Ultra-slow cratonic denudation in Finland since 1.5 Ga indicated by tiered unconformities and impact structures

Hall, Adrian M.; Putkinen, Niko; Hietala, Satu; Lindsberg, Elina; Holma, Marko

doi:10.1016/j.precamres.2020.106000

Cited by 11 publications

(13 citation statements)

References 138 publications

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“…Keurusselkä is a structure that has eroded below its original impact breccia layer (Hietala & Moilanen, 2004a, 2004b, 2007; Raiskila et al., 2013). According to pre‐Sveconorwegian erosion depth indicators, a postimpact erosion depth is 0.80–1.23 km in a 14 km Keurusselkä structure (Hall et al., 2020; Hietala et al., 2021). The postimpact erosion depth is based on the empirical relationship between the original diameter and original depth since the impact (Hall et al., 2020).…”

Section: Discussionmentioning

confidence: 99%

“…The interpreted topographic data and shatter cone distribution were used to determine the structure's size and compared to the earlier estimations by Osinski and Ferri ere (2016) with erosion estimates from Hall et al (2020). In a study of Haughton and Tunnunik's impact structure, Osinski and Ferri ere (2016) calculated the Keurusselk€ a structure as 36 km in diameter.…”

Section: Interpretation Of the Structure's Sizementioning

confidence: 99%

“…According to pre-Sveconorwegian erosion depth indicators, a postimpact erosion depth is 0.80-1.23 km in a 14 km Keurusselk€ a structure (Hall et al, 2020;Hietala et al, 2021). The postimpact erosion depth is based on the empirical relationship between the original diameter and original depth since the impact (Hall et al, 2020). However, in Keurusselk€ a, the residual gravity minimum east of the shatter cone area hints at a deeper erosion level.…”

Section: Interpretation Of the Structure's Sizementioning

confidence: 99%

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Keurusselkä impact structure, Finland—Overview, new observations, and renewed interpretation of the size

Hietala

Moilanen

Plado

2022

Meteorit & Planetary Scien

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The Keurusselk€ a structure is one of Finland's 12 meteorite impact structuresone of the world's oldest (1150 AE 10 Ma) and the largest of its kind in Finland. Findings of numerous well-formed shatter cones in a wide area have helped define and prove Keurusselk€ a's impact origin. Keurusselk€ a is deeply eroded, making estimating its size challenging. Thus, various size ranges are based on the distribution of shatter cones. This study provides an overview of the earlier published studies in light of the unpublished data resulting from 2003 to 2019 field surveys. Two shatter cone outcrops 15 km from each other were sampled during a field survey in 2019. Thin section samples from these sites were studied with a polarizing microscope, and shock metamorphic features were identified and measured with the universal stage. We also compared topographic and bathymetric Lidar (light detection and ranging) data with the existing geophysical data and shatter cone occurrences. In situ outcrops-Metsom€ aki 9.6 km toward the W and Martinniemi 5.7 km toward SE from the crater's center-delimit the maximum radius of shatter cones found so far. Studies resulted in planar fractures parallel to (0001) in Metsom€ aki shatter cones. We determine the size of 37.5 km as the apparent diameter of the Keurusselk€ a impact structure, whereas the 25 km in diameter semicircular feature represents faulted rim structures. 2063

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Section: Discussionmentioning

confidence: 99%

Section: Interpretation Of the Structure's Sizementioning

confidence: 99%

Section: Interpretation Of the Structure's Sizementioning

confidence: 99%

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Keurusselkä impact structure, Finland—Overview, new observations, and renewed interpretation of the size

Hietala

Moilanen

Plado

2022

Meteorit & Planetary Scien

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“…In a recent publication, Hall et al. (2020) estimated that the long‐term erosion rate is 1.08 m Myr −1 , and the post‐impact erosion depth is 150 m at maximum.…”

Section: Introductionmentioning

confidence: 99%

Petrographic studies and mineralogical characterization of the Dellen impactites

Hietala

Henkel

Plado

2023

Meteorit & Planetary Scien

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The impact origin of the Early Cretaceous (140.82 ± 0.51 Ma) 20‐km diameter Dellen structure was proven in the late 60s based on the discovery of planar deformation features (PDFs) in quartz grains. Although decades have passed, impactites found from the crater have not received much attention. Thus, this study provides a detailed petrological and mineralogical description of impactites from Dellen. Impactites were classified based on mineralogical observations using the latest recommendations of nomenclature. The studied samples include impact melt rocks (clast rich, clast poor, and clast free), suevitic impact breccias, shocked and unshocked granite, and a shatter cone. Altogether, 16 samples with different lithologies were studied using a polarization microscope. Selected samples were studied with an energy dispersive spectroscopy detector attached to the scanning electron microscopy. PDFs were indexed using a four‐axis universal stage from seven samples. Selected samples for PDF studies consisted of clast‐rich impact melt rocks (DEL10, DEL13, D99), suevitic impact breccias (DEL14, DEL16, DEL24), and shocked granite target rock (DEL17). A total of 197 PDF sets in 113 quartz grains were studied, and 186 sets resulted in rational crystallographic orientations. Common orientations include π{101̅2}, ω{101̅3}, z{101̅1}, ξ{112̅2}, and {101̅4}. In suevitic impact breccias and impact melt rocks, ballen silica and plagioclase with checkerboard texture were abundant. The petrographic results in Dellen impactites indicate a range of shock pressures from at least 2 to over 60 GPa, based on diagnostic shock metamorphic features in minerals and the occurrence of impact melt rock.

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“…This is probably due to the geological characteristics of this tectonic subprovince, where the lineaments reflect prominent geological structures in the bedrock and distinct Quaternary glacially derived formations (Skyttä et al, 2015;Torvela and Kurhila, 2022). The other provinces in Finland are also differently affected by erosional processes (Hall et al, 2021), which is especially evident in western Finland, where a flatter topographical surface especially hinders the identification of topographical lineaments.…”

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confidence: 95%

Aerogeophysics and light detecting and ranging (LiDAR)-based lineament interpretation of Finland at the scale of 1:500 000

Engström

Markovaara‐Koivisto

Ovaskainen

et al. 2023

Preprint

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Abstract. Lineaments, linear structures on the surface of the Earth, often represent the surface expressions of brittle structures, e.g., fault zones and fracture zones, or ductile shear zones. In addition, they may also represent other geological features such as lithological contacts, tectonic boundaries and Quaternary structures, or potentially a superposition of any of these. A lineament interpretation is usually the first step in the structural assessment of a crystalline bedrock setting, and the lineaments can further be used as basis for scientific research to more accurately determine the location of the previously mentioned various geological features. In this study, a multi-source lineament interpretation was performed within ArcGIS for the whole of Finland, based on light detecting and ranging (LiDAR), aerogeophysical and bathymetric raster data. The lineament database enhances the capability to produce more accurate geological maps for various geological purposes in Finland.

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Ultra-slow cratonic denudation in Finland since 1.5 Ga indicated by tiered unconformities and impact structures

Cited by 11 publications

References 138 publications

Keurusselkä impact structure, Finland—Overview, new observations, and renewed interpretation of the size

Keurusselkä impact structure, Finland—Overview, new observations, and renewed interpretation of the size

Petrographic studies and mineralogical characterization of the Dellen impactites

Aerogeophysics and light detecting and ranging (LiDAR)-based lineament interpretation of Finland at the scale of 1:500 000

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