Multi-proxy analyses of sediment cores from the Pakistan continental margin

Late Holocene laminated sediments from a core transect centred in the oxygen minimum zone (OMZ) impinging at the continental slope off Pakistan indicate stable oxygen minimum conditions for the past 7000 calendar years. High SW-monsoon-controlled biological productivity and enhanced organic matter preservation during this period is reflected in high contents of total organic carbon (TOC) and redox-sensitive elements (Ni, V), as well as by a low-diversity, high-abundance benthic foraminiferal Buliminacea association and high abundance of the planktonic species Globigerina bulloides indicative of upwelling conditions. Surface-water productivity was strongest during SW monsoon maxima. Stable OMZ conditions (reflected by laminated sediments) were found also during warm interstadial events (Preboreal, Bølling-Allerød, and Dansgaard-Oeschger events), as well as during peak glacial times (17-22.5 ka, all ages in calendar years). Sediment mass accumulation rates were at a maximum during the Preboreal and Younger Dryas periods due to strong riverine input and mobilisation of fine-grained sediment coinciding with rapid deglacial sea-level rise, whereas eolian input generally decreased from glacial to interglacial times. In contrast, the occurrence of bioturbated intervals from 7 to 10.5 ka (early Holocene), in the Younger Dryas (11.7-13 ka), from 15 to 17 ka (Heinrich event 1) and from 22.5 to 25 ka (Heinrich event 2) suggests completely different conditions of oxygen-rich bottom waters, extremely low mass and organic carbon accumulation rates, a high-diversity benthic fauna, all indicating lowered surface-water productivity. During these intervals the OMZ was very poorly developed or absent and a sharp fall of the aragonite compensation depth favoured the preservation of pteropods. The abundance of lithogenic proxies suggests aridity and wind transport by northwesterly or northeasterly winds during these periods coinciding with the North Atlantic Heinrich events and dust peaks in the Tibetan Loess records. The correlation of the monsoon-driven OMZ variability in the Arabian Sea with the rapid climatic fluctuations in the high northern latitudes suggests a close coupling between the climates of the high and low latitudes at a global scale.

Corg, CaCO3, bulk densities, accumulation rates and ages of ODP Leg 167 sites and three piston cores, California margin

Sediments from five Leg 167 drill sites and three piston cores were analyzed for Corg and CaCO3. Oxygen isotope stratigraphy on benthic foraminifers was used to assign age models to these sedimentary records. We find that the northern and central California margin is characterized by k.y.-scale events that can be found in both the CaCO3 and Corg time series. We show that the CaCO3 events are caused by changes in CaCO3 production by plankton, not by dissolution. We also show that these CaCO3 events occur in marine isotope Stages (MIS) 2, 3, and 4 during Dansgaard/Oeschger interstadials. They occur most strongly, however, on the MIS 5/4 glaciation and MIS 2/1 deglaciation. We believe that the link between the northeastern Pacific Ocean and North Atlantic is primarily transmitted by the atmosphere, not the ocean. Highest CaCO3 production and burial occurs when the surface ocean is somewhat cooler than the modern ocean, and the surface mixed layer is somewhat more stable.

Deep drilling of glaciers: Russian projects in the Arctic (1975-1995)

The data collection "Deep Drilling of Glaciers: Soviet-Russian projects in Arctic, 1975-1995" was collected by the following basic considerations: - compilation of deep (>100 m) drilling projects on Arctic glaciers, using data of (a) publications; (b) archives of IGRAN; (c) personal communication of project participants; - documentation of parameters, references. Accuracy of data and techniques applied to determine different parameters are not evaluated. The accuracy of some geochemical parameters (up to 1984 and heavy metalls) is uncertain. Most reconstructions of ice core age and of annual layer thickness are discussed; - digitizing of published diagrams (in case, when original numerical data were lost) and subsequent data conversion to equal range series and adjustment to the common units. Therefore, the equal-range series were calculated from original data or converted from digitized chart values as indicated in the metadata. For the methodological purpose, the equal-range series obtained from original and reconstructed data were compared repeatedly; the systematic difference was less then 5-7%. Special attention should be given to the fact, that the data for individual ice core parameters varies, because some parameters were originally measured or registered. Parameters were converted in equal-range series using 2 m steps; - two or more parameter values were determined, then the mean-weighted (i.e. accounting the sample length) value is assigned to the entire interval; - one parameter value was determined, measured or registered independently from the parameter values in depth intervals which over- and underlie it, then the value is assigned to the entire interval; - one parameter value was determined, measured or registered for two adjoining depth intervals, then the specific value is assigned to the depth interval, which represents >75% of sample length ; if each of adjoining depth intervals represents <75% of sample length, then the correspondent parameter value is assigned to both intervals of depth. This collection of ice core data (version 2000) was made available through the EU funded QUEEN project by S.M. Arkhipov, Moscow.

Campanian-Maestrichtian planktonic foraminifera of the southern South Atlantic

Campanian-Maestrichtian planktonic foraminifers were examined from Sites 698 (2128 m water depth) and 700 (3611 m water depth) on the Northeast Georgia Rise (southern South Atlantic, 51°S). Site 698 penetrated 72.5 m of Campanian-Maestrichtian chalk and limestone with only 18.2% recovery, whereas Site 700 recovered 66.8% of a 152.7-m section of Coniacian-Maestrichtian limestone. Preservation of planktonic foraminifers from both sites is moderate in Maestrichtian samples, but worsens with increasing depth in the Campanian. The Northeast Georgia Rise planktonic foraminifers are typical of Late Cretaceous Austral Province faunas described from other southern high-latitude sites; species diversity is low and the assemblages are dominated by species of Heterohelix, Globigerinelloides, Hedbergella, and Archaeoglobigerina. Five species, including Globigerinelloides impensus Sliter, Archaeoglobigerina australis Huber, Archaeoglobigerina mateola Huber, Hedbergella sliteri Huber, and Rugotruncana circumnodifer (Finlay), are considered to be endemic to the Austral Province. Formation of a cool temperate water mass in the circum-Antarctic region, resulting from the final breakup of the Gondwana continents, may have led to increased provincialism of the Austral Province planktonic foraminifers during Campanian-Maestrichtian time. Magnetobiostratigraphic correlation of eight planktonic foraminifer datum events at Hole 700B with ages determined for datums at ODP Leg 113 Holes 689B and 690C (Maud Rise, 65°S) demonstrates regional synchroneity of first and last occurrences within the Austral Province. As was observed at the Maud Rise, several keeled and nonkeeled species previously thought to have been restricted to warmer low-latitude regions first occur later at the Northeast Georgia Rise than at the low-latitude sites. The causes for high-latitude diachroneity among these immigrant species are not clear; neither oxygen and carbon isotope data from the Maud Rise sites nor calcareous nannoplankton distributions for the southern South Atlantic region show conspicuous changes that correlate to the delayed first occurrences.

Calcareous nannofossils of ODP Hole 123-765C and DSDP Hole 27-261

Sediments from the Argo Abyssal Plain (AAP), northwest of Australia, are the oldest known from the Indian Ocean and were recovered from ODP Site 765 and DSDP Site 261. New biostratigraphic and sedimentologic data from these sites, as well as reinterpretations of earlier findings, indicate that basal sediments at both localities are of Late Jurassic age and delineate a history of starved sedimentation punctuated by periodic influx of calcareous pelagic turbidites. Biostratigraphy and correlation of Upper Jurassic-Lower Cretaceous sediments is based largely on calcareous nannofossils. Both sites yielded variably preserved nannofossil successions ranging from Tithonian to Hauterivian at Site 765 and Kimmeridgian to Hauterivian at Site 261. The nannofloras are comparable to those present in the European and Atlantic Boreal and Tethyan areas, but display important differences that reflect biogeographic differentiation. The Argo region is thought to have occupied a position at the southern limit of the Tethyan nannofloral realm, thus yielding both Tethyan and Austral biogeographic features. Sedimentary successions at the two sites are grossly similar, and differences largely reflect Site 765's greater proximity to the continental margin. Jurassic sediments were deposited at rates of about 2 m/m.y. near the carbonate compensation depth (CCD) and contain winnowed concentrations of inoceramid prisms and nannofossils, redeposited layers rich in calcispheres and calcisphere debris, manganese nodules, and volcanic detritus. Lower Cretaceous and all younger sediments accumulated below the CCD at rates that were highest (about 20 m/m.y.) during mid-Cretaceous and Neogene time. Background sediment in this interval is noncalcareous claystone; turbidites dominate the sequence and are thicker and coarser grained at Site 765. AAP turbidites consist mostly of calcareous and siliceous biogenic components and volcanogenic smectite clay; they were derived from relatively deep parts of the continental margin that lay below the photic zone, but above the CCD. The Jurassic-Lower Cretaceous section is about the same thickness across the AAP; turbidites in this interval appear to have had multiple sources along the Australian margin. The Upper Cretaceous-Cenozoic section, however, is three times thicker at Site 765 than at Site 261; turbidites in this interval were derived predominantly from the south. Patterns of sedimentation across the AAP have been influenced by shifts in sea level, the CCD, and configuration of the continental margin. Major pulses of calcareous turbidite deposition occurred during Valanginian, Aptian, and Neogene time-all periods of eustatic lowstands and depressed CCD levels. Sediment redeposited on the AAP has come largely from the Australian outer shelf, continental slope, or rise, rather than the continent itself. Most terrigenous detritus was trapped in epicontinental basins that have flanked northwestern Australia since the early Mesozoic.

Vocational and occupational counsseling: a strategy of preventive intervention directed to Young men and women from the interior of the province of Buenos Aires

This work belongs to one of the activities that are carried out in the Vocational and Occupational Guidance Center (V.O.G.C.) of the Faculty of Humanities and Educational Sciences at the L.P.N.U. In the year 1994 the Vocational/Occupational Guidance Programme for Municipalities was created, destined for work with adolescents who are attending their last year at secondary schools in the interior of the Province of Buenos Aires . The Programme aims at fostering the development of spaces for reflection related to the educational/working projects of the adolescents who are close to entering university. The proposal is based on the methodology of work groups, in the journeys preoccupations are sheared, the worries and fears experienced by the students are shared with their hosts, possibilities are used as ground for construction, dealing both with aspects of their current situation and their future possibilities. From the analysis of the group productions collected throughout these years, we have developed a student's profile that - although it resembles the one obtained from local adolescents- adds new questions and points of view, thus increasing the complexity of the balance of forces related to the question of having to make a choice.

Stable oxygen isotope record of Globigerinoides ruber of ODP Site 133-820 off the Great Barriere Reef

Oxygen-isotope ratio measurements are presented for the planktonic species Globigerinoides ruber collected from shallow-water, upper-slope sediments from Holes 820A and 820B in 280 m of water, on the seaward edge of the Great Barrier Reef. Correlation of the Site 820 isotope curve with deep-sea reference curves of the Pacific Ocean (Core V28-238, Hole 677A, Hole 607A) permits the definition of isotope stages 1 to 19 in the top 145 m of Holes 820A and 820B. However, paleontological data indicate that stages 4 and 7 might be missing and that two hiatuses occur at a depth of 8.05 to 12.1 and 34.55 to 35.8 mbsf. Using deep-sea Hole 677A as a reference for ice-volume variations, we determine the difference in isotopic signature between it and Site 820. We propose that this difference is a regional signal representing a progressive 4°C increase in surface-water temperature at Site 820. The proposed temperature change was initiated at about 400 k.y. and corresponds to a change from high-to-low frequency variations in Pleistocene isotope signals. We postulate that these changes may have catalyzed the growth of the Great Barrier Reef. The shift also coincides with changes in seismic character and some physical and chemical sediment characteristics.

Analysis of an ancient global warming event, the Paleocene-Eocene thermal maximum, under examination from ODP Holes 113-689B and 113-690B

Spatiotemporal patterns of carbonate dissolution provide a critical constraint on carbon input during an ancient (~55.5 Ma) global warming event known as the Paleocene-Eocene thermal maximum (PETM), yet the magnitude of lysocline shoaling in the Southern Ocean is poorly constrained due to limited spatial coverage in the circum-Antarctic region. This shortcoming is partially addressed by comparing patterns of carbonate sedimentation at the Site 690 PETM reference section to those herein reconstructed for nearby Site 689. Biochemostratigraphic correlation of the two records reveals that the first ~36 ka of the carbon isotope excursion (CIE) signaling PETM conditions is captured by the Site 689 section, while the remainder of the CIE interval and nearly all of the CIE recovery are missing due to a coring gap. A relatively expanded stratigraphy and higher carbonate content at mid-bathyal Site 689 indicate that dissolution was less severe than at Site 690. Thus, the bathymetric transect delimited by these two PETM records indicates that the lysocline shoaled above Site 689 (~1,100 m) while the calcite compensation depth remained below Site 690 (~1,900 m) in the Weddell Sea region. The ensuing recovery of carbonate sedimentation conforms to a bathymetric trend best explained by gradual lysocline deepening as negative feedback mechanisms neutralized ocean acidification. Further, biochemostratigraphic evidence indicates the tail end of the CIE recovery interval at both sites has been truncated by a hiatus most likely related to vigorous production and advection of intermediate waters.

Characteristic directions and polarity ratings and polarity chron assignments of ODP Leg 171B sites

The full suite of magnetic polarity chrons from Subchron M''-2r'' (early Albian) through Chron C13r (latest Eocene) were resolved at one or more Ocean Drilling Program sites on the Blake Nose salient of the Florida continental margin. These sediments preserve diverse assemblages of calcareous and siliceous microfossils; therefore, the composite suite provides a reference section for high-resolution correlation of biostratigraphic datums to magnetic polarity chrons of the Late Cretaceous and Paleogene. Relative condensation or absence of polarity zones at different sites along the transect enhance the recognition and dating of depositional sequences and unconformities within the margin succession. A stable paleolatitude of ~25°N was maintained from the late Aptian through Eocene.

Late Campanian and Maastrichtian benthic foraminifera of El Kef, Tunesia

Late Campanian through Maastrichtian sea-level changes are examined based on lithology, macrofossils and benthic foraminifera at the Elles and El Kef sections in Tunisia. Six major sea-level regressions are identified during the late Campanian (74.4-74.2 Ma, 74.0-72.5 Ma), the Campanian-Maastrichtian transition (72.2-70.3 Ma), early Maastrichtian (69.6-69.3 Ma, 68.9-68.3 Ma), and late Maastrichtian (~65.5 Ma). Correlation of the Maastrichtian sea-level regressions with the oxygen isotope record of DSDP Site 525 in the middle latitude South Atlantic reveals that they coincide with episodes of high latitude cooling and appear to be of eustatic origin.