CICTERRA 20351
CENTRO DE INVESTIGACIONES EN CIENCIAS DE LA TIERRA
Unidad Ejecutora - UE
artículos
Título:
Cosmic spherules from the Ordovician of Argentina
Autor/es:
V.OLDMAN G.G.; GENGE G.L.; ALBANESI G.L.; BARNES C.R.; ORTEGA G.
Revista:
GEOLOGICAL JOURNAL (CHICHESTER)
Editorial:
JOHN WILEY & SONS LTD
Referencias:
Lugar: Chichester; Año: 2012 vol. 48 p. 222 - 235
ISSN:
0072-1050
Resumen:
The discovery of magnetic spherules in acid-insoluble residues from conodont samples encouraged a systematic search for Ordovicianmicrometeorites from northwestern Argentina. Some 220 melted micrometeorites were recovered from the magnetic fraction of six samples(total rock weight: 23 kg) from the Cordillera Oriental (Santa Rosita Formation) and 17 from five samples (total rock weight: 8.9 kg) from theArgentine Precordillera (Las Aguaditas, Gualcamayo and Las Vacas formations). The specimens resemble I-type cosmic spherules, in theirchemistry and distinct dendritic and polygonal crystalline structures. They represent a flux of micrometeorites several orders of magnitudegreater than present. The wide differences in spherule abundance between the Precordillera and the Cordillera Oriental samples could reflectuncertainties in the sedimentary rates or temporal variations in the flux of extraterrestrial matter to Earth. The micrometeorite-bearingformations span the late Tremadocian to the late Darriliwian (~480460 Ma), which is consistent with a period of elevated flux ofextraterrestrial material, as recorded several thousand kilometres away from coeval horizons in Scotland, Sweden and central China.
