| The Vargeao impact dome structure is located S 26° 50' and W 52 07' in Santa Catarina state, Brazil. The 11 km structure is defined by concentric hills in a topographic depression with a central uplift. Shock produced planar features have been identified in quartz pebbles in the lithology associated with the central uplift. Two types of planar features have been identified, planar fractures (PFs) and planar deformation features (PDFs), of which the latter is uniquely produced by shock waves associated with meteorite impacts. The PFs are most commonly parallel to the c (0001) and the PDFs are most commonly parallel to the r,z {lcub}1011{rcub}, s{lcub}1121{rcub}, pi{lcub}1012{rcub}, and _{lcub}2131{rcub} crystallographic plane in quartz. Field studies and sample analyses of breccias and fractured basalts, sandstones, and fractured quartz pebbles and possible pseudotachylites with the structure constrain estimates of shock pressures throughout the structure to a maximum of 30 GPa. |
