Walking through river
NPR/NGS Radio Expeditions
25 Mar 1995
- Union Choco
- 8.13809 -77.61566
- SONY TCD-D7
- Sennheiser MKH 30
- Sennheiser ME 40
Stereo=1; Decoded MS stereo; Sennheiser MKH40 Cardioid Mid Mic and MKH30 Bidirectional Side Mic
PANAMA - Darien Logs
DAT #2 - Union Choco - Day Hike
- Stereo pair, MS, Sennheiser 40 and a 30
Day 2 -
#1Preparing for the Day's hike
#2 - 0:02:29-FX Crossing the stream..... boot steps on the rocks .....
(mic handling A right channel NG)
03:35 - just stream ambi - plus steam crossing chatter
04:57 - FX - stream plus birds - (right still seems murky - NG )
05:33 - FX - stream plus birds (G) - 7:27
08:05 - (G) FX - crossing the river - splashing through. plunks til 8:30 (when Tony starts to talk and interrupts the recording.)
9: 19 - ambience going down the hill - then river ambi and still for forest
ambi plus stream on the right, plus some birds
11:02 (G) FX - Bird; stops at 12:40
[Good river forest ambi 9:19- 12:40]
12:50 More forest river ambi - bug flies by at the beginning.... scientists digging in the background- [GI general Ambi for forest river, scientists at work. faint talking...... then some walking in the river .... Embera kids laughing - ends at 15: 16
[Good river ambi with scientists at work -1250 - 15:16]
Interview with Biff in the forest:
15:23 -AC: How did you catch this thing Biff?
BB - We have this cheap little Radio Shack amplifier which we put leads from in the water, and I go around and listen ...... FX .... the fish is making that sound....and these fish hunt at night, and they come out and make use that electrical field to find prey and also to find one another in courtship--like a bat does? -- Similar, but they're using an electrical signal and waiting for that field to be broken as opposed to active sonar which is pinging off and on...... hear that, (FX -16:08) isn't that wild.... off in.... so we just go around when we're looking for these guys. with this little detector and when we hear 'em. we scoop with the net, and 50% of the time we pick one up ...
AC - That fish is 8" long. a little brown narrow fish. Do you recognize that fish?
BB Ya, it's a knife fish called hypeopomis. And actually you can recognize it just by the noise it makes...there are about four of these in this area.... and by the electrical signal, you can classify it to species, just the way Elizabeth does with bats without ever seeing it ..........
AC: hope he's going to filet it ...
BB - In the Amazon they eat these things ..... This guy is interesting because it his a distribution in Panama that if you were just to look at the species you would say it was not interesting .... it's widespread and typically in biogeography, or biodiversity, when you look at a widespread species that crosses areas of endemism, you're like ho-hum, kind of boring, but genetically when you look at this, it's very different in different regions of Panama and in fact, between here and Bocas del Toro, the divergence is very, very large, and suggests a very early colonization event that would have happened prior to the rise of the Isthmus, so it's got this idiosyncratic distribution which opens all sorts of speculation about how animals moved in this area at about the time the Isthmus was rising or slightly beforehand.
AC: Do you find this on both sides of the Isthmus?
BB: You do find it on both sides of the Isthmus.
AC: And are they different species?
BB: No, they're t he same species, which until genetics was applied to it, it was just sort of a boring no-hum species that had this widespread distribution, it's only genetics that's told us it's really quite different in different places.
AC: Why hasn't it radiated into different species?
BB: That's a good question; it's kind of the perennial question as to why some things diverge morphologically and some don't, and it's usually those things that diverge morphologically that we recognize as species. Because most of us use morphological methods to look at that, but as Jeremy would tell you, you have a lot of things in the record that go through these long periods of morphological stasis, they just don't change unless there's pressure on them to form new body plans they just sort of stick there, but in this case probably the reason that electrically we can distinguish them is because they use them in courtship and when they split in to different sides of the Isthmus. or one end of the Isthmus to the other, and are out of contact with one another, very slight random changes can be amplified over time into things that we can distinguish as different, and genetically, that's the same case.....you get these genes and over time they just accumulate differences that may not be at all important for the organism to make its daily living, but in fact are very useful to us to say ya they've been diverged for a very long time...whether you call them species after, that ..... well ..... [Jeremy starts to talk off mic] ........ l9:40
20:04: I'm Eldredge Bermingham, or "Biff" Bermingham, as most people call me, and I'm a molecular evolutionist who works with STRI and has a particular interest in historical biogeography and using patterns of genetic variation across widely distributed species to learn some thing about the history of earth-earth history..... so what we are particularly interested in is using these freshwater fishes to see if we can develop or reconstruct the historical development .... the geographical development of Panama....and it's particularly interesting for fresh water fishes, because Panama was a bridge when it formed for terrestrial organisms moving primarily from South America into Central America .... there are some examples of the reverse flow ... .. but Panama is particularly interesting, because fish like this have a completely South American distribution, you only find them in Panama .... a little into Costa Rica ..... then they cut off, so it's interesting to watch what 's happened as the landscape's formed over the last 3 million years...and how the fish have diversified as they've encountered this new landscape. (21:18)
FX - short ambi from the scene with Biff - 21:55-22:06
[*Note: 20:04 - 21:18 - good with Biff]
[Note for Ambience: NG = No Good, Do not use; G = OK; VG = Very Good; E= Excellent]
[Tony tells stories]
(OK. but not great unless want to hear people talking) FX - crossing the river with people talking in the background
26:20 [NG] FX - walking down the river - just Leo - mic handling
27:00 [G] More walking in the river ambi ...gets good @27:30
[*VG 27:30 - 28:33 FX - walking in the river ambi. no mic handling]
[*VG 29:00 - 30:27 FX Then walking on a spit of land and then goes right into the river again]
30:54 FX - facing the rapids - Good but not very full or rich, just OK til 32:35
[32:35 Alex notes on tape: river bottom is sandy in places, and other places is covered with small round stones that are covered with a slippery mud]
33:50 [VGl Approach the scientists at work along the river...they've taken out their hammers...... Jeremy talks about doing an orientation .....
34:14 - 34:59 [VG] slogging through the water and along through the sand
35:57 TC: (sitting down along the river back for orientation interview.)
TC: This is the geological map of the region that we've done so far .... and as you can see we've come down the Chucunaque up the Tuira to this point on the Tuira - Union Choco, and then this river that's going up to the north, northeast is the Yappe which is too shallow to take the boat up, so we've been walking on a path that intersects those curves in the river, and we're somewhere up here .... The disadvantage of doing what we've done is that I do not know exactly where we are on this river, so we'll solve that in two ways: one is, Biff has with him a global positioning system. and by use of that it'll lock onto 4 satellites and tell us where we are in latitude and longitude, and then we can plot that point on this river: and then secondly, as we work our way down the river looking for fossiliferous outcrops,
I nil1 roughly measure the length of the reach and the orientation with a compass, and I'll do a rough and ready survey of the river, such that when we get back I can map it out 011 myself on a piece of paper and overlay it on the map, and we will know exactly where we've been, am1 we will know exactly each location for am- fossiliferous deposit we get ...... (37: 17)
**35:57 - 37:17 - Tony Coates describing where the group is and location of fossil deposits.
**37: 20 I'm Tony Coates, I'm a geologist with the Smithsonian's Tropical Research Institute (STRI), and this is part of a larger project called the Paleontology Project, which involves my colleague Jeremy Jackson, and several other scientists who are scattered around the world, Peter Jung, who is the Director of the Basel Natural History Museum, Laurie Collins, who is at the University of Michigan in Ann Arbor, others.... at US Geological Survey... plus others....
38:06 TC: And what we are doing today is a routine survey of a river that we know from previous evidence might have fossils of the age and the kind that we are interested in. and we know that because there are collections from the 1920s of mollusks from this river. It doesn't say where in the river it is, and so we have to take pot luck .... start as high up in the river as we can and work our way systematically down, hoping that those deposits are exposed and we can collect them. [38:44]
AC: There's something about this river that relates to that earlier collection? . .
38:54 TC: Well, the river is one of a number of rivers that run north, south across the Isthmus and that are tributaries of the main artery, the TWO main arteries, the Chucunaque, and the Tuira River, and the beauty of those for us is that the biologists on the expedition want to replicate their samples, so each river we now know from the geological map we've been evolving runs at right angles to the lines of strata, and so each time we go up one of these rivers, it crosses the sequence of rocks that cover the time that we're interested in. and in each of those rivers. we have a chance of finding a replicate sample of a given period of time in the past. and if any systematic and quantitative biology is to be done with this stuff. we need adequate samples and we need replicated samples, and different rivers are a way to replicate. The Yappe is in a perfect position to be one of these rivers. [40:09]
AC: What kinds of things are you looking for as you going up and down and looking at the bank of the river?
**TC: 40:15 Because we are in the tropics, the region is deeply weathered and so it's very difficult to find rocks that haven't been completely altered. The one place we have a hope of finding that are in these fast running rivers that slash a wound across the Isthmus and expose bedrock that is continuously being eroded and therefore chemically relatively unaltered. In those sediments are fossils made of calcium carbonate, and they are very well preserved when we find them in this very fresh exposures. So What we will be doing down this river is systematically covering each of the reaches and going around each of the bends to look for exposures of fresh sediment that contain fossils. From that we can extract a history of marine life of us to 15 million years ago in this part of the world. [41:17]
AC: Physically, what are your clues .....
TC: We're looking for first of all stratification, so that I can take with my compass measurements on the beds that orient them in space. Since just as in an archaeological dig, the beds that are on top are younger than the beds that are underneath, I want to know whether we're going up towards younger and younger rocks, so the biologists who are going to work on the bivalves or the other kinds of fossils will know these are samples from this stratum, and samples from strata down the river are younger. So the expedition devolves into two phases, one finding the rocks, orienting them in space and stacking them in chronological order; the second phase is to take information contained in those sediments whether it be
paleomagnetic recordings or fossils that are useful for dating, and date the age at which each of the strata were formed; and then thirdly, extracting the fossils and looking at the biological evolution. so we're looking for stratification, we're looking for ways in which I can sequence the rocks. [42:34]
AC: I'm a layman ..... what are the physical signs you are looking for?
42:45 TC: Most of the rocks in this part of the world are derived from erosion of the volcanic chain that is higher up. Those rocks tend to be composed of very ordinary minerals like feldspar and black minerals like mica ...and sometimes quartz....they are eroded and dumped into the rivers, the rivers carry it to the sea, and of course much of this area was at the time that it was being deposited, under the sea. there was a large oceanic connection between what is now Central America and Colombia and we look for sediments that are fresh. You need a good eye t o tell that you're looking at sediments that were formed a long time versus the current alluvium of the river. and the way you tell that is that the alluvium is very soft. it's still got it's moisture content, has a particular arrangement in terraces relative to the river, whereas these are indurated, already become a hardened sandstone, and they're bent, they've been tilted, have an orientation that is not horizontal to the river........ etc.... [44: 10]
44:11 TC - The sediments that we're looking for are grayish blue ... when they're fresh, and they turn rusty brown when they're not: so we're looking to find nice grayish blue fresh sediment that is already slightly indurated into strata and oriented in regular plains. [44:33]
44:35 : AC: Jeremy -- This is a map ....
J J: What don't we start with this ..... Why don't we start at the beginning. What I'm doing trying to do is I'm trying to reconstruct the history of life in the seas in the seas over the past 10- 15 million years in this part of the world. And the reason this part of the world is interesting to me is because there was this great experiment of the formation of the Isthmus and changing environmental conditions and so it provides a natural experiment for asking how organisms respond to those changes.
If you go to the beach today, and you walk along a beach, it's obvious that the environment changes from place to place, so you can imagine that if you had a fossil beach, and you happened to find one little place that was preserved, and you collected the shells that were in that place, you would have one very small sample of a much larger situation that existed ..... so what this map shows is a basin of deposition with sources on either side and sediments accumulating and they lie more or less in a straight line like this, and you can think simplistically that there was a coastline somewhere along here, and because this is relatively undeformed and every thing goes straight like this, all these different rivers as Tony said are crossing through different age sediments that lay parallel lo a shoreline ..... so for me I can walk along these rivers as a paleoecologist doing what a modern ecologist might do which is to take samples of what the biota was like at different points along that shoreline at any particular time in the past represented by these rocks .... so that this is one minor sampling event traveling across this Rio Yappe, sampling what fauna may have been preserved here as opposed to all these other places we've been which also cross this same unit. And as you go from river to river, to river, even though the age is the same and the environment is roughly the same, you find very different fossils because of slight differences in environmental conditions. And so when I say how can I describe the biota of this red unit in the past I don't base it just on one river. I base it on samples from a dozen different rivers, and it's the summation of all those different samples collected over several years which then institutes a single point of diversity in a calculation. And it's really this ability to sample on this kind of scale that distinguishes what we're doing from anything that's been done before in this region. I'll show you later how important this sampling is in the sense that we constantly ask ourselves how many specimens have we looked at and how many taxa have we found. And if we had a good sample, if we really knew what existed in the past, then when we went out and found more and more specimens we wouldn't find any more taxa ..... After 10 years of work and 100,000 specimens we haven't come close to sampling the diversity that used to exist there. And our collection is already much much larger than any that were ever made before. So this is one little replicate sample in a sampling program for one basin going through about 7 million years of time and the accumulation of data on the composition of the biota in this general sampling region. [48:35]
AC: How much area is covered here (map)
TC: ..... 40 by 40... that would be 1,600 square kilometers, and that's going up to this river .......
JJ - the diagonal length of basin available to sample is roughly 100 kilometers..... perhaps a dozen rivers to check .................... (more re. other basins .....)
TC: really constrained to the rivers .....
AC: How far inland?
TC: From the north coast 40-45 kilometers.... mountains in between.... Cordillera San Blas....
50:53 -JJ: The other thing about this Basin that's really important is that the older rocks in this basin were deposited when there was a very strong flow connection between the Atlantic and the Pacific. The youngest rocks in this basin were deposited when that connection bas almost entirely broken.... so one is going through time and through ever increasing formation of a barrier between the two oceans....
TC: In fact some of these sediments.... the green one here which would be 5 or 10 million years older than the rock we're sitting on.... the ocean would have been 2,000 meters deep right here, and there would have been no land in sight so this is a very young and recently uplifted part of the Isthmus, and we're very close to perhaps one of the last marine corridors to connect the Pacific with the Caribbean. [51:58J
AC: We've walked 3 hours this morning.... now what are we going to be doing?
52:08 JJ: We're going to be looking for deposits of the type Tony was talking about which are primary and hopefully unaltered, and recording the kind of sediments observed and looking for fossils in them....and look for micro fossils to date the sediments, and looking for macro fossils of the type I'm interested in terms of characterizing the larger fauna I'm interested in.
AC: How common is it for you to find fossils?
JJ: Depends on the river.... sediment here is coarse.... best stuff is probably above us. Today might be a bit of a bust, Really good material is fine grained, because fine grained material is tighter packed.... it has more clay ... water can't penetrate it as easily, and the preservation of the fossils is vastly superior. This stuff is very coarse, and there are ghosts of fossils in this material.... indicating was once a rich fauna.... leached away...
53:3b TC: I'm sort of in charge of a stage that precedes Jeremy's activity. Jeremy is interested in replicating these samples, but he also needs to be dead sure that he's replicating samples of the same age. For that he depends on me getting the sequence of rocks right, and then each of the layers in that sequence dated precisely so that when he gets a sample from the Yappe and compares it to (other rivers), he can trust me when I say this sample here is the same age as this sample here....... So he has to replicate in space to get spatial variety and changes in environment at a given time. but what he also needs to know is comparing temporal apples with temporal apples and not comparing a 5 million year old fauna with a 4 million year old fauna... ....for that we need to take an outcrop such as we can see here that's got a sequence of strata in it. I will measure it to orient it in space so we can plot the geometry of the strata and hence calculate which rocks are going younger, which older, then we'll extract from each of those sequences samples. 100 grams of fine grained material.....contained in those samples will be tiny calcified organisms that are former members of the plankton, some float near the surface, some buried in the mud ..... some studied by oil companies ..... around the world ..... Second thing to do when have a continuous sequence...bring in Don McNeil - drill a hole, and extract a core every single meter of that sequence, using the orientation of that core in space, would determine, determines earth's magnetic field.... sometimes the field would be normal in its polarity.... sometimes the polarity is reversed... and by getting a sequence of normal, normal, reverse, reverse, and overlaying it on the dates he's got from the fossils, he can even more precisely nail down the exact time of deposition ...So when we've done that process, we can then give to Jeremy a sequence of rock's on a map like this which allows him to overlay the biological information with some confidence. [56:36]
56:36 JJ: When Wendell Woodrin came through here on a donkey and a canoe ¿Axel Oslon, he could distinguish two or three time periods by looking at the shells..... the reason it's worth going to all this trouble... if you want to understand cause and effect and be able to say conditions changed in a particular way and therefore biota changed in response. you have to be very sure that the environmental change you're describing and the biological change really were coincident with each other...and that refinement in age dating down below one million year confidence requires this enormous increase in effort.... and this is really the first attempt to try to achieve that refinement in a tropical American marine paleontological setting - coastal. Deep-sea people have been doing it for a long time. So, sounds like an enormous amount of effort for a relatively small refinement, but in terms of going beyond saying that's the way it was, to saying well, we think the reason it happened is because of this or that....... requires all I his extra time and dating.... so he tells me where I am in space and time and if I don't know that I can't do anything......... [58:53]
59:00 TC: So what we'll do here now is just roughly measure this section and collect what we can from it for micro samples for dating.... and then move down river looking for one of these rich and diverse macro fauna.... so if we're lucky...... if not, try another river........... time for a swim.....
10 times more possibility of finding micro samples......
1:02:10 Ambience with talking....... and swimming .......