The Flat Landing Brook Formation is a

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics (lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock expo ...

in Gloucester County of northern

New Brunswick New Brunswick is a Provinces and Territories of Canada, province of Canada, bordering Quebec to the north, Nova Scotia to the east, the Gulf of Saint Lawrence to the northeast, the Bay of Fundy to the southeast, and the U.S. state of Maine to ...

, Canada. It consists mostly of

volcanic rock Volcanic rocks (often shortened to volcanics in scientific contexts) are rocks formed from lava erupted from a volcano. Like all rock types, the concept of volcanic rock is artificial, and in nature volcanic rocks grade into hypabyssal and me ...

s that were deposited 466 to 465 million years ago during the

Darriwilian The Darriwilian is the upper stage of the Middle Ordovician. It is preceded by the Dapingian and succeeded by the Upper Ordovician Sandbian Stage. The lower boundary of the Darriwilian is defined as the first appearance of the graptolite species ' ...

stage Stage, stages, or staging may refer to: Arts and media Acting * Stage (theatre), a space for the performance of theatrical productions * Theatre, a branch of the performing arts, often referred to as "the stage" * ''The Stage'', a weekly Brit ...

of the

Middle Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era, and the second of twelve periods of the Phanerozoic Eon. The Ordovician spans 41.6 million years from the end of the Cambrian Period Ma (milli ...

epoch In chronology and periodization, an epoch or reference epoch is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured. The moment of epoch is usually decided b ...

Lithology

Rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...

flows,

breccia Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix. The word has its origins in the Italian language ...

s and hyaloclastics are the primary rocks comprising the Flat Landing Brook Formation. Locally abundant rocks include

tholeiitic 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 ...

to transitional

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...

fragmental rocks and massive flows, as well as

felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...

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 co ...

s, tholeiitic

pillow basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% o ...

s and minor

porphyritic Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning ...

felsic flows.

Siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

greywacke Greywacke or graywacke ( ) is a variety of sandstone generally characterized by its hardness (6–7 on Mohs scale), dark color, and Sorting (sediment), poorly sorted angular grains of quartz, feldspar, and small rock fragments or sand-size Lith ...

, iron formation, ferromanganiferous

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

and

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 ...

represent minor rocks.

Stratigraphy

Relationship to other units

The Flat Landing Brook Formation is the middle member of the Tetagouche Group. Exposures between Route 490 and the headwaters of Flat Landing Brook are the type locality. It is conformably overlain by massive pillowed alkali basalt of the Little River Formation and conformably underlain by crystal tuff as well as

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

feldspar Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...

augen Augen (from German "eyes") are large, lenticular eye-shaped mineral grains or mineral aggregates visible in some foliated metamorphic rocks. In cross section they have the shape of an eye. Feldspar, quartz, and garnet are common minerals which ...

schist Schist ( ) is a medium-grained metamorphic rock generally derived from fine-grained sedimentary rock, like shale. It shows pronounced ''schistosity'' (named for the rock). This means that the rock is composed of mineral grains easily seen with a l ...

of the Nepisiguit Falls Formation. The contact of the Flat Landing Brook and Little River formations is exposed in the Brunswick Mines area and near California Lake whereas the contact of the Flat Landing Brook and Nepisiguit Falls formations is exposed along The Narrows of the

Nepisiguit River The Nepisiguit River is a major river in northern New Brunswick, Canada, which enters the sea at the city of Bathurst, into the Nepisiguit Bay, part of the Bay of Chaleur. Appears in Jesuit Relations (1643) as Nepegiguit, a corruption through t ...

Subdivisions

The Flat Landing Brook Formation contains four named subdivisions:

Volcanology

With an estimated original volume of approximately , the Flat Landing Brook Formation incorporates the eruptive products of a

supervolcano A supervolcano is a volcano that has had an eruption with a volcanic explosivity index (VEI) of 8, the largest recorded value on the index. This means the volume of deposits for such an eruption is greater than . Supervolcanoes occur whe ...

similar in size and eruption rates to the

Taupō Taupō (), sometimes written Taupo, is a town located in the central North Island of New Zealand. It is situated on the edge of Lake Taupō, which is the largest freshwater lake in New Zealand. Taupō was constituted as a borough in 1953. It h ...

and

Yellowstone Yellowstone National Park is a List of national parks of the United States, national park of the United States located in the northwest corner of Wyoming, with small portions extending into Montana and Idaho. It was established by the 42nd U ...

calderas. It may also represent the largest supervolcanic eruption of the

Paleozoic The Paleozoic ( , , ; or Palaeozoic) Era is the first of three Era (geology), geological eras of the Phanerozoic Eon. Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma a ...

era An era is a span of time. Era or ERA may also refer to: * Era (geology), a subdivision of geologic time * Calendar era Education * Academy of European Law (German: '), an international law school * ERA School, in Melbourne, Australia * E ...

. Most of the volcanic rocks were laid down during a timespan of possibly less than two million years. A region of coarse co- ignimbritic breccias in the Flat Landing Brook Formation (Grants Lake pyroclastics) is interpreted to represent the infill of a large

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

with a radius of about .The petrological variations of the Ordovician felsic volcanic rocks of the Tetagouche Group, New Brunswick
/ref> The only rocks that do not seem to be related to the caldera are scattered

dikes Dyke or dike may refer to: General uses * Dyke (slang), a slang word meaning "lesbian" * Dike (geology), formations of magma or sediment that cut through and across the layering of adjacent rocks * Dike (mythology), ''Dikē'', the Greek goddess ...

and small effusive flows of the Taylor Brook rhyolites, the latter of which probably issued from parasitic vents on the outer margins of the caldera.

References

{{coord missing, New Brunswick Geologic formations of New Brunswick Calderas of New Brunswick Supervolcanoes Ordovician calderas Tuff formations of Canada Basalt formations Rhyolite formations Shale formations of Canada Siltstone formations of Canada