(Table T1) Calcium carbonate mineralogy and stable isotopic composition of ODP Hole 182-1132C sediments

Petrographic observation and carbonate mineralogic and stable isotopic investigation were conducted on lower Oligocene to middle Miocene sediments recovered during Ocean Drilling Program Leg 182 from Site 1132, located at a water depth of 218.5 m immediately seaward of the shelf-slope break of the eastern Eyre Terrace in the western Great Australian Bight. The middle Miocene section consists of bioclastic packstone and grainstone with an interval of partially silicified nannofossil-foraminiferal chalk and is slightly to densely dolomitized. By contrast, the lower Oligocene to lower Miocene section is characterized by a predominance of planktonic and benthic foraminifers, high porosity, absence of chert, and weak dolomitization. The carbon and oxygen isotopic composition of calcites and dolomites between two sections, however, shows no significant difference.

Geochemistry and strontium isotopic composition of interstitial waters of marine carbonates

The concentrations and isotopic compositions of strontium in interstitial waters from several DSDP sites, where sediments consist chiefly of carbonate oozes and chalks, are used as indicators of carbonate diagenesis by reference to a recently-produced curve showing detailed variations in the 87Sr/86Sr ratio of seawater with time. Carbonate sediments of the Walvis Ridge show increases in interstitial Sr[2+] concentrations in the upper carbonate-ooze sections with the highest concentrations near the ooze-chalk boundary where maximum rates of carbonate recrystallization occur. Below this, in situ production of Sr[2+] diminishes and there is a diffusive flux of Sr to an underlying sink, presumably volcanogenic sediments or basalts, leading to Sr isotopic disequilibrium between carbonates and interstitial waters. In some other sites, however, there is no apparent Sr sink at depth and isotopic equilibrium is retained. Overall, diffusive smoothing of profiles exerts an important control on the 87Sr/86Sr ratios, although lower ratios than contemporaneous seawater values in the carbonate oozes often correlate with zones of Mg[2+] loss and reflect a combination of a flux of Sr[2+] from the zone of maximum recrystallization rates together with a contribution from the in situ alteration of volcanic matter.

(Table 2) Aragonite, high and low magnesium calcite, major elements, bioclast and planktic foraminifera from ODP Hole 133-817A

Investigation of the Middle Miocene-Pleistocene succession in cores at ODP Site 817A (Leg 133), drilled on the slope south of the Queensland Plateau, identified the various material fluxes contributing to sedimentation and has determined thereby the paleogeographic events which occurred close to the studied area and influenced these fluxes. To determine proportions of platform origin and of plankton origin of carbonate mud, two reference sediments were collected: (1) back-reef carbonate mud from the Young Reef area (Great Barrier Reef); and (2) Late Miocene chalk from the Loyalty Basin, off New Caledonia. Through their biofacies and mineralogical and geochemical characters, these reference sediments were used to distinguish the proportions of platform and basin components in carbonate muds of 25 core samples from Hole 817A. Two "origin indexes" (i1 and i2) relate the proportion in platform and basin materials. The relative sedimentation rate is inferred from the high-frequency cycles determined by redox intervals in the cores. Bulk carbonate deposited in each core has been calculated in two ways with close results: (1) from calcimetric data available in the Leg 133 preliminary reports (Davies et al., 1991); and (2) from average magnetic susceptibility of cores, a value negatively correlated to the average carbonate content. Vertical changes in sedimentation rates, in carbonate content, in origin indexes and in "linear fluxes" document the evolution of sediment origins from platform carbonates, planktonic carbonates and insoluble material through time. These data are augmented with the variations in organic-matter content through the 817A succession. The observed changes and their interpretation are not modified by compaction, and are compatible with major paleogeographic events including drowning of the Queensland Plateau (Middle Miocene-Early Pliocene) and the renewal of shallow carbonate production, (1) during the Late Pliocene, and (2) from the Early Pleistocene. The birth and growth of the Great Barrier Reef is also recorded from 0.5 Ma by a strengthening of detrital carbonate deposition and possibly by a lack of clay minerals in the 4 upper cores, a response to trapping of terrigenous material behind this barrier. In addition, a maximum of biological silica production is displayed in the Middle Miocene. These changes constrain the time of events and the sequence-stratigraphy framework some components of which are transgression surface, maximum flooding surface and low-stand turbidites. Sedimentation rates and material fluxes show cycles lasting 1.75 Myr. Whatever their origin (climatic and/or eustatic) these cycles affected the planktonic production primarily. The changes also show that major carbonate variations in the deposits are due to a dilution effect by insoluble material (clay, biogenic silica and volcanic glasses) and that plankton productivity, controlling the major fraction of carbonate sedimentation, depends principally on terrigenous supplies, but also on deep-water upwelling. Accuracy of the method is reduced by redeposition, reworking, and probable occurrence of hiatuses.

(Table 1) Age and depth of reflectors of the 3.5-kHz and airgun seismic record and their corresponding depth of ash layers, carbonate peaks, and transition zones from DSDP Hole 83-504B

DSDP cores from areas of low (Site 505) and high heat flow (Site 504 B) near the Costa Rica Rift, together with seismic profiles from the Panama Basin, have been studied to determine the relationship between: (1) carbonate content and physical and acoustic properties; and (2) carbonate content, carbonate diagenesis and acoustic stratigraphy. Except for ash and chert layers, bulk density correlates strongly and linearly with carbonate content. Velocity is uniform downcore and only small variations at a small scale are measured. Thus an abrupt change in carbonate content will cause abrupt changes in acoustic impedance and should cause reflectors that can be detected acoustically. A comparison of seismic profiler reflection records with physical properties, carbonate content and reflection coefficients indicates that the main reflectors can be identified with ash layers, diagenetic boundaries, and carbonate content variations. Diagenesis of carbonate sediments is present at Site 504B in a 260 m-thick ooze-chalk-limestone/chert sequence. These diagenetic sequences occur in areas of higher heat flow (200 mW/m**2). Seismic profiler records can be used to map the extent and depth of these diagenetic boundaries.

Interstitial water chemistry of DSDP Leg 85 sites

The concentration changes in pore waters of dissolved calcium, magnesium, sulfate, strontium, and silica and of alkalinity are controlled by diagenetic reactions occurring within the biogenic sediments of DSDP Sites 572, 573, and 574. Downcore increases in dissolved Sr2 + indicate recrystallization of calcite, and increases in dissolved SiO2 reflect dissolution of amorphous silica. Minor gradients in dissolved Ca(2+) and Mg(2+) suggest little if any influence from reactions involving volcanic sediments or basalt. Differences in interstitial water profiles showing the downhole trends of these chemical species mark variations in carbonate and silica diagenesis, sediment compositions, and sedimentation rate histories among the sites. The location and extent of carbonate diagenesis in these sediments are determined from Sr/Ca distributions between the interstitial waters and the bulk carbonate samples. Pore water strontium increases in the upper 100 to 250 m of sediment are assumed to reflect diffusion from underlying zones where calcite recrystallization has occurred. On the basis of calculations of dissolved strontium production and comparisons between observed and calculated "equilibrium" Sr/Ca ratios of the solids, approximately 30 to 50% of the carbonate has recrystallized in these deeper intervals. These estimates agree with the observed amounts of chalk at these sites. Variations in Sr/Ca ratios of these carbonates reflect differences in calcareous microfossil content, in diagenetic history, and, possibly, in changes in seawater Sr/Ca with time. Samples of porcelanite recovered below 300 m at Site 572 suggest formation at temperatures 20 to 30° C greater than ones estimated assuming oceanic geothermal gradients from sedimentary sections similar to those recovered on Leg 85. The higher temperatures may partially account for higher Sr/Ca ratios determined for recrystallized carbonates from this site.

(Appendix) Range chart of calcareous nannofossils in ODP Hole 129-802A

Only Site 802 has recorded appreciable Cenozoic carbonate sediments during Ocean Drilling Program Leg 129 in the central Mariana Basin of the western Pacific Ocean. Calcareous nannofossils provide the best biostratigraphic information for the 360-m Tertiary section, which consists primarily of volcaniclastic turbidites interbedded with calcareous claystone and chalk. Many samples contain significant amounts of nannofossils reworked from older sediments. An unconformity appears to be present between Cores 129-802A-32R and -33R, with upper Oligocene-lower Miocene sediments above and lower Eocene-upper Paleocene sediments below the unconformity. The sediments below the unconformity contain abundant reworked Cretaceous nannofossils. Only one sample from Site 801 yielded nannofossils, and those consist of a mixture of Campanian-Maastrichtian and Paleogene forms.

Abundance of calcareous nannofossils across the K/T boundary at ODP Hole 113-690C (Table 1)

A biostratigraphically continuous, but intensely bioturbated, Cretaceous/Tertiary boundary sequence was cored during Ocean Drilling Program (ODP) Leg 113 on Maud Rise (65°S) in the Weddell Sea off East Antarctica. This interval is the first recovered by ODP/DSDP in the South Atlantic sector of the Southern Ocean and offers a unique opportunity to study the nannofossil sequences leading up to and beyond the terminal Cretaceous event at a high southern latitude. The K/T boundary lies just within Chron 29R and is placed at ODP Sample 113-690C-15X-4, 41.5 cm. An iridium anomaly was independently noted at about this level as well. Upper Maestrichtian-lower Paleocene sediments consist mostly of light-colored nannofossil chalks. Dark brown sediments at the base of the Danian (Zone CPla) are characterized by an increased clay content attributed to a drop in calcareous microplankton productivity following the terminal Cretaceous event. Although delineation of the boundary is hampered by intense bioturbation, the sharp color contrast between overlying clay-rich, dark brown chalks of the Tertiary and light cream colored chalks of the Cretaceous aids in the selection of the K/T horizon. Several dark colored burrows sampled at intervals as far as 1.3 m below the boundary and within the light colored Cretaceous chalk were found to contain up to 17% Tertiary nannofossils. Calcareous nannofossils from the boundary interval were divided into three groups for quantitative study. The three groups, "Cretaceous," "Tertiary," and "Survivor," exhibit a sequential change across the boundary with the Cretaceous forms giving way to a Survivor-dominated assemblage beginning at the boundary followed shortly thereafter by the appearance of the Tertiary taxa, Cruciplacolithus and Hornibrookina. The species, H. edwardsii, comprises nearly 50% of the assemblage just above the Zone CPla/CPlb boundary, an abundance not reported elsewhere at this level. Calculation of individual species abundances reveals several additional differences between this K/T boundary interval and those studied from middle and low latitude sections. The percentage of Thoracosphaera is much lower at the boundary in this section and a small form, Prediscosphaera stoveri, is extremely abundant in Cretaceous sediments just below the boundary.

(Table 1) Magnetic characteristic properties of selected samples of ODP Hole 134-831B

During Ocean Drilling Program Leg 134 (Vanuatu), geological high sensitivity magnetic tools (GHMT) developed by CEA-LETI and TOTAL were used at two drill sites. GHMT combine two sensors, a proton magnetometer for total magnetic field measurements with an operational accuracy of 0.1 nanoteslas (nT), and a highly sensitive induction tool to measure the magnetic susceptibility with an operational accuracy of a few 10**-6 SI units. Hole 829A was drilled through an accretionary prism and the downhole measurements of susceptibility correlate well with other well-log physical properties. Sharp susceptibility contrasts between chalk and volcanic silt sediment provide complementary data that help define the lithostratigraphic units. At Hole 831B magnetic susceptibility and total field measurements were performed through a 700-m reef carbonate sequence of a guyot deposited on top of an andesitic volcano. The downhole magnetic susceptibility is very low and the amplitude of peak-to-peak anomalies is less than a few 10**-5 SI units. Based on the repeatability of the measurements, the accuracy of the magnetic logging measurements was demonstrated to be excellent. Total magnetic field data at Hole 831B reveal low magnetic anomalies of 0.5 to 5 nT and the measurement of a complete repeat section indicates an accuracy of 0.1 to 0.2 nT. Due to the inclination of the earth's magnetic field in this area (~-40°) and the very low magnetic susceptibility of the carbonate, the contribution of the induced magnetization to the total field measured in the hole is negligible. Unfortunately, because the core recovery was extremely poor (<5%) no detailed comparison between the core measurements and the downhole magnetic data could be made. Most samples have a diamagnetic susceptibility and very low intensity of remanent magnetization (< 10**-4 A/m), but a few samples have a stable remanent magnetization up to 0.005 A/m. These variations of the intensity of the remanent magnetization suggest a very heterogeneous distribution of the magnetization in the carbonate sequence that could explain the magnetic field anomalies measured in these weakly magnetized rocks.

Carbon isotope record of 3 profiles from Campanian-Maastrichtian

Carbon-isotope stratigraphy has proven to be a powerful tool in the global correlation of Cretaceous successions. Here we present new, high-resolution carbon-isotope records for the Global Boundary Stratotype Section and Point (GSSP) of the Maastrichtian stage at Tercis les Bains (France), the Bottaccione and Contessa sections at Gubbio (Italy), and the coastal sections at Norfolk (UK) to provide a global d13C correlation between shelf-sea and oceanic sites. The new d13C records are correlated with d13C-stratigraphies of the boreal chalk sea (Trunch borehole, Norfolk, UK, Lägerdorf-Kronsmoor-Hemmoor section, northern Germany, Stevns-1 core, Denmark), the tropical Pacific (ODP-Hole 1210B, Shatsky Rise) and the South Atlantic and Southern Ocean (DSDP Hole 525A, ODP Hole 690C) by using an assembled Gubbio d13C record as a reference curve. The global correlation allows the identification of significant high-frequency d13C variations that occur superimposed on prominent Campanian-Maastrichtian events, namely the Late Campanian Event (LCE), the Campanian-Maastrichtian Boundary Event (CMBE), the mid-Maastrichtian Event (MME), and the Cretaceous-Paleogene transition (KPgE). The carbon-isotope events are correlated with the geomagnetic polarity scale recalculated using the astronomical 40Ar/39Ar calibration of the Fish Canyon sanidine. This technique allows the evaluation of the relative timing of base occurrences of stratigraphic index fossils such as ammonites, planktonic foraminifera and calcareous nannofossils. Furthermore, the Campanian-Maastrichtian boundary, as defined in the stratotype at Tercis, can be precisely positioned relative to carbon-isotope stratigraphy and the geomagnetic polarity timescale. The average value for the age of the Campanian-Maastrichtian boundary is 72.1 ± 0.1 Ma, estimated by three independent approaches that utilize the Fish Canyon sanidine calibration and Option 2 of the Maastrichtian astronomical timescale. The CMBE covers a time span of 2.5 Myr and reflects changes in the global carbon cycle probably related to tectonic processes than to glacioeustasy. The duration of the high-frequency d13C variations instead coincides with the frequency band of long eccentricity, indicative of orbital forcing of changes in climate and the global carbon cycle.

(Table 1) Distribution of Cretaceous-Tertiary benthic foraminifers in ODP Hole 129-802A

Reworked shallow-water larger and deep-water calcareous benthic foraminifers were recovered from foraminiferal packstones and nannofossil chalks in Hole 802A. The autochthonous zeolitic pelagic claystone is characterized by late Campanian abyssal agglutinated foraminifers that allow correlation with the North Atlantic and the adjacent Pigafetta Basin. Assemblages of DendrophryalRhizammina in graded beds within the zeolitic claystone indicate reworking through entrainment in the flocculent E layer of turbidites, rather than recolonization following a biosiliceous event. Background sedimentation of the claystone took place below the carbonate compensation depth. The nannofossil chalk contains reworked lower bathyal to abyssal calcareous foraminifers of late Paleocene to early Miocene age. The topmost bed of the nannofossil chalk unit commences with an algal foraminiferal packstone containing Lepidocyclina sumatrensis, Heterostegina borneensis, Amphistegina hauerina, Asterigerina marshallana, and A. tentoria, which indicate that the source area was a shallow-water reef and allow the bed to be dated as early Miocene. The absence of obviously younger planktonic microfossils in the graded bed indicates that the resedimentation event was generally contemporaneous with original deposition and took place during an early Miocene global sea-level highstand. An early Miocene shallow-water assemblage is also seen in the graded beds at the base of a volcaniclastic turbidite sequence overlying the nannofossil chalks. Resedimentation of this unit was associated with volcanic activity some distance away.

(Table T1) Mineralogy and geochemistry of ODP Hole 192-1183A and Hole 192-1186A sediments, Ontong Java Plateau

Boron, Ca, Na, and Gd concentrations and H intensity in sediments obtained during Ocean Drilling Program Leg 192 were determined by prompt gamma neutron activation analysis. The results show strong positive correlation between B content and H intensity in carbonate samples; chalk samples have higher B contents than limestone samples. Average B content is 9.1 ppm for the chalk and 5.2 ppm for the limestone. When chert blocks or clay minerals are present in the carbonate samples, B content increases (up to 91 ppm).

Estimates of %NCW bathing deep North Atlantic (IODP Site 306-U1313) over the past ~3.3 Ma

The circulation and internal structure of the oceans exert a strong influence on Earth's climate because they control latitudinal heat transport and the segregation of carbon between the atmosphere and the abyss (Sigman et al., 2010, doi:10.1038/nature09149). Circulation change, particularly in the Atlantic Ocean, is widely suggested (Bartoli et al., 2005, doi:10.1016/j.epsl.2005.06.020; Haug and Tiedemann, 1998, doi:10.1038/31447; Woodard et al., 2014, doi:10.1126/science.1255586; McKay et al., 2012, doi:10.1073/pnas.1112248109) to have been instrumental in the intensification of Northern Hemisphere glaciation when large ice sheets first developed on North America and Eurasia during the late Pliocene, approximately 2.7 million years ago (Bailey et al., 2013, doi:10.1016/j.quascirev.2013.06.004). Yet the mechanistic link and cause/effect relationship between ocean circulation and glaciation are debated. Here we present new records of North Atlantic Ocean structure using the carbon and neodymium isotopic composition of marine sediments recording deep water for both the Last Glacial to Holocene (35-5 thousand years ago) and the late Pliocene to earliest Pleistocene (3.3-2.4 million years ago). Our data show no secular change. Instead we document major southern-sourced water incursions into the deep North Atlantic during prominent glacials from 2.7 million years ago. Our results suggest that Atlantic circulation acts as a positive feedback rather than as an underlying cause of late Pliocene Northern Hemisphere glaciation. We propose that, once surface Southern Ocean stratification (Sigman, et al., 2004, doi:10.1038/nature02357) and/or extensive sea-ice cover (McKay et al., 2012, doi:10.1073/pnas.1112248109) was established, cold-stage expansions of southern-sourced water such as those documented here enhanced carbon dioxide storage in the deep ocean, helping to increase the amplitude of glacial cycles.

(Table 1) Results from XRD analysis as well as sediment type and selected results from ring shear experiments

The location of the seaward tip of a subduction thrust controls material transfer at convergent plate margins, and hence global mass balances. At approximately half of those margins, the material of the subducting plate is completely underthrust so that no accretion or even subduction erosion takes place. Along the remaining margins, material is scraped off the subducting plate and added to the upper plate by frontal accretion. We here examine the physical properties of subducting sediments off Costa Rica and Nankai, type examples for an erosional and an accretionary margin, to investigate which parameters control the level where the frontal thrust cuts into the incoming sediment pile. A series of rotary-shear experiments to measure the frictional strength of the various lithologies entering the two subduction zones were carried out. Results include the following findings: (1) At Costa Rica, clay-rich strata at the top of the incoming succession have the lowest strength (µres = 0.19) while underlying calcareous ooze, chalk and diatomite are strong (up to µres = 0.43; µpeak = 0.56). Hence the entire sediment package is underthrust. (2) Off Japan, clay-rich deposits within the lower Shikoku Basin inventory are weakest (µres = 0.13-0.19) and favour the frontal proto-thrust to migrate into one particular horizon between sandy, competent turbidites below and ash-bearing mud above. (3) Taking in situ data and earlier geotechnical testing into account, it is suggested that mineralogical composition rather than pore-pressure defines the position of the frontal thrust, which locates in the weakest, clay mineral-rich (up to 85 wt.%) materials. (4) Smectite, the dominant clay mineral phase at either margin, shows rate strengthening and stable sliding in the frontal 50 km of the subduction thrust (0.0001-0.1 mm/s, 0.5-25 MPa effective normal stress). (5) Progressive illitization of smectite cannot explain seismogenesis, because illite-rich samples also show velocity strengthening at the conditions tested.

Whistler's pastels and other modern profiles,

Reprinted in part from Art and progress and the International studio.