Miocene Tholeiitic Basalts of Coastal Oregon and Washington and Their Relations to Coeval Basalts of the Columbia Plateau

Snavely, Parke Detweiler; MacLeod, N.S.; Wagner, Holly Clyde

doi:10.1130/0016-7606(1973)84<387:mtboco>2.0.co;2

Cited by 47 publications

(13 citation statements)

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“…1). These sheet fl ows and intracanyon fl ows crossed the Coast Range through several structural lows and are now exposed along the coast from Seal Rock, south of Newport, Oregon, to Grays Harbor, Washington, a distance of 275 km (Snavely et al, 1973). This part of the fi eld trip examines the transition from subaerial to invasive fl ows in the northern part of the Astoria Basin, near the mouth of the Columbia River.…”

Section: Day 2: Crbg Transition To Invasive Flows Lower Columbia Rivmentioning

confidence: 99%

“…Where CRBG fl ows entered the coastal basins, they produced fl uvial and submarine pillow delta complexes and ultimately invaded the marine sedimentary section as mega-invasive fl ows, producing peperites, (rootless) vent complexes, and massive sills and dikes (Snavely et al, 1973;Niem and Niem, 1985;Wells, 1989). Originally, the Miocene basalt intrusive complexes along the coast were thought to be CRBG magmas derived from source vents on the coast (Snavely et al, 1973). The Miocene coastal intrusions of CRBG chemistry had many of the characteristics of central vent complexes, with radial and ring dikes, central plugs, and intrusions into rocks as old as Eocene.…”

Section: Day 2: Crbg Transition To Invasive Flows Lower Columbia Rivmentioning

confidence: 99%

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The Columbia River Basalt Group—From the gorge to the sea

Wells¹,

Niem²,

Evarts³

et al. 2009

Volcanoes to Vineyards

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Miocene fl ood basalts of the Columbia River Basalt Group inundated eastern Washington, Oregon, and adjacent Idaho between 17 and 6 Ma. Some of the more voluminous fl ows followed the ancestral Columbia River across the Cascade arc, Puget-Willamette trough, and the Coast Range to the Pacifi c Ocean. We have used fi eld mapping, chemistry, and paleomagnetic directions to trace individual fl ows and fl ow packages from the Columbia River Gorge westward into the Astoria Basin, where they form pillow palagonite complexes and mega-invasive bodies into older marine sedimentary rocks. Flows of the Grande Ronde, Wanapum, and Saddle Mountains Basalts all made it to the ocean; at least 33 fl ows are recognized in the western Columbia River Gorge, 50 in the Willamette Valley, 16 in the lower Columbia River Valley, and at least 12 on the Oregon side of the Astoria Basin. In the Astoria Basin, the basalt fl ows loaded and invaded the wet marine sediments, producing peperite breccias, soft sediment deformation, and complex invasive relations. Mega-invasive sills up to 500 m thick were emplaced into strata as old as Eocene, and invasive dikes up to 90 m thick can be traced continuously for 25 km near the basin margin. Mega-pillow complexes up to a kilometer thick are interpreted as the remains of lava deltas that prograded onto the shelf and a fi lled submarine canyon southeast of Astoria, possibly providing the hydraulic head for injection of invasive sills and dikes at depth.

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Section: Day 2: Crbg Transition To Invasive Flows Lower Columbia Rivmentioning

confidence: 99%

Section: Day 2: Crbg Transition To Invasive Flows Lower Columbia Rivmentioning

confidence: 99%

The Columbia River Basalt Group—From the gorge to the sea

Wells¹,

Niem²,

Evarts³

et al. 2009

Volcanoes to Vineyards

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“…Except for the sills near the coast, both units are underlain by the plateau-derived Grande Ronde and Wanapum basalts [Snavely et al, 1973;Schmincke, 1967;Wells, 1981], which can be firmly correlated from the coast to the Columbia Plateau. Similarly, the Pomona and the basalt of Pack Sack Lookout are both interbedded with late Miocene sedimentary rocks [Schmincke, 1967;Snavely et al, 1973]. In the Cathlamet region, Wells [1981] has mapped in detail a sequence of at None of the samples was found to be directionally unstable.…”

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confidence: 99%

Post 12 m.y. rotation of southwest Washington

Magill¹,

Wells²,

Simpson³

et al. 1982

J. Geophys. Res.

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Paleomagnetic field directions from the basalt of Pack Sack Lookout are compared to those from the Pomona Member of the Saddle Mountains Basalt of the Columbia River Basalt Group. The Pomona crops out over a wide region on the Columbia Plateau east of the Cascade Range, and the basalt of Pack Sack Lookout crops out well to the west of the Cascades about 30 to 60 km east of the Washington coast. Our paleomagnetic results support existing geologic and geochemical evidence that both these units are part of a single 12‐m.y.‐old flow that erupted in western Idaho and flowed to the Washington coast. The magnetic data further indicate that southwest Washington has undergone clockwise rotation with respect to the Columbia Plateau and stable North America. The data suggest that both a large‐scale regional rotation of ∼16° and locally complex small‐scale rotations exist, the two being present to different degrees in the eastern and western regions of southwest Washington. The Cascade Range appears to coincide with the tectonic boundary, separating rotated and unrotated regions of Washington state. Rotation of southwest Washington appears to have been associated with the rotation of large pieces of western Oregon and southern Washington, possibly as a result of either a ridge‐push force from the Basin and Range province or shear along the Pacific‐North America plate boundary.

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“…The collection program was based on locations described by Snavely et al (1973), Griggs (1976), McDougall (1976, Swanson et al (1979), andReidel (1983). Our collection and crushing procedures are described in Chamberlain and Lambert (1994).…”

Section: Sampling and Analytical Methodsmentioning

confidence: 99%

Ferro-andesites in the Grande Ronde Basalt: their composition and significance in studies of the origin of the Columbia River Basalt Group

Lambert¹,

Chamberlain²,

Holland³

1995

Can. J. Earth Sci.

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Flows from the Grande Ronde Basalt of the Columbia River Basalt Group include several with the chemical composition of ferro-andesites. These flows have SiO, > 55%, MgO < 4 % , and also have higher FeIMg than the average value for Grande Ronde Basalt. They are also distinctly richer in Cs, Rb, K, Ba, La, Ce, Th, and U than the remainder of the Grande Ronde Basalt flows, and possess small negative Eu anomalies. Their Pb isotopic compositions define a mixing line with a negative slope on a 206Pb/204Pb versus 207Pb/204Pb plot. Their Nd isotopic compositions lie between 143Nd/'44Nd = 0.51252 and 0.51264, and their Sr isotopic compositions lie between 87Sr/86Sr = 0.7055 and 0.7060. These values define the enriched end of the Columbia River Basalt Group spectrum on a Sr-Nd epsilon diagram (excluding the Saddle Mountains Basalt). These ferro-andesite flows also form a compositional end member of the Columbia River Basalt Group and are sufficiently distinctive to warrant special consideration. We compare them with lavas from other tholeiitic provinces. Petrogenetically, they can be related to the Grande Ronde Basalt low-Mg basalts by plagioclase fractionation, or by clinopyroxene fractionation in partially melted eclogites. However, the situation may not be that simple, as their unique isotopic compositions are closely related to those of parental mantle materials, perhaps thus requiring separate reservoirs and (or) sources. Extending this argument to other parts of the Columbia River Basalt Group suggests that the origin of these basalts may be in a system of comparatively small magma chambers in the uppermost mantle, frequently replenished from a variety of sources.RburnC : Plusieurs coulkes du Basalte de la Grande Ronde, qui est affilit au Groupe de Basalte de la Columbia River, ont la composition chimique des ferro-andksites. Ces coulkes ont des teneurs de Si02 > 55 %, MgO < 4 % , et des rapports Fe/Mg plus klevks que le rapport moyen fourni par le Basalte de la Grande Ronde. En outre, elles sont nettement plus riches en Cs, Rb, K, Ba, La, Ce, Th et U que tout le reste des coul6es de Basalte de la Grande Ronde, et elles affichent de faibles anomalies nkgatives en Eu. Leurs compositions isotopiques du Pb dtfinissent une droite de mklange avec une pente nkgative sur le diagramme 206Pb/2"Pb versus 207~b/204Pb. Leurs compositions isotopiques du Nd sont comprises entre 143Nd/'44Nd = 0,51252 et 0,51264, et leurs compositions isotopiques du Sr varient de 87Sr/86Sr = 0,7055 B 0,7060. Ces donnkes dkterminent le p61e enrichi de la courbe du Groupe de Basalte de la Columbia River dans le diagramrne epsilon Sr-Nd (excluant le Basalte de Saddle Mountains). Ces coulkes de ferro-andksite dtfinissent aussi un pBle chimique du Groupe de Basalte de la Columbia River, et elles sont suffisamment distinctes pour Ctre prises en considkration. Nous les comparons avec les laves de d'autres provinces tholtiitiques. Pktrogknktiquement, elles peuvent &tre relikes aux coulkes appauvries en Mg du Basalte de la Grande Ronde, soit par le fractionn...

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Miocene Tholeiitic Basalts of Coastal Oregon and Washington and Their Relations to Coeval Basalts of the Columbia Plateau

Cited by 47 publications

References 0 publications

The Columbia River Basalt Group—From the gorge to the sea

The Columbia River Basalt Group—From the gorge to the sea

Post 12 m.y. rotation of southwest Washington

Ferro-andesites in the Grande Ronde Basalt: their composition and significance in studies of the origin of the Columbia River Basalt Group

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