A series of widely spaced, scattered dykes, up to a metre thick, are aligned northeast-southwest and cut variable Precambrian gneisses. Rock types represented include nepheline-phyric tinguaite, porphyritic shonkinite and monchiquite.
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Itanhaem is a series of biotite tinguaite dykes cutting shield rocks. In the same area dykes of olivine sovite are reported.
This is a small dyke of porphyritic shonkinite with phenocrysts of biotite, aegirine-augite, apatite and orthoclase, in a groundmass of the same minerals plus nepheline. Weathered syenitic rocks also outcrop.
Dykes exposed in a railway cutting south of Tatui are shonkinites similar to those of Piedade (025-00-097).
A stock of less than 1 km2 forms the hill of Sao Joao and is surrounded by Recent sediments which obscure the contacts. The principal rocks are biotite pulaskite and nordmarkite, the latter containing quartz; both rock types include amphibole and a diopsidic pyroxene.
The small intrusion of Jaboticabal is emplaced in Cretaceous basalts. To the west and northwest near Aparecida de Monte Alto, Taiuva and Piranji alkaline lavas up to 15 m thick intercalated in sandstones of the Bauru Group have been encountered in drill holes.
This island of less than 2 km2 consists of nepheline syenite, pulaskite and syenite, with or without quartz and with gradational boundaries between them. Modal nepheline increases from east to west and its concentration indicates a submerged nepheline syenite centre 1 km west of the island.
This is an island of 7.5 km2, 90% of which is occupied by syenite and quartz syenite, the northwestern part being of Precambrian gneisses and hypersthene charnockites.
Four poorly exposed, stock-like bodies occupy about half the island and cut Precambrian gneisses and granites and some large basaltic dykes.
The island of Monte de Trigo is 1.2x1.3 km, 90% of which is foyaite and the rest melatheralite with minor olivine gabbro, jacupirangite, teschenite and essexite. The foyaite consists of alkali feldspar, nepheline (2-11%), barkevikite, aegirine-augite and a little biotite, sodalite or analcime.