Abstract-Calcite crystals within the Kaibab limestone in Meteor Crater, Arizona, are examined to understand how calcite is deformed during a meteorite impact. The Kaibab limestone is a silty finegrained and fossiliferous dolomudstone and the calcite crystals occur as replaced evaporite nodules with impact-induced twinning. Twinning in the calcite is variable with deformational regimes based on abundances of crystals with twins and twin densities within crystals. The twins are similar to those that are seen in low tectonically deformed regimes. Low levels of shock are inferred from minor peak broadening of the X-ray diffraction patterns (XRD) of the calcite crystals. In addition, electron spin resonance (ESR) spectroscopy data also indicates low shock levels (<3.0 GPa). Quantitative shock pressures and correlation between the XRD and ESR results are poor due to the inferred low shock levels in conjunction with the analytical error associated in calculation of the shock pressures.
Four measured sections of the Late Ordovician-Early Silurian Mount Kindle Formation near Norman Wells, Northwest Territories indicate this unit was deposited on a shallowly dipping carbonate ramp that was subsequently dolomitized. The most shoreward facies are
tidal flats that pass basinward into skeletal packstone-grainstone deposited on the ramp crest. Basinward of the ramp crest are burrowed skeletal wackestone-packstone passing downramp into skeletal wackestone or mudstone with nodular chert. The abundance of macrofauna (corals, stromatoporoids,
brachiopods, bryozoans, sponges, and crinoids) in this unit indicates that it formed in warm water. The majority of the macrofauna was silicified postdepositionally. Preliminary conodont analysis indicates the base of the Mount Kindle Formation is Late Ordovician (Katian). There is a marked faunal
change at a lithological break between shallow-water open-marine skeletal packstone and overlying cherty skeletal mudstone interpreted to be the Ordovician-Silurian unconformity that subdivides the Mount Kindle Formation into two separate sequences.
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