I didn’t dig into my old textbooks, but my recollection is that to be a breccia they clasts should be quite angular. Your question is a good one, I’m not sure what the ‘cutoff’ is in angularity. I think sub-angular would still probably be called a conglomerate, but that would be something to look up.

Rich asks: “Should one describe a granule grade siliclastic as a conglomerate? Well, to be precise I guess so, “granular conglomerate” may be.”

Yes, I’ve seen the term ‘granular conglomerate’ used in papers. I’ve also seen the term ‘pebbly sandstone’ used when there is a distinct bimodality (pebbles and sand, but not much in between)

Rich asks: “So my question is, why do we use “conglomerate”, when “rudite” may be a more suitable term, especially when used in conjunction with arenite?. In the same vein, why are argillaceous rocks rarely described as lutite? Lutite/arenite/rudite descriptors, also accommodates carbonates and siliciclastics, and a mix of the two quite well.”

I’m not sure why that is not used. It seems to be more prevalent in the carbonate literature (which I don’t read often at all) but, as you point out, could be used generically. I guess it’s one of those things … interesting … I might do a bit more digging around.

Rich asks: “On the other topic, have you seen a complete A-E bouma sequence in a single outcrop, or mapped along dip?”

Oooh … very interesting (and fun) question. I think I’ll save that one for a blog post. Hopefully I can get to that soon.

Indeed, cobbles can be transported in suspension. The reference to “conglomerates” was aimed at the use of the term. When does a conglomerate become a breccia? (50%?) How angular do the clasts have to be? (sub-rounded=conglomerate; sub-angular = breccia?). In this case, breccia being the sedimentological one, not the volcanic one!. Confusing?, may be.

Can you think of another lithological descriptive term that is defined on both grain size and texture?

Should one describe a granule grade siliclastic as a conglomerate? Well, to be precise I guess so, “granular conglomerate” may be.

So my question is, why do we use “conglomerate”, when “rudite” may be a more suitable term, especially when used in conjunction with arenite?. In the same vein, why are argillaceous rocks rarely described as lutite?

Lutite/arenite/rudite descriptors, also accommodates carbonates and siliciclastics, and a mix of the two quite well.

On the other topic, have you seen a complete A-E bouma sequence in a single outcrop, or mapped along dip?

Just a few random thoughts. May be a topic for the blog???

Keep up the good work, always an enjoyable read.

Regards

Rich.

I would agree that the sed flux was likely high … but actually quantifying flux (volume sediment per unit time) will have to wait until we can somehow date the time a grain/clast was deposited (c’mon geochronologists!).

These conglomerates were deposited in 1000-2000 m of water … so, while every single bed may not be a ‘turbidite’ sensu stricto (i.e., Bouma sequence), these beds do represent sedimentation several 10s to 100s of km from their entry point into the basin. And, yes, cobbles can be transported in suspension. :)

Nice rocks! and nice work.

Sounds like there was a great deal of sediment flux here. You mention Upper Cretaceous, do you know how much time is represented by the Lago Sofia Member? and has there been any work on sedimentation rates within the LS Member?.

Would be interesting to attempt to build a geohistory and assign the levee sediments with the channel-fill. I’d bet there are some significant time gaps here. If so, they may be apparent in the levees.

“turbidites”; “conglomerates” I’ll leave that to another day, when I’m feeling extremely pedant! :-)

Cheers,

Rich.

ps. re photo above….. hard hats?….. anyone?….!! :-)

Your link to the article keeps telling me I need to accept session cookies, even though I think I’m accepting all cookies! Glad you published the abstract here. Look forward to your summary post.