Hello.  There are outcrops of Silurian fossiliferous marine volcaniclastics near Eastport.  I had a student do a project on them in 1999.  Mostly favositid corals, also trilobites, brachiopods and crinoids.  The latter three are preserved as external molds.  We did not look for microfossils.  Have you contacted Lisa Churchill-Dickson?  She is the most knowledgeable about Maine paleontology.  Good luck.

Hi,

maybe encrustation or  bioerosion of endolithic organisms.

Ask in the topic Ichnology for expert analyse.

From what is visible, i would also search first in the field of corals ... what is known about the petrography and depositional environment of the rock?

Inner structure is not seen. If you could make a grinding-in of a fragment of this rock it would be possible to do some more reliable identification. Preliminarily, with doubt, I would suppose something microbial.

From my observing, the white substances in the circles are on the surface. There are some charring erosive characters under the white material .maybe that is melted elevated temperature substances dropped on the surface of the fossilized object.

Hi John,

for me this material looks more after a fragment (volcanoclast, or volcanic bomb) of spilite (a strongly alterated oceanic basalt), embedded in a volcanoclastic sediment. I have seen very similar material in the Lower and Middle Devonian of  Germany.  Submarine intruded basalts tends to be fine-grained and porous even with lots of "bubbles". During diagenesis most of the amorph volcanic glas of the matrix became destroyed and is replaced by calcite and even all former bubbles are filled by calcite. So it would not be a surprise if it reacts with acid, but its probably not a limestone (judging after this photo)

If this is indeed a sequence of Silurian volcanoclastites as mentioned by Russel one may expect also fossils, because life could be good in time without much eruptions around an ancient volcano.

It would be good to prepare thin sections of the  material to be sure. At least I can't see a fossil there and believe me, I have seen a lot of trilobites, brachiopods et cet;. ;-) The usual preservation in such a facies are indeed internal moulds.

regards,

Jens

I agree with the spillite interpretation. I've worked in volcaniclastic and interbedded sedimentary rocks a lot, and this looks like an igneous clast. At least, there's no sign here of anything diagnostically organic, but of course you'd want to see a section to be absolutely sure.

Thanks to all.  This is a clast in a conglomerate that is presumed to be Silurian in age.  It basically cannot be removed form the glacially polished outcrop of low-grade metamorphic rock.  The unit is metamorphosed to greenschist facies.  While volcaniclastics are common in this area, this unit is important because it contains granite clasts, and clasts of sedimentary rocks, including quartzite. (it is important because these are basement lithologies.)   We know that basement is Cambrian and Neoproterozoic.  It is possible that this is basalt, although I think this is unlikely - the basalt clasts in this unit - which are common - show clear greenschist assemblages, and are greenish as a result. I will go back, hopefully, and see if I can get a close up to see internal structure, if there are any.

I am nit shure, bu It is resemble to colonial corals: may be syringoporids. It is necessory to see the longitudinal section.

Thanks to all on this old post.  We since dated the unit (U/Pb on detrital zircon) and found that it is almost certainly incorrectly mapped as Silurian, and is likely Neoproterozoic.  I suspect we are looking at altered spillite.