An oscillator includes a resonator, which has an inertial mass returned by an elastic return and carries entry and exit pallets cooperating with teeth of an escape wheel each provided with a magnet. Each pallet includes a magnetic arrangement, with an annular sector, centred on the axis of oscillation of the resonator, defining a first magnetic barrier area extending above and/or below a mechanical pallet-stone of the entry pallet or exit pallet, over the entire length of this mechanical pallet-stone acting as support for the teeth during the supplementary arc, in order to form a magnetic cylinder escapement mechanism.