  The radial transport, or drift, of dust has taken a critical role in giant
planet formation theory. However, it has been challenging to identify dust
drift pile ups in the hard-to-observe inner disk. We find that the IM Lup disk
shows evidence that it has been shaped by an episode of dust drift. Using
radiative transfer and dust dynamical modeling we study the radial and vertical
dust distribution. We find that high dust drift rates exceeding 110 M_earth/Myr
are necessary to explain both the dust and CO observations. Furthermore, the
bulk of the large dust present in the inner 20 au needs to be vertically
extended, implying high turbulence alpha_z > 10^{-3} and small grains (0.2-1
mm). We suggest that this increased level of particle stirring is consistent
with the inner dust-rich disk undergoing turbulence triggered by the vertical
shear instability. The conditions in the IM Lup disk imply that giant planet
formation through pebble accretion is only effective outside 20 au. If such an
early, high turbulence inner region is a natural consequence of high dust drift
rates, then this has major implications for understanding the formation regions
of giant planets including Jupiter and Saturn.
