The huge supergiant shell ( SGS ) LMC 4 , next to the giant H ii region 30 Doradus the second most impressive feature of the Large Magellanic Cloud ( LMC ) , has been the subject of many studies and was used to test various models of star forming mechanisms .

In this paper we present a B,V photometry of the very centre of this SGS .
The new data yield an age of 11 ( 2 ) Myr and a B - V excess of 0.10 ( 3 ) mag .
Additionally , the two clusters near the geometric centre are too old to be related to the formation of LMC 4 : HS 343 being \sim 0.1 Gyr and KMHK 1000 being \sim 0.3 Gyr of age .
This and existing photometries support that the young stellar population covering the entire inner region is nearly coeval .

We compare these findings with predictions of models proposed for the creation mechanism of SGSs .
We conclude that the large-scale trigger , necessary to explain the observations , comes from hydrodynamic interaction of the galactic halo with gas in the leading edge of the moving LMC .