Bertie Group

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]

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.^[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 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.

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]

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 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.^[17]

Arthropods

More information Genus, Species ...

Genus	Species	Member/Formation	Notes	Image
Acutiramus	A. macrophthalmus	Fiddlers Green[18] Phelps Member/Ellicott Creek Breccia[19] Williamsville[18]
	A. cummingsi	Williamsville[20]
Buffalopterus	B. pustulosus	Williamsville[19] Fiddlers Green Phelps Member/Ellicott Creek Breccia[19]
Bunaia[21]	B. woodwardi	Williamsville	A Offacolid Chelicerate.
Carcinosoma	C. scorpionis	Williamsville[22]	Renamed as Cruinnopterus[23]
Ceratiocaris[24]	C. acuminata	Williamsville
	C. maccoyanus	Unknown
	C. praecedens	Unknown
Cruinnopterus	C. scorpionis	Williamsville[22]	A Carcinosomatid Eurypterid originally described under the genus Carcinosoma.[23]
Clarkeipterus	C. testudineus	Fiddlers Green Phelps Member/Ellicott Creek Breccia[19] Williamsville[19]	A Dolichopterid Eurypterid originally described as Dolichopterus? testudineus[25]
Diploaspis	D. praecursor	Fiddlers Green Phelps Member	A Chasmataspidid Chelicerate.[26]
Dolichopterus	D. herkimerensis	Fiddlers Green Moran Corner[27]	A Dolichopterid originally referred to D.? testudineus from Cranes Corners.
	D. jewetti	Fiddlers Green Ellicott Creek Breccia/Phelps Member[19]	A Dolichopterid Eurypterid.[27]
	D. macrocheirus	Williamsville[19]	A Dolichopterid Eurypterid.[27]
	D. siluriceps	Fiddlers Green Williamsville	Considered a Junior Synonym of C. macrocheirus[23]
	D. sp[19]	Moran Corner Akron/Cobleskil Williamsville Ellicott Creek Breccia/Phelps
Emmelezoe[28]	E. minnuta	Unknown	Emmelezoe has been regarded as a junior synonym of Ceratiocaris.
Erieopterus	E. pustulosus[citation needed]
Eurypterus	E. dekayi	Williamsville[19] Moran Corner[19]
	E. laculatus	Cobleskill[29]
	E. lacustris	Williamsville[19] Moran Corner[19] Akron/Cobleskill[19] Fiddlers Green Phelps Member/Ellicott Creek Breccia[19]
	E. remipes	Fiddlers Green Phelps Member/Ellicott Creek Breccia[19] Vernon Member[19]
Eusarcana	E. scorpionis	Williamsville[23]
Gonatocaris[citation needed]	G. sp.
Limuloides?	L. eriensis	Williamsville[30]	likely a Bunodid but its fragmentary nature makes generic identification difficult.[31]
Naraoia	N. bertiensis	Williamsville[32]
	N. cf. bertiensis	Fiddlers Green Phelps Member[32]
Proscorpius	P. osborni	Fiddlers Green[18] Phelps Member/Ellicott Creek Breccia[33]
Pseudoniscus	P. clarkei	Fiddlers Green[18]
	P. roosevelti	Unknown[34]
Pterygotus	P. cobbi	Williamsville[20] Fiddlers Green Phelps Member/Ellicott Creek Breccia[19] Falkirk?[20]
	P. juvensis	Fiddlers Green[35]	Reinterpreted as juveniles of A. macrophthalmus
Erettopterus	E. sp. [citation needed]	Fiddlers Green
	E. grandis	Fiddlers Green[23]
Rhinocarcinosoma	R. sp.	Williamsville[19]
Ostracods	Eukloedenella umbilicata	Fiddlers Green	[36]
	Leperditia alta, L. scalaris	Fiddlers Green	[36]
	Zygobeyrichia cf. regina	Fiddlers Green	[36]

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Acanthodians

More information Genus, Species ...

Genus	Species	Member/Formation	Notes	Image
Nerepisacanthus	N. denisoni	Williamsville	The only vertebrate found in the Bertie Group[37]

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Molluscs

More information Genus, Species ...

Genus	Species	Member/Formation	Notes	Image
Dawsonoceras[38]	D. oconnellae	Fiddlers Green
Gomphoceras[39]	Gomphoceras ruedemanni	Fiddlers Green
Mitroceras[38]	M. gebhardi	Fiddlers Green
Pristeroceras[38]	P. timidum	Unknown (Buffalo, NY)
Trochoceras[38]	T. cf. anderdonense	Fiddlers Green
Orthoceras[38]	O. sp.	Fiddlers Green
	O. vicinus	Unknown
Phragmoceras[39]	Phragmoceras sp.	Fiddlers Green	[36]
Loxonema[38]	Loxonema bertiense	Fiddlers Green
	Mesocoelia gregaria	Fiddlers Green	[36]
	Platyceras (Platyostoma) sp.	Fiddlers Green	[36]
Hercynella[38]	"H." buffaloensis	Fiddlers Green
	Modiolopsis dubius	Fiddlers Green	[36]
	Goniophora sp.	Fiddlers Green	[36]
	Nuculites sp.	Fiddlers Green	[36]
Rhytimya[38]	R. buffaloensis	Fiddlers Green

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Flora

More information Genus, Species ...

Genus	Species	Member/Formation	Notes	Image
Cooksonia[42]	Cooksonia cf. hemisphaerica	Fiddlers Green Phelps Member
	Cooksonia sp.	Williamsville Fiddlers Green Phelps Member
Hostinella[42]	H. silurica[38]
	H. sp.	Williamsville Fiddlers Green Phelps Member
Inocaulis[42]	I. lesqueureuxi	Williamsville
Dasycladophyceae	Medusaegraptus graminiformis	Fiddlers Green
Morania[38]	M. bertiensis	Unknown
	Calithamnopsis silurica	Fiddlers Green

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

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.^[43] 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).^[44] Zones of stromatolites and thrombolites (non-laminated algal mounds) occur in several formations in the Bertie Group,^[45] along with numerous desiccation cracks.^[44] 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.^[46]

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.^[14][47]

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.^[48] Alternating hypersaline and brackish estuarine conditions have been recorded in the group.^[14] The dolomitization of the group most probably was not primary.^[49]