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Stratigraphy and Depositional History of the Pantano Formation (Oligocene-Early Miocene), Pima County, Arizona
AuthorBalcer, Richard Allen
Basin and Range Province
Pima County Arizona
Geology, Stratigraphic -- Miocene
Geology, Stratigraphic -- Oligocene
Sedimentation and deposition -- Arizona -- Cienega Gap Region
Sedimentation and deposition -- Arizona -- Pima County
AdvisorSchreiber, J. F. Jr.
Committee ChairSchreiber, J. F. Jr.
MetadataShow full item record
PublisherThe University of Arizona.
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AbstractThe Pantano Formation comprises 1,250 m of alluvial, fluvial, lacustrine, and volcanic rocks deposited in a basin formed in response to regional extension during mid- Tertiary time in southeastern Arizona. During deposition, the locations and composition of sediment source areas varied as contemporaneous uplift occurred adjacent to the basin. The lower half of the formation was deposited as alluvial fans that prograded northward, westward, and southward; the upper half was deposited during southwestward retreat of alluvial fan deposition and the onset of lacustrine deposition. An andesite flow separates the two depositional regimes. Radiometric dates of 24.4 ± 2.6 m.y. B.P. for the andesite and 36.7 ± 1.1 m.y. B.P. for a rhyolitic tuff disconformably underlying the formation indicate that deposition occurred during Oligocene to early Miocene time. Proper stratigraphic sequencing and description, paleocurrent analysis, and gravel provenance study aided in understanding the depositional history of the formation.
Degree ProgramGraduate College