Structure of the Swauk formation and Teanaway dike swarm, Washington Cascades

Doran, Brigid

doi:10.31979/etd.5rwr-cdbk

Cited by 5 publications

(16 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Folds in the Swauk Formation mostly have wavelengths of 100 m to 2 km and steep axial planes (Fig. 6C) (Tabor et al, 1982(Tabor et al, , 2000Doran, 2009). Axial traces of these folds change from northwest in the west, to mainly east-southeast or west-northwest in the central region, to largely northwest in the easternmost part of the Swauk Formation (Tabor et al, 1982; our mapping; Fig.…”

Section: Eocene Nonmarine Basins and Their Deformationmentioning

confidence: 63%

“…These data include material in theses by some of the authors (Michels, 2008;Shea, 2008;Doran, 2009;McLean, 2012), publications arising from group research (Miller and Bowring, 1990;Gordon et al, 2010aGordon et al, , 2010bWintzer, 2012), and other publications, notably Misch (1968), Haugerud et al (1991), Paterson et al (2004), and Eddy et al (2016). The main new data sets presented herein include high-precision U-Pb (chemical abrasion-isotope dilution-thermal ionization mass spectrometry, CA-ID-TIMS) zircon dating of 10 orthogneiss bodies in the Skagit Gneiss Complex ( Fig.…”

Section: Overview Of North Cascades Geologymentioning

confidence: 99%

“…49.3 Ma (U-Pb date for Teanaway lavas) mafic Teanaway dike swarm, which primarily intrudes the Swauk Formation ( Fig. 8; Foster, 1958;Tabor et al, 1984;Doran, 2009). This swarm extends ~75 km from east to west and a maximum of 18 km from north to south (Fig.…”

Section: Eocene Dikesmentioning

confidence: 99%

See 2 more Smart Citations

Linking deep and shallow crustal processes during regional transtension in an exhumed continental arc, North Cascades, northwestern Cordillera (USA)

et al. 2016

View full text Add to dashboard Cite

Section: Eocene Nonmarine Basins and Their Deformationmentioning

confidence: 63%

Section: Overview Of North Cascades Geologymentioning

confidence: 99%

See 1 more Smart Citation

Linking deep and shallow crustal processes during regional transtension in an exhumed continental arc, North Cascades, northwestern Cordillera (USA)

et al. 2016

View full text Add to dashboard Cite

“…The eastern part of the Swauk Formation is openly to tightly folded, with fold wavelengths of 100 m to 2 km and steep axial planes (Tabor et al, 1982;Doran, 2009).…”

Section: ~390 Mmentioning

confidence: 99%

“…The Teanaway dikes are a swarm of basaltic dikes that intrude the Swauk Formation and are presumably the same age as the Teanaway lavas (Foster, 1958;Tabor et al, 1982;Doran, 2009;Eddy et al, 2016) (Fig. 4).…”

Section: Teanaway Formation and Dikesmentioning

confidence: 99%

Deformation, Sandstone Detrital Zircon Ages, and Provenance in and near the Eocene Leavenworth Fault Zone, Washington

Senes

View full text Add to dashboard Cite

The North Cascades is an excellent area to study basins and strike-slip faults that formed during regional transtension. This structural, petrographic, and U-Pb geochronological study focuses on the Eocene Leavenworth fault (LVF), which separates Eocene non-marine clastic rocks of the Chumstick Formation and older Swauk Formation. The LVF has been interpreted as a dextral strike-slip fault active during Chumstick deposition and as a reverse fault. Poles to beds (n=207) in the Swauk Formation trend WNW, oblique to the ~320˚-striking LVF, and commonly dip SSW, defining a girdle and a fold axis plunging 4˚ toward 297˚. Beds (n=50) in the Chumstick Formation trend NW and generally dip NE, and poles to beds define a fold axis plunging 13˚ towards 306˚. Overall, 70% of folds in the formations trend NW to WNW, <30˚ counterclockwise to the main strand of the LVF, compatible with dextral transpression. Most faults in the Swauk and Chumstick formations strike >45˚ or <30˚ to the main strand of the LVF. Their movement sense is unknown. Source terranes for the Swauk Formation likely include the Cascades crystalline core to the N and NE and a combination of other relatively local sources to the N, NE, and SW. Detrital zircon maximum depositional ages in the Swauk Formation range from 67.2 ± 1.9 to 50.46 ± 0.17 Ma, constraining the timing of deposition and early folding of the Swauk Formation. Distinctive ~91 Ma tonalitic clasts in Chumstick conglomerate were likely transported ~20 km from their source by dextral slip of the Leavenworth fault zone. v ACKNOWLEDGMENTS I would like to take this opportunity to thank the people that made this thesis possible. First and foremost I want to thank my family, who have always encouraged and supported me. Especially my parents, who have devoted their lives to giving me the best possible future, and for this, I would like to dedicate this thesis to them. To Robert Duffala, your motivation and constant optimism has helped me greatly through this process. Thank you for being my support during times when everything seemed impossible. I would like to extend special gratitude and admiration to my thesis advisor, Bob Miller, for giving me the opportunity to work in the North Cascades, for his incredible mentorship and guidance through my graduate studies, and for his insight in the field and in the office. I value greatly all the time and effort you put into making this thesis possible. I thank my thesis committee members, Dave Andersen and Jonathan Miller, your doors were always open and I appreciate your insightful revisions and knowledge. I especially give thanks to my field assistant Natasha Budimirovic for her encouragement and companionship which kept me sane through my field work. I would like to express gratitude to my fellow geology graduate students and friends, especially Kelly Dustin and Katie Bryant. I knew I could go to you with any questions and you were always reliable. Thank you for listening to me practice my thesis defense and giving me creative feedback. Most importantly, I a...

show abstract

Eocene dike orientations across the Washington Cascades in response to a major strike-slip faulting episode and ridge-trench interaction

et al. 2022

View full text Add to dashboard Cite

The northern Cascade Mountains in Washington (USA) preserve an exceptional shallow to mid-crustal record of Eocene transtension marked by dextral strike-slip faulting, intrusion of dike swarms and plutons, rapid non-marine sedimentation, and ductile flow and rapid cooling in parts of the North Cascades crystalline core. Transtension occurred during ridge-trench interaction with the formation of a slab window, and slab rollback and break-off occurred shortly after collision of the Siletzia oceanic plateau at ca. 50 Ma. Dike swarms intruded a ≥1250 km2 region between ca. 49.3 Ma and 44.9 Ma, and orientations of more than 1500 measured dikes coupled with geochronologic data provide important snapshots of the regional strain field. The mafic Teanaway dikes are the southernmost and most voluminous of the swarms. They strike NE (mean = 036°) and average ~15 m in thickness. To the north, rhyolitic to basaltic dikes overlap spatially with 49.3–46.5 Ma, mainly granodioritic plutons, but they typically predate the nearby plutons by ca. 500 k.y. The average orientations of five of the six dike domains range from 010° to 058°; W-NW– to NW–striking dikes characterize one domain and are found in lesser amounts in a few other domains. Overall, the mean strike for all Eocene dikes is 035°, and the average extension direction (305°–125°) is oblique to the strike (~320°) of the North Cascades orogen. Extension by diking reached ~45% in one >7-km-long transect through the Teanaway swarm and ranged from ~5% to locally ~79% in shorter transects across other swarms, which corresponds to a minimum of ~12 km of extension. The dominant NE-striking dikes are compatible with the dextral motion on the N- to NW-striking (~355–320°) regional strike-slip faults. Some of the W–NW- to NW-striking dikes were arguably influenced by pre-existing faults, shear fractures, and foliations, and potentially in one swarm where both NE- and lesser W-NW–striking dikes are present, by a switch in principal stress axes induced by dike emplacement. Alternatively, the W-NW– to NW-striking dikes may reflect a younger regional strain field, as ca. 49.3–47.5 Ma U-Pb zircon ages of the NE-striking dikes are older than those of the few dated W-NW– to NW-trending dikes. In one scenario, NE-striking dikes intruded during an interval when strain mainly reflected dextral strike-slip faulting, and the younger dikes record a switch to more arc-normal extension. Diking ended as magmatism migrated into a N-S–trending belt west of the North Cascade core that marks the initiation of the ancestral Cascade arc.

show abstract

Structure of the Swauk formation and Teanaway dike swarm, Washington Cascades

Cited by 5 publications

References 0 publications

Linking deep and shallow crustal processes during regional transtension in an exhumed continental arc, North Cascades, northwestern Cordillera (USA)

Linking deep and shallow crustal processes during regional transtension in an exhumed continental arc, North Cascades, northwestern Cordillera (USA)

Deformation, Sandstone Detrital Zircon Ages, and Provenance in and near the Eocene Leavenworth Fault Zone, Washington

Eocene dike orientations across the Washington Cascades in response to a major strike-slip faulting episode and ridge-trench interaction

Contact Info

Product

Resources

About