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{{Infobox Rockunit
| name = Leduc Formation
| image =
| caption =
| type = [[Geological formation]]
| age = [[Frasnian]]<br>~{{Fossil range|382|373}}
| period = Frasnian
| prilithology = [[Dolomite (rock)|Dolomite]]
| otherlithology = [[Limestone]]
| namedfor = City of [[Leduc, Alberta]]
| namedby = [[Imperial Oil Limited]]
| year_ts = 1950<ref name=Imperial>{{cite journal|author=Geological Staff, Imperial Oil Limited, Western Division |date=September 1950 |title=Devonian Nomenclature in Edmonton Area, Alberta, Canada |journal=Bulletin of the American Association of Petroleum Geologists |volume=34 |number=9 |pages=1807–1825 |doi=10.1306/3D934037-16B1-11D7-8645000102C1865D}}</ref>
| region = [[Alberta]]
| country = [[Canada]]
| coordinates = {{coord|53.3451|N|113.6949|W|name=B.A. Pyrz No. 1 well/Leduc Formation|display=inline,title}}
| paleocoordinates = {{coord|12.4|S|41.2|W|display=inline}}
| unitof =
| subunits = Cooking Lake Member
| underlies = [[Duvernay Formation|Duvernay]] & [[Ireton Formation]]s
| overlies = [[Beaverhill Lake Formation]]
| thickness = up to {{convert|300|m|ft|-1|abbr=on}}<ref name=lexicon>{{Cite web|url=http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:008349 |archive-url=https://archive.today/20120708100103/http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:008349 |url-status=dead |archive-date=July 8, 2012 |title=Leduc Formation |author=Lexicon of Canadian Geological Units |accessdate=2009-02-09}}</ref>
| extent = [[Western Canadian Sedimentary Basin]]
| area =
| map = {{Location map+ | Canada#Alberta
| relief = 1
| width = 250
| float = center
| places =
{{Location map~ | Canada#Alberta
| lat_deg = 53.3451
| lon_deg = -113.6949
| mark = Gold pog.svg
| marksize = 10
}}
}}
| map_caption =
}}
The '''Leduc Formation''' is a [[stratigraphic unit]] of [[Late Devonian]] ([[Frasnian]]) [[Geochronology|age]] in the [[Western Canadian Sedimentary Basin|Western Canada Sedimentary Basin]].<ref name=Mossop12>{{Cite web|url=https://ags.aer.ca/publications/chapter-12-devonian-woodbend-winterburn-strata |title=The Geological Atlas of the Western Canada Sedimentary Basin, Chapter 12: Devonian Woodbend-Winterburn strata of the Western Canada Sedimentary Basin|veditors=Mossop GD, Shetsen I |vauthors=Switzer SB, Holland WG, Christie DS, Graf GC, Hedinger AS, McAuley RJ, Wierzbicki RA, Packard JJ |publisher=Canadian Society of Petroleum Geologists and Alberta Geological Survey |year=1994 |accessdate=13 April 2019 |url-status=live |archiveurl=https://web.archive.org/web/20190326035255/https://ags.aer.ca/publications/chapter-12-devonian-woodbend-winterburn-strata |archivedate=26 March 2019}}</ref> It takes its name from the city of [[Leduc, Alberta|Leduc]], and it was formally described from the B.A. Pyrz No. 1 well in [[central Alberta]], between the depths of {{convert|1,623.7|m|ft|abbr=on}} and {{convert|1,807.5|m|ft|abbr=on}}, by [[Imperial Oil Limited]] in 1950. Supplementary information came from a complete section of the formation that was [[Core_sample|cored]] in Imperial Oil's Leduc No. 530 well between {{convert|1633|m|ft|abbr=on}} and {{convert|1863|m|ft|abbr=on}}.<ref name=lexicon/><ref name=Imperial /><ref name=Glass>Glass, D.J. (editor) 1997. Lexicon of Canadian Stratigraphy, vol. 4, Western Canada including eastern British Columbia, Alberta, Saskatchewan and southern Manitoba. Canadian Society of Petroleum Geologists, Calgary, 1423 p. on CD-ROM. {{ISBN|0-920230-23-7}}.</ref>

The Leduc Formation is a major source of [[Petroleum|oil]] and [[Natural gas|gas]] in central Alberta, and the drilling of the highly successful [[Leduc No. 1]] well in 1947 ushered in a new era in the Western Canadian petroleum industry.<ref name=heritage>{{cite encyclopedia|url=http://www.edukits.ca/petroleum/students_faq.htm |archive-url=http://wayback.archive-it.org/2217/20101208160955/http://www.edukits.ca/petroleum/students_faq.htm |url-status=dead |archive-date=2010-12-08 |title=Frequently Asked Questions – Leduc #1 |encyclopedia=Alberta Online Encyclopedia and Edukits |author=Heritage Community Foundation |access-date=13 April 2019}}</ref>

== Lithology ==
The Leduc Formation consists of fossil [[reefs]] that are highly [[porosity|porous]], which makes them excellent [[petroleum reservoir|reservoirs]] for oil and gas. They were deposited as [[limestone]] and [[mudstone]] in shallow water reef environments. [[Stromatoporoidea|Stromatoporoids]] were the primary reef-building organisms, and rock-types range from skeletal [[mudstone]]s and [[floatstone]]s to finer grained muddy [[packstone]]s and [[wackestone]]s.

Many, but not all, of the reefs were later subjected to [[dolomitization]] during [[diagenesis]], which increased their porosity, and they now consist of [[Dolomite (rock)|dolomite]] rather than limestone.<ref name=Glass /> The dolomitization that took place in the region has increased the porosity primarily in the more deeply buried [[Lagoon|lagoonal]] back reef facies. The pre-existing porosity has also been preserved well due to the dolomitization. Porosity in the region is dominated by [[Vug|vuggy]], moldic, intercrystalline, as well as [[Fracture (geology)|fracture]] types of porosity. Generally, the mean porosity of the Leduc Formation is 5.2%, with the [[Permeability (earth sciences)|permeability]] of the rocks in the region being an even spread.<ref name=":0">{{Cite thesis|url=http://www.collectionscanada.gc.ca/obj/s4/f2/dsk1/tape8/PQDD_0019/MQ55089.pdf |title=Sedimentology, diagenesis and reservoir characteristics of the Devonian Simonette (Leduc Formation) and Ante Creek (Swan Hills Formation) fields: a comparison between a limestone and dolomite field, west-central Alberta Basin |last=Rock |first=Luc |date=June 1999|publisher=McGill University|degree=MS |access-date=13 April 2019 |via=Library and Archives Canada}}</ref>

[[Anhydrite]] is also common in the Leduc Formation, along with the replacement dolomitization.<ref name=":0" />

== Oil and gas production ==
[[File:Leduc oil.jpg|thumb|right|150px|[[Leduc No. 1|The Leduc No. 1 well]]]]
The Leduc Formation is a major source of oil and natural gas in central Alberta. The Leduc No. 1 well drilled in 1947 produced 50 thousand cubic metres (more than 300 thousand barrels) of oil,<ref name=heritage /> marking the beginning of the post-war Albertan oil boom, and contributed to a large population boom in the cities of [[Calgary]] and [[Edmonton]]. <ref>"Woods, Hon. Lt-Col James Hossack, (12 July 1867–20 May 1941), Pres. Calgary Herald", ''Who Was Who'', Oxford University Press, 2007-12-01, retrieved 2019-04-08</ref> The discovery and subsequent production from the wells also led to an economic boom in Alberta, which now puts Calgary among the forefront of producers of oil in North America.{{citation needed|date=April 2019}}

The Strachan and Ricinus West gas fields, discovered in 1967 and 1969, are also in Late [[Devonian]] Leduc-age reefs.<ref name=strachan>{{cite book|last1=Hriskevich |first1=M. E. |last2=Faber |first2=J. M. |last3=Langton |first3=J. R. |year=1980 |chapter=Strachan and Ricinus West Gas Fields, Alberta, Canada |title=Giant Oil and Gas Fields of the Decade: 1968-1978 |series=AAPG Memoir |volume=30 |editor-last=Halbouty |editor-first=M. T. |publisher=American Association of Petroleum Geologists |isbn=0891813063 |chapter-url=https://pubs.geoscienceworld.org/books/book/1433/chapter/107724343/strachan-and-ricinus-west-gas-fields-alberta |access-date=13 April 2019}}</ref> The reefs were found using seismic common-depth point (CDP) techniques, which were being developed and used in the Western Canada Sedimentary Basin. The well that was crucial to the discovery of these two formations was drilled in 1955, and yielded gas as well as some salt water. Reef buildup of the Strachan and Ricinus gas field reefs are {{convert|900|ft}} and {{convert|800|ft}} respectively.<ref name=strachan />

== Distribution and thickness ==
The Leduc Formation occurs as discrete, discontinuous reef "buildups" in a line following the Woodbend shelf margin from [[Drumheller]] in central Alberta to the [[Peace River, Alberta|Peace River]] Arch area in [[northern Alberta]]. The formation is absent in inter-reef areas, and buildups can reach from {{convert|180|m|ft|sp=us}} to {{convert|300|m|ft|sp=us}} in thickness.<ref name=Glass />

== Relationship to other units ==
In central Alberta the Leduc Formation conformably overlies the platform limestones and dolomites of the [[Cooking Lake Formation|Cooking Lake]] and [[Beaverhill Lake Formation]]s. In northern Alberta near the Peace River Arch it rests on older [[red bed]]s or on the [[Granite Wash (geology)|Granite Wash]]. The Leduc reefs are surrounded by [[shales]] of the [[Duvernay Formation|Duvernay]] and [[Ireton Formation]]s and the [[Woodbend Group]] that were deposited in non-reefal, open marine environments.

The Leduc reefs are the same ages as, but not contiguous with, the reefs of the [[Cairn Formation]] farther west. Because the Leduc reefs are not exposed at the surface, the extensive [[outcrop]]s of the Cairn reefs in the [[Canadian Rockies]] have been studied to increase the understanding of the Leduc reefs.<ref name=Bloy>Bloy, G.R., Hunter, I.G. and Leggett, S.R. 1984. Depositional environments of the Devonian Cairn Formation, Rocky Mountain front ranges, Canmore, Alberta. Carbonates in subsurface and outcrop: 1984 CSPG Core Conference, Canadian Society of Petroleum Geologists, p. 148.</ref>

Near the Leduc Formation there is also the [[Beaverhill Lake Group|Swan Hills Formation]]. These two formations hold some similarities, such as the types of rocks and certain diagenetic processes. Rock types in both regions are dominated by limestones and dolomites. Dolomitization has taken place in both formations however it is more dominant in the Leduc Formation. [[Evaporite|Evaporites]] such as Anhydrites are also more present in the Leduc Formation, however they are also present in the Swan Hills Formation.<ref name=":0" />

The Swan Hills Formation also holds some differences to the Leduc Formation. The porosity types in both formations differ, and the types of fossilized biota also differ. Vuggy, moldic, intercrystalline, and fracture porosities are present in the Leduc Formation whereas the primary porosities in the Swan Hills Formation are interparticle and interfossil. One of the primary fossilized biota in the Leduc Formation are [[Stromatoporoidea|stromatoporoids]], whereas the primary fossil type in the Swan Hills Formation are [[Amphipoda|Amphipora]].<ref name=":0" />

== Fossil content ==
The following fossils have been reported from the formation:<ref name=FW>[https://paleobiodb.org/classic/displayStrata?geological_group=&formation=Leduc&group_formation_member=Leduc Leduc Formation] at [[Fossilworks]].org</ref>

;Bivalves
* ''[[Megalodon (bivalve)|Megalodon sp.]]''
* ''[[Modiomorpha|Modiomorpha sp.]]''
* ''[[Turbinopsis|Turbinopsis sp.]]''
;Brachiopods
* ''[[Conocardium|Conocardium sp.]]''
* ''[[Cranaena|Cranaena sp.]]''
* ''[[Schizophoria|Schizophoria sp.]]''
;Gastropods
* ''[[Cypricardinia|Cypricardinia sp.]]''
* ''[[Leptodesma|Leptodesma (Leiopteria) sp.]]''
* [[Archaeogastropoda|Archaeogastropoda indet.]]
;Corals
{{div col|colwidth=29em}}
* ''[[Actinostroma|Actinostroma clathratum]]''
* ''[[Actinostroma|A. redwaterense]]''
* ''[[Anostylostroma|Anostylostroma laxum]]''
* ''[[Atelodictyon|Atelodictyon cf. stelliferum]]''
* ''[[Euryamphipora|Euryamphipora platyformis]]''
* ''[[Ferestromatopora|Ferestromatopora dubia]]''
* ''[[Hammatostroma|Hammatostroma nodosum]]''
* ''[[Macgeea|Macgeea parva]]''
* ''[[Peneckiella|Peneckiella floydensis]]''
* ''[[Stachyodes|Stachyodes costulata]]''
* ''[[Stromatopora|Stromatopora cygnea]]''
* ''[[Stromatoporella|Stromatoporella cf. subvesiculosa]]''
* ''[[Stromatoporella|Stromatoporella damnoniensis]]''
* ''[[Stromatoporella|Stromatoporella cf. mirabilis]]''
* ''[[Synthetostroma|Synthetostroma vesiculosum]]''
* ''[[Trupetostroma|Trupetostroma warreni]]''
* ''[[Trupetostroma|Trupetostroma cf. coalescens]]''
* ''[[Alveolites|Alveolites sp.]]''
* ''[[Amphipora|Amphipora sp.]]''
* ''[[Charactophyllum|Charactophyllum sp.]]''
* ''[[Macgeea|Macgeea sp.]]''
* ''[[Metriophyllum|Metriophyllum sp.]]''
* ''[[Phacellophyllum|Phacellophyllum sp.]]''
* ''[[Phillipsastrea|Phillipsastrea sp.]]''
* ''[[Stachyodes|Stachyodes sp.]]''
* ''[[Syringoporella|Syringoporella sp.]]''
* ''[[Syringopora|Syringopora sp.]]''
* ''[[Tabulophyllum|Tabulophyllum sp.]]''
* ''[[Thamnopora|Thamnopora sp.]]''
* ''[[Zaphrentis|Zaphrentis sp.]]''
* ''[[Trupetostroma|?Trupetostroma sp.]]''
{{div col end}}

== References ==
{{reflist}}

{{Western Canadian Sedimentary Basin|Northwest_Plains=yes|South AB=yes}}

[[Category:Geologic formations of Alberta]]
[[Category:Devonian Alberta]]
[[Category:Frasnian Stage]]
[[Category:Dolomite formations of Canada]]
[[Category:Limestone formations of Canada]]
[[Category:Reef deposits]]
[[Category:Shallow marine deposits]]
[[Category:Reservoir rock formations]]
[[Category:Devonian southern paleotropical deposits]]
[[Category:Western Canadian Sedimentary Basin]]
[[Category:Fossiliferous stratigraphic units of North America]]
[[Category:Paleontology in Alberta]]

Leduc Formation - Revision history

imported>Volcanoguy: ce