Seismic reflection data from the Upper Rhine Graben (URG) show a series of synclines along the linear eastern boundary faults from north of Karlsruhe to the Jura Mountains. Similar structures do not characterize the northern segment of the graben. The synclinal shape is portrayed by inversion related to transpression on the linear boundary faults, coupled with the conserved easterly dip of the sediments farther inside the tilted hanging block. The onset of transpression preceded the known early Burdigalian unconformity but was also an early Miocene event. It suggests that the regional compression axis (σ1) in early Miocene had a trend between 315° and 0°. The continuous transtension in the northern segment suggests that at no time during the history of the URG was the regional σ1 horizontal with a NE‐SW trend. The lack of transpressional structures in the younger Plio‐Pleistocene sediments along the entire eastern boundary of the URG suggests a late change in the regional stress field. The main eastern boundary faults and synclines north and south of Baden‐Baden are all continuous and have the same trend. Kinematically, they form a single graben segment and respond to the regional stress in the same way.
Zusammenfassung81 Kr (T1/2 229.000 a) ist ein idealer Datierungstracer für alte Tiefengrundwässer. Die Oberjura-Formation im tiefen Teil des Molassebeckens stellt ein herausragendes Georeservoir für thermale Tiefenwässer (bis 140°C) dar. Über die genutzten Thermalwässer mit zumeist kaltzeitlicher Bildungscharakteristik (Na-HCO3-Cl-Typ) ist jedoch im Hinblick auf die Neubildungsprozesse, Herkunftsgebiete und Fließdynamik wenig bekannt. Für die Interpretation der Genese und Entwicklung (Ionen-und Isotopenaustausch, Gasflüsse, etc.) fehlen bislang verlässliche Altersinformationen. Erstmals wurden nun neun thermale Tiefenwässer erfolgreich durch 81 Kr/ 85 Kr-ATTA-Untersuchungen datiert. Die abgeleiteten Altersinformationen zeigen im westlichen und zentralen Molassebecken vorherrschend eine Bildung während der letzten Kaltzeit (Würm-Glazial), die sehr gut zur subglazialen Bildungshypothese über alpennahe, sehr mächtige Deckschichten hinweg passt. Im Ostteil des Molassebeckens weisen die Tiefenwässer hingegen einheitlich deutlich höhere Alterscharakteristiken (Günz/Mindel Interglazial) bzw. ein langsameres Strömungssystem auf, das allenfalls durch geringe Neubildungsanteile aus den jüngeren alpinen Vergletscherungen beeinflusst ist. 81 Kr/ 85 Kr-Dating of thermal groundwaters in the Upper Jurassic (Molasse Basin)Abstract 81 Kr (half-life 229,000 years) is an ideal tracer for old groundwater. The Upper Jurassic rock in the deep Molasse Basin is an outstanding geothermal groundwater reservoir (with temperatures up to 140°C). However, due to the complex groundwater evolution (ion and isotope exchange, gas flux, etc.), comprehensive hydrogeological studies completed to date, including 14 C-DIC and He isotopes, could not resolve the recharge dynamics and residence times. Nine geothermal wells were therefore sampled for 81 Kr/ 85 Kr employing the laser-based atom trap tracer analysis technique (ATTA). In the western and central basin, the results reveal predominant groundwater recharge during the last glacial period with one sample influenced by infiltration during the earlier glacial period. Recharge signatures and 81 Kr-model-ages fit very well to subglacial recharge with cross-formational flow through the sedimentary cover (600 to >3000 m deep). In the eastern basin, the results point to the Cromerian complex, indicating a slower flow system with less influence from recharge during glacial periods.
Der Erdwärmesonden‐Schadensfall Staufen i. Br. zeigt in deutlicher Weise Gefährdungen auf, die bei stockwerksübergreifenden Erdwärmesonden‐Bohrungen mit Potenzialunterschieden der angetroffenen Grundwasserstockwerke auftreten können. Durch Grundwasserströmung kam es im Ringraum der Erdwärmesonden‐Bohrungen zu einem Austrag von Abdichtungsmaterial. Dies führte in einer oder mehreren Ringraumabdichtungen zum Misslingen der erforderlichen Stockwerkstrennung. Wasserzutritte in ehemals trockene, quell‐ und schwellfähige Gebirgsabschnitte verursachten das “Gipskeuperquellen”. Diese Wasserzutritte konnten durch schadensbegrenzende Maßnahmen (Nachverpressung der Erdwärmesonden, Dauerabsenkung des Druckwasserspiegels) unterbunden werden. In quellfähiges Gebirge eingedrungenes Wasser lässt sich jedoch weder mit hydraulischen noch anderen Maßnahmen rückgewinnen. Von daher werden die Geländehebungen so lange andauern, bis das eingedrungene Wasser durch den Quell‐/Schwellprozess restlos aufgezehrt ist. Die eingeleiteten schadensbegrenzenden Maßnahmen zeigten Erfolg. Dadurch konnten die maximalen Hebungsgeschwindigkeiten von anfangs 11 mm/Monat auf derzeit ca. 3, 5 mm/Monat reduziert werden. Die Hebungsmessungen seit Herbst 2012 deuten darauf hin, dass die bisher zu beobachtende lineare Prozessverlangsamung nicht unverändert anhält. Durch eine Modellierung wurde deutlich, dass die Pumpmaßnahme zur Vermeidung von erneutem Auftrieb und weiteren Quellvorgängen fortgeführt werden muss.Investigation and remediation strategies for the damaging event caused by failed borehole heat exchanger drillings in Staufen i. Br. The effects of failed borehole heat exchanger drillings in the German town Staufen i. Br. show distinctly the hazards, which can arise from borehole heat exchanger drillings spanning multi groundwater storeys with potential difference of the penetrated groundwater storeys. Groundwater flow induced the discharge of annular sealing in the annulus of the borehole heat exchanger drilling. Under the encountered hydrological boundary conditions, this caused the failure of the required separation of the groundwater storeys in one or more annular sealing. Water influx in previously dry, swellable geological layers caused the so‐called “Gipskeuperquellen” (swelling of the gypsum‐containing Upper Triassic Grabfeld formation). This water influx could be suppressed by damage‐limiting measures (post‐grouting of the borehole heat exchanger, permanent groundwater lowering). It is not possible to reclaim water that ingressed into swellable geological layers neither by hydraulic nor by other measures. Thus, the ground heave will continue until the ingressed water is completely exhausted by the swelling process. The initiated damage‐limiting measures succeed. As a result, the maximum heave rate has decelerated from 11 mm/month at the beginning to currently approximately 3.5 mm/month. Since autumn 2012, the ground heave measurements indicate, that the linear deceleration of the process observed until now does not continue unchanged. By modelling it became clear, that the groundwater pumping has to be continued to avoid more uplift and further swell processes. Experiences from the case Staufen i. Br. show impressively, that a thorough pre‐investigation immediately followed by the initiation of defensive/control measures are absolutely necessary in case of damaging events caused by failed borehole heat exchanger drillings.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.