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Michael Hudec - Evolution of the Salina del Bravo, Mexico: The Bravo Trough, Sigsbee Canopy and Perdido Fold Belt

AAPG Distinguished Lecture Series, 2018-19 Season

AAPG Distinguished Lecture Series, 2018-19 Season


A Distinguished Lecture talk given by Michael Hudec during 2018-19 AAPG DL Season. Click here for abstract.

Full Transcript

Hello. And thanks for tuning in. My name's Mike Hudec. I'm a senior research scientist at the Bureau of Economic Geology, which is a part of the University of Texas at Austin. I'm also the principal investigator for an organization called the Applied Geodynamics Laboratory, or AGL, which is an industry-funded research consortium that studies salt tectonics.

This morning, I'm going to be talking to you about an area called the Selena del Bravo, which is in northeast Mexico as part of the Gulf of Mexico. And I'll be talking a little bit about the structures that make up the Selena del Bravo Region, including the Bravo Trough, Sigsbee Canopy, and the Perdido Fold Belt, and then also a little bit about how they evolved and what they all have to do with each other.

Before beginning, I need to thank both TGS and CGG for agreeing to let me use the seismic data that I'm going to be showing in this presentation, and also the members of the Applied Geodynamics Laboratory, who funded the research.

To begin with, let's talk about where the Selena del Bravo Region is. It's in the northwestern Gulf of Mexico. Now, the northwestern Gulf of Mexico is an interesting place for a couple of reasons. First of all, from a plate tectonics perspective, there is a big change in the style of opening of the Gulf of Mexico that goes on in that area. In the eastern parts of the Gulf of Mexico, most of the spreading center is spreading ridges separated by very short segments of transform faults. However, as you go further to the west in the basin, the style of opening changes. And when you get into the western part of the Gulf of Mexico, you're looking at much more of a transform-dominated system with very short spreading centers. So you're looking at much more strike-slip deformation in the western part of the basin.

The second, when you get into the Northwestern Gulf of Mexico, the width of the salt basin changes. The salt basin is about 500 miles wide in the central parts of the northern Gulf of Mexico. But as you go west, the basin gets narrower and narrower and also steeper and steeper. So we would expect some changes in style as we get closer to the west.

And then finally, as you get towards the western part of the Gulf of Mexico, you're getting closer to the Pacific margin, and you're starting to see some of the compressional structures. And those are the blue lines on the image that you're seeing there. And so you're starting to get caught up in the edges of some of the compressional plate deformation that's going on in the area. So you might expect to see some differences in the western part of the Gulf of Mexico as compared to the rest of the basin.

We'll start off by just sort of going through in a little more detail exactly where the Selena del Bravo is, and what are the main structures that formed there. So the Selena del Bravo is the continental slope that's just south of the US-Mexico border. So you start in offshore Texas, and you go south, and you're in the Selena del Bravo. If we wanted to look at a seismic line, showing some of the key structural elements across the Selena del Bravo, the line that you're looking at goes on the left, from roughly the shelf edge, out on to the continental rise on the right end of the section. And we can see four main sets of structures that we're going to be talking about in the basin.

First of all, starting furthest up dip, you have the Bravo trough. The Bravo trough is very thick accumulation of Cenozoic sediment. It's fairly tightly folded, and the seismic imaging is not very good, leading us to suspect that mostly it's filled with shale that's been tightly compressed and deformed.

Moving a little bit further outboard, what we see is the Sigsbee salt canopy. The Sigsbee salt canopy is fed mostly from feeders at it's up-dip end. However, there are a few feeders within the canopy as well. And it flows seaward, out over the next main structural province, which is the Perdido fold belt. The Perdido fold belt is detached on the low end salt, down at the bottom, and its series of compressional folds, with a few very minor thrust faults, but mostly folds, sitting at the seaward end of the system.

Now, underneath the Perdido fold belt, and at the seaward end of the Perdido fold belt, you have the BAHA high. The BAHA high is a structural high in the base of salt. You can see we're ramping up about 2 kilometers on to the BAHA high. And what this seismic line doesn't show, but the next one will, is that you drop back down about 1 to 2 kilometers off the other side of it. So it is a major basement high at the down dip end of the system.

Now, what do those provinces all have to do with one another? Well, starting with the BAHA high, you can see that the Perdido fold belt lies above the BAHA high and on the up-dip side. And as we'll be discussing as this presentation goes on, we're going to argue that the BAHA high formed a buttress, against which the Perdido fold belt formed as sediments slid seaward down on the salt detachment.

Looking further up-dip, if we look at the seaward end of the Bravo trough, we see a weld that is connecting up to the Sigsbee salt canopy. In places that weld still has some salt in it, in which case it's not a weld, but in most places along its length, what you're looking at is a weld connecting the Bravo trough to the Sigsbee salt canopy.

Now, the relationship between the Sigsbee salt canopy and the underlying Perdido fold belt is kind of interesting. In places, like is shown with the arrow pointing at it, it's very clear that the Perdido fold belt folds the base of the Sigsbee salt canopy. In other places, what you see is that the structures of the Perdido fold belt are unconformably overlain by the canopy.

So we're seeing mutually cross-cutting relationships, suggesting that the Perdido fold belt and the emplacement of the Sigsbee salt canopy are roughly synchronous. Now, synchronous at what time? The age of the sediments immediately under the Sigsbee salt canopy suggests that canopy emplacement and Perdido fold belt formation are mostly Oligocenan Age, extending on into the Miocene as well. So we're looking at an Oligo-Miocine event.

Let's talk a little bit more about the Bravo trough. This is another seismic line in which we're looking at the Bravo trough on the left-hand side. And one of the things that's interesting to see in that area is that the Mesozoic section, which is the blue on there, pinches out underneath the Bravo trough. And the overlying Cenozoic section expands greatly into the Bravo trough. And in fact, the Mesozoic is thin or missing under most of the Bravo trough, suggesting to us that there was actually a salt diapir there during the time of its formation. So the Bravo trough had, as a precursor, the Bravo diapir, onto which the Mesozoic section thinned.

So what do these all look like in map view? So this is a map of the Selena del Bravo and surrounding areas. And what we can see is several of the different structural trends that are important in the area. First in yellow, we have the BAHA high at the seaward end of the system, which extends all the way from the southern end of the salt basin, down at the bottom of the slide, up into US waters. Now overlying that, and to the left of it, is the Perdido fold belt, which are those lines. Those lines mark the axes of the anticlines in the Perdido fold belt. And then finally, up dip of that, in the blue, is the Bravo trough. So the Bravo trough, Perdido fold belt, and BAHA high all run roughly parallel to one another along the length of the continental margin.

So from here, we're going to be starting to address the question of, well, what do they all have to do to each other? But first, before we get into that, let's talk about what exactly the fill inside the Bravo trough looks like. We're going to be looking at a seismic line running from north to south down the axis of the Bravo trough.

Now, at the north end of this, around the area where it shows the one, actually, up in US waters, we do have one good deep well that goes into the Bravo trough. And what the Bravo trough shows is it's filled mostly with shale. And the well penetrated a thick Miocene section, and then more than 10,000 feet of Oligocene without ever getting out of the bottom of the Oligocene.

So we think that most of the fill of the Bravo trough is Oligo-Miocene in age. Now if that rings a bell, the age of the fill, Oligo-Miocene, is the same as the age of both the Sigsbee salt canopy and the Perdido fold belt. So all of the major structures in this part of the world seem to be roughly the same age.

So the question then comes, well, the salt was deposited in this area back in the Jurassic. And so for more than 100 million years, the area sat relatively inertly. Not much happened in the region. And then in Oligo-Miocene, everything happened at once. So what happened in the Oligo-Miocene to transform this and create all of these structures all at once?

Inside the Bravo trough you see that the fill is shingled from north to south. I've labeled them as 1, 2, 3. So the sediments become progressively younger to the south within the basin. The Bravo trough is named for the Rio Bravo. But the shingled nature of the fill suggests that there's probably going to be more than one river involved in filling this up. It suggests that really there's a little bit more going on than we currently know about in terms of Oligocene sediment transport systems in this part of the Gulf of Mexico.

OK. So those are the players. Now, let's talk about what happened-- how they all worked and why everything happened in the Oligo-Miocene and what was the source of the timing and the cause of deformation in the Selena del Bravo Region.

All right. Let's look again at a map of the system. And this time, we will focus on the deformation that lies to the west of the Selena del Bravo Region. You can see that, even today, there's a pretty good looking mountain belt off to the west. And those black lines are all structures in the Cordilleran Orogen, a compressional orogen related to subduction of the Farallon plate beneath western Mexico.

And this deformation in those mountains started in the late Cretaceous. The structures to the west are the oldest. And then as you go to the east, across those mountains, the deformation gets progressively younger and younger. And at its easternmost limit, you're looking at Eocene. So late Cretaceous to Eocene deformation forming the mountains.

Now, if we're looking for, in the Selena del Bravo Region, what impact did all that compression off to the west have, we're going to focus on an area called the Burgos Basin, which is just up dip of the Selena del Bravo Region, and ask ourselves what are the first things that we see in the Burgos Basin that tell us something about what's going on in the mountains off to the west.

So we're going to look at a stratigraphic cross-section across the Burgos Basin. And what we see is during Eocene time we get the first hints that something major is going on off to the west. We have a couple of major unconformities that cut down eastward across the Burgos Basin. And above each of those unconformities is a major prograding sequence. So we're starting to get sediment supply from the growing mountains off to the west beginning in Eocene time. Now, beyond that, we also see some interesting tilting in the Burgos Basin.

If we look at a map of surface exposures in the Burgos Basin, we can see that sediments get progressively older going westward toward the mountains. Along the coast, we see Miocene units exposed at the surface, then getting older and older, all the way back to Paleocene along the western margin of the basin. This geometry suggests that the basin has been uplifted and tilted toward the Gulf of Mexico.

So the next question is, when did that tilting occur? Well, there has been considerable work on uplift in the mountains, just to the west of the Burgos Basin. And what you can see in those areas is that the uplift is oldest to the south and gets progressively younger to the north. But if you look just to the west of the Burgos Basin, we've got uplift beginning around 30 million years ago, just to the west of the Burgos Basin.

Now, remember that the actual compressional deformation ended in the Eocene. 30 million years is Oligocene, which means that the uplift and tilting is post-orogenic. The shortening had already stopped by the time the uplift began.

So how much uplift was there? What kind of unroofing and uplift and tilting do we have going on just to the west? This is a plot showing the burial history of rocks to the west of the Burgos Basin and points south. And what you can see is that we reached a maximum burial depth here and started uplifting about 30 million years ago, for this particular sample. This is constrained by potassium-argon dating, fluid inclusions, and apatite fission track-dating. And at about 30 million years ago, we started uplifting and we're continuing to uplift all the way to the present.

So uplift is still going on in the region, uplift and tilting. What's particularly interesting is the magnitude of the uplift. Putting together all the samples regionally, you're looking at about 5 to 7 kilometers of uplift and erosion that have gone on just to the west of the Selena del Bravo Region.

So that's a lot of erosion and a lot of sediments that were supplied by the mountains to the west. And we would argue that the final resting place of a lot of those sediments is in the Bravo trough, further down dip. So what we've got going on in the early part of the Cenozoic is major sedimentation sourced from the mountains to the west. We're looking at tilting.

And so then the question becomes, well, there's a lot going on tectonically at the time, so how did that play into building the Bravo trough, Sigsbee salt canopy, and Perdido fold belt? Well, if you look what's updip of the Bravo trough, you see onshore there a lot of little blue lines, OK? Those are normal faults. So we're looking, when we tilted the basin and added all those sediments, we evidently destabilized the margin. And everything started to slide seaward. And those are the breakaway normal faults.

So at first glance, you'd say, well, OK, that makes this a fairly simple system. What happens is you throw in a lot of sediment, you tilt the margin, and you have breakaway extension updip, and the Perdido fold belt is the congressional toe of that system. Well, it turns out to be not quite that simple. Because if you look at a seismic line from onshore in the Burgos Basin, you see that the normal faults are not detached down on the salt layer. In fact, they're detached on a unit called the Mendez shale, which is at the top of the Cretaceous.

Now, the Perdido fold belt downdip is detached on the salt layer, which is down here. So if we're going to connect this updip extension to the downdip shortening in the Perdido fold belt, we have to find some place where the extension can ramp down from the Mendez shale on to the deeper salt detachment.

OK. Well, let's move a little bit further outboard. Now we're on the shelf, so just a little bit downdip from the last seismic line. And what we see on the shelf is actually even a little more complicated. We start to have shale diapirism, which are the little red blobs that you're seeing in the right end of the section. And you're getting multiple detachment levels. Not all of these normal faults make it down to the Mendez shale. Many of them are detaching in the Oligocene and the Miocene.

So we have multiple detachments being fed from onshore, none of which are making it down to the salt layer. So somehow, if we're going to explain the origin of the Perdido fold belt, we're going to have to get all of this translation ramped down onto the basal salt detachment.

You can see the same story a little bit more regionally here. On this seismic line, we see both some of the update extension, with the deeper detachment fault coming downslope and, we would argue, ramping down onto the salt detachment in the area of the Bravo trough.

There are also a number of shallower detachments up in here that don't make it down onto the deep salt layer, but instead go into feeding shortening within the Bravo trough. So some of the shortening that is sourced by the extension updip is actually being absorbed inside the Bravo trough and give an explanation for the complexity of some of the deformation there. And some of it is actually ramping down onto the deeper detachment and, we would argue, going out to feed deformation in the Perdido fold belt.

So in summary of our evolutionary model, this is the story that we suggest is what's going on. So back at the end of the Mesozoic, not that much had happened yet. The Mesozoic was a fairly quiet time. Most of what happened was building the Bravo diapir. So we would argue, at the updip end of the deeper salt basin, the salt basin that starts in about the center of the section, we had one big diapir, the Bravo diapir, which was a major salt wall that ran up and down the length of most of the basin.

Now, if you remember from the map how big the Bravo trough is, it's about 400 kilometers long by 100 kilometers wide. That would be the biggest salt diapir in the world by quite a lot. We suspect that actually the Bravo diapir had a series of relays in it and was more than one diapir and that subsequent mapping will probably show some of the additional complexities of the system. But for now, let's just treat it like it's one big diapir.

So at the end of the Mesozoic, there it sat, the Bravo diapir. Now, in the early parts of the Cenozoic, what you had down in the bottom half of the image was you had all the uplift and tilting started. So the present day is the configuration that we see down on the bottom. And there are a couple of interesting things about that.

First of all the sediments being sourced from the mountains that lie to the west come in and they fill the Bravo trough. And what happens is the salt that was in the Bravo trough gets squeezed up and out into the Sigsbee salt canopy, which lies just downdip. So we would argue that the Bravo diapir is actually the source of most of the salt that is presently in the Sigsbee canopy in this part of the Gulf of Mexico.

Second, the tilting that goes on destabilizes the margin, and everything starts sliding downhill. So the series of shallower detachments feed into the Bravo trough and go into some of the shortening there. But the deeper detachment along the Mendez shale, actually comes down to the updip end of the Bravo trough, ramps down to the deeper salt layer there, and then goes out and causes the deformation out in the Perdido fold belt.

So our argument is, is that the reason why the basin got destabilized in the Oligo-Miocene is that that's when the effects of the shortening and uplift to the west started to be felt in the basin. The compressional deformation further updip sourced all the sediments that filled the Bravo trough and expelled salt into the Sigsbee canopy. And the post-orogenic uplift in the region is what tilted everything and caused the sliding down slope which made the Perdido fold belt.

So that's an interesting model. And it's kind of plausible. But it's also a little bit complicated, because there has to be a whole lot that's happening all at once. We have to have tilting and sedimentation and extension and everything ramping down onto the salt detachment. And so although it's kind of a neat model, how do we know if it's physically plausible that all that could be happening at the same time? Well, what we resolved to do was to try to test it with a physical model, which is what I'm going to show you next.

So the setup of the physical model looks like this. We started off with a salt basin, which is shown in red on the top cross section. And we vacuumed off the cover over one little strip in the center of the model. And that caused salt to flow in from both sides and build the equivalent of the Bravo diapir. And so we build the Bravo diapir until it reaches the surface. So we've got our big, pre-existing Bravo diapir.

Then we put in another shallow layer which is shown in purple right there, which is going to be the equivalent of the Mendez shale. So that is the shallower detachment. And then we start prograding sediments, shown in that little wedge there, across our Mendez shale.

Now, if the experiment works, what we're expecting to see is that that prograding wedge will start extending and stretching, detached on the Mendez shale. You will get sliding along the Mendez shale until we reach the Bravo diapir. And then that sliding will ramp down onto the basal salt layer and go ahead and build the Perdido fold belt out to the right end of the model. At the same time, continued progradation is going to eventually reach the area of the Bravo diapir, is going to expel salt out from the Bravo diapir, creating the equivalent of the Sigsbee salt canopy further down slope. So let's see if that's actually what happened when we made the model.

What you're looking at now is an overhead view on the left-hand side and an underside view on the right-hand side. The overhead view is just a camera mounted on the ceiling. The underside view is actually a camera mounted on the floor, looking up. Now the underside of our experimental rig is actually clear plastic. So you can look up at the bottom of the model and watch it evolve. You can see in the underside view the little label that says salt wall in the middle of it, that's our Bravo diapir. So I'm going to be going back and forth a little bit, talking about what's going on.

On the overhead view, what you're looking at in the blue, on the left side, that's our Mendez shale, OK? And what you're going to see when the movie starts is you're going to see a series of colors being prograded across that. You'll see sort of quick changes of color, which is the new sediment wedges, each one which is a different color, prograding across that Mendez shale. So let's start the animation.

And so now you're seeing progradation. And almost immediately, you're seeing all that clear stuff extruding in the overhead view, out from in front of the Bravo diapir. So salt in the Bravo diapir is being expelled out. You're looking at the growth of the Sigsbee canopy. Now, if we look at the underside view, what you're seeing is shortening to the right of the Bravo diapir. That's actually the Perdido fold belt forming.

And at this point, you're also seeing some orange coming into view down at the bottom of the Bravo diapir. That is the Bravo trough. That is the sediments in the Bravo trough sinking down. You're looking at just about all of the salt has been expelled. And off to the right, what we've seen is some shortening going on. That panel off to the right has shortened quite considerably. And so we have made the Perdido fold belt.

Well, so that's the overhead view. Let's look at the cross sections. Now, before we start the animation, I should explain what you're looking at a little bit. In the upper right, you have the picture of the overhead view at the very end of the model. There is a white line down at the bottom of that which shows the location of the cross section which is down at the bottom of the image. Now, what's going to happen when we start the animation is that that white line is going to sweep northward across the picture. And we're going to do a fly-through of the model. So we're going to keep changing sections and look at new sections every time.

So let's start the animation. You can see the white line moving. And we're flying through the model. So let's just stop right here for a minute. And you can see right in the middle what we've got is a big syncline, almost exactly in the middle of the image. It's a big syncline with orange and yellow sediment sunk all the way down to the bottom. That is the Bravo trough. That is the former location of the Bravo diapir. Salt has now been expelled out from there and is in this little thin skim at the top of the model off to the right. That is the Sigsbee salt canopy.

Also noticed, at the right end, detached on the deeper salt level, we have the Perdido fold belt. You see a big set of salt cord folds down there. And at the updip end of the model, down along the Mendez shale detachment, you can see a little couple of triangular diapirs. Those are extensional structures. And that is the shallow extension detached on the Mendez shale.

So in short, the model seems to have worked. We get extension detached up on the Mendez shale. It ramps down to the deeper salt level, which is what forms the Perdido fold belt out in front. And at the same time, we have sediments sinking into the Bravo diapir to form the Bravo trough and formation of the Sigsbee salt canopy.

So let's move on and do a comparison between the seismic data on top and the physical model in the center and our conceptual model down at the bottom. So in the seismic, we see the location of the Bravo trough, seismically fairly incoherent, mostly shale filled, intensely deformed inside of it. Then we see the same structure in the physical model, which is the big sediment-filled syncline sinking down to the bottom. And there it is in the conceptual model as well.

So we get the Bravo trough in all three models. We get the Sigsbee salt canopy in the seismic, the physical model, and the conceptual model. And then finally, at the seaward end of the system, we have the Perdido fold belt on seismic model and conceptual model.

So we'd have to say that the physical model seems to be a success. Now, that doesn't prove that the model is right. But it does prove that it's physically reasonable, that we're not trying to call on some process that can't possibly work. So at this point, we feel that the conceptual model that we've developed offers a reasonable explanation for what seems to be going on in the Selena del Bravo Region.

Well, at this point in almost any kind of scientific endeavor, you have to stop and say, well, so what? I mean, it's kind of neat that we have a model. But what are the implications of this model? And what kind of insight does it give us as to larger questions in the Gulf of Mexico?

So first of all, let's talk about some of the structures that we see at the north end of the Bravo trough, where it crosses into US waters. Now, this area shown by the arrow on the map is notoriously difficult for seismic imaging in the Gulf of Mexico. And in fact, the top seismic line is a line across that area. And you can see that underneath the salt canopy, you see a whole lot of nothing. And there has been enormous effort in both seismic acquisition and processing spent on trying to get a better image out of this area.

What this work and this mapping suggests is that what's underneath the salt in this area is the Bravo trough, which is made largely of shale without much internal seismic impedance and is, in addition, very tightly deformed and extremely steep dips and not a whole lot of continuity, lots of faulting going on. So it is entirely possible that the effort that has been going on in seismic acquisition and processing is to some extent wasted because you're already seeing what's there. What's there is not really imageable. There's not a lot of sand. There's not a lot of impedance. And it's very, very tightly deformed.

So actually, the seismic imaging in this area may be quite good. And the unfortunate fact is there's just not a lot down there to image in this area. So that's one implication of this work.

Now furthermore, to more regional scale, there is an interesting comparison that you can make between the Perdido fold belt, which is the one we've been looking at in the Selena del Bravo Region, and looking further south across on the other side of the basin, the compressional structures in the Bay of Campeche.

Now, these are conjugate margins. The Perdido fold belt part of the basin restores against the Bay of Campeche. And both of them are in deep water. And they're both compressional fold belts. But there, the similarities stop. They're actually quite different in a lot of ways.

So let's talk a little bit about what we've got down in the Bay of Campeche. So here's a zoom in showing topography in the Bay of Campeche. And what you can see, that the Bay of Campeche is actually in the foreland of the Sierra de Chiapas, which is a big basement involved thrust system also related to tectonics along the Western edge of Mexico, and that the thrust faults come up toward the surface in that area and then detach on the salt layer and then slide out on the salt, so that the shortening in the Bay of Campeche is actually directly tied to plate compression, subduction along the western edge of Mexico.

If we look in at a map in detail of the structures in the Bay of Campeche, all the black and blue little lines that we're seeing in there are compressional folds, faults, pinched off diapirs, over-thrust diapirs, all sorts of different compressional structures. You can see they make a broadly arcuate shape. And there are a whole lot of them across pretty much the whole basin.

So in this area, you're looking at more than 100 kilometers of shortening, in all likelihood, in comparison with 10 kilometers or less in the Perdido fold belt. So there is roughly an order of magnitude, more shortening going on in the Bay of Campeche than there is in the Perdido fold belt.

So what we say is that, yes, they're both in deep water. Yes, they're both on sort of passive margins, although you can make an argument about the Bay of Campeche. But that's where the similarities stop. The Perdido fold belt, which is shown on the top illustration, is at the toe of a gravity slide which is coming off the eastern side of post-orogenic uplift related to all the plate collision. So it's kind of indirectly tied to plate margin effects on the western margin of Mexico. It's a gravity slide.

On the other hand, the Bay of Campeche is directly linked to plate collision, that in fact the basement structures-- we've got the Sierra de Chiapas at the left end of the section. The thrusting comes up out of the basement, detaches on the salt, and then moves directly forward from there. So you're looking at a direct manifestation of plate shortening in the Bay of Campeche. So two really very different congressional provinces on opposite sides of the basin.

So in summary, the Selena del Bravo Region is very interesting. It's got a set of major structures in deep water. And those are the BAHA high, Perdido fold belt, Sigsbee salt canopy, and Bravo trough. And we think that all of those provinces are tied to the influx of sedimentation and tilting that happened as a result of congressional deformation in central Mexico, the Cordilleran orogeny, and that the sedimentation loaded the Bravo diapir, expelled salt out into the Sigsbee canopy.

And the sedimentation plus tilting destabilized the margin edge and caused extension at the updip end of the margin, all sliding downhill. Some of that extension was absorbed by shortening within the Bravo trough. Some of it went all the way out into the Perdido fold belt, depending on the detachment level. And that the Perdido fold belt actually has a markedly different style than the shortening we see in the Bay of Campeche on the other side of the basin.

So it's an interesting area. It's an area about which really very little is known, outside of Mexican oil companies. They've had access to most of the data. And as it's starting to come to light that other geologists outside of Mexico can look at it, it's a fascinating province that teaches us a lot about processes that are going on in the basin.

So I hope you've enjoyed your introduction to the geology in this part of the world. I'd like to thank both AAPG and the AAPG Foundation for making the Distinguished Lecture Series a possibility. And I look forward to seeing you all at sometime in the future. Thank you.

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Explorer Foundation Update

Now available for streaming, the fourth video presentation in the AAPG Distinguished Lecture program features Michael Hudec and his presentation, Evolution of the Salina del Bravo, Mexico: The Bravo Trough, Sigsbee Canopy and Perdido Fold Belt.

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Explorer Foundation Update

AAPG’s historic Distinguished Lecture program has undergone a revolutionary transformation aimed at extending the program’s accessibility, audience and reach.

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Comments (1)

On Dr Michael Hudec video
The Dr. Michael Hudec 's video of the distinguish lecture program is quite clear and enlightening. The reconstruction movie that he presents based upon physical modelling, depicts and support the ideas of some 1980's Pemex geoscientists. The mechanism of regional uplift, starting in late Oligocene and extended to present, is clue to understand the development of what he calls Bravo Trough, Canopy and Perdido Fault and Thrust Belt provinces. Although the regional uplift, as he acknowledges, is well documented via fission tracks studies, there is still controversy regarding the geodynamic origin of such phenomenon. I remember that we invoked mechanisms such as: buoyancy of old crust, flexural uplift, and regional (isostatically induced) uplift, among others, to explain it. This is, and will be, a topic of research for many years to come. Anyway, Dr. Hudec's investigation presented in the video is a significant contribution to figure out, not only the salt tectonic setting, but also the regional geologic evolution of the NW Gulf of Mexico. As the humongous amount of seismic data collected in the south of the border Gulf of Mexico, is being analyzed and assimilated, a better understanding of the geology and petroleum system of such a unique and complex region of the world is guaranteed. Many thanks Dr. Hudec, Guillermo Perez Cruz
2/6/2019 4:00:35 PM

Distinguished Lecturer


Michael Hudec

Senior Research Scientist, Bureau of Economic Geology

University of Texas

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  • 50019 The Salina del Bravo region, on the continental slope just south of the Texas border, is dominated by four structures. From landward to seaward: the Bravo trough, Sigsbee Canopy, Perdido fold belt, and BAHA high. The Bravo trough lies beneath the updip part of the slope, and is characterized by a thick, intensely folded Tertiary section beneath which the Mesozoic section is thin or absent. The Bravo trough runs for roughly 400 km along strike, and is at least 40 km wide, with the west edge lying beyond the limits of our dataset. The downdip end of the Bravo trough is connected to the Sigsbee canopy by a feeder or weld. The Sigsbee canopy lies almost entirely seaward of the Bravo trough, and in most places overlies the Perdido fold belt. In many places the Perdido fold belt folds the base of the Sigsbee canopy. Elsewhere, Perdido folds are truncated beneath an unconformity on which the canopy is emplaced. At the seaward end of the system is the BAHA high, named for the first well drilled in it. The BAHA high is a structural high in the base of salt, with 1-2 km of relief in most places. Like the Bravo trough, it runs over 400 km along strike. The Perdido fold belt lies on top of or updip of the BAHA high. Evolution of the Salina del Bravo, Mexico: The Bravo Trough, Sigsbee Canopy and Perdido Fold Belt
    Evolution of the Salina del Bravo, Mexico: The Bravo Trough, Sigsbee Canopy and Perdido Fold Belt


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