Bertie Formation

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]

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 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]

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]
	Palaeodictyota buffaloensis	Fiddlers Green		[25]
	Ascograptus sp.	Fiddlers Green		[25]
	Orthograptus sp.	Fiddlers Green		[25]
Crustaceans	Ceratiocaris aculeatus, C. maccoyana	Fiddlers Green		[25]
	Emmelezoe minuta	Fiddlers Green		[25]
	Gonatocaris sp.	Williamsville		[20]
Cephalopods	Dawsonoceras oconnellae	Fiddlers Green		[25]
	Gomphoceras ruedemanni	Fiddlers Green		[25]
	Mitroceras gebhardi	Fiddlers Green		[25]
	Pristeroceras timidum	Fiddlers Green		[25]
	Trochoceras cf. anderdonense	Fiddlers Green		[25]
	Orthoceras sp.	Fiddlers Green		[25]
	Phragmoceras sp.	Fiddlers Green		[25]
Gastropods	Loxonema bertiense	Fiddlers Green		[25]
	Mesocoelia gregaria	Fiddlers Green		[25]
	Platyceras (Platyostoma) sp.	Fiddlers Green		[25]
Bivalves	"Hercynella" buffaloensis	Fiddlers Green		[25]
	Modiolopsis dubius	Fiddlers Green		[25]
	Goniophora sp.	Fiddlers Green		[25]
	Nuculites sp.	Fiddlers Green		[25]
	Rhytimya sp.	Fiddlers Green		[25]
Ostracods	Eukloedenella umbilicata	Fiddlers Green		[25]
	Leperditia alta, L. scalaris	Fiddlers Green		[25]
	Zygobeyrichia cf. regina	Fiddlers Green		[25]
Polychaeta	Serpulites sp.	Fiddlers Green		[25]
	Spirorbis sp.	Fiddlers Green		[25]
Rhynchonellata	Camarotoechia cf. andrewsi	Fiddlers Green		[25]
	Reticularia (Prosserella) modestoidea	Fiddlers Green		[25]
	Howellella eriensis	Fiddlers Green		[25]
	Whitfieldella sulcata	Fiddlers Green		[25]
	Delthyris sp.	Fiddlers Green		[25]
Edrioasteroidea	Pyrgocystis batheri	Fiddlers Green		[25]
Strophomenata	Schuchertella sp.	Fiddlers Green		[25]
Bryozoans	Hernodia sp.	Fiddlers Green		[25]
	Reptaria sp.	Fiddlers Green		[25]
	Stigmatella sp.	Fiddlers Green		[25]
Lingulata	Lingula semina, L. subtrigona	Fiddlers Green		[25]
	Orbiculoidea cf. numulus	Fiddlers Green		[25]
Scyphozoa	Metaconularia perglabra	Fiddlers Green		[25]
Anthozoa	Aulocystis sp.	Fiddlers Green		[25]
	?Ceratopora sp.	Fiddlers Green		[25]
Stromatoporoidea	Stromatopora constellata	Fiddlers Green		[25]
Dasycladophyceae	Medusaegraptus graminiformis	Fiddlers Green		[25]
Flora	Inocaulis lesqueureuxi	Williamsville		[31]
	Cooksonia sp.	Williamsville		[32]
	Hostinella silurica	Fiddlers Green		[33]
Cyanobacteria	Morania bertiensis	Fiddlers Green		[25]
	Calithamnopsis silurica	Fiddlers Green		[25]

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.[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 Algonquin Arch, 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]

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