The Neogene drainage history of south-central Idaho

Jurassic sedimentary rocks of southern to central Quesnellia record the history of the Quesnellian magmatic arc and reflect increasing continental influence throughout the Jurassic history of the terrane. Standard petrographic point counts, geochemistry, SmNd isotopes and detrital zircon geochronology, were employed to study provenance of rocks obtained from three areas of the terrane. Lower Jurassic sedimentary rocks, classified by inferred proximity to their source areas as proximal or proximal basin are derived from an arc source area. Sandstones of this age are immature. The rocks are geochemically and isotopically primitive. Detrital zircon populations, based on a limited number of analyses, have homogeneous Late Triassic or Early Jurassic ages, reflecting local derivation from Quesnellian arc sources. Middle Jurassic proximal and proximal basin sedimentary rocks show a trend toward more evolved mature sediments and evolved geochemical characteristics. The sandstones show a change to more mature grain components when compared with Lower Jurassic sedimentary rocks. There is a decrease in εNdT values of the sedimentary rocks and Proterozoic detrital zircon grains are present. This change is probably due to a combination of two factors: (1) pre-Middle Jurassic erosion of the Late Triassic Early Jurassic arc of Quesnellia, making it a less dominant source, and (2) the increase in importance of the eastern parts of Quesnellia and the pericratonic terranes, such as Kootenay Terrane, both with characteristically more evolved isotopic values. Basin shale environments throughout the Jurassic show continental influence that is reflected in the evolved geochemistry and SmNd isotopes of the sedimentary rocks. The data suggest southern Quesnellia received material from the North American continent throughout the Jurassic but that this continental influence was diluted by proximal arc sources in the rocks of proximal derivation. The presence of continent-derived material in the distal sedimentary rocks of this study suggests that southern Quesnellia is comparable to known pericratonic terranes.

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Deglaciation and Postglacial Vegetation History of the West Mountains, West-central Idaho, U.S.A.

Arctic Antarctic and Alpine Research ◽

10.1080/15230430.1999.12003313 ◽

1999 ◽

Vol 31 (3) ◽

pp. 303-311 ◽

Cited By ~ 2

Author(s):

James P. Doerner ◽

Paul E. Carrara

Keyword(s):

Vegetation History ◽

The West ◽

West Central ◽

History Of ◽

Central Idaho

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:Slavery and Beyond: The Making of Men and Chikunda Ethnic Identities in the Unstable World of South‐Central Africa, 1750–1920.(Social History of Africa.)

The American Historical Review ◽

10.1086/ahr.110.3.912 ◽

2005 ◽

Vol 110 (3) ◽

pp. 912-913

Author(s):

Clifton Crais

Keyword(s):

Social History ◽

Central Africa ◽

Ethnic Identities ◽

South Central ◽

History Of

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