Trace fossil ?

[Rockwood]

Found on a spoil pile in the Mazonia wildlife management area, northern Illinois. I've found a couple other cool trace fossils in the area. Is this one ?

[Johannes]

Those are "just" non-organic sediment structures (load casts). But nice ones.

Edited August 3 by Johannes

[supertramp]

1 hour ago, Johannes said:

Those are "just" non-organic sediment structures (load casts). But nice ones.

Too small in size, I think

[Johannes]

48 minutes ago, supertramp said:

Too small in size, I think

You are right, they are very small. Did you have any reference about minimum sizes except SELKER 1993*? I'm interested: what's your Idea? Maybe chute-and-pool-structures?

 

Best regards

 

Johannes

 

 

 

*Selker JS 1993 Expressions for the formation of load casts in soft sediment. J.Sed.Res. 63(6), 1149-1151.

Edited August 3 by Johannes

[Tidgy's Dad]

I think it is what we used to call 'calcitic creep' . 

Just a calcite growth along a bedding plane. 

[Rockwood]

54 minutes ago, Tidgy's Dad said:

I think it is what we used to call 'calcitic creep' . 

Just a calcite growth along a bedding plane. 

The 'calcitic' does seem to have crept away from the fossils in the area. Everything is well silicified, and beekite is present.   

[Johannes]

Looking on the flat sediment surface opposite to the structures, there are little holes along/above the thickest "rigde" of the sediment structure I would interprete as "dewatering structure". For me, this would strenghten the idea "load cast", even if the size of the structure is very small... But I'm open minded for better suggestions...

[supertramp]

if not what Tigdy's dad indicated (it should be easy to establish the calcitic nature if that is the case), I would go towards an inter-laminar moulds at the base of ripples; I don't know the English for the italian “controimpronte frondescenti” anyway; but again, we're at the limit of their typical size.

[Rockwood]

7 minutes ago, supertramp said:

 an inter-laminar moulds at the base of ripples

Micro turbidite ?

[Mahnmut]

Hi,

after deciding not to go out on any limbs so short after my last piece of questionable wisdom, here are my thoughts:

My first idea when I saw the picture was "load casts" (a term I learned here on the forum some time ago). The alternatives you mention are new to me.

Wikipedia tells me the wavelengths of load cast structures can vary from few milimeters to tens of meters depending on viscosity and density difference, without mentioning from which of the listed sources this information is taken.

Very nice structures anyway.

Best regards,

J

[supertramp]

Sorry for the late reply;

here's an example of the structures I was referring to; the photos are from the sedimentography atlas by Franco Ricci Lucchi ("Sedimentografia" - Zanichelli), one of the leading Italian (and not only) experts on turbitic sediments; the scale at the bottom, barely visible even in the original, is in mm. As you can see, we are at the lower dimensional limit with respect to Rockwood’s sample
Ciao

 

[Mark Kmiecik]

Those who collect Mazon Creek nodules know them as "leaverites". 

[Rockwood]

1 hour ago, Mark Kmiecik said:

Those who collect Mazon Creek nodules know them as "leaverites". 

I get tired of them, and I need a break from the ticks and chiggers. It's nice to collect a fossil I can see once in a while.