|DESCRIPTION OF EURYPTERID WINDROW: A,B,C) Inocaulis. D,E,F) Eurypterus lacustris Harlan. G) E. lacustris folded over on itself. H) Straight cephalopod. I,J) Tergite at edge of the windrow. K) Background (blotchy), ie. organic debris, probably including finely comin- uted eurypterid material, forming the basal layer of the windrow and upon which the above listed fossils occur. Also impressed upon this background are tergites, telsons, swimming legs, carapaces and other fragmentary plant and eurypterid remains.
FOR SCALE: The cephalopod (H) is 16.5 cm. in length (almost 6.5 inches). Williamsville For- mation at the Ridgemount Quarries South, Fort Earie, Ontario, Canada - 2002.
|AT LEFT: A specimen from the Late Silurian Williamsville Waterlime. Note that this animal (a molt) was deposited on its side nearly forming a circle with the extra telson in this 'circular win- drow.' Occasionally, circular currents (gyres) deposited organic remains in ringlike patterns. In one case, I ob- served numerous cephalopods that formed a ring about 1 foot in diameter. Only a strong, swirling current, could have left such a deposit and those in which eurypterid remains are collect- ed into circular areas. Specimen No. 083002-1: Eurypterus lacustris.|
|When I first observed these windrows, in the waterlime layers of the Phelps Waterlime at Passage Gulf northeast of Cedarville, New York (Ciurca, 1963), I became aware of the linear distribution of most of the remains of these arthropods and associated fauna and rare flora. Every other site I have exam- ined, from the base of the Salina Group to the Early Devonian Olney Limestone, exhibited the same phenomena, i.e. most, if not all, eurypterid remains occur in windrows. Eurypterid molts collected, via currents, into linear accummulations of organic remains, and these are what we observe when we encounter these remains in the Late Silurian waterlimes and black shales of New York and Ontario, Canada.
While windrows are important sedimentary structures occurring within the Salina and Bertie Groups, I have observed many other interesting structures, in recent years, and some of these are the sub- ject of the 2002 NYSGA Meeting at Lake George. Newly observed sedimentary structures will have an impact on our interpretation of the paleoenvironments of deposition of the eurypterid-bearing units of the above mentioned groups. There has been a lot of interpretation and speculation on the actual paleoenvironment of the eurypterids. However, these interpretations were based upon limited obser- vations. Because of exceptional exposition of the uppermost surface of the Williamsville A Waterlime, at a quarry in the Niagara Peninsula of Ontario, Canada, I am able to describe many new features not observed previously and that, certainly, will aid in paleoenvironmental interpretation of the eurypterid-bearing units of the Salina and Bertie Groups (Late Silurian) and also the Early Devonian units.
|Eurypterid remains occur, primarily, in windrows, that is current induced collections of debris preserved in the Late Silurian waterlimes and black shales of New York and nearby regions. This debris consists of disarticu- lated eurypterids, many other invertebrates and plants, and more rarely--"complete eurypterids".
COPYRIGHT 2002 Samuel J. Ciurca, Jr., Rochester, New York