It’s a good point about Davis … I don’t know that part of the history, that was around same time as Powell, did they influence each other? Did one influence the other more strongly? I don’t know…would be worth learning about. But, yes interior basins that are not linked to sea level can certainly have their “own” baselevel.

As for your questions about detecting rhythms in the rocks … it’s a very fascinating subject. There’s an entire field of ‘cyclostratigraphy’ that aims to do just that. Commonly, as you say, it is with varve-rich sequences or other sedimentary systems that are sensitive and more direct recorders of external forcings (typically, but not always, from quiet environments and chemical sedimentation).

In terms of whether or turbidites can be used … well, I have a paper in review right now that documents a potential example of just that (I’ll post about it here once it’s in press). But, more generally, turbidite sequences are a lot “noisier”; that is, they are recording the frequency and magnitude of sedimentation events, but what’s controlling the occurrence of those events, and so on … the signal from the underlying external control is diminished (or completely destroyed) as a result of numerous intermediary steps along the source-to-sink pathway. In other words, turbidites have a low signal-to-noise ratio.

All sedimentary systems have a variable degree of “noisiness”, so the goal is how to detect the real signal. Or, even more fundamentally, is the signal maintained at all? There has been some interesting work down in the last decade with physical experiments that suggest external forcings get so masked by all the inherent (and intrinsic) complexity of a sedimentary system that it’s often undetectable. I’ll stop myself before I go on forever … I hope that addresses your questions.

I think the quote about nature’s rhythms is very interesting, and I wonder if fractals somehow could fit in with some of these ideas? I’m also wondering if the repetitive or semi-repetitive beddding of some turbidite sequences – or maybe I’m thinking of varve-like sequences in general? – fit in with these ideas about rhythyms.

As a non-sedimentologist, maybe I’m a little over my head here! In deep water? ;)

The concept of baselevel as first introduced by John Wesley Powell, which is what Barrell is addressing, is a horizontal global surface, which is, in many cases, sea level. Wheeler, however, turned it into a non-horizontal dynamic surface that is a description rather than a control.

Perhaps it’s semantics or ‘splitting hairs’ but, to me, baselevel is more inclusive. Sea level is indeed a baselevel … but, as you point out, what about for nonmarine/fluvial or deep-marine? What about for the areas up- and down-system of sea level? In other words, calling sea level the ultimate baselevel no matter what is limiting.

Now, maybe the whole concept of baselevel doesn’t apply for the deep marine … as you allude to. In more recent papers, the concept of an equilibrium profile (as a function of gradient, topography, and confinement conditions) might be the closest thing to the baselevel concept as was discussed nearly 100 years ago.

It seems to me that the concept of ‘baselevel’ in stratigraphy belongs to the latter category: it is questionable whether a new term is needed to describe a “surface toward which external forces strive, the surface at which neither erosion nor sedimentation takes place”. Why should we talk about baselevel rise when we could simply say sea-level rise. It makes some sense to explain river incision as the result of baselevel drop (although even in this case baselevel is in fact sea- or lake level, so why introduce another layer of abstraction and terminology); but it is quite confusing to try to think about baselevel drops or rises in the deep sea: the bottom of the ocean moves pretty slowly in a vertical direction. I guess at the time Barrell was thinking about baselevel, very little was known about the deep sea, so he did not consider what happens to sediments once they somehow manage to get off the continental shelf.

Or is this more confusing that the idea of baselevel itself?…