  The Galaxy Mass Assembly ultra-deep Spectroscopic Survey samples a part of
the CDFS to unprecedented depth. The resulting distribution of 150 z>1.4
redshifts reveals a significant peak at z=1.6, part of a larger overdensity
found at this redshift. The 42 spectroscopic members of this structure, called
Cl 0332-2742, form an overdensity in redshift of a factor 11+/-3 and have a
velocity dispersion of 450 km/s. We derive a total mass for Cl 0332-2742 of
~7x10^14 Msol. The colours of its early-type galaxies are consistent with a
theoretical red sequence of galaxies with stars formed at z=3.0. In addition,
there are more massive, passive and older, but less star forming galaxies in CL
0332-2742 than in the field. We conclude that this structure is a cluster under
assembly at z=1.6.
