The anisotropy characteristics of natural fined-grained soils' small-strain stiffness were experimentally studied and interpreted with an effective-stress cross-anisotropic elasticity model. Use of highly precise local instrumentation allowed determining all the five parameters necessary for describing the cross-anisotropic behavior of soil at small-strain levels. Similar techniques and interpretations have so far been applied to uniform sands and clays, but the investigated gradation ranges were fairly limited. In this research, natural samples of Holocene and Pleistocene seabed sediments with a wide range of fines content were tested to study their anisotropic stiffness parameters at small-strain levels. The inherent anisotropy characteristics were further discussed by looking at two more commonly quoted inter-modulus ratios, G_hh/G_vh and E_h′/E_v′. They were found to range 0.9-1.3 and 0.6-1.4, respectively. These ranges are closer to those reported for reconstituted sands than those for clays. There is a possibility that larger particles are more dominant in determining the stiffness anisotropy patterns in non-uniform intermediate soils.