These features occur in disk-shaped concretions in what we suspect are deep water turbidites. I have not seen the rock myself, and alI have is this picture. We are working on more precision on the age of this unit, it may be as young as Upper Eocene.
It reminds me of Nereites or Neonereites uniserialis...
Maybe you should check that.
I suggest to post this image on facebook. I have founded an "Ichnology" FB-page with many professional ichnologists participating. All you have to do is join the group...
From scale and morphology I would reject Nereites/Neonereites but being far away from an ichno-expert
What is the orientation of the specimen in the image? The interpretation of trace fossils really depends on knowing this. Are we looking at a bed sole, top surface, or a section through a bed?
Trace fossil, yes, BUT preservation is way to bad to say anything. Definetely NOT Nereites! The structure is rather a backfillstructure than an actual meandering burrow. However, as I said, preservation is not sufficient to say more. You do not have to give every structures names, you know... :D
May I recommend you the book of Adolf Seilacher. Its title is Trace Fossil Analysis
This is maybe a tighly spaced, helical, horizontal structure, scoured and casted. If so, it is most symilar to Helicodromites, which whorls are distinctly not so tightly spaced
Alfred Uchman
Looks like a three dimensional fodinichnian burrow that is largely horizontal within dark (?mud) interlayers and at high angles to bed surface (lower, right) in coarser (?silty) intervals.
This is a nice trace trace fossil, best refereble to Rhabdoglyphus Vassoievitch, 1951, not a body fossil. The photo isn't great (the lighting doesn't bring out details), and the specimen might be water worn, which perhaps obliterated some details of the transverse ridges at the top and bottom of the picture. The exterior of the specimen is dominated by transverse ridges and doesn't consist of the screw-like whorls of Helicodromites Berger, 1957. Nereites has a longitudinal central depression and two lateral lobes that consist of a series of leaf-like depressions.
MacGabhann (hi, again!) correctly notes that identification really requires knowing if this is the top, side, or base of a bed (determinable in part by slabbing).
If the bottom of a bed (which seems possible), it is important that the six or so transverse ridges in the middle part of the trace below the large crack and "SSE" of the bottom of the yellow pen cap seem to show a steeper upper slope (to the top of the photo) and a more gentle slope toward the bottom of the photo. This sort of roughly cylindrical tube with transverse, closely spaced ridges that mark the outer edges of invaginated "calices" occurs in relatively small traces (to 8 mm wide) on bed bases that are referred to Rhabdoglyphus ichnosp. b by M. Ksiazkiewicz (1970, Observations on the ichnofauna of the Polish Carpathians, p. 283-322, in T.P. Crimes and J.C. Harper (eds.), Trace Fossils, Geological Journal Special Issue 3, Seel House Press, Liverpool). The gentle curvature shown in the photo isn't reported in other Rhabdoglyphus, as far as I know.
R. ichnosp. b was reported to have a long range (Senonian-Paleocene) in 1970 in "flysch" facies, but maybe runs higher.
Vallon's observation that the trace seems to be composed of backfills is borne out by the sections through the backfills at the top of the photo.
I agree with Vallon; they do appear to be backfills. Preservation is poor; however, it is difficult to consider the closely spaced ridges as outer edges of the invaginated calices so typical of Rhabdoglyphus.
The trace fossil preservation is interesting to say the least and difficult to assess without a scale and not seeing it in person. Two options for me: (1) the backfill reminds me of the trace fossil Taenidium, which has uniform backfill meniscae, and (2) soft sediment deformation structures produced by loading during rapid deposition associated in turbidite deposits. I have seen similarly appearing structures thought to be trace fossils with meniscate backfill, but upon closer inspection the uniformity of the fill and matrix and its variation in diameter demonstrated it to be load structures. Good luck!
Quite likely a trace fossil, scale is not clear, may be referred to trailing or crawling traces of bottom dwelers in deep lake.
Thanks for the responses. I have not seen these concretions, but at this point I have seen the unit in the field. The unit is associated with a turbidite assemblage, of probable Eocene age. These are distinctive disk-shaped concretions, thus the trace fossil is almost certainly horizontal and parallel with bedding. I may get a chance to see the actual sample, but this would require a trip to an office in Anchorage, Alaska. As far as I understand, the concretions are in a fine-grained facies, and the weather out and occur as discoid clasts along the shoreline. Because they are distinctive (and weird) they are quickly collected by locals....so we were not able to see context.
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