Marañón fold and thrust belt

[note 1] Prior to the deformation and uplift the rocks forming the Marañón fold and thrust belt constituted the fill of a marine back-arc basin that existed in the Mesozoic and was parallel to the present-day coast.

[5] The onset of Andean orogeny first caused the basin to rise and dry up with red beds being deposited in its eastern part.

[4] During deformation Chonta Fault acted as a barrier "damming-up" folded and thrust strata west of it.

[5] The unconformity that cuts across the Marañón fold and thrust belt show the Incaic Phase of the Andean orogeny ended no later than 33 million years ago in the earliest Oligocene.

The most common ore metals in the mineralizations of the belt are zinc, copper, gold, lead, tungsten and silver.