A Selection of Fossils from the ‘March Formation’ in Lanark County, Ontario - A Correction

 I was speaking with my daughter on Thursday and mentioned to her that there were a few things on my blog that were not correct.  She chimed in “Fake News!”   That convinced me to go back, correct and improve my identification of fossils shown in the  photographs that accompanied my September 13, 2013  blog posting.   These are my suggested changes.

1. Bedding Parallel Burrows and Bioturbation in a bed close to the top of the quarry.  Likely early Cambrian (or Ordovician).

2. The Trace Fossil Helminthopsis.  Simple cylindrical, curving burrows roughly parallel to bedding plane.  Possibly Ediacaran, Cambrian or Ordovician in age.

3. Larger, rougher, cylindrical, curving burrows  roughly parallel to bedding plane.  Possibly a worm burrow like Helminthopsis, but more likely arthropod burrows of Cambrian or Ordovician age.

4.  Branching, overlapping, possibly interpenetrating, roughly parallel to bedding plane, some plant like.  Three of the photos probably record Ediacaran microbial mat destruction textures, with the first, second, and fifth photographs possibly show a  reticulate pattern of petee ridges, with the ridges in the first  flattened, or simply sand cracks in a microbial mat.     The second last photo  shows a disc with stalk (below the ruler) and a number of spindle shaped objects that are potentially Ediacaran rangeomorphs. The last photo shows numerous spindle shapes that are possible Ediacaran rangeomorphs (note the medial line on three of the spindles), but the spindle shape is also consistent with examples reported by others as being petee ridges (e.g, see Eriksson et al., 2007, figures  4(c)-8B & 4(c)-9).   The fourth photo might  show Ediacaran vegetation (not rangeomorphs as there is no fractal construction) but is more likely to be a badly ripped  microbial mat.  I cannot identify the structure in the third photo, but note that the same texture is shown in the first four photos on my August 20, 2014 blog posting.

5.  Concentric discoid structure.   More likely the Ediacaran  holdfast Aspidella than medusae. 

6.  Concentric discoid structures.    The second and third  are likely the Ediacaran  holdfast Aspidella. The first might also be.  The fourth is likely Ediacaran, and might be Nemiana or Chuaria or Nimbia occlusa.

7.  A Congestion/Colony of Multiple Ediacaran discoid holdfasts.  Likely Aspidella.  Note that the second photo shows an Ediacaran rangeomorph structure (Bradgatia?) above the 4 1/4 to 4 1/2 inch marks on the ruler.

8. ‘ Lindt Truffles’ (circular, about the size of the candy, with a thin 2-4 mm rim and a different coloured centre) is the name that I used when talking about this structure with the quarry manager in 2013.  They are common at the quarry.   Possibly the Ediacarn fossil Chuaria or Beltanelliformis (=Beltanelloides, Nemiana).  Interestingly the smaller ones can often appear close to a spiral form, and while looking a bit like Gastropods are not as spiral as Arenicolites spiralis, Billings 1872 that was reported to have been associated with Aspidella in Newfoundland.

9.  Thin Film, barely there.  Sack like.   (algae?) (an Ediacaran Tawuia-like fossil?)

10.     In about 2013 I sent these photographs  to paleontologists who study Paleozoic fossil plants. I received the reply  that the photographs likely show a trace fossil.  In about 2013 I sent the same photographs to a paleontologist who has written extensively on Ediacaran and Cambrian trace fossils, who replied that it was likely a plant.   My best guess is  that it is algae or  analogous to algae.   Some linear grooves might be tool marks resulting from the blasting.

11.   Stromatolite  (Dr. Al Donaldson's identification while touring the quarry.)

In my September 13, 2013 posting I stated “The only shelled fossil that I’ve found (and I’ve only found broken parts of it) is likely a Gastropod, and Gastropods have been found in the March Formation.”   That statement is wrong.  I found broken parts of a spiral form that I mistakenly identified as a Gastropod.   I more likely found the Ediacarn fossil Chuaria or Beltanelliformis (=Beltanelloides, Nemiana).

I also no longer believe that Potsdam sandstone outcrops at the quarry. It is Precambrian sandstone of Ediacaran age.

I apologize if I have misled anyone. 
           
Christopher Brett
Ottawa, Ontario