Cabrillo National Monument: Geologic resources inventory report
KellerLynn K. 2018. Cabrillo National Monument: Geologic resources inventory report. Natural Resource Report. NPS/NRSS/GRD/NRR—2018/1666. National Park Service. Fort Collins, Colorado
This GRI report was written for resource managers at Cabrillo National Monument to support science-informed decision making. It may also be useful for interpretation. This report is accompanied by three GRI GIS data sets: (1) cabr_geology.mxd was compiled from a 1:100,000-scale source map by Kennedy and Tan (2008). That data set includes both “onshore” and “offshore” geology. (2) polm_geology.mxd was compiled from a 1:24,000-scale source map by Kennedy (1975). It shows the geology of the Point Loma quadrangle; it does not include offshore geology. (3) plhz_geology.mxd was compiled from a 1:24,000-scale source map by Tan (1995); it shows landslide susceptibility and landslide distribution on the Point Loma peninsula. The report was prepared using available geologic information, including the aforementioned source maps by the California Geological Survey. The NPS Geologic Resources Division conducted no new fieldwork in association with the preparation of this report. Resource managers may find Geological Monitoring (Young and Norby 2009) useful for addressing geologic resource management issues discussed in this report. The manual provides guidance for monitoring vital signs—measurable parameters of the overall condition of natural resources. Each chapter covers a different geologic resource and includes detailed recommendations for resource management, suggested methods of monitoring, and case studies. The monument is located 8 km (5 mi) southwest of downtown San Diego, California, and was established in 1913 to memorialize Juan Rodriguez Cabrillo and his 1542 voyage of exploration. The monument was initially administered by the US War Department; it was transferred to the National Park Service in 1933. The monument is at the southern end of Point Loma, which is a north–south-oriented peninsula that separates San Diego Bay on the east from the Pacific Ocean to the west. In addition to the National Park Service, four other land holders—listed alphabetically, the City of San Diego (Point Loma Wastewater Treatment Plant), US Coast Guard (Point Loma Light Station), US Department of Veterans Affairs (Fort Rosecrans), and US Navy (Naval Base Point Loma)—share responsibility of protecting and restoring Point Loma as part of the Point Loma Ecological Conservation Area (PLECA). The monument contains rare natural and cultural resources. The historic lighthouse rests on very old paralic (shoreface) deposits that accumulated atop a wave-cut platform about 855,000 years ago. During the Quaternary Period (the last 2.6 million years), regional uplift associated with the Rose Canyon fault zone raised the platform and associated sediments, which together constitute one of three marine terraces at the monument; the other two terrace levels are younger and lower in elevation but still above the present-day shoreline. These young marine terraces are much less lithified than the monument’s bedrock and thus form hillslopes rather than cliffs. Upper Cretaceous (100 million–66 million years ago) rocks make up the monument’s bedrock. Sand, silt, and cobble that compose these rocks were deposited in a huge submarine fan that spread onto the floor of the Pacific Ocean into water as much as 1,000 m (3,300 ft) deep. Sediment in the fan came from the ancestral Peninsular Ranges to the east and was transported by west-flowing rivers to the shoreline then by sediment gravity flows down the submarine fan. Subsequent tectonic deformation associated with faulting has uplifted these rocks above sea level, where they now form the substrate of the monument.
- Type
- Published Report
- Authors
- KellerLynn, Katie
- Date of Issue
- 2018-06
- Publisher
- National Park Service
- Units
- CABR , GRD , GRI , MEDN , NRSS
- Keywords
- Aeolian Features and Processes, and Fossils, and Other Coastal Features, and Protection, CABR, Cabrillo National Monument, California, Cave Resource Management, Climate Change Planning, Cretaceous Rocks and Fossils, Dredging, Earthquakes, Faults, Geologic Features, Geologic History, Geologic Processes, Geologic Resource Management Issues, Geologic Resources Division, Geologic Resources Inventory, GRD, GRI, Iron Pisoliths, Map Unit Properties Table, Map Units, Marine Terraces, Monitoring, Monitoring the Physical Environment of Tidepools, National Park Service, NPS, Offshore Geology, Old Point Loma Lighthouse, Paleogeographic Setting, Paleontological Resource Inventory, Resource Management, Sea Caves, Sea Cliff Erosion, Sea Cliffs, Slope Hazards, Tidepools, Unconformities, Uplift
- Subjects
- Ecological Framework: Geology and Soils | Geomorphology | Hillslope Features and Processes , Ecological Framework: Geology and Soils | Geomorphology | Coastal/Oceanographic Features and Processes , Ecological Framework: Geology and Soils | Geomorphology | Marine Features and Processes , Ecological Framework: Geology and Soils | Subsurface Geologic Processes | Cave/Karst Features and Processes , Ecological Framework: Geology and Soils | Subsurface Geologic Processes | Seismic Activity , Ecological Framework: Geology and Soils | Paleontology | Paleontology