Ground gravity, magnetic and electromagnetic surveys on a crater on basalt of Bajada del Diablo astrobleme-strewn field

ACEVEDO, R.D.; PREZZI, C.; ORGEIRA, M.J.; ROCCA, M.C.L.; MARTÍNEZ, O.; PONCE, J.F.; CORBELLA, H.; RABASSA, J.; GONZÁLEZ-GUILLOT, M.; SUBÍAS, I.

Casablanca

Encuentro; 77th Annual Meeting of the Meteoritical Society; 2014

The Meteoritical Society

The magnetic anomalies show a circular patternwith magnetic lows (-100 to 500 nT) in the crater?s floor. Furthermore,in the crater?s rims, high-amplitude, conspicuous andlocalized (short wavelength) anomalies, ranging between 2500and -3000 nT, are observed. Such large amplitude and shortwavelength anomalies are not detected out of the crater. For allused frequencies, the electromagnetic profiles show lower apparentelectrical conductivities in the crater?s floor, while the rimspresent notably higher values. The complete Bouguer anomalypresents a relative maximum value of ~ 1 mGal, which correlateswith the crater?s floor. This positive anomaly indicates the existenceof a mass excess below the floor of crater.Considering that all the geological formations described in thearea of the crater correspond to basaltic flows, no density contrastdue to lithological differences should be expected. Therefore, thepositive complete Bouguer anomaly in crater G floor could onlybe satisfactorily explained by means of the anomalous accumulationof blocks of basalts in the rims of the crater. Such accumulationof angular blocks leaves many empty spaces between them,which are filled with air and sand, diminishing the density of thecrater?s rims with respect to the crater?s floors.Magnetic and Bouguer anomalies in the crateron basalt of BdD are characteristic of impact structures.