaux, and Misima Islands (Fig. 2) show that (A) they are associated with Pliocene/Pleistocene granodiorite intrusions and amphibolite-facies ductile shear zones, (B) they have been rapidly exhumed from ~30 km depth (7-11 kilobar [kb]) in the last 4 m.y., (C) uplift continues (forming topography up to 2.5 km), and (D) they are very three dimensional and regionally discontinuous (or varying in grade) along strike (Davies and Warren, 1988, 1992; Hill, 1987, 1990, 1994, 1995; Hill et al., 1992, 1995; Hill and Baldwin, 1993; Baldwin et al., 1993; Lister and Baldwin, 1993; Baldwin and Ireland, 1995). 6.The Papuan Ultramafic Belt (PUB) is a late Paleocene to early Eocene supra-subduction zone ophiolite with gabbros and boninites 40Ar/39Ar dated at 59 Ma (R. Duncan, pers. comm., 1993; Walker and McDougall, 1982) and P4 (late Paleocene) foraminifer-bearing micrites overlying the basalts with tonalite-diorite-dacite intrusions K/Ar dated at 57-47 Ma (Rogerson et al., 1993). This revision to dating of the Papuan Peninsula basement allows a simplified geological evolution for the region, as outlined below. Papuan Crustal Evolution Paleogene Subduction and Collision Much of the Papuan Peninsula is 1-3 km above sea level and is underlain by crust 25-50 km thick (Finlayson et al., 1976). Major orogenic thickening of the crust occurred following the northeast subduction and partial accretion of a thick sequence of dominantly Cretaceous to Eocene strata beneath a late Paleocene-early Eocene island arc that includes the PUB, Milne Basic Complex, and Cape Vogel boninites (Davies and Jaques, 1984; Davies et al., 1984; Rogerson et al., 1987, 1993). Collision of the Australian (Papuan) continental margin plateau caused subduction to cease and uplifted the accretionary complex (Owen Stanley metamorphics) by the early Miocene (Rogerson et al., 1987). Metabasites in the Emo metamorphics and Suckling-Dayman massif (the latter with a cover of Maastrichtian micrites) have been exhumed from 7-12 kb (25-35 km) and may represent slivers of the subducted Cretaceous oceanic crust (Davies, 1980; Worthing, 1988). The preMiocene geology of the islands on the Pocklington and Woodlark Rises is similar to that of the Papuan Peninsula, with Owen Stanley metamorphics in the south (Misima, Tagula, and Rossel Islands) and Milne Basic Complex outcrops on Woodlark Island (Davies and Smith, 1971; Ashley and Flood, 1981). Likewise, late Paleocene volcanics occur at the base of the Nubiam 1 well (Stewart et al., 1986), west of the Trobriand Islands, and the metamorphic core complexes on the D'Entrecasteaux Islands have a core of Owen Stanley metamorphics and a cover of unmetamorphosed PUB ultramafics (Davies and Warren, 1988). Miocene-Quaternary Arc and Forearc Superimposed on this Paleogene basement is widespread middle Miocene to Holocene calc- alkaline and shoshonitic magmatism (Smith and Milsom, 1984) associated with southwest subduction of the Solomon Sea Basin at the Trobriand Trough. Active arc volcanism and a deforming accretionary prism are compatible with present-day slow subduction at the Trobriand Trough (Hamilton, 1979; Davies and Jaques, 1984; Lock et al., 1987), though this remains controversial given the small number of intermediate-depth earthquakes beneath the region (Abers and Roecker, 1991) and the lack of 10Be in the arc lavas (Gill et al., 1993). The geochemistry of the volcanics reveals melting and mixing of at least three magma sources: (1) subduction-modified mantle supplied the calc-alkaline arc volcanism; (2) this mantle, with the addition of partial melts from upwelling aesthenosphere, produced the comenditic (transitional basalt-peralkaline rhyolites) series around Dawson Strait; and (3) contamination by lower crust of Australian affinity formed minor high-K trachytes (see Smith, 1976; Hegner and Smith, 1992; Stolz et al., 1993; and references therein). The Cape Vogel (including Trobriand) Basin is a Neogene forearc basin, characterized by middle Miocene subsidence, volcanism, deep-marine sedimentation, late Miocene uplift and erosion (1-2 km) of the margins, and Pliocene coarse clastic (from uplift of the Papuan Peninsula and D'Entrecasteaux Islands to the south) and Quaternary carbonate, shallow-water sedimentation during broad subsidence (Tjhin, 1976; Stewart et al., 1986; Francis et al., 1987; Davies and Warren, 1988). The basin experienced late Miocene/Pliocene inversion in the northwest, but its center continues to subside in the southeast (Pinchin and Bembrick, 1985). The Lusancay- Trobriand-Woodlark Islands sit atop an outer forearc structural high with an associated 150-200 mgal free-air gravity anomaly. The Trobriand Trough, the outer forearc structural and gravity high, and the Cape Vogel forearc basin terminate near Woodlark Island. Farther east, the Woodlark and Pocklington Rises were not a Pliocene/Pleistocene arc-forearc system. Rather, the northern edge of the eastern Woodlark Rise was a transform margin, and seismicity and sidescan data indicate that it is still an active right- lateral fault. Thus, the Woodlark Basin did not originate as a backarc basin, in that the eastern Woodlark and Pocklington Rises were not active island arcs (Weissel et al., 1982). Nevertheless, the locus of present rifting (see below) bisects an inherited crustal asymmetry, with the Neogene forearc basin to the north and the Paleogene accretionary/collision complex and Neogene backarc to the south. Pliocene/Pleistocene Rifting Shallow seismicity, with extensional and strike-slip focal mechanisms having northerly T-axes, is concentrated east of the D'Entrecasteaux Islands and extends westward into the Papuan Peninsula at 9°-10°S to about 148°E (Fig. 2; Weissel et al., 1982; Abers, 1991; Abers et al., 1997). Pliocene/Pleistocene extension has produced three flooded grabens (Mullins Harbor, Milne Bay and Goodenough Bay) on the eastern extremity of the Papuan Peninsula with associated rift-flank subaerial uplift to over 500 m (Smith and Simpson, 1972). Metamorphic core complexes on the D'Entrecasteaux Islands and in the Suckling-Dayman massif on the Papuan Peninsula were also exhumed in the Pliocene/Pleistocene (Davies, 1980; Davies and Warren, 1988; Hill, 1990). The best structural studies, geothermometry, geobarometry, and age dating of these complexes have been done on Goodenough and Fergusson Islands (Davies and Warren, 1992; Hill et al., 1992, 1995; Hill and Baldwin, 1993; Baldwin et al., 1993; Lister and Baldwin, 1993; Hill, 1994; Baldwin and Ireland, 1995). There, normal movement along a 0.3- to 1.5-km-thick ductile mylonitic shear zone resulted in the uplift of deep metamorphic rocks and the juxtaposition of unmetamorphosed cover rocks. Granodioritic intrusion then focused uplift on several domes, offset by strike-slip faults. The ductile shear zones were brecciated and truncated by brittle faults late in their history. These domal structures are juxtaposed along strike with regions of significantly less unroofing, such as the low-grade (greenschist) eastern halves of both Normanby and Misima Islands. Woodlark Basin Evolution The oldest magnetic anomalies (An.3R), in the extreme east of the basin, indicate that seafloor spreading began by 6 Ma (Taylor, 1987; Taylor and Exon, 1987). Spreading has sequentially transgressed westward, stepping across Simbo Transform (156.5°E) about 4 Ma and Moresby Transform (154.2°E) about 1.9 Ma to reach its current tip at 151.7°E (Figs. 1, 2). Bruhnes Chron spreading rates decrease from 67 mm/yr at 156.2°E to 36 mm/yr at 152°E (Fig. 1). The 500-km- long spreading axis reoriented synchronously about 80-100 ka (Goodliffe et al., 1997, and unpubl. data). The sidescan and geophysical data show that the rifting-to-spreading transition involves both nucleation of discrete spreading cells and organized ridge propagation (Taylor et al., 1995). Two ridge propagation events into the margin at 153°E formed continental slivers surrounded by oceanic crust. Spreading is about to propagate into this margin again. Rifting of the conjugate margins continues for ~1 m.y. after spreading has separated them. Extension does not immediately localize to the ridge axis, as shown by the present overlap between spreading and seismogenic margin faulting, and by inwardly curved seafloor fabric and magnetic anomalies that require nonrigid margin reconstructions. The initial spreading system lacks transform faults and has both overlapping and orthogonally offset segments (Figs. 1, 2). The 50-km-offset Moresby Transform Fault formed by cutting through rifted crust to join overlapping spreading segments of initial oceanic crust. It is not contiguous with transfer faults in the rifted margins. The initial spreading system evolves by ridge propagation, transform development, and ridge jumping/rotation. Seismic reflection data indicate a very sharp (1 to 2 km wide at the surface) transition from rifted crust to oceanic crust. There are no dipping reflector sequences indicative of excessive lava production and high degrees of mantle partial melting, but there are small volcanoes a few kilometers in diameter that are often erupted along margin faults. Indeed, the initial seafloor spreading lavas indicate low degrees of partial melting: basalts from the youngest spreading segment, just east of Moresby Seamount, have Na8 = 3.1 (Binns and Whitford, 1987). Other young axial lavas include FeTi basalts and low- and high-Si andesites with evidence for both mantle heterogeneity and crustal contamination. Secondary convection in the mantle, induced by higher horizontal temperature gradients created during rifting of the thicker continental margins in the west, may explain the contrast in geophysical characteristics of the oceanic basins to either side of Moresby Tranform (Martinez et al., submitted 1998). With respect to the eastern basin, the western basin (1) is ~500 m shallower; (2) has Bouguer gravity anomalies that are >30 mgals lower; (3) has magnetic anomaly and modeled seafloor magnetization amplitudes that are respectively 100% and 50% higher; (4) has spreading centers with rifted axial highs as against axial valleys; (5) has smoother seafloor fabric; and (6) has exclusively nontransform spreading center offsets in contrast to transform faults and fracture zones that extend to the basin edges, all despite having lower spreading rates. Drilling Area The rifting region just ahead of the apex of spreading has been imaged by several seismic reflection surveys (Figs. 3-5; Mutter et al., 1993, 1996; Goodliffe et al., 1993; Taylor et al., 1996). North of Moresby Seamount, a low-angle (25°-30°) normal fault dips north beneath a down- flexed prerift sedimentary basin and basement sequence, unconformably onlapped by synrift sediments that are cut by higher angle normal faults with a zigzag pattern in plan view (Figs. 2-5). The seismic stratigraphy can be reasonably jump-correlated to that in the Trobriand Basin and is interpreted to be a Pliocene to Quaternary synrift sequence lying unconformably above a Miocene forearc basin sequence on Paleogene volcanic and metamorphic basement (Fig. 5). To the south of Moresby Seamount, high-relief rotated fault blocks are commonly overlain by only minor ponded sediments. Shallow (2-10 km) normal and strike-slip faults, with northerly T-axes, bound the north side of the rifting-spreading transition (Fig. 2; Abers, 1991; Taylor et al., 1995; Abers et al., 1997). All of the earthquake hypocenters occur within or north of the rift graben, and there are no major extensional structures north of the graben-bounding antithetic fault. Without local seismometers, the teleseismicity cannot be definitively associated with the low-angle reflector, but there is no more likely candidate structure. Furthermore, the seismic stratigraphy of the profiles in Figure 3 cannot be matched without recent faulting on the low-angle reflector. Two dredges of the northern flank of Moresby Seamount recovered metabasic greenschists, metagabbro, pelitic schist, and minor siliceous phyllite and microgranite that is material similar to the low-grade (greenschist) metamorphics on eastern Normanby and Misima Islands, not the core complex amphibolite metamorphics on Goodenough, Fergusson, and northwest Normanby (H. Craig, 1986, unpubl. SIO cruise report; Binns et al., 1987; J. Hill, pers. comm., 1996). In contrast, a dredge from 541 to 1211 m (~0.7-1.6 s two-way traveltime [TWT]) on the upper southern flank of the seamount recovered late Pliocene (N21 = 1.9-3.1 Ma) clastic sedimentary rocks of equivalent facies to the Awaitapu Formation of the Trobriand region in the Cape Vogel Basin (Francis et al., 1987). Benthic foraminifers indicate sediment deposition in water depths of 340- 800 m (J. Resig, pers. comm., 1995). These rocks are equivalent to those that we infer lie near the base of the synrift cover sequence in the rift basin and on the northern margin. A cross section consistent with the available seismic and dredge data is shown in Figure 5 (Taylor et al., 1996). At the end of the Miocene, the Paleogene basement and a forearc basin filled with Miocene sediment were being eroded at or near sea level. Pliocene rifting formed sediment-filled grabens in the southern orogenically thickened arc province, accompanied by gradual subsidence of the thinner, colder (and therefore stronger) forearc to the north (inferred Pliocene sediments are dotted in Fig. 5). Quaternary stretching localized on a low-angle normal fault (the antithetic hanging-wall fault accommodated little additional extension). The northern margin flexed down southward and was onlapped by sediments delivered via submarine channels incising northward. Recently, continued extension on the low-angle fault variably collapsed the hanging-wall graben, into which sediments are now prograding from the north. This interpretation predicts about 12 km of heave on the low-angle fault. This compares with at least 130 km of total extension in the 4 m.y. prior to spreading at this longitude, calculated from the pole of opening derived from seafloor spreading magnetic anomalies, and probably greater amounts back to the beginning of spreading at >6 Ma (Taylor et al., 1996). Given only minor extension of the northern, flexed margin, we infer that the locus of current extension must be the northernmost of a series of similar structures that extended weak crust to the south, forming the block-faulted Pocklington Rise. The regional estimates predict that this rugged province of mainly inactive faults accommodated >120 km of total strain as it collapsed from heights comparable to the 3-km-high Owen Stanley Ranges that form the backbone of the Papuan Peninsula. We do not know where to locate so much extension given a current total width of 200 km for this province. SCIENTIFIC OBJECTIVES The western Woodlark Basin is arguably the best characterized region of active continental breakup. The proximity of a seismogenic low-angle normal fault that has been imaged by seismic reflection data and zero-offset conjugate margins that are about to be penetrated by seafloor spreading is unique. There are two major objectives for drilling in this region. Both are within the broader context of understanding the physical processes and mechanics of lithospheric extension: 1.Characterize the composition and in situ properties (stress, temperature, physical properties, and fluid pressure) of an active low-angle normal-fault zone to understand how such faults slip. Questions to be answered include the following: What are the differences in properties of the active fault compared to the surrounding crust? How is friction effectively reduced? Is there a strong permeability and fluid pressure contrast between the fault zone and its surroundings? Do the fault zone materials exhibit reduced frictional strength at higher slip velocities, consistent with unstable sliding? How do fluid/rock reactions affect the deformation mechanisms and rock fabrics? 2.Determine the vertical motion history of both the down-flexed hanging wall and the unloaded footwall (by backstripping the biostratigraphy, regionalizing the well data using seismic stratigraphy, and by Pressure-Temperature-time [P-T-t] data and petrofabric studies of metamorphic basement), as local groundtruth for input into regional models to determine the timing and amount of extension prior to spreading initiation. Drilling a very deep hole (>2.5 km) through the low-angle normal fault in the seismogenic zone, where both the footwall and hanging wall are composed of basement, remains our long-term objective. However, as Leg 180 may penetrate only ~1200 m across the fault zone, this and further fault zone experiments and monitoring (e.g., CORK) will require a future leg. DRILLING STRATEGY Leg 180 will drill a transect of three sites across an asymmetric incipient conjugate margin pair (4- 5 km ahead of the spreading tip): Site ACE-9a on the down-flexed northern margin; Site ACE-8a through the rift basin sediments, the active low-angle normal fault zone, and into the footwall; and Site ACE-3c near the crest of the metamorphic footwall fault block (Moresby Seamount). Water depths at the drill sites range from 420 m to 3180 m. The sites are located within a grid of multichannel seismic (MCS) lines and multibeam bathymetry (Fig. 3). The northern site (ACE-9a) is designed to penetrate the Pliocene-Quaternary hemipelagic cover sequence into the prerift section of Miocene forearc clastics. Penetration into greenschist facies metamorphic basement beneath the 300-m-thick Pliocene-Quaternary section at Site ACE- 3c is planned to be 100+ m or until bit destruction. Site ACE-8a includes a triple-casing reentry hole (Fig. 6) that will also sample basement. The plan is to start with a jet-in test at Site 8a to determine how much initial casing can be washed in with the reentry cone at the Site 8a reentry hole. We will then core and log, to the maximum depth possible, at the Site ACE-8a pilot holes. This will be followed by coring and logging at Site ACE-9a before returning to Site ACE-8a for operations at the cased Site ACE-8a reentry hole. Site ACE-3c will be the final hole of the leg. Casing at the Site ACE-8a reentry hole is needed in anticipation of possibly unstable sediments (resulting from rapid deposition and faulting), an active fault zone (probably overpressured), and anisotropic basement (probably sheared and altered). We expect that this will be the most challenging drilling operation during Leg 180. Uncertainties regarding the degree of consolidation of the seafloor sediments may have considerable impact on our ability to install the reentry cone and attached conductor pipe (20-in. casing). The jet-in test at the begining of the leg will provide information to determine the appropriate type of seafloor structure and deployment technique. Our plan is to wash the reentry cone and casing into the seafloor. If the jet-in test indicates this is not possible, the installation process could become more complex and time consuming, potentially impacting other cruise activities. The vertical seismic profile (VSP) and packer experiments are dependent upon successfully cementing around the long casing strings. The cement characteristics are dependent on the local temperature gradient, which is unknown. Therefore, we plan to have specially blended cement and additives on board to allow shipboard adjustment of the cement characteristics. The deepest casing string was designed to use liner (10 3/4 in.) hanger technology instead of conventional casing hanger hardware. Installing a very long casing string through a potentially unstable detachment fault is problematic. Use of the liner hanger allows us to install the casing at the deepest possible point that the formation will allow without requiring that a predetermined length of hole remain open. Alternative Sites ACE-1c and ACE-7b exist to increase the stratigraphic resolution of the onlap sequences on the northern margin, if they are drilled. LOGGING PLAN All sites will be logged with the triple-combo geophysical and formation microscanner (FMS)/sonic (sonic digital tool [SDT]) combination tools to which the temperature tool (TLT) will be added. The triple-combo (DIT-HLDS-APS) will provide three independent porosity estimates by measuring the electronic density (hostile environment lithodensity sonde [HLDS]), the hydrogen density (accelator porosity sonde [APS]), and the electrical resistivity (phasor dual induction tool [DIT]). The dual laterolog (DLL) may be required to measure electrical resistivity in the basement if the basement turns out to be very resistive. The FMS will provide oriented images of drilling induced tensile fractures and natural fractures for stress analysis, for structural analysis, and core/log integration. The geological high-sensitivity magnetometer (GHMT), if on board, may be used at Site ACE-9a to aid core/log integration via magnetic susceptibility. The borehole televiewer (BHTV) will be run in the deeper section of Sites ACE-3c and 8a to ultrasonically image lithostratigraphy, fracture orientation, and the presence and extent of borehole breakouts. At Site ACE-8a, the Schlumberger five-element array seismic imager (ASI) will be used in the cased hole for a VSP to accurately tie the well to the MCS data. In addition, a drill-string straddle packer will be used to isolate two perforated intervals within the cemented casing and, perhaps, one interval within the open borehole below the casing. The three isolated intervals will be above, within, and below the fault zone. Once the packers are set, the isolated interval will be allowed to equilibrate to obtain the best possible estimate of formation pore pressures. Subsequently, pulse tests will be conducted to estimate formation permeabilities. If injected pulses decay very rapidly, indicating high formation permeability, constant-rate flow tests will be conducted. The longer duration tests allow for greater radius of influence and more reliable permeability estimates. Following the hydrogeologic tests in Site ACE-8a, the interval will be hydraulically fractured for the purpose of measuring the least principal stress magnitude (Shmin). These tests will consist of at least two cycles of fluid injection and shut-in, followed by bleeding off excess pressure. Details of the complete stress tensor will be inferred from hydraulic fracture experiment (Shmin), pore pressure estimates, and images (BHTV and FMS) of tensional (tensile cracking) and compressive (wellbore breakouts) failures. Repeated temperature profiles from logging may provide evidence for fluid flow associated with critically stressed fractures and faults. These temperature profiles will also help constrain the thermal perturbations, enabling the development of drilling-induced tensile cracking. Interactions between breakouts and fractures/faults may also be used to constrain the extent of stress perturbation associated with active faulting (Barton and Zoback, 1994). SAMPLING STRATEGY Sampling guidelines and policy are available at the following web site URL: http://www- odp.tamu.edu/curation/forms.htm. The Sample Allocation Committee (co-chiefs, staff scientist, and ODP curator onshore and curatorial representative on board ship) will work with the entire scientific party to formulate a formal leg-specific sampling plan for shipboard and postcruise sampling. Modification of the strategy during the leg must be approved by the co-chiefs, staff scientist, and curatorial representative on board ship. The minimum permanent archive will be the standard archive half of each core. All sample frequencies and sizes must be justified on a scientific basis and will be dependent on core recovery, the full spectrum of other requests, and the cruise objectives. Some redundancy of measurement is unavoidable, but minimizing the redundance of measurements among the shipboard party and identified shore-based collaborators will be a factor in evaluating sample requests. In some critical intervals (e.g., fault gouge, ash layers, basement, veins, etc.), there may be considerable demand for samples from a limited amount of core material. These intervals may require special handling, a higher sampling density, reduced sample size, or continuous core sampling by a single investigator. A coordinated sampling plan may be required before critical intervals are sampled. PROPOSED SITES Site ACE-3c This proposed site is situated on a small bench just north of the crest of Moresby Seamount near where the basement reflector is shallowest (Figs. 3-5). The site is positioned in 420 m of water to avoid the possible safety and logistical constraints of shallower water drilling. However, 12-kHz records indicate the presence of only 6 m of ponded sediments above the northeast-dipping sediments seen on seismic records. Approximately 300 m of lithified sediments and 100+ m of metamorphic basement may be drilled at this site. The primary objective at this site is to determine the internal structure and composition of Moresby Seamount, including the nature of the basement (rock type, P-T-t, structural fabric, and deformation history). By comparison with the stratigraphy and basement at the other sites, this will constrain the offset on the inferred low-angle normal fault. If Moresby Seamount is not a core complex, it should comprise sedimentary rocks above upper crustal rocks (presumably prerift metamorphic basement) without evidence of intense ductile deformation and rapid decompression. Site ACE-8a This proposed site is situated on the southern edge of the graben north of Moresby Seamount and will be drilled though the hanging wall, across the fault zone, and into the footwall of the inferred low-angle fault (Figs. 3-5). The expected section at Site ACE-8a includes up to 900 m of Quaternary hemipelagic sediments (only 0.7 s TWT, but are apparently fast-interval velocities averaging 2.6 km/s) overlying 250-300 m of fault zone and metamorphic basement rocks. The primary objectives at this site are to determine the (1) sedimentology, biostratigraphy, structural fabric, and vertical motion history in the graben; (2) in situ stress, temperature, physical properties, and fluid pressures in and around the fault zone; and (3) nature of the basement (rock type, P-T-t, structural fabric, deformation history) in and below the fault zone. Site ACE-9a Proposed Site ACE-9a is north of a major south-dipping normal-fault system that is antithetic to the low-angle fault dipping north from Moresby Seamount (Fig. 4). The site is positioned to cross two angular unconformities (Fig. 4). Beneath the lower angular unconformity, a stratified sequence, interpreted to be prerift forearc basin sediments, dips north. The expected sequence at Site ACE-9a includes 780 m of Holocene to Pliocene hemipelagic, synrift sediments unconformably overlying 220 m of consolidated Miocene forearc basin sediments. The primary objectives at this site are to determine the (1) sedimentology, biostratigraphy, and vertical motion history of the synrift sediments on the northern margin and (2) nature of the forearc basin sequence and, hence, the prerift history. Alternate Sites ACE-1c and ACE-7b These are alternate sites located on the northern margin (Figs. 3-5). The stratal geometry, including two angular unconformities, requires that at least two sites be drilled to best characterize this region. Site ACE-9a is a compromise site between these two. Proposed Site ACE-1c is just north of a major south-dipping normal-fault system that is antithetic to the low-angle fault dipping north from Moresby Seamount (Fig. 4). It is also located above north-dipping reflectors at the base of the interpreted prerift forearc basin sequence. The expected sequence at Site ACE-1c includes 950 m of Quaternary hemipelagic, synrift sediments unconformably overlying 50 m of Paleogene volcanic or metamorphic basement. Proposed Site ACE-7b is 15 km farther north on the margin and is positioned to cross two angular unconformities (Fig. 4). Beneath the lower angular unconformity, a stratified sequence dips north. The expected section at Site ACE-7b includes 640 m of Pliocene to Quaternary hemipelagic sediments unconformably overlying 110 m of consolidated Miocene forearc basin sediments. The primary objectives at these sites are to determine the (1) sedimentology, biostratigraphy, and vertical motion history of the northern margin; (2) nature of the forearc basin and basement sequence and, hence, the prerift history; and (3) in situ stress orientation, permeability, temperature, physical properties, and fluid composition in the basement for comparison with the same parameters in the active low-angle fault zone. REFERENCES Abers, G.A., 1991. Possible seismogenic shallow-dipping normal faults in the Woodlark- D'Entrecasteaux extensional province, Papua New Guinea. Geology, 19:1205-1208. 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Thermochronologic constraints on the tectonic evolution of active metamorphic core complexes, D'Entrecasteaux Islands, Papua New Guinea. Tectonics, 12:611-628. Barton, C.A., and Zoback, M.D., 1994. Stress perturbations associated with active faults penetrated by boreholes; possible evidence for near-complete stress drop and a new technique for stress magnitude measurement. J. Geophys. Res., 99:9373-9390. Barton, C.A., Zoback, M.D., and Moos, D., 1995. Fluid flow along potentially active faults in crystalline rock. Geology, 23:683-686. Benes, V., Scott, S.D., and Binns, R.A., 1994. Tectonics of rift propagation into a continental margin: western Woodlark Basin, Papua New Guinea. J. Geophys. Res., 99:4439-4455. Binns, R.A., Scott, S.D., Burne, R.V., Chase, R.L., Cousens, D.R., Denton, A.W., Edwards, R.J., Finlayson, E.J., Gorton, M.P., McConachy, T.F., Poole, A.W., Whitford, D.J., 1987. Western Woodlark Basin: Potential analogue setting for volcanogenic massive sulphide deposits. Proc. Pacific Rim Congr., 87:531-535. Binns, R.A., Scott, S.D., and PACLARK Participants, 1989. Propagation of sea-floor spreading into continental crust, western Woodlark Basin, Papua New Guinea, CCOP/SOPAC Misc. Rept. 79, 14-16. Binns, R.A., Scott, S.D., Wheller, G.E., and Benes, V., 1990. Report on the SUPACLARK cruise, Woodlark Basin, Papua New Guinea, April 8-28 1990, RV Akademik Mstislav Keldysh. CSIRO Rept. 176R. Binns, R.A., and Whitford, D.J., 1987. Volcanic rocks from the western Woodlark Basin, Papua New Guinea. Proc. Pacific Rim Congress, 87:525-534. Davies, H.L., 1980. Folded thrust and associated metamorphics in the Suckling-Dayman massif, Papua New Guinea. Am. J. Sci., 280:171-191. Davies, H.L., and Jaques, A.L., 1984. Emplacement of ophiolite in Papua New Guinea. Spec. Publ. Geol. Soc. Lond., 13:341-350. Davies, H.L., and Smith, I.E., 1971. Geology of eastern Papua. Geol. Soc. Am. Bull., 82:3299- 3312. Davies, H.L., Symonds, P.A., and Ripper, I.D., 1984. Structure and evolution of the southern Solomon Sea region. BMR J. Aust. Geol. Geophys., 9:49-68. Davies, H.L., and Warren, R.G., 1988. Origin of eclogite-bearing, domed, layered metamorphic complexes ("core complexes") in the D'Entrecasteaux Islands, Papua New Guinea. Tectonics, 7:1-21. Davies, H.L., and Warren, R.G., 1992. Eclogites of the D'Entrecasteaux Islands. Contrib. Mineral. Petrol., 112:463-474. Finlayson, D.M., Muirhead, K.J., Webb, J.B., Gibson, G., Furumoto, A.S., Cooke, R.J.S., and Russel, A.J., 1976. Seismic investigation of the Papuan Ultramafic Belt. Geophys. J. R. Astron. Soc., 29:245-253. Francis, G., Lock, J., and Okuda, Y., 1987. Seismic stratigraphy and structure of the area to the southeast of the Trobriand Platform. Geo-Marine Lett., 7:121-128. Gill, J.B., Morris, J.D., and Johnson, R.W., 1993. Time scale for producing the geochemical signature of island arc magmas: U-Th-Po and Be-B systematics in recent Papua New Guinea lavas. Geochim. Cosmochim. Acta, 57:4269-4283. Goodliffe, A., Taylor, B., Hey, R., and Martinez, F., 1993. Seismic images of continental breakup in the Woodlark Basin, PNG. Eos, Trans. AGU, 74:606. Goodliffe, A., Taylor, B., Martinez, F., Hey, R., Maeda, K., and Ohno, K., 1997. Synchronous reorientation of the Woodlark Basin spreading center. Earth Planet. Sci. Lett., 146:233-242. Hamilton, W., 1979. Tectonics of the Indonesian region, U.S. Geol. Surv. Prof. Paper, 1078. Hegner, E., and Smith, I.E.M., 1992. Isotopic compositions of late Cenozoic volcanics from southeast Papua New Guinea: evidence for multi-component sources in arc and rift environments. Chem. Geol., 97:233-249. Hickman, S., Sibson, R., and Bruhn, R. (Eds.), 1993. Proceedings of Workshop LXIII: The Mechanical Involvement of Fluids in Faulting. U.S. Geol. Surv. Open File Rpt., 94-228. Hill, E.J., 1987. Active extension in the D'Entrecasteaux Islands, Papua New Guinea. BMR Res. Symp., 87:51-57. Hill, E.J., 1990. The nature of shear zones formed during extension in eastern Papua New Guinea. Proc. Pacific Rim Congr., 90:537-548. Hill, E.J., 1994. Geometry and kinematics of shear zones formed during continental extension in eastern Papua New Guinea. J. Structural Geol., 16:1093-1105,. Hill, E.J., 1995. Extensional deformation of continental crust prior to break-up and sea-floor spreading: a study of Misima Island, Papua New Guinea. Geol Soc. Aust. Abstr. 9. Hill, E.J., and Baldwin, S.L, 1993. Exhumation of high-pressure metamorphic rocks during crustal extension in the D'Entrecasteaux region: Papua New Guinea. J. Metamorphic Geol., 11:261-277. Hill, E.J., Baldwin, S.L., and Lister, G.S., 1992. Unroofing of active metamorphic core complexes in the D'Entrecasteaux Islands, Papua New Guinea. Geology, 20:907-910. Hill, E.J., Baldwin, S.L., and Lister, G.S., 1995. Magmatism as an essential driving force for formation of active metamorphic core complexes in eastern Papua New Guinea. J. Geophys. Res., 100:10,441-10,451. Lisitsin, A.P., Binns, R.A., Bogdanov, Y.A., Scott, S., Zonenshayn, L.P., Gordeyev, V.V., Gurvich, Y.G., Murav-yev, K.G., Serova, V.V., 1991. Active hydrothermal activity at Franklin Seamount, western Woodlark Sea (Papua New Guinea). Internat. Geol. Rev., 33:914-929. Lister, G.S., and Baldwin, S.L., 1993. Plutonism and the origin of metamorphic core complexes. Geology, 21:607-610. Lock, J., Davies, H.L., Tiffin, D.L., Murakami, F., and Kisomoto, K., 1987. The Trobriand Subduction system in the Western Solomon Sea. Geomarine Lett., 7:129-134. Martinez, F., Taylor, B., and Goodliffe, A., 1998. Evidence for active rift-induced mantle convection in a young ocean basin: the Woodlark Basin, Papua New Guinea. J. Geophys. Res., submitted. Mutter, J.C., Mutter, C.Z., Abers, G., and Fang, J., 1993. Seismic images of low-angle normal faults in the western Woodlark Basin where continental extension yields to seafloor spreading. Eos, Trans. AGU, 74:412. Mutter, J.C., Mutter, C.Z., and Fang, J., 1996. Analogies to oceanic behaviour in the continental breakup of the western Woodlark Basin. Nature, 380:333-336. Pinchin, J., and Bembrick, C., 1985. Cape Vogel Basin, PNG - tectonics and petroleum potential. In 14th BMR Symposium Extended Abstracts: Petroleum Geology of South Pacific Island Countries. Bur. Min. Resour. Aust. Rec., 32:31-37. Rice, J.R., 1992. Fault stress states, pore pressure distributions, and the weakness of the San Andreas fault. In Evans, B., and Wong, T.-F. (Eds.), Fault Mechanics and Transport Properties of Rock (Int. Geophys. Ser. 51): San Diego, Academic Press, 475-503. Rogerson, R., Hilyard, D., Francis, G., and Finlayson, E., 1987. The foreland thrust belt of Papua New Guinea. Proc. Pacific Rim Congress, 87:579-583. Rogerson, R., Queen, L., and Francis, G., 1993. The Papuan Ultramafic Belt Arc Complex. In Wheller, G. E. (Ed.), Islands and Basins: Correlation and Comparison of Onshore and Offshore Geology. CCOP/SOPAC Misc. Rept. 159:28-29. Smith, I.E., and Simpson, C.J., 1972. Late Cenozoic uplift in the Milne Bay area, eastern Papua New Guinea. Bur. Min. Resour. Aust. Bull., 125:29-35. Smith, I.E.M., 1976. Peralkaline rhyolites from the D'Entrecasteaux Islands, Papua New Guinea, In Johnson, R.W. (Ed.), Volcanism in Australasia: Amsterdam (Elsevier), 275-285. Smith, I.E.M., and Milsom, J.S., 1984. Late Cenozoic volcanism and extension in eastern Papua. In Kokelaar, B.P., and Howells, M.F. (Eds.), Marginal Basin Geology, Geol. Soc. Spec. Publ., 16:163-171. Stewart, W.P., Francis, G., and Deibert, D.H., 1986. Hydrocarbon potential of the Cape Vogel Basin, Papua New Guinea. Geol. Surv. Papua New Guinea Rept. No. 86/10. Stolz, A.J., Davies, G.R., Crawford, A.J., and Smith, I.E.M., 1993. Sr, Nd and Pb isotopic compositions of Calc-alkaline and peralkaline silicic volcanics from the D'Entrecasteaux Islands, Papua New Guinea, and their tectonic significance. Mineral. and Petrol, 47:103- 126. Taylor, B., 1987. A geophysical survey of the Woodlark-Solomons region. In Taylor, B. and Exon, N.F., (Eds.), Marine Geology, Geophysics and Geochemistry of the Woodlark Basin - Solomon Islands, Earth Science Series, 7: Houston, (Circum-Pacific Council for Energy and Mineral Resources), 25-48. Taylor, B., and Exon, N.F., 1987. An investigation of ridge subduction in the Woodlark- Solomons region: Introduction and overview. In Taylor, B. and Exon, N.F. (Eds.), Marine Geology, Geophysics and Geochemistry of the Woodlark Basin - Solomon Islands, Earth Science Series, 7: Houston, (Circum-Pacific Council for Energy and Mineral Resources), 1- 24. Taylor, B., Goodliffe, A., Martinez, F., and Hey, R., 1995. A new view of continental rifting and initial seafloor spreading. Nature, 374:534-537. Taylor, B., Mutter, C., Goodliffe, A., and Fang, J., 1996. Active continental extension: the Woodlark Basin, JOI/USSAC Newsletter, 9:1-4. Tjhin, K.T., 1976. Trobriand Basin Exploration, Papua New Guinea. The APEA J., 81-90. Walker, D.A., and McDougall, I., 1982. 40Ar/39Ar and K-Ar dating of altered glassy volcanic rocks: the Dabi Volcanics, P.N.G. Geochim. Cosmochim. Acta, 46:2181-2190. Weissel, J.K., Taylor, B., and Karner, G.D., 1982. The opening of the Woodlark Basin, subduction of the Woodlark spreading system and the evolution of northern Melanesia since mid-Pliocene time. Tectonophysics, 87:253-277. Wernicke, B., 1995. Low-angle normal faults and seismicity: a review. J. Geophys. Res., 100:20159-20174. Wills, S., and Buck, W.R., 1997. Stress-field rotation and rooted detachment faults: a Coulomb failure analysis. J. Geophys. Res., 102, 20503-20514. Wintsch, R.P., Christoffersen, R., and Kronenberg, A.K., 1995. Fluid-rock reaction weakening of fault zones. J. Geophys. Res., 100:13021-13032. Worthing, M.A., 1988. Petrology and tectonic setting of blueschist facies metabasites from the Emo Metamorphics of Papua New Guinea. Aust. J. Earth Sci., 35:159-168. FIGURE CAPTIONS Figure 1. Major physiographic features and active plate boundaries of the Woodlark Basin region. The stippled area encloses oceanic crust formed during the Brunhes Chron at spreading rates labeled in mm/yr. MT and ST = Moresby and Simbo Transform Faults, respectively; DE = D'Entrecasteaux Islands. Top inset: geographical location of the Woodlark Basin. Bottom inset: depth profile along the axis of the spreading center with the five spreading segments numbered. Figure 2. HAWAII MR1 bathymetric texture and acoustic imagery. Relocated epicenters (black circles) and earthquake focal mechanisms are from Abers et al. (1997). PP = Papuan Peninsula, G = Goodenough Island, F = Fergusson Island, N = Normanby Island, R = Rossel Island, T = Tagula Island, MS = Moresby Seamount, MT = Moresby Transform Fault, M = Misima Island, W = Woodlark Island. The solid line is the landward boundary of oceanic crust, and the dashed line marks the boundary of crust formed during the Brunhes Chron. Figure 3. Location of the proposed drill sites (Sites ACE-1c, 3c, 7b, 8a, and 9a) and multichannel seismic track data plotted on a base map with 100-m bathymetric contours (thicker contours labeled every km). Relocated earthquake epicenters (open black circles) together with the focal mechanisms (beach balls) are from Abers et al. (1997). The western limit of the Woodlark spreading system is marked by the closed black line, the major rift-bounding normal faults by the ticked lines. Figure 4. Migrated seismic profiles showing the location of the proposed drill sites, Sites ACE- 1c, 3c, 7b, 8a, and 9a. Figure 5. Nested meridional sections showing the regional and local structures across the incipient conjugate margins. The proposed drill sites are Sites ACE-3c, 8a, and 9a, with alternate Sites ACE-1c and 7b. VE = vertical exaggeration. Figure 6. Planned reentry cone and casing installation at Site ACE-8a. SITE SUMMARIES Site: ACE-1c Priority: 2 Position: 9°35.117'S, 151°34.424'E Water Depth: 2307 m Sediment Thickness: 950 m Approved Maximum Penetration: 1030 mbsf Seismic Coverage: EW9510-1366 (WW01 CMP 4547) and 1381 (WW13 CMP 1681) Objectives: The objectives of Site ACE-1c are to determine the: 1. sedimentology, biostratigraphy, and vertical motion history of the northern margin; 2. nature of basement and the pre-rift history; and 3.basement stress orientation, permeability, temperature, physical properties, and fluid composition. Drilling Program: APC, XCB, RCB. Logging and Downhole Operations: Triple-combo Geophysics, FMS-sonic, GHMT (if on board), BHTV in basement, temperature (Adara, DVTP/WSTP). Nature of Rock Anticipated: Quaternary hemipelagic sediments, Paleogene volcanics and volcaniclastics. Site: ACE-3c Priority: 1 Position: 9°47.61'S, 151°34.50'E Water Depth: 420 m Sediment Thickness: 300 m Approved Maximum Penetration: 1000 mbsf Seismic Coverage: EW9510-1366 (WW01 CMP 6390) Objective: The objective of Site ACE-3c is to determine the internal structure and composition of Moresby Seamount including the nature of basement (rock type, P-T-t, structural fabric, and deformation history). Drilling Program: RCB. Logging and Downhole Operations: Triple-combo Geophysics, FMS-sonic, BHTV in basement. Nature of Rock Anticipated: 6 m Holocene carbonate sand; Quaternary sandstone, siltstone and mudstone; Paleogene greenschist facies metamorphics. Site: ACE-7b Priority: 2 Position: 9°27.327'S, 151°34.396'E Water Depth: 2115 m Sediment Thickness: 750 m Approved Maximum Penetration: 750 mbsf Seismic Coverage: EW9510-1366 (WW01 CMP 3399) and 1369a (WW4a CMP 1208) Objectives: The objectives of Site ACE-7b are to determine: 1.sedimentology, biostratigraphy, and vertical motion history of the northern margin, and 2. nature of the forearc basin sequence and the pre-rift history. Drilling Program: APC, XCB, RCB. Logging and Downhole Operations: Triple-combo Geophysics, FMS-sonic, GHMT (if on board), temperature (Adara, DVTP/WSTP). Nature of Rock Anticipated: 640 m Pliocene-Quaternary hemipelagic sediments above 110 m Miocene forearc basin sediments (sandstone, siltstone, and mudstone). Site: ACE-8a Priority: 1 Position: 9°44.71'S, 151°37.52'E Water Depth: 3175 m Sediment Thickness: 900 m Approved Maximum Penetration: 1500 mbsf Seismic Coverage: EW9510-1374 (WW08 CMP 1500) Objectives: The objectives of Site ACE-8a are to determine the: 1.sedimentology, biostratigraphy, structural fabric, and vertical motion history in the rift graben, 2.nature of basement (P-T-t, structural fabric, deformation history) in and below fault zone, and 3.in situ stress, temperature, physical properties, fluid pressure, and composition. Drilling Program: ACE-8a Pilot hole: APC, XCB, RCB, logging. ACE-8a Reentry hole: Reentry cone and triple casing, basement coring and logging, basement logging, casing perforation, packer hydrologic testing. Logging and Downhole Operations: Triple-combo Geophysics, FMS-sonic, BHTV, vertical seismic profile (ASI-VSP), packer experiments, temperature (Adara, DVTP/WSTP). Nature of Rock Anticipated: Quaternary hemipelagic sediments, sheared fault zone rocks, metamorphics. Site: ACE-9a Priority: 1 Position: 9°30.387'S, 151°34.393'E Water Depth: 2211 m Sediment Thickness: 1000 m Approved Maximum Penetration: 1000 mbsf Seismic Coverage: EW9510-1366 (WW01 CMP 3850) and 1379 (WW11 CMP 1624) Objectives: The objectives of Site ACE-9a are to determine: 1.sedimentology, biostratigraphy, and vertical motion history of the northern margin, and 2.nature of the forearc basin sequence and the pre-rift history. Drilling Program: APC, XCB, RCB. Logging and Downhole Operations: Triple-combo Geophysics, FMS-sonic, GHMT (if on board), temperature (Adara, DVTP/WSTP). Nature of Rock Anticipated: 780 m Pliocene-Quaternary hemipelagic sediments above 220 m Miocene forearc basin sediments (sandstone, siltstone, and mudstone). SCIENTIFIC PARTICIPANTS* Co-Chief Philippe Huchon CNRS, Laboratoire de Geologie École Normale Supérieure 24 rue Lhomond Paris Cedex 05 75231 France Internet: huchon@ens.fr Work: (33) 1-44-32-22-54 Fax: (33) 1-44-32-20-00 Co-Chief Brian Taylor School of Ocean & Earth Science & Technology University of Hawaii at Manoa 2525 Correa Road Honolulu, HI 96822-2285 U.S.A. Internet: taylor@soest.hawaii.edu Work: (808) 956-6649 Fax: (808) 956-5154 Staff Scientist Adam Klaus Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet : adam_klaus@odp.tamu.edu Work: (409) 845-3055 Fax: (409) 845-0876 Inorganic Geochemist Eric H. De Carlo Department of Oceanography/SOEST University of Hawaii at Manoa 1000 Pope Road Honolulu, HI 96822 U.S.A. Internet: edecarlo@soest.hawaii.edu Work: (808) 956-6473 Fax: (808) 956-7112 Organic Geochemist Ian D. Mather Department of Geology University of Bristol Wills Memorial Building Queens Road Bristol BS8 1RJ United Kingdom Internet: i.d.mather@bris.ac.uk Work: (44) 117-928-8930 Fax: (44) 117-925-3385 Geophysicist Andrew M. Goodliffe Department of Geology and Geophysics/SOEST University of Hawaii at Manoa 2525 Correa Road Honolulu, HI 96822 U.S.A. Internet: andrew@soest.hawaii.edu Work: (808) 956-5238 Fax: (808) 956-2538 JOIDES Logging Scientist Elizabeth J. Screaton Department of Geology University of Florida P.O. Box 117340 Gainesville, FL 32611 U.S.A. Internet: screaton@geology.ufl.edu Work: (352) 392-4612 Fax: (352) 392-9294 Paleomagnetist Gina M. Frost Hawaii Institute of Geophysics and Planetology University of Hawaii at Manoa 2525 Correa Road Honolulu, HI 96822 U.S.A. Internet: gfrost@soest.hawaii.edu Work: (808) 956-6192 Fax: Paleomagnetist Naoto Ishikawa School of Earth Sciences Kyoto University Sakyo-ku Kyoto 606-01 Japan Internet: ishikawa@gaia.h.kyoto-u.ac.jp Work: (81) 75-753-6871 Fax: (81) 75-753-6872 Paleontologist (Foraminifer), Russell C.B. Perembo Science Observer Department of Geology University of Papua New Guinea Box 414 University P.O. Papua New Guinea Work: (675) 267-395 Fax: (675) 260-369 Paleontologist (Foraminifer) Johanna M. Resig Department of Geology and Geophysics/SOEST University of Hawaii at Manoa 2525 Correa Road Honolulu, HI 96822 U.S.A. Internet: jresig@soest.hawaii.edu Work: (808) 956-7757 Fax: (808) 956-2538 Paleontologist (Nannofossil) William G. Siesser Department of Geology Vanderbilt University Box 46 Station B Nashville, TN 37235 U.S.A. Internet: siesser@ctrvax.vanderbilt.edu Work: (615) 322-2984 Fax: (615) 322-2138 Paleontologist (Nannofossil) Kyoma Takahashi Graduate School of Science Hokkaido University N10 W8 Sapporo, Hokkaido 060 Japan Internet: kyoma@epms.hokudai.ac.jp Work: (81) 11-716-2111, ext 3519 Fax: (81) 11-746-0394 Petrologist Suzanne L. Baldwin Department of Geosciences University of Arizona Bldg. #77 Tucson, AZ 85721 U.S.A. Internet: baldwin@geo.arizona.edu Work: (520) 621-9688 Fax: (520) 621-2672 Igneous Petrologist Charles K. Brooks Dansk Lithosfærecenter Øster Voldgade 10 København K 1350 Denmark Internet: kentb@geo.geol.ku.dk Work: (45) 35-32-24-17 Fax: (45) 33-11-08-78 Metamorphic Petrologist, Véronique Gardien Structural Geologist Laboratoire de Pétrologie et Tectonique Université Claude Bernard Lyon I 43 Bl du 11 Nov. 1918 Villeurbanne, Cedex 69622 France Internet: vgardien@univ-lyon1.fr Work: (33) 4-72-44-62-38 Fax: (33) 4-72-44-85-93 Physical Properties Specialist Garry D. Karner Lamont-Doherty Earth Observatory Columbia University Palisades, NY 10964 U.S.A. Internet: garry@ldeo.columbia.edu Work: (914) 365-8355 Fax: (914) 365-8156 Physical Properties Specialist Achim Kopf GEOMAR Christian-Albrechts-Universität zu Kiel Wischhofstr. 1-3 Kiel 24148 Federal Republic of Germany Internet: akopf@geomar.de Work: (49) 431-600-2333 Fax: (49) 431-600-2922 Sedimentologist Stefania Gerbaudo Dipartmento di Scienze della Terra Università degli Studi di Genova Corso Europa, 26 Genova 16132 Italy Internet: andri@dister.unige.it Work: (39) 10-3538287 Fax: (39) 10-352169 Sedimentologist Klas S. Lackschewitz Geologisch-Paläontologisches Institut Christian-Albrechts-Universität zu Kiel Olshausenstraße 40 Kiel 24118 Federal Republic of Germany Internet: klackschewitz@gpi.uin-kiel.de Work: (49) 431-880-2818 Fax: (49) 431-880-4376 Sedimentologist Alastair H.F. Robertson Department of Geology and Geophysics University of Edinburgh West Mains Road Edinburgh EH9 3JW United Kingdom Internet: alastair.robertson@glg.ed.ac.uk Work: (44) 131-650-8546 Fax: (44) 131-668-3184 Sedimentologist Timothy R. Sharp Department of Applied Geology University of Technology, Sydney P.O. Box 123 Broadway, N.S.W. Sydney 2007 Australia Internet: tim.sharp@uts.edu.au Work: (61) 2-9514-1757 Fax: (61) 2-9514-1755 Microbiologist Peter Wellsbury Department of Earth Sciences University of Bristol Wills Memorial Building Queens Road Bristol BS8 1RJ UK Internet: peter.wellsbury@bris.ac.uk Work: (44) 117-928-8859 Fax: (44) 117-925-3385 LDEO Logging Scientist Bernard Célérier Laboratoire de Tectonique et Géochronologie Université Montpellier II Sciences et Techniques du Languedoc Place Eugène Bataillon Case 58 Montpellier Cedex 05 34095 France Work: (33) 4-67-14-39-06 Fax: (33) 4-67-54-73-62 LDEO Logging Trainee Jacqueline Floyd Lamont-Doherty Earth Observatory Columbia University Palisades, NY 10964 U.S.A. Internet: jsfloyd@ldeo.columbia.edu Work: Fax: Schlumberger Engineer Robert Laronga Schlumberger Offshore Services 369 Tristar Drive Webster, TX 77598 U.S.A. Work: (281) 480-2000 Fax: (281) 480-9550 Operations Manager Michael A. Storms Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: michael_storms@odp.tamu.edu Work: (409) 845-2101 Fax: (409) 845-2308 Development Engineer Derryl Schroeder Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: derryl_schroeder@odp.tamu.edu Work: (409) 845-8481 Fax: (409) 845-2308 Laboratory Officer Burney Hamlin Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: burney_hamlin@odp.tamu.edu Work: (409) 845-2496 Fax: (409) 845-0876 Marine Lab Specialist: Yeoperson Michiko Hitchcox Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: michiko_hitchcox@odp.tamu.edu Work: (409) 845-2483 Fax: (409) 845-0876 Marine Lab Specialist: Chemistry Dennis Graham Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: dennis_graham@odp.tamu.edu Work: (409) 845-8482 Fax: (409) 845-0876 Marine Lab Specialist: Chemistry Chieh Peng Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: chieh_peng@odp.tamu.edu Work: (409) 845-2480 Fax: (409) 845-0876 Marine Lab Specialist: Curator Lorraine Southey Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: lorraine_southey@odp.tamu.edu Work: (409) 845-8482 Fax: (409) 845-1303 Marine Lab Specialist: Downhole Tools, Gus Gustafson Marine Lab Specialist: Thin Sections Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: ted_gustafson@odp.tamu.edu Work: (409) 845-8482 Fax: (409) 845-0876 Marine Lab Specialist: Paleomagnetics Edwin Garrett Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: edwin_garrett@odp.tamu.edu Work: (409) 845-2480 Fax: (409) 845-0876 Marine Lab Specialist: Photographer Tim Fulton Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A Internet: tim_fulton@odp.tamu.edu Work: (409) 845-1183 Fax: (409) 845-4857 Marine Lab Specialist: Physical Properties Melissa McEwen Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: melissa_mcewen@odp.tamu.edu Work: Fax: (409) 845-0876 Marine Logistics Coordinator TBN Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: Work: (409) 862-8715 Fax: (409) 845-2380 Marine Lab Specialist: X-Ray Robert Olivas Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: bob_olivas@odp.tamu.edu Work: (409) 845-2481 Fax: (409) 845-0876 Marine Lab Specialist: X-Ray Don Sims Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: don_sims@odp.tamu.edu Work: (409) 845-2481 Fax: (409) 845-0876 Marine Computer Specialist John Eastlund Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845 U.S.A. Internet: john_eastlund@odp.tamu.edu Work: (409) 845-3044 Fax: (409) 845-4857 Marine Computer Specialist David Morley Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845 U.S.A. Internet: david_morley@odp.tamu.edu Work: (409) 862-4847 Fax: (409) 845-4857 Marine Electronics Specialist TBN Ocean Drilling Program Texas A&M University 1000 Discovery Drive College Station, TX 77845-9547 U.S.A. Internet: Work: (409) 845-2454 Fax: (409) 845-2308 Sedimentologist Sherif Abdel Moneim Awadallah Earth Sciences Department Memorial University of Newfoundland St. John's, Newfoundland A1B 3X5 Canada Internet: sherif@morgan.ucs.mun.ca Work: (709) 737-8142 Fax: (709) 737-2589 Structural Geologist Bernard Le Gall Laboratoire de GŽologie Structurale UniversitŽ de Bretagne Occidentale URA CNRS 1278 6 Avenue Le Gorgue - BP809 Brest Cedex 29285 France Internet: blegall@univ-brest.fr Work: (33) 2-98-01-61-82 Fax: (33) 2-98-01-66-20 Physical Properties Specialist, JOIDES Logging Scientist Shannon C. Stover Department of Geological Sciences University of Colorado at Boulder Campus Box 399 Boulder, CO 80309 U.S.A. Internet: shannon.stover@colorado.edu Work: (303) 735-5032 Fax: (303) 492-2606 *Participants are subject to change