Figure F1. Map of the central tropical Pacific showing (A) Leg 199 drill sites and DSDP drill sites in the region superimposed on bathymetry and (B) Leg 199 drill sites superimposed on the approximate position of magnetic Anomaly C25n (58.9–56.4 Ma), the target crust for the 56-Ma transect.
Figure F2. Chlorophyll contents in the Pacific equatorial region, from SeaWIFS satellite, September 1997–July 1998 composite. The high-productivity band along the equator is constrained to its position by ocean physics. Red = highest chlorophyll contents, dark purple = lowest chlorophyll.
Figure F3. Position and thickness of the equatorial sediment bulge in the equatorial Pacific Ocean. The thickest pile of sediments is displaced from the equator by the northwestward movement of the Pacific plate. Because of Pacific plate movement, Paleogene equatorial sediments lie beneath a relatively thin Neogene sediment column.
Figure F4. Sites along the 56-Ma Leg 199 transect, superimposed on model estimates of upwelling from a new early Eocene coupled ocean-atmosphere climate model. Lines with arrows = current streamlines at the approximate depth of the thermocline. Compare the upwelling pattern in this model with the chlorophyll distribution in Figure F2, an indicator of modern upwelling.
Figure F5. Compilation of benthic oxygen isotope data for the Cenozoic (Zachos et al., 2001a). Also shown is the time window investigated during ODP Leg 199 and the position of three major events targeted by the leg. P-E marks the position of the Paleocene/Eocene boundary and its associated thermal event. Oi-1 is approximately at the Eocene/Oligocene boundary and marks the first major Antarctic glaciation. Mi-1 is near the Oligocene/Miocene boundary and marks a the beginning of the development of the Neogene cryosphere.
Figure F6. Lithologic summary for Leg 199. Individual units at each site are correlated to each other. The abundance of carbonate ooze in the Oligocene–upper Miocene sequence at Site 1218 suggests this site was above the CCD after the late Eocene. O/M = Oligocene/Miocene boundary, E/O = Eocene/Oligocene boundary.
Figure F7. LAS (300–2500 nm) determined concentrations for smectite and illite vs. depth for sites that contained an illite to smectite transition.
Figure F8. Illite–smectite transition plotted as a function of age and latitude. The transition most likely tracks the paleoposition of the ITCZ because it marks the switch from Asian dust sources (illite rich) to American sources (smectite rich).
Figure F9. Lithologic columns for Sites 1218, 1219, 1220 and 1221 showing where diatoms are common to abundant (>10% based on smear slide analysis). Diatoms are a significant constituent of sediments from all the southern sites during the RP15 radiolarian zone (upper middle Eocene). RP19 and 20 (basal Oligocene) is diatom rich, with the exception of Site 1219. At Site 1219, a pronounced peak in diatom abundance is found in upper Oligocene sediments. O/M = Oligocene/Miocene boundary, E/O = Eocene/Oligocene boundary, P/E = Paleocene/Eocene boundary.
Figure F10. Composite digital photographs of the late Eocene "pentachert" interval of Site 1218 plotted against gamma ray attenuation (GRA) bulk density (uncleaned data) in Sections 199-1218A-25X-1 and 25X-2, 199-1218B-25X-1, and 199-1218C-18X-3 and 18X-4. Five chert layers of early Paleocene age were recovered intact and can be observed through all holes drilled at Site 1218. The contacts of the radiolarite of Unit III and these lithified chert layers are gradational. More of these intact chert layers were observed in Cores 199-1218A-27X and 199-1218C-18X, 19X, and 20X.
Figure F11. Composite digital photographs of cores taken across the E/O boundary at Site 1218 using the shipboard GEOTEK digital imaging system. At Site 1218 (shallowest 42-Ma crust) it is clear that the Eocene–Oligocene carbonate transition is a two-step process. At Site 1219 (deeper 55-Ma crust) only one step can be observed.
Figure F12. A. Subsidence history of nonequatorial Leg 199 sites (1215, 1217, and 1221). Estimated calcite compensation depth (CCD) based on presence/absence of carbonate is also shown. B.ÝSubsidence history of equatorial Leg 199 sites (1218, 1219, and 1220). The estimated CCD based on presence/absence of carbonate is also shown.
Figure F13. Relative position of the paleoequator for the middle Eocene and late Oligocene based on data from Sites 1218, 1219, and 1220. The main oceanic magnetic anomalies as well as the major fracture zone are shown in blue. For each site, we have computed a mean declination and inclination for two different intervals, 26 and 39 Ma. Mean sites declination (less accurately oriented) have then been adjusted for the expected paleomagnetic pole for the Pacific plate of the appropriate age. The map was constructed using GMAP32 (Torsvik and Smethrust, 1989–1997).
Figure F14. Inferred paleolatitudes for Sites 1218, 1219, and 1220 based on mean paleomagnetic inclinations, using the dipole formula. Error bars represent the maximum difference obtained from different holes around their mean. Site 1218 has not produced data older than the Oligocene. Notice that Site 1219 crosses the equator much later than Site 1220. Data points at 0 Ma are the present-day latitudes of the studied sites.
Figure F15. Interstitial water profiles from Leg 199 sites. Profiles reflect the limited organic matter diagenesis and relatively high biogenic silica contents at these sites. Only Site 1219 has the "typical" Ca and Mg profile indicating an exchange of seawater Mg for basalt Ca during crustal alteration.
Figure F16. Shipboard ICP-OES analyses of sedimentary Si and Ca weight percent and mass accumulation rate (MARs). MAR is a product of sedimentation rate, elemental weight percent, and dry bulk density.Si largely represents biogenic silica, whereas Ca represents CaCO3.
Figure F17. Summary of sedimentation rates derived from age-depth models at each of the Leg 199 drill sites. MAR is a product of sedimentation rate, elemental weight percent, and dry bulk density.
Figure F18. Shipboard ICP-OES analyses of sedimentary Al and P weight percent and mass accumulation rate (MARs). MAR is a product of sedimentation rate, elemental weight percent, and dry bulk density. Al represents detrital aluminosilicate deposition while P is delivered to the seafloor by primary productivity.
Figure F19. Si/Ti, Ba/Ti, and Al/Ti of Leg 199 sediments. Relatively constant Al/Ti suggests that the detrital sources had similar amounts of these elements. High Si/Ti reflects high biogenic opal deposition, whereas high Ba/Ti reflects high biogenic Ba burial.
Figure F20. Latitudinal transect of Si mass accumulation rate (MARs) for three time slices: early Oligocene (25–34 Ma), middle Eocene (38–45 Ma), and early Eocene (50–55 Ma). Si accumulation in the early Eocene is low and probably has a major contribution from detrital aluminosilicates. Middle Eocene Si accumulation is high, about double modern opal accumulation at the equivalent longitude. Early Oligocene Si accumulation resembles that of modern sediments (Lyle, 1992).
Figure F21. Latitudinal transect of Ca mass accumulation rate (MARs) for three time slices: early Oligocene (25–34 Ma), middle Eocene (38–45 Ma), and early Eocene (50–55 Ma). Ca MAR almost exclusively results from the deposition of CaCO3. The early Oligocene pattern of Ca MAR is the only one that resembles the Neogene in both shape and magnitude. CaCO3 is essentially absent from middle Eocene sediments along the 56-Ma transect but is present intermittently at the southern end of the transect. The early Eocene Ca MAR is about half of modern flux, and curiously, equatorial Ca MAR is significantly less than the off-axis flux.
Figure F22. Synthesis of magnetic stratigraphy from four Leg 199 drill sites. Depth scale in mcd is shown on the right of each column, and geographic coordinates are shown at the bottom of each column. Black = normal magnetic chrons, white = reversed magnetic chrons, gray = no polarity assignation possible. Crosses = intervals with no data, dashed lines = correlation between selected chrons to the GPTS (Cande and Kent, 1995).
Figure F23. Comparison of estimated ages of radiolarian zones (Sanfilippo and Nigrini, 1998) to age boundaries intercalibrated with magnetic reversal stratigraphy on Leg 199. Significant improvements of zone boundary ages have occurred because of Leg 199 shipboard studies.
Figure F24. Digital photograph of the record of the Oligocene–Miocene transition and Mi-1 glacial step at ODP Site 1218. Lithology and magnetic susceptibility records show the distinct cyclicity in carbonate content and physical properties observed around the O/M boundary. Together with unambiguous magnetostratigraphy and biostratigraphy, the cycle record contributes to the first high-resolution astronomical-calibrated chronology for the O/M boundary in the Pacific. Bioevents such as the first and last appearance datums of the clacareous nannofossil, Sphenolithus delphix, and the appearance datum of the foraminifer Paragloboroatlia kugleri are identical within current resolution to these same events in the Atlantic Ocean. Hence, we have no doubt that the Site 1218 record will become a standard reference section for the Oligocene–Miocene interval in the Pacific that can be correlated precisely to Atlantic sites that typically lack unambiguous magnetochronologies.
Figure F25. MST, paleomagnetic, and biostratigraphic data from Site 1218 and Site 1219 plotted on a common timescale (developed mainly from paleomagnetic reversal datums that were composited from both sites after matching of lithologic cycles). Note the close correspondence between MST data from the two drill sites and calculated sedimentation rates. Biostratigraphic nannofossil datums and their uncertainty intervals agree well, whereas datums based on certain foraminifera do not agree. Gray-shaded boxes = ages of magnetic reversals (Cande and Kent, 1995). VGP = virtual geomagnetic pole. GRA = gamma ray attenuation.
Figure F26. Composite digital photographs showing the Eocene–Oligocene sequence at each site and composite gamma ray attenuation (GRA) bulk density, magnetic susceptibility, and color reflectance data. The lithologic change from carbonate-rich to carbonate-poor sediments is evident as a two-step decrease in GRA density and an increase in susceptibility at Site 1218.
Figure F27. Composite digital photographs of the E/O boundary during ODP Leg 199 using biostratigraphic (nannofossil and radiolarian) and magnetostratigraphic data. The position of the boundary (at the 33.7-Ma isochron) has been calculated through linear interpolation between paleomagnetic and/or biostratigraphic indications. E/O = Eocene/Oligocene boundary.
Figure F28. Composite digital photographs of the correlation and comparison of the E/O boundary sections recovered during Leg 199. At four of the five sites from which this interval was recovered, cores from Holes A, B, and C overlap to produce continuous complete sections. At Site 1219 only one hole penetrated the boundary, and a small coring gap is present in the section. Refer to Figure F27 for biostratigraphic datums. E/O = Eocene/Oligocene boundary.
Figure F29. Comparison of diatom events (>5% diatoms in the sediments) to estimated position of equator crossings in lower Oligocene–lower Eocene sediments from the 56-Ma transect. Equator crossings have been estimated by shipboard paleomagnetics and by using a fixed hotspot model of Pacific plate motion. Diatom events are not clustered at equator crossings. F.Z. = fracture zone.
Figure F30. Digital photographs of the P/E boundary sediments recovered at Sites 1220 and 1221. Lower Eocene calcareous chalks grade downcore into multicolored clay-rich lithologies. The last occurrence of Paleocene fauna is recorded at the base of the brown clay, and the first occurrence of Eocene assemblages is at the top of the dark brown clay. Calcareous fossils are barren to poorly preserved in the multicolored clay layers, and percentage CaCO3 values are very low. FO = first occurrence, LO = last occurrence.
Figure F31. Digital photograph of the >63-boundary. The following major grains are observed at each depth interval: Planktonic foraminifers (intervals 199-1220B-20X-2; 13–20, 28–35, 35–43, and 42–50 cm; 198.90–199.40 mbsf), pink brown grains and dolomite crystals (interval 199-1220B-20X-2; 50–57 cm; 199.40–199.47 mbsf), black grains and sediment lumps (interval 199-1220B-20X-2; 57–64.5 cm; 199.47–199.55 mbsf), large pinkish grains with many dolomite crystals (interval 199-1220B-20X-2; 65–72 cm; 199.55–199.62 mbsf), small pink brown grains with rare planktonic foraminifers and dolomite grains (interval 199-1220B-20X-2; 74–78 cm; 199.64–199.68 mbsf), and dolomite grains and rare benthic foraminifers (interval 199-1220B-20X-2; 77.5–85 and 85–95 cm; 199.68–199.85 mbsf).
Figure F32. Digital photograph of the stratigraphic distribution of benthic foraminifers in Section 199-1220B-20X-2 (198.90–199.85 mbsf). Red triangles at 199.68 mbsf = P/E boundary as represented by the benthic extinction event is shown by red triangles at 199.68 mbsf.
Figure F33. A. Composite digital photograph of shipboard ICP-OES analyses of Si, Al, Ti, Fe, and Mg on 2-cm bulk sediment scrapes across the Paleocene–Eocene (P/E) boundary from Sites 1220 and Sites 1221. Elevated concentrations of all these elements in the boundary interval reflect low CaCO3. Different levels of elements through the interval reflect the distinct color bands. B. Composite digital photograph of shipboard ICP-OES analyses of Ca, Sr, Ba, P, and Mn on 2-cm bulk sediment scrapes across the P/E boundary from Sites 1220 and Sites 1221. The difference in behavior between Ca and Sr reflects recrystallization. A strong Mn peak flanked by P and Ba peaks is characteristic of the boundary interval.