Geochemistry at DSDP Legs 36 and 71 Holes

For Middle Jurassic to Pleistocene times, clay mineralogical and geochemical data provide information on the evolution of continental and marine paleoenvironments. They are a source of information on marginal instability, on the continental and shallow marine environments related to the development of the Southern Ocean during the Middle and Late Jurassic, and on tectonic relaxation of the continental margins at the end of the Late Jurassic. They also provide evidence for the influences of the South Atlantic opening and the movement of the Falkland Plateau in a reduced marine environment until Aptian-Albian times, and the transition to an open marine environment during Albian time; the influences of the Albian-Turonian and Coniacian-Santonian Andean deformations in an open marine environment; the limited tectonic effects and strong influence of marine currents at the Cretaceous/Tertiary boundary; the influences of the global climatic cooling and inferred bottom water circulation during the late Eocene and Oligocene; the widening of the South Atlantic Ocean during Oligocene time, which was accompanied by an increased influence of the biogenic components on sedimentation; increased carbonate dissolution from late Oligocene to early Miocene, related to the deepening of the ocean; limited mineralogical and important geochemical modifications when the Drake Passage opened in the early Miocene; the influence of the late Miocene development of the Antarctic ice-sheet; the major Antarctic cooling and Patagonian glaciation during Pliocene time; and the change in the Antarctic Bottom Water circulation at the Pliocene/Pleistocene boundary.

Produtividade de vacas mestiças leiteiras em sistema semi-intensivo nos municípios de Irituia e Mãe do rio do nordeste paraense

Verificar a influência de fatores do meio ambiente sobre características de produção e reprodução em grupos genéticos de bovinos leiteiros explorados em algumas fazendas nos municípios de Irituia e Mãe do rio no Nordeste Paraense. Foi utilizada uma média de 454 animais em lactação mestiças de Holandês, Pardo-Suíça e Girolando pertencentes a duas fazendas com sistema de criação semi-intensivo na época menos chuvosa. As médias e desvio-padrão para produção de leite total foram iguais a 1097,36 ± 330,47 Kg, com coeficiente de variação igual a 25,64% sendo que o grupo genético Holandesa, a época de parto menos chuvosa e o ano de 2007 apresentaram maior produção. O período de lactação apresentou efeito linear e crescente sobre a produção de leite total. O período de lactação apresentou média e desvio-padrão iguais a 218,17 ± 43,17 dias, a maior média para o período de lactação foi observada na época mais chuvosa e a média do período de lactação diminuiu no decorrer dos anos 2007 e 2008. A média e desvio padrão de intervalo entre partos encontrado no rebanho foi igual a 398,975 ± 60,85 dias. A época menos chuvosa apresentou uma média de intervalo entre partos menor que época mais chuvosa e a média de intervalo entre partos foi reduzindo a partir de 2006. A média de idade ao primeiro parto encontrado foi de 38,57 ± 5,81 meses. Os coeficientes de determinação foram maiores que 0,85 (R²a > 0,85), sendo que para o grupo genético Holandesa, os ajustes foram melhores em relação aos ajustes dos outros dois grupos genéticos. Para o grupo genético Girolando, o formato da curva de lactação diferiu dos outros dois grupos genéticos dificultando o ajuste pelas funções Gama Incompleta, Linear Hiperbólica e Polinomial Inversa. Os ajustes promovidos pela função polinomial inversa apresentaram ligeiro desvio em relação às outras duas funções. O grupo genético Holandesa apresentou produção ao pico e persistência um pouco mais elevados em relação aos outros grupos genéticos.

Foraminifera and microfossil occurence in Late Jurassic sediments of the North and South Atlantic

Biostratigraphical, taxonomical, and palaeocological results were obtained from Oxfordian to Tithonian foraminifers of the Northern and Southern Atlantic Ocean boreholes of the DSDP Legs 1, 11, 36, 41, 44, 50, and 79. An oversight on the cored Jurassic sections of the DSDP Legs 79 and the corresponding foraminiferal descriptions are given. The reddish brown, clayey and carbonaceous Cat Gap Formation (Oxfordian to Tithonian) of the Northern Atlantic Ocean, rich in radiolarians, yields less or more uniform, in most cases allochthonous foraminiferal faunas of Central European shelf character. No Callovian and Upper Tithonian foraminiferaI zones can be established. The zone of Pseudomarssonella durnortieri covers the Oxfordian/Kimmeridgian, the zone of Neobulimina atlantica the Kimmeridgian/Lower Tithonian interval. Characteristic foraminiferal faunas are missing since the Upper Tithonian to Valanginian for reason of a widely distributed regression which caused hiatuses observed all over the Northern Atlantic Ocean and in parts of Europe. The Upper Jurassic cannot be subdivided into single stages by foraminiferal biostratigraphy alone. The fovaminiferal zones established by Moullad (1984) covering a Callovian-Tithonian interval may be of some local importance in the Tethyan realm: It has too long-ranging foraminiferal species to be used as index marker in the word-wide DSDP boreholes. Some taxonomical confusion is caused because in former publications some foraminiferal species have got different names both in the Jurassic and Cretaceous. The foraminiferal biostratigraphy of drilled sections from DSDP boreholes is restricted by the drilling technique and for palaeo-oceanographical, biological, and geological reasons. Foraminiferal faunas from the DSDP originally described as ,,bathyal, or ,,abyssal,, have to be derived from shallower water. This contrasts the palaeo-water depths of 3000-4000 m which result from sedimentological and palaeo-geographical investigations.

Organic facies variations in the Mesozoic South Atlantic DSDP Holes

Visual kerogen and total organic carbon determinations indicate that there are two periods of organic enrichment events in the Mesozoic sediments of the South Atlantic. The first period, from the Late Jurassic through the late Aptian, is recorded in sediments from the Falkland Plateau, the Cape Basin, and the Angola Basin. Apparently, salinity stratification in the restricted basin, coupled with rising sea level, led to bottom water anoxia and organic enrichment. The second event, from the late Albian to the Santonian period, is recorded in sediments from the Angola Basin and the Sao Paulo Plateau. It appears to have been caused by development of an anoxic oxygen minimum zone at midwater depths. Organic matter sedimentation in the Mesozoic South Atlantic is controlled by geologic, climatic, eustatic, and Oceanographic factors.

Strontium-isotope stratigraphy and oxygen- and carbon-isotope record of Middle Jurassic to Early Cretaceous belemnites in the South Atlantic

87Sr/86Sr data of belemnites are presented from a Middle Jurassic-Early Cretaceous succession from the Falkland Plateau (Deep Sea Drilling Project Sites 511 and 330) that was deposited in a periodically anoxic, semi-enclosed shallow water basin. Diagenetically screened strontium-isotope values of 0.706789 rise to 0.707044 before increasing sharply to 0.707428 in the uppermost part of the sampled succession. Comparison with published strontium calibration curves suggests that the oldest samples were Callovian to Oxfordian in age, whilst the remainder of the Jurassic part of the succession consisted of Kimmeridgian and Early Tithonian age sediments. The nannofossil, dinoflagellate and molluscan assemblages provide comparable age determinations. The strontium-isotope analysis of the youngest belemnites points to a Hauterivian-Barremian age, whilst age interpretations based upon the fauna provide a wide age range from the Barremian to early Albian. Strontium-isotope stratigraphy of this succession hence offers increased age resolution providing data regarding the timing of episodes of bottom water anoxia which have been recorded throughout the South Atlantic Basin. Well-preserved belemnite specimens display an oxygen-isotope range between +0.08 and -2.22? (PDB, Peedee belemnite international standard) and a carbon-isotope range from +2.35 to -1.33? (PDB). Delta13C values become increasingly negative through the Late Jurassic-Early Cretaceous and in concert with the 87Sr/86Sr data reveal a trend that could be accounted for by increasing levels of weathering and erosion. The oxygen-isotope data if interpreted in terms of palaeotemperature are consistent with warm palaeotemperatures in the Kimmeridgian and slightly cooler temperatures for the Tithonian and Early Cretaceous parts of the succession. The proposed relative Kimmeridgian warmth (based upon strontium-isotope age assignments) is thus in good agreement with other published palaeotemperature records.

Paleotemperature reconstructions from high Late Jurassic paleolatitudes

Oxygen and carbon isotopes have been determined from Late Jurassic (Oxfordian-Tithonian) belemnites and inoceramid bivalves from two Deep Sea Drilling Project (DSDP) sites located on the Falkland Plateau. Mean belemnite delta18O values, derived from well preserved skeletal material, were -1.29? from DSDP site 330 and -1.45? from DSDP site 511. Assuming a seawater SMOW value of -1.0?, mean palaeotemperatures calculated from the oxygen isotopic composition are 17.2°C and 17.9°C, respectively. The inoceramid bivalves yielded much lighter delta18O values (mean -3.58?). Petrographic and geochemical evidence points to the inoceramid bivalves being altered by diagenesis which accordingly accounts for the observed differences in isotopic values. "Vital effects" or the importation of belemnites or inocerarnids from another area, are considered not to account for the observed isotopic trends. The palaeotemperatures interpreted from the belemnites are significantly warmer than other recent estimates of Late Jurassic temperature (from oxygen isotope studies and climate model predictions) from similar southern palaeolatitudes. We suspect our apparent warmer temperatures are because of a combination of increased freshwater runoff depleting surface waters with respect to delta18O and related to the semi-enclosed nature of the depositional basin retaining warmth, relative to the open ocean of similar latitudes.

Occurrence of Inoceramus in the South Atlantic and oxygen isotopic paleotemperatures in DSDP Hole 75-530A

Inoceramus occurs in every DSDP hole that penetrated Cretaceous sediments in the South Atlantic Ocean, and specimen occurrence has been mapped in detail for each core. Oxygen and carbon isotope measurements were completed on 18 Inoceramus specimens from Hole 530A. Textural evidence of diagenesis is accompanied by depletion in 18O. Paleotemperature results were obtained from 11 well-preserved specimens. Bottom water temperatures in the Angola Basin decreased from 23°C during the Coniacian to 13°C near the end of the Campanian.

Cooperative or collaborative learning: Is there a difference in university students’ perceptions?

The hypothesis that the same educational objective, raised as cooperative or collaborative learning in university teaching does not affect students’ perceptions of the learning model, leads this study. It analyses the reflections of two students groups of engineering that shared the same educational goals implemented through two different methodological active learning strategies: Simulation as cooperative learning strategy and Problem-based Learning as a collaborative one. The different number of participants per group (eighty-five and sixty-five, respectively) as well as the use of two active learning strategies, either collaborative or cooperative, did not show differences in the results from a qualitative perspective.

Molecular abundances in the magellanic clouds III. LIRS 36, a star-forming region in the Small Magellanic Cloud

Detections of CO, CS, SO, C2H, HCO+, HCN, HNC, H2CO, and C3H2 are reported from LIRS 36, a star-forming region in the Small Magellanic Cloud. (CO)-O-18, NO, CH3OH, and most notably CN have not been detected, while the rare isotopes (CO)-C-13 and, tentatively, (CS)-S-34 ar,seen. This is so far the most extensive molecular multiline study of an interstellar medium with a heavy element depletion exceeding a factor of four.