A 3.3-Ma impact in Argentina and possible consequences

Enigmatic glassy materials (escorias) and red bricklike materials (tierras cocidas) occur at a restricted stratigraphic Level (the top of the Chapadma lal Formation). Materials from one Locality near Mar del Plata are attribut ed to a mid-Pliocene impact event with a radiometric and magnetostratigraph ic age of 3.3 million years ago (Ma), An extinction of endemic fauna (inclu ding the glyptodonts and flightless cariamid birds) correlates with the uni t containing the impact glasses, Moreover, the age of the glasses is coinci dent within dating uncertainties with a pulselike change in the oxygen isot ope marine record in the Atlantic and Pacific Oceans just before the tate P liocene deterioration of the climate.