Geology of Newfoundland and Labrador
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Newfoundland and Labrador Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...
includes basement rocks formed as part of the Grenville Province in the west and Labrador and the Avalonian microcontinent in the east. Extensive tectonic changes, metamorphism and volcanic activity have formed the region throughout Earth history.


Newfoundland

In contrast to neighboring Labrador, the island of Newfoundland is largely underlain by younger rocks. The Churchill, Nain, Superior and Grenville Province present in Labrador were all small continents or pieces of continental lithosphere that joined to form sections of the proto-North American continent
Laurentia Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of North America. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although ...
and the broad stable region known as the
Canadian Shield The Canadian Shield (french: Bouclier canadien ), also called the Laurentian Plateau, is a geologic shield, a large area of exposed Precambrian igneous and high-grade metamorphic rocks. It forms the North American Craton (or Laurentia), the anc ...
. By the end of the
Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...
in the
Neoproterozoic The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago. It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is ...
, continental crust which had come into existence in the
Archean The Archean Eon ( , also spelled Archaean or Archæan) is the second of four geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic. The Earth Earth ...
nearly 2.5 billion years had already experienced up to eight supercontinent cycles. In the late Precambrian and
Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...
,
Avalonia Avalonia was a microcontinent in the Paleozoic era. Crustal fragments of this former microcontinent underlie south-west Great Britain, southern Ireland, and the eastern coast of North America. It is the source of many of the older rocks of Wester ...
(named after the Avalon Peninsula in Newfoundland) formed as a volcanic island arc off the coast of the supercontinents
Pannotia Pannotia (from Greek: '' pan-'', "all", '' -nótos'', "south"; meaning "all southern land"), also known as the Vendian supercontinent, Greater Gondwana, and the Pan-African supercontinent, was a relatively short-lived Neoproterozoic supercontinent ...
which lost land through rifting and became
Gondwana Gondwana () was a large landmass, often referred to as a supercontinent, that formed during the late Neoproterozoic (about 550 million years ago) and began to break up during the Jurassic period (about 180 million years ago). The final stages ...
. This volcanic island arc was later split into different areas, but currently underlies southern New England, Maine, Nova Scotia, Prince Edward Island, southern New Brunswick, southern Ireland, England, Wales, Belgium, the Netherlands and much of north Germany. Northwest Newfoundland includes older rocks affected by the
Grenville orogeny The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, ...
in the late
Proterozoic The Proterozoic () is a geological eon spanning the time interval from 2500 to 538.8million years ago. It is the most recent part of the Precambrian "supereon". It is also the longest eon of the Earth's geologic time scale, and it is subdivided ...
during the collision of continents to form the previous supercontinent
Rodinia Rodinia (from the Russian родина, ''rodina'', meaning "motherland, birthplace") was a Mesoproterozoic and Neoproterozoic supercontinent that assembled 1.26–0.90 billion years ago and broke up 750–633 million years ago. were probably ...
. Examples of ancient rocks from this period include the late Precambrian Harbour Main Group
ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surrou ...
and ash flow
tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...
with
obsidian Obsidian () is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Obsidian is produced from felsic lava, rich in the lighter elements s ...
and
augite Augite is a common rock-forming pyroxene mineral with formula . The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees. Characteristics Augite is a solid solution in the pyroxene group. ...
in the center of the Avalon Peninsula. Rocks of similar age were forming on Grenville Province basement rock in what would become western Newfoundland, such as the Round Pond Granite formed 602 million years ago. Sedimentary and volcanic rocks 15 kilometers thick are exposed in the Avalon Peninsula, deposited in rift basins as
flysch Flysch () is a sequence of sedimentary rock layers that progress from deep-water and turbidity flow deposits to shallow-water shales and sandstones. It is deposited when a deep basin forms rapidly on the continental side of a mountain building ep ...
and
molasse __NOTOC__ The term "molasse" () refers to sandstones, shales and conglomerates that form as terrestrial or shallow marine deposits in front of rising mountain chains. The molasse deposits accumulate in a foreland basin, especially on top of flys ...
with volcaniclastic rocks in submarine fans. The Gaskiers Formation holds
diamictite Diamictite (; from Ancient Greek ''δια'' (dia-): ''through'' and ''µεικτός'' (meiktós): ''mixed'') is a type of lithified sedimentary rock that consists of nonsorted to poorly sorted terrigenous sediment containing particles that ra ...
that may have formed during the
Snowball Earth The Snowball Earth hypothesis proposes that, during one or more of Earth's Greenhouse and icehouse Earth, icehouse Climate, climates, the Earth's surface, planet's surface became entirely or nearly entirely Freezing, frozen. It is believed that ...
glaciations and
Ediacaran The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and th ...
fossils and microfossils have been found in some rocks. Northern Newfoundland at the edge of the Laurentian continent witnessed columnar flood basalts in the Cloud Hills area into the
Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...
. The Avalon Zone is an area of 550 million year old sedimentary and volcanic rocks exposed only in the east that preserves the original geology of the microcontinent and extends 600 kilometers out to sea forming the below water Flemish Cap. By the early
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...
, the Avalonia microcontinent and the
Bronson Hill island arc The Bronson Hill Arc is a bimodal volcanic arc and associated sediments that formed over a west (?) dipping subduction zone during the Ordovician period (c. 475 - 450 million years ago (Ma)) as part of the Taconic Orogeny. These rocks are present ...
, collided with Laurentia to form the mid-sized continent
Euramerica Laurasia () was the more northern of two large landmasses that formed part of the Pangaea supercontinent from around ( Mya), the other being Gondwana. It separated from Gondwana (beginning in the late Triassic period) during the breakup of Pan ...
, causing the
Taconic orogeny The Taconic orogeny was a mountain building period that ended 440 million years ago and affected most of modern-day New England. A great mountain chain formed from eastern Canada down through what is now the Piedmont of the East coast of the Unit ...
. The collision closed the
Iapetus Ocean The Iapetus Ocean (; ) was an ocean that existed in the late Neoproterozoic and early Paleozoic eras of the geologic timescale (between 600 and 400 million years ago). The Iapetus Ocean was situated in the southern hemisphere, between the paleoco ...
and obducted the Laurentian continental margin under the two island arcs. The process produced a strange bulged up area of mantle material to the surface as
peridotite Peridotite ( ) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg2+), reflecting the high prop ...
in
Gros Morne National Park Gros Morne National Park is a National Parks of Canada, Canadian national park and World Heritage Site located on the west coast of Newfoundland and Labrador, Newfoundland. At , it is the second largest national park in Atlantic Canada after To ...
, essentially the only area on the Earth's surface where mantle material is present as cool, crystallized rock. It also created an
ophiolite An ophiolite is a section of Earth's oceanic crust and the underlying upper mantle that has been uplifted and exposed above sea level and often emplaced onto continental crustal rocks. The Greek word ὄφις, ''ophis'' (''snake'') is found i ...
zone where oceanic crust was preserved on land. Geologists group the rocks in this area into the Humber Zone and the Dunnage Zone, with the Dunnage Zone's southern edge defined by the Gander River Ultrabasic Belt. The neighboring Gander Zone has siltstone, shale and quartz sandstone as well as deformed rocks and granite. The sediments were deposited on the continental margin during the closure of the Iapetus Ocean. By 356 million years ago, Gondwana collided with Euramerica, closing the Rheic Ocean and creating the supercontinent
Pangea Pangaea or Pangea () was a supercontinent that existed during the late Paleozoic and early Mesozoic eras. It assembled from the earlier continental units of Gondwana, Euramerica and Siberia during the Carboniferous approximately 335 million y ...
, which left Newfoundland and the Avalonian microcontinent (also known as terrane) far inland and brought widespread interior desert conditions around the world. Newfoundland was re-exposed to the ocean in the
Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest period ...
when rifting began to form new oceanic crust and opened the Atlantic Ocean.


Labrador

Labrador is part of the eastern
Canadian Shield The Canadian Shield (french: Bouclier canadien ), also called the Laurentian Plateau, is a geologic shield, a large area of exposed Precambrian igneous and high-grade metamorphic rocks. It forms the North American Craton (or Laurentia), the anc ...
and intrusive igneous or metamorphic rocks are the most common, with sedimentary rocks in some areas. Four of the seven Canadian Shield provinces make up Labrador.
Archean The Archean Eon ( , also spelled Archaean or Archæan) is the second of four geologic eons of Earth's history, representing the time from . The Archean was preceded by the Hadean Eon and followed by the Proterozoic. The Earth Earth ...
age rocks and east-west structural trends mark the
Superior Province The Superior Craton is a stable fault block, crustal block covering Quebec, Ontario, and southeast Manitoba in Canada, and northern Minnesota in the United States. It is the biggest craton among those formed during the Archean period. A craton is ...
(a small area in the west near Quebec) which encompasses the Ashuanipi Complex
granulite Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism. They are medium to coarse–grained and mainly composed of feldspars sometimes associated w ...
and
granodiorite Granodiorite () is a coarse-grained (phaneritic) intrusive igneous rock similar to granite, but containing more plagioclase feldspar than orthoclase feldspar. The term banatite is sometimes used informally for various rocks ranging from gra ...
intruded by
pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...
-rich felsic plutons. The Nain Province runs along the northeast coast and also has Archean-age rocks, although a greater northward trend. The only exception is
gneiss Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...
overlain by metasedimentary and metavolcanic rocks in the southeast, which were recrystallized and metamorphosed during 1.42 billion year old orogeny. A major
anorthosite Anorthosite () is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most c ...
-
adamellite Quartz monzonite is an intrusive, felsic, igneous rock that has an approximately equal proportion of orthoclase and plagioclase feldspars. It is typically a light colored phaneritic (coarse-grained) to porphyritic granitic rock. The plagioclas ...
pluton intrudes the province. South of the Davis Inlet, the Hopedale Gneiss is the defining rock unit. Nain Archean gneiss is overlain to the north of the community of
Nain, Newfoundland and Labrador Nain (Inuit language: ''Nunainguk'') is the northernmost permanent settlement in the Canadian province of Newfoundland and Labrador, within the Nunatsiavut region, located about by air from Happy Valley-Goose Bay. The town was established as a Mo ...
by the undeformed Ramah Group shale, sandstone and quartzite from the Aphebian. The Mugford Group
tholeiite The tholeiitic magma series is one of two main magma series in subalkaline igneous rocks, the other being the calc-alkaline series. A magma series is a chemically distinct range of magma compositions that describes the evolution of a mafic magma i ...
basalts and pyroclastic flows overlie similar sedimentary rocks. The volcanic rocks are between 1.49 and 2.3 billion years old. The Nain Province is subdivided into the Makkovik-subprovince, which is mainly made up of the 25,000 foot thick Aillik Group quartzofeldspathic, argillite, limestone, conglomerate, paragneiss and iron formations. The Churchill Province is situated inland in north-central Labrador and was deformed during the
Hudsonian orogeny The Trans-Hudson orogeny or Trans-Hudsonian orogeny was the major mountain building event ( orogeny) that formed the Precambrian Canadian Shield and the North American Craton (also called Laurentia), forging the initial North American conti ...
. Anorthosite intrusions partly obscure it in places, but a
mylonite Mylonite is a fine-grained, compact metamorphic rock produced by dynamic recrystallization of the constituent minerals resulting in a reduction of the grain size of the rock. Mylonites can have many different mineralogical compositions; it is a cl ...
zone marks it northern boundary. Structural geologists divide it into the undeformed sedimentary and volcanic rocks Kaniapiskau Supergroup in the Labrador Trough (including gabbro sills and plutons) in the west and high-grade anorthosite and gneiss in the east. Virtually all of southern Labrador belongs to the major
Grenville Province The Grenville Province is a tectonically complex region, in Eastern Canada, that contains many different aged accreted terranes from various origins. It exists southeast of the Grenville Front and extends from Labrador southwestern to Lake Huron. ...
, which underlies much of eastern Canada and the northern US. Extensive faulting and mylonite marks its northern boundary with the other structural provinces. Archean gneisses were metamorphosed again during the
Grenville orogeny The Grenville orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, ...
and intruded by anorthosite-adamellite plutons. The Kaniapiskau Supergroup extends into the Grenville Province, marked by marble and quartzite. During the
Paleozoic The Paleozoic (or Palaeozoic) Era is the earliest of three geologic eras of the Phanerozoic Eon. The name ''Paleozoic'' ( ;) was coined by the British geologist Adam Sedgwick in 1838 by combining the Greek words ''palaiós'' (, "old") and ' ...
around 334 million years ago, flood basalts emplaced in northern Newfoundland and southern Labrador. Through the
Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles, the Age of Conifers, and colloquially as the Age of the Dinosaurs is the second-to-last era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceo ...
and into the
Cenozoic The Cenozoic ( ; ) is Earth's current geological era, representing the last 66million years of Earth's history. It is characterised by the dominance of mammals, birds and flowering plants, a cooling and drying climate, and the current configura ...
, the landscape eroded, shedding sand into the Labrador Shelf, mainly from older metasediments and metavolcanic rocks that reached
amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose (flaky ...
grade on the sequence of
metamorphic facies A metamorphic facies is a set of mineral assemblages in metamorphic rocks formed under similar pressures and temperatures.Essentials of Geology, 3rd Edition, Stephen Marshak The assemblage is typical of what is formed in conditions corresponding ...
. Close to Makkovik,
breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...
from the Mesozoic, cut by
lamprophyre Lamprophyres () are uncommon, small-volume ultrapotassic igneous rocks primarily occurring as dikes, lopoliths, laccoliths, stocks, and small intrusions. They are alkaline silica-undersaturated mafic or ultramafic rocks with high magnesium oxid ...
-
carbonatite Carbonatite () is a type of intrusive rock, intrusive or extrusive rock, extrusive igneous rock defined by mineralogic composition consisting of greater than 50% carbonate minerals. Carbonatites may be confused with marble and may require geoche ...
dikes marks the opening of the Labrador Sea. The region experienced repeat glaciations during the
Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...
. Glaciomarine silts and mud records the melting of the glaciers on the Labrador Shelf, with significant deposition around 20,000 years ago. Analysis suggests most of these sediments originated on land in Labrador, although large amounts of limestone (which is completely absent in the Labrador) indicate a second source to the north, likely Paleozoic limestone on the Hudson Strait and Ungava Bay.


Natural resource geology of Labrador

Massive iron deposits are found in the Labrador Trough along with copper, uranium and molybdenum. Iron forms in
chert Chert () is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a prec ...
from the Ungava Bay to the Grenville Front, over a span of 700 miles, while copper and nickel minerals such as
pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic Luster (mineralogy), lust ...
,
pyrrhotite Pyrrhotite is an iron sulfide mineral with the formula Fe(1-x)S (x = 0 to 0.2). It is a nonstoichiometric variant of FeS, the mineral known as troilite. Pyrrhotite is also called magnetic pyrite, because the color is similar to pyrite and it is ...
,
sphalerite Sphalerite (sometimes spelled sphaelerite) is a sulfide mineral with the chemical formula . It is the most important ore of zinc. Sphalerite is found in a variety of deposit types, but it is primarily in Sedimentary exhalative deposits, sedimen ...
and
galena Galena, also called lead glance, is the natural mineral form of lead(II) sulfide (PbS). It is the most important ore of lead and an important source of silver. Galena is one of the most abundant and widely distributed sulfide minerals. It cryst ...
form dispersed deposits or massive bodies in Kaniapiskau Supergroup rocks. The Aillik Group hosts uranium as
uraninite Uraninite, formerly pitchblende, is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2 but because of oxidation typically contains variable proportions of U3O8. Radioactive decay of the uranium causes t ...
and
pitchblende Uraninite, formerly pitchblende, is a radioactive, uranium-rich mineral and ore with a chemical composition that is largely UO2 but because of oxidation typically contains variable proportions of U3O8. Radioactive decay of the uranium causes th ...
dispersed in veins in
pegmatite A pegmatite is an igneous rock showing a very coarse texture, with large interlocking crystals usually greater in size than and sometimes greater than . Most pegmatites are composed of quartz, feldspar, and mica, having a similar silicic com ...
, argillite, granulite and quartzite.


References

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