Architecture of the Chugach accretionary complex as revealed by detrital zircon ages and lithologic variations: Evidence for Mesozoic subduction erosion in south-central Alaska

2013 ◽  
Vol 125 (11-12) ◽  
pp. 1891-1911 ◽  
Author(s):  
J. M. Amato ◽  
T. L. Pavlis ◽  
P. D. Clift ◽  
E. J. Kochelek ◽  
J. P. Hecker ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
Accretionary Complex ◽  
South Central ◽  
Subduction Erosion ◽  
Detrital Zircon Ages

scholarly journals The tectonic significance of the Early Cretaceous forearc-metamorphic assemblage in south-central Alaska based on detrital zircon U–Pb dating of sedimentary protoliths

2015 ◽  
Vol 52 (12) ◽  
pp. 1182-1190 ◽  
Author(s):  
Amanda Labrado ◽  
Terry L. Pavlis ◽  
Jeffrey M. Amato ◽  
Erik M. Day
Keyword(s):  
Early Cretaceous ◽  
Detrital Zircon ◽  
Early Jurassic ◽  
Ductile Deformation ◽  
Metamorphic Rocks ◽  
Accretionary Complex ◽  
Metamorphic Complex ◽  
Metasedimentary Rocks ◽  
South Central ◽  
Detrital Zircon Ages

A complex array of faulted arc rocks and variably metamorphosed forearc accretionary complex rocks form a mappable arc–forearc boundary in southern Alaska known as the Border Ranges fault (BRF). We use detrital U–Pb zircon dating of metasedimentary rocks within the Knik River terrane in the western Chugach Mountains to show that a belt of Early Cretaceous amphibolite-facies metamorphic rocks along the BRF was formed when older mélange rocks of the Chugach accretionary complex were reworked in a sinistral-oblique thrust reactivation of the BRF during a period of forearc plutonism. The metamorphic subterrane of the Knik River terrane has a maximum depositional age (MDA) of 156.5 ± 1.5 Ma and a detrital zircon age spectrum that is indistinguishable from the Potter Creek assemblage of the Chugach accretionary complex, supporting correlation of these units. These ages contrast strongly with new and existing data that show Triassic to earliest Jurassic detrital zircon ages from metamorphic screens in the plutonic subterrane of the Knik River terrane, a fragmented Early Jurassic plutonic assemblage generally interpreted as the basement of the Peninsular terrane. Based on these findings, we propose the following new terminology for the Knik River terrane: (1) “Carpenter Creek metamorphic complex” for the Early Cretaceous “metamorphic subterrane”, (2) “western Chugach trondhjemite suite” for the Early Cretaceous forearc plutons within the belt, (3) “Friday Creek assemblage” for a transitional mélange unit that contains blocks of the Carpenter Creek complex in a chert–argillite matrix, and (4) “Knik River metamorphic complex” in reference to metamorphic rocks engulfed by Early Jurassic plutons of the Peninsular terrane that represent the roots of the Talkeetna arc. The correlation of the Carpenter Creek metamorphic complex with the Chugach mélange indicates that the trace of the BRF lies ∼1–5 km north of the map trace shown on geologic maps, although, like other segments of the BRF, this boundary is blurred by local complexities within the BRF system. Ductile deformation of the mélange is sufficiently intense that few vestiges of its original mélange fabric exist, suggesting the scarcity of rocks described as mélange in the cores of many orogens may result from misidentification of rocks that have been intensely overprinted by younger, ductile deformation.

scholarly journals Supplemental Material: Detrital zircon geochronology and Hf isotope geochemistry of Mesozoic sedimentary basins in south-central Alaska: Insights into regional sediment transport, basin development, and tectonics along the NW Cordilleran margin

2020 ◽  
Author(s):  
C.R. Fasulo ◽  
et al.
Keyword(s):  
Detrital Zircon ◽  
Isotope Geochemistry ◽  
Age Distribution ◽  
Sedimentary Basins ◽  
Alaska Range ◽  
Zircon Age ◽  
Detrital Zircon Geochronology ◽  
South Central ◽  
Cordilleran Margin ◽  
Detrital Zircon Ages

Supplemental Figure S1. Normalized distribution plot of detrital zircon ages from the Kahiltna assemblage of the central Alaska Range (Hampton et al., 2010), the Wellesly basin (this study), and the Kahiltna assemblage of the northwestern Talkeetna Mountains (Hampton et al., 2010). Note that the detrital zircon age distribution of ages older than 500 Ma has 10× vertical exaggeration.

scholarly journals Detrital zircon geochronology and Hf isotope geochemistry of Mesozoic sedimentary basins in south-central Alaska: Insights into regional sediment transport, basin development, and tectonics along the NW Cordilleran margin

Geosphere ◽  
2020 ◽  
Vol 16 (5) ◽  
pp. 1125-1152 ◽  
Author(s):  
Cooper R. Fasulo ◽  
Kenneth D. Ridgway ◽  
Jeffrey M. Trop
Keyword(s):  
Detrital Zircon ◽  
Lower Cretaceous ◽  
Sedimentary Basins ◽  
Upper Jurassic ◽  
Detrital Zircons ◽  
Hf Isotope ◽  
Published Data ◽  
Convergent Margin ◽  
South Central ◽  
Detrital Zircon Ages

Abstract The Jurassic–Cretaceous Nutzotin, Wrangell Mountains, and Wellesly basins provide an archive of subduction and collisional processes along the southern Alaska convergent margin. This study presents U-Pb ages from each of the three basins, and Hf isotope compositions of detrital zircons from the Nutzotin and Wellesly basins. U-Pb detrital zircon ages from the Upper Jurassic–Lower Cretaceous Nutzotin Mountains sequence in the Nutzotin basin have unimodal populations between 155 and 133 Ma and primarily juvenile Hf isotope compositions. Detrital zircon ages from the Wrangell Mountains basin document unimodal peak ages between 159 and 152 Ma in Upper Jurassic–Lower Cretaceous strata and multimodal peak ages between 196 and 76 Ma for Upper Cretaceous strata. Detrital zircon ages from the Wellesly basin display multimodal peak ages between 216 and 124 Ma and juvenile to evolved Hf compositions. Detrital zircon data from the Wellesly basin are inconsistent with a previous interpretation that suggested the Wellesly and Nutzotin basins are proximal-to-distal equivalents. Our results suggest that Wellesly basin strata are more akin to the Kahiltna basin, which requires that these basins may have been offset ∼380 km along the Denali fault. Our findings from the Wrangell Mountains and Nutzotin basins are consistent with previous stratigraphic interpretations that suggest the two basins formed as a connected retroarc basin system. Integration of our data with previously published data documents a strong provenance and temporal link between depocenters along the southern Alaska convergent margin. Results of our study also have implications for the ongoing discussion concerning the polarity of subduction along the Mesozoic margin of western North America.

scholarly journals Supplemental Material: Detrital zircon geochronology and Hf isotope geochemistry of Mesozoic sedimentary basins in south-central Alaska: Insights into regional sediment transport, basin development, and tectonics along the NW Cordilleran margin

2020 ◽  
Author(s):  
C.R. Fasulo ◽  
et al.
Keyword(s):  
Detrital Zircon ◽  
Isotope Geochemistry ◽  
Age Distribution ◽  
Sedimentary Basins ◽  
Alaska Range ◽  
Zircon Age ◽  
Detrital Zircon Geochronology ◽  
South Central ◽  
Cordilleran Margin ◽  
Detrital Zircon Ages

Supplemental Figure S1. Normalized distribution plot of detrital zircon ages from the Kahiltna assemblage of the central Alaska Range (Hampton et al., 2010), the Wellesly basin (this study), and the Kahiltna assemblage of the northwestern Talkeetna Mountains (Hampton et al., 2010). Note that the detrital zircon age distribution of ages older than 500 Ma has 10× vertical exaggeration.

DETRITAL ZIRCON AGES REVEAL POST 15 MA CONVERGENCE AND PLEISTOCENE-QUATERNARY BASEMENT UNROOFING IN THE CAUCASUS

2017 ◽  
Author(s):  
Alexander Tye ◽  
◽  
Nathan A. Niemi ◽  
Rafiq Safarov ◽  
Fakhraddin Kadirov
Keyword(s):  
Detrital Zircon ◽  
The Caucasus ◽  
Detrital Zircon Ages
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