The St. Anthony Complex consists of the White Hills Peridotite (the ultramafic remnant of an ophiolite), and an underlying metamorphic aureole which grades from metagabbro and hornblende granulite through amphibolite, epidote amphibolite, and greenschist into undeformed volcanic rocks at the base of the sequence. The petrology and mineralogy of the complex show that the basal peridotite mylonites recrystallized at 900–950 °C, the coronitic metagabbros at 850–900 °C, two-pyroxene amphibolites at 860 °C, marbles at 680 °C, epidote amphibolites at 550–650 °C, and greenschists at 350–550 °C. The metamorphic pressures range from 7–10 kb at the peridotite contact to 3–5 kb in the greenschists and amphibolites, and less than 2 kb in the volcanics. The geology suggests that the metamorphic rocks originally formed from a strip of turbidites, alkali basalts, tholeiites, and gabbros adjacent to a continental margin. This sequence was subjected to dynamothermal metamorphism resulting from a combination of conduction of heat from the overlying ultramafic rocks and shear heating. The rocks were gradually accreted onto the base of the overriding ophiolite sheet, forming the composite metamorphic sequence now observed.