{"id":16029,"date":"2018-08-01T09:09:27","date_gmt":"2018-08-01T07:09:27","guid":{"rendered":"http:\/\/karmaka.de\/?p=16029"},"modified":"2018-08-01T09:09:27","modified_gmt":"2018-08-01T07:09:27","slug":"from-the-mid%e2%80%90ordovician-into-the-late-silurian-changes-in-the-micrometeorite-flux-after-the-l-chondrite-parent-breakup","status":"publish","type":"post","link":"https:\/\/karmaka.de\/?p=16029","title":{"rendered":"From the mid\u2010Ordovician into the Late Silurian: Changes in the micrometeorite flux after the L chondrite parent breakup"},"content":{"rendered":"<p>Ellinor Martin, Birger Schmitz, Hans\u2010Peter Sch\u00f6nlaub<\/p>\n<p><a href=\"https:\/\/onlinelibrary.wiley.com\/doi\/full\/10.1111\/maps.13174\" target=\"_blank\"><strong>LINK<\/strong><\/a><\/p>\n<p>Meteorit Planet Sci. . doi:10.1111\/maps.13174<\/p>\n<p>&#8220;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\u2010spinel grains from micrometeorites that fell on the ancient sea floor. A total of 155 extraterrestrial spinel grains (10 grains >63 \u03bcm, and 145 in the 32\u201363 \u03bcm fraction) were recovered. For comparison, we searched 102 kg of similar limestone from the mid\u2010Ordovician 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 \u03bcm fraction, and estimate a content of at least 7000 such grains in the 32\u201363 \u03bcm 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\u2010chondritic micrometeorites has waned off significantly, from >99% in the post\u2010LCPB mid\u2010Ordovician to ~60% in the Late Silurian, with ~30% H\u2010, and ~10% LL\u2010chondritic grains. In the Late Silurian, primitive achondrite abundances are similar to today&#8217;s value, contrasting to the much higher abundances observed in pre\u2010LCPB mid\u2010Ordovician sediments. &#8220;<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Ellinor Martin, Birger Schmitz, Hans\u2010Peter Sch\u00f6nlaub LINK Meteorit Planet Sci. . doi:10.1111\/maps.13174 &#8220;We present the first reconstruction of the micrometeorite flux to Earth in the Silurian Period. We searched 321 kg of condensed, marine limestone&#8230;<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6,23,24,3157,7,337],"tags":[490,4634,327,4636,321,4635],"_links":{"self":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/16029"}],"collection":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=16029"}],"version-history":[{"count":1,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/16029\/revisions"}],"predecessor-version":[{"id":16030,"href":"https:\/\/karmaka.de\/index.php?rest_route=\/wp\/v2\/posts\/16029\/revisions\/16030"}],"wp:attachment":[{"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=16029"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=16029"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/karmaka.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=16029"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}