  High-resolution simulations of cosmological structure formation indicate that
dark matter substructure in dense environments, like groups and clusters, may
survive for a long time. These dark matter subhalos are the likely hosts of
galaxies. We examine the small-scale spatial clustering of subhalo major
mergers at high redshift using high-resolution N-body simulations of
cosmological volumes. Recently merged, massive subhalos exhibit enhanced
clustering on scales ~100-300 kpc/h, relative to all subhalos of the same
infall mass, for a short time after a major merger (< 500 Myr). The small-scale
clustering enhancement is smaller for lower mass subhalos, which also show a
deficit on scales just beyond the excess. Halos hosting recent subhalo mergers
tend to have more subhalos; for massive subhalos the excess is stronger and it
tends to increase for the most massive host halos. The subhalo merger fraction
is independent of halo mass for the scales we probe. In terms of satellite and
central subhalos, the merger increase in small-scale clustering for massive
subhalos arises from recently merged massive central subhalos having an
enhanced satellite population. Our mergers are defined via their parent infall
mass ratios. Subhalos experiencing major mass gains also exhibit a small-scale
clustering enhancement, but these correspond to two-body interactions leading
to two final subhalos, rather than subhalo coalescence.
