Woodbend Group#Subdivisions

{{Infobox Rockunit

| name = Woodbend Group

| image =

| caption =

| type = Geological group

| age = {{Fossil range|Frasnian|Frasnian|Frasnian}}

| period = Frasnian

| prilithology = Limestone, dolomite

| otherlithology = Shale

| namedfor =

| namedby = Imperial Oil

| year_ts = 1950

| region = Alberta, British Columbia, Manitoba, Northwest Territories, Saskatchewan, Yukon

| country = Canada

| coordinates = {{coord|53.34507|N|113.6949|W|display=inline,title|name=Woodbend Group}}

| unitof =

| subunits = Cooking Lake Formation
Duvernay Formation
Leduc Formation
Ireton Formation

| underlies = Winterburn Group

| overlies = Beaverhill Lake Group

| thickness = up to {{convert|700|m|ft|-1}}

| extent =

| area =

| map =

| map_caption =

}}

The Woodbend Group is a stratigraphic unit of Frasnian age in the Western Canadian Sedimentary Basin.

It was first described in the British American Pyrcz No. 1 well by Imperial Oil geological staff in 1950.Imperial Oil Limited, Geological Staff, Western Division, 1950. Devonian nomenclature in Edmonton area, Alberta, Canada. Bull. American Association of Petroleum Geologists, v. 34, p. 1807-1825

Lithology

The Formation is composed of crystalline and dolomitized limestone (Cooking Lake Formation) in off-reef areas, bituminous shale and argillaceous limestone, detrital limestone (reef fallout), stromatoporoid calcarenite (Duvernay Formation), gray shale, argillaceous limestone, argillaceous dolomite, crystalline dolomite (Ireton Formation). In reef build-ups, it consists of massive limestone and dolomite with porosity (Leduc Formation).

{{Cite web|url=http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:016672

|title=Woodbend Group

|author=Lexicon of Canadian Geologic Units

|access-date=2009-03-01}}

=Hydrocarbon production=

Oil is produced from the Leduc Formation in central Alberta since the early 1950s. Shale gas and liquids are extracted from the Duvernay Formation using horizontal drilling and multi-stage hydraulic fracturing.{{Cite web|url=http://chinookconsulting.ca/News/Duvernay-Shale.html|title=The Duvernay Shale|access-date=2012-03-04}} Several project test the economic viability of extracting bitumen from the Grosmont Formation.

Distribution

The Woodbend Group reaches a maximum thickness of {{convert|700|m|ft|-1}} in northern Alberta (where reefs were developed), and has typical thickness of {{convert|300|m|ft|-1}} in southern and central Alberta. It extends laterally from north-eastern British Columbia through Alberta and into southern Saskatchewan and southern Manitoba. Reef build-ups range in size from small mounds to pinnacle reefs and large atoll size reefs and bank developments.

Subdivisions

;Central Alberta

In central Alberta the following formations are recognized, from top to bottom:

Sub-unit	Age	Lithology	Max. Thickness
class="wikitable"
Ireton Formation	Frasnian	upper: calcareous shale and argillaceous limestone middle: fissile grey-green shale with calcirudite beds lower: massive and banded limestone with shale partings	{{convert\|250\|m\|ft
1\|abbr=on}} \|{{Cite web\|url=http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:007011\|title=Ireton Formation\|author=Lexicon of Canadian Geologic Units \|access-date=2009-12-27}}
Leduc Formation	Frasnian	shallow water reef deposits: Stromatoporoid limestone, skeletal mudstone, boundstone, floatstone, packstone and wackestone, mostly dolomitized	{{convert\|300\|m\|ft
1\|abbr=on}} \|{{Cite web\|url=http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:008349\|title=Leduc Formation\|author=Lexicon of Canadian Geologic Units \|access-date=2009-12-27}}
Duvernay Formation	Frasnian	bituminous shale, calcareous shale, argillaceous limestone with disseminated pyrite	{{convert\|250\|m\|ft
1\|abbr=on}} \|{{Cite web\|url=http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:004342\|title=Duvernay Formation\|author=Lexicon of Canadian Geologic Units \|access-date=2009-12-27}}
Cooking Lake Formation	Frasnian	limestone (dolomite in the Rimbey-Meadowbrook reef trend)	{{convert\|90\|m\|ft
1\|abbr=on}} \|{{Cite web\|url=http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:003304\|title=Cooking Lake Formation\|author=Lexicon of Canadian Geologic Units \|access-date=2009-12-27}}

;Northeast Alberta

In northeast Alberta the following formations are recognized, from top to bottom:

Sub-unit	Age	Lithology	Max. Thickness
class="wikitable"
Grosmont Formation	Frasnian	limestone and dolomite, minor argillaceous dolomite, limestone, siltstone and shale	{{convert\|230\|m\|ft
1\|abbr=on}} \|{{Cite web\|url=http://cgkn1.cgkn.net/weblex/weblex_litho_detail_e.pl?00053:006008\|title=Grosmont Formation\|author=Lexicon of Canadian Geologic Units \|access-date=2011-06-25}}
Ireton Formation	Frasnian	upper: calcareous shale and argillaceous limestone middle: fissile grey-green shale with calcirudite beds lower: massive and banded limestone with shale partings	{{convert\|250\|m\|ft
1\|abbr=on}} \|
Cooking Lake Formation	Frasnian	limestone: fossiliferous mudstone and wackestone, grainstone, stromatoporoid rudstone and floatstone	{{convert\|90\|m\|ft
1\|abbr=on}} \|

Relationship to other units

The Woodbend Group is conformably overlain by the Winterburn Group and conformably overlays the Beaverhill Lake Group. It is transgressive in the Peace River Arch and Tathlina uplift. Newer deposits rest on the Woodbend group upon an erosional surface in eastern Alberta, south-central Saskatchewan and Manitoba.

It is equivalent to the Birdbear Formation and Duperow Formation in northern Montana, southern Saskatchewan and southwestern Manitoba, as well as parts of the Fort Simpson Formation and Muskwa Formation of northeastern British Columbia and southern Yukon, while it corresponds to the Tathlina Formation, Twin Falls Formation and Hay River Formation in the Northwest Territories.