Deer Lake Trip Report - Mahantango - Major Highway Construction - Apr2013

[hitekmastr]

I've been waiting for that work to start up there. They are making a bypass of sorts and was hoping they would cut down into the rock some. I'll have to take a trip up soon.

DEER LAKE TRIP REPORT - MAJOR HIGHWAY CONSTRUCTION

Deer Lake was our first fossil trip this year. If you haven't been there recently, the Deer Lake fossil site is totally transformed. There is major highway construction that wraps around the site and has exposed tons of Devonian rubble. It looks like an on ramp is being constructed there the way it curves around the site. Most of the areas that were previously posted are now part of the construction. There are walls of Devonian exposure, huge piles of rubble, lots of new exposures.

However, in this Mahantango formation, most of the death assemblages are from the late Devonian and are confined to a thin upper layer which seems to be about less than a meter thick - the assemblages we found were in the same layer throughout the site, but hard to locate if you don't know the layer. Everything else is needle in a haystack collecting, sorting through lots of rock and inspecting the newly exposed boulders and rockfaces.

We went on a weekend when there was no construction and there were no signs posted - I have a feeling that there will be no access signs at some point. We saw a few student fossil hunters combing the sides of the highway beds. This exposure is very temporary, and it's not clear what will be left to fossil-hunt after the highway is completed. We're familiar with the site and were very pleased with our finds - This is Nan examining some of the construction rubble, in front of one of the exposed faces. The accompanying photo shows all of the fossils we collected - first examination revealed trilobites (Dipleura), brachiopods, bivalve internals, gastropods, a few cephalopods - the larger rocks in the back were not chiseled open because they looked promising and I wanted to take more care and open those at home.

Here are some closeups of finds from our Deer Lake trip - notable details include the large Dipleura segments. There is a nice gastropod in the lower left corner of the shell assemblage - this is one of several well articulated gastropods we found. The bivalve internal shows fine details and also two of the bivalves have the pedicle preserved.

Edited April 29, 2013 by hitekmastr

[Auspex]

Great report: fast-breaking developments, indeed! Is this now a priority salvage-site for you?

[Fossildude19]

Nice report, Michael.

Thanks for the vicarious field trip.

Were it me, I would hit that site as much as possible 'til it is posted or gone.

Good luck with your home splitters.

Regards,

[Shamalama]

I've been waiting for that work to start up there. They are making a bypass of sorts and was hoping they would cut down into the rock some. I'll have to take a trip up soon.

[hitekmastr]

I've been waiting for that work to start up there. They are making a bypass of sorts and was hoping they would cut down into the rock some. I'll have to take a trip up soon.

I would get there as soon as possible and also, go on a Saturday or Sunday since they don't seem to be working weekends. It's funny, but I was contacting people to find out how to get permission to explore the back portion of the fossil site (behind the parking lot) but was unable to find an owner for that and it looked like that parcel had no owners listed although it had Posted signs. When I arrived Saturday, I was surprised to find the whole thing graded for the new highway/bypass, including mostly the back portion I wanted to inspect. There are death assemblages in a bluish-purple-green with rust colored fossil shells etc. in a thin layer near the top of the formations, throughout the site which I assume is from a late Devonian extinction event since this is consistent everywhere on the site although it's kind of hard to find this layer since it's only about 1 or 2 meters thick. Some of the areas where I found the trilobite pieces are on some of the few remaining marginal areas that haven't been scraped away yet but I'm worried that they will be flattened before I get back. I also found it more rewarding to examine the exposed faces rather than searching the tons of rubble strewn on the ground. It also appears that after the highway is built there may be areas to explore on the sides of the highway but they may be too close to the highway to be safe. It's a window of opportunity, to be sure, and the keep out signs could go up any time.

[Shamalama]

The "death assemblages" are more likely the result of current winnowing by storms. When a storm churned up the water some shells (from both dead and live animals) would get pushed around and redeposited then buried quickly. In the portion of the Mahantango exposed at Deer Lake there are few consistent horizons where one could make a case for a smothered bottom.

[hitekmastr]

The "death assemblages" are more likely the result of current winnowing by storms. When a storm churned up the water some shells (from both dead and live animals) would get pushed around and redeposited then buried quickly. In the portion of the Mahantango exposed at Deer Lake there are few consistent horizons where one could make a case for a smothered bottom.

Must have been a really big storm because the layer I'm talking about extends throughout the site, same layer. Maybe that's just the depth where the dead shells accumulated and were fossilized. All I know is that if I go from one end of the site to the far boundary, and look in the same layer where the band of rock is the same odd color, the death assemblages are in that layer (also most of the trilos we've found). It's difficult to envision the original geology from the record, of course, or why some fossils are concentrated and some not. Imagine all the fossils that never got preserved including species we've never seen or imagined, and that might still be discovered in one of these layers!

[Missourian]

Good trip report and nice fossils. I really like the ornamented trilobite segments and the spiriferids on the slab that seem to have been intentionally arranged.

[hitekmastr]

Good trip report and nice fossils. I really like the ornamented trilobite segments and the spiriferids on the slab that seem to have been intentionally arranged.

I grouped them for the photo but haven't cleaned or prepped anything yet. The reason for my original visit was to get a few more pieces for my "fossil sculpture" series but when we arrived we were surprised to see the massive highway construction had not only flattened and opened a lot of new facings, but also provided access to the area in the back that was previously posted. Have been trying to get back but soonest will be this Sunday when we go to St. Clair and stop at Deer Lake on the way.

[Mattalic]

Are people still able to hit the Deer Lake site? It's been a year + since this report and it seems a lot of work was done in the area.