The Lockne Crater: Revision and Reassessment of Structure and Impact Stratigraphy

Lindström, Maurits; Ormö, Jens; Sturkell, Erik; Dalwigk, Ilka von

doi:10.1007/3-540-27548-7_14

Cited by 44 publications

(121 citation statements)

References 15 publications

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“…1). The Lockne impact structure has a concentric morphology with an inner crater diameter of 7 km and an ejecta brim of crushed basement rocks up to 2.5 km wide (Lindström et al 2005). The target rocks consisted of a Proterozoic granitic basement overlain by a sedimentary cover of mainly black unconsolidated shale, limestone, and seawater (Sturkell 1998).…”

Section: Target Rocks and Impactitesmentioning

confidence: 99%

“…The matrix is mainly composed of finely crushed granitic material with traces of carbonaceous matter (Sturkell 1998). There are three main varieties of the Tandsbyn breccia (Lindström et al 2005): matrix-supported breccia, clastsupported breccia, and carbonaceous breccia. The carbonaceous breccia has a dark, sooty, or asphalt-like matrix derived from the carbon-rich shales.…”

Section: Target Rocks and Impactitesmentioning

confidence: 99%

“…The Loftarstone contains quartz grains with planar deformation features and microscopic particles of melted rock (Therriault and Lindström 1995). An autochthonous monomictic limestone breccia, referred to as the Ynntjärnen breccia (Lindström et al 2005), is located below the resurge deposits. Fig.…”

Section: Target Rocks and Impactitesmentioning

confidence: 99%

“…1. Geological map of the Lockne impact structure, after Lindström et al (2005). Sample localities 1-16 are marked on the map.…”

Section: Target Rocks and Impactitesmentioning

confidence: 99%

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Formation of uranium‐thorium‐rich bitumen nodules in the Lockne impact structure, Sweden: A mechanism for carbon concentration at impact sites

Lindgren

Parnell

Norman

et al. 2007

Meteorit & Planetary Scien

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Abstract-The Ordovician Lockne impact structure is located in central Sweden. The target lithology consisted of limestone and black unconsolidated shale overlaying a Precambrian crystalline basement. The Precambrian basement is uranium-rich, and the black shale is both uranium-and organic-rich. This circumstance makes Lockne a good candidate for testing the occurrence of U-Thrich bitumen nodules in an impact structure setting. U-Th-rich bitumen nodules are formed through irradiation; hence the increase in the complexity of organic matter by a radioactive (uranium-and thorium-rich) mineral phase. U-Th-rich bitumen nodules were detected in crystalline impact breccia and resurge deposits from the impact structure, but samples of non-impact-affected rocks from outside the impact structure do not contain any U-Th-rich bitumen nodules. This implies that in the Lockne impact structure, the nodules are associated with impact-related processes. U-Th-rich bitumen nodules occur throughout the geological record and are not restricted to an impact structure setting, but our studies at Lockne show that this process of irradiation can readily occur in impact structures where fracturing of rocks and a post-impact hydrothermal system enhances fluid circulation. The irradiation of organic matter by radioactive minerals has previously been proposed as a process for concentration of carbon on the early Earth. Impact structures are suggested as sites for prebiotic chemistry and primitive evolution, and irradiation by radioactive minerals could be an important mechanism for carbon concentration at impact sites.

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Section: Target Rocks and Impactitesmentioning

confidence: 99%

Section: Target Rocks and Impactitesmentioning

confidence: 99%

Section: Target Rocks and Impactitesmentioning

confidence: 99%

“…1. Geological map of the Lockne impact structure, after Lindström et al (2005). Sample localities 1-16 are marked on the map.…”

Section: Target Rocks and Impactitesmentioning

confidence: 99%

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Formation of uranium‐thorium‐rich bitumen nodules in the Lockne impact structure, Sweden: A mechanism for carbon concentration at impact sites

Lindgren

Parnell

Norman

et al. 2007

Meteorit & Planetary Scien

Self Cite

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“…There are a few examples of terrestrial impact craters that were affected but not destroyed by orogeny: Sudbury, Canada, (e.g., Riller 2005), Charlevoix, Canada (e.g., Trepmann and Spray 2005), Gardnos, Norway (French et al 1997), and Lockne, Sweden, (e.g., Lindström et al 1996;Sturkell 1998a;Lindström et al 2005a). Here, we focus on the Lockne crater, which is situated at the eastern border of the Caledonian orogen in central Sweden (Fig.…”

Section: Introductionmentioning

confidence: 99%

Coupled effects of impact and orogeny: Is the marine Lockne crater, Sweden, pristine?

Kenkmann¹,

Kiebach

Rosenau

et al. 2007

Meteorit & Planetary Scien

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Abstract-Our current understanding of marine-impact cratering processes is partly inferred from the geological structure of the Lockne crater. We present results of a mapping campaign and structural data indicating that this crater is not pristine. In the western part of the crater, pre-impact, impact, and post-impact rocks are incorporated in Caledonian thrust slices and are subjected to folding and faulting. A nappe outlier in the central crater depression is a relic of the Caledonian nappe cover that reached a thickness of more than 5 km. The overthrusted crater is gently deformed. Strike of strata and trend of fold axes deviate from standard Caledonian directions (northeast-southwest). Radially oriented crater depressions, which were previously regarded as marine resurge gullies formed when resurging seawater erosively cut through the crater brim, are interpreted to be open synclines in which resurge deposits were better preserved. The presence of the impact structure influenced orogenesis due to morphological and lithological anomalies of the crater: i) a raised crater brim zone acted as an obstacle during nappe propagation, (ii) the occurrence of a central crater depression caused downward sagging of nappes, and (iii) the lack of an appropriate detachment horizon (alum shale) within the crater led to an enhanced mechanical coupling and internal deformation of the nappe and the overthrusted foreland. Preliminary results of 3-D-analogue experiments suggest that a circular high-friction zone representing the crater locally hinders nappe propagation and initiates a circumferentially striking ramp fault that delineates the crater. Crustal shortening is also partitioned into the crater basement and decreases laterally outward. Deformation of the foreland affected the geometry of the detachment and could be associated with the activation of a deeper detachment horizon beneath the crater. Strain gradients both vertically and horizontally result in non-plane strain deformation in the vicinity of the crater. The strain tensors in the hanging and foot walls may deviate up to 90° from each other and rotated by up to 45° with respect to the standard regional orientation. The observed deflection of strata and fold axes within the Lockne crater area as revealed by field mapping is in agreement with the pattern of strain partitioning shown in the analogue models.

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The Modification Stage of Crater Formation

2012

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The Lockne Crater: Revision and Reassessment of Structure and Impact Stratigraphy

Cited by 44 publications

References 15 publications

Formation of uranium‐thorium‐rich bitumen nodules in the Lockne impact structure, Sweden: A mechanism for carbon concentration at impact sites

Formation of uranium‐thorium‐rich bitumen nodules in the Lockne impact structure, Sweden: A mechanism for carbon concentration at impact sites

Coupled effects of impact and orogeny: Is the marine Lockne crater, Sweden, pristine?

The Modification Stage of Crater Formation

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