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21-584: The formations of the Elk Point Group are composed primarily of carbonate rocks ( dolomite and limestone ) and evaporitic rocks ( halite , anhydrite and potash ), with lesser amounts of dolomitic mudstone and shale . Some of the carbonate formations of the Elk Point Group contain rich assemblages of marine invertebrate fossils , including many species of brachiopods , gastropods , bivalves , cephalopods , crinoids , ostracods and corals . The evaporitic formations are unfossiliferous or contain

42-525: A well that was drilled near Elk Point has been designated as the type section (Anglo-Canadian Elk Point No. 11, 2-11-57-5W4). The group is subdivided into the Lower and Upper Elk Point Group, each of which is further subdivided into formations according to the dominant lithologies , as shown in the tables below. The Lower Elk Point Group comprises all strata lying below the Winnipegosis Formation (in

63-700: A few spores and algal remains. The formations of the Elk Point Group were deposited in a marine embayment that stretched from an open ocean in the present-day Northwest Territories of Canada to North Dakota in the United States, covering an area roughly half as large as that covered by today's Mediterranean Sea . At times of low water levels and excessive evaporation , halite and other evaporite minerals were deposited in sabkha , supratidal flat and coastal lagoon environments, and at times of higher water levels carbonate platform sedimentation and reef growth were dominant. The Elk Point Group extends from

84-723: Is composed of dolomite (CaMg(CO 3 ) 2 ). They are usually classified on the basis of texture and grain size . Importantly, carbonate rocks can exist as metamorphic and igneous rocks, too. When recrystallized carbonate rocks are metamorphosed , marble is created. Rare igneous carbonate rocks even exist as intrusive carbonatites and, even rarer, there exists volcanic carbonate lava . Carbonate rocks are also crucial components to understanding geologic history due to processes such as diagenesis in which carbonates undergo compositional changes based on kinetic effects . The correlation between this compositional change and temperature can be exploited to reconstruct past climate as

105-402: Is doloimite which contains significant trace levels of iron. Due to the similar ionic radii of iron(II) and magnesium , iron(II) can easily substitute magnesium to form ferroan dolomite; manganese can also substitute this atom. The result can be defined as ankerite . The exact delineation between which minerals are considered ferroan dolomite and which are ankerite is unclear. Ankerite with

126-433: Is dolomite which has more calcium than magnesium in its mineral form. This is the most common form of dolomite found naturally and artificially from synthesis . This dolomite, when formed in the oceans, can prove to be metastable . The resultant structure of this mineral presents minimal differences from regular dolomite likely as a result of formation after initial crystal growth. Iron-rich dolomite, or ferroan dolomite,

147-465: Is done in paleoclimatology . Carbonate rocks can also be used for understanding various other systems as described below. Limestone is the most common carbonate rock and is a sedimentary rock made of calcium carbonate with two main polymorphs : calcite and aragonite. While the chemical composition of these two minerals is the same, their physical properties differ significantly due to their different crystalline form . The most common form found in

168-634: Is equivalent to parts of the Horn River Formation , Besa River Formation , and others. The porous carbonate rocks of the Elk Point Group host major petroleum and natural gas reservoirs . As of 1994, the Initial Established Recoverable Petroleum Reserves and the Cumulative Petroleum Production for the group were estimated at 339.3 and 240.4 million cubic metres, respectively. For natural gas,

189-705: The Northwest Territories, some of its uppermost units are exposed at surface or are unconformably overlain by Cretaceous strata. The Lower Elk Point Group is equivalent to the Stone Formation and its equivalents, and the Headless and Nahanni Formations , in northerneastern British Columbia and the southwestern Northwest Territories. In the same areas, the Upper Elk Point includes the Pine Point Group , and

210-544: The greenhouse effect . There is significant amount of research studying the ideal quantity of calcium carbonate (derived from limestone) in concrete and if other compounds can be used to provide the same economic and structural integrity benefits. Many forms of paleoclimatology exist whereby carbonate rocks can be used to determine past climate. Corals and sediments are well-known proxies for these reconstructions. Corals are marine organisms with calcium carbonate skeletons (rocks) which grow specific to oceanic conditions at

231-503: The "pure" CaFe(CO 3 ) 2 chemical formula has yet to be found in nature . Carbonate rocks are significant for both human understanding of Earth's atmospheric and geologic history, in addition to providing humans with significant resources for current civilizational endeavors such as concrete . Limestone is often used in concrete as powder due to its cheap cost. During the formation of concrete, however, breakdown of limestone releases carbon dioxide and contributes significantly to

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252-588: The Initial Established Marketable Reserves and the Cumulative Production were estimated at 142.7 and 79.5 billion cubic metres, respectively. Carbonate rock Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals . The two major types are limestone , which is composed of calcite or aragonite (different crystal forms of CaCO 3 ), and dolomite rock (also known as dolostone), which

273-469: The aragonite of coral skeleton can be used, alongside other proxies like oxygen isotopic ratios , to reconstruct climate variability when the coral was growing. This is because Strontium will sometimes substitute for Calcium in the calcium carbonate molecule depending on temperature effects. Similar to the concept for using compositional changes in coral skeletons as proxies for climate conditions, compositional changes in marine sediments can be used for

294-529: The existing rock grains together or it can fill fractures. Compared to calcite, aragonite is less stable and more soluble , and can thus be converted to calcite under certain conditions. In solution, magnesium ions can act as promoters of aragonite growth as they inhibit calcite precipitation . Often this inhibited precipitation occurs in biology where organisms aim to precipitate calcium carbonate for their structural features such as for skeleton and shells . The discovery of dolomite rock, or dolostone ,

315-783: The following subdivisions, from top to base: The Elk Point Group is dolomitic and is not differentiated. The Elk Point Group is conformably overlain by the Manitoba Group in Manitoba and Saskatchewan, and by the Beaverhill Lake Group in Alberta. It rests unconformably on Precambrian basement rocks in northern Alberta, on Cambrian strata in northeastern Alberta and in Saskatchewan, and on Ordovician to Silurian formations in western Alberta, Saskatchewan and southwestern Manitoba. In

336-520: The same purpose (and more). The changes in trace metal ratios from carbonate minerals found here can be used to determine patterns from parent [carbonate] rocks, too. Headless Formation The Headless Formation is a geologic formation in Northwest Territories . It preserves fossils dating back to the Devonian period . This article about a specific stratigraphic formation in Canada

357-512: The seafloor is calcite, while aragonite is more found in biological organisms. Calcite can be either dissolved by groundwater or precipitated by groundwater, depending on several factors including the water temperature , pH , and dissolved ion concentrations. Calcite exhibits an unusual characteristic called retrograde solubility in which it becomes less soluble in water as the temperature increases. When conditions are right for precipitation, calcite forms mineral coatings that cement

378-467: The south) or the Keg River Formation (in the north) and is present only in the deepest parts of the basin . The Upper Elk Point Group, which is present throughout the basin, includes those formations and all overlying formations to the base of the Manitoba Group (in the south) or the Beaverhill Lake Group (in the north). In northern Alberta and central Alberta , the Elk Point Group contains

399-430: The southern boundary of the Northwest Territories through northwestern British Columbia , Alberta , Saskatchewan , and southwestern Manitoba in Canada, and continues into eastern Montana and North Dakota in the United States. It reaches a maximum thickness of about 610 metres (2,000 ft) in eastern Alberta. The Elk Point Group was named for the town of Elk Point, Alberta by J.R. McGehee in 1949. Core from

420-404: The time of growth. Diagenesis refers to the process whereby sediments are being converted to sedimentary rock. This includes biological activity, erosion, and other chemical reactions. Due to the strong correlation between diagenesis and seawater temperature , coral skeletons can be used as proxies for understanding past climate effects. Specifically, the ratio of Strontium to Calcium in

441-524: Was first published in 1791 and has been found across the Earth's crust from various different time periods . Because the rock is made of calcium , magnesium , and carbonate ions, the mineral crystalline structure can be visualized similar to calcite and magnesite . Due to this composition, the dolomite mineral present in dolostone can be classified by varying degree of calcium inclusion, and occasionally iron, too. Calcium-rich dolomite, or calcian dolomite,

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