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7. Using ⁸⁷Sr/⁸⁶Sr Ratios to Date Fossil Methane Seep Deposits: Methodological Requirements and an Example from the Great Valley Group, California

Author

Kiel, Steffen, Hansen, Christian, Nitzsche, Kai Nils, Hansen, Bent T., Kiel, Steffen, Hansen, Christian, Nitzsche, Kai Nils, and Hansen, Bent T.

Abstract

Methane seep carbonates preserve information about the history of methane seepage and of the fauna inhabiting these ecosystems. For this information to be useful, a reliable determination of the carbonates’ stratigraphic ages is required, but this is not always available. Here we investigate the using strontium isotope stratigraphy to date fossil methane seep carbonates via detailed petrographic and geochemical investigation of the different carbonate phases in biostratigraphically well-dated seep carbonates of Paleozoic, Mesozoic, and Cenozoic age. The best results are obtained from banded, botryoidal rim cements from carbonate phases showing a weak or no cathodoluminescence signal, an oxygen isotope signature close to that of seawater, and the lowest Mn concentrations. We then applied the method to a presumably late Jurassic seep carbonate from the Great Valley Group in California. Strontium isotope ratios of the least diagenetically altered carbonate phases indicate a Tithonian (late Jurassic) age for this seep site, which is in conflict with a recent study that suggested the absence of Jurassic strata from the Great Valley Group.

Published
2022

11. The Erbisberg drilling 2011: Implications for the structure and postimpact evolution of the inner ring of the Ries impact crater

Author

Arp, Gernot, primary, Reimer, Andreas, additional, Simon, Klaus, additional, Sturm, Sebastian, additional, Wilk, Jakob, additional, Kruppa, Corina, additional, Hecht, Lutz, additional, Hansen, Bent T., additional, Pohl, Jean, additional, Reimold, Wolf Uwe, additional, Kenkmann, Thomas, additional, and Jung, Dietmar, additional

Published
2019
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16. Isotope Dating of the Potash and Rock Salt Deposit at Bamnet Narong, NE-Thailand

Author

Hansen, Bent T., Wemmer, Klaus, Eckhardt, Monique, Putthapiban, Prinya, and Assavapatchara, San

Subjects
Isotope Dating, Salt Deposits, Mid-Cretaceous, Asian Potash Mine, Thailand
Abstract

Bamnet Narong is located in northeastern Thailand (Chaiyaphum Province). It is the largest salt mine in the country and has been mined for decades. The landscape in this part of Thailand is characterised by a low plateau, which is called the Khorat Plateau. The plateau is divided into two basins by the Phu Phan Range, the Sakhon Nakhon Basin in the north and the Khorat Basin in the south. The analysed potashes and rock salts are deposited in the Maha Sarakham Formation, which represents the salt-bearing strata of the Khorat Basin. The stratigraphic age of this deposit has been debated since the late 1960’s. The assigned ages range from Mid-Cretaceous to Late Cretaceous and up to the Eocene. In this study different isotopic dating systems (Rb-Sr, Sr-Sr, K-Ar and K-Ca) were applied. The stratigraphic age for the time of deposition was confirmed to be Mid Cretaceous (Cenomanian). Furthermore, the homogeneity of the carnallites was investigated in order to trace a possible redistribution of rubidium., Open-Access-Publikationsfonds 2016

Published
2016

17. Isotope and REE Characterization of Groundwater Aquifers within the Aquifer Storage and Recovery Programme in Sukhothai (N.-Thailand)

Author

Hengsuwan, Manussawee, Yongprawat, Monthon, Simon, Klaus, and Hansen, Bent T.

Subjects
Sr-Isotope, Rare Earth Elements (REE), Aquifer Storage and Recovery (ASR), Thailand
Abstract

Aquifer Storage and Recovery (ASR) was a pilot project for solving flood and drought problem in the northern part of Chao Phraya River basin, Thailand. This part of Thailand always faces flooding in rainy season and drought during dry season every year. The overexploitation of groundwater during dry season leads to continuously decline of water level in this area. In this project, the excessive surface water during rainy season was stored by injection of this treated surface water through recharge wells into the underground aquifers. This would serve to raise the water level, which can be extracted for use during the dry season. To assess the efficiency of the ASR process some tracers are required. The aim of this study is to prove the suitability of natural tracers to follow up the artificial recharge process; emphasis will be placed on Strontium (Sr) isotopic composition. The results showed that the change in 87Sr/86Sr ratios could be observed during an artificial recharge due to the different isotopic fingerprint of surface water and groundwater. However, the flow direction of the injected water cannot be clearly interpreted because of the limited number of monitoring wells, small distance between each monitoring well and the short duration of injection., Open-Access-Publikationsfonds 2016

Published
2016

18. Are there two types of vredefort granophyre?

Author

Wannek, Dshamilja L. M., Reimold, Wolf Uwe, Thirlwall, Matthew, Hansen, Bent T., Schulz, Toni, Hoffmann, Michael, Zaag, Patrice T., Hauser, Natalia, and Siegert, Susann

Subjects
Institut für Erd- und Umweltwissenschaften
Published
2015

19. [Untitled]

Author

Hansen, Bent T.

Subjects
Palaeontology, FOS: Biological sciences, Zoology
Abstract

Frank Wiese, Mike Reich and Gernot Arp (Eds.) “Spongy, slimy, cosy & more ; 7-8

Published
2014
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26. Geochemische Klassifikation und Sm-Nd Isotopensystematik proterozoischer Metasedimente des Baltischen Schildes (Västervik Region, SESchweden)

Author

Fischer, Mario, Hansen, Bent T., and Kleinhanns, Ilka C.

Abstract

Die Västervik Region liegt an einer Haupt-Terran-Grenze im Baltischen Schild. Im NE schließen sich die Einheiten des Südsvecofennischen Vulkanitgürtels mit Altern >1,85Ga an, im SW folgen die Granitoide des Transskandinavischen Magmatitgürtles (TMZ) mit Altern, conference

Published
2006
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36. Using 87Sr/86Sr Ratios to Date Fossil Methane Seep Deposits: Methodological Requirements and an Example from the Great Valley Group, California.

Author

Kiel, Steffen, Hansen, Christian, Nitzsche, Kai N., and Hansen, Bent T.

Subjects
METHANE, CARBONATES, STRONTIUM, STRATIGRAPHIC geology, PETROLOGY, GEOCHEMISTRY
Abstract

Methane seep carbonates preserve information about the history of methane seepage and of the fauna inhabiting these ecosystems. For this information to be useful, a reliable determination of the carbonates' stratigraphic ages is required, but this is not always available. Here we investigate the using strontium isotope stratigraphy to date fossil methane seep carbonates via detailed petrographic and geochemical investigation of the different carbonate phases in biostratigraphically well-dated seep carbonates of Paleozoic, Mesozoic, and Cenozoic age. The best results are obtained from banded, botryoidal rim cements from carbonate phases showing a weak or no cathodoluminescence signal, an oxygen isotope signature close to that of seawater, and the lowest Mn concentrations. We then applied the method to a presumably late Jurassic seep carbonate from the Great Valley Group in California. Strontium isotope ratios of the least diagenetically altered carbonate phases indicate a Tithonian (late Jurassic) age for this seep site, which is in conflict with a recent study that suggested the absence of Jurassic strata from the Great Valley Group. [ABSTRACT FROM AUTHOR]

Published
2014
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45. <SUP>87</SUP>Sr/<SUP>86</SUP>Sr-Verhältnisse als Tracer für geochemische Prozesse in einem Lockergesteinsaquifer (Liebenau, NW-Deutschland)

Author

Wiegand, Bettina, Dietzel, Martin, Bielert, Ulrich, Groth, Peter, and Hansen, Bent T.

Abstract

Grundwässer aus den quartären Lockersedimenten im Einzugsgebiet des Wasserwerkes Liebenau II (NW-Deutschland) sind durch heterogene Verteilungen der gelösten Inhaltsstoffe charakterisiert. Zur Bestimmung der Herkunft der Lösungskomponenten und zur Ermittlung von Grundwasserfließwegen wurden Sr-Isotopenuntersuchungen an Grundwässern, Niederschlagswässern und Sedimentproben durchgeführt. Die 87Sr/86Sr-Verhältnisse der Grundwässer liegen im Bereich von 0.708 bis 0.719 und ermöglichen eine Unterscheidung von vier Grundwasserhorizonten. Unterschiede in den 87Sr/86Sr-Verhältnissen resultieren aus verschiedenen Quellen des gelösten Strontiums im Grundwasser. Diese sind geprägt durch die Mineralverwitterung, die Niederschläge und anthropogene Einträge. Für den oberflächennahen Grundwasserbereich sind Einflüsse aus den Niederschlägen und vermutlich aus der landwirtschaftlichen Düngung durch niedrige 87Sr/86Sr-Verhältnisse zwischen 0.710 und 0.713 indiziert. Mit zunehmender Tiefe dominieren Verwitterungsprozesse die Grundwasserchemie. Über das 87Sr/86Sr-Verhältnis kann zwischen Silikat- und Karbonatauflösung unterschieden werden. Im mittleren Grundwasserhorizont bestätigen hohe 87Sr/86Sr-Verhältnisse zwischen 0.713 und 0.719 und Sättigungsindices < –3.5 für Calcit den Einfluss verwitternder Silikate. Niedrige 87

Published
2001
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47. Cenozoic Methane-Seep Faunas of the Caribbean Region

Author

Kiel, Steffen and Hansen, Bent T.

Subjects
14. Life underwater
Abstract

We report new examples of Cenozoic cold-seep communities from Colombia, Cuba, the Dominican Republic, Trinidad, and Venezuela, and attempt to improve the stratigraphic dating of Cenozoic Caribbean seep communities using strontium isotope stratigraphy. Two seep faunas are distinguished in Barbados: the late Eocene mudstone-hosted 'Joes River fauna' consists mainly of large lucinid bivalves and tall abyssochrysoid gastropods, and the early Miocene carbonate-hosted 'Bath Cliffs fauna' containing the vesicomyid Pleurophopsis, the mytilid Bathymodiolus and small gastropods. Two new Oligocene seep communities from the Sinú River basin in Colombia consist of lucinid bivalves including Elongatolucina, thyasirid and solemyid bivalves, and Pleurophopsis. A new early Miocene seep community from Cuba includes Pleurophopsis and the large lucinid Meganodontia. Strontium isotope stratigraphy suggests an Eocene age for the Cuban Elmira asphalt mine seep community, making it the oldest in the Caribbean region. A new basal Pliocene seep fauna from the Dominican Republic is characterized by the large lucinid Anodontia (Pegophysema). In Trinidad we distinguish two types of seep faunas: the mudstone-hosted Godineau River fauna consisting mainly of lucinid bivalves, and the limestone-hosted Freeman's Bay fauna consisting chiefly of Pleurophopsis, Bathymodiolus, and small gastropods; they are all dated as late Miocene. Four new seep communities of Oligocene to Miocene age are reported from Venezuela. They consist mainly of large globular lucinid bivalves including Meganodontia, and moderately sized vesicomyid bivalves. After the late Miocene many large and typical 'Cenozoic' lucinid genera disappeared from the Caribbean seeps and are today known only from the central Indo-Pacific Ocean. We speculate that the increasingly oligotrophic conditions in the Caribbean Sea after the closure of the Isthmus of Panama in the Pliocene may have been unfavorable for such large lucinids because they are only facultative chemosymbiotic and need to derive a significant proportion of their nutrition from suspended organic matter., Open-Access Publikationsfonds 2015

48. Isotope and REE Characterization of Groundwater Aquifers within the Aquifer Storage and Recovery Programme in Sukhothai (N.-Thailand)

Author

Hengsuwan, Manussawee, Yongprawat, Monthon, Simon, Klaus, and Hansen, Bent T.

Subjects
13. Climate action, 6. Clean water
Abstract

Aquifer Storage and Recovery (ASR) was a pilot project for solving flood and drought problem in the northern part of Chao Phraya River basin, Thailand. This part of Thailand always faces flooding in rainy season and drought during dry season every year. The overexploitation of groundwater during dry season leads to continuously decline of water level in this area. In this project, the excessive surface water during rainy season was stored by injection of this treated surface water through recharge wells into the underground aquifers. This would serve to raise the water level, which can be extracted for use during the dry season. To assess the efficiency of the ASR process some tracers are required. The aim of this study is to prove the suitability of natural tracers to follow up the artificial recharge process; emphasis will be placed on Strontium (Sr) isotopic composition. The results showed that the change in 87Sr/86Sr ratios could be observed during an artificial recharge due to the different isotopic fingerprint of surface water and groundwater. However, the flow direction of the injected water cannot be clearly interpreted because of the limited number of monitoring wells, small distance between each monitoring well and the short duration of injection., Open-Access-Publikationsfonds 2016

50. Chemical and ecological evolution of the Miocene Ries impact crater lake, Germany: A reinterpretation based on the Enkingen (SUBO 18) drill core.

Author

Arp, Gernot, Blumenberg, Martin, Hansen, Bent T., Jung, Dietmar, Kolepka, Claudia, Lenz, Olaf, Nolte, Nicole, Poschlod, Klaus, Reimer, Andreas, and Thiel, Volker

Subjects
*RIVERS, *LAKES, *DRILLING & boring, *CRATERING, *GEOMORPHOLOGY, *IMPACT craters
Abstract

Scientific drilling conducted at the inner slope of the Miocene central Ries impact crater recovered a partial section of crater lake sediments. Four sequences were recovered, composed of suevite-derived sandstones, thin lignite seams, bituminous shales, and marlstones to claystones. These flooding-evaporation sequences reflect the impact of short-term climatic fluctuations on a hydrologically closed basin. The superimposed trend from sequences rich in bituminous shales in the lower parts of the section to sequences dominated by organic-poor claystones and intercalated lignites in the upper parts of the section resembles that of the 300-m-thick central crater basin succession, which has previously been considered to reflect a climate-controlled development from an alkaline saline lake to a freshwater lake with temporary coal swamps. In the sediment core of Enkingen, however, the change from bituminous shales to organic-poor claystones with intercalated lignites is associated with a general increase in salinity, as indicated by (1) palynomorphs, (2) increase in δ13C of the lipid biomarker archaeol (bis-O-phytanylglycerol), and (3) the occurrence of 13C-enriched C20/C25-archaeol (O-phytanyl-O-sesterterpanylglycerol) specific to halophilic Archaea. In addition, the unidirectional trend in 87Sr/86Sr of carbonates, declining from ratios of Variscan basement rocks toward marine ratios, indicates a change from (1) weathering of crystalline rocks and suevite to (2) ejected Jurassic sediments (Bunte Breccia) in the catchment area as the major source of ion influx to the lake. From that trend, a change in lake water composition and a general increase in ion concentrations are inferred. These new results can be applied to a reassessment of major parts of the lacustrine succession of the Ries crater. We use these data to propose a new hypothetical model for the chemical and ecological evolution of the Ries crater lake: (1) After the establishment of a stratified brackish eutrophic soda lake due to silicate weathering and evaporation, the increasing influx of waters from the Bunte Breccia carbonate and authigenic silicate precipitation led to a mesotrophic halite lake with marine-like ion ratios and concentrations. (2) Further increase in ions, among them Mg2+ and Sr2+, resulted in hypersaline conditions with gypsum precipitation, low primary production, and phreatic Sr-rich dolomitization in marginal carbonates. (3) The final, sudden change to oligotrophic freshwater conditions is explained by the formation of an outlet late in the lake history. We conclude that the chemical and ecological evolution of the Ries lake therefore appears to have been mainly controlled by the weathering history of the catchment area, with climate fluctuations causing superimposed cycles. Similarly, changes in terrestrial palynomorph associations may at least partly reflect a change in soil types in the catchment area, from fertile, moist soils on suevite to dry karst soils and soils on Bunte Breccia. These interpretations imply that the initial suevite blanket of the Ries crater was much more continuous and widespread than previously assumed. [ABSTRACT FROM AUTHOR]

Published
2013
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