ODESSA IMPACT
CRATER
About 64,000 years ago,
during the Late Pleistocene, an iron meteorite impacted western Texas about 9
to 10 miles southwest of the town of Odessa (Ector County). The resulting
impact crater is about 160-170 meters in diameter. The present crater
floor is only a few meters below the level of the surrounding plain. The
original impact crater was about 30 meters deep. It has since been filled
with fine- to coarse-grained siliciclastic and lithic sediments. It is
currently a dry depression, but a small lake occupied the site in the past.
Large and small fragments of
the impactor have been collected from the Odessa Crater area for decades.
The meteorite is an 4.55 billion year old octahedrite originating from the
asteroid belt between Mars and Jupiter. It is dominated by the minerals
kamacite and taenite (both are Fe-Ni alloys).
Odessa Impact Crater (looking north) - low
oblique aerial photo from the 1950s.
Odessa Impact Crater - schematic
cross-section. The basal crater-filling unit is a very fine-grained
"rock flour", formed by impact pulverizing of target rocks.
Above that is an impact breccia unit and many layers of fine- to coarse-grained
siliciclastic and lithic sediment fill.
Odessa Meteorite - a nice 32-kilogram
individual with well formed regmaglypts (the surficial depressions). This
rock is composed principally of the iron-nickel alloy minerals kamacite
and taenite.
Odessa Impact Crater (looking southwest) - the
small ridge in the distance is uplifted rim rocks along the crater edge.
Odessa Impact Crater (looking NW)
Odessa Impact Crater (panoramic view) - north is
toward the building; the trail at left is looking to the southwest. Photo
provided by Mary Ellen St. John.
The rim rocks at Odessa
Impact Crater have been uplifted and upturned (see cross section on previous
page). These rocks are Lower Cretaceous oncolitic limestones of the
Fredericksburg Group. The oncolites range in shape from subspherical to
irregular.
Odessa Impact Crater rim
rocks
- oncolitic limestones from the Lower Cretaceous Fredericksburg Group.
Odessa Impact Crater rim
rock
- oncolitic limestone from the Lower Cretaceous Fredericksburg Group.
Odessa Impact Crater rim
rock
- oncolitic limestone from the Lower Cretaceous Fredericksburg Group.
The impact breccia deposits
at this site are referred as the Odessa Breccia. The rocks consist of a
mixture of large and small, angular fragments formed by shattering and
pulverizing of target bedrock by the meteorite.
Odessa Breccia (large brownish clast at
left is 3.5 cm across at its widest)
Odessa Breccia (field of view: 28.6 cm
across)
Odessa Breccia