Depth of maximum of extensive air showers and cosmic ray composition above10(17) eV in the geometrical multichain model of nuclei interactions

The depth of maximum for extensive air showers measured by Fly's Eye and Ya kutsk experiments is analysed. The analysis depends on the hadronic interac tion model that determines cascade development. The novel feature found in the cascading process for nucleus-nucleus collisions at high energies leads to a fast increase of the inelasticity in heavy nuclei interactions withou t changing the hadron-hadron interaction properties. This effects the devel opment of the extensive air showers initiated by heavy primaries. The detai led calculations were performed using the recently developed geometrical mu ltichain model and the CORSIKA simulation code. The agreement with data on average depth of shower maxima, the falling slope of the maxima distributio n, and these distribution widths are found for the very heavy cosmic ray ma ss spectrum (slightly heavier than expected in the diffusion model at about 3 x 10(17) eV and similar to the Fly's Eye composition at this energy).