Lower and Middle Jurassic Radiolaria (Multicyrtid Nassellariina) from California, East-Central Oregon and the Queen Charlotte Islands, B.C.

1982 ◽  
Vol 28 (2) ◽  
pp. 111 ◽  
Author(s):  
Emile A. Pessagno ◽  
Patricia A. Whalen
Keyword(s):  
Middle Jurassic ◽  
East Central ◽  
Queen Charlotte Islands

Reineckeiidae (Ammonoidea) from the Callovian (Middle Jurassic) of the Shotori Range (East Central Iran)

2002 ◽  
Vol 2002 (3) ◽  
pp. 184-192 ◽  
Author(s):  
Kazem Seyed-Emami ◽  
Gerhard Schairer ◽  
Franz T. Fürsich ◽  
Markus Wilmsen ◽  
Mahmoud Reza Majidifard
Keyword(s):  
Middle Jurassic ◽  
Central Iran ◽  
East Central

Correlation among lower to upper crustal components in an island arc: the Jurassic Bonanza arc, Vancouver Island, Canada

1999 ◽  
Vol 36 (8) ◽  
pp. 1371-1413 ◽  
Author(s):  
Susan M DeBari ◽  
Robert G Anderson ◽  
James K Mortensen
Keyword(s):  
Middle Jurassic ◽  
Volcanic Rocks ◽  
Vancouver Island ◽  
Island Arc ◽  
Calc Alkaline ◽  
Queen Charlotte Islands ◽  
Basement Rocks ◽  
Plutonic Rocks ◽  
Differential Uplift ◽  
Age Range

The Westcoast Crystalline Complex (WCC), Island Intrusions, and Bonanza Group of Vancouver Island, Canada, form three different crustal levels of the Early to Middle Jurassic Bonanza island arc. Differential uplift has exposed the plutonic roots and the volcanic carapace of the arc for a strike length of ~500 km, and for another 250 km on the Queen Charlotte Islands. At deeper crustal levels within the arc, influx of mantle-derived magmas was accompanied by metamorphism and melting of Wrangellian basement rocks, yielding the heterogeneous WCC. Upward mobilization and hybridization of magmas to shallower levels in the crust resulted in the batholiths of the Island Intrusions and the lavas and pyroclastic rocks of the Bonanza Group. New U-Pb crystallization ages for plutonic rocks of the arc span an age range of 190.3 ± 1.0 to 168.6 ± 5.3 Ma. Ages of the WCC and western Island Intrusions are indistinguishable and overlap with published fossil and isotopic ages for the Bonanza Group. Younger Middle Jurassic ages for the eastern Island Intrusions overlap with those for plutonic rocks in the southern Coast Belt and Queen Charlotte Islands. All plutonic and volcanic rocks within the arc have overlapping geochemical signatures, supporting their comagmatic origin. All are light rare earth element-enriched with abundances 10-50× chondrites. The most mafic noncumulate gabbroic rocks have compositions typical of island arc basalts, with intermediate values of Al2O3 (16-17 wt.%) and high MgO (7-9 wt.%). More differentiated rocks follow a calc-alkaline trend with concomitant increase in Al2O3 (18-20 wt.%). Their geochemistry indicates varying degrees of mixing with melts of mafic Wrangellian basement.

Lower and Middle Jurassic Perispyridium (Radiolaria) from the Snowshoe Formation, East-Central Oregon

1988 ◽  
Vol 34 (4) ◽  
pp. 289 ◽  
Author(s):  
Norman MacLeod
Keyword(s):  
Middle Jurassic ◽  
East Central

DEPOSITION DOWNWIND OF THE COLORADO PLATEAU ERGS: UPPERMOST TRIASSIC?-MIDDLE JURASSIC STRATA OF THE PLOMOSAS UPLIFT, EAST-CENTRAL CHIHUAHUA, MEXICO

2016 ◽  
Author(s):  
Timothy F. Lawton ◽  
◽  
Jorge Enrique Ruiz-Urueña ◽  
Carmen Manuela Tarango-Terrazas ◽  
Edgar Juárez-Arriaga ◽  
...  
Keyword(s):  
Middle Jurassic ◽  
Colorado Plateau ◽  
East Central

Deformation of the western margin of the Omineca Belt near Crooked Lake, east-central British Columbia

1990 ◽  
Vol 27 (3) ◽  
pp. 414-425
Author(s):  
Jeffrey A. Fillipone ◽  
John V. Ross
Keyword(s):  
British Columbia ◽  
North America ◽  
Middle Jurassic ◽  
Phase 1 ◽  
Late Devonian ◽  
East Central ◽  
Western Margin ◽  
Metasedimentary Rocks ◽  
Narrow Zone ◽  
Minimum Age

The western margin of the Omineca Belt near Crooked Lake, British Columbia, consists of metasedimentary rocks (Snowshoe Group) and orthogneisses of the Barkerville terrane, structurally overlain by a mafic volcanic – sedimentary package of rocks belonging to the allochthonous Slide Mountain (Crooked Amphibolite) and Quesnel terranes (Triassic phyllite and Nicola Group). At least two episodes of regional deformational (phases 2 and 3) affected this composite package. Deformation and metamorphism (phase 1) in the Snowshow Group predate the formation of this package and are nowhere evident within the allochthonous terranes.Middle Jurassic metamorphism ranging from chlorite zone through sillimanite zone affected all units. Isograds are folded, together with the junction between the terranes, indicating that the metamorphic assemblages developed prior to folding of this boundary. Granitic orthogneiss (Boss Mountain, Quesnel Lake, and Perseus gneisses), having a minimum age of Late Devonian to Early Pennsylvanian, was intruded into and deformed with the Snowshoe Group during the earliest recognizable phase of deformation in the Barkerville terrane (phase 1). Slide Mountain terrane rocks occupy a narrow zone where large eastward displacement occurred during overthrusting of the Intermontane superterrane upon the western margin of North America in Middle Jurassic time.

Paleomagnetic results from Upper Triassic and Middle Jurassic strata of east-central New Mexico, and implication for North American apparent polar wander path

2021 ◽  
pp. 228872
Author(s):  
Masoud Mirzaei ◽  
Bernard A. Housen ◽  
Russell F. Burmester ◽  
Brady Z. Foreman
Keyword(s):  
New Mexico ◽  
North American ◽  
Middle Jurassic ◽  
Upper Triassic ◽  
East Central ◽  
Polar Wander ◽  
Apparent Polar Wander Path
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