Composition and accretion rate of fossil micrometeorites recovered in Middle Triassic deep-sea deposits

Tetsuji Onoue, Tomoki Nakamura, Takeshi Haranosono, Chika Yasuda

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Micrometeorites, which are submillimeter-sized extraterrestrial particles that survive atmospheric entry, originate from dust-producing objects such as comets and asteroids. Although ancient micrometeorites found in sedimentary rocks are of key interest as a historical record of meteoroid populations in the solar system, they are rare and prone to severe chemical weathering. Here we report the recovery of well-preserved micrometeorites, older than 240 Ma, in radiolarian chert from Japan. The collection of micrometeorites comprised 258 cosmic spherules, which are particles that totally melted during atmospheric entry, and 2 coarse-grained unmelted micrometeorites. These micrometeorites are much older than any previous micrometeorite collection in the sedimentary record. Using this collection, we calculated the accretion rate of iron-type cosmic spherules to the Earth during the Anisian Stage of the Middle Triassic. The estimated accretion rate for Anisian iron-type spherules smaller than 125 μm is 25 ± 8 t yr-1. Analysis of the accretion rate for cosmic spherules also reveals high accretion rates of small spherules (~8-36 μm) for a 0.74 m.y. period in the late Anisian. However, the possible link between an enhancement in the accretion rate of small cosmic spherules in the late Anisian and variations in the flux of extraterrestrial matter to the Earth requires further scrutiny.

Original languageEnglish
Pages (from-to)567-570
Number of pages4
JournalGeology
Volume39
Issue number6
DOIs
Publication statusPublished - Jun 1 2011
Externally publishedYes

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micrometeorite
spherule
Triassic
accretion
Anisian
fossil
extraterrestrial matter
iron
chemical weathering
historical record
chert
rate
deep sea deposit
asteroid
comet
solar system
sedimentary rock
dust

All Science Journal Classification (ASJC) codes

  • Geology

Cite this

Composition and accretion rate of fossil micrometeorites recovered in Middle Triassic deep-sea deposits. / Onoue, Tetsuji; Nakamura, Tomoki; Haranosono, Takeshi; Yasuda, Chika.

In: Geology, Vol. 39, No. 6, 01.06.2011, p. 567-570.

Research output: Contribution to journalArticle

Onoue, Tetsuji ; Nakamura, Tomoki ; Haranosono, Takeshi ; Yasuda, Chika. / Composition and accretion rate of fossil micrometeorites recovered in Middle Triassic deep-sea deposits. In: Geology. 2011 ; Vol. 39, No. 6. pp. 567-570.
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