What is the composition of the primary rock outcrop in the Peninsular Ranges?

The primary rock outcrop in the Peninsular Ranges is predominantly composed of gabbro and diorite. These types of rocks are igneous, which means they formed from the solidification of molten material. Gabbro is a coarse-grained rock that typically contains a significant amount of plagioclase feldspar and pyroxene, while diorite, often considered a 'intermediate' rock, has a composition between gabbro and granite, featuring both dark and light minerals.

The geological setting of the Peninsular Ranges includes complex tectonic histories influenced by subduction and other processes that have led to the formation of these igneous bodies. The presence of gabbro and diorite reflects the region's history of magmatic activity, with these rocks often found at depth in the Earth's crust, sometimes as part of intrusive formations.

In contrast, the other options involve sedimentary or metamorphic rocks that are not representative of the primary rock composition in this specific geological range. Sandstone and shale are predominantly sedimentary rocks formed from the accumulation and compaction of sediments. Granite, while a common igneous rock, does not dominate the composition of the Peninsular Ranges; it is more