105 Million years of igneous activity, Wrangell, Alaska, to Prince Rupert, British Columbia

2005 ◽  
Vol 42 (6) ◽  
pp. 1097-1116 ◽  
Author(s):  
Maria Luisa Crawford ◽  
William A Crawford ◽  
Jennifer Lindline
Keyword(s):  
British Columbia ◽  
Plate Motion ◽  
Coast Mountains ◽  
Crustal Rocks ◽  
Arc Melting ◽  
Eastern Arc ◽  
Igneous Activity ◽  
History Of ◽  
Terrane Accretion ◽  
Lower Crustal

The Coast Mountains orogen, which lies along coastal British Columbia and southeastern Alaska, records extensive Mesozoic and Cenozoic igneous activity. Here we focus on the two youngest periods: 105–50 Ma and 30 Ma – present. The history of subduction, orogen uplift, and, finally, extension associated with this magmatic activity can be related to plate motion since the mid-Cretaceous. The 105–50 Ma period is related to terrane accretion and subduction. The northwest–southeast-trending Coast shear zone divides the resulting Coast Mountains calc-alkaline continental margin batholith into a western (105–90 Ma) and an eastern (80–50 Ma) arc. Melting of hydrous mantle overlying a dehydrating slab generated the plutons of the western arc. The plutons of the eastern arc show a wider range of compositions. Their origin consists of mantle melts modified by melts from lower crustal rocks of continental affinity and possibly amphibolitic hydrated basalt. In both parts of the arc, igneous bodies also resulted from crustal melting; these are very abundant in the eastern arc. During the younger period bi-modal igneous suites consisting of mantle-derived mafic magmas and coeval crustal melts are associated with crustal extension and block faulting.

Nd isotopic characteristics of metamorphic and plutonic rocks of the Coast Mountains near Prince Rupert, British Columbia

1998 ◽  
Vol 35 (5) ◽  
pp. 556-561 ◽  
Author(s):  
P J Patchett ◽  
G E Gehrels ◽  
C E Isachsen
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Metamorphic Rocks ◽  
Published Data ◽  
Isotopic Data ◽  
Crustal Component ◽  
Coast Mountains ◽  
Crustal Rocks ◽  
Metasedimentary Rocks ◽  
Plutonic Rocks

Nd isotopic data are presented for a suite of metamorphic and plutonic rocks from a traverse across the Coast Mountains between Terrace and Prince Rupert, British Columbia, and for three contrasting batholiths in the Omineca Belt of southern Yukon. A presumed metamorphic equivalent of Jurassic volcanic rocks of the Stikine terrane gives epsilon Nd = +6, and a number of other metaigneous and metasedimentary rocks in the core of the Coast Mountains give epsilon Nd values from +3 to +7. A single metasedimentary rock approximately 3 km east of the Work Channel shear zone gives a epsilon Nd value of -9. Coast Belt plutons in the traverse yield epsilon Nd from -1 to +2. The Omineca Belt plutons give epsilon Nd from -10 to -17. All results are consistent with published data in demonstrating that (i) juvenile origins for both igneous and metamorphic rocks are common in the Coast Belt; (ii) representatives of a continental-margin sedimentary sequence with Precambrian crustal Nd are tectonically interleaved in the Coast Mountains; (iii) Coast Mountains plutons can be interpreted as derived from a blend of metamorphic rocks like those seen at the surface, or as arc-type melts contaminated with the older crustal component; and (iv) Omineca Belt plutons are dominated by remelted Precambrian crustal rocks.

Late Quaternary glacial and interglacial environments of the Nechako River - Cheslatta Lake area, central British Columbia

2001 ◽  
Vol 38 (4) ◽  
pp. 719-731 ◽  
Author(s):  
A Plouffe ◽  
V M Levson
Keyword(s):  
British Columbia ◽  
Late Quaternary ◽  
Late Glacial ◽  
Lake Area ◽  
Glacial Lakes ◽  
Ice Flow ◽  
Coast Mountains ◽  
Quaternary Stratigraphy ◽  
History Of ◽  
Quaternary History

The Quaternary stratigraphy of the Nechako River – Cheslatta Lake area of central British Columbia is described and interpreted to reconstruct the late Quaternary history of the region. Exposures of glacial and nonglacial sediments deposited prior to the last glaciation (Fraser) are limited to three sites. Pollen assemblages from pre-Fraser nonglacial sediments at two of these sites reveal forested conditions around 39 000 BP. During the advance phase of the Fraser Glaciation, glacial lakes were ponded when trunk glaciers blocked some tributary valleys. Early in the glaciation, the drainage was free in easterly draining valleys. Subsequently, the easterly drainage was blocked either locally by sediments and ice or as a result of impoundment of the Fraser River and its tributaries east of the study area. Ice generally moved east and northeast from accumulation zones in the Coast Mountains. Ice flow was influenced by topography. Major late-glacial lakes developed in the Nechako River valley and the Knewstubb Lake region because potential drainage routes were blocked by ice.

Multi-proxy record of Holocene glacial history of the Spearhead and Fitzsimmons ranges, southern Coast Mountains, British Columbia

2007 ◽  
Vol 26 (3-4) ◽  
pp. 479-493 ◽  
Author(s):  
Gerald Osborn ◽  
Brian Menounos ◽  
Johannes Koch ◽  
John J. Clague ◽  
Vanessa Vallis
Keyword(s):  
British Columbia ◽  
Southern Coast ◽  
Glacial History ◽  
Proxy Record ◽  
Coast Mountains ◽  
History Of

Little Ice Age glacial activity in the Mt. Waddington area, British Columbia Coast Mountains, Canada

2003 ◽  
Vol 40 (10) ◽  
pp. 1413-1436 ◽  
Author(s):  
S J Larocque ◽  
D J Smith
Keyword(s):  
British Columbia ◽  
Little Ice Age ◽  
Ice Age ◽  
Climate Forcing ◽  
Medium Size ◽  
Coast Mountains ◽  
Mountain Ranges ◽  
Relative Age ◽  
History Of ◽  
Forcing Mechanisms

The establishment of fourteen Little Ice Age (LIA) glacier chronologies in the Mt. Waddington area led to the development of an extended history of glacial activity in this portion of the southern British Columbia Coast Mountains, Canada. The glaciers were located within four different mountain ranges, and were of varying size and aspect. Dendrochronological and lichenometric techniques were used to provide relative age estimates of moraines formed as glacier termini retreated from advanced positions. Evidence for pre-LIA glacial events is best preserved at Tiedemann Glacier, where the oldest glacial advances date to A.D. 620 and 925–933. Soil-covered and well-vegetated moraines built at Cathedral, Pagoda, and Siva glaciers date to between A.D. 1203 and 1226. Following this event, moraines constructed at Ragnarok, Siva, and Cathedral glaciers in the mid-14th century suggest glaciers in the region underwent a period of downwasting and retreat before readvancing. The majority of moraines recorded in the Mt. Waddington area describe late-LIA glacial events shown to have constructed moraines that date to A.D. 1443–1458, 1506–1524, 1562–1575, 1597–1621, 1657–1660, 1767–1784, 1821–1837, 1871–1900, 1915–1928, and 1942–1946. Over the last 500 years, these moraine-building episodes were shown to occur on average every 65 years and suggest there has been prolonged synchronicity in the glaciological response to persistent climate-forcing mechanisms. Nevertheless, our analysis suggests that local factors, such as aspect and size, play an important role in individual glacial response. Notably, ice termini of medium-size glaciers facing eastwards showed a quicker response to climatically induced mass balance changes.

Late Holocene glacial history of Scimitar Glacier, Mt. Waddington area, British Columbia Coast Mountains, Canada

2013 ◽  
Vol 50 (12) ◽  
pp. 1195-1208 ◽  
Author(s):  
Jessica A. Craig ◽  
Dan J. Smith
Keyword(s):  
British Columbia ◽  
Late Holocene ◽  
Regional Climate ◽  
Ice Age ◽  
Climate Trends ◽  
Glacier Surface ◽  
Coast Mountains ◽  
Standing Trees ◽  
History Of ◽  
Glacial Expansion

Scimitar Glacier originates below the northeast face of Mt. Waddington in the southern British Columbia Coast Mountains and flows 18 km down valley to calve into a proglacial lake. At several locations, downwasting of the glacier surface has exposed stacked till units separated by wood-bearing horizons in the proximal slopes of lateral moraines flanking the glacier. Historical moraine collapse and erosional breaching has also revealed the remains of standing trees buried in moraine-dammed lake sediments. Radiocarbon and tree-ring dating show that Scimitar Glacier expanded down valley at least three times in the late Holocene. The earliest evidence found for ice expansion indicates Scimitar Glacier was advancing in 3167–2737 cal years BP in association with the regional Tiedemann Advance. Following this advance, the glacier downwasted prior to expanding in 1568–1412 cal years BP during the First Millennial Advance. A final period phase of moraine construction was initiated during late Little Ice Age glacial expansion before A.D. 1742 and extended until at least A.D. 1851, after which Scimitar Glacier began to recede and downwaste. This record is comparable to that recorded at other glaciers in the southern British Columbia Coast Mountains and confirms the long-term relationship between regional climate trends and glacier behaviour in this setting.

A Rb–Sr isotopic study of the Archean rocks of the eastern Lac Seul region, English River subprovince, northwestern Ontario

1980 ◽  
Vol 17 (5) ◽  
pp. 569-576 ◽  
Author(s):  
Joseph L. Wooden ◽  
Alan M. Goodwin
Keyword(s):  
Source Region ◽  
Granitic Rocks ◽  
Isotopic Study ◽  
Zircon Age ◽  
Crustal Rocks ◽  
Northwestern Ontario ◽  
Plutonic Complex ◽  
History Of ◽  
Lower Crustal ◽  
Good Agreement

Rb–Sr whole-rock data for the gneissic and granitic rocks of the eastern Lac Seul region, when combined with the U–Pb zircon dating of Krogh, document a history of multiple intrusion for the area. The oldest rocks are the Sen Bay plutonic complex gneisses which have complex Rb–Sr systematics. Interpretation of the Rb–Sr data yields model ages of 3000–3100 Ma which are in good agreement with a zircon age of 3040 Ma. The next oldest rocks are trondhjemitic–granodioritic gneisses with a Rb–Sr age of 2780 ± 90 Ma. The initial Sr ratio (I) of 0.7009 ± 4 for these rocks suggests that this age approximates the time of intrusion and that the magma was derived from lower crustal rocks with a very short residence lime in the crust. Following a period of deformation and metamorphism, granodioritic to granitic dikes, sills, and small plutons were intruded between 2660 and 2560 Ma ago. I values for these racks range from 0.7019–0.7027. If the I values of these rocks represent the source region for the granitic magmas, then one explanation for the I values would be that the magmas were derived from a source region of mixed lithology and age. The Sen Bay plutonic complex is considered to represent an earlier cycle of crustal formation which is distinct from a later 2800–2550 Ma old cycle which dominates much of the Superior Province.

scholarly journals Late Cretaceous to Paleocene Tectonometamorphic Evolution of the Blanchard River Assemblage, Southwest Yukon: New Insight into the Terminal Accretion of Insular Terranes in the Northern Cordillera

Lithosphere ◽  
2020 ◽  
Vol 2020 (1) ◽  
Author(s):  
Lianna Vice ◽  
H. Daniel Gibson ◽  
Steve Israel
Keyword(s):  
British Columbia ◽  
Late Cretaceous ◽  
Amphibolite Facies ◽  
Contact Metamorphism ◽  
Northern Coast ◽  
Coast Mountains ◽  
Tectonic Events ◽  
Western Cordillera ◽  
History Of ◽  
Northwestern North America

Abstract The Intermontane-Insular terrane boundary stretches over 2000 kilometers from British Columbia to Alaska in the western Cordillera. Juxtaposed between these terranes is a series of Jura-Cretaceous basinal and arc assemblages that record a complicated and contested tectonic evolution related to the Mesozoic-Paleocene accretionary history of northwestern North America. In southwest Yukon, west-verging thrust faults facilitated structural stacking of the Yukon-Tanana terrane over these basinal assemblages, including the Early Cretaceous Blanchard River assemblage. These previously undated compressional structures are thought to be related to the final collapse of the Jura-Cretaceous basins and the tectonic burial of the Blanchard River assemblage resulting in amphibolite facies metamorphism. New in situ U-Th-Pb monazite ages record at least three tectonic events: (1) the tectonic burial of the Blanchard River assemblage to amphibolite facies conditions between 83 and 76 Ma; (2) peak burial was followed by regional exhumation at ca. 70-68 Ma; and (3) intense heating and ca. 63-61 Ma low-pressure contact metamorphism attributed to the intrusion of the voluminous Ruby Range suite, which is part of the northern Coast Mountains batholith. The tectonometamorphic evolution recorded in the Blanchard River assemblage can be correlated to tectonism within southwest Yukon and along the length of the Insular-Intermontane boundary from western British Columbia through southwestern Yukon and Alaska. In southwest Yukon, these results suggest an asymmetric final collapse of Jura-Cretaceous basins during the Late Cretaceous, which relates to the terminal accretion of the Insular terranes as they moved northward.

The sedimentary record and Neoglacial history of Tide Lake, northwestern British Columbia

1992 ◽  
Vol 29 (11) ◽  
pp. 2383-2396 ◽  
Author(s):  
John J. Clague ◽  
William H. Mathews
Keyword(s):  
Twentieth Century ◽  
British Columbia ◽  
Ice Age ◽  
Second Phase ◽  
Northern Coast ◽  
Coast Mountains ◽  
Fine Sediments ◽  
Early Twentieth Century ◽  
Outburst Floods ◽  
History Of

Tide Lake was the largest glacier-dammed lake in British Columbia before its demise in the early twentieth century. Situated in the northern Coast Mountains, the lake was impounded by Frank Mackie Glacier and its Neoglacial end moraine. A study of Tide Lake has provided information on styles of glaciolacustrine sedimentation and the chronology of the Neoglacial interval.Much of the sediment underlying the floor of Tide Lake was transported by subglacial and proglacial meltwater streams flowing from nearby glaciers. During the last phase of the lake, large subaqueous fans were built in front of Berendon and Frank Mackie glaciers, and deltas formed on the east side of the basin. Rhythmically bedded fine sediments, which cover much of the lake floor but are almost completely lacking on the slopes above, were deposited from underflows originating on deltas and subaqueous fans and by fallout from interflows and overflows.Three major and one minor lake phases are recognized from stratigraphic, geomorphic, radiocarbon, and dendrochronological data: the earliest phase is undated, but older than 3000 BP (1300 B.C.); the second phase has yielded radiocarbon ages of 2600–2700 BP (800–1000 B.C.); a third, minor phase, during which Tide Lake was restricted to the northern part of the basin, began before 1600 BP (A.D. 350–550) and probably ended a few hundred years later; the last phase may have begun as early as 1000 BP (A.D. 1000–1150), peaked in the seventeenth century, and ended in the early twentieth century. During each of the four phases, Tide Lake fluctuated in a complex fashion and at times was empty. The second phase corresponds to a widely recognized middle Neoglacial advance in western North America; the last phase is coincident with the Little Ice Age. Outburst floods from Tide Lake in the nineteenth and early twentieth centuries devastated Bowser River valley as far downstream as Bowser Lake. The last of the floods occurred around A.D. 1930 when the Frank Mackie moraine was breached and the lake emptied for the last time.

Neoglacial history of the Stikine–Iskut area, northern Coast Mountains, British Columbia

1987 ◽  
Vol 24 (7) ◽  
pp. 1294-1301 ◽  
Author(s):  
J. M. Ryder
Keyword(s):  
British Columbia ◽  
Aerial Photograph ◽  
Northern Coast ◽  
Historical Records ◽  
Radiocarbon Dates ◽  
Coast Mountains ◽  
Low Level ◽  
The Past ◽  
History Of ◽  
Late Nineteenth

Information about Neoglacial features was obtained from aerial photograph interpretation, observations during low-level flights, ground checking, and historical records. Terminal moraines at Great, Flood, and Mud glaciers date from the late seventeenth to early eighteenth centuries, and recessional moraines at these glaciers and terminal moraines at glaciers farther east date from the late nineteenth to early twentieth centuries. These late Neoglacial terminal moraines appear, in general, to mark the greatest post-Pleistocene extent of the glaciers. Radiocarbon dates from overridden trees and soil indicate that 500–600 14C years BP glaciers were considerably more extensive than they are at present and were advancing. Preservation of a 3800 14C year old caribou antler in a snowbank that is now rapidly shrinking suggests that climate has been relatively cool and moist for the past four millennia.

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