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Marius Ramirez-Cardona, State University of Hidalgo (Mexico)
Hernando Nuņez del Prado, INGEMMET (Peru)
Jose Machare, INGEMMET (Peru)
Luisa Macedo, INGEMMET (Peru)
Humberto Chirif, INGEMMET (Peru)
Walter Pari, INGEMMET (Peru)
Dafne Ramirez-Mendoza, State University of Hidalgo (Mexico)
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The Carancas impact crater (13-m-diameter) is located in southern Peru, at 16°39'52'' S and 69°02'38'' W, near Titicaca lake, Desaguadero district. The meteorite impact was registered in 15 September 2007, at 11:45 GMT, and created an apparently circular structure lying on the seasonal river bed, called Callacane. The impact structure could not be preserved for much time, since the rain and river water may create weathering and erode the original features. Hence, this study was urgently performed during the dry season (from 09/26/2007 to 09/28/2007).
The impact affected grayish brown soil and Cenozoic continental sedimentary rocks of Puno Group (sandstone and siltstone). Loose and removed fragments of the sedimentary materials occupied the larger part of the ejected material rim (ER). The most distinguishable effect of the classical gravitational collapse after the excavation is the occurrence of some decimeter and meter-sized blocks, scattered along the slope of the inner wall of the rim. On its N/NW arc, the rim attains its height approximately one meter above the original soil level and is higher than in other parts. This contour figures a U-shaped horseshoe structure with an overture or depression to the E/SE.
Crater intersects the phreatic level (PL), which created a groundwater pond in the deepest zone or central part (C) of the geoform. The surface level of water pond is approximately two meters below the highest point of ER. The most elongated axis of the pond is 7.8 meters (NW-SE direction) and the water column is 0.60 m height from the deepest point.
One of the main aims of this work is to present some preliminary results derived from a GPR study. A subsurface interface radar system (EKKO PRO) with 200 and 100 MHz monostatic shielded antennas was used. The lower frequency (100 MHz) was probed to identify deformations (folding) of layering sequences up to 10 m deep. 200 MHz pulse reached a maximum penetration of 4 m, showing buried geomorphologic features at subsurface level. The profiles of the higher frequency revealed the limits of an asymmetrical conical transient cavity filled with removed materials derived from the gravitational collapse. The lower frequency profile shows an upward bending reflector segment (generally situated beneath C in vertical impact models) that clearly presents an offset to N/NE direction. Upward and downward bending segments are very useful to deduce approximately the direction of impact as mentioned in other studies (up- and down-range area). A proper study about the nature of this impact event has been established by combining geometrical and geophysical signatures of the associated geoform. It is proposed that all these features are formed by an oblique impact with an approximate direction NW/SE, originated by a bolide that transferred a part of the motion energy to the target material.
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