Wrede V.,Geologischer Dienst Nordrhein Westfalen
Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften | Year: 2013
The 526 m deep borehole Paffrather Mulde 1 revealed a sequence of Upper Devonian strata (Adorfian-Dasbergian) within the Bergisch Gladbach-Paffrath Synclinorium. The unit is strongly affected by numerous tectonic faults. Dips of strata as reconstructed from combined core and borehole data are generally directed towards SE. Within the deepest part of the borehole, orientation data are not available and interpretation of the structural setting is ambiguous. Combined with folding, numerous thrusts occur, which are part of the Bergian Thrust Zone. In part they cut the stratigraphic sequence as synthetic faults, dipping steeper than bedding planes. Other thrusts, however, form flat dipping shear planes. For one of the thrusts a stratigraphic throw of at least 150 m can be proved. Another major thrust has to be inferred closely to the south of the borehole. In the area between the borehole and the main branch of the Bergian Thrust in the south, the existence of a deeply downfolded syncline is most probable, containing uppermost Devonian or even Lower Carboniferous strata. In detail different interpretations of the exposed structure are possible, depending on the interpretation of the deepest part of the drilled section as being a syncline or anticline. Besides these Variscan structures neotectonic faults occurred in the borehole. Normal faults and strike-slip faults, striking NW-SE, are most likely related to the subsidence of the Lower Rhine Embayment during the Tertiary. The main fault inferred from the borehole data and adjacent outcrops causes a stratigraphic gap of at least 425 m. In the context with other boreholes and exposures in the neighbourhood a graben structure of some 400-500 m subsidence can be recognised, here named as "Refrath Graben". The interference of this graben structure with the Bergisch Gladbach-Paffrath Synclinorium explains the occurrence of youngest Palaeozoic strata (uppermost Devonian, "Dasbergian"), known so far within this region. © 2013 E. Schweizerbart'sche Verlagsbuchhandlung, Stuttgart, Germany.
Scharer U.,University of Munster |
Scharer U.,University of Nice Sophia Antipolis |
Berndt J.,University of Munster |
Scherer E.E.,University of Munster |
And 4 more authors.
Chemical Geology | Year: 2012
Detrital zircon grains of the Cenozoic Lower Rhine Basin were dated by the U-Pb method and simultaneously analyzed for initial Hf signatures to (1) identify distinct geodynamic events recorded in the W-European basement and cover rocks and (2) estimate the addition of juvenile crust in relation to these. Approximately 350 zircon grains extracted from 4 Miocene to Quaternary sand samples were investigated by back-scattered electron (BSE) and cathodoluminescence (CL) imaging. One third of these zircons were found to be sufficiently homogeneous for laser ablation U-Pb dating, which was performed by two individual and spatially well separated laser-spot analyses on the same grain, substantiating zircons have identical ages for the two intra-grain analyses. Approximately 40 zircons showed different ages. Our U-Pb dating results document distinct periods of primary magmatic zircon growth between 2.7 and 0.03. Ga. These ages correspond to worldwide known subduction-collision cycles. The oldest terrains exposed today along the Rhine River and the Alps belong to the Variscan cycle. Therefore, all zircon grains older than ca. 0.4. Ga must have been extracted from Paleozoic or Mesozoic-Cenozoic cover rocks containing detrital grains inherited from pre-Variscan basement; only the Cenozoic zircons require direct transport to the basin.From the dated homogeneous zircons 34 grains were selected for Hf isotope analysis, showing large variations in initial Hf isotope ratios (εHf i) between -10.9 and +15.2. Twelve of the 13 Precambrian grains yield positive or zero εHf i values, with a single 1025-Ma old grain having a negative value of -10.9. For the 21 zircon grains younger than 0.6Ga, a series of 9 grains yield positive or zero εHf i, whereas the remaining 12 zircons have negative values as low as -5.8. Approximately 60% of the zircon crystals reflect addition of juvenile crust having positive or zero εHf i being extracted from the mantle around the time indicated by their U-Pb ages. For some cases, juvenile crust addition may be somewhat older than indicated by the U-Pb ages because zircon growth may occur during later differentiation of rocks originally devoid of zircon. For such cases, εHf i values are necessarily less positive than that of the juvenile magma, depending on the Lu/Hf and crustal residence times of the zircon-free rock. A few εHf i values between +11.4 and +15.2 corroborate the existence of highly fractionated, Lu-enriched and Hf-depleted asthenospheric mantle in Mid-Proterozoic times. In agreement with earlier detrital zircon studies, our new data demonstrate that crustal recycling during continent collision events significantly increased in Phanerozoic times, being relatively rare during Precambrian times where intra-plate plume activity and oceanic arc attachment were dominant. © 2011 Elsevier B.V.
Richter D.K.,Ruhr University Bochum |
Gotte T.,Goethe University Frankfurt |
Stritzke R.,Geologischer Dienst Nordrhein Westfalen
Geologie und Palaeontologie in Westfalen | Year: 2014
A post-variscic karst cavity in the Middle Devonian limestone sequence of the quarry Asbeck (Honnetal) contains a 5.5 m thick sequence of silty and muddy sediments of Neogene age below sandy Pleistocene deposits. Palynological investigation reveals a Miocene age of the silt-series (SP9 sensu BRELIE, 1988) but no pre-quaternary forms have been found in the upper sandy part of the sediments. The fine, Miocene deposits are laminated and are suggested to be transported by turbidity currents with low density into the cavity, while the badly sorted, coarse sediments in the upper part of the sequence are probably transported by massflows higher viscosity. This sedimentological interpretation is in accord with [Laugfacetten] at the walls of the cavity, which indicate stagnant water or at least very low streaming. The provenance areas of the sediments are outside the Devonian limestones for both parts of the sequence. Glaucony which have been found in the sediments indicates that partly Upper Cretaceous sediments are recycled. © 2014 Landschaftsverband Westfalen-Lippe.
Dutta S.,Indian Institute of Technology Bombay |
Hartkopf-Froder C.,Geologischer Dienst Nordrhein Westfalen |
Mann U.,Julich Research Center |
Wilkes H.,Helmholtz Center Potsdam |
And 2 more authors.
Lethaia | Year: 2010
Biogeochemistry and molecular taphonomy of biopolymers of marine zoomorphs are poorly known. In order to obtain insights into this issue we report on the biogeomacromolecular composition of hand-picked, well-preserved scolecodonts of Ordovician, Silurian and Devonian age using micro-Fourier transform infrared (micro-FTIR) spectroscopy, Curie point pyrolysis-gas chromatography-mass spectrometry (Cupy-GC-MS) and tetramethylammonium hydroxide (TMAH)-assisted thermochemolysis-GC-MS. The present study reveals that scolecodonts are composed of both aliphatic and aromatic moieties. The micro-FTIR spectra of scolecodonts are characterized by aliphatic CHx (3000-2800 and 1460-1450/cm) and CH3 (1375/cm) absorptions and aromatic C=C (1560-1610/cm) and CH (3050/cm and 700-900/cm) absorptions. The major pyrolysis products from the scolecodonts include aromatic hydrocarbons such as alkylbenzenes, alkylnaphthalenes and alkylphenols. Aliphatic hydrocarbons are represented by a homologous series of n-alkenes and n-alkanes. The compounds released upon thermochemolysis with TMAH are saturated and unsaturated fatty acids (as their methyl esters), n-alkenes/alkanes and aromatic acids (as their methyl esters). No protein/amino acid-derived compounds have been recognized in the pyrolysates or in the thermochemolysates, and it is concluded that protein/amino acid-related compounds, which are commonly found in the jaws of extant polychaetes, were destroyed due to diagenetic processes. Obviously, excellent morphological preservation and low thermal alteration are not paralleled by a similar degree of chemical preservation. □Biogeomacromolecules, micro-FTIR, pyrolysis-GC-MS, scolecodonts, thermochemolysis-GC-MS. © 2009 The Authors, Journal compilation © 2009 The Lethaia Foundation.
Luminescence dating of Last Glacial and Early Holocene fluvial deposits from the Lower Rhine - Methodological aspects and chronological framework [Lumineszenzdatierung an letztglazialen und frühholozänen flusssedimenten vom niederrhein - Methodische aspekteund chronologischer rahmen]
Lauer T.,Leibniz Institute for Applied Geophysics |
Frechen M.,Leibniz Institute for Applied Geophysics |
Klostermann J.,Geologischer Dienst Nordrhein Westfalen |
Krbetschek M.,TU Bergakademie Freiberg |
And 2 more authors.
Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften | Year: 2011
Luminescence dating was applied to Last Glacial and Early Holocene fluvial deposits derived from the Lower Rhine. The aim was to obtain a robust chronology for the sections (open pits) under study in order to contribute to a better understanding of past fluvial dynamics of the River Rhine. Furthermore, different luminescence dating methods (quartz OSL, feldspar IRSL and pIRIR as well as pIR-YOSL) were compared and tested by applying them to sands sampled at Rheinberg and Monheim-Hitdorf where independent age control is provided by intercalated pumice originating from the eruption of the Laacher See Volcano, about 12 900 a ago. The obtained quartz ages are in agreement with the age of the marker tephra. Also the feldspar luminescence age estimates agree with the quartz OSL ages. For the Rheinberg and Monheim-Hitdorf sections the obtained ages now yield a very precise chronology. Based on this chronology a very rapid fluvial aggradation could be demonstrated for the sediment succession at the Monheim-Hitdorf site occurring during Younger Dryas. At Rheinberg it was shown that the Laacher See pumice was reworked for long time as the luminescence ages point to a Boreal period of aggradation (~4 ka after the eruption of the volcano). For the older Lower Terrace sites (Aloysiushof/Dormagen, Niederkassel, Libur) the ages now yield a reliable chronological framework for the fluvial aggradation helping to better understand the timing of changes in fluvial dynamics. © 2011 E. Schweizerbart'sche Verlagsbuchhandlung.