Unveiling the nature of glassy impact spherules by analyzing pristine Chicxulub spherules from Gorgonilla IslandShow others and affiliations
2026 (English)In: Journal of South American Earth Sciences, ISSN 0895-9811, E-ISSN 1873-0647, Vol. 169, p. 105877-105877, article id 105877Article in journal (Refereed) Published
Abstract [en]
The Chicxulub impact triggered a massive extinction event marked by the Cretaceous-Paleogene boundary (K-Pg ∼66Ma), ejecting vast amounts of dust, molten, and vaporized materials. While impact spherules are interpreted as products of impactor and target lithologies, their precise composition and distribution remain insufficiently constrained. Although previous studies restrict impactor contamination to the condensed spherules from the fireball layer and the K-Pg boundary clay, here we show asteroid contribution to the composition of large spherules from the base of the K-Pg bed. Despite those spherules displaying an apparent immiscible bimodal composition of yellow (Ca-rich) and black (Si-rich) glasses, novel nano-resolution analyses demonstrate enrichment of elements derived from the impactor. By analyzing pristine spherules from the normally-graded sequence of Gorgonilla Island K-Pg site, our results show the presence of metals and platinum group elements (PGEs) in glasses and vesicles within large molten spherules. Furthermore, needle-like and cubic-shaped nanostructures co-localizing Pt, Co, Ni, and Pb, and Cu, Os, and Zn, may represent the first evidence of quasicrystals (quasi-periodic solids, not found in terrestrial rocks, with symmetries forbidden for crystals) in Chicxulub-derived deposits. Those nanostructures challenge the definitions of microtektites and microkrystites, suggesting these classifications are misleading. We recommend abandoning such terminology, preserving the generic term "impact spherules," irrespective of composition, morphology, or size. Our findings contribute to refining the classification and interpretation of impact spherules, advancing our understanding of the processes underlying hypervelocity impacts. Moreover, these insights may hold relevance not only for terrestrial impacts but also for analogous extraterrestrial contexts.
Place, publisher, year, edition, pages
2026. Vol. 169, p. 105877-105877, article id 105877
Keywords [en]
Chicxulub, Cretaceous-Paleogene boundary, Glassy impact spherules, Composition, Nanocrystals, Quasicrystals
National Category
Geochemistry Geology
Research subject
The changing Earth
Identifiers
URN: urn:nbn:se:nrm:diva-6307DOI: 10.1016/j.jsames.2025.105877OAI: oai:DiVA.org:nrm-6307DiVA, id: diva2:2025741
Funder
Swedish Research Council, 2018-07152Knut and Alice Wallenberg Foundation, KAW 2020.0145Wenner-Gren Foundations, SSh2023-0016Swedish Research Council Formas, 2019-02496Vinnova, 2018-04969
Note
This work was supported by the Knut and Alice Wallenberg Foundation, Sweden, grant KAW 2020.0145 (VV), and the Wenner-Gren Foundation, Sweden, grant SSh2023-0016 (VV). We thank Catherine H. Ross and two anonymous reviewers for their helpful comments and suggestions, which significantly improved the quality of this manuscript. We thank the beamline scientists and staff at the MAX IV synchrotron facility. We acknowledge MAX IV Laboratory for time on Beamline NanoMAX under Proposal 20190340 and Beamline Balder, Sweden, under Proposal 20210384. Research conducted at MAX IV, a Swedish national user facility, is supported by the Swedish Research Council, Sweden, under contract 2018–07152, the Swedish Governmental Agency for Innovation Systems, under contract 2018–04969, and Formas, Sweden, under contract 2019–02496.
2026-01-072026-01-072026-01-07Bibliographically approved