The Upper Cretaceous (?) Colombier volcanic sequence, which is the oldest exposed rock in the Terre-Neuve Mountains, is unconformably overlain by Upper Cretaceous sediments, and both of these rocks have been intruded by the 66.2 m.y. old Terre-Neuve quartz monzonite stock. This entire sequence is overlain unconformably by Paleocene and Eocene limestone, which has been intruded by a small, hypabyssal basalt pluton. Left-lateral, strike-slip faulting, previously unrecognized in northern Haiti, has offset parts of the area by more than 2 km. Although the Terre-Neuve stock and Colombier volcanic rocks are closely associated in space and time, subtraction diagrams suggest that they are not directly related by crystal-melt equilibria and are therefore not strictly consanguineous. Plots of Na2O versus K2O and plagioclase versus K-feldspar for intrusive rocks of the Greater Antilles indicate that the Terre-Neuve stock is among the most granitic of this group. Also, the Terre-Neuve igneous series (including the Colombier volcanic rocks) contains substantially less A12O3 than rock series from both oceanic and continental orogenic zones, as illustrated by differentiation index diagrams.
The age and mineral content of the igneous rocks of northern Haiti plotted on a Qz-Cpx-Ol-Ne tetrahedron indicate that these rocks have become increasingly subsilicic and alkalic with time. This range of rock compositions could have resulted from mantle-generated crystal-melt diapirs that lost most of their crystals (thereby fixing the melt compositions) at the crust-mantle boundary, which migrated downward with time. The spacial variation in magma composition in Hispaniola suggests that the Americas plate originally underthrust the Caribbean plate from the north rather than from the east as presently observed.