| Actual Image
"Swimming" Upstream (44)
Silke
![Gold Star Critiquer/Gold Star Workshop Editor/Gold Note Writer [C: 727 W: 98 N: 1694]](http://i1.treknature.com/misc/g-g-g.gif) (5406) | This sea change for my gallery was brought about by two things. First of all I started thinking more about rocks and minerals when I was doing the research for my series on the geology of the California coast. Secondly, I was invited to do some shooting for an amateur mineralogist this past weekend.
If TrekNature will allow this, I shall be posting a few of the images over the next few weeks. And rather than giving the location where they were shot, I shall give the location from which they originated wherever possible.
The first in the series is this 7" (17 cm) Knightia fossil, which comes from the Green River formation, an area of sedimentary accumulations from a prehistoric lake. Knightia fossils are found in abundance in the limestone that is harvested from the 25,000 square mile area that also extends into west Colorado and east Utah. This is an area that was covered by a large inland lake 40 to 50 million years ago. It appears that during the Eocene Era the region was sub-tropical to temperate. However a relatively brief period of cold caused a partial die-off of the sea life and the same cold caused the dead fish to sink quickly due to a less inflated swim bladder. The latter, combined with the great depth of the lake and the lack of oxygen at those depths prevented scavengers from disturbing the carcasses. So they were simply covered up by sediments that compacted and eventually formed the limestone layer in which they are now found.
The Knightia were apparently a schooling fish related to the modern herring. Not only did they travel in schools (clusters), but they apparently died in schools and are thus found closely grouped within the sediments.
This specimen has been uncovered by carefully scraping away the relatively soft limestone from around the bones with a dental instrument normally used for cleaning teeth.
Tech: shot in RAW, handheld and in available light from directly above the display table on which it lay. Contrast adjustment, slight cropping, resized for TN and sharpened edges only.
Captured and published with the permission of Dr. Peter Russell, Curator of the Earth and Environmental Sciences Museum at the University of Waterloo
Thanks for looking and have a memorable week :D
Research source: http://www.fossilmall.com/Science/Sites/GreenRiver/GreenRiver.htm |
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