(Table 2) Ice rafted debris abundance and accumulation rate, sedimentation rate and dry bulk density of bottom sediments from the Sea of Okhotsk

Oxygen isotope records, radiocarbon AMS data, carbonate and opal stratigraphy, sediment magnetic susceptibility, tephrachronology, and paleontological results were used to obtain detailed sediment stratigraphy and an age model for the studied cores. For studying sea-ice sedimentation an analysis of lithogenic grain number in >0.15 mm grain size fraction of bottom sediments was carried out. For quantitative estimation of intensity ice-rafting debris sedimentation number of IRD particles per sq cm per ka was calculated. Obtained results allowed to plot IRD AR distribution for the first oxygen isotope stage (0-12.5 14C ka, 14C) and for the second stage (12.5-24 14C ka). The first stage was subdivided into the latest deglaciation and the beginning of Holocene (6-12.5 14C ka) (transitive period), when the sea level was changing significantly, and the second part of Holocene (0-6 14C ka), when climate conditions and the sea level were similar to modern estimates. Data clearly show strong increase in ice formation in the glacial Sea of Okhotsk and its extent in the middle part of the sea. Average annual duration of ice coverage during glaciation was longer than that for interglaciation. However the sea ice cover was not continuous all the year round and disappeared in summer time except the far northwestern part of the sea.

Winter sea surface temperature reconstruction from planktic foraminiferal transfer functions in the northeastern Arabian Sea over the last two millennia

The Indian monsoon system is an important climate feature of the northern Indian Ocean. Small variations of the wind and precipitation patterns have fundamental influence on the societal, agricultural, and economic development of India and its neighboring countries. To understand current trends, sensitivity to forcing, or natural variation, records beyond the instrumental period are needed. However, high-resolution archives of past winter monsoon variability are scarce. One potential archive of such records are marine sediments deposited on the continental slope in the NE Arabian Sea, an area where present-day conditions are dominated by the winter monsoon. In this region, winter monsoon conditions lead to distinctive changes in surface water properties, affecting marine plankton communities that are deposited in the sediment. Using planktic foraminifera as a sensitive and well-preserved plankton group, we first characterize the response of their species distribution on environmental gradients from a dataset of surface sediment samples in the tropical and sub-tropical Indian Ocean. Transfer functions for quantitative paleoenvironmental reconstructions were applied to a decadal-scale record of assemblage counts from the Pakistan Margin spanning the last 2000?years. The reconstructed temperature record reveals an intensification of winter monsoon intensity near the year 100 CE. Prior to this transition, winter temperatures were >1.5°C warmer than today. Conditions similar to the present seem to have established after 450 CE, interrupted by a singular event near 950 CE with warmer temperatures and accordingly weak winter monsoon. Frequency analysis revealed significant 75-, 40-, and 37-year cycles, which are known from decadal- to centennial-scale resolution records of Indian summer monsoon variability and interpreted as solar irradiance forcing. Our first independent record of Indian winter monsoon activity confirms that winter and summer monsoons were modulated on the same frequency bands and thus indicates that both monsoon systems are likely controlled by the same driving force.

Sea surface temperature and export productivity reconstructions of sediments off the western Iberian margin

Present day hydrographic conditions along the western Iberian margin are characterized by seasonal upwelling with filaments that can penetrate more than 200 km into the open ocean and constitute areas of cold and highly productive waters. In order to investigate spatial and temporal gradients in temperature and productivity conditions during the last 150 ky, high-resolution proxy records were generated in 3 cores (SU92-03, MD95-2040, MD95-2042), located along the Iberian coast between 43°12'N and 37°48'N and forming a N-S profile. In all cores, planktonic foraminifera census counts are used to reconstruct summer sea surface temperature (SSTsu) and export productivity (Pexpsu) using the modern analog technique SIMMAX 28. SSTsu and Pexpsu values similar to the present are observed throughout the Holocene and MIS 5e periods for each site, respectively, indicating fairly stable conditions equivalent to the modern ones. On glacial/interglacial timescales, SSTsu increases by 2-3 °C from the northern to southernmost site. Pexpsu, on the other hand, shows a decrease of 30-40 gC/m**2/yr from North to South at present time and during interglacial periods, and no significant variation (90-100 gC/m**2/yr) during glacial periods. The northernmost core SU92-03 reveals the coldest conditions with records more similar to MD95-2040 than to MD95-2042, the later of which is, as at present, more affected by subtropical waters. Core SU92-03 shows higher interglacial productivity similar to open ocean mid- to high latitude sites, while the other two cores monitor higher glacial productivity conform with other upwelling sites off NW Africa. A boundary between differences in glacial/interglacial productivity appears to be present in our study between 43°12'N and 40°35'N. Especially north of 40°N, coldest SSTsu and lowest Pexpsu are found during Heinrich events (H)1-H8 and H10-H11. In contrast, lowest Pexpsu do not coincide with these events at site MD95-2042, but appear to be related to the presence of relatively warm and nutrient-poor subtropical Eastern North Atlantic Central Water advected with the Azores Current.

Biostratigraphy and average linear sedimentation rate and accumulation rate of ODP Site 159-959 (Table 1)

Reconstructing the long-term evolution of organic sedimentation in the eastern Equatorial Atlantic (ODP Leg 159) provides information about the history of the climate/ocean system, sediment accumulation, and deposition of hydrocarbon-prone rocks. The recovery of a continuous, 1200 m long sequence at ODP Site 959 covering sediments from Albian (?) to the present day (about 120 Ma) makes this position a key location to study these aspects in a tropical oceanic setting. New high resolution carbon and pyrolysis records identify three main periods of enhanced organic carbon accumulation in the eastern tropical Atlantic, i.e. the late Cretaceous, the Eocene-Oligocene, and the Pliocene-Pleistocene. Formation of Upper Cretaceous black shales off West Africa was closely related to the tectonosedimentary evolution of the semi-isolated Deep Ivorian Basin north of the Côte d'Ivoire-Ghana Transform Margin. Their deposition was confined to certain intervals of the last two Cretaceous anoxic events, the early Turonian OAE2 and the Coniacian-Santonian OAE3. Organic geochemical characteristics of laminated Coniacian-Santonian shales reveal peak organic carbon concentrations of up to 17% and kerogen type I/II organic matter, which qualify them as excellent hydrocarbon source rocks, similar to those reported from other marginal and deep sea basins. A middle to late Eocene high productivity period occurred off equatorial West Africa. Porcellanites deposited during that interval show enhanced total organic carbon (TOC) accumulation and a good hydrocarbon potential associated with oil-prone kerogen. Deposition of these TOC-rich beds was likely related to a reversal in the deep-water circulation in the adjacent Sierra Leone Basin. Accordingly, outflow of old deep waters of Southern Ocean origin from the Sierra Leone Basin into the northern Gulf of Guinea favored upwelling of nutrient-enriched waters and simultaneously enhanced the preservation potential of sedimentary organic matter along the West African continental margin. A pronounced cyclicity in the carbon record of Oligocene-lower Miocene diatomite-chalk interbeds indicates orbital forcing of paleoceanographic conditions in the eastern Equatorial Atlantic since the Oligocene-Miocene transition. A similar control may date back to the early Oligocene but has to be confirmed by further studies. Latest Miocene-early Pliocene organic carbon deposition was closely linked to the evolution of the African trade winds, continental upwelling in the eastern Equatorial Atlantic, ocean chemistry and eustatic sea level fluctuations. Reduction in carbonate carbon preservation associated with enhanced carbon dissolution is recorded in the uppermost Miocene (5.82-5.2 Ma) section and suggests that the latest Miocene carbon record of Site 959 documents the influence of corrosive deep waters which formed in response to the Messinian Salinity Crisis. Furthermore, sea level-related displacement of higher productive areas towards the West African shelf edge is indicated at 5.65, 5.6, 5.55, 5.2, 4.8 Ma. In view of humid conditions in tropical Africa and a strong West African monsoonal system around the Miocene-Pliocene transition, the onset of pronounced TOC cycles at about 5.6 Ma marks the first establishment of upwelling cycles in the northern Gulf of Guinea. An amplification in organic carbon deposition at 3.3 Ma and 2.45 Ma links organic sedimentation in the tropical eastern Equatorial Atlantic to the main steps of northern hemisphere glaciation and testifies to the late Pliocene transition from humid to arid conditions in central and western African climate. Aridification of central Africa around 2.8 Ma is not clearly recorded at Site 959. However, decreased and highly fluctuating carbonate carbon concentrations are observed from 2.85 Ma on that may relate to enhanced terrigenous (eolian) dilution from Africa.

Estudo comparativo do acúmulo de massa seca e macronutrientes por plantas de Zea mays e Ipomoea hederifolia

Two experiments were carried out under greenhouse conditions to study the accumulation and distribution of dry mass and macronutrients in maize and Ipomoea hederifolia. Plants of both species had grown, separately, in pots with sand substrate and irrigation with nutrient solution. Treatments were represented by the times of evaluation, realized in intervals of 14 days, starting at 21 days after emergence (DAE). A maize plant showed slight growth up to 30 DAE, when dry mass allocation was higher in roots and leaves (80%); while an I. hederifolia plant, up to 50 DAE, when the allocation of dry mass was higher in offshoots and leaves (79). Dry mass accumulation was almost five times greater in maize (134 g per plant) than in I. hederifolia (29 g per plant). The average values of N and K contents were greater in I. hederifolia. Maximum accumulations of macronutrients by maize were 1,431; 474; 1,832; 594; 340, and 143 mg per plant, while by I. hederifolia, 727; 52; 810; 350; 148, and 65 mg per plant, for N, P, K, Ca, Mg, and S, respectively. Mean accumulation rate of dry mass and macronutrients by maize plants was crescent up to 87 DAE, reaching the maximum value at 103 DAE; while being crescent up to 121 DAE by I. hederifolia plants, reaching the maximum value at 138 DAE. Thus, beyond the interference on harvesting process, a population of I. hederifolia also can compete with maize crop for nutrients.

Produção de forragem e composição estrutural de pastos de Brachiaria brizantha cv. Xaraés manejados em diferentes alturas de pastejo

The objective of this study was to analyze the production of dry mass, forage accumulation rate and the structural composition of Brachiaria brizantha cv. Xaraes pastures, managed under different grazing heights in continuous stocking. The experimental area was 12 hectares, divided in paddocks of one hectare each. The treatments were 15, 30, 45 and 60 cm of defoliation heights. Nellore steers were used to reach the desired heights. Every 28 days four cut samples and eight visual samples were collected for comparative performance in the experimental plots. Two grazing exclusion cages were used per treatment to estimate accumulation rates kg.ha(-1) DM. The cut material was taken to the laboratory for separation of the botanical components (green leaf, stem and senescent material), weighing and determination of dry matter. The experimental design was the completely randomized with three replicates. There were treatments effects at all seasons for the production of total mass, except in the spring. In summer and spring seasons it was observed the highest values for leaf blades (1.100 kg DM.ha(-1)). In the winter, the highest values of senescent material was observed, as expected. The average accumulation showed no significant difference among the treatments, except for stem and total mass in the summer and stem in the fall. The tillers were heavier and higher values for number of green leaves per tiller occurred in the fall, but for senescent leaves per tiller ocurred in the winter. Swards grazed at heights between 45 and 60 cm of defoliation, had good production of forage mass and leaf constituent.

Planktonic foraminifera of IODP Site 306-U1314

Surface water conditions at the Integrated Ocean Drilling Program (IODP) Site U1314 (Southern Gardar Drift, 56° 21.8' N, 27° 53.3' W, 2820 m depth) were inferred using planktic foraminifer assemblages between Marine Isotope Stage (MIS) 19 and 11 (ca. 800-400 ka). Factor analysis of the planktic foraminifer assemblages suggests that the assemblage was controlled by three factors. The first factor (which explained 49% of the variance) is dominated by transitional and subpolar species and points to warm and salty surface water conditions (Atlantic water). The second factor (37%) is dominated by Neogloboquadrina pachyderma sin and has been associated with the presence of cold and low saline surface waters (Arctic water). Finally, the third factor (9%), linked to a significant presence of Turborotalita quinqueloba, reflects the closeness of the Arctic front (the boundary between Atlantic and Arctic water). The position of the Arctic and Polar fronts has been estimated across the glacial-interglacial cycles studied according to planktic foraminifer abundances from Site U1314 (and their factor analysis) combined with a synthesis of planktic foraminifer and diatom data from other North Atlantic sites. Regarding at the migrations of the Arctic front and the surface water masses distribution across each climatic cycle we determined five phases of development. Furthermore, deep ocean circulation changes observed in glacial-interglacial cycles have been associated with each phase. The high abundance of transitional-subpolar foraminifers (above 65% at Site U1314) during the early interglacial phase indicated that the Arctic front position and surface water masses distribution were similar to present conditions. During the late interglacial phase, N. pachyderma sin and T. quinqueloba slightly increased indicating that winter sea ice slightly expanded southwestwards whereas the ice volume remained stable or was still decreasing. N. pachyderma sin increased rapidly (above 65% at Site U1314) at the first phase of glacial periods indicating the expansion of the Arctic waters in the western subpolar North Atlantic. During the second phase of glacial periods the transitional-subpolar assemblage throve again in the central subpolar North Atlantic associated with strong warming events that followed ice-rafting events. The third phase of glacial periods corresponds to full glacial conditions in which N. pachyderma sin dominated the assemblage for the whole subpolar North Atlantic. This division in phases may be applied to the last four climatic cycles.

Benthic foraminiferal accumulation rates of the late Pliocene-Pleistocene in the northern Indian Ocean

During the late Pliocene-middle Pleistocene, 63 species of elongate, bathyal-upper abyssal benthic foraminifera (Extinction Group = Stilostomellidae, Pleurostomellidae, some Nodosariidae) declined in abundance and finally disappeared in the northern Indian Ocean (ODP Sites 722, 758), as part of the global extinction of at least 88 related species at this time. The detailed record of withdrawal of these species differs by depth and geography in the Indian Ocean. In northwest Indian Ocean Site 722 (2045 m), the Extinction Group of 54 species comprised 2-15% of the benthic foraminiferal fauna in the earliest Pleistocene, but declined dramatically during the onset of the mid-Pleistocene Transition (MPT) at 1.2-1.1 Ma, with all but three species disappearing by the end of the MPT (~0.6 Ma). In northeast Indian Ocean Site 758 (2925 m), the Extinction Group of 44 species comprised 1-5% of the benthic foraminiferal fauna at ~3.3-2.6 Ma, but declined in abundance and diversity in three steps, at ~2.5, 1.7, and 1.2 Ma, with all but one species disappearing by the end of the MPT. At both sites there are strong positive correlations between the accumulation rate of the Extinction Group and proxies indicating low-oxygen conditions with a high organic carbon input. In both sites, there was a pulsed decline in Extinction Group abundance and species richness, especially in glacial periods, with some partial recoveries in interglacials. We infer that the glacial declines at the deeper Site 758 were a result of increased production of colder, well-ventilated Antarctic Bottom Water (AABW), particularly in the late Pliocene and during the MPT. The Extinction Group at shallower water depths (Site 722) were not impacted by the deeper water mass changes until the onset of the MPT, when cold, well-ventilated Glacial North Atlantic Intermediate Water (GNAIW) production increased and may have spread into the Indian Ocean. Increased chemical ventilation at various water depths since late Pliocene, particularly in glacial periods, possibly in association with decreased or more fluctuating organic carbon flux, might be responsible for the pulsed global decline and extinction of this rather specialised group of benthic foraminifera.

Mass accumulation rates, age, sedimentation rate and bulk density at the East Pacific Rise

The rate at which hydrothermal precipitates accumulate, as measured by the accumulation rate of manganese, can be used to identify periods of anomalous hydrothermal activity in the past. From a preliminary study of Sites 597 and 598, four periods prior to 6 Ma of anomalously high hydrothermal activity have been identified: 8.5 to 10.5 Ma, 12 to 16 Ma, 17 to 18 Ma, and 23-to-27 Ma. The 18-Ma anomaly is the largest and is associated with the jump in spreading from the fossil Mendoza Ridge to the East Pacific Rise, whereas the 23-to-27-Ma anomaly is correlated with the birth of the Galapagos Spreading Center and resultant ridge reorganization. The 12-to-16-Ma and 8.5-to-10.5-Ma anomalies are correlated with periods of anomalously high volcanism around the rim of the Pacific Basin and may be related to other periods of ridge reorganization along the East Pacific Rise. There is no apparent correlation between periods of fast spreading at 19°S and periods of high hydrothermal activity. We thus suggest that periods when hydrothermal activity and crustal alteration at mid-ocean ridges are the most pronounced may be periods of large-scale ridge reorganization.

Geochemistry and foraminiferal stable isotoe record of sediment core SCS90-36

Changes in the Southeast Asia monsoon winds and surface circulation patterns since the last glaciation are inferred using multiple paleoceanographic indicators including planktic foraminifer faunal abundances, fauna and alkenones sea-surface temperature (SST) estimates, oxygen and carbon isotopes of planktic and benthic foraminifers, and sedimentary fluxes of carbonates and organic carbon obtained from deep-sea core SCS90-36 from the South China Sea (SCS) (17°59.70'N, 111°29.64'E at water depth 2050 m). All these paleoceanographic evidences indicate marked changes in the SCS ocean system over the last glacial toward the Holocene. Planktic foraminiferal faunal SST estimates show stable warm-season SST of 28.6°C, close to the modern value, throughout the glacial-interglacial cycle. In contrast, cold-season SST increases gradually from 23.6°C in the last glacial to a mean value of 26.4°C in the Holocene with a fluctuation of about 3°C during 13-16 ka. SST estimates by UK'37 method reveal less variability and are in average 1-3°C lower than the fauna-derived winter-season SST. These patterns reveal that the seasonality of the SST is not only higher by about 3-4°C in the glacial, but also a function of the winter season SST. Sedimentation rates decrease from the last glacial-deglacial stage to the Holocene due to a reduction in supply of terrigenous components, which led to an increase of carbonate contents. Total organic carbon (TOC) contents of primarily marine sources decrease from the last glacial-deglacial to the Holocene. The last deglaciation is also characterized by high surface productivity as indicated by increased ketones abundances and high mass accumulation rates (MAR) of the TOC and carbonates. The gradient of planktic foraminifer ocygen and carbon isotopes of between surface dwellers and deep dwellers increases significantly toward Termination I and Holocene, and is indiscernibly small in the carbon isotope gradient of between 14 and 24 ka, revealing a deep-mixing condition in surface layers prior to 10 ka. The glacial-interglacial fluctuation of the carbon isotope value of a benthic foraminifer is 0.61%. which is significantly larger than a global mean value. The large carbon isotope fluctuation indicates an amplification of marginal-sea effects which is most likely resulted from an increase in surface productivity in the northern SCS during the last glacial-deglacial stage. The multiple proxies consistently indicate that the last glacial-deglacial stage winter monsoon in the Southeast Asia was probably strengthened in the northern SCS, leading to a development of deep-mixing surface layer conditions and a more efficient nutrient cycling which supports more marine organic carbon production.