Upper Oso Dam
Orange County, California33.65917, −117.62917
Can I collect here?
ProSee who owns this land and whether it is claimedPro shows the owner, the claim on this spot and every claim within a mile.
Based on our latest records, with claims updated from the BLM on Oct 9, 2026. Land and claims can change quickly, so check before you go.
Minerals on record here
1 mineralRecorded here: fossil.
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About Upper Oso Dam
Upper Oso Dam is a fossil collection site in Orange, California, cataloged in the Paleobiology Database. Fossils here come from the "Topanga" Formation, dated to the Langhian (15.98–13.82 million years ago). The depositional environment is recorded as marine indet. Documented finds include Equinae, Aepycamelus, Palaeomerycidae, Diomedea milleri, Puffinus priscus, Puffinus.
Geologic setting
- Formation
- "Topanga"
- Geologic interval
- Langhian
- Age
- 15.98–13.82 Ma
- Depositional environment
- marine indet.
- Recorded occurrences
- 37
Locality notes
Oso Creek, Santa Ana Mtns.
Fossils found here
Equinae
Mammalia · Equidae
Aepycamelus
Mammalia · Camelidae
Palaeomerycidae
Mammalia · Palaeomerycidae
Diomedea milleri
Aves · Diomedeidae
Puffinus priscus
Aves · Procellariidae
Puffinus
Aves · Procellariidae
Sulidae
Aves · Sulidae
Mergini
Aves · Anatidae
Panalcidae
Aves · Panalcidae
Carcharodon hastalis
Chondrichthyes · Lamnidae
Cosmopolitodus planus
Chondrichthyes · Lamnidae
Isurus
Chondrichthyes · Lamnidae
Otodus megalodon
Chondrichthyes · Otodontidae
Carcharhinus
Chondrichthyes · Carcharhinidae
Negaprion
Chondrichthyes · Carcharhinidae
Galeocerdo aduncus
Chondrichthyes · Galeocerdonidae
Hemipristis serra
Chondrichthyes · Hemigaleidae
Squalus
Chondrichthyes · Squalidae
Squatina lerichei
Chondrichthyes · Squatinidae
Myliobatis
Chondrichthyes · Myliobatidae
Allodesmus
Mammalia · Desmatophocidae
Neotherium
Mammalia · Odobenidae
Otariidae
Mammalia · Otariidae
Kentriodon obscurus
Mammalia · Kentriodontidae
Zarhinocetus errabundus
Mammalia · Allodelphinidae
Archaeolagus
Mammalia · Leporidae
Leidymys
Mammalia · Cricetidae
Eotaria citrica
Mammalia · Otariidae
Anatinae
Aves · Anatidae
Desmostylia
Mammalia
Cetotheriidae
Mammalia · Cetotheriidae
Puffinus mitchelli
Aves · Procellariidae
Sula willetti
Aves · Sulidae
Diomedea
Aves · Diomedeidae
Records and references
Data: Paleobiology Database collection 19595 (CC BY 4.0) — view the source record
Getting there
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Trip reports
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Questions about Upper Oso Dam
Can you collect at Upper Oso Dam?
It depends on who owns the land and whether a mining claim covers it. BLM land usually allows hand collecting for personal use, national parks allow none, and private land needs the owner’s permission. Pro members see the owner and any claims at this spot.
What minerals are found at Upper Oso Dam?
Fossil.
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Source: Paleobiology Database.