Undetection of Australasian microtektites in the Chinese Loess Plateau

Pan, Yan; Xiao, Zhiyong; Xiao, Guoqiao; Pan, Qing; Hui, Hejiu; Wu, Yunhua; Ma, Yizhen; Xu, Yongjiang

doi:10.1016/j.palaeo.2021.110721

Cited by 6 publications

(4 citation statements)

References 88 publications

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“…South China is an important geographic branch of AASF (Figure 1b), because this area is the northern portion of this strewn field (Yan et al., 2022), and it corresponds to the uprange of the hypothesized impactor trajectory. Numerical simulations suggested that impact plume formed by an oblique impact would be inclined toward the downrange, so that much fewer impact melt that was engulfed in the impact plume was capable to form tektites at the uprange (Artemieva, 2013; Stöffler et al., 2002).…”

Section: Introductionmentioning

confidence: 99%

Magnetic Properties of Australasian Tektites From South China

Pan

Shi

et al. 2023

JGR Solid Earth

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South China, the northern part of the Australasian strewn field (AASF) of tektites and microtektites is located at the uprange of the hypothesized source crater that is still unconfirmed. Magnetic properties of impact glasses are an important indicator of their source materials and thermal history. Extensive magnetic investigations have been performed on various AASF tektites sampled from both the Indochina Peninsula and further south, but such information remains sparse for those sampled from South China. Here, we present a detailed rock magnetism study for both Muong Nong‐type and splash‐form AASF tektites from South China, showing that all the tektites have rather weak remanent magnetization, but ferromagnetic information can be extracted from their dominating paramagnetic signal. Signals caused by superparamagnetic particles are elusive, but those of single domain magnetite are detected in the splash‐form tektites, and signals of pseudo‐single domain magnetite are discovered in the Muong Nong‐type tektites. Each morphological type of tektites from a same geographic area exhibits large dispersions in their magnetic properties. Across the entire AASF, the Muong Nong‐type tektites from South China exhibit the lowest average magnetic susceptibility, and the splash‐form tektites exhibit the smallest average natural remanent magnetization and ratio of equivalent magnetization. The observed heterogeneous magnetic properties are mainly caused by the different contents and sizes of magnetic particles, which can be explained by the different shock level and/or cooling history of the tektite melts. Micro‐sized immiscible Fe‐S spherules in the Muong Nong‐type tektites from South China were likely originated from the pre‐impact target.

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Section: Introductionmentioning

confidence: 99%

Magnetic Properties of Australasian Tektites From South China

Pan

Shi

et al. 2023

JGR Solid Earth

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“… Sampling locations of the investigated tektites from South China in this study. Inserted image shows approximate geographic boundaries of the Australasian strewn field of tektites and microtektites (Yan et al., 2022), and the white box denotes boundaries of the study area. Red circles represent locations of studied splash‐form tektites in South China.…”

Section: Introductionmentioning

confidence: 99%

“…South China is an end‐member geographic branch of AASF (Figure 1) because this area is located at the northern edge of this strewn field and corresponds to the uprange region with respect to the hypothesized impactor trajectory (Prasad et al., 2007; Yan et al., 2022). Both splash‐form and Muong Nong‐type tektites are widespread on the continent of South China, but their magnetic properties are underrepresented in the literature.…”

Section: Introductionmentioning

confidence: 99%

Magnetite in Muong Nong‐Type Australasian Tektites From South China

Pan,

Xiao,

et al. 2023

Geochem Geophys Geosyst

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South China belongs to the northern geographic branch of the Australasian strewn field (AASF) of tektites and microtektites, and this area is assumed to be part of the uprange region of the putative impactor trajectory that formed the yet undiscovered source crater. Ferromagnetic minerals in impact glass may record the magnetization process and thermal history of impact melt, but the possible identity of ferromagnetic minerals in AASF tektites from South China is elusive. Here, we perform a rock magnetism and crystallography study of iron‐sulfur spherules in Muong Nong‐type tektites from South China, revealing abundant single‐domain and pseudo single‐domain nano‐grains of magnetite within the spherules. This result is consistent with the detection of magnetic signals caused by single‐domain and pseudo single‐domain magnetite in these samples. Compared to the large value ranges of magnetic properties of tektites in the entire strewn field, individual specimens of both Muong Nong‐type and single splash‐form tektites have relatively homogeneous magnetic properties in terms of magnetic susceptibility, natural remanent magnetization (NRM), saturation isothermal remanent magnetization (SIRM) and NRM/SIRM ratio. The results indicate that the impact melt that formed each tektite specimen experienced similar thermal history, and most AASF tektites from South China were cooled in an ambient magnetic field that is the same order of magnitude as the Earth's magnetic field.

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“…The insufficient size of the putative crater has been questioned also by Burrett (2021) and Whymark (2021), and several other points of criticism have been presented by Whymark (2021) including geochemical incompatibility of supposed source materials with AAT, insufficient size of the putative crater, the absence of a sufficiently thick and by appearance suitable proximal ejecta blanket, and unconvincing study of the planar deformation features observed in quartz grains recovered from the supposed ejecta blanket. The latter point has also been questioned by Yan et al (2022).…”

Section: Introductionmentioning

confidence: 99%

Quest for the Australasian impact crater: Failings of the candidate location at the Bolaven Plateau, Southern Laos

Mizera

2022

Meteorit & Planetary Scien

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The quest for the parent impact structure for Australasian tektites (AAT) has remained without solution for almost a century. The present paper doubts the plausibility of the recently proposed location of the impact site at the Bolaven volcanic field in Southern Laos by showing problems with most of the presented lines of evidence. The geochemical incompatibility of the AAT composition with a mixture of weathered basalts and Mesozoic sandstones that were proposed as source materials of AAT is demonstrated by a two‐component mixing calculation for major element oxides and the Nd‐Sr isotopic system. Deficiency of the basaltic component as a source of Ni, Co, Cr, and 10Be in AAT and inconsistency with trends observed for O and Pb isotopes are shown. The size of the putative crater, conclusiveness of a gravity anomaly identification, signs of complete crater burial by postimpact lava flows, and identification of proximal ejecta blanket are doubted. Remarks on the shortcomings of the current consensus location of an impact site for AAT in Indochina are presented.

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Undetection of Australasian microtektites in the Chinese Loess Plateau

Cited by 6 publications

References 88 publications

Magnetic Properties of Australasian Tektites From South China

Magnetic Properties of Australasian Tektites From South China

Magnetite in Muong Nong‐Type Australasian Tektites From South China

Quest for the Australasian impact crater: Failings of the candidate location at the Bolaven Plateau, Southern Laos

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