Paleomagnetism of Cretaceous and Paleocene Sedimentary Rocks Across the Castle Mountain Fault, South Central Alaska

2013 ◽  
pp. 151-177 ◽  
Author(s):  
John A. Stamatakos ◽  
K. P. Kodama ◽  
L. F. Vittorio ◽  
T. L. Pavlis
Keyword(s):  
Sedimentary Rocks ◽  
South Central ◽  
Castle Mountain Fault

Provenance of Jurassic sedimentary rocks of south-central Quesnellia, British Columbia: implications for paleogeography

2004 ◽  
Vol 41 (1) ◽  
pp. 103-125 ◽  
Author(s):  
Nathan T Petersen ◽  
Paul L Smith ◽  
James K Mortensen ◽  
Robert A Creaser ◽  
Howard W Tipper
Keyword(s):  
Detrital Zircon ◽  
Middle Jurassic ◽  
Sedimentary Rocks ◽  
Source Area ◽  
Lower Jurassic ◽  
Early Jurassic ◽  
Late Triassic ◽  
Nd Isotopes ◽  
South Central ◽  
History Of

Jurassic sedimentary rocks of southern to central Quesnellia record the history of the Quesnellian magmatic arc and reflect increasing continental influence throughout the Jurassic history of the terrane. Standard petrographic point counts, geochemistry, Sm–Nd isotopes and detrital zircon geochronology, were employed to study provenance of rocks obtained from three areas of the terrane. Lower Jurassic sedimentary rocks, classified by inferred proximity to their source areas as proximal or proximal basin are derived from an arc source area. Sandstones of this age are immature. The rocks are geochemically and isotopically primitive. Detrital zircon populations, based on a limited number of analyses, have homogeneous Late Triassic or Early Jurassic ages, reflecting local derivation from Quesnellian arc sources. Middle Jurassic proximal and proximal basin sedimentary rocks show a trend toward more evolved mature sediments and evolved geochemical characteristics. The sandstones show a change to more mature grain components when compared with Lower Jurassic sedimentary rocks. There is a decrease in εNdT values of the sedimentary rocks and Proterozoic detrital zircon grains are present. This change is probably due to a combination of two factors: (1) pre-Middle Jurassic erosion of the Late Triassic – Early Jurassic arc of Quesnellia, making it a less dominant source, and (2) the increase in importance of the eastern parts of Quesnellia and the pericratonic terranes, such as Kootenay Terrane, both with characteristically more evolved isotopic values. Basin shale environments throughout the Jurassic show continental influence that is reflected in the evolved geochemistry and Sm–Nd isotopes of the sedimentary rocks. The data suggest southern Quesnellia received material from the North American continent throughout the Jurassic but that this continental influence was diluted by proximal arc sources in the rocks of proximal derivation. The presence of continent-derived material in the distal sedimentary rocks of this study suggests that southern Quesnellia is comparable to known pericratonic terranes.

Effect of rock strength on exhumation and the thermochronologic record: The south-central Colorado example

2021 ◽  
Author(s):  
Sabrina Kainz ◽  
Lon Abbott ◽  
Rebecca Flowers ◽  
James Metcalf
Keyword(s):  
Low Temperature ◽  
Sedimentary Rock ◽  
Rock Strength ◽  
Sedimentary Rocks ◽  
Sedimentary Basins ◽  
Crystalline Basement ◽  
Precambrian Basement ◽  
The West ◽  
South Central ◽  
Sangre De Cristo

<p>Past work has used the Southern Rocky Mountains (SRM) in the U.S. state of Colorado to illustrate the important role that rock strength plays in the histories recorded by the apatite fission track (AFT) and apatite (U-Th)/He (AHe) low-temperature thermochronometers (Flowers & Ehlers, 2018). The SRM were initially raised during the Laramide Orogeny, ca. 70-45 Ma, but consensus exists that the region also experienced a later, post-Laramide exhumation event. Flowers & Ehlers (2018) pointed to the low erosion potential of the Precambrian crystalline basement rocks that crop out in most SRM ranges as a primary reason for the abundance of 55-70 Ma “Laramide” AFT and AHe dates in the region, compared to a paucity of younger dates that would presumably be produced through erosion triggered by the post-Laramide exhumation event. South-central Colorado offers a test of this hypothesis, due to lateral variations in rock erodibility provided by the presence here of both sedimentary and crystalline Laramide ranges and adjacent sedimentary basins. The combination of our ongoing AHe study with previous south-central Colorado AFT and AHe work reveals kilometer-scale post-Laramide (Oligo-Miocene) exhumation has occurred in areas that possess thick sedimentary rock sequences whereas exhumation has been negligible where crystalline basement comprises the land surface. </p><p>South-central Colorado’s Sangre de Cristo Mountains consist of an imbricate stack of thrust sheets composed of Permian sedimentary rock. About 30 km farther east stand the Wet Mountains, another Laramide range – but one composed of Precambrian basement rock. The Raton Basin, a SRM foreland basin filled with 2 km of synorogenic fill underlain by a thick sequence of marine shale, lies south and east of the two ranges. The Wet Mountains thus form a peninsula of strong crystalline rock surrounded by more erodible sedimentary rocks to the west, south, and east. </p><p>Our study and that of Landman (2018) records at least 2 km of erosion in the Raton Basin east and south of the Wet Mountains since 25 Ma. Lindsey et al (1986) obtained 24-15 Ma AFT dates from the Paleozoic sedimentary rocks of the Sangre de Cristo Mountains, demonstrating that kilometer-scale Oligo-Miocene exhumation occurred just west of the Wet Mountains. By contrast, Kelley and Chapin (2004) obtained only pre-Laramide AFT ages between 228-110 Ma for 17 samples of Precambrian basement from the crest of the Wet Mountains. A 32 Ma ash flow tuff unconformably overlies Precambrian basement on Greenhorn Mountain, the Wet Mountains’ highest and southernmost peak. Its presence reinforces the conclusion, based on the AFT dates, that Oligo-Miocene erosion of the Wet Mountain massif has been minimal simultaneous with kilometer-scale exhumation to the west, south, and east. These results illustrate the important role that rock strength plays in determining the dates recorded in low-temperature thermochronologic studies.</p>

Evolution of the south-central segment of the Archean Abitibi Belt, Quebec. Part II: Tectonic evolution and geomechanical model

1983 ◽  
Vol 20 (9) ◽  
pp. 1355-1373 ◽  
Author(s):  
Erich Dimroth ◽  
Lazlo Imreh ◽  
Normand Goulet ◽  
Michel Rocheleau
Keyword(s):  
Tectonic Evolution ◽  
Anisotropic Plate ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Normal Fault ◽  
Geomechanical Model ◽  
Southwestern Part ◽  
South Central ◽  
Central Segment ◽  
Volcanic Terrain

In this paper, we describe the relations between the paleogeographic and tectonic evolution of the southwestern part of the Archean Abitibi and Bellecombe belts. Volcanism in the Abitibi Belt created a very thick, anisotropic plate composed of competent volcanic rocks and broken by the Duparquet–Destor break. The depocenters of the upper division of diverse volcanic rocks subsided about 10 km relative to their surroundings, and some central volcanic complexes within this division were consolidated by synvolcanic plutons and their thermal metamorphic aureole. The Cadillac break, a normal fault, separated the Abitibi and Bellecombe belts. The latter consisted of comparatively incompetent sedimentary rocks on top of a basement composed of ultramafic–mafic flows.North–south compression of the volcanic terrain during the Kenoran Orogeny produced a set of flexure folds, F1, that curve around the consolidated cores of central volcanic complexes generally in an easterly direction. Synclinoria nucleated at the deeply subsident depocenters of the upper diverse division. Further north–south flattening and subvertical stretching produced the east-trending F2 folds, their axial-plane schistosity S2, and local superposed schistosities S3 and S4. Southward verging recumbent folds suggest that the Bellecombe Belt simultaneously was pulled northward below the Abitibi Belt. During the orogeny, the Duparquet–Destor and Cadillac breaks were transformed to thrust faults; the Duparquet–Destor break also shows minor (< 3 km) right-lateral strike slip. Diapiric rise of late- to post-kinematic plutons locally distorted earlier schistosities.

scholarly journals Petrography and Provenance Study of South-Central Part of Kaladgi Basin, Belgaum, Karnataka, India

2020 ◽  
Vol 11 (1) ◽  
pp. 108-112
Author(s):  
Anant G. Pujar ◽  
A. Sreenivasa ◽  
Ajaykumar N. Asode
Keyword(s):  
Sedimentary Rocks ◽  
Ternary Diagram ◽  
Point Of View ◽  
Provenance Study ◽  
The South ◽  
Rock Samples ◽  
South Central ◽  
Microscopic Studies

The area under investigation covers the south-central part of Kaladgi series comprising of sedimentary rocks, mainly quartzarenites. From the geological point of view the study area comprises southcentral part of Kaladgi basin covering around 54 km2 which encompasses rocky hills of moderate height, showing three types of facies i.e., argillaceous, arenaceous and rudaceous. Among these three, arenaceous facies is more prominent in the area. These sedimentary rocks rest unconformably over gneisses. Detailed study of the rocks exposed are done by studying the petrological aspects of the rock samples which were subjected to microscopic studies, bifurcating different minerals and counting each parameter of the minerals which is plotted in the QFR ternary diagram and further illustrating the tectonic provenance of the area. Present work mainly focuses on the studies related to petrological, diagenesis and provenance of the study area where the rocks exposed in the vicinity are quartz arenites indicating that these sediments were deposited in a riverine condition.

scholarly journals Petrography and Provenance Study of South-Central Part of Kaladgi Basin, Belgaum, Karnataka, India

2020 ◽  
Vol 11 (1) ◽  
pp. 108-112
Author(s):  
Anant G. Pujar ◽  
A. Sreenivasa ◽  
Ajaykumar N. Asode
Keyword(s):  
Sedimentary Rocks ◽  
Ternary Diagram ◽  
Point Of View ◽  
Provenance Study ◽  
The South ◽  
Rock Samples ◽  
South Central ◽  
Microscopic Studies

The area under investigation covers the south-central part of Kaladgi series comprising of sedimentary rocks, mainly quartzarenites. From the geological point of view the study area comprises southcentral part of Kaladgi basin covering around 54 km2 which encompasses rocky hills of moderate height, showing three types of facies i.e., argillaceous, arenaceous and rudaceous. Among these three, arenaceous facies is more prominent in the area. These sedimentary rocks rest unconformably over gneisses. Detailed study of the rocks exposed are done by studying the petrological aspects of the rock samples which were subjected to microscopic studies, bifurcating different minerals and counting each parameter of the minerals which is plotted in the QFR ternary diagram and further illustrating the tectonic provenance of the area. Present work mainly focuses on the studies related to petrological, diagenesis and provenance of the study area where the rocks exposed in the vicinity are quartz arenites indicating that these sediments were deposited in a riverine condition.

scholarly journals Cenozoic tectono-thermal history of the southern Talkeetna Mountains, Alaska: Insights into a potentially alternating convergent and transform plate margin

Geosphere ◽  
2019 ◽  
Vol 15 (5) ◽  
pp. 1539-1576 ◽  
Author(s):  
Patrick J. Terhune ◽  
Jeffrey A. Benowitz ◽  
Jeffrey M. Trop ◽  
Paul B. O’Sullivan ◽  
Robert J. Gillis ◽  
...  
Keyword(s):  
Fault System ◽  
Mountain Range ◽  
Spreading Ridge ◽  
Primary Role ◽  
Ridge Subduction ◽  
South Central ◽  
Slab Breakoff ◽  
History Of ◽  
Talkeetna Mountains ◽  
Castle Mountain Fault

Abstract The Mesozoic–Cenozoic convergent margin history of southern Alaska has been dominated by arc magmatism, terrane accretion, strike-slip fault systems, and possible spreading-ridge subduction. We apply 40Ar/39Ar, apatite fission-track (AFT), and apatite (U-Th)/He (AHe) geochronology and thermochronology to plutonic and volcanic rocks in the southern Talkeetna Mountains of Alaska to document regional magmatism, rock cooling, and inferred exhumation patterns as proxies for the region’s deformation history and to better delineate the overall tectonic history of southern Alaska. High-temperature 40Ar/39Ar thermochronology on muscovite, biotite, and K-feldspar from Jurassic granitoids indicates postemplacement (ca. 158–125 Ma) cooling and Paleocene (ca. 61 Ma) thermal resetting. 40Ar/39Ar whole-rock volcanic ages and 45 AFT cooling ages in the southern Talkeetna Mountains are predominantly Paleocene–Eocene, suggesting that the mountain range has a component of paleotopography that formed during an earlier tectonic setting. Miocene AHe cooling ages within ∼10 km of the Castle Mountain fault suggest ∼2–3 km of vertical displacement and that the Castle Mountain fault also contributed to topographic development in the Talkeetna Mountains, likely in response to the flat-slab subduction of the Yakutat microplate. Paleocene–Eocene volcanic and exhumation-related cooling ages across southern Alaska north of the Border Ranges fault system are similar and show no S-N or W-E progressions, suggesting a broadly synchronous and widespread volcanic and exhumation event that conflicts with the proposed diachronous subduction of an active west-east–sweeping spreading ridge beneath south-central Alaska. To reconcile this, we propose a new model for the Cenozoic tectonic evolution of southern Alaska. We infer that subparallel to the trench slab breakoff initiated at ca. 60 Ma and led to exhumation, and rock cooling synchronously across south-central Alaska, played a primary role in the development of the southern Talkeetna Mountains, and was potentially followed by a period of southern Alaska transform margin tectonics.

Upper Paleozoic rocks of the western Canadian Cordillera and their bearing on Cordilleran evolution

1977 ◽  
Vol 14 (8) ◽  
pp. 1832-1859 ◽  
Author(s):  
J. W. H. Monger
Keyword(s):  
British Columbia ◽  
Pacific Ocean ◽  
Sedimentary Rocks ◽  
Ocean Floor ◽  
Canadian Cordillera ◽  
Island Arcs ◽  
South Central ◽  
Early Mesozoic ◽  
Basic Volcanics ◽  
Paleozoic Rocks

Volcanic and sedimentary successions of late Paleozoic and locally Mesozoic age in the Canadian Cordillera form six assemblages, based mainly on lithological association and similar stratigraphy. From east to west these assemblages are: (1) Eastern assemblage, located along the Omineca Crystalline Belt and consisting of Mississippian to Permian largely sedimentary rocks overlain by mainly Permian basic volcanics and ultramafics; (2) poorly known rocks in south-central British Columbia characterized by abundant volcaniclastics of Pennsylvanian and Permian ages; (3) Cache Creek – Bridge River assemblage of the Intermontane Bell, ranging from Lower Mississippian to Middle Jurassic and composed of chert, argillite, carbonate, basic volcanics, and ultramafics: (4) Stikine assemblage of northwestern and north-central British Columbia of Mississippian and Permian age, with basic to acidic volcanics, argillite, and carbonate; (5) Chilliwack Group on the west side of the Cascade Mountains, of Pennsylvanian and Permian age, with basic to acidic volcanics overlying a carbonate and clastic succession: and (6) Sicker–Skolai assemblage of Vancouver Island and the Saint Elias Mountains with basic to acidic volcanics overlain by sedimentary rocks. Coeval faunas in several of these assemblages differ. The assemblages may be largely unrelated to one another and came together in the Mesozoic, Their present distribution, with rocks typical of ocean basins (assemblages 1, 3) east of rocks that probably represent island arcs (assemblages, 2, 4, 5, 6) presents major problems. Two hypotheses attempt to explain this distribution. (1) The oceanic assemblages represent Paleozoic and early Mesozoic Pacific Ocean floor obducted over a broad arc terrane in the Jurassic, or (2) they are Paleozoic and early Mesozoic Pacific Ocean floor, trapped east of allochthonous arc terranes (assemblages 4, 5, 6) emplaced in the Mesozoic.

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