Geology- working up from basic principles.

If i can politely interject as a newbie...hi!Flowing slurries can self-sort and produce simultaneous strata - ie. strata that are superimposed on one-another, but were formed simultaneously by a flowing, self-sorting slurry. One known mechanism is the "like for like" principle, where particles of similar "dynamic settleability (my term!)"...a function of size (hydrodynamic diameter, etc), shape, density (etc) will accumulate together in "layers" - stratum.An example: Page not found – Sedimentology
(this person/group has done a fair bit of experimentation on this topic, and his/their stuff is worth reading...)Hence, i would assert that for any given series of strata, it is not so much about assuming any given mechanism, but seeing what other features in and around the series are more consistent with a certain mechanism - ie. take into quality of fit with the data, but also quality of arguement.Honestly, i'm not a fan of just assuming Superposition, but believe that higher-energy mechanisms should also be included in the consideration (such as described above).Enjoy (and hello!),
Stewart

Possibly, but i would assert that it all depends on conditions...I've seen experiments with sediment in flumes where sand reaches angles of > 30 degrees.Qith a quick Google, i found this one (photo about 2/3 way down page...other experiments there too!!): Sedimentary experiments: Preliminary reportAnyhow, again, i think it's better not to assume a mechanism (if we are trying to be truly "objective" instead of "dogmatic" (both are OK IMHO!), but to see which best fits the context.Regards,
Stewart

Cora,Thanks for the hello and the response.I'll respond point by point, as it's clearer that way (no, i'm not being picky and facaetious! ):Cora said: "And I'm sure that such experiments have been done. But I don't think that you'll find many flumes supplied with sand-laden sediment out in nature." (PS...i don't konw how to use a "quote tool" )Of course! But it does mean that, give the right conditions, that such features can be produced by moving slurry/sediment - that's my point. A general point-of-view comes into play, where we scientifically obliged to consider such mechanisms.And the non-specificity (non-exactness) of an experiment should not invalidate an "in-principle" extrapolation/induction...otherwqise we start splitting hairs and invalidating a huge number of otherwise accepted notions - even if there ARE just working hypthoses.For a generally relevant and pertinent idea should not be thrown out because it is not EXACTLY what we are after! Surely it just becomes the basis for a potential new perspective, a potentially superior explanation (in terms of fit with the evidence and interal logical structure)? I personally find such notions very exciting. If it involves the changing of previous paradigms, then so be it - that's Science, afterall...Cora said: "And, if I remember this thread right, we were specifically talking about the Coconino Sandstone, where other evidence, like animal tracks and etching of grains, points to being wind-laid."I won't pretend to know too much about the Coconino Sandstone - i am an Aussie after all! But i would have thought that general experiments involving sand particles of various sizes would be at least relevant in principle? I don't understand why you seem to be suggesting they are not - is that because of the non-exactness of the tests? As i explained before, that becomes a bit of a special pleading, doesn't it?As for animal tracks: couldn't that simply imply that there was numerous events, one following another in a given local area, with sufficient time in between for tracks to be formed? I don't see why this is not a valid working hypothesis.Hence, it is not necessarily (ie. cannot be exclusively decucted logically from an "open" set of premises, as we deal with here, and in much of science about the past...) the case that it is wind-blown on the basis of this piece of evidence. I believe we have to be careful about what we call "data"/"evidence"/"fact" and what we call "interpretation"....i would call angles of repose, etching, tracks, size dsitribution, etc, etc, "data"/"evidence"/"fact", and anything more than these observables as "interpretation", where any interpretation is subject to further logical analysis/deconstruction (and that's how we like it, isn't it?!) As for etching: I would have thought that one could also invoke slurry flow tooling as an etching mechanism (ie. "high-energy" particle-particle collisions)? That is, etching/frosting as a result of transport. I thought that was an observed phenomena....?But again it makes me think: shouldn't we simply be asking "what can cause etching", and "how might tracks for preserved", and "can another mechanism (such as flowing slurry)" be invoked to form what we see?" and "Isn't it possible that an alternative mechanism might produce a logically-superior explanation?"As for "assuming a mechanism": logically speaking, data doesn't speak for itself - that's a fallacious notion. All people have the same data, and all have their starting points for logical interaction with it. If we invoke the same basic logical processes (in this case, the scientific method), a come up with a different result, then, logically speaking, it is only because we have different starting points, different starting assumptions.SOOOOO () when i say "assuming a mechanism", i'm only suggesting a logical imperative - one has to start somewhere, then develop the logic, and then see how satisfied with it they are (ie. how well it fits). So, of course people have assumed a mechanism - the data isn't self-evident, and one MUST assume premises/axioms/etc, otherwise one can't deduce anything at all.But it's just a matter of WHAT premises one chooses to start from...and i'm just suggesting that, perhaps, an assumed mechanism involving flowing slurry/moving sediment is a valid and relevant consideration, given its experiementally-verified abilities to produce the same general forms and traits that are said to be wind-blown...Isn't that a valid point of view?Regards,
Stewart

Hey RAZD. Thanks for responding. I can heartily agree with this - anyone who calls themself a "scientist" is "philosophically obliged" to consider all proposed angles, else they are dogmatists (mind you, i think most people are dogmatists most of the time, anyhow, with the occasional idealism slipping in, not actually the other way around....!) I certainly can't disagree with that! And how could I?: It's a small scale experiment, that is certainly not anything like the scale of rock strata one is describing and investigating! It's also simplified in its complexity, it's dynamics - one would expect a real event of such magnitude to have far more complicated hydro-dynamic and geo-chemical interactions, would one not?Hence, in all honesty, i have to take your comment as trivial... But couldn't i just as easily claim that an increase in the complexity of the experiment would satisfy some of the said problems? Surely we have to be careful in denying generalised inductive logic, or we'll stall science in its tracks.... but we've also got to ask the question, because i think it's being begged: let's say that increases in the scale and complexity of the experiments produced results that are more and more like the strata we are investigating - ie. more complex, larger scale (simply because we've increased complexity and scale!)....then what? Will we continue to deny valid induction/extrapolation, if even at least as a strong basis for some serious further investigation? Or, at what point does the experiment provide a valid basis for an alternative model? Does it have to be exactly the same size as the strata under consideration, and have exactly the same components? When is enough enough?Additionally, why is the evidence "inconvient"? I'm not quite sure why you're saying that, or at least why you would be saying that at this point in the conversation. Too many people think that evidence "speaks" - but it doesn't: it's mute. Consequently, no evidence is "inconvient", merely "evidence" and merely awaiting incorporation into a model that includes experimental support. Aha...sorry, not true. Silty clay does not necessarily take a long time to deposit - this assumes a Stokian settling regime, considering dry particle hydrodynamic diameter and density only; it does not consider the very significant impact of water chemistry on these colloidal and near-colloidal size particles. But it's good you brought it up.Coagulation and flocculation (how i've made my crust for the last 6 years, water treatment) of these types of particles is actually the norm, not the exception - dissolved (both inorganic and organic) interact with the particle surfaces, and can (and usually do) cause particle agglomeration...which affects the hydrodynamic size and densities of the particles - and, thus, their settling characteristics.As a result, particles can have their settling rates increased by orders of magnitude WRT their calculated Stokes Settling rates. It has not been uncommon for me to see colloidal clays with Stokes Settling rates of years per metre accelerated to metres per minute with the appropriate water chemistry (HUGE range! normal!), and a little agitation (for particle-particle agglomeration opportunity). It's really, really easy to do, too, and happens readily.Actually, there's been some university flume work conducted on exactly this aspect...i'll find the references if you or anyone else are interested...Infact, it's such a common phenomena, that to this day i wonder why people still assert that clays have to settle really slowly? "Under what conditions?" i ask, and those conditions are almost always the exception to the rule, being quite uncommon in nature. But perhaps that's just a chemical engineer's perspective on all this....but bringing it back to the point of the thread: General Principles.A "Law" can't be a "law" if it has exceptions; that's why the Principle of Superposition is only a Principle (which is great!) but perhaps no longer even deserves such a title, given that flowing slurries (a very common phenomena!) can produce the same basic features simultaneously.A difficult pill to swallow, yes, but if a general principle is so easily shown to have exception by a relatively simple and common phenomena (in that vertically successive layers can be produced by a horizontal, simultaneous event), then surely the title of "Principle" should be brought into question, and reviews conducted? Crikeys...i think it's exciting...can't wait to do some flume work myself!Hopefully the clay-settling notion (of being slow) is also not a "Principle" (though i do hear that A LOT!), as isn't even the norm...i still scratch my head at why geos keep saying it's so....it's just not....Anyhow, hopefully my general conclusions bring my specific thoughts into keeping with the theme of this thread.Edited by stewartreeve, : No reason given.

OK, firstly, someone asked, "Are you a geologist"? No, i'm not; i hope i don't seem like i am pretending to be. I'd call myself a geology enthusiast as the very best. No, my primary interests WRT geology are, at this point, the philosophical/logical aspects (stemming from my more frequent interest in the Philosophy of Science, it's Logic, etc...)Secondly, i can't respond to all this - i either don't know enough of what is being said, or i just don't have time to (more the latter, but definitely some of the former)...but i'll do my best.But do me a favour: don't just disagree with me because i am suggesting a divergent perspective (i'm not saying that people necessarily are doing that, i'm just asking that it doesn't happen ) - there are things i don't understand well and will seek to have clarified by people that know more than me - and i may also request further breakdown on assertions, etc; but there are also things i do understand well, such as arguement/logic structure, and even particle-chemical interactions.Now that i've had my cry (), back to it... You're right, it doesn't provide such a mechanism, and i think i would be at fault to suggest that it does (so i don't).And that's not the perspective by which i'm suggesting that the Principle of Superposition has some issues in light of a dynamic mechanism, which hypothetically forms successive strata....i'll express it in terms of something else i read recently (tell me if i'm on the money, or getting ideas mixed up...)Doesn't the Principle of Superposition have the following corollary/necessary implication (paraphrased):"For any given vertical coordinate in a layer, it follows that any given horizontal point is said to be deposited at the same time, and thus, has the same age" (yes? no? am i mixed up with the Principle of Original Horizontality? Don't think so, but i should ask...)Consequently, the dynamic simultaneous deposition of layers potentially contradicts at least THIS interpretation/version of the Principle of Superposition, because it is possible to have the VERTICAL points being deposited at the same time (and thus having the same "age"), instead of the horizontal points being deposited at the same time, and thus having the same age....and this is just because the layers have been formed horizontally instead of vertically. It's a 90 degree axis shift, so to speak....Logically speaking, what was considered a closed deduction now has another possible option, such that further deduction to a non-impossible conclusion must again close-off the other possibility (even if it is by a priori denial of the other possibility's validity - a valid proposition, but not a very good qulity one...)At least that is one perspective on how dynamic formation of strata could affect an axiom like Superposition...i am tired....it's 12:45am now yeah, from what i know if turbidites (which is not admittedly not grand, though i understand slurry flow fairly well...) i can't see why what i'm saying would not apply to turbidites. I've actually heard quite the opposite from geos: that flocculation is the norm, and that dispersed particle settling (true Stokian - the "ideal"?) is actually the exception. Again, it is a matter of what conditions one hypothetically invokes, and many natural conditions cause particle agglomeration (yes, yes, i will get onto a brief theory and mechanisms of particle agglomeration later, as i have been requested to do...)Edited by stewartreeve, : No reason given.

OK - i need to clarify where you're coming from here, edge.Are you saying that there are details that apparently differentiate water-formed simultaneous strata from wind-formed strata? On that i'd agree - there is boudn to be differentiating signatures...but it seems that you are suggesting that the water-formed simultaneous strata bear VERY LITTLE resemblence at all to what would be conventionally labelled wind-formed strata?Like i conceeded before - i'm not up on all the details, and how they might feature in differentiation...but also consider that any idiot (me, perhaps?) can see that there are some very significant, major similarities, and that i would think any idiot would be hesitant to dismiss them so casually...For example, the water-formed simultaneous mechanisms can produce:i) parallel stratumii) cross-beddingiii) inter-beddingiv) angles of repose for cross-beds normally/conventionally interpreted as being categorically wind-derivedWhen so many major features have their boxes ticked "yes", how can one so easily dismiss it?Given such weight, isn't when compelled to consider, then, that, if we consider the hypothesis of high-energy water-dynamics as a theoretical starting point, it is reasonably possible that the finer details that are said to differentiate the strata as "necessarily wind-blown" might infact be conceivably (and even experimentally!) explained in another light?Could you conceed that my reasoning at least has some merit?Regards.

Mind you, Cora, from what i understand of a sediment trap, it can only give an indication of the unit mass collected per unit time, not the unit distance settled of a given particle per unit time (which is settling rate, what we're talking about).As for the chemicals you've listed that can (and often are) used by engineers to induce coagulation and flocculation (though the listed chemicals are mainly primary coagulants, not primary flocculants...beside the point, yes ).

OK, first up, look at references, don't just listen to me...here is a good references i dug up for a geo acquaintance recently (there was others, but this was the best freebie!):Coagulation and flocculation in water and wastewater treatmentBy John BratbyError 404 (Not Found)!!1...i actually might buy that book - it's some of the best material on the topic i've ever read, actually Oh, and a note, someone brought up recently that i was using the notion of flocculation to disprove the Lake Shigetsu varve interpretations - i actually did not such thing...i merely corrected a comment previous to that original correction, which asserted that clays necessarily settled slowly. That's it. I did not comment on the Lake Shigetsu info at all, initially.Anyhow, for a briefer explanation from me re: how does coagulation and flocculation affect clay and silt settling rates? Under what conditions does coagulation and flocculation occur?hmmm...how to do this briefly?Ok, basics:- the smaller particles get, the more significant (surface area to volume ratio) the surface electrical layer repulsion becomes WRT the mass of the particle- i'd take a stab and say that particles < 150 micron (in very general! mining guy here!) are where we start to really see dispersive particle behaviour really start to kick in. It's the electrical field that does the particle-particle repulsion, and keeps particles "suspened'/stable in water.- the field characteristics are generally well-correlated to a quanitity known as the "Zeta Potential" - the stronger the zeta-potential, the stronger the field of charge, and the stronger the repulsive effect. Note that the electrical field can be net negative or net positive (or can be ~ zero!...more on that later...)- what is Coagulation? Basically: It is the reduction of the strength of the repulsive field surrounding the particle, such that particle-particle interaction can occur- what is flocculation? Basically: It is the agglomeration of particles with their fields of charge sufficiently reduced (now that is a geo-specific deinfition...water treatment lingo/theory generally collapses this definition of flocculation into the definition of coagulation, and redefines "flocculation" as relating to the "bridging"-type agglomeration of particles ("flocs") by a chemical-bridge - normally a high-molecular weight organic molecule, such as a synthetic polymer, but also inorganic polymers such as poly-aluminium chloride amd activated silica).- factors affecting the strength of the electrical field include (but are not necessarily limited to): i) particle-specific geo-chemistry; ii) size of the particle; iii) water chemistry- as you can gather from the above list of only three items, the range of affects is HUGE - so the answer to the question, "What conditions are conducive to coagulation and flocculation" is also HUGE if we focus on these factors...there are MANY, MANY different combinations for coagulation and flocculation of a specific particle(s)...but the best way of expressing it is with that single quantity: ZETA-POTENTIAL- when Zeta-potential is lowered from a "high" net-negative or net-positive state (ie. ZP approaches zero), particles can interact and agglomerate. A zero value is not NEEDED necessarily - just what is "needed" is the reduction of the repulsive forces between particles so that they can agglomerate. ZP ~ 0 is a good guide, though, and many particle systems have best agglomeration around this value.- some particles - like clays such as kaolinite, with their charged platelet surfaces - tend to "self-flocculate", which for us means that they will tend to agglomerate more easily, over wider ranges of water chemistry- but it is true that the most common mechanisms (in industry, as well as nature) that coagulation and flocculation occur is by the appropriate ranges of water chemistry and assistance kinetic energy (ie. mixing) being present- water chemistry: pH (or "bulk affect") is important - any fine particle system will have the "positiveness" or "negativeness" of water of a particular pH affect the zeta-potential. A given particle system will have a range (often fairly wide) where pH affects alone will, in conjunction with a little mixing, induce coagulation and flocculation- water chemistry: typically, most particle systems have a net-negative charge...thus, the presence of dissolved cations in the water are of particular interest....ie. ANY dissolved cation...sodium, potassium, calcium, iron, magnesium, aluminium, cobalt, strontium...anything....all become "coagulants" and can induce coagulation if the right concentrations are present. Similarly, over-concentration of cations can actually "re-suspend" a particle by creating a neg-popsitve charge....so it's just reversed the problem However, that normally takes a very high concentration of cations.- the coagulative potential of a cation is directly proportional to the sixth power of the valance (pretty sure that's right!)...definitely very exponential, that's for sure.- This implies that, with adequate mixing for increased chemical-particle-particle interaction, sodium(1+), for example can perform the task, but calcium(2+) is far more effective, and iron(3+ in this case) is more effective again, and vanadium (5+) is far more effective again...and the efficiency trend is exponential.- applying it briefly: sea-water should generally coagulate (high sodium(1+) concentration- a little bit of mixing goes a long way (not much required; make up for energy with time!); and is an important factor is coagulation and flocculation, and "floc" stability- someone also mentioned that making the size of the particle larger shouldn't affect it too much, as it wasn't related to density, as if this should invalidate the signficance of agglomeration to fine particle settling rates. Not so: look at the basic Stokes Equation for Terminal Velocity in a viscous fluid as a guide (laminar flow assumption, Stokes' law - Wikipedia): the terminal velocity in linearly proportional to the density of the particle, but proportional to the SQUARE of the diameter (read-in hydrodynamic diamter, as we are not dealing with spheres in the real world).- FINAL COMMENT: it is the prevalence of either favourable cation concentrations (which don't even need to be that high!), and/or favourable pHs, and abundance of natural mixing environments that assist chemical-particle-particle collisions, that makes coagulation and flocculation of fine particles (silts and clays, etc) so common in the natural world.I really hope that was at least interesting to someone! Should i at least give myself a gold star for effort? lolRegards.
Stewart

PaulK, i see your point, but i think the correction is quite trivial....perhaps i should re-phrase it as relating to the same relative or proportional point in the same layer?Nonetheless, the point is that vertically-successive strata can be formed by a simultaneous, dynamic mechanism, by HORIZONTAL progression- and said strata, if analysed "blind", would conventionally be interpreted as forming one layer after another: the lowest first, then the next, then the next, and so on, according to the normal rendering of the Principle of Superposition; whilst the truth of the matter would be that the stratum were all formed at the same time: with the "youngest" part being at the horizontal "start", and not at the vertical "start" (bottom)...This is a thought-experiment to help convey my point...Also, if people want to appeal to a particle-by-particle deposition for the dynamic scenario as still validating the general Principle of Superposition, then i'd have to remind them (and myself!) that the principle is concerned with the inter-stratum chronology - true? Thus, this appeal would reduce the necessary validity of the PoSn to only having intra-stratum relevance, instead of the inter-stratum relevance it is intended to have.I really have to stop and go to bed....thanks for your patience...Stewart

--PercyNo, it's not relevant to this discussion. The whole clay/silt settling thing was initially a tangent, a comment i made on someone else's comment, that someone else decided (kind of randomly and definitely tangentially!) that it was relevant to Lake Shigetsu - perhaps i shouldn't have said anything? I apologise - i'll happilly stop discussing the topic if no one wants to discuss it IN GENERAL any further.The Lake Shigetsu thingy is a strong point - great, i'll give you that. But i'm sure not obliged to discuss it in this thread (and i'd be silly to, given how little i know about it! Mind you, RAZD's post looks really good, and has lots of info...i'll go back to that sometime Ta)Now let me go to bed Edited by stewartreeve, : No reason given.