Uploaded July 2026 | Updated September 2026, 1 week ago
Arizona geology and fossil hunting come together in this central Arizona rockhounding adventure through ancient TSY basin-fill deposits. We explore desert washes and exposed sediment layers for mudstone, conglomerate, chalcedony, volcanic clasts, and possible Miocene fossils.
On some Arizona geologic maps, TSY is used as shorthand for younger basin-fill units. These deposits can contain gravel, sand, silt, clay, and partially cemented sediment carried down from nearby mountains. By studying TSY geology, washes, road cuts, and exposed stratigraphy, we can begin reconstructing how Arizona’s basins developed over time.
During this Arizona geology field trip, we find fine-grained mudstone that points toward quieter depositional conditions, cemented conglomerate created by higher-energy water movement, an angular volcanic clast, and weathered chalcedony that may have traveled farther through the ancient drainage system.
The most unusual discovery is a tooth-like specimen with complex surface patterns. It may represent part of a fossilized mammal tooth, but because it was found loose in a wash, I cannot confidently identify its species, original layer, or exact age. I carefully document the find and leave it in place rather than removing it.
This video also explains how geologic maps, satellite imagery, stratigraphy, and fresh wash exposures can help with Arizona rockhounding and fossil hunting. We explore the Basin and Range landscape, younger basin-fill deposits, natural caliche and silica cement, and the possibility of finding evidence from the Miocene and later Neogene.
Before collecting rocks or fossils, always verify land ownership and current regulations. Vertebrate fossils may be protected and generally should not be removed from public land without proper authorization. When uncertain, photograph the specimen, record its location, leave it in place, and contact the appropriate land manager.
Subscribe to Will O’s Southwest Studio for more Arizona geology, Arizona rockhounding, lapidary, rock identification, and outdoor Southwest adventures.
#arizonarockhounding #fossilhunting #ArizonaGeology #willorocks
Arizona geology and fossil hunting come together in this central Arizona rockhounding adventure through ancient TSY basin-fill deposits. We explore desert washes and exposed sediment layers for mudstone, conglomerate, chalcedony, volcanic clasts, and possible Miocene fossils.
On some Arizona geologic maps, TSY is used as shorthand for younger basin-fill units. These deposits can contain gravel, sand, silt, clay, and partially cemented sediment carried down from nearby mountains. By studying TSY geology, washes, road cuts, and exposed stratigraphy, we can begin reconstructing how Arizona’s basins developed over time.
During this Arizona geology field trip, we find fine-grained mudstone that points toward quieter depositional conditions, cemented conglomerate created by higher-energy water movement, an angular volcanic clast, and weathered chalcedony that may have traveled farther through the ancient drainage system.
The most unusual discovery is a tooth-like specimen with complex surface patterns. It may represent part of a fossilized mammal tooth, but because it was found loose in a wash, I cannot confidently identify its species, original layer, or exact age. I carefully document the find and leave it in place rather than removing it.
This video also explains how geologic maps, satellite imagery, stratigraphy, and fresh wash exposures can help with Arizona rockhounding and fossil hunting. We explore the Basin and Range landscape, younger basin-fill deposits, natural caliche and silica cement, and the possibility of finding evidence from the Miocene and later Neogene.
Before collecting rocks or fossils, always verify land ownership and current regulations. Vertebrate fossils may be protected and generally should not be removed from public land without proper authorization. When uncertain, photograph the specimen, record its location, leave it in place, and contact the appropriate land manager.
Subscribe to Will O’s Southwest Studio for more Arizona geology, Arizona rockhounding, lapidary, rock identification, and outdoor Southwest adventures.
#arizonarockhounding #fossilhunting #ArizonaGeology #willorocks
