Hydrochemistry,origin and evolution of sedimentary subsurface fluids: II. Early diagenetic pore-water evolution in high sedimentation-rate offshore basins

High sedimentation-rate basins are characteristic of the continental margins, where sedimentation rates up to 500m/Ma and more are no exception. The sediments are rich in organic matter and undergo a well-established sequence of bacterial oxidation reactions, starting at the sediment/water interface with: (1) the oxidation zone (absent in euxinic basins), which is followed downwards by (2) the nitrate reduction zone, (3) the sulfate reduction zone, (4) the carbonate reduction zone, (5) the fermentation zone and (6) the decarboxylation zone, which marks the onset of thermocatalytic reactions characteristic of the intermediate stage (and deeper stages) of diagenesis. This sequence of bacterially mediated organic-matter decomposition reactions in rapidly deposited sediments on the continental margins is well reflected in the vertical trends of pore-water chemistry. Carbon isotopic fractionation permits to distinguish between zones (1) to (3) with negative δ¹³C values for the CO₂ generated, and between zones (4) and (5) with increasingly heavier carbon-isotopes in CO₂ (up to + 15 to + 25‰ δ¹³C). The formation of gas-hydrates causes characteristic chemical and isotopic signatures in pore waters retrieved from hydrate-bearing sediments. After hydrate decomposition (in the sampling process or at the base of hydrate zones) marked chlorimity decreases accompanied by increases in heavy oxygen isotopes are observed. These are distinctly different from the effects of meteoric water influx, which are not accompanied by positive δ¹⁸O values. The opposite trend of increasing salinity at shallow burial depths, rather than pore-waters freshening, is observed in the vicinity of evaporites.     

Direct determination of the quartz-coesite transition by in situ X-ray measurements

The quartz-coesite transition has been determined over the temperature range 600–1100° C by in Situ X-ray measurements with NaCl as internal pressure standard. An internally heated high-pressure X-ray apparatus (Belt-type) was used which is based on the principle developed by Freud and Sclar (1969). The obtained quartz-coesite equilibrium line may be represented by the equation P=31±1+0.0075 T where P is in kb and T in ° C.     

The patterns of centrality in the province of Bursa (Turkey)Die zentralörtliche struktur der provinz Bursa (Türkei)La hiérarchie des lieux centraux dans la province de Bursa (Turquie)

The paper deals with the problem of central place hierarchies in developing countries. If the information collected in the province of Bursa — by means of the questionaire method and in field work — is interpreted from the point of view of services offered in the central place alone, a multi-graded hierarchy is evident. However, the central place-oriented behaviour of the rural population of Bursa province reveals a two-graded hierarchy: towards the respective district centre and towards the provincial capital (Bursa city). The different qualities of services offered in the district centres must be explained in the light of different socio-economic standards in the various regions of the province of Bursa.     

über Vereisungsperioden und Vereisungsspuren in Brasilien

Zusammenfassung In Brasilien wurden Vereisungsspuren vom Präkambrium bis zum Oberkarbon festgestellt. Aus den bisherigen Untersuchungen ergibt sich, daß das gesamte Paläozoikum bis zum Beginn des Perm kalt war. Präkambrische bis kambrische Glazialschichten weisen die Lavras-Serie in Minas und Bahia auf. Gotlandische Tillite und Driftablagerungen liegen im Staate Paraná; unmittelbar darüber beobachtet man unterdevonische Sandsteine mit glazialem Driftmaterial. Auch das Oberdevon in Nordost-Brasilien enthält Tillite. In der vorliegenden Arbeit werden besonders die Vereisungsspuren in Südbrasilien eingehender behandelt. Die jetzt getrennten Gondwanablöcke von Südamerika und Afrika bildeten früher eine geschlossene Einheit. Ohne transversale Krustenverschiebungen sind die auf den verschiedenen Gondwanaländern verteilten Vereisungsspuren nicht zu erklären. Damit entfällt die Existenz eines südatlantischen Urozeans.     

Meteorologische Faktoren im Gelände nahe Tromsö während der Schneeschmelze

Zusammenfassung Für ein schmelzendes Schneefeld im Gebirge bei Tromsö wird die Energieaufnahme abgeschätzt. Stichprobenhafte Beobachtungen von Strahlung, Temperatur, Feuchtigkeit und Wind im Gelände werden auf Registrierungen in Tromsö bezogen und aus stochastischen Zusammenhängen die tägliche Schmelzwassermenge während zwei Monaten überschlagsmässig bestimmt. Sie wird mit dem beobachteten Abfluss verglichen.

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Summary For a melting snow field in the mountains near Tromsö the energy input is estimated. Samplelike observations of radiation, temperature, humidity and wind in the field are referred to registrations of these variables at Tromsö. From the stochastic relations the daily snow melt is approximately calculated through two months, and is compared with observed runoff.

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Symbole A atmosphärische Gegenstrahlung - a Konstante - Albedo - b Konstante - c Konstante - D Richtung - Differenz - E effektive Entfernung (Korrelation) - e Dampfdruck - F relative Feuchte - G Globalstrahlung - H spezifische Feuchte - K kurzwelliger Strahlungssaldo - k Konstante - L langwelliger Strahlungssaldo - N Niederschlagsmenge - n Anzahl Beobachtungen - Gebietsfläche - p Korrelationsparameter - Q Saldo sensibel und latent übertragener Wärme - q Wärmeübergangszahl - Stefan-Boltzmann-Konstante - T Temperatur - V Windgeschwindigkeit - W Schmelzwassermenge;W ₁ undW ₂ abgeschätzte und beobachtete Abflussintensität - Bewölkungsgrad - Z vertikale Höhe - Æ Äquivalenttemperatur - bezüglich Bewölkung 3/10 - bezüglich Bewölkung >3/10 - * bezüglich Schneeoberfläche - ' (Index) bezeichnet Referenzwert     

Assessment of freshwater diatoms as quantitative indicators of past climatic change in the Yukon and Northwest Territories,Canada

We identified, enumerated, and interpreted the diatom assemblages preserved in the surface sediments of 59 lakes located between Whitehorse in the Yukon and Tuktoyaktuk in the Northwest Territories (Canada). The lakes are distributed along a latitudinal gradient that includes several ecoclimatic zones. It also spans large gradients in limnological variables. Thus, the study lakes are ideal for environmental calibration of modern diatom assemblages. Canonical correspondence analysis, with forward selection and Monte Carlo permutation tests, showed that maximum lake depth and summer surface-water temperature were the two environmental variables that accounted for most of the variance in the diatom data. The concentrations of sodium and calcium were also important explanatory variables. Using weighted-averaging regression and calibration techniques, we developed a predictive statistical model to infer lake surface-water temperature, and we evaluated the feasibility of using diatoms as paleoclimate proxies. This model may be used to derive paleotemperature inferences from fossil diatom assemblages at appropriate sites in the western Canadian Arctic.     

Parasite findings in archeological remains: Diagnosis and interpretation

Paleoparasitology has contributed to resolving the debate about the peopling of the Americas and determining the antiquity of human parasite infection. Hookworm (Ancylostomidae) and whipworm (Trichuris trichiura) and other exclusive human intestinal parasites have been recorded in pre-Columbian America. These parasite species originated in pre-hominids and have accompanied humans across continents when people went out of Africa. However, for those human populations that crossed the Bering Land Bridge from Siberia to Alaska, cold climate conditions hampered parasite transmission. Alternative migration routes have been proposed to explain the presence of these parasites in pre-Columbian populations in the Americas. Other parasites were established in the New World long before humans entered the American continents.One such malady is Chagas disease. Chagas disease, caused by Trypanosoma cruzi, offers an example of how animals and humans have interacted in the past. Classical theory points to the origin and dispersion of human T. cruzi infection among Andean populations, starting with sedentary habits and animal domestication 6000 years ago. However, recent PCR results in mummified bodies outside the Andean region have challenged this theory. Pre-Columbian Brazilian mummies were found positive for T. cruzi infection, raising an alternative hypothesis on the antiquity of Chagas disease in the Americas. Paleoparasitology is a new tool to study past events, shedding light on human and other animal behavior, migration routes, diet, and other aspects of host–parasite environment evolution.     

Effects of spring warming and mixing duration on diatom deposition in deep Tiefer See,NE Germany

Monitoring during three meteorologically different spring seasons in 2012, 2013, and 2014 revealed that temperature increase in spring, which influences spring lake mixing duration, markedly affected nutrient availability and diatom deposition in a sediment trap close to the bottom of deep Tiefer See, NE Germany. Deposition of Stephanodiscus taxa and small Cyclotella taxa was much higher after late ice out and a deep, short lake mixing period in spring 2013, compared to that after gradual warming and lengthy lake mixing periods in spring 2012 and 2014, when only brief or marginal ice cover occurred. Availability of dissolved Si and P was 33 and 20 % higher, respectively, in 2013 compared to 2014. The observed relation between high (low) diatom deposition and short (lengthy) mixing duration in spring was applied to varved sediments deposited between AD 1924 and 2008. Low detrital Si content in trapped material and a sediment core enabled use of µXRF-counts of Si as a proxy for diatom silica. The spring mixing duration for 1951–2008 was derived from FLake-model calculations. The spring warming duration related to lake mixing was approximated from air temperatures for 1924–2008 using the dates when daily mean air temperature exceeded 5 °C (start) and 10 °C (end). Diatom silica deposition showed a significant (p < 0.0001) inverse linear relationship with the modeled spring mixing duration (R² = 0.36) and the spring warming duration (R² = 0.28). In both cases, the relationship is strengthened when data from the period of low diatom production (1987–2005) is excluded (R² = 0.59 and R² = 0.35). Part of this low diatom production is related to external nutrient supply that favored growth of cyanobacteria at the expense of diatoms. This approach shows that diatom Si deposition was strongly influenced by the availability of light and nutrients, related to the duration of lake mixing and warming in spring, during most of the studied period. The remaining unexplained variability, however, indicates that additional factors influence Si deposition. Further tests in other deep, temperate lakes are necessary to verify if this relation is a common feature and consequently, if diatom Si can be used as a proxy for spring mixing duration in such lakes.     

Secondary Ion Mass Spectrometry Bias on Isotope Ratios in Dolomite–Ankerite,Part I: δ18O Matrix Effects

We document the development of a suite of carbonate mineral reference materials for calibrating SIMS determinations of δ¹⁸O in samples with compositions along the dolomite–ankerite solid solution series [CaMg(CO₃)₂–CaFe(CO₃)₂]. Under routine operating conditions for the analysis of carbonates for δ¹⁸O with a CAMECA IMS 1280 instrument (at WiscSIMS, University of Wisconsin‐Madison), the magnitude of instrumental bias along the dolomite–ankerite series decreased exponentially by ~ 10‰ with increasing Fe content in the dolomite structure, but appeared insensitive to minor Mn substitution [< 2.6 mol% Mn/(Ca+Mg+Fe+Mn)]. The compositional dependence of bias (i.e., the sample matrix effect) was calibrated using the Hill equation, which relates bias to the Fe# of dolomite–ankerite [i.e., molar Fe/(Mg+Fe)] for thirteen reference materials (Fe# = 0.004–0.789); for calibrations employing either 10 or 3 μm diameter spot size measurements, this yielded residual values ≤ 0.3–0.4‰ relative to CRM NBS 19 for most reference materials in the suite. Analytical precision was ± 0.3‰ (2s, standard deviations) for 10‐μm spots and ± 0.7‰ (2s) for 3‐μm spots, based on the spot‐to‐spot repeatability of a drift monitor material that ‘bracketed’ each set of ten sample‐spot analyses. Analytical uncertainty for individual sample analyses was approximated by a combination of precision and calibration residual values (propagated in quadrature), suggesting an uncertainty of ± 0.5‰ (2s) for 10‐μm spots and ± 1‰ (2s) for 3‐μm spots.