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From the mid-Ordovician into the Late Silurian : Changes in the micrometeorite flux after the L chondrite parent breakup

Martin, Ellinor LU ; Schmitz, Birger LU and Schönlaub, Hans Peter (2018) In Meteoritics and Planetary Science 53(12). p.2541-2557
Abstract

We present the first reconstruction of the micrometeorite flux to Earth in the Silurian Period. We searched 321 kg of condensed, marine limestone from the Late Silurian Cellon section, southern Austria, for refractory chrome-spinel grains from micrometeorites that fell on the ancient sea floor. A total of 155 extraterrestrial spinel grains (10 grains >63 μm, and 145 in the 32-63 μm fraction) were recovered. For comparison, we searched 102 kg of similar limestone from the mid-Ordovician Komstad Formation in southern Sweden. This limestone formed within ~1 Ma after the breakup of the L chondrite parent body (LCPB) in the asteroid belt. In the sample we found 444 extraterrestrial spinel grains in the >63 μm fraction, and estimate a... (More)

We present the first reconstruction of the micrometeorite flux to Earth in the Silurian Period. We searched 321 kg of condensed, marine limestone from the Late Silurian Cellon section, southern Austria, for refractory chrome-spinel grains from micrometeorites that fell on the ancient sea floor. A total of 155 extraterrestrial spinel grains (10 grains >63 μm, and 145 in the 32-63 μm fraction) were recovered. For comparison, we searched 102 kg of similar limestone from the mid-Ordovician Komstad Formation in southern Sweden. This limestone formed within ~1 Ma after the breakup of the L chondrite parent body (LCPB) in the asteroid belt. In the sample we found 444 extraterrestrial spinel grains in the >63 μm fraction, and estimate a content of at least 7000 such grains in the 32-63 μm fraction. Our results show that in the late Silurian, ~40 Ma after the LCPB, the flux of ordinary equilibrated chondrites has decreased by two orders of magnitude, almost down to background levels. Among the ordinary chondrites, the dominance of L-chondritic micrometeorites has waned off significantly, from >99% in the post-LCPB mid-Ordovician to ~60% in the Late Silurian, with ~30% H-, and ~10% LL-chondritic grains. In the Late Silurian, primitive achondrite abundances are similar to today's value, contrasting to the much higher abundances observed in pre-LCPB mid-Ordovician sediments.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Meteoritics and Planetary Science
volume
53
issue
12
pages
2541 - 2557
publisher
Wiley-Blackwell
external identifiers
  • scopus:85051007959
ISSN
1086-9379
DOI
10.1111/maps.13174
language
English
LU publication?
yes
id
87efcd2a-2524-4d13-9309-6de21a29b666
date added to LUP
2018-09-13 08:13:17
date last changed
2019-02-20 11:26:40
@article{87efcd2a-2524-4d13-9309-6de21a29b666,
  abstract     = {<p>We present the first reconstruction of the micrometeorite flux to Earth in the Silurian Period. We searched 321 kg of condensed, marine limestone from the Late Silurian Cellon section, southern Austria, for refractory chrome-spinel grains from micrometeorites that fell on the ancient sea floor. A total of 155 extraterrestrial spinel grains (10 grains &gt;63 μm, and 145 in the 32-63 μm fraction) were recovered. For comparison, we searched 102 kg of similar limestone from the mid-Ordovician Komstad Formation in southern Sweden. This limestone formed within ~1 Ma after the breakup of the L chondrite parent body (LCPB) in the asteroid belt. In the sample we found 444 extraterrestrial spinel grains in the &gt;63 μm fraction, and estimate a content of at least 7000 such grains in the 32-63 μm fraction. Our results show that in the late Silurian, ~40 Ma after the LCPB, the flux of ordinary equilibrated chondrites has decreased by two orders of magnitude, almost down to background levels. Among the ordinary chondrites, the dominance of L-chondritic micrometeorites has waned off significantly, from &gt;99% in the post-LCPB mid-Ordovician to ~60% in the Late Silurian, with ~30% H-, and ~10% LL-chondritic grains. In the Late Silurian, primitive achondrite abundances are similar to today's value, contrasting to the much higher abundances observed in pre-LCPB mid-Ordovician sediments.</p>},
  author       = {Martin, Ellinor and Schmitz, Birger and Schönlaub, Hans Peter},
  issn         = {1086-9379},
  language     = {eng},
  month        = {07},
  number       = {12},
  pages        = {2541--2557},
  publisher    = {Wiley-Blackwell},
  series       = {Meteoritics and Planetary Science},
  title        = {From the mid-Ordovician into the Late Silurian : Changes in the micrometeorite flux after the L chondrite parent breakup},
  url          = {http://dx.doi.org/10.1111/maps.13174},
  volume       = {53},
  year         = {2018},
}