Bertie Formation

Bertie Group Stratigraphic range: Pridoli (/) ~422.9–416.0 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological group
Unit of
Sub-units	Akron, Cobleskill, Fiddlers Green, Fort Hill, Moran Corner, Scajaquada, Williamsville, Oatka, Oxbow formations
Underlies	Bois Blanc Formation
Overlies	Salina Group
Thickness	Up to 495 ft (151 m)
Lithology
Primary	Dolomite
Other	Shale
Location
Coordinates	42°54′N 78°54′W / 42.9°N 78.9°W / 42.9; -78.9Coordinates: 42°54′N 78°54′W / 42.9°N 78.9°W / 42.9; -78.9
Approximate paleocoordinates	30°18′S 40°48′W / 30.3°S 40.8°W / -30.3; -40.8
Region	Ontario New York
Country	Canada  United States
Extent	Appalachian Basin
Type section
Named for
Named by	Chapman
Year defined	1864
Bertie Formation (the United States) Bertie Formation (New York) Show map of the United StatesShow map of New YorkShow all

The Bertie Group or Bertie Limestone, also referred to as the Bertie Dolomite and the Bertie Formation, is an upper Silurian (Pridoli, or and age in the local chronologies) 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.^[1] The formation comprises dolomites, limestones and shales and reaches a thickness of 495 feet (151 m) in the subsurface, while in outcrop the group can be 60 feet (18 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 Proscorpius osborni, the oldest known scorpion, xiphosurans, primitive fossil flora, 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 groups position within a shallow inland sea (the Appalachian basin).

Description[]

The type locality for the Bertie Group is Ridgemount Quarry,^[2] located west of Fort Erie on the Niagara Peninsula of Bertie, Ontario, 6 miles (9.7 km) west of Buffalo, New York,^[3] after which the group is named.^[4] The first author who recognized the group as a separate stratigraphic unit was Chapman in 1884.^[3] In more recent years, the unit has been elevated to group status.^[5][6]

Geographic extent[]

The Bertie Group forms the bedrock in a narrow band extending from Fort Erie, west of Buffalo, New York, through , New Hamburg, Harriston, and Walkerton to Southampton on Lake Huron.^[7] The group consists of medium- to massive-bedded aphanitic brown to grey, laminated, bituminous and burrowed dolomites,^[8] with minor thin-bedded shaly dolomites.^[9]

Along the outcrop area between Fort Erie and Hagersville, the thickness varies from 35 to 60 feet (11 to 18 m). It thickens to 495 feet (151 m) in the subsurface. Sanford (1969) used the term Bertie Groupfrom 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 .

Stratigraphy[]

The Bertie Group is the uppermost unit in the Cayugan Series and forms part of the Tippecanoe II sequence.^[10] At its type locality, the group is subdivided into several formations.^[3] In central New York, the Group is subdivided into the Fiddlers Green Dolomite, Forge Hollow Shale, and Oxbow Dolomite members, from oldest to youngest.^[3] Here, the Bertie Group is overlain by the Honeoye and Chrysler formations. In New York, the Onondaga Limestone overlies the Bertie Group.^[11] The group is in Ontario conformably overlain by the Middle Devonian Bois Blanc Formation.^[12]

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.^[8] In Pennsylvania, the Bertie Group is time-equivalent with the Keyser Formation.^[13]

Fossils[]

Many Eurypterus fossils were found in the formation

The fish Nerepisacanthus denisoni is the only vertebrate found in the Bertie Formation

The Bertie Group Fiddler's Green and Williamsville formations are considered Konservat-Lagerstätten;^[14] 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.^[15][16] Other fossils from the unit include Proscorpius osborni, the oldest known scorpion, 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.^[17]

Group	Fossils	Member	Image	Notes
Fish	Nerepisacanthus denisoni	Williamsville		[18]
Eurypterids	Acutiramus macrophthalmus	Fiddlers Green Williamsville		[19][20]
	Buffalopterus pustulosus	Williamsville		[20][21]
	Carcinosoma scorpionis	Oxbow Dolomite		[22]
	Clarkeipterus testudineus	Fiddlers Green		[21][23]
	Dolichopterus herkimerensis	Fiddlers Green		[21][23]
	D. jewetti	Fiddlers Green		[24]
	D. macrocheirus	Williamsville		[20][21]
	D. siluriceps	Fiddlers Green Williamsville		[20][25]
	Erieopterus pustulosus	Fiddlers Green		[25]
	Eurypterus dekayi	Williamsville		[20][26]
	E. laculatus	Fiddlers Green		[27]
	E. lacustris	Williamsville		[26]
	E. remipes	Williamsville		[20][26]
	Eusarcana scorpionis	Williamsville		[20]
	Pterygotus cobbi	Williamsville		[20]
	P. cummingsi	Fiddlers Green		[25]
	P. grandis	Fiddlers Green		[25]
	P. juvensis	Fiddlers Green		[25]
	P. macrophthalmus	Fiddlers Green Williamsville		[28]
	Erettopterus sp.	Fiddlers Green		[25]
	Rhinocarcinosoma sp.	Williamsville		[26]
Planaterga	Bunaia woodwardi	Fiddlers Green		[25]
	Limuloides eriensis	Fiddlers Green		[25]
	Pseudoniscus clarkei, P. roosevelti	Fiddlers Green		[25]
Arachnids	Palaeophonus osborni	Fiddlers Green		[29]
	Proscorpius osborni	Fiddlers Green		[30]
Machaeridians	Lepidocoleus reinhardi	Fiddlers Green		[25]
Graptolites	Climacograptus ultimus	Fiddlers Green		[25]
		Fiddlers Green		[25]
		Fiddlers Green		[25]
		Fiddlers Green		[25]
Crustaceans	Ceratiocaris aculeatus, C. maccoyana	Fiddlers Green		[25]
		Fiddlers Green		[25]
		Williamsville		[20]
Cephalopods		Fiddlers Green		[25]
	Gomphoceras ruedemanni	Fiddlers Green		[25]
		Fiddlers Green		[25]
		Fiddlers Green		[25]
	Trochoceras cf. anderdonense	Fiddlers Green		[25]
	Orthoceras sp.	Fiddlers Green		[25]
		Fiddlers Green		[25]
Gastropods		Fiddlers Green		[25]
		Fiddlers Green		[25]
	Platyceras (Platyostoma) sp.	Fiddlers Green		[25]
Bivalves	"Hercynella" buffaloensis	Fiddlers Green		[25]
		Fiddlers Green		[25]
	Goniophora sp.	Fiddlers Green		[25]
		Fiddlers Green		[25]
		Fiddlers Green		[25]
Ostracods		Fiddlers Green		[25]
	,	Fiddlers Green		[25]
		Fiddlers Green		[25]
Polychaeta		Fiddlers Green		[25]
	Spirorbis sp.	Fiddlers Green		[25]
Rhynchonellata	Camarotoechia cf. andrewsi	Fiddlers Green		[25]
		Fiddlers Green		[25]
		Fiddlers Green		[25]
		Fiddlers Green		[25]
		Fiddlers Green		[25]
Edrioasteroidea		Fiddlers Green		[25]
Strophomenata		Fiddlers Green		[25]
Bryozoans		Fiddlers Green		[25]
		Fiddlers Green		[25]
	Stigmatella sp.	Fiddlers Green		[25]
Lingulata	Lingula semina, L. subtrigona	Fiddlers Green		[25]
		Fiddlers Green		[25]
Scyphozoa		Fiddlers Green		[25]
Anthozoa		Fiddlers Green		[25]
		Fiddlers Green		[25]
Stromatoporoidea		Fiddlers Green		[25]
		Fiddlers Green		[25]
Flora		Williamsville		[31]
	Cooksonia sp.	Williamsville		[32]
	Hostinella silurica	Fiddlers Green		[33]
Cyanobacteria	Morania bertiensis	Fiddlers Green		[25]
		Fiddlers Green		[25]

Age[]

The Bertie Formation is late Silurian (Pridoli, or and in the local chronologies).

Interpretations of depositional environments[]

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.^[34] 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 120 to 800 metres (390 to 2,620 ft).^[35] Zones of stromatolites and thrombolites (non-laminated algal mounds) occur in several formations in the Bertie Group,^[36] along with numerous desiccation cracks.^[35] 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.^[37]

The sediments of the Bertie Group were deposited on the paleosouthern side of the subsiding , flanking the northern rim of the Appalachian foreland basin of Laurentia.^[14][38]

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,^[14] and the evaporites and casts of halite pseudomorphs, with sides of up to 30 centimetres (12 in), suggest the environment was far from normal marine; hypersalinity must have prevailed throughout most of the depositional history of the group.^[29] Alternating hypersaline and brackish estuarine conditions have been recorded in the group.^[14] The dolomitization of the group most probably was not primary.^[39]

See also[]

References[]

Bibliography[]

• Armstrong, Derek K., and J.E.P. Dodge. 2007. Paleozoic Geology of Southern Ontario, 1–27. Ontario Geological Survey. Accessed 2019-03-23.
• Brett, Carlton E.; William M. Goodman; Steven T. Loduca, and Denis Tetreaul. 1999. Silurian-Early Devonian sequence stratigraphy, events, and paleoenvironments of western New York and Ontario, Canada, 1–58. NYSGA. Accessed 2019-03-23.
• Burrow, Carole J., and David Rudkin. 2014. Oldest Near-Complete Acanthodian: The First Vertebrate from the Silurian Bertie Formation Konservat-Lagersta¨tte, Ontario. PLoS ONE 9. 1–7. Accessed 2019-03-23.
• Edwards, D.; H.P. Banks; S.J. Ciurca, and R.S. Laub. 2004. New Silurian cooksonias from dolostones of north-eastern North America. Botanical Journal of the Linnean Society 146. 399–413.
• Ettensohn, Frank R. 2008. The Appalachian Foreland Basin in Eastern United States. K.J. Hsü: Sedimentary Basins of the World, Vol 5, The Sedimentary Basins of the United States and Canada 5. 105–179. Accessed 2019-03-23.
• Hewitt, D.H. 1972. Paleozoic Geology of Southern Ontario, 1–19. Ontario Division of Mines. Accessed 2019-03-23.
• Lau, Kimberly. 2009. Paleoecology and Paleobiogeography of the New York Appalachian Basin Eurypterids (BSc. thesis), 1–48. Yale University. Accessed 2019-03-23.
• Rickard, Lawrence V. 1969. Stratigraphy of the Upper Silurian Salina Group New York, Pennsylvania, Ohio, Ontario, 1–77. New York State Museum and Science Service. Accessed 2019-03-23.
• Sun, S.; F.R. Brunton, and J. Jin. 2014. Sequence Stratigraphic Architecture and Bedrock Aquifers of Upper Silurian to Middle Devonian Strata, Southwestern Ontario, 1–15. Ontario Geological Survey, Open File Report 6300. Accessed 2019-03-23.
• Swezey, Christopher S. 2002. Regional Stratigraphy and Petroleum Systems of the Appalachian Basin, North America, 1. USGS. Accessed 2019-03-23.
• Treesh, Michael. 1972. Sedimentology and Stratigraphy of the Salina Group (upper Silurian) in East-central New York, 1–26. Rensselaer Polytechnic Institute. Accessed 2019-03-23.
• Vrazo, Matthew B.; Carlton E. Brett, and Samuel J. Ciurca Jr. 2016. Buried or brined? Eurypterids and evaporites in the Silurian Appalachian basin. Palaeogeography, Palaeoclimatology, Palaeoecology 444. 48–59. Accessed 2019-03-23.
• Vrazo, Matthew B.; Jeffrey M. Trop, and Carlton E. Brett. 2014. A new eurypterid Lagerstätte from the Upper Silurian of Pennsylvania. Palaios 29. 431–448. Accessed 2019-03-23.

External links[]

• The Eurypterida of New York/Volume 1
• The Eurypterida of New York/Volume 2