  The mSUGRA parameter space corresponding to light sleptons well within the
reach of LHC and relatively light squarks and gluinos (mass $\le$ 1 TeV) has
three regions consistent with the WMAP data on dark matter relic density and
direct mass bounds from LEP 2. Each region can lead to distinct leptonic
signatures from squark-gluino events during the early LHC experiments
(integrated luminosity $\sim 10 ~fb^{-1}$ or even smaller). In the much studied
stau-LSP coannihilation region with a vanishing common trilinear coupling
($A_0$) at the GUT scale a large fraction of the final states contain electrons
and / or muons and $e$ - $\mu$ - $\tau$ universality holds to a good
approximation. In the not so well studied scenarios with non-vanishing $A_0$
both LSP pair annihilation and stau-LSP coannihilation could contribute
significantly to the dark matter relic density for even smaller squark-gluino
masses. Our simulations indicate that the corresponding signatures are final
states rich in $\tau$-leptons while final states with electrons and muons are
suppressed leading to a violation of lepton universality. These features may be
observed to a lesser extent even in the modified parameter space (with non-zero
$A_0$) where the coannihilation process dominates. We also show that the
generic $m$-leptons + $n$-jets+ $\not! E_T$ signatures without flavour tagging
can also discriminate among the three scenarios. However, the signals become
more informative if the $\tau$ and $b$-jet tagging facilities at the LHC
experiments are utilized.
