Zygi-Petrini lies in an area dominated by alluvial marly sediment and several carbonate rock (chalk, limestone, etc) outcrops, including the Nicosia, Pachna, and Lefkara formations. These sedimentary rocks are the source of the abundant marl found around Zygi. Cream colored marly clay collected within the site of Zygi is highly calcareous and includes frequent limestone grains and foraminifera. Marls derived from the Nicosia Formation just west of Zygi bear the same natural sand-sized grains, but don’t exhibit the formation of sparry calcite after being fired at temperatures above 500℃. Large dark red clay pellets occur frequently throughout this marl. Foraminifera, cf. Globigerina, some stained with iron, are common. Clinopyroxene, basalt (including pillow lava) and quartz grains are present.
The nearby Vasilikos River deposits Holocene period alluvium around Zygi. Sediment collected from the Vasilikos River includes biotite, mica schist, foraminifera, limestone, pyroxene, chlorite, serpentine, plagioclase feldspar and black opaques. The river's source is the southeast Troodos Mountains, which contributes to the ultramafic black sands that characterize the beaches at the site. Petrographic analyses show that this beach sand is characterized by angular and elongate grains of volcanic material, including pyroxene, basalt, and biotite micas, and abundant fragments of rounded limestone, shell, and microfossils.
