Dear Mr. Issigonis,

At first glance it looks like a polymictic matrix-supported carbonate breccia. Having a closer look you will recognize there many dark clasts with concave margins whereas others show normal contacts. I know similar contacts from Late Carboniferous to Permian breccias where these special contacts are accounted for by differential pressure solution of the clasts. Some highly soluble ones disappear earlier than others which for special mineralogical reasons have a higher preservation potential. In this case the dark carbonate clasts seem to be the most vulnerable ones contributing to what might be called a “pseudomatrix” which has nothing to do with the primary sedimentation. Even if I do not know what the stratigraphy is it reminds me of similar Paleozoic rock in NE USA where submarine slope deposits are exposed in road cuts, e.g., near Rochester (New York State). Notwithstanding the caveats I would like to direct your thoughts to carbonate-bearing slope deposits (calcareous turbidites).

I do not see any intrusive impact on the structure and texture.

Kind regards H.G.Dill

Hello, according to the photos you have given, it is obvious that this kind of rock should be similar to conglomerate, cemented and formed in the process of short-distance transportation and rapid deposition, similar to the molasse formation deposited in the Piedmont orogenic belt. There are many kinds of gravels in your photos, such as vein quartz, ordinary sandstone (which seems to have bedding), etc. I hope the answer will help you.

Best，

Liu

It seems of sedimentary nature

Dear Michael,

Did you already take an impact breccia into account? I've seen many of them from various impact sites and I have the impression that it could be one. Angular components of varoius rock types (most of them of sedimentary origin?), and a matrix supported structure. However, I do not see any glassy particles but many impact breccias do not contain (former) melt particles. Maybe it would be worth looking for some shocked minerals in thin sections but of course this is not very promissing in carbonate rocks. You might look for e.g. shocked quartz if there are any basement or sandstone clasts too.

All the best,

Elmar

It looks as breccia, may be containing volcanoclastic material

Dear Michael Issigonis this sedimentary rocks and if we see here we can find angular Gravels between cementation or matrix material its Bricia and when gravel rounded in this case we can said Conglomerates

Michael,

The two cores are clearly sedimentary. Liu suggests short distance transport and I would agree, in that the clasts are very angular and the matrix is mainly clay-sized to sandy particles. In the second core there is a faint suggestion of bedding due to water movement. The only fly in the ointment is that the larger clasts are of a variety of rock types that could suggest an origin from a wider area. However, I do not think that such is the case. It resembles a wet debris flow deposit, which has been derived from talus. The talus itself would have been derived from rockfall from a large cliff above. The cliff probably had interbedded strata, hence the variety of rock type within the breccia.

Hope this helps

George Strachan

I already said its maybe sedimentary rocks

Breccia, because of the angular fragments in rock.

Sedimentary breccia - angular fragments supported by a fine-grained matrix suggests a debris-flow deposit

Looks like a polymict breccia of sedimentary origin. I have seen these in the Western Canada Sedimentary Basin related to evaporite karstification (predominantly karsting of evaporites below such strata), although I don't suggest this is the mechanism of formation for your samples. Many of the clasts preserve primary sedimentary textures, such as laminations. Without being able to test with HCl, I would guess most of them are carbonates given the context of the strata you mentioned. The vuggy-like porosity observed in one of the clasts also suggests carbonates.

T. Hauck's suggestion is another possibility. It would be useful to know if evaporites are associated with the breccia and enclosing rocks.

should be sedimentary likely formed under debris flow with low energy

Dear Jim Dixon

There are no known evaporites in that particular area, but there are numerous salt springs in the surrounding area.

Even without evaporites a karstification breccia is a possibility. What is the basal contact like - planar or downcutting?

One contact, not sure of it is the bottom

Can you give a general location of the core? Are you in northeastern Alberta??

If this is the basal contact, plus the red coloration and unsorted nature of the clasts, I suspect it my be a karst breccia

This is clearly a polymict breccia, and the variety of clast types indicates an extrabasinal source - possibly derived from a fault scarp close to the basin margin, or due to exposure of older rocks within the basin along a fault scarp.

Dear Tyler Hauck

Thank you for your excellent contribution. The core is from western Manitoba, south of the 53rd parallel.

Dear Jim Dixon

Thank you for your valuable input. I have another possible contact in the attached, but I am sorry I don't have more information. I logged the core and kept some pictures. Originally those looking at the core thought this was intrusive, as we saw several gneissic fragments, presumably from basement rocks.

Dear Peter Strogen

Thank you for your important contribution. This fault scarp could presumably bring much older fragments into the basin.

The various clast types do tend to indicate an external source but the contacts seem to be indicative of karstic solution. I am uncertain where to go with an interpretation!

Thank you Jim Dixon for your continued valuable contribution.

I have to get more info on the contact areas of this rock.

This rock is probably a volcanic breccia.

Thank you Reza Hanifzadah for your contribution. Most of the answers point to a sedimentary event. I thought originally it was volcanic too, however, I don't have any proof for a violent event.

Hi I'm pretty sure this is a volcanic breccia rock.

Looks like a sedimentary polymict breccia.

Thank you Ramesh Chandra Phani and Reza Hanifzadah for your input into this identification effort.

I think I will need to find the exact contacts of this unit, so I can give you complete information on which to base your judgement.

I will be visiting the core in the near future and hope to take detail pictures of the contact areas.

There is no surprise if the breccia2.png could be an ultramafic breccia, suspiciously and/or plausibly a kimberlite breccia. In the photograph, the matrix appears greenish, but unless megascopic and mineralogical evidence must support. In India, few kimberlite breccias in Proterozoic sedimentary basin have similar appearance. Just my apprehension...but it has to be checked physically.

Dear Ramesh Chandra Phani

This is interesting.

This is what we originally thought it was. We have also identified many indicator minerals usually associated with kimberlite. We are also puzzled with the amount of calcite in the matrix (although the country rocks are limestone and dolomite).

Thanks, most welcome. Eager to know further outcomes of your investigations on this. In this case, the calcite is primary and perhaps genetically related with kimberlite, not necessarily be the recrystallised country rock limestone/dolomite due to igneous intrusion. Please also check your mesage box. Thank you.

Personally I think that this is a polymictic, polygentic & Polylithologic breccia (Possibly sedimentary). I do see many angular clasts from different origin intermixed in a consolidated matrix.

Nevertheless, i have another speculative point of view that you can consider, how about, alteration/rockfall of igneous rocks on an escarpment (volcanic island /atoll), than re-deposition on sea bed ?

I do consider it as a sedimentary breccia.

Thank you Anzor Giorgadze for your valuable contribution.

Looks like a sedimentary breccia because of the angular shape of the fragments and the different sizes

Thank you Elena Hicks for your interesting point. I didn't consider that aspect.