New stromatolite donation

2013-12-05aA frequent activity in my job is responding to public requests for identification of possible fossils. The majority of these turn out to not be fossils at all, but a few are, and some of those eventually make their way into a museum collection.

A few months ago, after reading some of my blog posts about thrombolites and stromatolites, Robin Boucher contacted me to confirm the identity of some possible stromatolites he had collected in Montgomery County, Virginia. Sure enough, Mr. Boucher’s identification was correct, and it turned out he had a large number of stromatolites with nice laminations visible in cross section:

2013-12-05b

Mr. Boucher arranged with the landowner, Cynthia Pitonyak, to have the specimens donated to VMNH, and delivered them personally a few weeks ago.

These stromatolites were collected from the Cambrian Elbrook Formation, which is older than the Conococheague Formation that produced the Boxley thrombolite, but probably deposited in a similar near-shore setting. It’s interesting that the older Elbrook specimens are laminated stromatolites, while the younger Conococheague specimens are non-laminated thrombolites. Walter and Heys (1985) suggested that in the Cambrian thrombolites became more common because increased burrowing destroyed stromatolitic laminations. If they’re correct, we may have caught the point in time in Virginia when burrowing increased enough that stromatolitic textures were being replaced by thrombolitic textures, resulting in the change in algal mounds we see from the Elbrook to the Conococheague.

Thanks to Mr. Boucher and Ms. Pitonyak for donating these interesting specimens to the museum.

Reference:

Walter, M. R. and G. R. Heys, 1985. Links between the rise of the Metazoa and the decline of stromatolites. Precambrian Research 29:149-174.

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3 Responses to New stromatolite donation

  1. Mike Huggins says:

    Here’s a good link to a paper by Va Tech’s Fred Read and Ken Eriksson to put these Elbrook stromatolite finds in context of Virginia regional geology. http://vtechworks.lib.vt.edu/handle/10919/19078 (download paper in PDF form). Fred’s grad student Bill Koerschner was Mr. Elbrook and Conococheague, and his work (and that of Fred’s other students) is a big part of the section on that part of the sequence (I spent a good part of a summer with Bill over near Radford going over the Elbrook/Conococheague sequence).

  2. Dr. Ken was the first geo person to see my Mt Tabor Road specimens! Thanx Mike for the link to his paper, I am very interested in the geology and paleontology of the area.

  3. Dr. Dooley, Robin Boucher here. Glad the stromatolite sections are in a good home. I have found a thrombolite (in my opinion) at the same site as the stromatolites. I am fairly sure because I cut into it and has the look of clotted masses rather than laminations.

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