Extraterrestrial microspherules from Bajada del Diablo, Chubut, Argentina

ORGEIRA, M.J.; CASTRO, L.N.; GOLDMANN, GA; PREZZI, C.; SILEO, E.; VEGA, DR; FRANZOSI, C; ACEVEDO, R.D.; MARTINEZ, OSCAR A.; RABASSA, J

Geoscience Frontiers

China University of Geosciences

Lugar: Beijing; Año: 2017 vol. 8 p. 137 - 149

1674-9871

The Quaternary infilling of a circular structure located in Bajada del Diablo, Chubut Province, Argentinahas been proposed as a crater strewn field in previous studies. Here we report the finding of about 65microspherules collected in a trench excavated in the center of the structure. The majority of handpickedspecimens are single, but some of them exhibit compound forms. The single specimens arespherical with a mean size of 137 mm, whereas the more complex samples show peduncles and dropshapes. Dendritic crystal growth is recognized in the internal structure of some broken microspherules.Preliminary chemical composition from the surface and center of microspherules was determined byenergy dispersive spectrometry employing EDS. Quantitative EMPA and XRD analysis indicate that themicrospherules are mainly composed of Fe and O with magnetite, Fe with subordinate wüstite.Following consideration of possible anthropogenic and volcanic origins, these spherulites are ascribed toan extraterrestrial input. An accumulation rate of 47 microspherules per m2/yr is estimated for thestudied sediments. This value is two orders of magnitude higher than the reference flux for cosmic dustestimated for the last 1 Ma in the Transantarctic Mountains. The microspherules might have beengenerated as a byproduct of asteroid entry in the atmosphere.