Northward extension of carolina slate belt stratigraphy and structure, south-central virginia: Results from geologic mapping

2007 ◽  
Vol 307 (4) ◽  
pp. 749-771
Author(s):  
P. C. Hackley ◽  
J. D. Peper ◽  
W. C. Burton ◽  
J. W. Horton
Keyword(s):  
Geologic Mapping ◽  
South Central ◽  
Carolina Slate Belt

scholarly journals Cretaceous to Oligocene magmatic and tectonic evolution of the western Alaska Range: Insights from U-Pb and 40Ar/39Ar geochronology

Geosphere ◽  
2020 ◽  
Author(s):  
James V. Jones ◽  
Erin Todd ◽  
Stephen E. Box ◽  
Peter J. Haeussler ◽  
Christopher S. Holm-Denoma ◽  
...  
Keyword(s):  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Geologic Mapping ◽  
Localized Deformation ◽  
Alaska Range ◽  
South Central ◽  
Wrangellia Terrane ◽  
Terrane Accretion ◽  
Latest Eocene ◽  
Slab Window

New U-Pb and 40Ar/39Ar ages integrated with geologic mapping and observations across the western Alaska Range constrain the distribution and tectonic setting of Cretaceous to Oligocene magmatism along an evolving accretionary plate margin in south-central Alaska. These rocks were emplaced across basement domains that include Neoproterozoic to Jurassic carbonate and siliciclastic strata of the Farewell terrane, Triassic and Jurassic plutonic and volcanic rocks of the Peninsular terrane, and Jurassic and Cretaceous siliciclastic strata of the Kahiltna assemblage. Plutonic rocks of different ages also host economic mineralization including intrusion-related Au, porphyry Cu-Mo-Au, polymetallic veins and skarns, and peralkaline intrusion-related rare-earth elements. The oldest intrusive suites were emplaced ca. 104–80 Ma into the Peninsular terrane only prior to final accretion. Deformation of the northern Kahiltna succession and underlying Farewell terrane occurred at ca. 97 Ma, and more widespread deformation ca. 80 Ma involved south-ver­gent folding and thrusting of the Kahiltna assemblage that records collisional accretion of the Peninsular-Wrangellia terrane and juxtaposition of sediment wedges formed on the inboard and outboard terranes. More widespread mag­matism ca. 75–55 Ma occurred in two general pulses, each having distinct styles of localized deformation. Circa 75–65 Ma plutons were emplaced in a transpressional setting and stitch the accreted Peninsular and Wrangellia terranes to the Farewell terrane. Circa 65–55 Ma magmatism occurred across the entire range and extends for more than 200 km inboard from the inferred position of the continental margin. The Paleocene plutonic suite generally reflects shallower emplacement depths relative to older suites and is associ­ated with more abundant andesitic to rhyolitic volcanic rocks. Deformation ca. 58–56 Ma was concentrated along two high-strain zones, the most prominent of which is 1 km wide, strikes east-northeast, and accommodated dextral oblique motion. Emplacement of widespread intermediate to mafic dikes ca. 59–51 Ma occurred before a notable magmatic lull from ca. 51–44 Ma reflect­ing a late Paleocene to early Eocene slab window. Magmatism resumed ca. 44 Ma, recording the transition from slab window to renewed subduction that formed the Aleutian-Meshik arc to the southwest. In the western Alaska Range, Eocene magmatism included emplacement of the elongate north-south Mer­rill Pass pluton and large volumes of ca. 44–37 Ma andesitic flows, tuffs, and lahar deposits. Finally, a latest Eocene to Oligocene magmatic pulse involved emplacement of a compositionally variable but spatially concentrated suite of magmas ranging from gabbro to peralkaline granite ca. 35–26 Ma, followed by waning magmatism that coincided with initiation of Yakutat shallow-slab subduction. Cretaceous to Oligocene magmatism throughout the western Alaska Range collectively records terrane accretion, translation, and integration together with evolving subduction dynamics that have shaped the southern Alaska margin since the middle Mesozoic.

scholarly journals Oligocene-Neogene lithospheric-scale reactivation of Mesozoic terrane accretionary structures in the Alaska Range suture zone, southern Alaska, USA: Comment

2021 ◽  
Author(s):  
Grant Lowey
Keyword(s):  
Suture Zone ◽  
Ultramafic Rocks ◽  
Metamorphic Rocks ◽  
Geologic Mapping ◽  
Alaska Range ◽  
Denali Fault ◽  
South Central ◽  
Ultramafic Complex ◽  
History Of ◽  
Ultramafic Intrusion

Waldien et al. (2021) present new bedrock geologic mapping, U-Pb geochronology, and 40Ar/39Ar thermochronology from the eastern Alaska Range in south-central Alaska to determine the burial and exhumation history of metamorphic rocks associated with the Alaska Range suture zone, interpret the history of faults responsible for the burial and exhumation of the metamorphic rocks, and speculate on the relative importance of the Alaska Range suture zone and related structures during Cenozoic reactivation. They also propose that ultramafic rocks in their Ann Creek map area in south-central Alaska (herein referred to as the “Ann Creek ultramafic complex”) correlate with the Pyroxenite Creek ultramafic complex in southwestern Yukon, and that this correlation is “consistent with other estimates of >400 km” of offset on the Denali fault. However, despite Waldien et al.’s (2021) claim that the purportedly offset ultramafic rocks are “similar” and that characteristics of the Ann Creek ultramafic complex “make a strong case” for a faulted portion of an Alaska-type ultramafic intrusion, their paper gives short shrift in describing the Pyroxenite Creek ultramafic complex and in discussing previous estimates of displacement on the Denali fault. In Addition, Waldien et al. (2021) are either unaware of or ignore several key references of the Pyroxenite Creek ultramafic complex and estimates of displacement on the Denali fault. As a result, Waldien et al.’s (2021) claim of a “correlation” between allegedly offset ultramafic rocks is suspect, and their reference to “other estimates of >400 km” of offset on the Denali fault is incorrect, or at the very least misleading.

Trace fossils from Late Precambrian Carolina slate belt, south-central North Carolina

1989 ◽  
Vol 63 (1) ◽  
pp. 1-10 ◽  
Author(s):  
Gail G. Gibson
Keyword(s):  
North Carolina ◽  
Trace Fossils ◽  
Middle Cambrian ◽  
Late Precambrian ◽  
Late Proterozoic ◽  
South Central ◽  
Cambrian Trilobite ◽  
Volcanosedimentary Sequence ◽  
Carolina Slate Belt ◽  
Stratigraphic Sequences

The volcanosedimentary sequence of the Carolina slate belt in south-central North Carolina was long thought to be unfossiliferous; however, the 5,484–7,315 meters of dominantly evenly bedded siltstones and mudstones have recently yielded body fossils of the late Precambrian Ediacarian fauna and a Middle Cambrian trilobite assemblage. Ongoing stratigraphic studies in the Carolina slate belt of southern North Carolina have now revealed trace fossils representing the ichnotaxa Gordia arcuata?, ?Helminthopsis sp., Monocraterion sp., Neonerites biserialis, N. uniserialis, ?Neonerites sp., Planolites beverlyensis, P. montanus, ?Planolites sp., Syringomorpha nilssoni?,? Tomaculum sp., Torrowangea sp., and three additional indeterminate ichnogenera. These trace fossils, lacking ornamentation and complex patterns, compare favorably with ichnofossil assemblages from Late Proterozoic stratigraphic sequences (Ichnofossil Zone I) elsewhere and support the late Precambrian age interpretation for the Carolina slate belt in south-central North Carolina.

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