Dear Jose,

They look like they might possibly be Skolithos - known popularly as "piperock."

Regards,

Bob Skiles 

Dear Dr. Gasca,

the image presented is not very much enlightening and needs some more data about the internal structure and the hanging and footwall rocks. At the moment the tubular structures can be faunal or floral, or even pertain to the wide range of freshwater limestones (tuffa).

H.G.Dill

Dear Jose

As you know morphological characteristic, size and situation of ichno fossils are the most parameters of identification.

however, the primary use of trace fossils is in the interpretation of the paleoenvironment. An ichnofacies is a group of ichnofossils distributed over a wide enough area to characterize the environment. Ichnofacies are distinguished in type by their predominance in fresh or salt water and in their distance from the shoreline or littoral. They range from the Scoyenia ichnofacies which may be footprints on firm ground to the Nereites ichnofacies which are typically grazing traces in deep water offshore. The Skolithos ichnofacies are characteristic of soft intertidal or shallow subtidal marine environments. The Harpers and Erwin (Antietam) Formations are characterized by thick-bedded quartzite in which dense ichnofacies of Skolithos tubes are present. It was at one time hypothesized that these were plant stems or were caused by rising gas bubbles. It is now believed that they were caused by phoronid worms, a phylum of marine invertebrates with an elongated, nonsegmented body that burrow in the sand or mud. This indicates that the paleoenvironment of these formations was a tidal zone, which supports the geologic theory that the quartzite beds were formed by the erosion of the Grenville Mountains.

According to Wilson (2013), Abundant Skolithos burrows are here described from a possible regressive event bed at Ohesaare cliff (Pridoli), Saaremaa, Estonia. The vertical, cylindrical burrows are identified as Skolithos rather than Trypanites because they intercept and bypass rather than cut bioclasts in the limestone matrix. The absence of encrustation on the upper bedding surface also is evidence that these traces are soft-sediment burrows rather than hardground borings. He confirm Skolithos is assigned to shallow water paleoenvironment.

the shape and size support Skolithos in your prepared figure,

Regards

Massih

Looks like Skolithos, there are several references I would particularly refer those of Mary Droser and associates, which you may consult.

José

It seems to be Trypanites (if associated with a hardgound) or Scholitus (associated with relatively soft lime sediment) as are verticals.

Santiago

I SAW THE SAME IN IRAN BASAL CRETACEOUS SEDIMENTS.THE CRETACEOUS STARTED WITH RED CONGLOMERATE AND SANSTONE PLUS SHALE WHICH SHOW TRANSGRESSION OF THE SEA ON THE GROUND, SO IT MAY BELONGS TO FLORA STEM OF JAGLANDACEA FAMILY.

Dear colleagues,

as long as we have only an oblique cut through a rock which we do not know anything about as to its orientation, hanging- and footwall rocks, and the lithology associated with it is largely a rambling around. Therefore I ask for a more precise description of the environment of deposition or host rock lithology. What is the reason for claiming this rock to be laid down in a lacustrine environment ?

Best regards

H.G.Dill

Dear colleagues,

as long as we have only an oblique cut through a rock which we do not know anything about as to its orientation, hanging- and footwall rocks, and the lithology associated with it is largely a rambling around. Therefore I ask for a more precise description of the environment of deposition or host rock lithology. What is the reason for claiming this rock to be laid down in a lacustrine environment ?

Best regards

H.G.Dill

Dear colleagues,

as long as we have only an oblique cut through a rock which we do not know anything about as to its orientation, hanging- and footwall rocks, and the lithology associated with it is largely a rambling around. Therefore I ask for a more precise description of the environment of deposition or host rock lithology. What is the reason for claiming this rock to be laid down in a lacustrine environment ?

Best regards

H.G.Dill

Dear Dr. Dill, the lacustrine setting is marked by the presence of charophytes in next outcrops lateral to the layer bearing ichnofossils. 

 A colleague suggested me the ichnofossil Taenidium as a possible option. Also I can add some important info: I saw meniscated structures in the natural cast of that burrows that reaches the underlying lutitic or marly level

Dear José,

you may consider spatangoid-produced ichnofabrics, if the burrows show meniscate backfill (if lacustrine facies is not for sure, and a marginal marine facies could also be suggested). An ongoing discussion of maybe comparable traces from jurassic marine sediments (with reference recommendations) you can find here:

https://www.researchgate.net/post/Please_can_you_help_me_to_know_about_this_bioturbation_which_I_found_it_in_lower_callovien_of_algeria/1

For lacustrine and terrestrial trace fossils you may check the several papers of  Luis Buatois and Steven Hasiotis. For taking Charophyta as evidence for lacustrine settings you should be a little bit more careful, they are more limited by water turbidity than by salinity. Giving a quote from Winter & Kirst 1990*:

"However, some species are found in marine habitats. There are apparently three categories of charophyte species with respect to the different salinities of their habitats:

(1) obligatory freshwater charophytes

(2) euryhaline inhabitants of brackish and marine waters

(3) 'halophiles accidentelles'

The latter mainly occur in fresh water, but tolerate moderate or temporary enhancement of salinity. "

Best regards

Johannes

*Winter & Kirst 1990 Salinity response of a freshwater charophyte Chara vulgaris. Plant, Cell and Environment 13: 123-134.

Try Edward S. Belt,Amherst College, Researchgate, who is good when these types of organic structrures.