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[1] The fireball producing a crater-forming meteorite fall near Carancas, Peru, on 15 September 2007 has been analyzed using eyewitness, seismic, and infrasound records. The meteorite impact, which produced a crater of 13.5 m diameter, is found to have released of order 10 10 J of energy, equivalent to $2-3 tons of TNT high explosives based on infrasonic measurements. Our best fit trajectory solution places the fireball radiant at an azimuth of 82°relative to the crater, with an entry angle from the horizontal of 63°. From entry modeling and infrasonic energetics constraints, we find an initial energy for the fireball to be in the 0.06-0.32 kton TNT equivalent. The initial velocity for the meteoroid is restricted to be below 17 km/s from orbit considerations alone, while modeling suggests an even lower best fit velocity close to 12 km/s. The initial mass of the meteoroid is in the range of 3-9 tons. At impact, modeling suggests a final end mass of order a few metric tons and impact velocity in the 1.5-4 km/s range. We suggest that the formation of such a substantial crater from a chondritic mass was the result of the unusually high strength (and corresponding low degree of fragmentation in the atmosphere) of the meteoritic body. Additionally, the high altitude of the impact site (3800 m.a.s.l) resulted in an almost one order of magnitude higher impact speed than would have been the case for the same body impacting close to sea level.

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Fluvial terraces flank the course of the Bow River for 100 km from the eastern margin of the Rocky Mountain Front Ranges to Calgary and beyond. The terraces are cut predominantly in gravel fill, which ranges in thickness from approximately 10 m in the Calgary area to 3 0 m near the mountain front. Sedimentary structures in the gravels indicate a braided stream sedimentary environment in contrast to the present quasi-stable, sinuous, single-channel form of the Bow River. Radiocarbon dates on ungulate remains from the gravels indicate the main period of fill occurred ca. 11 500-10 000 RCYBP (radiocarbon years before present). Previous workers have postulated that the gravels originated directly as outwash from a glacial advance to or beyond the mountain front. This explanation has been refuted by recent stratigraphic and palynological investigations. A complex nonglaciofluvial origin is proposed for these terraces and the sediments that form them. The last glacial advance to reach the mountain front was well into retreat by as early as ca. 13 400 RCYBP. Spruce and pine forest was established in the Bow River drainage by ca. 10400-10000 RCYBP and glaciers were restricted to high cirques. It is probable that the early period of fill deposition (ca. 11 500-10 000 RCYBP) was initiated when mountain tributary trunk streams of the Bow River were choked with debris-flow-delivered sediment during the construction of paraglacial debris fans and related phenomena. The debris flows were distinctive features of early nonglacial times, when landforms left unstable by ice retreat mass-wasted into the valleys. Paraglacial processes explain the early postglacial history of the Bow drainage and this example provides a model readily applicable to other drainages in formerly glaciated terrain.Des terrasses fluviatiles situkes de chaque cBtk du cours d'eau de la rivikre Bow, occupant une longueur de 100 krn reliant la bordure est des contreforts des Montagnes Rocheuses jusqu'i Calgary et au deli. En gknkral, les terrasses sont sculptCes dans du gravier de remplissage dont I'kpaisseur varie de 10 m dans la rCgion de Calgary i environ 30 m prks du front des montagnes. Des structures sedimentaires dans le gravierrCvklent un milieu de ~Cdimentation form6 de cows d'eau anastomosks contrastant avec le chenal unique actuel, sinueux et quasiment stable, de la rivikre Bow. Les datations au radiocarbone sur des fragments d'ongulks trouv6s dans le gravier indiquent que la pkriode la plus active de dCposition des matkriaux de remplissage a eu lieu il y a environ 11 500 h 11 000 annkes au radiocarbone avant le prksent. On postulait dans les travaux antCrieurs que les graviers onginaient directement d'un Cpandage fluvio-glaciaire associk avec une avancCe glaciaire rejoignant et allant m6me au deli du front des montagnes. Suite h des travaux stratigraphiques et palynologiques rkcents on a rejetk cette interprktation. I1 est maintenant proposk pour expliquer la prksence des terrasses et leurs skdirnents une origine complexe qui ne serait pas fluvio-g...