  We present direct spectroscopic modeling of 11 high-S/N observed spectra of
the Type Ia SN 2010kg, taken between -10 and +5 days with respect to B-maximum.
The synthetic spectra, calculated with the SYN++ code, span the range between
4100 and 8500 \r{A}. Our results are in good agreement with previous findings
for other Type Ia SNe. Most of the spectral features are formed at or close to
the photosphere, but some ions, like Fe II and Mg II, also form features at
~2000 - 5000 km s$^{-1}$ above the photosphere. The well-known high-velocity
features of the Ca II IR-triplet as well as Si II $\lambda$6355 are also
detected.
  The single absorption feature at ~4400 \r{A}, which usually has been
identified as due to Si III, is poorly fit with Si III in SN 2010kg. We find
that the fit can be improved by assuming that this feature is due to either C
III or O II, located in the outermost part of the ejecta, ~4000 - 5000 km
s$^{-1}$ above the photosphere. Since the presence of C III is unlikely,
because of the lack of the necessary excitation/ionization conditions in the
outer ejecta, we identify this feature as due to O II. The simultaneous
presence of O I and O II is in good agreement with the optical depth
calculations and the temperature distribution in the ejecta of SN 2010kg. This
could be the first identification of singly ionized oxygen in a Type Ia SN
atmosphere.
