Meteoritics & Planetary Science最新文献

{"title":"Determining impact angle from the spatial distribution of shock metamorphism: A case study of the Gosses Bluff (Tnorala) impact structure, Australia","authors":"Eloise E. Matthews,&nbsp;Auriol S. P. Rae,&nbsp;Thomas Kenkmann,&nbsp;Nicholas E. Timms,&nbsp;Aaron J. Cavosie,&nbsp;Marian B. Holness","doi":"10.1111/maps.70070","DOIUrl":"https://doi.org/10.1111/maps.70070","url":null,"abstract":"<p>The majority of planetary impacts occur at oblique angles. Impact structures on Earth are commonly eroded or buried, rendering the identification of the direction and angle of impact—using methods such as asymmetries in ejecta distribution, surface topographic expression, central uplift structure, and geophysical anomalies—challenging. In this study, we investigate the potential of spatial asymmetries in shock metamorphism intensity to act as a quantitative constraint on the direction and angle of impact at the Gosses Bluff structure in Northern Territory, Australia. We measured the frequency of specific orientations of planar deformation features in quartz from nine samples around the central uplift and compared the spatial asymmetries in observed peak shock conditions with predictions from new three-dimensional numerical impact simulations of the formation of the Gosses Bluff structure. This comparison indicates formation by an impact along an approximately N→S trajectory at an angle of 52° ± 10°. The direction agrees with previous independent identification of structural asymmetry at the crater, although an attempt to constrain the impact angle has not been previously conducted. Alongside a trend of an increase in shock pressure recorded by down-range target rocks, we also observe a marked increase in shock metamorphism in the cross-range direction at Gosses Bluff. We attribute this pattern to the movement of faults in the central uplift during crater modification, displacing and dissecting the originally smooth distribution of shock metamorphism. This study provides new guidance for identifying and quantifying oblique impacts in the rock record, which is applicable to a large range of impact angles and crater sizes.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"61 7","pages":"1333-1354"},"PeriodicalIF":3.2,"publicationDate":"2026-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70070","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148532991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Magnetic properties of geraisites, the first tektite strewn field identified in Brazil","authors":"Melissa De Andrade Nunes,&nbsp;Ricardo I. F. Trindade,&nbsp;João Pedro Rodriguez Pinto,&nbsp;Alvaro P. Crósta,&nbsp;Gabriel G. Silva,&nbsp;Ludovic Ferrière,&nbsp;Camila R. Sales,&nbsp;Giovanna M. Tosi","doi":"10.1111/maps.70155","DOIUrl":"https://doi.org/10.1111/maps.70155","url":null,"abstract":"<p>Geraisites are a newly recognized class of tektite from Brazil. They occur as centimeter-sized, elongated to subspherical bodies scattered across surface gravel and shallow subsurface layers within a ~90-km-long strewn field extending between the municipalities of São João do Paraíso and Curral de Dentro, near the border between the states of Minas Gerais and Bahia. This study presents a rock magnetic characterization of geraisites, aimed at understanding their magnetic mineralogy and remanent magnetization. The samples exhibit weak bulk magnetization dominated by a paramagnetic contribution, consistent with typical tektite compositions. In addition, rock magnetic analyses indicate the presence of a ferromagnetic fraction, as evidenced by demagnetization curves and hysteresis behavior. Lowrie–Fuller test and isothermal remanent magnetization decomposition indicate a dominant low-coercivity component consistent with nanoscale magnetite grains in the single-domain to pseudo-single-domain range. In some samples, the remanence behavior suggests overprinting by transient high-field processes, such as lightning-induced remanent magnetization. Furthermore, geraisites show a distinct relationship between magnetic susceptibility and iron content compared to other splash-form tektites, reflecting their relatively enhanced ferromagnetic contribution. Overall, these results provide new insights into the magnetic properties of geraisites and their comparison with other tektite populations.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"61 7","pages":"1163-1178"},"PeriodicalIF":3.2,"publicationDate":"2026-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70155","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148534169","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"New Early Jurassic paleomagnetic age based on paleomagnetic and diagenetic study of the Kentland impact structure, Indiana","authors":"Christina Hamilton,&nbsp;Shannon Dulin,&nbsp;John Weber,&nbsp;R. Douglas Elmore","doi":"10.1111/maps.70139","DOIUrl":"https://doi.org/10.1111/maps.70139","url":null,"abstract":"<p>A paleomagnetic and petrographic study of host carbonate rocks and impact breccias at the Kentland impact structure was conducted to better constrain the timing of the impact and to test for alteration by hydrothermal fluids. The Ordovician-Silurian target rocks sampled are fossiliferous wackestone/packstones with minor dolomite. Polymict impact breccias, also sampled, occur as dikes/sills and contain clasts of dolomite, host carbonate, sandstone, sphalerite, and rare coated grains which contain clays, dolomite, calcite, and hexagonal silica resembling tridymite. The host carbonates contain brecciated zones near the polymict breccias that display flow textures of aligned and elongated clasts and minerals. Authigenic minerals present include sylvite, apatite, gypsum, magnetite, and hematite. These observations suggest alteration by hydrothermal fluids, which probably had an estimated duration of ~7500 yrs after impact. Alternating field (AF) and thermal demagnetization of impact breccia and host carbonate specimens removed two post-tilting magnetic components: one with southerly declinations and moderate negative inclinations and the other with northerly declinations and positive inclinations. Demagnetization results suggest the magnetizations primarily reside in magnetite as well as hematite and possibly pyrrhotite. Petrographic and rock magnetic results are consistent with this interpretation. These magnetizations are interpreted as chemical remanent magnetizations acquired through a reversal, which formed from alteration by hydrothermal fluids generated after the impact. The paleomagnetic poles (mean pole, 75.7° N, 98.4° W) fall near the Early Jurassic part of the apparent polar wander path, which suggests the alteration in the breccias, and likely the impact, occurred in the Early Jurassic (175–185 Ma).</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"61 7","pages":"1243-1262"},"PeriodicalIF":3.2,"publicationDate":"2026-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148533006","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Confirmation of the impact origin of the Late Ordovician Tvären impact structure (southeast Sweden) and emplacement of impactites in a marine setting","authors":"Katarzyna J. Gajewska,&nbsp;Sanna Alwmark,&nbsp;Mikael Calner,&nbsp;Sylvain Richoz,&nbsp;Jens Ormö,&nbsp;Erik Sturkell,&nbsp;Carl Alwmark","doi":"10.1111/maps.70128","DOIUrl":"https://doi.org/10.1111/maps.70128","url":null,"abstract":"<p>The Tvären structure in southeastern Sweden has been listed as a confirmed marine-target impact structure for decades. However, to date, no measurements and/or indexed data of planar deformation features in quartz grains from the structure have been published or any other unequivocal evidence of impact. Here, we present an investigation aimed at searching for shocked quartz in the 224 m deep Tvären-2 drill core. We confirm that the rocks of this core contain, on average, about 5% of shocked quartz, either displaying up to 10 sets of planar deformation features, planar fractures, or both. Petrographic investigation resulted in a division of the core into four main stratigraphic units: (i) lithic impact breccia; (ii) coarse melt-bearing resurge deposit; (iii) finer melt-bearing resurge deposit; and (iv) post-impact deposit. Studying sedimentary facies and structures as well as using petrographic and textural characteristics of the material made it possible to recreate the process of crater formation. We describe a sequence of excavation stage-generated crystalline breccia overlain by early modification stage polymictic breccia with crystalline and limestone clasts formed when the collapse of the crater rim and walls had begun. This breccia is, in turn, overlain by a resurge deposit comprised of material brought into the crater as the water returned. Hence, studying macro- and microstructures is yet another approach to better understand the mechanisms involved in the formation of small impact craters and their associated deposits in marine environments.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"61 7","pages":"1188-1212"},"PeriodicalIF":3.2,"publicationDate":"2026-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70128","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148533302","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Iron redox variations in Australasian Muong Nong-type tektites","authors":"Gabriele Giuli,&nbsp;Maria Rita Cicconi,&nbsp;Angela Trapananti,&nbsp;Sigrid Griet Eeckhout,&nbsp;Giovanni Pratesi,&nbsp;Christian Koeberl","doi":"10.1111/maps.70156","DOIUrl":"https://doi.org/10.1111/maps.70156","url":null,"abstract":"<p>Two thin sections of Muong Nong-type tektites from the Australasian tektite strewn field have been analyzed by Fe K-edge X-ray absorption near edge spectroscopy (XANES), using a hundreds-of-micrometers–sized beam suitable for spatially resolved analysis of the Fe oxidation state across distinct regions of the samples. Earlier analyses with an unfocused beam were inconclusive regarding different amounts of oxidized iron in the Muong Nong-type tektites, but did indicate different chemical compositions of the lighter and darker colored layers. Experimental XANES spectra are very similar in shape to those of other tektites. However, small and reproducible changes were found in the pre-edge peak involving the centroid energy: the pre-edge peak of the spectra collected within the dark layers are reproducibly 0.2 eV at higher energy than those of the spectra collected within the light matrix. This difference in energy position is four times the estimated energy reproducibility and, therefore, is significant. By comparison with pre-edge peak data of Fe model compounds, we estimate the Fe³⁺/(Fe²⁺+Fe³⁺) ratios in the light matrix and dark layers to be 5% and 15% (±5), respectively. The heterogeneous distribution of the Fe oxidation state in Muong Nong-type tektites, as opposed to the homogeneous Fe oxidation state distribution in splash-form tektites, is consistent with previous hypotheses, based on volatile contents, of Muong Nong-type tektites resulting from melts that experienced lower temperatures compared to those of splash-form tektites.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"61 7","pages":"1179-1187"},"PeriodicalIF":3.2,"publicationDate":"2026-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148534128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Vertical profiling of shock attenuation at the Rochechouart impact structure, France","authors":"P. Struzynska,&nbsp;S. Alwmark,&nbsp;C. Alwmark,&nbsp;M. H. Poelchau,&nbsp;P. Lambert","doi":"10.1111/maps.70078","DOIUrl":"https://doi.org/10.1111/maps.70078","url":null,"abstract":"<p>Rochechouart, south-west France, is a complex impact structure. Here, we present the first report of shock barometry of quartz from what are likely parautochthonous basement units at depth, based on samples from the 2017 C.I.R.I.R drilling campaign. The crystallographic orientations of 725 sets of PDFs in 512 quartz grains in samples from four drill cores were measured. We find basal PDFs (Brazil twins) as shear indicators and rhombohedral PDFs recording moderate shock pressures of 10–15 GPa, with numbers of sets per grain ranging from 1.0 to 2.1. A staggering 59.5% of the measured parautochthonous PDF sets are basal PDFs. We find a decrease of shock-metamorphic overprint from 10–15 to 5–10 GPa at site SC16 (Montoume), ~4.5 km south of what is currently held as the apparent crater center. Based on the abundance of low-to-moderate shock pressures and a lack of more highly shocked parautochthonous units, we discuss two well-defined scenarios for this occurrence. Scenario 1 attributes Rochechouart parautochthonous basement target material to have been subjected to at most 15 GPa as per our results. In scenario 2, the drilling only sampled the flanks of the central uplift but not its more strongly shocked center. Our favored hypothesis is the latter, and thus we relate our lack of highly shocked parautochthonous units to a lack of samples from the immediate center of the structure. Finally, based on the extent of PDFs from our shock barometry study of quartz, we estimate the minimum extent for the diameter of the structure to be 24 km.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"61 7","pages":"1434-1455"},"PeriodicalIF":3.2,"publicationDate":"2026-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70078","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148532766","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A geophysical investigation of the Roter Kamm impact crater, Namibia","authors":"Hannah Nienhaus,&nbsp;Pritam Yogeshwar,&nbsp;Wiebke Mörbe,&nbsp;Bülent Tezkan,&nbsp;Yajun Liu,&nbsp;Bufelo Lushetile,&nbsp;Martin Melles","doi":"10.1111/maps.70088","DOIUrl":"https://doi.org/10.1111/maps.70088","url":null,"abstract":"<p>The Roter Kamm impact crater is located in the southern Namib Desert. The crater has a diameter of 2.5 km and belongs to the category of simple, bowl-shaped impact craters, with an elevated rim of fractured target rock. The crater's interior is completely buried beneath sediments, preventing extensive surface investigations of the bedrock topography. Geophysical investigations were carried out to better characterize the sediment cover, the resulting shape of the crater, and the infill of the impact structure. Two electromagnetic techniques, transient electromagnetics and audiomagnetotellurics, were used to study the subsurface resistivity structure across and beyond the Roter Kamm crater along two transects. The postimpact sediments inside the crater reach thicknesses up to 340 m. The surface of the underlying brecciated zone exhibits the characteristic bowl-shape of a simple crater. A prominent conductive anomaly was found inside the sedimentary succession, indicating the presence of water. The boundary between fluid-saturated and dry material likely marks the transition from postimpact sediments to impact breccia. Our results provide the first geophysical model of the sedimentary infill of the Roter Kamm impact crater derived from electromagnetic methods.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"61 7","pages":"1386-1398"},"PeriodicalIF":3.2,"publicationDate":"2026-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70088","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148533020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Confirming the impact origin of the São Miguel do Tapuio structure, northeastern Brazil","authors":"Alvaro Penteado Crósta,&nbsp;Neivaldo Araújo de Castro,&nbsp;Marcos Alberto Rodrigues Vasconcelos,&nbsp;Airton Natanael Coelho Dias,&nbsp;Ludovic Ferrière,&nbsp;Wolf Uwe Reimold,&nbsp;Ana Maria Góes,&nbsp;Jackson Alves Martins,&nbsp;Liliana Sayuri Osako,&nbsp;Raimundo Mariano Gomes Castelo Branco","doi":"10.1111/maps.70144","DOIUrl":"https://doi.org/10.1111/maps.70144","url":null,"abstract":"<p>The São Miguel do Tapuio structure (SMT) is a remarkable, nearcircular feature of about 21 km diameter, centered at 5°37.6′ S, 41°23.3′ W in Piauí state, northeastern Brazil. The structure is located within the sedimentary strata of the Paleozoic–Mesozoic Parnaíba Basin and predominantly comprises sandstones of the Devonian Pimenteiras and Cabeças formations. SMT exhibits a rugged morphology, in contrast to the smoother surrounding terrain. An impact origin has been suggested for SMT since the 1980s based on indirect aspects, such as the structure's morphology with an annular outer rim, inner rings, and an elevated central area. Some of the sandstones found in the inner region were structurally deformed and recrystallized, in contrast to the undeformed equivalent strata outside the structure. A field survey conducted in 2017 yielded a few samples of sandstone and monomict sandstone breccia from near the center of the structure. Here we report the discovery of multiple shocked quartz grains with planar fractures (PFs), feather features (FFs), and planar deformation features (PDFs) in four thin sections of two samples from this central area. Universal stage measurements on all shocked quartz grains (25 grains in total; 16 with PFs, five with PDFs, and four with both PFs and PDFs) confirm that these planar microstructures occur in distinct crystallographic orientations that are indicative of shock pressures up to 20 GPa. Our investigations, thus, have confirmed the impact origin of the SMT. It represents the ninth confirmed impact structure in Brazil and, at 21 km diameter, is the second largest of its kind in South America.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"61 7","pages":"1263-1287"},"PeriodicalIF":3.2,"publicationDate":"2026-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70144","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148533217","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Doing geology by looking up, doing astronomy by looking down (with a focus on the Umbria–Marche pelagic limestones of Italy)","authors":"Walter Alvarez","doi":"10.1111/maps.70084","DOIUrl":"https://doi.org/10.1111/maps.70084","url":null,"abstract":"<p>Astronomy and geology: the first deals with myriad, enormous, unreachable objects seen at great distances and at very low resolution; the other investigates one tiny (by comparison) object, Earth, at close range, from planetary scale down to almost atomic resolution in the laboratory. Planetary Science, studying solar system objects, to some extent bridges the gap between astronomy and geology. Astronomers mostly look up; geologists mostly look down. This paper lists cases where studies in one of those fields have contributed to understanding in the other. The central focus is on investigations of the Cretaceous and Paleogene pelagic Scaglia limestone in the Italian Apennine Mountains where geologic studies bear on five classes of solar system objects. The classes are separated by three orders of magnitude in size: the Moon-forming impactor, bolides that form craters on Earth, meteorites, meteor-forming grains, and extraterrestrial dust. The paper closes by calling attention to LIGO, the Laser Interferometer Gravitational-Wave Observatory, in which astronomical discoveries made by looking down have yielded a geological discovery done by looking up. LIGO has detected distant collisions involving black holes and neutron stars by measuring infinitesimal distortions of the Earth, which in turn have shown that at least some of Earth's supply of heavy elements has been created by collisions of pairs of neutron stars—a major contribution to geochemistry and cosmochemistry.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"61 7","pages":"1108-1121"},"PeriodicalIF":3.2,"publicationDate":"2026-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148533738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geochemical investigation of impactites from the Boltysh impact structure and possible relationship to early Danian sediments from the Umbria–Marche Basin, Italy","authors":"Toni Schulz,&nbsp;Sophia Wernitznig,&nbsp;Christian Koeberl,&nbsp;Bérengère Mougel,&nbsp;Alessandro Montanari,&nbsp;Frédéric Moynier","doi":"10.1111/maps.70174","DOIUrl":"https://doi.org/10.1111/maps.70174","url":null,"abstract":"<p>Within the Danian Scaglia Rossa Formation appears a regionally correlatable horizon cutting across multiple sections and outcrops within the Umbria–Marche Basin of NE Italy, where it is intercalated with uniform pelagic carbonate successions. This horizon is called “ALE layer” and has tentatively been interpreted as a fine-grained volcanic ash. A key motivation for this study is the striking agreement between the ages of the ALE bed (65.440 ± 0.005 Ma) and the Boltysh impact event (65.39 ± 0.14/0.16 Ma), raising the possibility that the ALE layer preserves a distal Boltysh ejecta component transported over ~1600 km, while its bulk may reflect a longer duration volcanosedimentary depositional interval. To test this hypothesis, we combine impact-scaling considerations with highly siderophile element (HSE) and Cr-Os isotope data for Boltysh impactites and geochemical and Os isotopic analyses of the ALE horizon. Chromium isotope compositions of the Boltysh impactites (as low as ε⁵⁴Cr = −0.31) may indicate an extraterrestrial contribution; however, their interpretation remains ambiguous. If interpreted as such, implausibly high IIIAB iron meteoritic admixtures would be required. By contrast, HSE abundances and ¹⁸⁷Os/¹⁸⁸Os systematics indicate clearly resolvable meteoritic components of up to 1 wt% CI-equivalent, forming coherent crust–chondrite mixing arrays. The ALE bed, though dominated by volcanosedimentary material, consistently shows Os–Ir–Pt–Pd enrichments far above the pelagic background, requiring up to ~0.8 wt% CI meteoritic input if interpreted in terms of an impact event horizon. Unradiogenic ¹⁸⁷Os/¹⁸⁸Os excursions occur primarily within the ALE layer, but in some cases extend into adjacent pelagic carbonate layers stratigraphically above and below the ALE layer. These unradiogenic ¹⁸⁷Os/¹⁸⁸Os excursions define chondritic-trending trajectories that mirror those in the Boltysh samples and are interpreted as diffusion-modified expressions of an originally ALE-centered meteoritic Os input. Taken together, the temporal coincidence between the Boltysh impact event and the ALE layer, impact-scaling relationships, and HSE- and Os-isotopic signatures favors the interpretation that the ALE layer preserves a distal equivalent of the Boltysh impact ejecta diluted within a volcanosedimentary depositional system that was subsequently modified by diagenetic processes.</p>","PeriodicalId":18555,"journal":{"name":"Meteoritics & Planetary Science","volume":"61 7","pages":"1309-1332"},"PeriodicalIF":3.2,"publicationDate":"2026-07-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/maps.70174","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"148533830","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}