Mount Pleasant Caldera rock. The Intercaldera Sequence comprises formations that crop out from overlying flows in triangularly shaped area, and includes thick volcanic ash (tuff), thick breccia layers, and intermediate to felsic igneous rocks that tend to intrude the above layers and are typically located along caldera margin faults. The Exocaldera Sequence contains ash flow tuffs, mafic lavas, alluvial redbeds, and porphyritic felsic lavas that are distributed across five different layers. The late Caldera-Fill Sequence contains rocks that are similar to those of the outflows of the other, older layers, and comprises two formations and two relatively minor intrusive lava flows. The volcanic
Eoarchean geology highly deformed biotite-hornblende tonalitic to granitic orthogneiss. Subordinate mafic amphibolitic and chloritic elliptical enclaves and inclusions are observed in felsic gneisses.Although the rocks are highly deformed and could not reflect the original field relation between rock units, the chemical composition of the rocks showcases how Eoarchean greenstone-TTG be like. Chemical composition in the mafic inclusion suggests the acasta area was possibly a supra-subduction setting. Dominant felsic rocks are composed of highly deformed tonalitic, granodioritic and granitic gneisses. Inclusion of as early as 4.2 billion years old zircon core are observed in the gneisses. Mafic rocks, i.e. subordinate amphibolite and ultra