Eurypterids.net
Paleoenvironments
EURYPTERID-BEARING SEQUENCES
Samuel J. Ciurca, Jr.,
Rochester, New York
Sedimentary Structures
SALT HOPPERS 
The distribution of SALT HOPPERS, and other sed- imentary structures formed by the mineral halite, in the eurypterid-bearing Late Silurian sequences,  is a fascinating topic. Most of the stratigraphic occur- ences are within the Salina and Bertie Groups of Ontario, Canada and New York. These groups are within a thick EVAPORITE SEQUENCE and bear much of the salt and gypsum that is mined in the region. The earliest occurrence of salt hoppers appears to be in the lower Vernon Formation, ie. within the eurypterid-bearing black shales near Rochester, New York (eg. Pittsford Black Shale). The highest occurrences are in the upper portions of the Akron Dolostone of the Niagara Peninsula, Ontario, Canada; and still higher, in the Moran Cor- ners Formation south of Rochester, New York.
   There are numerous occurrences wherein the central portions of the salt hoppers are hollow and  filled with small crystals of several mineral types. These include Quartz, Calcite, Dolomite, Hematite, Pyrite and Selenite.
   The largest salt hoppers occur within the Bertie Group of Western New York--from Phelps westward to Clarence.  In this region, they range from 6 to 12 inches on a side.  What type of environment would lead to the development of Halite crystals so large?
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WINDROWS
One of the most characteristic features occurring in the eurypterid-bearing units of the Salina and Bertie Groups is the WINDROW.  Most, if not all, eurypterid remains found occur in current-oriented accumulations of eurypterid (and other) debris. Often, segregation of remains is observed, ie. one specific form may occur within the windrow, eg. pterygotid remains, cephalopods, gastropods, etc.
   Accumulations of simple eurypterid parts, like the telsons of these animals, are often  found collected together in windrows  Telsons, of course, are the more resistant structures found (ie. have a better chance of preservation).  Clusters of nearly com- plete  eurypterids are often encountered.
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At left, another example of the salt hoppers occurring in the Ellicott Creek Breccia,  Bertie Group of Ontario, Canada.
 
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STROMATOLITES
To the right is a photo of a lithology I described as TOPOGRAPHIC WATERLIME.  The lamellae, when seen in transverse section, appear like contours on topographic maps.  After observing and tracing this lithology across Western New York and  part of the Niagara Peninsula of Ontario, Canada for several years, I realized that these structures were just one facies of a grand stromatolite/thrombolite complex that stretches for hundreds of miles in the Late Silurian outcrop belt.  This occurrence occurs within the Ellicott Creek Breccia, Fiddlers Green Formation (Bertie Group). The specimen shown was retrieved from Ridgemount Quarry in Fort Erie in Ontario, Canada. CLICK PHOTO TO ENLARGE.
Paleoenvironments 2   STROMATOLITES AND EURYPTERIDS