In Ontario, Canada, the two Eurypterus-bearing formations of the Late Silurian Bertie Group are exposed at numerous sites. Above is a view of a site in the Niagara Peninsula. The bedrock shown in the above photograph is the top of Williamsville (A) Waterlime.  Below this surface are 18-20 inches of very fine- grained dolostone containing the Eurypterus lacustris Fauna. The smooth surface seen in the above photograph is very re- sistant, almost like a glacially polished surface.  It is, however, very resistant to excavation and represents the interface of Williamsville A Waterlime (the eurypterid-bearing unit) with the overlying Williamsville B unit.  The surface is a STORM EVENT, (TEMPESTITE) replete with sedimentary structures and faunal structures not typically seen in the eurypterid-bearing unit be- low. These include RIPPLEMARKS, 'BOOMERANGS,' RIP-UP CLASTS, a BRACHIOPOD PAVEMENT, and fossils including CEPHALOPODS  and GASTROPODS--and TRACE FOSSILS. See Ciurca in New York State Geological Association Fieldtrip Guidebook
Niagara Peninsula, Ontario, Canada
BELOW: Large blocks of Williamsville Waterlime in the quarry at Fort Erie, Ontario, Canada after a great blast of the bedrock.  Lefthand corner of the photo shows the quarry wall with vegetation grow- ing atop.  Note the straticulate nature (varvelike) of the large block in the foreground. The Williamsville Waterlime in this quarry (Ridgemount Quarry South) is 18 - 24 inches thick.  When fresh, the unit is at its maximun thickness--as it slowly weathers over the years, it becomes flagstonelike then platy, weathering into lighter colors (from dark grey to tan to creamish in color).  Water, freezing and thawing, work on the waterlimes to break them down into thinner and thinner layers.  Fossil remains, eg. the eurypterid specimens, probably facilitate breakdown of the layers to reveal the fossils on certain bed- ing planes.  Conchoidal fracture (and weathering) facilitate the exposure of fossil remains and, often, eurypterid remains are found in "conchoids" - ie., the eurypterid specimens are found in dishlike pieces of rock.  This is especially true of the waterlime just below the Williamsville A-B contact (a storm layer, or TEMPESTITE). Blocks of waterlime, like that shown below, must weather before they exhibit the fossils that they preserve within.  Breaking such rocks usually yields conchoidal fracturing - the large blocks do not break parallel to the bedding planes - to reveal the fossils trapped within.