corresponds to maximal distances between star clusters and H[ii]{} regions nearest to them. This spatial scale corresponds to a typical size of a star complex.

Of course, our estimates of the $\log \Delta t - \log \Delta S$ dependency are only qualitative. They are intended to show an agreement between our estimates and the results of previous researchers [@efremov1998; @grasha2017], if we use the classical technique to study the hierarchical star formation in turbulent media based on the study of the $\log \Delta t - \log \Delta S$ dependence for cluster pairs. @efremov1998 and @grasha2017 used cluster ages determined directly. Obviously, our ’photometric’ ages, calculated from the $U-B$ colour, are less reliable.

We did not identify close cluster pairs ($S<100$ pc) in NGC 3726, the most distant galaxy in the sample. Thus, correlation parameters for it were obtained with large errors and are shown in the figure only for a qualitative comparison.

Our results show that the decrease of the mean age difference with the decrease of separation $\Delta S$ for close cluster pairs with $\Delta S<250$ pc is a real physical effect. Age difference distributions for cluster pairs within narrow $\Delta t$ ranges (0.2 dex), which are presented in 