
Name: Buzzard Coulee
History:
A bright fireball was widely
observed across Alberta, Saskatchewan and Manitoba during late twilight
on November 20, 2008. The fireball and subsequent dust trail, or shadows
cast by the fireball, were recorded by all-sky and security video
cameras establishing that its brightest portion occurred from 17:26:40
to 17:26:45 MST. The fireball traveled approximately north to south with
an elevation angle of ~60°. Abundant sonic phenomena were reported
including anomalous sounds, explosion booms, sonic booms from individual
fragments and whirring sounds interpreted as produced by individual
fragments falling to ground; the fireball’s explosions were also widely
recorded by Comprehensive Test Ban Treaty infrasound stations
establishing an energy release of approximately one third of a kiloton,
indicating an original meteoroid mass of ~10 tons. Interviews of
eyewitnesses and crude calibrations of security cameras constrained the
fall region and the first search attempt led to meteorites being
recovered off the ice of a manmade pond late on November 27, 2008.
Subsequent searches led to recovery of more than one hundred individual
fragments before December 6 when increasing snow cover made further
searching unproductive. A strewn field at least seven kilometers long
and approximately three km wide with a wind drift tail of an additional
three km eastwards has been crudely outlined.
Physical characteristics:
A total
of 129 well-substantiated pieces totaling ~41 kg have been recovered,
but dozens of additional recovered specimens are indicated. The
meteorites are distinguished by the large number of specimens with
immature ablation surfaces (angular shapes with numerous small
piezoglypts); up-range in the strewn field a larger proportion of mature
ablation surfaces and oriented individuals are found. The fusion crust
is a typical dark gray for an ordinary chondrite fall. The fall is also
distinguished by the large proportion of meteorites that exhibit freshly
broken surfaces with no fusion crust; broken surfaces with variable
amounts of “painting” by fusion crust are also common.
Petrography
(M. Hutson and A. Ruzicka, Cascadia; E. Milley and A. Hildebrand, UCalg):
Most surfaces show no brecciation, but one surface has a slightly
lighter gray angular clast in a uniform gray matrix. Two different
chondrite textures are visible in one thin section, but boundaries
between the two regions are indistinct. One area has welldefined
chondrules. The other region has more opaques with fewer easily visible
chondrules, but has numerous smaller cryptocrystalline chondrules and
chondrule fragments. Another section contains a light colored, coarse
grained, pyroxene-rich inclusion with an igneous texture.
Mineral compositions and geochemistry:
Olivine (Fa17.8 ± 0.3) with PMD Fa = 1.3, low-Ca pyroxene (Fs16.6 ± 0.8, Wo1.87 ± 0.8) with PMD Fs = 3.9, high-Ca pyroxene (Fs12.4 ± 3.3, Wo20.1 ± 11.2). The composition of high-Ca pyroxene is suggestive of pigeonite, but may be an intimate mixture of low- and high- Ca pyroxene.
| State/Prov/County: | Wilton Rural Municipality, Saskatchewan, |
| Date: | 20-Nov-08 |
| Latitude: | 52°59.76?N |
| Longitude: | 109°50.89?W |
| Mass (g): | 41,000 |
| Pieces: | 129 |
| Class: | H4 |
| Shock stage: | S2 |
| Weathering grade: | W0 |
| Fayalite (mol%): | 17.8 |
| Ferrosilite (mol%): | 16.6 |
| Wollastonite (mol%): | 1.9 |
| Classifier: | M. Hutson and A. Ruzicka, Cascadia, E. Milley and A. Hildebrand, UCalg |
| Type spec mass (g): | 39.1 |
| Type spec location: | Ucalg |
| Main mass: | anonymous |



