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Miocene Teleost Fish From Chino Hills: Preliminary Results From The Vila Borba Project, San Bernardino County, CA


The Vila Borba Project is a 336-acre residential and commercial development in the city of Chino Hills, San Bernardino County, California. Phase I began in early 2014, with archeological and paleontological monitoring provided by DUKE Cultural Resources Management. Phase I involved the northwest portion of the project, an area roughly bisected by the northwest-southeast trending Chino Fault. This area has been previously mapped as comprising the late Miocene (Late Luisian to Delmontian) Puente and Sycamore Canyon Formations. In five months of monitoring, over 160 fossils specimens were found, including teleost fish, chondrichthians, bivalves, marine and land plants, corprolites, and burrows. Preliminary investigation of the teleost fish specimens identified Chauliodus sp. (viperfish), Etringus sp. (round herring), Laytonia sp. (halosaur), Rhythmias sp. (sheepshead), Clupeiformes (herring and anchovy), and Myctophiformes (lanternfish). The sedimentology of the bedrock and the presence of fossils were distinctly different on either side of the Chino Fault. East of the fault (footwall), sediments were dominated by pebble to boulder conglomerates and sandstones, and relatively few fossils were observed. West of the fault (hanging wall), sediments were exclusively mudstones to very fine-grained sandstones, and the majority of fossils were encountered. The difference in fossil exposure in sedimentology on either side of the Chino Fault may reflect taphonomic differences within the same formation, or may signify a more complex geology in the project area than is currently mapped. Further phases in the Vila Borba Project may clarify the local geology and their respective fossil deposits.