Upper Cretaceous Stratigraphy and Tectonic History of Ridgway Area, Northern San Juan Mountains, Colorado: ABSTRACT

AAPG Bulletin ◽  
1981 ◽  
Vol 65 ◽  
Author(s):  
Paul C. Weimer
Keyword(s):  
Upper Cretaceous ◽  
San Juan ◽  
San Juan Mountains ◽  
Tectonic History ◽  
History Of

Obducted nappe sequence in the San Juan Islands – northwest Cascades thrust system, Washington and British Columbia

2012 ◽  
Vol 49 (7) ◽  
pp. 796-817 ◽  
Author(s):  
E.H. Brown
Keyword(s):  
British Columbia ◽  
Detrital Zircons ◽  
San Juan ◽  
San Juan Islands ◽  
Tectonic History ◽  
Plutonic Complex ◽  
Coast Plutonic Complex ◽  
History Of ◽  
Accreted Terranes ◽  
Thrust System

The San Juan Islands – northwest Cascades thrust system in Washington and British Columbia is composed of previously accreted terranes now assembled as four broadly defined composite nappes stacked on a continental footwall of Wrangellia and the Coast Plutonic Complex. Emplacement ages of the nappe sequence are interpreted from zircon ages, field relations, and lithlogies, to young upward. The basal nappe was emplaced prior to early Turonian time (∼93 Ma), indicated by the occurrence of age-distinctive zircons from this nappe in the Sidney Island Formation of the Nanaimo Group. The emplacement age of the highest nappe in the thrust system postdates 87 Ma detrital zircons within the nappe. The nappes bear high-pressure – low-temperature (HP–LT) mineral assemblages indicative of deep burial in a thrust wedge; however, several features indicate that metamorphism occurred prior to nappe assembly: metamorphic discontinuities at nappe boundaries, absence of HP–LT assemblages in the footwall to the nappe pile, and absence of significant unroofing detritus in the Nanaimo Group. A synorogenic relationship of the thrust system to the Nanaimo Group is evident from mutually overlapping ages and by conglomerates of Nanaimo affinity that lie within the nappe pile. From the foregoing relations, and broader Cordilleran geology, the tectonic history of the nappe terranes is interpreted to involve initial accretion and subduction-zone metamorphism south of the present locality, uplift and exhumation, orogen-parallel northward transport of the nappes as part of a forearc sliver, and finally obduction at the present site over the truncated south end of Wrangellia and the Coast Plutonic Complex.

GEOCHEMICAL CHARACTERISTICS OF AUSTRALIA'S SOUTHERN MARGIN PETROLEUM SYSTEMS

1999 ◽  
Vol 39 (1) ◽  
pp. 297 ◽  
Author(s):  
D.S. Edwards ◽  
H.I.M. Struckmeyer ◽  
M.T. Bradshaw ◽  
J.E. Skinner
Keyword(s):  
Upper Cretaceous ◽  
Petroleum System ◽  
Geochemical Characteristics ◽  
Source Rocks ◽  
Liquid Hydrocarbons ◽  
Petroleum Systems ◽  
Tectonic History ◽  
Southern Margin ◽  
History Of ◽  
Oil Source

The hydrocarbons discovered to date on the southern margin of Australia have been assigned to the Austral Petroleum Supersystem based on the age of their source rocks and common tectonic history. Modelling of the source facies distribution within this supersystem using tectonic, climatic and geographic history of the southern margin basins, suggests the presence of a variety of source rocks deposited in saline playa lakes, fluvial, lacustrine, deltaic and anoxic marine environments.Testing of the palaeogeographic model using geochemical characteristics of liquid hydrocarbons confirms the three-fold subdivision (Al, A2 and A3) of the Austral Petroleum Supersystem.Bass Basin oils are assigned to the Austral 3, Eastern View Petroleum System. The presence of oleanane in the biomarker assemblages of these oils, together with their negatively sloping, heavy, isotopic profiles, indicate derivation from Upper Cretaceous-Tertiary fluvio–deltaic source facies.In the eastern Otway Basin, oils of the Austral 2, Eumeralla Petroleum System are sourced by Lower Cretaceous (Aptian–Albian) coaly facies. Oil shows reservoired in the Wigunda Formation at Greenly-1 in the Duntroon Basin are possibly sourced from the Borda Formation and are assigned to the Austral 2, Borda Petroleum System.In the western Otway, Duntroon and Bight basins, a lack of definitive oil-source rock correlations precludes the identification of individual Austral 1 petroleum systems.

New Constraints on the Timing and History of Breccia Dikes in the Western San Juan Mountains, Southwestern Colorado

2019 ◽  
Vol 56 (4) ◽  
pp. 397-420
Author(s):  
David Gonzales
Keyword(s):  
Spatial Relationship ◽  
Metamorphic Rocks ◽  
San Juan ◽  
San Juan Mountains ◽  
Basement Rocks ◽  
Intrusive Rocks ◽  
Close Spatial Relationship ◽  
History Of ◽  
Proterozoic Basement ◽  
Structural Levels

In the western San Juan Mountains, clastic (breccia) dikes crop out in Paleozoic to Cenozoic rocks. The dikes are tabular to bifurcating masses up to several meters thick and are exposed on northwest or northeast trends for up to several kilometers. They are matrix- to clast-supported with angular to rounded pebble- to boulder-sized fragments that in most dikes are dominated by Proterozoic igneous and metamorphic rocks. U-Pb age analyses (n = 3) reveal a range of zircon ages in all samples with several containing high proportions of 1820 to 1390 Ma zircons. The majority of Proterozoic zircons are interpreted as direct contributions from basement rocks during breccia dike formation and emplacement. Field relations and U-Pb zircon analyses reveal that breccia dikes formed in intervals from 65 to 30 Ma (Ouray) and 27 to 12 Ma (Stony Mountain); some dikes are closely allied with mineralization. The dikes formed at depths over 500 meters where Proterozoic basement was fragmented, entrained, and transported to higher structural levels along with pieces of Paleozoic to Cenozoic rocks. A close spatial relationship exists between breccia dikes and latest Mesozoic to Cenozoic plutons. This is best exemplified near Ouray where clastic dikes share similar trends with ~65 Ma granodiorite dikes, and there is a clear transition from intrusive rocks to altered-brecciated plutons, and finally to breccia dikes. The preponderance of evidence supports breccia dike formation via degassing and explosive release of CO2-charged volatiles on deep fractures related to emplacement of 70 to 4 Ma plutons or mantle melts. In addition to breccia dikes, several post-80 Ma events in the region involved explosive release of volatile-charged magmas: 29-27 Ma calderas, ~25 Ma diatremes, and ~24 Ma breccia pipes. Causal factors for production of these gas-charged magmas remain poorly understood, but partial melting or assimilation of altered and metasomatized lithospheric mantle could have played a role.

Phases terminales et tectogenese de la montagne Sainte-Victoire

1965 ◽  
Vol S7-VII (1) ◽  
pp. 59-63
Author(s):  
Fernand Touraine
Keyword(s):  
Upper Cretaceous ◽  
Basic Structure ◽  
The West ◽  
Lower Eocene ◽  
Tectonic History ◽  
History Of

Abstract Sainte-Victoire mountain has been considered as the eroded remnant of a massif whose first signs are known from the upper Cretaceous but which was actually emplaced during the lower Eocene. Three studies of the area have shown that the basic structure, but not the relief, was formed in the Eocene; intense erosion in the Oligocene and Miocene peneplaned the area. In a post-Tortonian phase the structure was uplifted and acquired its present morphology. The uplift is limited on the west by a fault at the foot of the Bau-Roux plateau; the eastern limit is the Delubre fault. The tectonic history of the area developed in seven phases and interphases from the upper Cretaceous to the post-Tortonian.

Tectonic history of the Dent Blanche

2017 ◽  
Vol 9 (2.1) ◽  
pp. 1-73 ◽  
Author(s):  
Paola Manzotti ◽  
Michel Ballèvrei
Keyword(s):  
Tectonic History ◽  
History Of
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