Eramosa Karst Conservation Area- Nexus Cave- Hamilton-Ontario-2

The Eramosa is a

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

stratigraphic unit exposed along the

Niagara Escarpment The Niagara Escarpment is a long escarpment, or cuesta, in Canada and the United States that runs predominantly east–west from New York through Ontario, Michigan, Wisconsin, and into Illinois. The escarpment is most famous as the cliff over ...

in Ontario and western New York State. In the late nineteenth century it was an important source of building stone in

Hamilton Hamilton may refer to: People * Hamilton (name), a common British surname and occasional given name, usually of Scottish origin, including a list of persons with the surname ** The Duke of Hamilton, the premier peer of Scotland ** Lord Hamilt ...

, Ancaster and

Waterdown Waterdown was a hardcore punk and post-hardcore band from Osnabrück, Germany. The band emerged onto the scene in 1999 under the formation of: Axel Pralat (guitar), Marcel Bischoff (vocals), Jörg Schwoeppe (drums), Christian Kruse (bass), Holger ...

, and in the late twentieth century quarries in a similar unit, also called the Eramosa, near

Wiarton Wiarton () is a community in the town of South Bruce Peninsula, Bruce County, Ontario, Canada. It is located at the western end of Colpoys Bay, an inlet off Georgian Bay, on the Bruce Peninsula. Wiarton is notable for the Wiarton Willie Festiva ...

in the

Bruce Peninsula The Bruce Peninsula is a peninsula in Ontario, Canada, that divides Georgian Bay of Lake Huron from the lake's main basin. The peninsula extends roughly northwestwards from the rest of Southwestern Ontario, pointing towards Manitoulin Islan ...

, became an important source of dimension stone at a time when most of the other resources of similar stone were depleted. Work in these quarries led to the discovery of exceptionally well preserved fossils (the Eramosa

lagerstätte A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These for ...

). On the east Mountain at Hamilton, a well-developed cave system was discovered in the Eramosa and has now been designated as the

Eramosa Karst The Eramosa Karst is a provincially significant Earth Science Area of Natural and Scientific Interest in Ontario, Canada, located in Stoney Creek, a constituent community of the City of Hamilton, and immediately south of the Niagara Escarpment. ...

Conservation Area.

Stratigraphy

The term was first used for a stratigraphic unit by Williams (1915) who named the Eramosa Member (of the

Lockport Formation The Lockport Formation is a geologic formation in Ontario and New York State. It preserves fossils dating back to the Silurian period. It is named after the city of City of Lockport, New York, where the Erie Canal cuts through and exposes beds o ...

) for the

bituminous Asphalt, also known as bitumen (, ), is a sticky, black, highly viscous liquid or semi-solid form of petroleum. It may be found in natural deposits or may be a refined product, and is classed as a pitch. Before the 20th century, the term a ...

dolomite Dolomite may refer to: *Dolomite (mineral), a carbonate mineral *Dolomite (rock), also known as dolostone, a sedimentary carbonate rock *Dolomite, Alabama, United States, an unincorporated community *Dolomite, California, United States, an unincor ...

s exposed below the Guelph Formation along the

Eramosa River The Eramosa River is a river in Wellington County in southwestern Ontario which rises near Erin, Ontario, and flows southwest through the city of Guelph, where it joins the Speed River, which then enters the Grand River in Cambridge. The rive ...

, northeast of

Guelph Guelph ( ; 2021 Canadian Census population 143,740) is a city in Southwestern Ontario, Canada. Known as "The Royal City", Guelph is roughly east of Kitchener and west of Downtown Toronto, at the intersection of Highway 6, Highway 7 and Wel ...

, Ontario. No detailed description of the type section has ever been published, and the status of the unit has been subject to many different interpretations. Until recently, the Eramosa in Ontario was regarded as the highest Member of the

, with gradational contacts with the Goat Island Member (below) and the

Guelph Formation The Guelph Formation is a geologic formation in New York. It preserves fossils dating back to the Silurian period. See also * List of fossiliferous stratigraphic units in New York This article contains a list of fossil-bearing stratigraphic un ...

(above). In 1995, the

US Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, an ...

proposed a revised stratigraphy based on studies in the Niagara region. It extended the Lockport to Group status and included, from base to top, the Gasport, Goat Island, Eramosa, and Guelph as Formations within the Lockport Group. In a "reference section" in the Niagara River Gorge, the Eramosa was divided into six "units" recognized throughout the Niagara region, but a shaley lower unit previously named for the Hamilton area (the Vinemount Member) was transferred to the Goat Island Formation. Brunton (2009) has proposed a revision for Ontario which restores the Vinemount Member to the Eramosa and recognizes two other members.

Age

The exact age and correlation of the Eramosa are still uncertain.

Conodont Conodonts (Greek ''kōnos'', "cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which ...

s at first indicated that the Eramosa age was Ludlovian (c.420 Ma), but recent studies of both conodonts ''Geological Society of America Abstracts with Programs'', v.40(5) p.22, 2008 and the Eramosa lagerstätte suggest an earlier, late Wenlockian (c.425 Ma) age.

Paleoenvironment

The rocks forming the Eramosa are mostly dolomites, but the composition varies from almost pure, grey-weathering, fine-grained dolomite (at Ancaster) to

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4) and tiny fragments (silt-sized particles) of other minerals, especial ...

y, bituminous, brown-weathering, bioturbated dolomites. Fossils are common at some localities, scarce at others, and chert is generally a minor component. The most characteristic feature is

shaley interbeds. Probably the Eramosa was deposited in several related environments, most likely including shallow, restricted (and poorly oxygenated) marine waters. Among the fossils, perhaps the most spectacular are the

eurypterids Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 million years ago. The group is l ...

, an extinct form of scorpions. Some species lived in fresh or brackish water, but Silurian examples were marine. The exceptionally preserved biota are present in a stratum of rock about 8 m thick, which extends for around in the

South Bruce Peninsula :''South Bruce Peninsula is not to be confused with the Municipality of South Bruce, Ontario'' South Bruce Peninsula is a town at the base of the Bruce Peninsula of Ontario, Canada, in Bruce County between Lake Huron and Georgian Bay. It was form ...

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

. So-called "Eramosa marble" is actually a bituminous dolomite (see

list A ''list'' is any set of items in a row. List or lists may also refer to: People * List (surname) Organizations * List College, an undergraduate division of the Jewish Theological Seminary of America * SC Germania List, German rugby union ...

References

{{reflist Bancroft, A.M., M.A. Kleffner and F.R. Brunton, (2008). Silurian conodont biostratigraphy and δ13 C stratigraphy of the Eramosa Formation, southwestern Ontario, Canada. ''Geological Society of America Abstracts with Programs'', v.40(5) p. 22. Brett, C.E. et al., (1995). Revised Stratigraphy and Correlations of the Niagaran Provincial Series (Medina, Clinton and Lockport Groups) in the Type Area of Western New York. ''U.S. Geological Survey Bulletin'' 2086, 66 p. Brunton, F.R. (2009). Update of revisions to Early Silurian stratigraphy of the Niagara Escarpment: Integration of sequence stratigraphy, sedimentology and hydrogeology to delineate hydrogeologic units. ''Ontario Geological Survey Open File Report'' 6240, p. 25-1 to 25–20. Collette, J.H. and D.M. Rudkin, (2010). Phyllocarid crustaceans from the Silurian Eramosa Lagerstätte (Ontario, Canada): Taxonomy and functional morphology. ''Journal of Paleontology'', v.58(1) p. 116-127. Johnson, M. D., et al. (1991). Phanerozoic Geology of Ontario; in ''Geology of Ontario'', Ontario Geological Society Special Volume 4, pt. 1, p. 907-1008. Von Bitter, P.H et al., (2007). Eramosa Lagerstätte – Exceptionally preserved soft-bodied biotas with shallow-marine shelly and bioturbating organisms (Silurian, Ontario, Canada). ''Geology'', v.35(10) p. 879-883. Williams, M.Y. (1915). A eurypterid horizon in the Niagara Formation of Ontario. ''Geological Survey of Canada Museum Bulletin'' 20, 21 p.