Bland, PA

Coniglio, J

De Souza Filho, CR

Evers, V

Hough, RM

Jull, AJT

Pierazzo, E

Pinotti, L

Spiral - Imperial College Digital Repository

  THE RIO CUARTO CRATER FIELD RE-VISITED: REMOTE SENSING IMAGERY ANALYSIS AND NEW FIELD OBSERVATIONS.  P.A. Bland1, C.R. de Souza Filho2, R.M. Hough1, E. Pierazzo3, J. Coniglio4, L. Pinotti4, A.J.T. Jull5 and V. Evers6, 1Planetary and Space Sciences Research Institute, The Open University, Milton Keynes MK7 6AA, UK (p.a.bland@open.ac.uk), 2Instituto de Geociências, Universidade Estadual de Campinas, Campinas, Brazil, 3Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721, USA, 4Departamento de Geologia, Universidad Nacional de Rio Cuarto, 5800 Rio Cuarto, Cordoba, Argentina, 5NSF-Arizona AMS Labo-ratory, University of Arizona, 1118 East Fourth St, Tucson, AZ 85721, USA, 6BCG, Devonshire House, Mayfair Place, London W1X 5FH, UK   Introduction:  The Rio Cuarto crater field consists of 10 elongate depressions occurring along a line 30-40km long. It is found in the Pampas of Argentina, north of the city of Rio Cuarto, at ~32°50S, 64°10W, and was first described in detail by Schultz and Lianza [1]. Previously, some of these features had been identi-fied as deflations [2], however, based on the morphol-ogy of the depressions, and recovery of glass and fragments of chondritic meteorite, Schultz and Lianza [1] interpreted the structures as the result of the highly oblique impact of a chondritic body 150-300m in di-ameter. Glass was later shown to have elevated Cr, Ni, and Ir abundances [3,4], a low water content [3], and contained rare shocked quartz grains [3], suggesting that the material was in fact an impactite, and further strengthening the impact argument.  Results and Discussion:  We conducted an exten-sive remote sensing study of the Rio Cuarto site and the surrounding Pampas, using CORONA and EOS Terra-ASTER satellite imagery. Our survey reveals >100 features that bear a strong similarity to those described previously [1], with several >5km in length. We visited >50 of these features (including several of those previously identified [1]) during fieldwork in the area. Similarities indicated by the satellite imagery (elongate scars with high length-to-width ratios and orientations ~NNE-SSW) are confirmed on the ground: rims (occasionally degraded) 3-10m above the plains, and bases 3-10m below the plains are characteristic. In addition, 3 samples of chondrite were recovered from craters D and E (both these craters also yielded abun-dant glass, the largest sample 17x9x6cm), and glass was found in 2 of the new structures following brief searches. The absence of glass at other sites appears to be related to variable preservation of the original sur-face  many features are infilled with lakes, swamp, or dunes, or are cultivated.  Conclusion: Our findings suggest that all the de-pressions (those previously identified [1], and the new features we describe) have a common formation mechanism. Further work is needed to establish the formation mechanism, either exogenic or endogenic, of the Rio Cuarto structures.   Figure 1: Rimmed depressions in the vicinity of Carnerillo (east of craters D and E [1]), from Corona satellite imagery. The image is oriented N-S, and is ~8km from top to bottom.  Acknowledgements: We thank N.A. Artemeva and H.J. Melosh for valuable discussion, and D. Ducast  for assistance in the field.  References: [1] Schultz P.H. and Lianza R.E. (1992) Nature, 355, 234-237. [2] Allione J.L. (1987) Trabajo Final de Licenciatura (unpublished). [3] Schultz P.H., Koeberl C., Bunch T., Grant J. and Collins W. (1994) Geology, 22, 889-892. [4] Aldahan A.A., Koeberl C., Possnert G. and Schultz P.H. (1997) GFF, 119, 67-72. 64th Annual Meteoritical Society Meeting (2001) 5319.pdf

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The Rio Cuarto crater field re-visited: remote sensing imagery analysis and new field observations.

The Rio Cuarto crater field re-visited: remote sensing imagery analysis and new field observations.

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