CHAPTER IV 



GEOLOGY OF POINT LOBOS * 



The "record of the rocks" at Point Lobos, where the forces of surf and 

 weather have for countless centuries battered the edge of the continent, 

 reveals a story of many chapters. 



Rocks on Point Lobos show varied conditions of origin. The granite 

 (granodiorite), once cooled from a molten mass of rock far below the sur- 

 face, has been raised up and exposed on Cypress Headland. Fragments 

 worn or broken from it and from other rocks were heaped in layers as sand 

 and gravel along the shore, and have since been cemented into rock which 

 we call sandstone and conglomerate. Occasional fossils found in these sedi- 

 ments indicate that they were laid down in the sea. More recently, as a part 

 of mountain-making which produced the California Coast Ranges, all of 

 these rocks have been folded, and subjected to erosion until Point Lobos 

 as we know it has been carved out by waves, wind, and rain. 



Some of the more important events in the geologic history of Point Lobos 

 Reserve, in the order of their happening, include : 



1. Deposition of an extensive series of rocks, probably mainly sedimen- 

 tary, of which now no remnants are left in the park. These may have been 

 deformed and altered before the intrusions of the granodiorite. 



2. Intrusion of the Santa Lucia granodiorite with accompanying contact 

 metamorphism superheating the surrounding sediments by molten rock. 



3. Elevation, which may or may not have occurred at the time of the 

 intrusion, followed by long-continued erosion which removed entirely the 

 altered sedimentary rocks above the granodiorite and cut deeply into it. 



4. Deposition of the Carmelo formation, at least partially under marine 

 conditions. At the same time older (Cretaceous) sediments and granitic 

 rocks were probably undergoing erosion on adjacent highlands. 



5. Deposition of Miocene (Middle Recent) marine sediments along the 

 coast. This deposition continued locally to the south on the borders of the 

 Santa Lucia Range into Pliocene time. 



6. Deformation accompanied by strong shearing took place probably 

 some time during the Pliocene. The history of adjacent regions indicates 

 that deformation occurred intermittently through the Pliocene and prob- 

 ably continued into the early Pleistocene (Ice Age). 



7. Erosion of the region with the development of something approaching 

 the present topography, probably mainly by streams and wind. 



8. Depression of the area beneath the sea and then emergence which was 

 intermittent rather than gradual in its character. At certain periods the 

 sea level must have been relatively stable to permit the cutting of rather 

 broad terraces, each of which tended to remove traces of the previous ones. 

 Finally there has been cut the terrace which is still beneath the sea and 

 which is still being eroded. 



• By Ralph \V. Chaney, Profe.ssor of Paleontology, University of California ; Research Asso- 

 ciate, Carnegie Institution of Washington ; and R. A. Bramkamp, Research Assistant, 

 Paleontology, University of California. 



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