COSC-2 – drilling the basal décollement and underlying margin of palaeocontinent Baltica in the Paleozoic Caledonide Orogen of Scandinavia

Lorenz, Henning; Rosberg, Jan-Erik; Juhlin, Christopher; Klonowska, Iwona; Lescoutre, Rodolphe; Westmeijer, George; Almqvist, Bjarne; Anderson, Mark; Bertilsson, Stefan; Dopson, Mark; Kallmeyer, Jens; Kück, Jochem; Lehnert, Oliver; Menegon, Luca; Pascal, Christophe; Rejkjær, Simon

doi:10.5194/sd-30-43-2022

Cited by 6 publications

(7 citation statements)

References 22 publications

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“…1). However, the effect of the lithology on the biomass was not feasible to predict prior to field sampling as the expected lithology from the siting differed from the drilled lithology (Lorenz et al, 2022).…”

Section: Rock Core Samplesmentioning

confidence: 99%

“…The sampling procedure and contamination control were described in detail in Lorenz et al (2022). Briefly, rock core samples with core recovery to characterize potential contaminants introduced during the drilling operation.…”

Section: Field Samplingmentioning

confidence: 99%

“…Integration of subsurface microbiology into the workings of the International Continental Scientific Drilling Program (ICDP) defined several questions (Mangelsdorf and Kallmeyer, 2010) including understanding subsurface biodiversity; interactions between the deep biosphere and geosphere; and deep life as an analogue for potential life on other planets. Following this workshop, two subsurface scientific drilling projects termed Collisional Orogeny in the Scandinavian Caledonides (COSC-1 and COSC-2), located in western central Sweden, were performed in 2014 and 2020 (Lorenz et al, 2015(Lorenz et al, , 2022. Here, microorganisms present in a hard rock environment were studied down to 2250 m depth by sampling drill cores and groundwater-bearing fractures during the COSC-2 drilling project.…”

Section: Introductionmentioning

confidence: 99%

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Continental scientific drilling and microbiology: (extremely) low biomass in crystalline bedrock of central Sweden

Westmeijer,

Escudero,

Bergin

et al. 2023

Preprint

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Abstract. Scientific drilling expeditions offer a unique opportunity to characterize the microbial communities in the subsurface that have been long-term isolated from the surface. With subsurface microbial biomass being low in general, biological contamination from the drilling fluid, sample processing, or molecular work is a major concern. To address this, characterization of the contaminant populations in the drilling fluid and negative extraction controls are essential for assessing and evaluating such sequencing data. Here, crystalline rock cores down to 2250 m depth, groundwater-bearing fractures, and the drilling fluid were sampled for DNA to characterize the microbial communities using a broad genomic approach. However, even after removing potential contaminant populations present in the drilling fluid, notorious contaminants were abundant and mainly affiliated with the bacterial order Burkholderiales. These contaminant microorganisms likely originated from the reagents used for isolating and amplifying DNA despite stringent quality standards during the molecular work. The detection of strictly anaerobic sulfate reducers such as Candidatus Desulforudis audaxviator suggested the presence of autochthonous deep biosphere taxa in the sequenced libraries, yet these clades represented only a minor fraction of the sequence counts (< 0.1 %), hindering further ecological interpretations. The described methods and findings emphasize the importance of sequencing extraction controls and can support experimental design for future microbiological studies in conjunction with continental drilling operations.

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Section: Rock Core Samplesmentioning

confidence: 99%

Section: Field Samplingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Continental scientific drilling and microbiology: (extremely) low biomass in crystalline bedrock of central Sweden

Westmeijer,

Escudero,

Bergin

et al. 2023

Preprint

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“…However, seismic reflection imaging across the central Scandinavian Caledonides shows a pervasively reflective upper crust, down to at least 15 km present depth, characterized by sub‐horizontal and west‐dipping reflectors (Hurich et al, 1989; Juhlin et al, 2016; Juhojuntti et al, 2001; Palm et al, 1991). These reflectors are intriguing because they occur under the shale décollement and deep drilling indicated that they are likely to originate from mafic intrusions (Lorenz et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

Brittle basement deformation during the Caledonian Orogeny observed by K‐Ar geochronology of illite‐bearing fault gouge in west‐central Sweden

et al. 2023

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This study presents K‐Ar ages of illite‐bearing fault gouges in crystalline basement in central‐western Sweden. Samples were taken from two faults that localized brittle deformation marginal to and within mafic dikes that intruded Paleoproterozoic granitoids. K‐Ar ages from 10 separated grain fractions span from 823 to 392 Ma. Older ages obtained (823–477 Ma) were influenced by a mixture of illite and K‐feldspar; the latter likely formed during a hydrothermal event prior to faulting. The remaining ages (442.1 ± 9.7 to 391.7 ± 6.1 Ma) were obtained from fractions from both faults hosting only authigenic illite and show that illite crystallized during the Scandian phase of the Caledonian orogeny. These results indicate that previously presumed autochthonous Caledonian basement was involved in continental contraction and subsequent collapse of the Caledonian orogen, influencing both the mode and depth of penetration of deformation into Baltica.

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“…Collisional Orogeny in the Scandinavian Caledonides, a scientific drilling project conducted in 2020, located in central Sweden [51].…”

Section: Syntrophymentioning

confidence: 99%

Microbial life deep underground: From anaerobic cultures to reconstructed genomes

Westmeijer

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The deep biosphere refers to the vast ecosystem of life beneath the Earth’s surface, residing in the fractured bedrock and pores of rocks, largely isolated from solar energy. These fractures enclose an important reservoir of groundwater that contains microorganisms active in processes such as the uptake of inorganic carbon, sulfur cycling, or the degradation of organic matter. However, there is still much knowledge to be gained on the diversity and function of these subsurface microorganisms, and how the surface influences subsurface life. In this work, I explored interactions among subsurface microorganisms, studied subsurface microbial diversity in the light of surface recharge, and characterized microbial populations residing in biofilms. Potential interactions among microorganisms were explored with anaerobic cultures using groundwaters from the Äspö Hard Rock Laboratory. By removal of larger cells (> 0.45 𝜇m in diameter), an inoculum enriched in ultra-small bacteria (nanobacteria) was obtained. Despite the presence of various sources of energy and nutrients, these nanobacteria did not grow over prolonged incubation times up to four months. Reconstructed genomes confirmed this group of bacteria to have a low metabolic potential, indicative of a symbiotic lifestyle. Characterization of microbial communities in subsurface groundwaters and overlying environments on Äspö island revealed that a substantial proportion of the subsurface community was also detected in soil-hosted groundwaters. Considering the unidirectional water flow, this showed that part of the subsurface diversity between 70 and 460 m depth could originate from surface recharge, especially for the shallower groundwaters. In contrast to the high microbial diversity observed in Äspö groundwaters, characterization of a fracture fluid at 975 m depth in central Sweden revealed a microbial community dominated by a single population, adapted to the energy-limited conditions in the deep subsurface, namely the bacterium Candidatus Desulforudis audaxviator. Furthermore, the activity (based on RNA transcripts) of attached microbial populations was measured using flow-cells that facilitated biofilm formation. An elevated number of genes involved in the transition from a planktonic to an attached lifestyle was observed. Interestingly, comparing the microbial activity in the biofilm to the planktonic community revealed Thiobacillus denitrificans to have a principal role in the biofilm formation. Combined, these findings help understand the magnitude of microbial diversity in the continental subsurface as well as how these microorganisms are adapted to cope with the energy limitations in this subsurface ecosystem.

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COSC-2 – drilling the basal décollement and underlying margin of palaeocontinent Baltica in the Paleozoic Caledonide Orogen of Scandinavia

Cited by 6 publications

References 22 publications

Continental scientific drilling and microbiology: (extremely) low biomass in crystalline bedrock of central Sweden

Continental scientific drilling and microbiology: (extremely) low biomass in crystalline bedrock of central Sweden

Brittle basement deformation during the Caledonian Orogeny observed by K‐Ar geochronology of illite‐bearing fault gouge in west‐central Sweden

Microbial life deep underground: From anaerobic cultures to reconstructed genomes

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