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  • 1
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    Results on Core-Log-Seismic-Integration in hard-rock environments using the ICDP drilling project COSC-1, Sweden (2018)
    In:  [Poster] In: AGU Fall Meeting 2018, 10.-14.12.2018, Washington, D.C., USA .
    Details
    Publication Date: 2019-02-15
    Description: As part of the ICDP priority program “Collisional Orogeny of the Scandinavian Caledonides (COSC)” we are investigating the geophysical properties of the rocks from the Seve Nappe Complex (SNC) using the COSC-1 borehole (Sweden). This project has two main objectives. The first, geological aim is to establish a high-resolution seismic stratigraphy applying Core-Log-Seismic-Integration (CLSI) to a metamorphic setting to improve our understanding of the tectonic and structural geological processes that led to the formation of the SNC and, in particular, how shear stress was partitioned and how it affected the geophysical properties. The second, methodological objective aims at learning how the CLSI techniques can be applied for metamorphic rocks although they have been developed mainly for hydrocarbon reservoirs in lithified sediment rocks. Here, we use information from two sets of wireline logs and tie them to a 2D and 3D seismic surveys from the SNC, a multi-azimuthal walkaway vertical seismic profile, and a high-resolution zero-offset vertical seismic profile, and combine them through Log-Seismic-Integration (LSI). From density and sonic information we have generated synthetic seismograms and compared them to zero offset seismic traces and traces from the processed surface 3D seismic data that were extracted at the location of the borehole. As expected, the results show significant deviations between synthetic and measured seismograms due to seismic wave propagation artefacts, noise both in the seismic and in the downhole logging data, imperfect coupling of the tools in the boreholes and uncertainty in the depth measurements during logging as well as anisotropy in the seismic velocities. Nevertheless, we identify a number of prominent reflections that can be linked e.g. to amphibolite zones as well as to measured seismograms which will allow us to extrapolate the lithology from the borehole. In order to reveal physical properties of the methamorphic setting the next step is to improve the seismic processing with an iterative process to minimize the mismatch between the synthetic and measured seismograms.
    Type: Conference or Workshop Item , NonPeerReviewed
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    OceanRep: Poster
  • 2
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    Challenges of Core-Log-Seismic Integration in metamorphic environments: A case study for the ICDP drilling project COSC-1, Sweden (2019)
    In:  [Talk] In: EGU General Assembly 2019, 08.-13.04.2019, Vienna, Austria .
    Details
    Publication Date: 2019-06-03
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
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    OceanRep: Talk
  • 3
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    Correlation of core and downhole seismic velocities in high-pressure metamorphic rocks: A case study for the COSC-1 borehole, Sweden (2020)
    In:  [Paper] In: EGU General Assembly 2020, 03.05.-08.05.2020, Vienna, Austria .
    Details
    Publication Date: 2020-05-20
    Type: Conference or Workshop Item , NonPeerReviewed
    Format: text
    DOI: 10.5194/egusphere-egu2020-13955
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    OceanRep: Conference paper
  • 4
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    Correlation of core and downhole seismic velocities in high-pressure metamorphic rocks: a case study for the COSC-1 borehole, Sweden (2020)
    Copernicus Publications (EGU)
    Details
    Publication Date: 2023-02-08
    Description: Deeply rooted thrust zones are key features of tectonic processes and the evolution of mountain belts. Exhumed and deeply-eroded orogens like the Scandinavian Caledonides allow to study such systems from the surface. Previous seismic investigations of the Seve Nappe Complex have shown indications for a strong but discontinuous reflectivity of this thrust zone, which is only poorly understood. The correlation of seismic properties measured on borehole cores with surface seismic data constrains the origin of this reflectivity. In this study, we compare seismic velocities measured on cores to in situ velocities measured in the borehole. The core and downhole velocities deviate by up to 2 km/s. However, velocities of mafic rocks are generally in close agreement. Seismic anisotropy increases from about 5 to 26 % at depth, indicating a transition from gneissic to schistose foliation. We suggest that differences in the core and downhole velocities are most likely the result of microcracks mainly due to depressurization. Thus, seismic velocity can help to identify mafic rocks on different scales whereas the velocity signature of other lithologies is obscured in core-derived velocities. Metamorphic foliation on the other hand has a clear expression in seismic anisotropy. These results will aid in the evaluation of core-derived seismic properties of high-grade metamorphic rocks at the COSC-1 borehole and elsewhere. In particular, they show that core log seismic integration via synthetic seismograms requires wireline logging data in any but mafic lithologies.
    Type: Article , PeerReviewed
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 5
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    Core-log-seismic integration in metamorphic rocks and its implication for the regional geology: A case study for the ICDP drilling project COSC-1, Sweden (2021)
    AGU (American Geophysical Union) | Wiley
    Details
    Publication Date: 2024-02-07
    Description: Continental collision causes deformation in the crust along shear zones. However, the physical and chemical conditions at which these zones operate and the deformation processes that enable up to hundreds of km of tectonic transport are still unclear because of the depth at which they occur and the challenges in imaging them. Ancient exhumed collision zones allow us to investigate these processes much better, for example at the COSC‐1 borehole in the central Scandinavian Caledonides. This study combines data from the COSC‐1 borehole with different seismic measurements to provide constraints on the spatial lithological and textural configuration of the Seve Nappe Complex. This is one of the few studies that shows that core‐log‐seismic integration in metamorphic rocks allows to identify the spatial distribution of major lithological units. Especially gamma ray logs in combination with density data are powerful tools to distinguish between mafic and felsic lithologies in log‐core correlation. Our results indicate that reflections along the borehole are primarily caused by compositional rather than textural changes. Reflections in the Seve Nappe Complex are not as distinct as in greater depths but continuous and several of them can be linked to magmatic intrusions, which have been metamorphically overprinted. Their setting indicates that the Seve Nappe Complex consists of the remnants of a volcanic continental margin. Our results suggest that ductile‐deformed middle crustal reflectivity is primarily a function of pre‐orogenic lithological variations which has to be considered when deciphering mountain building processes.
    Type: Article , PeerReviewed
    Format: other
    Format: other
    Format: other
    Format: text
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 6
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    Lithologierekonstruktion von submarinen Einheiten des Mauna Kea Vulkans mit bohrlochgeophysikalischen Messungen der magnetischen Suszeptibilität, HSDP Bohrung, Hawai’i (2010)
    Universitätsverlag Göttingen
    Details
    Publication Date: 2021-03-29
    Description: Als Teil des International Continental Drilling Projects (ICDP), wurde von März bis September 1999 im Rahmen des Hawai’i Scientific Drilling Projects (HSDP) die etwa 3109m tiefe HSDP-2 Bohrung in der Nähe von Hilo auf Big Island, Hawai’i niedergebracht. Die mit einem Durchmesser von 98mm (3.8500) durchgehend gekernte Bohrung, durchteuft sowohl die subaerischen Einheiten des Mauna Loa, als auch die darunter liegenden submarinen Laven des Mauna Kea. Ab etwa 1080m Teufe wurden die jüngsten, während der Entwicklung dieses Vulkans abgelagerten submarinen Laven erbohrt. Die Verteilung von Hyaloklastiten, Pillowlaven, massiver Intrusiva sowie sedimentärer Ablagerungen, wurde durch die lithologische Beschreibung des durchgehend geförderten Kernprofils von DePaolo et al. (1999) aufgenommen. Verschiedene Autoren, wie z.B. Bücker et al. (1999) oder Helm-Clark et al. (2004) haben bereits gezeigt, dass sich Messungen der natürlichen Gammastrahlung (GR), die üblicherweise sehr gut zur lithologischen Einteilung von Gesteinen herangezogen werden können, in vergleichbaren Bohrungen nur sehr bedingt zur primären Unterscheidung basaltischer Gesteinseinheiten eignen. Dies ist vor allem auf die sehr geringe Variation des K-, U- und Th-Gehalts der Basalte zurückzuführen. Daher wurden von der Operational Support Group (OSG) des GFZ-Potsdam im November 2002 bohrlochgeophysikalische Messungen in dem 98mm Bohrloch in einem Bereich von etwa 1830 bis 2615m durchgeführt. Diese wurden speziell zum Test einer Bohrlochsonde zur Messung der magnetischen Suszeptibilität (MS) im Rahmen des DFG-Projektes Wa 1015/4 angesetzt. Dazu wurde die MSdH-2 Sonde der OSG, hergestellt von der Fa. Antares GmbH (Stuhr, Germany) eingesetzt.
    Description: conference
    Keywords: 551 ; VAD 400 ; TOT 310 ; TQG 000 ; VEV 285 ; VBL 500 ; VKB 124 ; Vulkanische Förderprodukte {Geologie} ; Gesteinsmagnetismus {Geophysik} ; Geophysikalische Bohrlochmessungen ; Hawaii {Geologie} ; Geologische Bohrungen in einzelnen Regionen ; Basaltische Vulkanite {Petrologie} ; Mauna Kea ; Tiefbohrung ; Bohrlochgeophysik ; Magnetische Suszeptibilität ; Lava ; Basalt
    Language: German
    Type: anthologyArticle , publishedVersion
    Format: application/pdf
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    CITATION GEO-LEO
  • 7
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    Petrophysical characterization of the lacustrine sediment succession drilled in Lake El‘gygytgyn, Far East Russian Arctic (2013)
    COPERNICUS GESELLSCHAFT MBH
    In:  EPIC3Climate of the Past, COPERNICUS GESELLSCHAFT MBH, 9, pp. 1933-1947, ISSN: 1814-9324
    Details
    Publication Date: 2016-11-19
    Description: Seismic profiles of Far East Russian Lake El’gygytgyn which was formed by a meteorite impact some 3.6 million years ago show a stratified sediment succession that can be separated into Subunits Ia and Ib at approximately 167 m below lake floor (= ∼3.17 Ma). The former is well-stratified, while the latter is acoustically more massive. The sediments are intercalated with frequent mass movement deposits mainly in the proximal parts, while the distal part is almost free of such deposits at least in the upper part. In spring 2009, a long core drilled in the lake center within the framework of the International Continental Scientific Drilling Program (ICDP) penetrated the entire lacustrine sediment succession down to ~320 m below lake floor and about 200 m further into the meteorite-impact related bedrock. Downhole logging data down to 390 m below lake floor show that the bedrock and the lacustrine part of the core differ largely in their petrophysical characteristics. The contact between the bedrock and the lacustrine sediments is not abrupt, but rather transitional with a mixture of impact-altered bedrock clasts in a lacustrine matrix with varying percentages. Physical and chemical proxies measured on the cores can be used to divide the lacustrine part into five different clusters. These can be plotted in a redox-condition vs. input type diagram with total organic carbon content and magnetic susceptibility values indicating anoxic or oxic conditions and with the Si/Ti ratio representing more clastic or more biogenic input. Plotting the clusters in this diagram allows identifying clusters that represent glacial phases (Cluster I), super interglacials (Cluster II), and interglacial phases (Clusters III and IV).
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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    PAPER (OA)
  • 8
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    Interpretation dreikomponentiger Bohrlochmagnetik in der COSC2-Bohrung (2022)
    Details
    Publication Date: 2022-12-01
    Description: Das Ziel des COSC-2 (Collisonal Orogeny in the Scandinavian Caledonides) Projektes ist es, die Entstehungsprozesse der Skanden zu untersuchen. Hierfür sind Kenntnisse über die Deformationen / Faltungsprozesse von großer Wichtigkeit, die sich aus der Richtung der remanenten Magnetisierung ableiten lassen. Die teufenabhängigen Magnetisierungsvektoren lassen sich aus dreikomponetigen Bohrlochmagnetikdaten berechnen. Als Datengrundlage dienen Messungen, die mit einem Dipmeter in der COSC2-Bohrung in Järpen (Schweden) durchgeführt wurden. Es wurden 5 Messungen mit 1cm Messpunktabstand in verschiedenen Teufenbereichen zwischen 100m und 2250m Teufe aufgezeichnet. Anhand der in der Sonde verbauten Accelerometer und dem bekannten Verlauf der Bohrung konnten die Magnetfelddaten in das geographische Referenzsystem reorientiert werden. Die erreichte Genauigkeit beträgt 1,5° in der Deklination und 0,16° in der Inklination. Um die Magnetisierung der durchbohrten Gesteinseinheiten zu bestimmen wird an die reorientierten Magnetfelddaten ein Schichtmodell nach Bosum et al (1988) angepasst. Dieses Modell nähert die Schichten durch zentral durchbohrte Zylinder. Das Modell von Bosum geht von einem Zylinder aus, der senkrecht zu den Deckflächen zentral durchbohrt wird. In der COSC-2 Bohrung ist aber zum einen das Bohrloch geneigt, zum anderen weisen auch die durchbohrten Schichten eine Neigung auf. Aus diesem Grund erweitern wir das Bosum-Modell nach Ehmann (2016) für beliebige Schichtinklinationen. Die Schichtmächtigkeiten werden durch die Lithologie der Bohrung bestimmt, die aus den Bohrkernen abgeleitet wurde. Eine erste Analyse zeigt, dass in den oberen 1200m der Bohrung nur schwach magnetisierte Gesteine vorherrschen. Darunter folgen stärker magnetisierte-Schichten, die im Mittel eine Magnetisierung von 1A/m aufweisen. Im Bereich von 1590m bis 1850m befindet sich eine stark magnetisierte Sektion, die sich in vier Bereiche aufteilen lässt. Die Magnetisierung in dieser Sektion beträgt bis zu 5 A/m. In der stark magnetisierten Sektion können zwei Bereiche identifiziert werden, in denen die Inklination der Magnetisierungen von 40° auf bis zu 80° ansteigt. Die beiden Bereiche mit hoher Inklination weichen in ihrer Deklination von der mittleren Deklination der Sektion um +90° und -90° ab. Diese Variationen deuten auf Deformationen der Gesteinsschichten hin. Unterhalb dieser Sektion schließt sich eine Sektion mit Magnetisierungen von etwa 1 A/m und Inklinationen von etwa 15° an.
    Description: DFG, Fördernummer VI 836/5-1
    Description: poster
    Keywords: ddc:550
    Language: German
    Type: doc-type:conferenceObject
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    CITATION GEO-LEO
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