ABSTRACT Four impact structures are known from the Republic of Kazakhstan, most of which have been poorly studied. This includes the Shili impact structure, an ~1.5-km-wide circular feature visible in satellite imagery. It is located in the western part of Kazakhstan, in the Aktobe Region, where the structure is centered at 49°10.5′N and 57°50′E. While the structure was first considered to be a salt diapir, its impact origin was confirmed in 1989 based on the findings of rare shocked quartz grains and a few poorly developed “shatter cones.” In this contribution, we report the results of a field campaign and a detailed petrographic investigation of 15 quartz sandstone samples. We confirm the presence of rare shocked quartz grains with planar fractures (PFs) and planar deformation features (PDFs). The characterization of shocked quartz allows us to not only confirm the impact origin of the structure, but also to estimate a shock pressure of at least 16 GPa (with a local peak-shock pressure of at least 20 GPa) for some of the rocks now outcropping at the surface. Signs of postimpact hydrothermal alteration include the decoration of many of the PDFs and the occurrence of fractures filled with secondary silica in a few samples. The name and some statistics commonly reported for this structure are also discussed. We suggest the structure be referred as “Shili,” after the name of a nearby river and also that of a phytonym. The minimum original diameter of the Shili impact crater is estimated at ~4–5 km based on a minimum central uplift diameter of 1 km. An early Eocene to Pliocene age for the formation of the Shili impact structure is inferred based on stratigraphy.

ABSTRACT The most recent comprehensive database of Martian impact craters was the result of the work of impact crater scientists (S.J. Robbins and B.M. Hynek) who carefully examined the available high-resolution imagery of Mars. Building on this previous work, we present the result of an alternative approach involving 56 planetary scientists and trained students. A web platform was designed for this purpose. All impact craters larger than 1 km in diameter were classified according to a simplified classification scheme, recording the primary or secondary nature of the crater, and the morphology of the ejecta (single, double, or multiple layered ejecta rampart sinuous [LERS], or low-aspect-ratio layer ejecta [LARLE]). In total, 8445 LERS craters, 24,530 partially buried craters, 55,309 secondary craters, and 288,155 craters in the category “standard” were identified. Our assessment differs for 8145 entries in the original database compiled by Robbins and Hynek, which are not considered to be impact structures. In this work, ~39,000 secondary craters have been associated with 108 primary craters. Coupled to the existing database, the database we propose here offers a complementary way to investigate the geological history of Mars. More specifically, the completion of layered ejecta crater morphologies down to 1 km and the connection established between secondary and primary impact crater sources will allow the implementation of statistical studies to reveal the spatial and temporal evolution of the impacted material characteristics. Thanks to the simplified classification we performed here, this version of the database can be easily used as a training data set for crater identification algorithms based on machine-learning techniques with the aim to identify smaller impact craters and to automatically define their morphological characteristics. Since it is not possible to confirm an impact structure from remote-sensing data alone, any Martian impact database at this stage remains subjective, and its assessment must be facilitated. The interface we developed for this participative project can be directly used for this purpose and for continuous updates and improvements of this work, in particular, with the latest high-resolution imagery releases such as the CTX global mosaic by J.L. Dickson and others, but also as a platform for building specific databases of craters or any other structures located in a particular region of interest.

ABSTRACT Quantitative insights into the geochemistry and petrology of proximal impactites are fundamental to understand the complex processes that affected target lithologies during and after hypervelocity impact events. Traditional analytical techniques used to obtain major- and trace-element data sets focus predominantly on either destructive whole-rock analysis or laboratory-intensive phase-specific micro-analysis. Here, we present micro–X-ray fluorescence (µXRF) as a state-of-the-art, time-efficient, and nondestructive alternative for major- and trace-element analysis for both small and large samples (up to 20 cm wide) of proximal impactites. We applied µXRF element mapping on 44 samples from the Chicxulub, Popigai, and Ries impact structures, including impact breccias, impact melt rocks, and shocked target lithologies. The µXRF mapping required limited to no sample preparation and rapidly generated high-resolution major- and trace-element maps (~1 h for 8 cm 2 , with a spatial resolution of 25 µm). These chemical distribution maps can be used as qualitative multi-element maps, as semiquantitative single-element heat maps, and as a basis for a novel image analysis workflow quantifying the modal abundance, size, shape, and degree of sorting of segmented components. The standardless fundamental parameters method was used to quantify the µXRF maps, and the results were compared with bulk powder techniques. Concentrations of most major elements (Na 2 O–CaO) were found to be accurate within 10% for thick sections. Overall, we demonstrate that µXRF is more than only a screening tool for heterogeneous impactites, because it rapidly produces bulk and phase-specific geochemical data sets that are suitable for various applications within the earth sciences.

ABSTRACT The Vredefort granophyre dikes have long been recognized as being derived from the now-eroded Vredefort melt sheet. One dike, in particular, the Daskop granophyre dike, is notable for a high abundance of lithic clasts derived from various stratigraphic levels. In this study, we mapped the distribution of the clasts throughout the continuously exposed section of the dike using field mapping and aerial drone photography and attempted to constrain the emplacement mechanisms of the dike. We found that the clasts are not homogeneously spread but instead are distributed between clast-rich zones, which have up to 50% by area clasts, and clast-poor zones, which have 0–10% by area clasts. We examined three models to explain this distribution: gravitational settling of clasts, thermally driven local assimilation of clasts, and mechanical sorting of clasts due to turbulent flow. Of the three models, the gravitational settling cannot be supported based on our field and geophysical data. The assimilation of clasts and turbulent flow of clasts, however, can both potentially result in inhomogeneous clast distribution. Zones of fully assimilated clasts and nonassimilated clasts can occur from spatial temperature differences of 100 °C. Mechanical sorting driven by a turbulent flow can also generate zones of inhomogeneous clast distribution. Both local assimilation and mechanical sorting due to turbulent flow likely contributed to the observed distribution of clasts.

ABSTRACT The impact-generated hydrothermal system at Vargeão Dome, Brazil, is a unique potential analogue for impact-generated hydrothermal systems on Mars. Its evolution can be understood through thermodynamic modeling, for which one of the necessary parameters is the composition of the involved water. The exact water composition for Vargeão at the time of the impact is unknown, and, moreover, the effect of this uncertainty is often underestimated in thermodynamic modeling. Here, the effect of initial water composition was tested by using a randomized set of initial solutions for thermodynamic modeling of the evolution of the Vargeão Dome impact-generated hydrothermal system. It was found that even small changes in composition could affect the precipitation of common minerals like calcite and quartz. Therefore, it is necessary to perform a sensitivity analysis for any thermodynamic model in which the initial solution is poorly constrained. Subsequently, the found effects were used to constrain water compositions for the Vargeão Dome system at the time of the impact, by eliminating randomized solutions of models precipitating different minerals from those observed in reality. Using a simple set of rules, it was possible to constrain the total amount of dissolved solids between 6 and 2000 mg/L, as well as provide approximate boundaries for all individual elements present in the solution.

ABSTRACT This contribution is concerned with the debated origin of the impact melt rock in the central uplift of the world’s largest confirmed impact structure—Vredefort (South Africa). New major- and trace-element abundances, including those of selected highly siderophile elements (HSEs), Re-Os isotope data, as well as the first Se isotope and Se-Te elemental systematics are presented for the felsic and mafic varieties of Vredefort impact melt rock known as “Vredefort Granophyre.” In addition to the long-recognized “normal” (i.e., felsic, >66 wt% SiO 2) granophyre variety, a more mafic (<66 wt% SiO 2) impact melt variety from Vredefort has been discussed for several years. The hypothesis that the mafic granophyre was formed from felsic granophyre through admixture (assimilation) of a mafic country rock component that then was melted and assimilated into the superheated impact melt has been pursued here by analysis of the two granophyre varieties, of the Dominion Group lava (actually meta-lava), and of epidiorite mafic country rock types. Chemical compositions, including high-precision isotope dilution–derived concentrations of selected highly siderophile elements (Re, Os, Ir, Pt, Se, Te), and Re-Os and Se isotope data support this hypothesis. A first-order estimate, based on these data, suggests that some mafic granophyre may have resulted from a significant admixture (assimilation) of epidiorite to felsic granophyre. This is in accordance with the findings of an earlier investigation using conventional isotope (Sr-Nd-Pb) data. Moreover, these outcomes are in contrast to a two-stage emplacement model for Vredefort Granophyre, whereby a mafic phase of impact melt, derived by differentiation of a crater-filling impact melt sheet, would have been emplaced into earlier-deposited felsic granophyre. Instead, all chemical and isotopic evidence so far favors formation of mafic granophyre by local assimilation of mafic country rock—most likely epidiorite—by a single intrusive impact melt phase, which is represented by the regionally homogeneous felsic granophyre.

ABSTRACT The ~11-km-wide, Paleoproterozoic Dhala impact structure in north-central India comprises voluminous exposures of impact melt breccia. These outcrops are discontinuously spread over a length of ~6 km in a semicircular pattern along the northern, inner limit of the monomict breccia ring around the central elevated area. This study of the magnetic fabrics of impact breccias and target rocks from the Dhala impact structure identified a weak preferred magnetic orientation for pre-impact crystalline target rocks. The pre- and synimpact rocks from Dhala have magnetite and ilmenite as common magnetic phases. The distributions of magnetic vectors are random for most impact melt breccia samples, but some do indicate a preferred orientation. Our anisotropy of magnetic susceptibility (AMS) data demonstrate that the shape of susceptibility ellipsoids for the target rocks varies from prolate to oblate, and most impact melt breccia samples display both shapes, with a slight bias toward the oblate geometry. The average value for the corrected degree of anisotropy of impact melt rock (P′ = 1.009) is lower than that for the target rocks (P′ = 1.091). The present study also shows that both impact melt breccia and target rock samples of the Dhala structure have undergone minor postimpact alteration, and have similar compositions in terms of magnetic phases and high viscosity. Fine-grained iron oxide or hydroxide is the main alteration phase in impact melt rocks. Impact melt rocks gave a narrow range of mean magnetic susceptibility (K m) and P′ values, in contrast to the target rock samples, which gave K m = 0.05–12.9 × 10 −3 standard international units (SI) and P′ = 1.036–1.283. This suggests similar viscosity of the source magma, and limited difference in the degrees of recorded deformation. Between Pagra and Maniar villages, the K m value of impact melt breccias gradually decreases in a clockwise direction, with a maximum value observed near Pagra (K m = 1.67 × 10 −3 SI). The poor grouping of magnetic fabrics for most impact melt rock samples implies local turbulence in rapidly cooled impact melt at the front of the melt flow immediately after the impact. The mean K 1 for most impact melt samples suggests subhorizontal (<5°) flow in various directions. The average value of K m for the target rocks (4.41 × 10 −3 SI) is much higher compared to the value for melt breccias (1.09 × 10 −3 SI). The results of this study suggest that the melt breccias were likely part of a sheet-like body of sizeable extent. Our magnetic fabric data are also supported by earlier core drilling information from ~70 locations, with coring depths reaching to −500 m. Our extensive field observations combined with available widespread subsurface data imply that the impact melt sheet could have covered as much as 12 km 2 in the Dhala structure, with an estimated minimum melt volume of ~2.4 km 3 .

ABSTRACT The earliest ejection process of impact cratering involves very high pressures and temperatures and causes near-surface material to be ejected faster than the initial impact velocity. On Earth, such material may be found hundreds to even thousands of kilometers away from the source crater as tektites. The mechanism yielding such great distances is not yet fully understood. Hypervelocity impact experiments give insights into this process, particularly as the technology necessary to record such rapid events in high temporal and spatial resolution has recently become available. To analyze the earliest stage of this hypervelocity process, two series of experiments were conducted with a two-stage light-gas gun, one using aluminum and the other using quartzite as target material. The vertical impacts of this study were recorded with a high-speed video camera at a temporal resolution of tens of nanoseconds for the first three microseconds after the projectile’s contact with the target. The images show a self-luminous, ellipsoidal vapor cloud expanding uprange. In order to obtain angle-resolved velocities of the expanding cloud, its entire front and the structure of the cloud were systematically investigated. The ejected material showed higher velocities at high angles to the target surface than at small angles, providing a possible explanation for the immense extent of the strewn fields.

ABSTRACT Finite deformation patterns of accessory phases can indicate the tectonic regime and deformation history of the host rocks and geological units. In this study, tectonically deformed, seismically deformed, and shocked zircon grains from a granite sample from the core of the Vredefort impact structure were analyzed in situ, using a combination of Raman spectroscopy, backscatter electron (BSE) imaging, electron backscattered diffraction (EBSD) mapping, electron probe microanalyses (EPMA), energy-dispersive X-ray spectroscopy (EDS) qualitative chemical mapping, and cathodoluminescence (CL) imaging. We aimed to reveal the effects of marginal grain-size reduction, planar deformation bands (PDBs), and shock microtwins on the crystal structure and microchemistry of zircon. Deformation patterns such as PDBs, microtwins, and subgrains did not show any significant effect on zircon crystallinity/metamictization degree or on the CL signature. However, the ratio of Raman band intensities B 1g (1008 cm –1) to E g (356 cm –1) slightly decreased within domains with low misorientation. The ratio values were affected in shocked grains, particularly in twinned domains with high misorientation. B 1g /E g ratio mapping combined with metamictization degree mapping (full width at half maximum of B 1g peak) suggest the presence of shock deformation features in zircon; however, due to the lower spatial resolution of the method, they must be used in combination with the EBSD technique. Additionally, we discovered anatase, quartz, goethite, calcite, and hematite micro-inclusions in the studied zircon grains, with quartz and anatase specifically being associated with strongly deformed domains of shocked zircon crystals.

ABSTRACT The rare earth element–bearing phosphate xenotime (YPO 4) is isostructural with zircon, and therefore it has been predicted that xenotime forms similar shock deformation microstructures. However, systematic characterization of the range of microstructures that form in xenotime has not been conducted previously. Here, we report a study of 25 xenotime grains from 10 shatter cones in silicified sandstone from the Spider impact structure in Western Australia. We used electron backscatter diffraction (EBSD) in order to characterize deformation and microstructures within xenotime. The studied grains preserve multiple sets of planar fractures, lamellar {112} deformation twins, high-angle planar deformation bands (PDBs), partially recrystallized domains, and pre-impact polycrystalline grains. Pressure estimates from microstructures in coexisting minerals (quartz and zircon) allow some broad empirical constraints on formation conditions of ~10–20 GPa to be placed on the observed microstructures in xenotime; at present, more precise formation conditions are unavailable due to the absence of experimental constraints. Results from this study indicate that the most promising microstructures in xenotime for recording shock deformation are lamellar {112} twins, polycrystalline grains, and high-angle PDBs. The {112} deformation twins in xenotime are likely to be a diagnostic shock indicator, but they may require a different stress regime than that of {112} twinning in zircon. Likewise, polycrystalline grains are suggestive of impact-induced thermal recrystallization; however, in contrast to zircon, the impact-generated polycrystalline xenotime grains here appear to have formed in the solid state, and, in some cases, they may be difficult to distinguish from diagenetic xenotime with broadly similar textures.

ABSTRACT With an age of less than ~5000 yr and a diameter of 45 m, Kamil crater in Egypt is one of the youngest and smallest terrestrial impact craters known to date. Abundant evidence of shock-deformed sandstone has been reported from Kamil crater, including shatter cones, vesicular impact glass, high-pressure polymorphs of silica and carbon, planar deformation features (PDFs) and planar fractures (PFs) in quartz, dissociated zircon, melt veins, and intergranular melt, giving rise to a range of estimated shock pressures from ~20 to ~60 GPa. Here, we investigated shocked zircon from Kamil crater through characterization of microstructures in a centimeter-sized clast of shocked nonporous sandstone ejecta, previously described as containing quartz grains with PDFs and PFs, coesite, stishovite, diamond, and lechatelierite. Orientation analysis by electron backscatter diffraction (EBSD) showed that the quartz arenite consists of damaged detrital quartz grains surrounded by a matrix of either comminuted quartz or intergranular melt. Individual quartz grains are pervasively fractured (abundant PFs and PDFs); apparent isotropic crushing resulted in uniformly and highly dispersed orientation clusters on pole figures. Zircon grains are not abundant; however, four of 19 grains analyzed by EBSD contained {112} deformation twin lamellae, with individual lamellae ranging in length from 1 to 2 µm. Lengths of twin lamellae in Kamil zircon grains are anomalously short compared to those reported in shocked zircon from other impact structures, where individual lamellae are tens of micrometers long. Previous empirical studies have suggested that {112} twin lamellae in zircon form at ~20 GPa in non-porous target rocks, a finding supported by their coexistence, in some impactites, with high-pressure phases such as reidite. The only available experimental constraint, by diamond anvil cell, found {112} twins in zircon powder quenched at 20 GPa. The presence of coesite, stishovite, lechatelierite, and shocked quartz with PDFs in the studied sample is consistent with empirically derived pressure estimates of ~20 GPa for {112} twin formation in zircon in the ejecta sample from Kamil crater. Kamil thus represents the smallest and youngest impact structure where shock-twinned zircon has been reported. Given the apparent efficiency of {112} twin formation (21% of grains), shock-twinned zircon is here shown to provide a robust and readily identifiable record of shock deformation in a relatively common mineral at one of the smallest known terrestrial impact craters.

ABSTRACT Crater-forming events are generally followed by the development of hydrothermal systems due to the rapid heating of the target rock. Such hydrothermal systems are a feature of nearly all large terrestrial impact structures. For the Siljan impact structure in Sweden, there is evidence for such a fossil hydrothermal system, possibly triggered by the impact event ca. 380 Ma. To investigate the thermal regime of the near-surface hydrothermal activity of the Siljan crater, biotite and amphibole grains extracted from samples collected in a transect across the high-pressure regime recorded by the central uplift, as well as from distal localities outside the central uplift of the crater, were dated using the 40 Ar/ 39 Ar laser step-heating technique. Our results show that biotite from inside the central uplift, which was strongly altered to chlorite by low-temperature (200–340 °C) hydrothermal reactions, yields strongly disturbed age spectra. The first and second (low laser power) step ages range from ca. 1300 to 190 Ma. In contrast, biotite from outside the central uplift and amphibole, irrespective of location inside or outside of the central uplift, are much less altered, which is reflected in less disturbed, near-flat age spectra. This result indicates that the hydrothermal temperatures inside the central uplift were >200 °C, sufficient to disturb the K-Ar system of biotite during its chloritization, but too low to affect the amphibole (closure temperature of 480–580 °C). In contrast, the temperature of the hydrothermal system outside of the central uplift was <200 °C, as no significant reset of the K-Ar system can be observed in either biotite or amphibole. Our results are consistent with estimated trapping temperatures from fluid inclusion studies, which show a decrease from 327–342 °C within the central uplift to 40–225 °C toward outside the central uplift. We conclude that the near-surface hydrothermal system in the Siljan impact structure was an impact-triggered system. This system was strongly active, with its highest temperature inside the central uplift and decreasing rapidly toward the outlying part of the crater.

ABSTRACT Accessory mineral U-Pb geochronometers are crucial tools for constraining the timing of deformation in a wide range of geological settings. Despite the growing recognition that intragrain age variations within deformed minerals can spatially correlate to zones of microstructural damage, the causal mechanisms of Pb loss are not always evident. Here, we report the first U-Pb data for shock-deformed xenotime, from a detrital grain collected at the Vredefort impact structure in South Africa. Orientation mapping revealed multiple shock features, including pervasive planar deformation bands (PDBs) that accommodate up to 40° of lattice misorientation by <100>{010} slip, and also an ~50-µm-wide intragrain shear zone that contains {112} deformation twin lamellae in two orientations. Twenty-nine in situ secondary ion mass spectrometry (SIMS) U-Pb analyses from all microstructural domains yielded a well-defined discordia with upper-intercept age of 2953 ± 15 Ma (mean square of weighted deviates [MSWD] = 0.57, n = 29, 2σ), consistent with derivation from Kaapvaal craton bedrock. However, the 1754 ± 150 Ma lower concordia intercept age falls between the 2020 Ma Vredefort impact and ca. 1100 Ma Kibaran orogenesis and is not well explained by multiple Pb-loss episodes. The pattern and degree of Pb loss (discordance) correlate with increased [U] but do not correlate to microstructure (twin, PDB) or to crystallinity (band contrast) at the scale of SIMS analysis. Numerical modeling of the Pb-loss history using a concordia-discordia-comparison (CDC) test indicated that the lower concordia age is instead best explained by an alteration episode at ca. 1750 Ma, rather than a multiple Pb-loss history. In this example, the U-Pb system in deformed xenotime does not record a clear signature of impact age resetting; rather, the implied high dislocation density recorded by planar deformation bands and the presence of deformation twins facilitated subsequent Pb loss during a younger event that affected the Witwatersrand basin. Microstructural characterization of xenotime targeted for geochronology provides a new tool for recognizing evidence of deformation and can provide insight into complex age data from highly strained grains, and, as is the case in this study, elucidate previously unrecognized alteration events.

ABSTRACT The Manicouagan impact event has been the subject of multiple age determinations over the past ~50 yr, providing an ideal test site for evaluating the viability of different geochronometers. This study highlights the suitability of Manicouagan’s essentially pristine impact melt body as a medium for providing insight into the U-Pb isotope systematics of geochronometers in the absence of shock-related overprinting. We performed in situ laser-ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U-Pb geochronology on apatite and zircon, both of which crystallized as primary phases. This study is the first application of U-Pb geochronology to apatite crystallized within a terrestrial impact melt sheet. U-Pb analyses were obtained from 200 melt-grown apatite grains (n = 222 spots), with a data subset providing a lower-intercept age of 212.5 ± 8.0 Ma. For melt-grown zircon, a total of 30 analyses from 28 grains were obtained, with a subset of the data yielding a lower-intercept age of 213.1 ± 1.6 Ma. The lower precision (±8.0 Ma; ±3%) obtained from apatite is a consequence of low U and a high and variable common-Pb composition. This resulted from localized Pb*/Pb C heterogeneity within the impact melt sheet that was incorporated into the apatite crystal structure during crystallization (where Pb*/Pb C is the ratio of radiogenic Pb to common Pb). While considered a limitation to the precision obtainable from melt-grown apatite, its ability to record local-scale isotopic variations highlights an advantage of U-Pb studies on melt-grown apatite. The best-estimate ages from zircon and apatite overlap within error and correlate with previously determined ages for the Manicouagan impact event. An average formation age from the new determinations, combined with previous age constraints, yields a weighted mean age of 214.96 ± 0.30 Ma for the Manicouagan impact structure.

ABSTRACT Constraints on impact-related hydrothermal alteration are important to enable the reconstruction of the possible processes affecting the surface of other terrestrial planets, such as Mars. Terrestrial impact structures excavated in basaltic targets provide the opportunity for analog studies. In Brazil, seven impact structures have been confirmed so far. Three of them, Vargeão Dome, Vista Alegre, and Cerro do Jarau, were formed in the same basaltic province belonging to the Paraná Basin, and they have several common characteristics. Oxidized basaltic breccias locally containing sandstone clasts occur in all these structures. In this work, selected samples of such breccias from the Vargeão Dome impact structure in southern Brazil were petrographically and geochemically investigated to further constrain the effects of the postimpact hydrothermal alteration. The breccia matrix shows typical oxidation effects induced by postimpact hydrothermal fluids, which highlight its heterogeneous nature, related to the impact event, and mixing components from different pre-impact stratigraphic formations. The detection of partially dissolved exsolution lamellae in pyroxene and of related alteration products constrains the effects of hydrothermal alteration in the basalts of the Vargeão Dome, which could serve as a terrestrial analog for planetary studies.

ABSTRACT Studies of impact structures in Sweden date back almost 60 years. They have so far resulted in the confirmation and understanding of eight impact structures and one impact-derived breccia layer, including the largest confirmed impact structure in the western part of Europe, the Siljan impact structure. Several additional structures have been proposed as impact derived, but they have to date not been confirmed. In this contribution, I summarize the current state of knowledge about the impact cratering record of Sweden. This is an up-to-date, comprehensive review of the features of known impact structures (and impact-related deposits) in Sweden. The described impact structures formed over a time period spanning from the Cambrian to the Cretaceous, and the preservation of several small (~1–2 km in diameter) Paleozoic impact structures indicates that the conditions securing their protection were close to optimal, with formation in a shallow epicontinental sea and rapid cover by protective sediments followed by a regional geologic evolution permitting their preservation. The generally well-preserved state of some of these crater structures contradicts the general assumption that such small impact structures can only be preserved for approximately a couple of thousand to a few million years. The Lockne-Målingen, Tvären, Granby, and Hummeln impact structures all have ages that place their formation in a period of proposed increased cratering rate on Earth following the breakup event of the L-chondrite parent body in the asteroid belt. However, to date, evidence other than a temporal correlation is missing for all of these structures except for Lockne (and Målingen), which has been shown to have formed by the impact of an L-chondritic body.