Geology

The coastline of the shire is dominated by the Cattamarra Coal Measures, formed during the Jurassic period from volcanic and sedimentary rocks and consisting of siltstone, shale, claystone, coal and sandstone. Just inland, the underlying geology is the Northampton complex, which consists of migmatitic and paragneiss rocks. Further east, the shire lies on a complex of formations, including the above and Tumblagooda Sandstone, the Yarragadee Formation and Holmwood Shale. Tumblagooda Sandstone consists of fine to coarse grained red-bed sandstone and minor siltstone. The Yarragadee formation was formed during the Jurassic period from volcanic and sedimentary rock and consists of sandstone interbedded with shale. Holmwood Shale was formed during the Permian period from sedimentary and volcanic rock and consists of grey shale and clayey siltstone interbedded with limestone. The north east portion of the shire lies primarily on the Nangetty formation, formed during the Carboniferous-permian period from sedimentary and volcanic rocks and consisting of diamictite, shale and sandstone.

Coastal soils are deep and sandy. Soils to the east consist of sodic subsoils, red loamy duplexes, sandy duplexes and siliceous coloured sands. The red loamy duplexes are often associated with drainage lines in the area. Red shallow loams, red to brown hardpan soils and deep sandy earth  are associated with the undulating plains and breakaways of the shire.

Environment

The shire is located within the Geraldton Hills (GES01) and Edel (YAL01) IBRA sub-regions and is characterised by sandy proteaceous heath, casuarina scrub, and low close acacia shrublands. The Edel subregion is unique because it is a transition zone for flora and fauna between the South West and Carnarvon Bioregions. Patches of Subtropical and Temperate Coastal Saltmarsh can be found in the shire. This is a nationally protected Threatened Ecological Community listed as vulnerable under Australia’s national environment law. The plant, animal and micro-organism community is found in the intertidal zone, often associated with estuaries. The plant community consists mainly of salt-tolerant vegetation (halophytes) including grasses, herbs, reeds, sedges and shrubs. Several Priority Ecological Communities occur in the shire, including Acacia rostellifera and mallee eucalypt Coastal Sands, the plant assemblages of the Moresby Range System and the Frankenia pauciflora shurblands on Tamala Limestone ridges.