Several northwest-trending faults cut across the Little Sur River drainage: the Sur, the Palo Colorado, and the Church Creek faults. The river flows mostly west for much of its length, unlike other rivers in the region which tend to flow to the northwest or southeast. Near Camp Pico Blanco, the river meets the Palo Colorado fault and follows it northwesterly for about , before turning west towards the Pacific Ocean. The lower length of the South Fork follows the Sur fault zone until it meets the North Fork. West of the Sur fault the earth is composed of Franciscan Assemblage rocks, some exposed serpentine, and overlying sandstone. Most of the Little Sur River geology is to the east of the Sur fault. This area is marked by deep canyons cut through granitic and metamorphic rocks of the Salinian Block. Upstream from the Boy Scout camp the gorges are full of mica schist and gneiss (metamorphosed sedimentary rocks), and granodiorite, quartz monzonite, and quartz diorite (granitic rocks). At the river's mouth are some of the largest sand dunes on the Big Sur coast.