Ordovician Micro Fossils – ID Help Requested

[Walter Piorkowski]

Leitz Ortholux microscope
4X Leitz projection eyepiece plus 1/3x relay lens

Image No.1
Horizontal Field of View - 10.25 millimeters
16 images at .005 inch increments
Nikon 1.2x Plan Achromat objective
Diffused Fiber Optic Illumination

Image No.2
Horizontal Field of View - 3.3 millimeters
13 images at .002 inch increments
Leitz 4x Plan Achromat objective
Diffused Fiber Optic Illumination

Image No.3
Horizontal Field of View - 700 micrometers
165 images at 1 micron increments in area of interest, then 2 microns
Leitz 32x UO Achromat objective, iris full open.
Polarized Diffused Fiber Optic Illumination

Canon 50D
Zerene PMax and Photoshop 7 processing.


Normally, looking at a rock under magnification is not very interesting. However in the case of this Ordovician sea floor sample I have run across two interesting micro subjects.

The first, and undoubtedly most interesting, are the small round black objects visible in these images. I was about to dismiss them as once non-living crystal formations, until I noticed that they all had a single tiny hole in their centers. I don’t believe that a crystal would grow like that. They are scattered about and seem to have some relationship with another odd repeated feature, the green patches nicely visible in the upper and lower right of image three. The green spots may be the base elements of broken off black objects.

The black subjects range in diameter from 100 to 170 micrometers. The subject in image three is roughly 170 micrometers and has a 10 micrometer hole in its center. Polarized light was used to provide as much detail on its surface as possible. The green spots as well as the black objects are on a surface of fine mud, now crystallized that is made up of fine calcium carbonate crystals secreted by marine algae of the period. So this is not sand.

I hope the learned members of this form can tell me what species of extinct animal these are.

Walt

[Peter M. Macdonald]

Walter,

Do these actually go down into the rock, or are they only on the surface? I am wondering if this was a surface which was exposed to the air in the quarry?

Peter

[Walter Piorkowski]

Hi Peter. The objects are all on the surface. I did some destructive testing, so to speak, with a fine needle and was able to easily remove samples from the surface of a solid shell as well as the fine calcium carbonate crystal mud. The black material did not extend into the rock.

There is no doubt that the rock was exposed to the air in the quarry. All the rock samples we had access to had been blasted free by the quarry owner at an unspecified time before our arrival.

Looks like what I have here is not likely from the Ordovician and not a fossil after all. Thanks for your help. What they are still remains a mystery though. Probably the desicated remains of something.
Walter

[Peter M. Macdonald]

Walter,

Looks like these are small lichens growing on the exposed surface. May be worth trying to take them off of the fissil surface, as they can sometime mar calcareous fossils. A wooden toothpick can be a very versatile tool. Also, it will not normally damage things that you do not want to damage. If it is too sharp, you can always snip off the point.

Best wishes,

Peter

[rjlittlefield]

as they can sometime mar calcareous fossils.

Ah, good point! I had wondered about the rings of white material that surround many of the black objects, for example the one shown at high resolution in the third picture. Do you suppose these are reformed rock?

--Rik

[Peter M. Macdonald]

Rik,

Difficult to say. My instinct is that it is probably some of the lichen, although it may contain a little of the limestone.

Quite a number of lichens can produce acids, so best to clean them off of anything which you want to preserve. Keeping them very dry is the next best approach, as there is usually no growth of the lichen unless and until it gets damp.

Peter