Figure F1. Bathymetric map of the North Atlantic Ocean showing locations of Site 1276 in the Newfoundland Basin and DSDP and ODP drill sites on the western and southern margins of Galicia Bank on the conjugate Iberia margin (Legs 47B, 103, 149, 173).

Figure F2. Summary diagram of rift events in the Newfoundland–Iberia rift. Leg 210 drilling was at the boundary between the central and northern rift segments (black triangle at top of the figure). The green intervals show principal periods of rifting, and the vertically hatched intervals indicate hiatuses, most of which probably developed because of tectonic uplift associated with rifting. "E" at the bottom indicates evaporites deposited in shallow rift basins during the Late Triassic to Early Jurassic. Minor magmatism in the rift is documented south of Tagus Abyssal Plain in Gorringe Bank (Schärer et al., 2000) and on Galicia Bank (Schärer et al., 1995; Beard et al., 2002). The Southeast Newfoundland Ridge at the southern margin of Newfoundland Basin was a major locus of volcanism in the Barremian–Aptian (Tucholke and Ludwig, 1982). Open arrows = earliest proposed seafloor spreading, solid arrows = estimates for latest initiation of spreading. (Southern segment earliest = 145–131 Ma [Anomaly M20–M11] [Srivastava et al., 2000; Mauffret et al., 1989]; central segment earliest = 140 Ma [M17] [Srivastava et al., 2000], latest = 127–125 Ma [M5–M3] [Whitmarsh and Miles, 1995; Russell and Whitmarsh, 2003]; northern segment = ~122 Ma [M0] [Srivastava et al. 2000; Boillot et al., 1987]). Other data are compiled from Enachescu (1987), Tankard and Welsink (1987), Wilson (1988), Balkwill and Legall (1989), Murillas et al. (1990), Driscoll et al., (1995), Rasmussen et al. (1998), and Wilson et al. (2001).

Figure F3. A. Reconstruction of the Newfoundland–Iberia rift to Anomaly M0 time (121 Ma), based on the reconstruction pole of Srivastava et al., 2000. Newfoundland plate is fixed in present geographic coordinates. Solid circles = locations of Sites 1276 and 1277 in the Newfoundland Basin plus DSDP and ODP drill sites on the conjugate Iberia margin. Tectonic and other data are compiled from numerous sources (structural data from the SCREECH survey [Fig. F5] are not included). Light red = evaporites in continental rift basins. Ocean crust (center, blue) is presumed to have formed beginning near Anomaly M3. A south–north zipperlike opening would account for the observed splayed tectonic trends between the two margins and the northward-narrowing zone of ocean crust. On the Newfoundland side, U extends throughout the Newfoundland Basin and pinches out seaward near Anomaly M3. B. M0 reconstruction as in A, with locations of reflection profiles. Solid lines show locations of profiles in Figure F4 and dotted lines show positions of other SCREECH transects not illustrated here (see Fig. F5). BMT. = basement, SMT(S) = seamount(s). NFLD. = Newfoundland, A.P. = abyssal plain, FL. = Flemish, N.B. = Newfoundland Basin. F.Z. = fracture zone, T.Z. = transition zone.

Figure F4. Conjugate seismic reflection sections from the Newfoundland and Iberia margins, juxtaposed at Anomaly ~M1. Profiles are displayed north to south (top to bottom), and locations are shown in Figure F3B . Vertical exaggeration = ~12.5. On the Newfoundland side, sediments are shaded brown above basement and/or the intersecting U reflection; on the Iberia side, sediments are similarly shaded above basement. Top left: Simplified interpretation of SCREECH line 2MCS with location of Site 1276. Top right: Composite seismic section (Sonne 16, JOIDES Resolution, Lusigal 12, OC 103) along the conjugate Iberia drilling transect, adapted from ODP Leg 173 Scientific Party (Shipboard Scientific Party, 1998). Drill sites are numbered and lithology at the bottom of holes is indicated. Center left: Conrad multichannel seismic (MCS) line NB1 about 150 km south of SCREECH Line 2MCS, showing another view of Newfoundland basement structure and the overlying U reflection. Center right: MCS line IAM9 about 50 km south of Lusigal 12 off Iberia. Bottom left: Conrad MCS line NB19 in southern Newfoundland Basin. Bottom right: Conjugate MCS profile Lusitanie 86 over Tagus Abyssal Plain. Note the marked asymmetries in basement depth and roughness between the Newfoundland and Iberia sides of the rift.

Figure F5. Track line map showing three transects of the SCREECH survey (Ewing cruise 00-07) across the Newfoundland continental margin. Leg 210 drilling was on transect 2 (see Fig. F6). Bathymetric contour interval = 200 m.

Figure F6. Track line map of the SCREECH survey (Ewing cruise 00-07) along transect 2, conjugate to the ODP Leg 149/173 drilling transect on the Iberia margin (see Fig. F3B). Locations of Leg 210 Sites 1276 and 1277 are indicated. The black section of track line locates the section of reflection profile 2MCS illustrated in Figure F8. Bathymetric contour interval = 200 m.

Figure F7. Bathymetry of the northern Newfoundland Basin showing the locations of Sites 1276 and 1277.

Figure F8. SCREECH line 2MCS from the central Newfoundland continental rise seaward to oceanic crust east of Anomaly M0, illustrated in three sections. Location is shown in Figure F6. A. Lower continental rise. The basement block at center is the landward side of the Flemish Hinge and is capped by probably lower Mesozoic, prerift sediments. Major deep-basin reflections and seismic sequences to the east are identified. B. Lowermost continental rise and western margin of the abyssal plain with Sites 1276 and 1277, major reflections, seismic sequences, and magnetic anomaly locations identified. C. Seaward portion over the abyssal plain, with Horizon A^u and location of Anomaly M0 indicated. CMP = common midpoint, Unc. = unconformity.

Figure F9. Simplified interpretation of SCREECH line 2MCS across the Newfoundland continental margin, with magnetic anomaly locations of Srivastava et al. (2000) indicated. Line location is shown in Figure F5.

Figure F10. Isopach map of the U–basement interval showing two-way traveltime between the U reflection and basement, based on MCS profiles of the SCREECH survey (Ewing cruise 00-07) along transect 2. Locations of Sites 1276 and 1277 are indicated. Note that the deposits below the U reflection fill depressions between basement ridges. Interpretation of an U–basement interval southeast of Site 1277 is tentative; the U reflection cannot be traced continuously to this location from farther west in existing seismic data, and the possible U reflection there is inferred only on the basis of reflection character and depth (see, e.g., Fig. F9 for one example of possible occurrence of U in this zone).

Figure F11. Schematic models to explain observed deep structural asymmetries between the Newfoundland (left) and Iberia (right) transition zones. A. Synrift extension of continental crust. In the central part of the rift, lower crust is thinned ductilely (dashes) but brittle upper crust has limited tectonic extension (e.g., Driscoll and Karner, 1998). B. Anomaly ~M3; the rift evolves asymmetrically, with a thin remnant of continental crust forming an upper, Newfoundland plate, and serpentinized peridotite and remnants of ductilely thinned lower crust forming a lower, Iberia plate. Bending stresses may account for faulting in the cold, brittle mantle footwall as it is exhumed on the Iberia side. Differences of basement depth on the two margins reflect buoyancy of thin continental crust (shallow) vs. serpentinized mantle (deep). The U reflection could be compared to a synrift unconformity developed near sea level, basalt flows, or high-velocity sediments (see C and D). C. Alternate model at Anomaly ~M3; mantle is exposed on both sides of the rift at an early stage, followed by development of an asymmetric shear. Melt extracted from the lower plate may permeate the Newfoundland upper plate and flood its surface to form the U-to-basement sequence in a submarine setting. Basement depth differences between the two margins reflect buoyancy differences caused by melt intrusion/extrusion on the Newfoundland side. D. Second alternate model at Anomaly ~M3; ultra-slow seafloor spreading. Symmetrical spreading is unlikely because it would not account for extensive exposure of serpentinized mantle on the Iberia side or asymmetry in basement structure of the transition zones on the two margins. Rather, ocean crust may have formed in the western part of the rift by seafloor spreading after initial exposure of mantle, with the ocean crust subsequently being isolated on the Newfoundland side by a jump of the spreading axis (from a failed rift [FR] eastward to a more central location). The U–basement sequence might be explained by basalt flows capping the ocean crust or as a high-velocity sedimentary sequence. More buoyant Newfoundland ocean crust would be shallower than serpentinized mantle on the Iberia side, and differences in basement roughness would reflect dissimilar tectonic extension in the two kinds of lithosphere. MOHO = Mohorovicic discontinuity.

Figure F12. Proposed drilling and casing plan for the deep hole drilled at Site 1276. RCB = rotary core barrel, VSP = vertical seismic profile.

Figure F13. Synthesis of lithostratigraphic units recognized at Site 1276. Columns show recovery (solid black boxes), age, lithology on a core-by-core basis (see separate key), grain size and color variation (pseudoweathering profile and separate color key), and primary characteristics.

Figure F14. Close-up photograph of typical poorly sorted muddy sandstone of lithologic Unit 4 (interval 210-1276-29R-1, 90–120 cm). Note the intense burrowing and reddish color attributed to well-oxygenated bottom waters.

Figure F15. Close-up photograph of massive, poorly sorted grainstone with carbonate granules (mainly bioclasts) and abundant large mud clasts in lithologic Unit 1 (interval 210-1276A-7R-2, 16–41). The sediment has a swirled appearance because of soft-sediment deformation and differential compaction.

Figure F16. Close-up photograph of central part of a chaotic mud-clast conglomerate in lithologic Subunit 5C (interval 210-1276A-93R-3, 70–97 cm). Note the range in color of the mudstone clasts and the variety of clast shapes.

Figure F17. Close-up photograph of an excellent example of repeated graded beds in lithologic Unit 2 (interval 210-1276A-9R-2, 96–120 cm). Note the sharp bases of these turbidites and upward fining into burrowed and laminated intervals.

Figure F18. Close-up photograph of planar-laminated carbonate grainstone grading upward into marlstone in lithologic Unit 3 (interval 210-1276A-19R-5, 80–112 cm). Above 99 cm, there are contorted and flattened laminae and pockets of silt that formed when the sediment was in a plastic state.

Figure F19. Close-up photograph of middle part of a highly disorganized gravity flow deposit in lithologic Subunit 5C (interval 210-1276A-89R-6, 80–115 cm). Note the planar lamination (at 104–111 cm) passing upward into a convoluted and swirled interval (at 81–100 cm). Such flow features characterize this lithologic subunit.

Figure F20. Comparison of (A) core photograph and (B) computed tomography (CT) scan of a porphyroblastic mudrock created by thermal and hydrothermal effects of the intrusion of the upper diabase sill in lithologic Subunit 5C (interval 210-1276A-87R-6, 18–27 cm). The CT scan is a horizontal slice through a three-dimensional reconstructed image, viewed with IMAGEJ software. Note the apparent near-random orientation of the porphyroblasts.

Figure F21. Close-up photograph of very finely laminated black shale with planar siltstone laminae and a small siltstone lens (at 96 cm) in lithologic Subunit 5B (interval 210-1276A-43R-2, 88–117 cm).

Figure F22. Simplified time-stratigraphic chart comparing the lithostratigraphic successions encountered on the Newfoundland and Iberia conjugate margins. For comparison, a similar summary is provided (at right) for the geographically separate North American Basin in the western central North Atlantic. Lithologic units are shown on the left sides of the columns, and the thickness of the units are shown on the right sides. TD = total depth.

Figure F23. Summary of core recovery and observations of segregation bands, grain size, degree of alteration, thin section sample locations, textures, and minerals from X-ray diffraction data for the upper igneous sill at Site 1276. Photomicrographs 2i, 13i, and 6i show the texture denoted in the texture column. Photomicrograph 4i shows the composition of a segregation band. The alteration is shown with gray shades, where dark gray is complete alteration and lighter shades are moderate. The recovery of the core is shown in red. Plag = plagioclase, cpx = clinopyroxene, mag = magnetite.

Figure F24. Age-depth plot based on first and last occurrences datums (FOs and LOs) of microfossils at Site 1276 and DSDP Site 398. Dashed lines represent intervals in which no samples were analyzed, age-diagnostic datums are uncertain, or in which samples were found to be barren. Approximate sedimentation rates at Site 1276 which are based on calcareous nannofossils are shown in blue, while those based on palynomorphs are depicted in red.

Figure F25. Downhole plots of CaCO₃, TOC, C₁, and C₂ concentrations and C/N ratios, Site 1276. Core lithology and recovery are shown on the left.

Figure F26. Composite physical property plots of smoothed NGR, z-velocity, bulk density, and porosity plotted against depth and for Site 1276, with lithology, lithologic boundaries, and grain size also indicated. Lithology and sedimentary facies keys are also shown.

Figure F27. Schematic lithologic column in a "weathering profile," x-velocity, porosity, and methane (C₁) plots vs. depth for the lowermost 50 m of Site 1276 (1675–1725 mbsf). Right-hand border on the lithologic column indicates relative degree of compaction. Black circles indicate shipboard measurements. Dashed red lines are trend lines for each data set for sediments in lithologic Subunit 5C above the anomalous sediments.

Figure F28. (top) Time-migrated seismic SCREECH profile 2MCS with location of main seismic reflections and location of Site 1276; (bottom) Time-migrated IFP-CNEXO seismic profile GP-19 (Bouguigny and Wilm, 1979) with location of main seismic reflections and location of Site 398. CMP = common midpoint.

Figure F29. Correlation between seismic sequences and lithologic breaks and age at Site 1276 and that at Site 398 (Shipboard Scientific Party, 1979). CMP = common midpoint.

Figure F30. Isopach map of acoustic Unit 4 beneath the orange reflection on the Iberia margin. Sources are: (1) the isopach map of acoustic Unit 4 by Réhault and Mauffret (1979) from available seismic data in 1975; (2) MCS lines acquired in 1997 by the Maurice Ewing during the Iberian Seismic Experiment (ISE, Dale Sawyer, Principal Investigator), MCS line IAM 9 (Pickup et al., 1996), and MCS line Lusigal 12 (Beslier, 1996); (3) the Iberia Abyssal Plain basement map (Shipboard Scientific Party, 1998) compiled from all available seismic data in the IAP; and (4) a detailed bathymetric map of the northeast Atlantic Ocean (Loubrieu et al., 2002).

Figure F31. Sedimentation rates at Sites 398 (Shipboard Scientific Party, 1979) and 1276; timescale from Berggren et al. (1995) and Gradstein et al. (1995). Site 398 seismic sequence (numbers) (Shipboard Scientific Party, 1979) and Site 1276 seismic sequence (letters) are shown.

Figure F32. Schematic illustration of actual Site 1276 installation and cored intervals. The depth of the seafloor was determined by observing a reduction in drill string weight, so the seafloor depth of 4549.1 m below sea level is likely deeper than the true sediment/water interface. The exact sediment thickness over the reentry cone is unknown. ODL = Overseas Drilling, Ltd.

Figure F33. Breakdown of operational activities while on site.