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The ~790 ka Australasian (micro)tektite strewn field is one of the most recent and best-known examples of impact ejecta emplacement as the result of a large-scale cratering event across a considerable part of Earth's surface (>10% in area). The Australasian strewn field is characterized by a tri-lobe pattern consisting of a large central distribution lobe, and two smaller side lobes extending to the west and east. Here, we report on the discovery of microtektite-like particles in sedimentary traps, containing abundant micrometeorite material, in the Sør Rondane Mountain (SRM) range of East Antarctica. The thirty-three glassy particles display a characteristic pale yellow color and are predominantly spherical in shape, except for a single dumbbell-shaped particle. The vitreous spherules range in size from 220 to 570 μm, with an average diameter of ~370 μm. This compares relatively well with the size distribution (75–778 μm) of Australasian microtektites previously recovered from the Transantarctic Mountains (TAM) and located ca. 2500–3000 km from the SRM. In addition, the chemical composition of the SRM particles exhibits limited variation and is nearly identical to the ‘normal-type’ (i.e., <6% MgO) TAM microtektites. The Sr and Nd isotope systematics for a single batch of SRM particles (n = 26) strongly support their affiliation with TAM microtektites and the Australasian tektite strewn field in general. Furthermore, Sr isotope ratios and Nd model ages suggest that the target material of the SRM particles was composed of a plagioclase- or carbonate-rich lithology derived from a Paleo- or Mesoproterozoic crustal unit. The affiliation to the Australasian strewn field requires long-range transportation, with estimated great circle distances of ca. 11,600 km from the hypothetical source crater, provided transportation occurred along the central distribution lobe. This is in agreement with the observations made for the Australasian microtektites recovered from Victoria Land (ca. 11,000 km) and Larkman Nunatak (ca. 12,000 km), which, on average, decrease in size and alkali concentrations (e.g., Na and K) as their distance from the source crater increases. The values for the SRM particles are intermediate to those of the Victoria Land and Larkman Nunatak microtektites for both parameters, thus supporting this observation. We therefore interpret the SRM particles as ‘normal-type’ Australasian microtektites, which significantly extend the central distribution lobe of the Australasian strewn field westward. Australasian microtektite distribution thus occurred on a continent-wide scale across Antarctica and allows for the identification of new, potential recovery sites on the Antarctic continent as well as the southeastern part of the Indian Ocean. Similar to volcanic ash layers, the ~790 ka distal Australasian impact ejecta are thus a record of an instantaneous event that can be used for time-stratigraphic correlation across Antarctica.
Bibliographical noteFunding Information:
We would like to thank the Research Foundation Flanders (FWO) for funding this PhD research to BS. SG, VD, MvG, and PC acknowledge the support by the Belgian Science Policy (BELSPO) through BELAM, Amundsen and BAMM projects. SG and PC also thank the Research Foundation - Flanders (FWO – Vlaanderen), and the VUB strategic research. SG, SC, PC, VD and FV acknowledge the support from the FWO–FNRS “Excellence of Science (EoS)” project ET–HoME (ID 30442502 ). NS and VD thank the FRS–FNRS for support, Wendy Debouge, Sabrina Cauchies and Jeroen de Jong are warmly thanked for their help and support with the clean lab and MC-ICP-MS at Laboratoire G-Time. We thank Christian Koeberl and an anonymous reviewer for their insightful comments. We also acknowledge the Associate Editor R.M. Palin for editorial handling.
© 2021 Elsevier B.V.
Copyright 2022 Elsevier B.V., All rights reserved.
- Impact cratering
- Impact ejecta
- Target stratigraphy
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1/11/19 → 31/10/24
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