Stikinia
Encyclopedia
Stikinia is the name of a tectonostratigraphic terrane
in the Canadian Cordillera of British Columbia
, Canada
. It was formed in a volcanic arc
environment during the Paleozoic
and Mesozoic
periods. Until now, the Paleozoic rocks that form a semicontinuous belt along its western margin (Stikine assemblage) were only recognized in a restricted area in northern British Columbia, between the Stikine and Taku river areas. In contrast, Mesozoic Stikinia rocks form an almost continuous belt that extends much farther to the north, leading some authors to question the nature of the unexposed Paleozoic basement north of the Taku River area. The following correlations have significant implications for tectonic reconstructions of the northern Cordillera because they suggest that Stikinia's Paleozoic volcanic-sedimentary basement is more widespread than previously thought.
On the basis of similar rock types and lithologic associations, six new uranium
-lead
zircon
dates, and the common intrusive
relationship with 184–195 million year old pluton
s, the Stikine assemblage is correlated with the Boundary Ranges suite, a metamorphosed Paleozoic volcanic assemblage exposed in the Tagish Lake area, north of the Taku River and south of the Yukon–British Columbia border. The recognition of the Boundary Ranges
suite and the Jurassic
plutons that intruded it (Tagish Lake suite) as part of Stikinia has implications for the age and character of the Stikinia–Tracy Arm terrane boundary because the Boundary Ranges and Tagish Lake
suites form the footwall of a major Middle Jurassic shear zone that carried the continental margin–like rocks of the Tracy Arm terrane in its hanging wall. This correlation also implies that the late Paleozoic basement to the Mesozoic Stikinia arc is not a continental margin assemblage, at least as far north as the British Columbia–Yukon border, and possibly farther. The Boundary Ranges suite, and therefore the Stikine assemblage, are also tentatively correlated with parts of the Yukon-Tanana Terrane
in Yukon (Aishihik Lake area), parts of the Taku terrane in southeast Alaska, and undivided metamorphic rock
s in west-central British Columbia. Differences in the isotopic signatures of these rocks may reflect along-strike changes in the character of the basement rocks of the late Paleozoic Stikinia volcanic arc.
Stikinia forms the bedrock of numerous volcanoes in the southern portion of the Northern Cordilleran Volcanic Province
, a Miocene
to Holocene
geologic province
that has its origins in continental rifting.
Terrane
A terrane in geology is short-hand term for a tectonostratigraphic terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate...
in the Canadian Cordillera of British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. It was formed in a volcanic arc
Volcanic arc
A volcanic arc is a chain of volcanoes positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic island arc. Generally they result from the subduction of an oceanic tectonic plate under another tectonic plate, and often parallel an oceanic trench...
environment during the Paleozoic
Paleozoic
The Paleozoic era is the earliest of three geologic eras of the Phanerozoic eon, spanning from roughly...
and Mesozoic
Mesozoic
The Mesozoic era is an interval of geological time from about 250 million years ago to about 65 million years ago. It is often referred to as the age of reptiles because reptiles, namely dinosaurs, were the dominant terrestrial and marine vertebrates of the time...
periods. Until now, the Paleozoic rocks that form a semicontinuous belt along its western margin (Stikine assemblage) were only recognized in a restricted area in northern British Columbia, between the Stikine and Taku river areas. In contrast, Mesozoic Stikinia rocks form an almost continuous belt that extends much farther to the north, leading some authors to question the nature of the unexposed Paleozoic basement north of the Taku River area. The following correlations have significant implications for tectonic reconstructions of the northern Cordillera because they suggest that Stikinia's Paleozoic volcanic-sedimentary basement is more widespread than previously thought.
On the basis of similar rock types and lithologic associations, six new uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
-lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
zircon
Zircon
Zircon is a mineral belonging to the group of nesosilicates. Its chemical name is zirconium silicate and its corresponding chemical formula is ZrSiO4. A common empirical formula showing some of the range of substitution in zircon is 1–x4x–y...
dates, and the common intrusive
Intrusion
An intrusion is liquid rock that forms under Earth's surface. Magma from under the surface is slowly pushed up from deep within the earth into any cracks or spaces it can find, sometimes pushing existing country rock out of the way, a process that can take millions of years. As the rock slowly...
relationship with 184–195 million year old pluton
Pluton
A pluton in geology is a body of intrusive igneous rock that crystallized from magma slowly cooling below the surface of the Earth. Plutons include batholiths, dikes, sills, laccoliths, lopoliths, and other igneous bodies...
s, the Stikine assemblage is correlated with the Boundary Ranges suite, a metamorphosed Paleozoic volcanic assemblage exposed in the Tagish Lake area, north of the Taku River and south of the Yukon–British Columbia border. The recognition of the Boundary Ranges
Boundary Ranges
The Boundary Ranges, also known in the singular and as the Alaska Boundary Range, are the largest and most northerly subrange of the Coast Mountains...
suite and the Jurassic
Jurassic
The Jurassic is a geologic period and system that extends from about Mya to Mya, that is, from the end of the Triassic to the beginning of the Cretaceous. The Jurassic constitutes the middle period of the Mesozoic era, also known as the age of reptiles. The start of the period is marked by...
plutons that intruded it (Tagish Lake suite) as part of Stikinia has implications for the age and character of the Stikinia–Tracy Arm terrane boundary because the Boundary Ranges and Tagish Lake
Tagish Lake
Tagish Lake is a lake in the Yukon Territory and northern British Columbia, Canada. The lake is more than long and about 2 km wide.It has two arms, the Taku Arm in the east which is very long and mostly in British Columbia and Windy Arm in the west, mostly in the Yukon. The Klondike Highway runs...
suites form the footwall of a major Middle Jurassic shear zone that carried the continental margin–like rocks of the Tracy Arm terrane in its hanging wall. This correlation also implies that the late Paleozoic basement to the Mesozoic Stikinia arc is not a continental margin assemblage, at least as far north as the British Columbia–Yukon border, and possibly farther. The Boundary Ranges suite, and therefore the Stikine assemblage, are also tentatively correlated with parts of the Yukon-Tanana Terrane
Yukon-Tanana Terrane
The Yukon-Tanana Terrane is a tectonic terrane that extends from central Alaska through central Yukon and into northern British Columbia, Canada and Southeast Alaska, USA. Extending over 2000 km, the YTT is the largest tectonostratigraphic terrane in the northern North American Cordillera...
in Yukon (Aishihik Lake area), parts of the Taku terrane in southeast Alaska, and undivided metamorphic rock
Metamorphic rock
Metamorphic rock is the transformation of an existing rock type, the protolith, in a process called metamorphism, which means "change in form". The protolith is subjected to heat and pressure causing profound physical and/or chemical change...
s in west-central British Columbia. Differences in the isotopic signatures of these rocks may reflect along-strike changes in the character of the basement rocks of the late Paleozoic Stikinia volcanic arc.
Stikinia forms the bedrock of numerous volcanoes in the southern portion of the Northern Cordilleran Volcanic Province
Northern Cordilleran volcanic province
The Northern Cordilleran Volcanic Province , formerly known as the Stikine Volcanic Belt, is a geologic province defined by the occurrence of Miocene to Holocene volcanoes in the Pacific Northwest of North America...
, a Miocene
Miocene
The Miocene is a geological epoch of the Neogene Period and extends from about . The Miocene was named by Sir Charles Lyell. Its name comes from the Greek words and and means "less recent" because it has 18% fewer modern sea invertebrates than the Pliocene. The Miocene follows the Oligocene...
to Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
geologic province
Geologic province
A geologic or geomorphic province is a spatial entity with common geologic or geomorphic attributes. A province may include a single dominant structural element such as a basin or a fold belt, or a number of contiguous related elements...
that has its origins in continental rifting.
See also
- Takla GroupTakla GroupThe Takla Group is a group of basalt and andesite lava flows, pyroclastic rocks, volcanogenetic sandstones and argillites in north-central British Columbia, Canada, covering more than of the Stikinia terrane in a belt up to wide and over long.-See also:...
- Volcanism of Canada
- Volcanism of Western CanadaVolcanism of Western CanadaVolcanism of Western Canada produces lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes and maars, along with examples of more less common volcanic forms such as tuyas and subglacial mounds.-Volcanic belts:*Anahim...
- Volcanism of Northern CanadaVolcanism of Northern CanadaVolcanism of Northern Canada has led to the formation of hundreds of volcanic areas and extensive lava formations across Northern Canada, indicating volcanism played a major role in shaping its surface...