A Study of Impact Fracturing and Electric Resistivity Related to the Lockne Impact Structure, Sweden

Bäckström, Ann

doi:10.1007/3-540-27548-7_15

Cited by 3 publications

(8 citation statements)

References 11 publications

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“…Laboratory experiments, field data and numerical modeling confirmed the relationship between key parameters affecting ER and squeezing (Ammar & Kamal, 2018). For example, the pore fluid condition (Bhatt & Jain, 2014), fluid pressure, weathering, joint characteristics and faults properties (Bäckström, 2004;László, 2011) as well as the porosity and lithology of rock matrix (Aceh, 2019) can also influence ER, similar to tunnel squeezing.…”

Section: Introductionmentioning

confidence: 79%

Prediction of tunnel squeezing in soft sedimentary rocks by geoelectrical data

et al. 2023

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Squeezing is time-dependent deformations of tunnels which can cause technical difficulties and financial consequences. This study employs geo-electrical resistivity data to predict squeezing intensity along Beheshtabad tunnel in the Sanandaj-Sirjan formation located in Northwest Iran. For comparison analysis, a combination of semi-empirical approach and numerical modeling was used to evaluate tunnel squeezing at design stage. The squeezing intensity obtained for Beheshtabad tunnel was then compared with the instability observations along Golab tunnel excavated in sedimentary rocks of the same formation. We developed a relationship between electrical resistivity and strains, and provided a new strain-based squeezing classification system. The calibrated electrical data are the most accurate method to predict tunnel squeezing as compared to the conventional approach. The results show that rock type, joint properties and water saturation have noticeable impacts on squeezing.

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Section: Introductionmentioning

confidence: 79%

Prediction of tunnel squeezing in soft sedimentary rocks by geoelectrical data

et al. 2023

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“…In a study by Bäckström (2005), it is observed that the non‐brecciated crystalline rock has a resistivity >10,000 Ωm. It is also seen that the resistivity of brecciated crystalline rock ranges between 300 and >10,000 Ωm (Figure 6).…”

Section: Resultsmentioning

confidence: 99%

“…The fracture frequencies were measured over a set 1 m 2 surface. Some of the results were published in Bäckström (2005), but other previously unpublished data. In connection with the field work that led to the Bäckström (2005) article additional resistivity measurements were performed in locations outside two profiles described by Bäckström (2005).…”

Section: Vlf Resistivity and Fracture Frequencymentioning

confidence: 99%

“…A tree diagram showing the distribution of resistivity values in the crystalline ejecta split into four groups depending on the area around the crater. The dashed horizontal lines show resistivity values given in the pseudo profiles.The data originate fromBäckström (2005). The resistivity measurements were made with a Very Low Frequency EM 16R instrument from Geonic equipped with an additional 10 m-long antenna that is laid out over the ground.…”

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confidence: 99%

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The Proximal Ejecta Around the Marine‐Target Lockne Impact Structure, Sweden

Sturkell,

Ormö,

Hegardt

et al. 2023

JGR Planets

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Except for some impact structures on low-gravity cosmic bodies, essentially all fresh impact structures are surrounded by ejecta from the crater interior (Melosh, 1989, p. 89). The geological activity on Earth does not favor the preservation of ejecta deposits. The preservation varies considerably. The best-preserved exposed ejecta deposits according to Osinski et al. (2011) are the Mauritanian Tenoumer structure (1.9 km diameter, 0.0214 Ma) and Pingualuit (New Quebec) in Canada (3.4 km diameter, 1.4 Ma). In Table 1 in Osinski et al. (2011), nine additional structures with preserved ejecta deposits are listed. Several other structures are completely buried and can only be observed with drilling and for these, the precise extent of the ejecta deposits is difficult to estimate. Also, there are ejecta deposits without a known impact structure. In this aspect, the Lockne structure offers a unique opportunity to study and explore the proximal ejecta (the ejecta blanket) around a marine target impact. The preservation of the crater and its proximal ejecta is favored by a combination of a relatively young age and large magnitude of the event (making a large impact crater), as well as that it occurred

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“…The impact structure consists of impact breccia and resurge deposits (Sturkell et al, 2013). The fracture frequency of the breccia is estimated to be 25 times higher than in the surrounding crystalline bedrock, and the porosity is 2-10 times higher (Bäckström, 2005). These characteristics, together with the karstified carbonate bedrock, facilitate groundwater flow in the catchment area (Dahlqvist et al, 2018).…”

Section: Study Sitementioning

confidence: 99%

A modern snapshot of the isotopic composition of lacustrine biogenic carbonates – records of seasonal water temperature variability

et al. 2022

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Abstract. Carbonate shells and encrustations from lacustrine organisms provide proxy records of past environmental and climatic changes. The carbon isotopic composition (δ13C) of such carbonates depends on the δ13C of dissolved inorganic carbon (DIC). Their oxygen isotopic composition (δ18O) is controlled by the δ18O of the lake water and by water temperature during carbonate precipitation. Lake water δ18O, in turn, reflects the δ18O of atmospheric precipitation in the catchment area, water residence time and mixing, and evaporation. A paleoclimatic interpretation of carbonate isotope records requires a site-specific calibration based on an understanding of these local conditions. For this study, samples of different biogenic carbonate components and water were collected in the littoral zone of Lake Locknesjön, central Sweden (62.99∘ N, 14.85∘ E, 328 ma.s.l.) along a water depth gradient from 1 to 8 m. Carbonate samples of living organisms and subfossil remains in surface sediments were taken from the calcifying alga Chara hispida, from bivalve mollusks of the genus Pisidium, and from adult and juvenile instars of two ostracod species, Candona candida and Candona neglecta. Our results show that neither the isotopic composition of carbonates nor the δ18O of water vary significantly with water depth, indicating a well-mixed epilimnion. The mean δ13C of Chara hispida encrustations is 4 ‰ higher than the other carbonates. This is due to fractionation related to photosynthesis, which preferentially incorporates 12C into the organic matter and increases the δ13C of the encrustations. A small effect of photosynthetic 13C enrichment in DIC is seen in contemporaneously formed valves of juvenile ostracods. The largest differences in the mean carbonate δ18O between species are caused by vital offsets, i.e., the species-specific deviations from the δ18O of inorganic carbonate which would have been precipitated in isotopic equilibrium with the water. After subtraction of these offsets, the remaining differences in the mean carbonate δ18O between species can mainly be attributed to seasonal water temperature changes. The lowest δ18O values are observed in Chara hispida encrustations, which form during the summer months when photosynthesis is most intense. Adult ostracods, which calcify their valves during the cold season, display the highest δ18O values. The seasonal and interannual variability in lake water δ18O is small (∼ 0.5 ‰) due to the long water residence time in the lake. Seasonal changes in the temperature-dependent fractionation are therefore the dominant cause of carbonate δ18O differences between species when vital offsets are corrected. Temperature reconstructions based on paleotemperature equations for equilibrium carbonate precipitation using the mean δ18O of each species and the mean δ18O of lake water are well in agreement with the observed seasonal water temperature range. The high carbonate δ18O variability of samples within a species, on the other hand, leads to a large scatter in the reconstructed temperatures based on individual samples. This implies that care must be taken to obtain a representative sample size for paleotemperature reconstructions.

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A Study of Impact Fracturing and Electric Resistivity Related to the Lockne Impact Structure, Sweden

Cited by 3 publications

References 11 publications

Prediction of tunnel squeezing in soft sedimentary rocks by geoelectrical data

Prediction of tunnel squeezing in soft sedimentary rocks by geoelectrical data

The Proximal Ejecta Around the Marine‐Target Lockne Impact Structure, Sweden

A modern snapshot of the isotopic composition of lacustrine biogenic carbonates – records of seasonal water temperature variability

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