Bajada del Diablo impact crater-strewn field: the largest crater field in the Southern Hemisphere.

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

París

Congreso; 8th IAG International Conference on Geomorphology; 2013

IAG

Recent remote sensing analyses and field studies have shown that Bajada del Diablo, in Argentine Patagonia, is a huge, new crater strewn field. The Bajada del Diablo astrobleme-strewn field is a domain of enigmatic circular structures located in central Patagonia. Four different impact areas are herein described, investigated, mapped, and geo-referenced. A single, blurred crater dispersion ellipse has been identified. A total of 185 circular structures (some of which are partially obliterated by erosion or sediment accumulation), were identified by remote sensing techniques, but many have been evaluated in situ and interpreted as impact craters. Moreover, two of the structures have been surveyed in detail in the field using a total station instrument. The crater-type structures have diameters ranging from 100 to 500 m in width and 30 to 50 m in depth. The four impact crater fields were formed simultaneously, impacting upon a Miocene basaltic plateau and Pliocene?Early Pleistocene pediments. The original crater field was later eroded by Late Pleistocene fluvial processes, isolating the different areas. The rocks within the craters have strong and stable magnetic signature. No meteorite fragments or other diagnostic landmarks have been found yet. The origin of these crater fields may be related to multiple fragmentation of one asteroid that broke up before impact, perhaps traveling across the space as a rubble pile. Alternatively, multiple collisions of comet fragments could explain the crater formation. Other preliminary observations on collected samples (glass, breccias, and, most relevant, Fe-Ni-bearing spherules found within the impacted zones) are herein discussed. Based on field geological and geomorphological data, the age of this event is estimated to be bracketed between Early Pleistocene and the beginning of Late Pleistocene (i.e., 0.78?0.13 Ma ago).