 So interpreting stratigraphic columns is one of the key aspects of being a stratigrapher and using the sedimentology to interpret ancient depositional environments. So we're going to take this stratigraphic column here, which is actually Cambrian in age, and we're going to use the sedimentary structures preserved in that stratigraphic column to interpret the depositional environments. So I've written out this page that describes how to do that, and it includes, as a first step, characterizing the diagnostic sedimentary structures, then developing a tentative environmental interpretation. Check that interpretation with respect to consistency with other features, and then we will in detail evaluate the vertical facies changes and apply Walther's law to test whether our environmental interpretation is consistent. So we'll go step by step through this process. So the first thing is to identify diagnostic sedimentary structures. And we have this legend here, and the ones that are pretty consistent with specific depositional environments are Hamaki cross stratification, which suggests storms, and particularly storms in standing water that have the waves plus currents. Swaley cross stratification is a version of Hamaki cross stratification, but there's more erosion on the tops of it, so both of these represent storms. And then tabular to wedge cross stratification is typical of tides. The key thing to note in the legend here is that you have lamina dipping in two different directions, not always, but sometimes, which is consistent with the herringbone cross stratification. And in this particular case, it represents tidal influences. So the first thing, we have these two sets of diagnostic textures. Cross stratification can occur in a lot of environments, so it's not specific to an environment. Shale occurs whenever the sediment, the water flow speed is low, pebbles require a high flow speed, burrows are from organisms that have time to burrow. An intra class suggests erosion within the environment and deposition of, for example, consolidated mud or slightly cemented sandstone. So none of the other ones are particularly diagnostic, but these storm deposits and the tidal influences are. So if we look over at the strat column here, we have the hammocky cross stratification throughout this area. So we can say that the strat column is influenced by storms, in standing water here. There's inter clasts, and this little wiggly line represents erosion. So there's a lot of high flow speed, you got that U for flow speed. Then we have our storms again here, and this is the swaley cross stratification. So we have storms. The trough cross stratification can be a number of different sorts of environments. We have a high flow speed again here, and storms. Again we have the trough cross stratification which is a little bit uncertain what it is. Then we have a high flow speed again at this unconformity. Then up here we have evidence of tides with the flow going back and forth in multiple directions. And then up here it's not 100% clear what the sedimentary structures are. There are a lot of inter clasts, and when they're filled in black it means that they're mud. But then if we look at our grain size down here we have medium sand. So these are sand, and the P is for pebble. So I am interpreting this as being mudstone, otherwise known as shale, but mud deposited and clasts of mud here, but of course grain size. So I'm going to also interpret this as possibly related to tides because tidal environments often have a range of flow speeds which can allow the settling of mud from suspension as well as the transport of course grain sizes. So the transport of course grains is when the tidal flows are very high and the mud settles out when it's low. And then we have an unconformity here, so a high flow speed again here. So if I use these distinctive sedimentary structures, and we can look at the change in grain size, my overall interpretation, tentative interpretation, is that the flow speed increases upward and the storms are in standing water, so this would be lake or ocean based on the storm deposits. But up here we have tides, and so we know that this needs to be in the ocean because very few lakes actually have tides. So I'm going to cross out the possible lake interpretation for the storms because the tides indicate we have an oceanic environment here. So I have a tentative interpretation that we have something that's offshore and storm influenced and then we go up into a tidal zone. There are a number of layers, like for example in here, that I don't have an interpretation for yet. So my step one was to identify these features. My step two was a tentative interpretation. Now I'm going to move into step three, which is looking for consistency with the other features. So I cleaned up the image a little bit, and we are at step three looking for consistency with other features. So if you start at the bottom, it's very fine sand down here, and storm deposits. So this is probably a pretty deep water environment, and then we have this unconformity. So I asked myself, is an unconformity, an intra class above it, is that consistent with storm deposits? And I will say that maybe there's a particularly large set of storms, and it's very common for them to cause erosion surfaces and have class at the bottom of them at the peak of the storm. So I will say that basically this is consistent with the storm environment. It will have, it represents a higher energy or higher flow speed to get these environments, and often the higher flow speed is closer to shore. So I'm going to have a tentative refinement of my interpretation as possibly closer to shore. So then we have storms again in this environment, and I should mention we should evaluate the bioturbation, and the bioturbation is common in this environment. So so far everything's consistent. We have our storm deposits and a bioturbation again, and here we have this swaly cross stratification. This is also from storms, but again higher flow, and so that is also consistent with closer to shore. We'll keep that as a tentative interpretation. So if we look at our column, it's generally getting higher energy, and we have these two indications that maybe we're getting closer to shoreline. Okay, so now we get to this trough cross stratified sand here, and this requires the grain size is fine to medium sand. So it's a higher flow speed than down below, and it has more unidirectional flow. So we have a tentative interpretation that we're getting closer to shoreline with a higher energy, and then we have the question, could this be related to being closer to shore? And the trough cross stratification can form from a current, but often irregular currents, and so one of the currents that can form near shore would be for rip current, for example, that's flowing offshore. So this is consistent with a near shore, either a rip current or possibly in a river channel, but it's consistent with a near shore environment. So this sequence suggests it's shallow and upward. Now we have an unconformity here, erosion, and we're returning to storm deposits again. So these storm deposits are again finer grained, and so this suggests possibly deeper water again. We know we have to be below sea level to get the storm deposits because they require that the standing water for the waves and the currents. Then we go back up into the same trough cross stratified facies. So we can again say, okay, is that consistent with our interpretation down here, or is there some additional information? There's a little bit of additional information right here in this black part, which again is mud, which requires a low speed to accumulate. So now we have this possible mud, we again have some bioturbation, and we have this coarser sand in these sorts of deposits. So the presence of the mud here and the sand suggests that we have variable environments. The mud might just be right at the bottom here, which suggests that maybe it's some sort of transitional environment. So I have a question here, is the mud from a separate environment? So that's something I'm going to want to test when we really work with Walther's Law. And then we're getting up here, tides in the ocean with moderately high flow speeds in different parts here. And then we have an uncomformity with pebbles and faster flow in this stone here. So this is all consistent, this environment up here, all the features are consistent with what you would see on tidal flats and in subtitle environments. So tidal flats that often have the channels, tidal channels in them, it's very common to get this suite of depositional textures. Okay, so in my evaluation I haven't found anything that's inconsistent with a tentative model or the hypothetical model where we have standing water with storms. We have some indication we're getting to shallow environments in these two trough cross stratified intervals and I'm not sure yet how they exactly fit in with the storm deposits. And then there's this tidal flat zone up here. So we did the consistency with other features combined with a vertical evaluation. And the next step then is to compare that vertical evaluation and Walther's Law. Okay, so we have our tentative interpretation and now we want to evaluate it with respect to Walther's Law. So we have an offshore environment as a hypothesis with a couple of shallower or higher energy. There's trough cross stratification near shore, back to offshore, back to near shore and then shallow marine tidal environments. So how do we test that? So the first thing we can do is if you have, there are two ways to approach this, one of which is to draw the environments that you have in your mind and see if you can trace those through the strat column on the environment or you can go vertically through the column and try to draw the environment. So I have a pretty good mental image of what I think the shoreline might look like. And so I'm going to try to draw that. So I'm going to draw a map view and so this is land up here and we have our shoreline somewhere in here and we have our ocean down here. So we have offshore storm deposits. So I'm going to say that this is below wave base, normal wave base but above storm wave base. And then maybe this little bit that shallower will be a little bit closer to the shoreline. And then we have something going on in the shoreline that produces this trough cross stratification. So one of the ways that can happen is if you have a current flowing offshore. So I'm going to say maybe we have some sort of river flowing in into the zone here and this is where we're getting our trough cross stratification. So I can draw something like this. And then we have some tidal flats over here. So I'm going to draw a set of channels in here for my tidal channels and maybe sometimes the flow moves upstream here and then I'll mark maybe an area with, this will be the high tide line and the solid one will be low tide. So this is sort of a hypothesis that's based on looking at some of the Google Earth images. And so let's test to see how this fits with our model and our environments. Okay so if Walther's law is correct we should be able to move gradationally from one environment to the next without skipping any unless there's an unconformity. So we'll start with our offshore storms. And so I should add this, so this line here would be storm wave base. So we're seeing the effects of storm in all of this. So we'll start out somewhere out here. Okay my hypothesis is that this is somewhat shallower but still basically the same environment. So maybe that's something in here so we can go from one to two for shallower. And then maybe it comes back to deeper water as we're getting more of these storms and then we think that it's shallower again. So this would be three and four. And then we need to see if we can get to something that will have the trough cross stratification. And I think I added this river so that we could get that here. So we can sort of go into this environment here. Maybe it sort of goes up more strongly influenced by the river maybe not, maybe something to test. And then we go back to an environment where we have the unconformity and the interclass which is a lot like environment too. So maybe we're going back here. There is some erosion right here. So we could be missing an environment but we can actually go back to this environment. So this would be five. This would be six. We can go back to that environment without a big change. So so far everything's consistent. Then we need to go back to the near shore environment again. So this would be seven. And so we can go back in here. And then we would be sort of have the coarser grain, some erosion into the tidal flot environment. And I haven't sorted these out in detail but the style of stratification here in the coarse grain size might actually be within a channel. So just based on the grain size I'm going to guess that eight is sort of within a channel here with mud clasts. The herringbone cross stratification with a little bit of mud in here might be pretty close to a channel in here where there's a lot of flow at an out. But it's inundated with at high tide. And then we go up into this zone here and I'm not sure what this cross stratification means but we'll say this is sort of nine. Ten could maybe sort of be anywhere in here. And then we have a bigger erosion zone which might be related to the channel here but we sort of have tidal flats on either side. But it represents to get the pebbles you need a faster flow speed which maybe our river can produce here. So in evaluating my Walther's law I can sort of go continuously, messily among these environments. So we can basically say that the interpretation of the environment is consistent with Walther's law. So the final thing we can do is check for consistency or check and interpret what happened with sea level. So what is the overall change through time? So in this zone here we went maybe shallow or a little deeper. So we can say, so if we plotted up sea level we can do it on this side of the column. So we can do low, high, relative sea level. The water depth is high initially. So the relative sea level would be high. We think maybe it gets a little bit shallower, a little deeper shallower. And then in this channel we think we're pretty close to the shoreline. And then to get the hammocky we probably go deep pretty quickly which represents this line over here. So that represents this change right here. And then we go shallower again. And then this zone is probably intertidal. So this, we don't know in detail how it's changing but the zone in here represents deposits probably that are somewhere between high and low tide. So this would be within the tide change. So based on these feces changes and tracking them back and forth across the map we can match and track the relative sea level change in this column. So just to review the processes we took, step one was to identify the diagnostic sedimentary structures. And in particular we found hammocky cross stratification and herringbone cross stratification and likely mud drapes. We used those, the evidence of storms and tides to develop a tentative environmental interpretation which was offshore to near shore. We checked the consistency of other features, especially the trough cross stratification being one of those. Then we evaluated, we did steps three and four about the same time. We looked for consistency with a vertical evaluation. Then we used that vertical evaluation to create an environment and a map of different areas where the deposits would be made to test that hypothesis using Walther's law. So this is a process that we do when we are measuring stratigraphic columns in the field. We develop these hypotheses and we look to see if we can make additional observations to test them. And we can also use it to interpret other people's stratigraphic columns like we did here.