Lehmann K.,Geological Survey of Germany
Journal of Applied Geophysics | Year: 2010
Correction concepts for the elimination of environmental influences on gamma-ray logs have been published in a number of articles and in guidelines by service companies. However, these widely-used processing rules for open- and cased-hole measurement conditions have been presented in different forms using different assumptions. For a detailed comparison, these concepts were reduced to simple analytical formula with the application of the same units and scaling to common, standardised conditions. For geological and technical drilling, environmental influences like borehole geometry, casing configuration and material, as well as mud density have turned out to represent the most important effects for a characterisation of environmental conditions. Typical case histories show that correction processing may lead to differing results, depending on the chosen presumptions. A thorough analysis of different types of influences and a careful choice of adequate correction procedures substantially improve the quality of gamma-ray log data. Further implications of these analytical correction rules permit also the quantitative interpretation of logs in dry cased-hole intervals and with the presence of tool joints or casing collars. The latter effect is widely underrated but is proven here to be a necessary step in precise gamma-ray log processing. © 2009 Elsevier B.V. All rights reserved.
Salamon M.,Geological Survey of Germany |
Konigshof P.,Senckenberg Institute
Gondwana Research | Year: 2010
The Rheinisches Schiefergebirge in the Rheno-Hercynian zone of the mid-European Variscides was geographically situated on Laurussia's southern shelf during the Devonian. In its eastern part (Lahn-Dill area), Givetian coarse clastic sediments, formerly misinterpreted as transgressional conglomerates, are recognised as olistostrome deposits intercalated in basinal sediments that document a phase of rifting on the southern shelf of Laurussia. The clastic components, redeposited as olistolithes and rounded boulders, are locally derived rocks of Emsian and Givetian age. The olistostromes show facies patterns comparable with other syn-rift deposits. The proximal facies is characterised by olistolithes and slideflow debrites, overlain by debrites and intercalated with turbidites. The distal facies is represented by intercalation of debrites and turbidites. Both grade upwards into basinal sedimentation. Based on conodont stratigraphy, the redeposition lasted from the Middle varcus Zone to the disparilis Zone. During the Middle varcus Zone footwall uplift raised the sedimentary column of the source area by about 500 m above, which brought it above sea level. Rifting of the Laurussian shelf as a result of hinterland transtension and extension caused by the oblique collision of Peri-Gondwana with Laurussia provides the most plausible explanation for the development of the olistostromes, olistolithes and slideflow debrites in the eastern Rheinisches Schiefergebirge. © 2009 Elsevier B.V. All rights reserved.
Dustira A.M.,University of Tromso |
Wignall P.B.,University of Leeds |
Joachimski M.,Friedrich - Alexander - University, Erlangen - Nuremberg |
Blomeier D.,Norwegian Polar Institute |
And 2 more authors.
Palaeogeography, Palaeoclimatology, Palaeoecology | Year: 2013
The Permian-Triassic extinction event is considered to be the most devastating environmental crisis of the Phanerozoic. With many coinciding factors involved, the role of marine anoxia during the extinction is still poorly understood. In this study a boreal Permian-Triassic Boundary (PTB) section from Svalbard, Norway has been investigated with the aim of better understanding the timing and nature of local marine anoxia onset and extinction events across the PTB. The section comprises the Kapp Starostin and Vikinghøgda formations; δ13Corg values indicate the PTB is located within the lower part of the Vikinghøgda Formation. Lag deposits at the top of the Kapp Starostin Formation indicate a marine hiatus and ensuing transgression during the Late Permian shortly before the extinction event, implying concurrence of major ecological changes and sea-level rise. Pyrite framboid size distributions and total organic carbon (TOC) were used to evaluate bottom water oxygen conditions, and show that changes in bottom water redox conditions and extinction are clearly linked. Oxic to dysoxic bottom water conditions prevailed during deposition of Kapp Starostin Formation sediments and changed to anoxic to euxinic conditions above the formation boundary. The onset of anoxia is not abrupt but rather shows a gradual increase within the Kapp Starostin Formation during the Late Permian. The tipping point where bottom waters reach a long-term state of anoxia to euxinia coincides with the final extinction event, though changes in biotic assemblages at the top of the Kapp Starostin Formation indicate a marine ecosystem crisis prior to this. Oxygen depletion in the boreal region, as seen in our study section and correlating to Greenland and Arctic Canada, seems to be consistently more severe than in lower latitude settings. © 2013 Elsevier B.V.
Dutta S.,Indian Institute of Technology Bombay |
Hartkopf-Froder C.,Geological Survey of Germany |
Witte K.,FH Aachen |
Brocke R.,Senckenberg Institute |
Mann U.,Julich Research Center
International Journal of Coal Geology | Year: 2013
Transmission micro-FTIR spectroscopy has been conducted to elucidate the macromolecular structure of well-preserved fossil palynomorphs including prasinophycean algae, megaspores, chitinozoans, and scolecodonts. Plant and arthropod cuticles which may be present in palynological residues have also been investigated. Important differences are noted among these palynomorph groups regarding the intensities of CHx, CO and aromatic CC absorptions. Tasmanites, Leiosphaeridia, and plant cuticles are characterized by stronger aliphatic CHx stretching (3000-2800cm-1), strong CH3 (1460-1450cm-1), and intense CO group (1710-1700cm-1) absorptions. Aromatic CC stretching (1610-1560cm-1) absorptions are less intense and aromatic CH out of plane (900-750cm-1) absorptions are absent. In contrast, chitinozoans, scolecodonts, and arthropod cuticles show intense aromatic CC stretching (1620-1560cm-1) and aromatic CH out of plane (900-750cm-1) absorptions. Aliphatic CHx stretching (3000-2800cm-1) and CO group (1710-1700cm-1) absorptions are less intense. Megaspores are characterized by stronger aliphatic CHx stretching (3000-2800cm-1), strong CH3 (1460-1450cm-1), and moderate aromatic CC stretching (1610-1560cm-1) and CO group (1710-1700cm-1) absorptions. The CH2/CH3 intensity ratio has been used to assess the relative chain length and degree of branching. The aliphatic components in Tasmanites, Leiosphaeridia, and plant cuticles are longest chained and least branched whereas those in chitinozoans, scolecodonts, and arthropod cuticles are shortest chained and most branched. Megaspores show intermediate CH2/CH3 ratio. The present study demonstrates that palynomorphs differ in functional group chemistry and this spectroscopic technique can be useful to assign biological affinity of enigmatic palynomorphs. Furthermore, micro-FTIR spectroscopy provides insights into the hydrocarbon generating potential of different fossil palynomorph groups. © 2013 Elsevier B.V.
Banning A.,RWTH Aachen |
Rude T.R.,RWTH Aachen |
Dolling B.,Geological Survey of Germany
Journal of Hazardous Materials | Year: 2013
Cretaceous shallow marine sediments from northwestern Germany exhibit a distinct colour and geochemical boundary in a depth of several decametres, witnessing a terrestrial oxidative paleo redox process which resulted in cement loss and oxidation of Fe(II) phases. Sediment samples were obtained from boreholes drilled in near-coastal and further basinward paleo environments, including both reduced and oxidized redox facies, to characterize As and Fe occurrence in unaltered layers and redistributional consequences of the redox event. Geochemical and mineralogical composition and As fractionation were assessed. Arsenic resides in pyrite in the reduced section with a bulk rock maximum concentration of 39μgg-1, calculated Aspyrite is ~0.2wt.%. Siderite concretions in the fine sands do not function as As sinks, neither does glauconite whose general As/Fe leaching behaviour was characterized. In the zone of redox transition, reduced and oxidized phases coexist and elevated As concentrations (up to 73μgg-1) with high proportions of reactive As were detected. Arsenic behaviour changes from relatively homogeneous Fe sulphide-control in the unaltered sediments to very heterogeneous Fe hydroxide-control above the paleo redox boundary. The studied characteristics determine recent As availability in the subsurface and must be considered during groundwater extraction from this highly important aquifer. © 2012 Elsevier B.V.