Bertie Formation
{{Short description|Geological formation in Ontario, Canada}}
{{Infobox rockunit
| name = Bertie Formation
| image =
| caption =
| type = Geological group
| period = Pridoli
| age = Pridoli (Cayugan Series)
~{{fossil range|422.9|416.0}}
| prilithology = Dolomite, Shale
| otherlithology = Shale
| namedfor = Bertie, Ontario
| namedby = Chapman
| year_ts = 1864
| country = Canada, United States
| coordinates = {{coord|42.9|N|78.9|W|display=inline,title}}
| paleocoordinates = {{coord|30.3|S|40.8|W|display=inline}}
| unitof = Cayugan Series
| subunits = Falkirk (dolomite), Scajaquada (shale) and Williamsville (dolomite) - Western New York
Fiddlers Green (dolomite), Forge Hollow (shale) and Oxbow (dolomite) - Central New York
| underlies = Bois Blanc Formation, Hederberg Group , Bass Islands Group
| overlies = Salina Group
| thickness = Up to {{convert|495|ft|m|abbr=on}}
| extent = Appalachian Basin
| area =
| map = {{Location map+ | United States#New York
| relief = 1
| width = 250
| float = center
| places =
{{Location map~ | United States#New York
| lat_deg = 43.0
| lon_deg = -75.4
| mark = SpringGreen pog.svg
| marksize = 8
}}
{{Location map~ | United States#New York
| lat_deg = 43.0
| lon_deg = -76.0
| mark = SpringGreen pog.svg
| marksize = 8
}}
{{Location map~ | United States#New York
| lat_deg = 43.0
| lon_deg = -75.1
| mark = SpringGreen pog.svg
| marksize = 8
}}
{{Location map~ | United States#New York
| lat_deg = 43.0
| lon_deg = -78.7
| mark = SpringGreen pog.svg
| marksize = 8
}}
{{Location map~ | United States#New York
| lat_deg = 42.9
| lon_deg = -78.8
| mark = SpringGreen pog.svg
| marksize = 8
}}
{{Location map~ | United States#New York
| lat_deg = 42.9
| lon_deg = -78.9
| mark = SpringGreen pog.svg
| marksize = 8
}}
{{Location map~ | United States#New York
| lat_deg = 42.9
| lon_deg = -75.1
| mark = SpringGreen pog.svg
| marksize = 8
}}
{{Location map~ | United States#New York
| lat_deg = 43.5
| lon_deg = -75.0
| mark = SpringGreen pog.svg
| marksize = 8
}}
{{Location map~ | United States#New York
| lat_deg = 43.0
| lon_deg = -78.1
| mark = SpringGreen pog.svg
| marksize = 8
}}
{{Location map~ | United States#New York
| lat_deg = 43.1
| lon_deg = -76.2
| mark = SpringGreen pog.svg
| marksize = 8
}}
{{Location map~ | United States#New York
| lat_deg = 42.9
| lon_deg = -78.9
| mark = SpringGreen pog.svg
| marksize = 12
}}
}}
| map_caption =
}}
The Bertie Group or Bertie Limestone, also referred to as the Bertie Dolomite and the Bertie Formation, is an upper Silurian (Pridoli, or Cayugan) geologic group and Lagerstätte in southern Ontario, Canada, and western New York State, United States. Details of the type locality and of stratigraphic nomenclature for this unit as used by the U.S. Geological Survey are available on-line at the National Geologic Map Database.{{Cite web|url=https://ngmdb.usgs.gov/Geolex/search|title=National Geologic Map Database}} The formation comprises dolomites, limestones and shales and reaches a thickness of {{convert|495|ft|m}} in the subsurface, while in outcrop the group can be {{convert|60|ft|m}} thick.
The group represents the uppermost unit of the Cayugan Series and the youngest Silurian unit in Ontario. The group overlies the Salina Group and is conformably overlain by the Devonian Bois Blanc Formation in Ontario and Onondaga Limestone in New York.
Two formations within the Bertie Group, the Fiddler's Green and Williamsville, are considered Konservat-Lagerstätten; geologic units that contain a unique and typically soft-bodied fauna. These formations have produced thousands of Silurian eurypterids (sea scorpions) as well as early scorpion Proscorpius osborni, xiphosurans, primitive fossil flora, the planktonic cephalodiscid Rotaciurca superbus and the fish Nerepisacanthus denisoni. The excellent preservation of the many eurypterids and other taxa was the possibly result of periodic hypersaline and anoxic conditions owing to the group's position within a shallow inland sea (the Appalachian basin).
Description
The type locality for the Bertie Group is Ridgemount Quarry,[https://paleobiodb.org/classic/displayCollResults?collection_no=53825 Ridgemount Quarry South] at Fossilworks.org located west of Fort Erie on the Niagara Peninsula of Bertie, Ontario, {{convert|6|mi|km}} west of Buffalo, New York, after which the group is named.Sun et al., 2014, p.7 The first author who recognized the group as a separate stratigraphic unit was Chapman in 1884.Vrazo et al., 2017, p.5 In more recent years, the unit has been elevated to group status.Vrazo et al., 2014, p.431Edwards et al., 2004, p.399
Geographic extent
The Bertie Group forms the bedrock in a narrow band extending from Fort Erie, west of Buffalo, New York, through Hagersville, New Hamburg, Harriston, and Walkerton to Southampton on Lake Huron.Hewitt, 1972, p.19 The group consists of medium- to massive-bedded aphanitic brown to grey, laminated, bituminous and burrowed dolomites,Armstrong & Dodge, 2007, p.8 with minor thin-bedded shaly dolomites.Hewitt, 1972, p.10
Along the outcrop area between Fort Erie and Hagersville, the thickness varies from {{convert|35|to|60|ft|m}}. It thickens to {{convert|495|ft|m}} in the subsurface. Sanford (1969) used the term Bertie Group from Fort Erie to the vicinity of Hagersville and the term Bass Islands Formation north and west of Hagersville. The group is correlated with the Bass Islands Formation of Michigan. Bertie Group dolomite is quarried for crushed stone at Fort Erie, Port Colborne, Dunnville, Cayuga, and Hagersville.
Stratigraphy
The Bertie Group is the uppermost unit in the Cayugan Series and forms part of the Tippecanoe II sequence.Swezey, 2002 At its type locality, the group is subdivided into several formations. In central New York, the Group is subdivided into the Fiddlers Green Dolomite, Forge Hollow Shale, and Oxbow Dolomite members, from oldest to youngest. Here, the Bertie Group is overlain by the Honeoye and Chrysler formations. In New York, the Onondaga Limestone overlies the Bertie Group.Rickard, 1969, p.4 The group is in Ontario conformably overlain by the Middle Devonian Bois Blanc Formation.Hewitt, 1972, p.11
Laterally, the group is equivalent to the Bass Islands Formation and is mapped as a combined stratigraphic unit. Haynes and Parkins (1992) reported that the
Bertie Group is progressively cut by the Bass Islands Formation from Dunnville to Hagersville. In Pennsylvania, the Bertie Group is time-equivalent with the Keyser Formation.Rickard, 1969, p.5
Fossils
The Bertie Group Fiddler's Green and Williamsville formations are considered Konservat-Lagerstätten; units characterized by rare and typically soft-bodied fauna. These formations have produced thousands of fossil eurypterids (sea scorpions) since collecting began in earnest in the mid-20th century.Lau, 2009, p.10Vrazo et al., 2016, p.53 Other fossils from the unit include early scorpion Proscorpius osborni, early flora, and a fossil fish; Nerepisacanthus denisoni. The excellent preservation of the many eurypterids possibly was the result of periodic hypersaline and anoxic conditions.Vrazo et al., 2016, p.58
Age
The Bertie Formation is late Silurian (Pridoli, or Cayugan in the local chronologies).
Interpretations of depositional environments
{{see also|Geology of the Appalachians}}
The Appalachian Foreland basin was formed during the Alleghanian orogeny in the Early to Middle Ordovician. The period of mountain building led to the closure of the Iapetus and Rheic Oceans. Due to tectonic loading, the foreland basin developed in the present-day area north of the Appalachian Mountains.Ettensohn, 2008, p.107 The late Silurian climate was arid and warm; this, and the restricted and shallow nature of the inland basin, resulted in the deposition of evaporites in the Salina Group, ranging in thickness from {{convert|120|to|800|m|ft}}.Vrazo et al., 2016, p.49 Zones of stromatolites and thrombolites (non-laminated algal
mounds) occur in several formations in the Bertie Group,Brett et al., 1999, p.10 along with numerous desiccation cracks. During the Hercynian orogeny in the Devonian, many of the Silurian sediments were eroded to the south in the Appalachians, while north of the mountains the Silurian units were preserved.Ettensohn, 2008, p.136
The sediments of the Bertie Group were deposited on the paleosouthern side of the subsiding Algonquin Arch, flanking the northern rim of the Appalachian foreland basin of Laurentia.Burrow & Rudkin, 2014, p.1Lau, 2009, p.24
The Bertie Group was deposited in a hypersaline marine environment. The stratigraphic sections and the fossil content suggest that the group was deposited in a near-shore marine to lagoonal setting, and the evaporites and casts of halite pseudomorphs, with sides of up to {{convert|30|cm|in}}, suggest the environment was far from normal marine; hypersalinity must have prevailed throughout most of the depositional history of the group.[https://paleobiodb.org/classic/displayCollResults?collection_no=153533 Forge Hollow, Waterville] at Fossilworks.org Alternating hypersaline and brackish estuarine conditions have been recorded in the group. The dolomitization of the group most probably was not primary.Vrazo et al., 2016, p.56
See also
{{div col}}
- List of fossiliferous stratigraphic units in New York
- List of fossiliferous stratigraphic units in Ontario
- Tonoloway Formation, contemporaneous formation of Pennsylvania, Maryland, Virginia and West Virginia
- Tymochtee Dolomite, contemporaneous dolomite formation of Ohio
- Catavi Formation, contemporaneous fossiliferous formation of Bolivia
- Peel Sound Formation, contemporaneous fossiliferous formation of Nunavut, Canada
- Stony Mountain Formation, Late Ordovician Lagerstätte of Manitoba, Canada
- Lau event, Late Silurian extinction event preceding the Bertie fauna
{{div col end}}
References
{{reflist|20em}}
= Bibliography =
- {{citation |last1=Armstrong |first1=Derek K. |last2=Dodge |first2=J.E.P. |year=2007 |title=Paleozoic Geology of Southern Ontario |url=https://maps.niagararegion.ca/metadata/md/DocumentUpload/2007-08-08%2014-44-38.pdf |publisher=Ontario Geological Survey |pages=1–27 |accessdate=2019-03-23}}
- {{citation |last1=Brett |first1=Carlton E. |last2=Goodman |first2=William M. |last3=Loduca |first3=Steven T. |last4=Tetreaul |first4=Denis |year=1999 |title=Silurian-Early Devonian sequence stratigraphy, events, and paleoenvironments of western New York and Ontario, Canada |url=https://ottohmuller.com/nysga2ge/Files/1999/NYSGA%201999%20SatB1%20-%20Silurian-Early%20Devonian%20Sequence%20Stratigraphy,%20Events,%20and%20Paleoenvironments%20of%20Western%20New%20York%20and%20Ontario,%20Canada.pdf |publisher=NYSGA |pages=1–58 |accessdate=2019-03-23}}
- {{citation |last1=Burrow |first1=Carole J. |last2=Rudkin |first2=David |year=2014 |title=Oldest Near-Complete Acanthodian: The First Vertebrate from the Silurian Bertie Formation Konservat-Lagersta¨tte, Ontario |journal=PLoS ONE |volume=9 |issue=8 |pages=1–7 |doi=10.1371/journal.pone.0104171 |doi-access=free |pmid=25093877 |pmc=4122448 |bibcode=2014PLoSO...9j4171B }}
- {{citation |last1=Edwards |first1=D. |last2=Banks |first2=H.P. |last3=Ciurca |first3=S.J. |last4=Laub |first4=R.S. |year=2004 |title=New Silurian cooksonias from dolostones of north-eastern North America |journal=Botanical Journal of the Linnean Society |volume=146 |issue=4 |pages=399–413|doi=10.1111/j.1095-8339.2004.00332.x }}
- {{citation |last=Ettensohn |first=Frank R |year=2008 |title=The Appalachian Foreland Basin in Eastern United States |url=https://www.researchgate.net/publication/251471668 |journal=K.J. Hsü: Sedimentary Basins of the World, Vol 5, the Sedimentary Basins of the United States and Canada |volume=5 |pages=105–179 |doi=10.1016/S1874-5997(08)00004-X |accessdate=2019-03-23}}
- {{citation |last=Hewitt |first=D.H |year=1972 |title=Paleozoic Geology of Southern Ontario |url=http://www.geologyontario.mndm.gov.on.ca/mndmfiles/pub/data/imaging/R105/r105.pdf |publisher=Ontario Division of Mines |pages=1–19 |accessdate=2019-03-23}}
- {{citation |last=Lau |first=Kimberly |year=2009 |title=Paleoecology and Paleobiogeography of the New York Appalachian Basin Eurypterids (BSc. thesis) |url=https://pdfs.semanticscholar.org/952c/4f88818ca2c57e2e7b128c9c8ffbb1c8871b.pdf |archive-url=https://web.archive.org/web/20180228161507/https://pdfs.semanticscholar.org/952c/4f88818ca2c57e2e7b128c9c8ffbb1c8871b.pdf |archive-date=2018-02-28 |publisher=Yale University |pages=1–48 |s2cid=14229267 |accessdate=2019-03-23 }} {{Webarchive|url=https://web.archive.org/web/20180228161507/https://pdfs.semanticscholar.org/952c/4f88818ca2c57e2e7b128c9c8ffbb1c8871b.pdf |date=2018-02-28 }}
- {{citation |last=Rickard |first=Lawrence V |year=1969 |title=Stratigraphy of the Upper Silurian Salina Group New York, Pennsylvania, Ohio, Ontario |url=http://nysl.cloudapp.net/data/Library1/Library1/pdf/149934.pdf |publisher=New York State Museum and Science Service |pages=1–77 |accessdate=2019-03-23}}
- {{citation |last1=Sun |first1=S. |last2=Brunton |first2=F.R. |last3=Jin |first3=J. |year=2014 |title=Sequence Stratigraphic Architecture and Bedrock Aquifers of Upper Silurian to Middle Devonian Strata, Southwestern Ontario |url=https://www.researchgate.net/publication/304540332 |publisher=Ontario Geological Survey, Open File Report 6300 |pages=1–15 |accessdate=2019-03-23}}
- {{citation |last=Swezey |first=Christopher S |year=2002 |title=Regional Stratigraphy and Petroleum Systems of the Appalachian Basin, North America |url=https://pubs.usgs.gov/imap/i-2768/i2768.pdf |publisher=USGS |pages=1 |accessdate=2019-03-23}}
- {{citation |last=Treesh |first=Michael |year=1972 |title=Sedimentology and Stratigraphy of the Salina Group (upper Silurian) in East-central New York |url=https://ottohmuller.com/nysga2ge/Files/1972/NYSGA%201972%20B%20-%20Sedimentology%20and%20Stratigraphy%20of%20the%20Salina%20Group%20(upper%20Silurian)%20in%20East-central%20New%20York.pdf |publisher=Rensselaer Polytechnic Institute |pages=1–26 |accessdate=2019-03-23}}
- {{citation |last1=Vrazo |first1=Matthew B. |last2=Brett |first2=Carlton E. |last3=Ciurca Jr |first3=Samuel J. |year=2016 |title=Buried or brined? Eurypterids and evaporites in the Silurian Appalachian basin |url=https://mattvrazo.files.wordpress.com/2017/03/vrazo_et-al_2016_buried-or-brined.pdf |journal=Palaeogeography, Palaeoclimatology, Palaeoecology |volume=444 |pages=48–59 |doi=10.1016/j.palaeo.2015.12.011 |bibcode=2016PPP...444...48V |accessdate=2019-03-23}}
- {{citation |last1=Vrazo |first1=Matthew B. |last2=Trop |first2=Jeffrey M. |last3=Brett |first3=Carlton E. |year=2014 |title=A new eurypterid Lagerstätte from the Upper Silurian of Pennsylvania |url=http://pdfs.semanticscholar.org/fd4d/9709eb439950cb42bd1e7e1f661164e4cf67.pdf |archive-url=https://web.archive.org/web/20190309025151/http://pdfs.semanticscholar.org/fd4d/9709eb439950cb42bd1e7e1f661164e4cf67.pdf |archive-date=2019-03-09 |journal=PALAIOS |volume=29 |issue=8 |pages=431–448 |doi=10.2110/palo.2014.003 |bibcode=2014Palai..29..431V |s2cid=30066085 |accessdate=2019-03-23}}
External links
- [https://en.wikisource.org/wiki/The_Eurypterida_of_New_York/Volume_1 The Eurypterida of New York/Volume 1]
- [https://en.wikisource.org/wiki/The_Eurypterida_of_New_York/Volume_2 The Eurypterida of New York/Volume 2]
{{Chronostratigraphy of Michigan}}
{{Chronostratigraphy of New York}}
{{Chronostratigraphy of Ohio}}
{{Chronostratigraphy of Pennsylvania}}
{{Stratigraphic column of West Virginia}}
Category:Geologic formations of New York (state)
Category:Geologic formations of Ontario
Category:Silurian System of North America
Category:Silurian United States
Category:Shallow marine deposits
Category:Fossiliferous stratigraphic units of North America
Category:Paleontology in New York (state)