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  • 1
    Electronic Resource
    Electronic Resource
    Wildfires and seasonal aridity recorded in Late Cretaceous strata from south-eastern Arizona, USA (2005)
    Oxford, UK : Blackwell Science Ltd
    Sedimentology 52 (2005), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Lithostratigraphic and organic chemostratigraphic studies of fluvial/lacustrine sediments in the Late Cretaceous Fort Crittenden Formation in south-eastern Arizona USA, reveal changes in palaeoclimate and tectonics as well as associated fluctuations in lake level. The lower Fort Crittenden is dominated by marginal wetland to deep-water lake deposits, whereas the upper Fort Crittenden is characterized by wetland to deltaic deposits. Abundance of polycyclic aromatic hydrocarbons (PAH) and reflectance of fusinite substantiate the impact of wildfires within the watershed. Organic geochemical evidence of wildfires is linked with sedimentological indicators of seasonal aridity suggesting that wildfires were common occurrences. Sedimentological evidence for seasonal aridity includes mottles and pseudoslickensides on ped structures within wetland mudstones. Distinct variations in PAH assemblages, characterized by the number of aromatic rings, indicate that there were variations in the intensities of wildfires, assuming no variations in the types of fuel. Fusinite reflectance values are consistent with combustion temperatures from 470 to 550 °C observed in modern wildfires.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.2005.00712.x
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  • 2
    Electronic Resource
    Electronic Resource
    Geochemical and climatic effects of increased marine organic carbon burial at the Cenomanian/Turonian boundary (1988)
    [s.l.] : Nature Publishing Group
    Nature 335 (1988), S. 714-717 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The stratigraphic position of the maximum values of the positive excursion in the carbon isotope composition of organic carbon (513Corg) corresponds closely with the maximum of the excursion in the corresponding quantity for carbonate (5I3Ccarb) (Fig. 2), within the latest Cenomanian and earliest ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/335714a0
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  • 3
    Electronic Resource
    Electronic Resource
    Stable Sulfur Isotopic Evidence for Historical Changes of Sulfur Cycling in Estuarine Sediments from Northern Florida (1999)
    Springer
    Aquatic geochemistry 5 (1999), S. 249-268 
    Details
    ISSN: 1573-1421
    Keywords: sulfate ; stable sulfur isotopes ; delta 34S ; porewaters ; bacterial sulfate reduction ; diffusion modeling ; sulfide reoxidation ; pyrite ; anthropogenic effects ; organic contamination ; stable carbon isotopes ; delta 13C ; estuarine sediments ; Florida ; St. Andrew Bay ; pulp mill effluent ; lignin ; lignocellulose
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Data on abundance and isotopic composition of porewater and sedimentary sulfur species are reported for relatively uncontaminated and highly contaminated fine-grained anoxic sediments of St. Andrew Bay, Florida. A strong contrast in amount and composition of sedimentary organic matter at the two sites allows a comparative study of the historical effects of increased organic loading on sulfur cycling and sulfur isotopic fractionation. In the contaminated sediments, an increase in organic loading caused increased sedimentary carbon/sulfur ratios and resulted in higher rates of bacterial sulfate reduction, but a lower efficiency of sulfide oxidation. These differences are well reflected in the isotopic composition of dissolved sulfate, sulfide, and sedimentary pyrite. Concentration and isotopic profiles of dissolved sulfate, organic carbon, and total sulfur suggest that the anaerobic decomposition of organic matter is most active in the upper 8cm but proceeds at very slow rates below this depth. The rapid formation of more than 90% of pyrite in the uppermost 2 cm which corresponds to about 3 years of sediment deposition allows the use of pyrite isotopic composition for tracing changing diagenetic conditions. Sediment profiles of the sulfur isotopic composition of pyrite reflect present-day higher rates of bacterial sulfate reduction and lower rates of sulfide oxidation, and record a profound change in the diagenetic cycling of sulfur in the contaminated sediments coincident with urban and industrial development of the St. Andrew Bay area.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009661812641
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