Complex sentence: Margarita Peak,; and Redonda Mesa, are part of the Santa Margarita Mountains, a subrange of the Santa Anas that extends down to Camp Pendleton and Fallbrook.
Split into simpler sentences: Margarita Peak,; and Redonda Mesa,. The Santa Margarita Mountains, a subrange of the Santa Anas also extends down to Camp Pendleton and Fallbrook.