|A Missing Period of Time in the Pt. Reyes Geologic History
Between the formation of the granites and the next geologic evidence in the rock record of the peninsula a large period of time is completely missing. While similar to the "Great Unconformity" in the depths of the Grand Canyon, much less time is missing (only 50 million years?).
The Pre-Cretaceous metamorphic rocks and granitic rocks were uplifted and eroded.
Most of the metamorphic rocks were entirely removed, leaving only patches of the pre-granitic rocks. These patches are sometimes referred to as "roof pendants" and only a few outcrops are available for direct inspection.
Following the uplift and erosion, the granitic and metamorphic rocks were submerged below the sea by the Paleocene and the Pt. Reyes Conglomerate was deposited upon the pre-existing rocks.
Because the rocks are so different in their origins, this type of boundary is referred to as a non-conformity.