 It's my very, very pleasure to introduce our next speaker of the series. Professor Ronald Olson of the Department of Environmental Science and Policy Management, which we usually love to talk about at home, is going to talk to us today about the Autocommer Desert in Chile and an archeological area that will be a great interest to make people in the room. And I'm just going to turn this over to you right away because I want to hear what you have to say. Alright. Thank you. ESPM, and I am a soil scientist and earth scientist, and so I have been working in Chile for 15 years, and my reason for going there didn't have anything to do with archeology, and I have to say that for years I kind of tried to ignore things that had to do with current stuff because I didn't want to get sidetracked from working on what I went down there to do originally, which was to, I got started with a NASA funding to use the Autocommer Desert as an earth analog for Mars. And I've still been kind of doing that, and here I have one of my colleagues, Bill Dietrich, who tagged along with me a few times and is actually studying Mars now. So it is a very important earth location for understanding the chronic effects over millions of years of extreme eridity on the environment. And I've done projects to look at the long term, when the desert became the desert, back in the Miocene or Pliocene, we've looked at the effect of these, of eridity on the geochemistry of soils and what that can tell us about past climate and also inform us about what the history of Mars is. But in the last five or six years we were looking at big scale questions on the evolution of the desert, the erosion, and we were driving back and forth across landscapes like you see in this picture here, which we knew essentially must be a dry lake bed, but we had initially not too much interest in exploring when it was a lake and its history and so forth. This is actually, if you look across this landscape, there's this road leading out across this dried lake bed and it's really, it's about this thick of rock hard sodium chloride. The lake, it's just a cemented lake, a bumpy road going across this lake bed. We thought it was an interesting thing but I never thought, as we went along, that it would eventually be relevant to thinking about archeological questions. And so I'm going to give you a little overview today of part of my grad students' PhD project who is here right now, Marco Pfeiffer is right here in the middle of the room. This is part of, one part of Marco's PhD dissertation. And then I'll talk about some new work that I've started with my colleagues, Claudio Lattore and Caligaro Centoro from Chile and their students postdocs and colleagues to about things linking up our observations on the paleo-hydrology and the connection to recent developments and discoveries in archeology in the region. So one of the, I guess there's kind of a, I guess we're at the point in our studies and research in South America now where we're sort of at a point where a lot of the old myths and sort of predisposed ideas are starting to fade away. And one myth, well it's not a myth, it's really true and I'll talk about this today, ongoing work on lakes and new archeology. So the myths are that the desert is lifeless. Well it truly is today but the buried underneath this is what I'm going to talk about is that there's subtle oscillations in maybe not the climate of the desert but the climate of the nearby Andes that are feeding water sporadically and periodically into the desert that change have probably greatly changed the character of what we see today on very short geological time scales. The other thing is 10 years ago and I'll show you a paper that sort of set out what was known about a decade ago. This is considered, the desert was considered to be an archeological free zone that people had moved up into the Altiplano of the Andes. They had inhabited the coast but had largely avoided this interior and a lot of this is now sort of melting and fading away and we're developing I think a more complicated and complex perspective of the peopleing of South America. Now it's hard not to be totally impressed by how dry it is when you're there. This is, I was out there a year ago with Marco and my Chilean colleagues. This is typical of the desert, it's an absolute desert in biological terms. There's no plants, there's not enough water to support plants unless there's groundwater here and there that's providing a little oasis. Very few insects, there's a few that are surprisingly here and there but essentially an almost abiotic environment and it's hard not to be impressed when you're out there and when you know that there's archeological sites out there to wonder how in the world this ever was inhabitable or habitable. This is another photo of my Chilean colleagues making a mess in the desert driving to an archeological site. The landscape in addition to being dry is covered with a mantle of windblown dust and sulfate salt and it's just so dry that this stuff doesn't dissolve or disappear and you drive across this landscape gets stuck in the dust and it's an incredibly inhospitable environment and then while you're walking around in all this stuff you find things like this. This is a ball my colleagues found. They suggested it was part of a toy or play thing used by the people that lived there several thousand years ago. Walk across the landscape you find these lithic materials and even more surprising when you're out in the midst of this absolute desert out you stumble across some things and you dig it up and it's a tree trunk. So there's sort of this dichotomy of this incredible oridity today and yet a perspective that things were different not too long ago and it's been the fun part of this sort of recent work that I've done that sort of is unveiling sort of the unique things that have happened out here in the last 10,000 to 12,000 years. So this is sort of where the state of archeology knowledge about the desert was when I first went down there in 2001 this came out in 2002 it's written by the famous Chilean archeologist Nunez and he and his colleagues at that point outlined the known archeological sites in this part of Chile in South America and they were all concentrated up here in what are essentially the Andes the Altiplano, the high plateau that is truly actually not a desert there's actually plants, there's rainfall, snowfall but it's pretty dry, pretty cold but it showed the distribution of known archeological sites and I put this red line in here to essentially show that there was nothing shown on the map for what is the low elevation dry desert region and one of the things that Bill and Marco and I have found is we were just wandering geologists and we stumbled on all of these red stars our places where we had found either lithic chipping, abandoned shelters or some combination thereof that reflected archeological activity so this was to me kind of a revelation and it was sort of a curiosity more than anything it took us a long time to actually get up the energy and overcome the inertia to bring in or get involved with archeologists to explore this a little bit more and that's what I'll be talking about today the thing that really drew us in is the discovery of the site called Mani it's on the Quebrada Mani it's a paleolithic site that my colleagues Claudio Lattori and Caligaro Centoro have uncovered and so that led into the, it sort of led to us tying into my geo hydrology work into their archeology so they've created sort of a more updated perspective on archeology in this part of South America they've divided this up into three zones, a coastal zone this yellow area is the true absolute desert region of the Atacama and then the stuff to the right is sort of the Altiplano each little dot represents an archeological site and you can see they're all sort of converging on dates between 10 and 12,000 years and the Quebrada Mani which they've worked on the oldest date associated with archeological information is about 12,800 years and so this is pushing back human occupation pretty far in time but it's part of this overall pattern that's starting to emerge of occupation in the desert and later in this talk I'll just give you a little update on quite an extensive area of activity that we're just starting to explore much further south it's also right in the belt of hypereridity so the Mani site, here they are excavating it it's basically in the middle of this absolute desert it's on an ancient or a Miocene river terrace that's sort of stranded and it's been cut around by a subsequent incision of the streams coming off the Andes when they did the survey they walked across the site they found all sorts of lithics scattered along the surface and then adjacent to it to the south is a modern drainage and to the north is a sort of Pleistocene drainage that's in there and also not shown on here, there's all sorts of post 2000 year old agricultural fields, canals, drainage systems so there was an extensive sort of late Holocene period of stream activity that sort of brought in the Neolithic sort of and the agriculturalists laid in the game but this is the Mani site, the late Pleistocene site they showed the artifacts scattered over the surface what they found on the surface were these these are the points that were just laying on the surface and I find it interesting about humans so around Mani this is just maybe 100 meters across, 200 meters across and down here must have been thousands or hundreds at least of farmers and I asked Caligaro if he found any sort of farmer debris on top of that terrace and he said no, apparently nobody either went up there or they didn't bring any stuff up with them but it's a baffling to me that there could have been people here for hundreds of thousands of years farming and they didn't leave anything up on the ridge but nonetheless they left all the Paleolithic people left this stuff they found gastropods, spear tips, camelid bones with tool marks in it and a lot of lithic products around there so it's quite an extensive occupation and then the one site that they really excavated in detail they found some evidence here of a hearth, hearth or some sort of fire pit with evidence of heating of the material and some burning so this was at least a semi-occupied area for some period of time and the evidence suggests that around it on both sides was a riparian zone that now very dry channel on both sides was fed by runoff from the Andes and must have been a very luxuriant and rich and vibrant biotic zone that provided the resources to the people that were living here so people did traverse and inhabit the desert but the other thing that's part of what we're working on here is to unravel a lot more about the hydrological history and what the overall scope of the desert looked like maybe at the end of the Pleistocene so here is the Monysite right here it's a long stream called the Corbrata Mani that drains or heads up in the pre-Andean area there's been work done between the Chileans and some folks from Cornell that have looked at terraces and biotic remains and some of these streams coming out of the Andes and they get a variety of ages in the early Pleistocene, early Holocene and then there's sort of some very late Holocene evidence of stream activity but what it sort of begs the question is what was the whole region like during this period we have a hint now that water was moving through these corridors but what was going on in the basins and this is a map from Claudio's paper showing three large salt-covered basins now and so what we're going to do now is take a look at what we're learning about the history of these salt-covered basins the other thing that's emerged from all the work that other people have done not so much that what we've accomplished so far is that there's been evidence for two big pluvial periods one between 18,000 and maybe 14,000 and then from 13,000 down to about 10,000 these are called Cape I and II events central Andean pluvial episode events Cape II is the one that corresponds to the earliest archaeological record the data that my colleagues have around this area clump into these two areas and we'll see that lake evidence also seems to suggest that these areas were filled with water or partially filled with water at various times during Cape I and Cape II events and then there was a later period in the late Holocene that also probably had significant water so this is sort of an accidental thing as I mentioned my colleague Arjun Heimseth and I were focused on big-scale stuff and either just through touristy sort of things that we're doing or just wandering around and just looking at things we were sort of sucked into this sort of late quaternary history of the area and we've sort of stumbled onto dates for pluvial episodes for the Salar Pentados, Bella Vista, and Yamara to the south and I'll talk a little bit about some of the things we've seen and some of the dates that we've generated on this so this is part of Marco's PhD dissertation and so the more overall scope that Marco's working on we've looked at a lot of outcrops along these lakes the miners, one thing about Chile is there's salt mining just about everywhere so there's excavation holes in all sorts of locations so we've looked at a lot of outcrops, done some logging of these outcrops we're developing a radiocarbon database so we have more samples to date as well and one of the things that we're going to do is calculate the extent and volume of these lakes and sort of outline the periphery to sort of inform us more about where to look for other archeological settlements and inform the future archeological excavations and the one challenging thing that Marco's trying to work on now is to calculate changes in the regional ground flow in geological models that would cause the salars to fill so this is part of a series of steps that are leading into an overall and richer history of this area well the Salar Pintados is I guess for me as a just as a tourist it's an interesting archeological area it's now site of a national park that has been set up to sort of preserve all the amazing array of geoglyphs that are found on the nearby hills and the Salar in Spanish essentially is the term for a salt-covered flat basin or lakebed largely the boundary between the salars right about where we're standing here and then there's some gravelly beach area in the background and then these hills in the back where people over time have created these amazing geoglyphs if you look down on it from Google Earth this is a scale bar up there of 150 meters you can kind of see the geoglyphs on the hill this is a rough boundary between the basin and the geoglyphs and then there's a salt-covered dry lakebed in the background when we were there a few years ago they were just building a new visitor center and they built a walkway out onto the flat and they dug a trench all the way through it which opened up the stratigraphy and to our surprise we found basically what appears to be freshwater marl underneath all this salt so what you see here is since the dates we have on this are about 11,000 years and they are calibrated to calendar years so 11,200 or so years old so basically since that was a freshwater environment the water table has dropped there's been capillary movement of water and solutes and the evaporation has basically left this thick rock-hard zone of sodium chloride on the surface so that's that rugged looking topography in the background but then underneath it there's a zone of fine-grained soil with a lot of riselists from plants and that gave us some ages of about 11,100 below that are some moral layers about very well fine-grained almost pure calcium carbonate gave us ages of just over 11,000 years so this was quite a different environment and the interesting thing is this is within the time frame of known human occupation so this could have been an area for resources for people then and so it sort of allows us to extrapolate the periphery of this wetland or small lake area and project where there might be the outlines of this area to look for future occupations down at Bella Vista there's a lot of trenching that's gone on for salt mining purposes and they opened up a number of really cool things around shorelines with plants and so forth this is sort of in the middle of the basin if you will these lakes were probably only a few meters thick at their thickest point during the late quaternary so they wouldn't be extensive or large lakes but there's quite a history here there's some dipping very sorted and imbricated gravels that look like shoreline layers and that is a thick zone of diatomaceous material that we have one dated sample from this from a carbonate in a wave feature right below the salt crust that's 25,000 years old and the diatoms Marco has been working with the folks down in Chile and it's a mix of fresh to saltwater species that are in there so there's a variety of environments the diatoms but including freshwater environments that were in these lake sediments also we found in pentados we found shells these are sands that have in them these freshwater shells that we've dated these came out about 16,500 years so they reflect a very different environment than what we see here today one of the features that strike you when you drive across these dry lake beds are these humpy mounds that are found across the landscape and what these are appear to be coppice dunes around the periphery of these ancient lakes and marshlands the wind was blowing sand around you can find modern analogs of this tamarugo trees are basically a mesquite sort of species nowadays live in or you can find these associated with these coppice dunes and if you drive through some of these road cuts through these dunes again there's the ubiquitous sodium chloride crust over it but occasionally you can find trunks or branches of these fossil mesquite trees and in this particular out cut crop we dated it and it was about 12,700 years old so again there's sort of pieces of the puzzle in the solar Bella Vista we have sort of basin deposits we have shoreline plants and so forth we found and then we have information on the ages and nature of these sort of coppice dunes that were surrounding the area I should say near the in another lake basin around these coppice dunes we found a lot of artifacts hammers and tools that appear that this would have been an area for people to exploit or at least utilize but we haven't done any archaeological excavation sort of walks through this area yet but this might be an area we want to take a look at in the future okay and then the final salar the salar Yamara this was beyond sort of our interest in this as a paleo hydrology question I just had a student Kari Finstad who finished her PhD on basically the geochemistry and geohydrology of what forms these crusts how fast they form and also the sub part of her project she's just finishing is she's working we were working with Jill Banfield in our department to look at the genetic make up of the microorganisms that live in this sodium chloride it's actually another interesting sort of contradiction in the sense that this is the driest place on earth this is an area of pure sodium chloride and yet the most vibrant life in this entire region is to be found in the salt crusts that are exposed to the atmosphere basically what's happening at night is the salt absorbs water becomes essentially a brine and some very salt tolerant cyanobacteria and microbial communities basically are thriving well thriving is I guess a relative word but within this salt and so the greatest biodiversity is in what would seem to be at face value the most inhospitable environment and to illustrate how inhospitable it is there's Marco using a jackhammer as we try to excavate a pit into this to get at the stratigraphy but anyway in this one there was a marl down at the base gave us 15,000 years and then up at the top there's some sand with organic layered sandy material with some organics that came in a little over 12,000 so again this gives us a perspective of the hydrological history of this area so putting it together I'm starting to try to get myself around the idea of what would this area have looked like at the end of the Pleistocene if you look around the landscape probably the local rainfall didn't change much so it would still be this absolute desert first with you know vibrant riparian zones and then sort of temporal or periodic lakes and marshlands in all these what are now salt covered salt flats so it's a very different setting that the early inhabitants and people that came to South America explored and ran across up there there's this Cape 1 event, Cape 2 event there's our lakes, Pintados Belivista, Yamara basically we have dates that suggest there was wet conditions for both of those periods so probably both of these lake systems and solar systems were responding to the regional climate and presumably then would provide a very different habitat for the early inhabitants so this has already led to us thinking about where to look for archaeology quite differently so after driving around last summer and showing Caligaro and Claudio the work that we've done we started to think about some other places that hadn't been explored before one of them is a cave well you can only find this in Chile a cave and a mountain appear sodium chloride and so we think that well there's evidence that suggests that this cave formed when the region has been cutting down for 10 million years the river system was about at this high this is probably a dissolution cave that formed early in the Pleistocene there's actually river gravels in the cave I found this summer that I hadn't recognized before but we went in to see if there was any archaeological evidence so this is what it looks like into the entrance again this is all salt a cave of salt here's Marco and my colleagues down here and around you can see the these are actually river gravels down here and then we found a fish bone in there so this is sort of opening up where and when people came through there and it's sort of an exciting period to work with archaeologists to show them what we're finding and then think about what that might mean for people in occupation of the area but I want to give you a little overview of this summer the project was for me to show the archaeologists some of the stuff that we've found Bill and I and Marco over the last decade and so we moved south south of Antifagasta into what was considered to be a very large area without much archaeology although that is changing as time goes on one thing that's been discovered is some sites found up in the some lakes near sort of at sort of the pre-Andian area recently and then there's some sites that have been found along the coast both near Antifagasta and further south but the area where we've been finding a lot of stuff was right out sort of right in the heart of this hyperarid zone in the Atacama we don't have a name for it the nearest mountains called Buena Vista so that's kind of what we're sticking with for the moment and I don't know what is considered to be an archaeological site but I'll show you what we found so 10 years ago a colleague of mine from NASA was studying he was looking for basalt outcrops in the Atacama desert which are hard to find actually and he wanted to do this because Mars has made a basalt and he wanted to look at a true Mars analog so he talked to some geologists and they showed him where this outcrop was and then I went out to look at his soil pit that he had dug and I was more struck by all the artifacts I found around me and so I went back there this summer and it's quite an extensive belt of little outcrops of basalt that seemed to have jasper veins and the people paleolithic people were coming there to basically use this as a lithic manufacturing site so what you commonly see when you're driving around are these piles of rocks probably shelters that have fallen down this is one of Bill's photos from another area but very similar to what we were looking at this is another area of some of these shelters that have been built and then stuff in the background here's Claudio I found one of these sites and they're dating right now this abalone shell that was on the surface so that'll give us some sense of when people were there and this is the kind of thing you see here but also all up and down the Atacama Desert you see the lithic chippings and then you see these rounded beach cobbles that people brought from the coast inland and then used them as hammers to chip the lithics and a lot of these have big dents and indentations on the edge due to hammering and they're sort of dropped there and left from their excavations I took a video once this is up north near Pasagua but I was at the coast where the water was coming in and sort of rolling these cobbles along so this is sort of the environment where you get these but one of the things about this new area that we're exploring is that there's no there's no stream right next to these lakesites there's some paleo streams about 30-40 kilometers away so unlike Mani which had a stream running right by it it begs the question how did they get there how did they sustain themselves and so forth so it's 90 miles, 90 kilometers from the ocean and then the other thing is what did they survive on when they got there so we're looking at some places in the interior of this desert now that people haven't thought of in terms of lake quaternary support of human habitation but I'm starting to think that indeed there might be evidence that this was a very different area as well probably at the turn of the Pleistocene-Holocene transition this is an area called Young Eye it's had a long history of incision there's a dry lake bed out there now a week there this summer and so digging trenches below getting below the salt crust on the surface it's a whole different geological world there's a big thick marl layer below that is sandy deposits probably maybe along a shoreline they're non-calcareous so it was an environment that was producing calcium carbonate which is a very different geochemical condition today apparently it looks like in some sort of water where this marl was accumulating and concentrating eventually it dried up and it got covered with salt like many places do there about 30 kilometers from that lithic site is a vast probably it's been a wet land off and on for millions of years it's a long stream that comes out of the Andes and I explored this over a couple of days in the recent this is the most recent stratigraphic section what was striking is on the surface there were remnants fossil partly decomposed plant material all over the surface and lots of these little still woody material from the previous wetland plants that were there so we're in the process of dating both the plants and the marl and stuff that's underneath this there's even outcrops of this is a thick calcium carbonate layer that probably formed in a lake below it is peat and then there's fossilized or at least mineralized plant roots and plant material below it so there's below the surface of all this salt and dust again is apparently a very vibrant and unique and complex sort of late quaternary history of pluvial episodes we're in the process of dating so I have all these samples I'm just waiting hopefully for a National Geographic proposal to get funded so I can date them so this is where we're sort of working now in terms of this is sort of an interesting find all these lithic sites manufacturing sites the question is were there more permanent settlements in the area what were the water resources available for these people and when this all happened and ultimately I guess it brings up the bigger question of putting together sort of this big human history of the Atacama desert and sort of sort of lifting I guess some of the perspectives on how arid the region has been over time there's been oscillations due to changes in the Andes that bring resources in and people have certainly exploited this and utilized this I'm going to end with just this figure that came out in Nature earlier this year by folks down at Stanford where they put together this map of known archaeological sites over time periods and to me this is you know as a geologist this is very striking how so early in human occupation of the western hemisphere the people had succeeded in occupying everything from the driest place on earth to the wettest place on earth and had spread over this area in such a short time and so it's interesting to be a part of understanding what's going on in the driest place and that's kind of where my work is heading over the next few years in Chile so that's all I have today but I'll be happy to answer any questions you have in the Salar we have a date the raw radio carbon date is 6800 so there's something there was water there maybe calendar years 7000 or something years ago so I guess that's my follow-up question that 5 7000 years ago did you have any surface water in this region well partly it's an artifact of what we look for to or what we've been able to discuss so we haven't we've looked now a little we spent a couple of seasons now looking more specifically at the recent history and oh that's what we've found so far I don't know if there's other evidence that we haven't stumbled on yet open to maybe other things being uncovered but that's more or less what we've found there's yeah so we have I think things well the other thing is it had to have dried up both in all these Salars in order to allow that salt crust to form so that salt crust provides some framework into the amount of time that these are dead so given the rates of evaporation and everything the radiocarbon ages along with the major rates we have seem to suggest you know it's been pretty dry for the last 7 to 8 thousand years is there some kind of bacteria that can be used to complete the salt crust like adding carbon to it? yeah it makes so I didn't like the salt crust with the green cyanobacteria but the salt crust does have again carbon in it probably not a very fast growing ecosystem but the interesting thing is carbon sensors in these crust and even though the air temperature goes through a daily cycle of maybe 20% humidity it's 90% the crust in a lot of these areas never go below the point where the salt is liquid by so these crusts are basically brine almost 100% of the time of the year so that if there's light microbes can have any cyanobacteria can focus on this size so Bob have you tried to reconstruct what these were really like? you know with all sorts of different kinds of fish and either a sink in the head or these are fairly salt you know just what you guys know Marco's right just give a summary of the pollen filaments so what the data suggests is that there's no tuition in the rates of recharge to the lakes so probably they went to brine lakes salty to more freshwater lakes what we have found so far like the better sink of freshwater are those shells that you can find today around the El Cidano region in the lakes there but we don't know what we think though is that the marshals were pretty far like pretty wide extent and they support vegetation and in that vegetation probably also supports some mammals, big mammals there are some very old studies that they have found some mammals in the region and probably they support mammals and that was the the resource for the people there I was wondering if there's any kind of regional variable that you're about 20 degrees south there so if you know if you could talk about it not core specifically to look at lake history but as Marco and I were talking about there's been a lot of coring deep to understand the hydrology and there's been some oil wells and stuff that actually have been drilled to see if there's oil but there's not specifically coring of these pliers to look for environmental history I think well there's kind of an unspoken idea that I think well by a lot of us we maybe didn't pay attention to it accordingly but these were ancient things that they couldn't have possibly been very active recently I never really gave a little thought and I guess early on but I didn't really ponder it too deeply and then a lot of people a lot of some of the patrons they've been coming out of the biology in this large city like the ancient they've been seeing and stuff so we're starting to get to the point now where we know that they're young and now maybe the next phase we go in and do these sort of focused projects to look at the I noticed that on one of your sections there was a section that was labeled phytolith analysis can you talk a little bit more about what's going on what is that mark on your face so that's actually from the chain that we looked at that section well mostly we found like some grasses and the first events like the first movement that talk a lot like a marshland and then it tends toward more mischievous trees so it tells about trend to our identification but I'm asking would you say it's just like what you find in the Alta Toronto because actually two years ago we did a vegetation study on the shores of both Titicaca and also the pole which is now dry but when we were there it was wet and wet her obviously and we have a whole range of taxa from that very salty dry dry lake very similar to what you might be getting hints at well the species that we found there mostly we correlate with species that are along the Rio Loa which is the main favor that the only terrain surface water that you find in the Alta Toronto and they're pretty similar so you can use a picture of the Loa riparian some sort of sense of lake shores that's what we have really and actually the people that already feed and is that prosopis still growing there yeah I had a question I was just curious about the farming terraces that you were finding around that site and I mean what kind of archaeological evidence do you see when they're from or what period where are they getting the water from the water came from the riparian zone reactivated again during the late Holocene and there's diversion canals that move the water out of the main channel distributed across the landscape small fields, little distributary canals and since my focus was on the earlier part but they have a couple of papers that have been written on the agricultural settlement and they in some places you can actually still see the corn stalk standing in place because it's so dry there's color cobs even popcorn so quite and if you look at it on Google Earth it's a very extensive area of fields and manipulation landscapes that suggest at least to me not an archaeologist but it was a pretty vibrant human occupation that inhabited that area as well as other streams probably had similar things in them as well so it got a lot better again than in the late Holocene so the first wave where the paleolithic people then as a hiatus after those plurial events at least who knows we'll probably get surprised again about archaeological evidence so far and then sort of just late Holocene episode before that dried up and people dispersed as a result of the drying of the region