| Titre | Terrestrial impact craters: their spatial and temporal distribution and impacting bodies |
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| Auteur | Grieve, R A F; Pesonen, L J |
| Source | Earth, Moon and Planets vol. 72, 1996 p. 357-376, https://doi.org/10.1007/bf00117541 |
| Année | 1996 |
| Séries alt. | Commission géologique du Canada, Contributions aux publications extérieures 41994 |
| Éditeur | Springer Nature |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.1007/bf00117541 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Région | Monde |
| Lat/Long OENS | -180.0000 180.0000 90.0000 -90.0000 |
| Sujets | cratères; astroblèmes; cratères météoriques; géologie extraterrestre |
| Illustrations | croquis cartographiques; analyses |
| Diffusé | 1996 02 01 |
| Résumé | (disponible en anglais seulement)
The terrestrial impact record contains currently ~145 structures and includes the morphological crater types observed on the other terrestrial planets. It has,
however, been severely modified by terrestrial geologic processes and is biased towards young (= 200 Ma) and large (= 20 km) impact structures on relatively well-studied cratonic areas. Nevertheless, the ground-truth data available from terrestrial
impact structures have provided important constraints for the current understanding of cratering processes. If the known sample of impact structures is restricted to a subsample in which it is believed that all structures = 20 km in diameter (D) have
been discovered, the estimated terrestrial cratering rate is 5.5±2.7 × 10-15km-2a-1 for D = 20 km. This rate estimate is equivalent to that based on astronomical observations of Earth-crossing bodies. These rates are a factor of two higher, however,
than the estimated post-mare cratering rate on the moon but the large uncertainties preclude definitive conclusions as to the significance of this observation. Statements regarding a periodicity in the terrestrial cratering record based on
time-series analyses of crater ages are considered unjustified, based on statistical arguments and the large uncertainties attached to many crater age estimates. Trace element and isotopic analyses of generally siderophile group elements in impact
lithologies, particularly impact melt rocks, have provided the basis for the identification of impacting body compositions at a number of structures. These range from meteoritic class, e.g., C-1 chondrite, to tentative identifications, e.g., stone?,
depending on the quality and quantity of analytical data. The majority of the identifications indicate chondritic impacting bodies, particularly with respect to the larger impact structures. This may indicate an increasing role for cometary impacts
at larger diameters; although, the data base is limited and some identifications are equivocal. To realize the full potential of the terrestrial impact record to constrain the character of the impact flux, it will be necessary to undertake additional
and systematic isotopic and trace element analyses of impact lithologies at well-characterized terrestrial impact structures. |
| GEOSCAN ID | 204531 |
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