The results of extensive nonequilibrium molecular dynamics simulations of transport of a supercritical fluid mixture through a carbon nanopore, in the presence of an external pressure gradient, are reported. If the downstream pressure is large enough, a pore packing phenomenon occurs in which several layers of the fluids fill the pore. We also find that the fluid molecules form dynamic clusters that travel the length of the pore, with cluster sizes that oscillate with the time. In addition, the simulations indicate that there may be an optimal pore size and an optimal applied pressure gradient for maximum separation of a supercritical fluid mixture into its components. (C) 2003 American Institute of Physics.