  Magnetic reconnection has been observed in the transition region of
quasi-parallel shocks. In this work, the particle-in-cell method is used to
simulate three-dimensional reconnection in a quasi-parallel shock. The shock
transition region is turbulent, leading to the formation of reconnecting
current sheets with various orientations. Two reconnection sites with weak and
strong guide fields are studied, and it is shown that reconnection is fast and
transient. Reconnection sites are characterized using diagnostics including
electron flows and magnetic flux transport. In contrast to two-dimensional
simulations, weak guide field reconnection is realized. Furthermore, the
current sheets in these events form in a direction almost perpendicular to
those found in two-dimensional simulations, where the reconnection geometry is
constrained.
