THE HALO INFALL TIMESCALE

There is an accumulating body of observational evidence which seems to support the view that the duration of the phase of star formation and nucleosynthesis activity in the halo of our Galaxy may have been of t he order of 2-3 x 10(9) years. Such evidence arises from abundance det erminations for metal-deficient field halo stars and globular cluster stars, as well as from age determinations for the local white dwarf po pulation and for the halo and disk populations of globular clusters. W e briefly review these diverse observational constraints on the timesc ale of halo evolution and discuss some possible implications for dynam ical models for the collapse of the halo and the onset of star formati on activity in the Galactic disk.