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oh all right as they already said my

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name is Gabriella March some of you saw

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me last night and this is basically the

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same talk only longer and with some

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numbers so oh and I don't have the

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answer so anyway let's jump right in

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thanks to my collaborators I definitely

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could not have done this alone and my

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sources of funding so here we go so I

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studied carbonate cemented conglomerates

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this is what they look like it looks a

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lot like concrete it's pretty boring

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it's hard to get away from because I

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always see concrete so I'm always

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thinking about my rocks and what I've

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hypothesized is that if you can't find

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organic material or living organisms

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which is possible that we may not be

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able to find most immediately on Mars

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maybe you can use isotopes and the

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mineralogy sort of a detailed

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investigation to prove the or service

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evidence that life existed so it'd be

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started the study we thought we'd find

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negative carbon isotopes we thought we'd

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find dramatic variability in the

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isotopes and in the mineralogy on a fine

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scale and then mineralogical

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heterogeneity so we'll get into that all

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right so I investigated rocks from two

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different creaks adobe creek and del

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Puerto Creek this is what they look like

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they're pretty low flow in the

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wintertime which is when I went and

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collected rocks it looks like somebody

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dumped a whole bunch of concrete into

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the rivers and I want to point out that

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there is ooh that there are microbial

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mats all over the place so a note for

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you biologists out there so this is the

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i found these creeks run through the

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dell printer over your light adobe creek

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runs this way into del puerto rican whr

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creek runs runs down this is downstream

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and so those are my sampling sites

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they're actually pretty close together

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but could come from very distinct

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watersheds and this is where the del

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Puerto feel is located so it's in

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California it's part of the California

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coast range Oh feel light system so

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there's lots of ophiolites up and down

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the coast and it's pretty close to San

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Francisco and the closest big city is

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Livermore so that's where we stay in

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hotels okay so it's a no fee alight and

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I use that word and some of you may not

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know what that means so we use

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ophiolites as Mars analog

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I don't think this has been mentioned

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before but basically Mars's crust which

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is kind of what I'm investigating it's

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an analog for Mars Mars Chris never got

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differentiated so it's mostly may thick

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and ultramafic rocks which is the same

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thing we find on earth in the ocean

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crust so we have may fick and ultramafic

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rocks in the ocean crust we have

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continental crust which is high in

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aluminum silicon things like that so if

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we want a study on Mars analog we really

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need that ocean crust which obviously is

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underwater which is an issue but luckily

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at subduction zones when the plate the

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ocean krutz gets abducted under the

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continental crust sometimes a chunk of

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that ocean crust and even sometimes a

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bit of the mantle gets shoved up onto

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the land which is what we call an Ohio

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light sweet and those may thicken

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ultramafic rocks are sort of a

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compositional analog for Mars so there's

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a lot of interest in the chemistry of

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the water that runs through there and as

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an analog for Mars so it's pretty

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exciting so just to give you some

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context as to why you should even care

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carbonates are definitely on Mars

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they've identified those and there are

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definitely conglomerates on Mars those

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are my rocks right here these are Mars

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rocks just saying they look a little

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like okay so dolomite the carbonate that

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cement this conglomerate together one of

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them one of the carbonates in there is

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called dolomite and for those of you

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that don't know what that is it's

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dolomite been a problem for geologists

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because forever we could not get it to

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precipitate out of solution in the lab

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and poor dr. land did this for 32 years

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in perfect conditions and it never

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happened but then we found out later

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that we add microbes to the mix and some

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sort of microbial mediation goes on it's

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not like a coral or a shell that that a

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a clam is making its it's some sort of

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indirect influence and there's a lot of

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theories as to how that happens it might

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just be sort of cellular material in the

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area they might we're not

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sure what they do but we say that they

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might they mediate the formation of the

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dolomites and they are necessary in

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order for dolomite to form in these

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types of environments at low

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temperatures all right so I'm going to

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talk a lot about magnesium content in

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the data and this is important because

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calcite is just pure calcium with

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carbonate whereas dolomite is calcium

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and magnesium with carbonate and it's a

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solid solution between these two it's

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very rarely perfect one or the other so

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you'll see high magnesium calcite switch

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means you have less than one hundred

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percent of calcite and then usually you

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I actually found no perfect dolomite in

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any of my samples it was always

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something that was slightly less than

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fifty percent but something mineralogist

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would still classify as dolomite so here

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you have a layer of calcium lale layer

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of carbonate and on and on in the

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dolomites you have a layer of calcium

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carbonate than a layer of magnesium

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carbonate so it kind of goes back and

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forth which is a nice orderly way but

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that never happens in real life it's

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just theoretical so magnesium content in

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the carbon and cement so here are my

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actual rocks in the triangles you have

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adobe creek which i'll use throughout

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the rest of the presentation in squares

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we have del perrito creek and you'll see

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that we have magnesium content from 0%

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all the way up to fifty percent which

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would be perfect ideal dolomite and then

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one hundred percent calcium all the way

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down to fifty percent so adobe creek end

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up where two creeks are there this is

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where dolomite would plot what we'd call

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dolomite about thirty-six percent

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magnesium all the way up to fifty

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percent magnesium in the crystal

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structure and you'll see a lot of those

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points fall into the dolomite range oh

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but then you also have a lot of in high

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magnesium calcite and obviously there's

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a lot more of that in adobe creek than

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we see in del puerto creek but that

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could be sampling bias let's be

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realistic and then there's also low

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magnesium calcite i only have one point

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represented in that and it may actually

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be in a ragga night for those of you

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meteorologists or challenges out there

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so the next thing i want to talk about

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quickly with dolomite is that not only

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is there variable magnesium content

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there's also the concept of order and

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disorder so this again is the ideal

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dolomite structure right so you

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a layer of calcium layer of magnesium

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and on and on and on so an ordered

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dolomite can have variable magnesium

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contents but those magnesium elements

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will stay confined to those orange

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magnesium layers so you could find

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magnesium here here and here but you

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also might have some calcium

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incorporated in there so that's what we

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call an order dolomite a disordered

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dolomite is something that you

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definitely have magnesium those

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magnesium layers but you can also have

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magnesium in the calcium layers so it's

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a lot more mixed up which is why we call

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it disordered so you could see magnesium

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at any one of those layers so here's an

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x-ray diffraction pattern don't get too

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nervous if you don't know what this

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looks like I'm going to be a pretty

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simple example so this is an actual

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pattern from one of my rocks that's

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pretty representative of the hole and

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I'm going to overlay an ideal dolomite

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pattern right but this is not ideal

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dolomite this is this is actually a

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dolomite with variable magnesium content

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that's actually disordered so the way we

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know that is you'll notice that this

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peak right here which I'm pointing to in

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with an arrow because this is the one we

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like to use because it's nice and strong

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it's very wide here and that's an

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indication that we're getting lots of

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different magnesium contents in a very

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small amount of material that we are

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measuring so there's a lot of

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heterogeneity and then also you'll see

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that this peak is very offset from where

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the ideal peak is right so here's the

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peak I've and then there's the overlay

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and that offset is an indication of

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disorder so we know that just based on

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the xrd patterns that there's lots of

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different types of magnesium contents

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and also disorder in the structure and

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there is tem data to back this up if

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you're interested to look at it with me

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but I didn't have time to show it today

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alright so just to review where we are

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the so far so these are streambed

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conglomerates that means they're low

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temperature so they're formed at Earth's

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surface temperatures it's disordered

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which we're pretty sure is modern

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because if you give it enough time it

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will eventually order itself so we know

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it's a modern dolomite and so what we

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need to investigate nests at the edge

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the microbial involvement and so how I'm

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going to do that as carbon and oxygen

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isotopes and I'm only going to show

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carbon today so here's an adobe creek

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rock and a del puerto Creek rock finally

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we see some rocks you'll notice that del

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cuadro creek looks pretty distinct it's

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got a lot more it's not more classed

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heavy and so here are the different

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textures of carbon it you find within

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these so you'll see these laminated on

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these layers on the clasts which are

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pretty beautiful there's vein fillings

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that you'll see there's this fine

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grained sort of grayish material that we

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can't you can't see any sort of textures

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in there and then surface laminations

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which are nice and thick but I'm not

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going to talk about the surface

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laminations today so here's what

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laminated looks like in opted for an

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optical microscope and also in

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backscatter electron on the SEM I like

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to point out that this is pretty narrow

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which is why we had to use a lot of kind

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of Institute techniques in order to

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investigate this just crushing it up is

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not really good enough to understand it

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so anyway this here are the carbonate

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layers and there's a lot of clay mixed

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in there so again this isn't backscatter

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right here would be a clay layer and we

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can talk about clays for those of you

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that interest in clays if you want to

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talk with me later here's the vein

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filling looks very similar and like to

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point out this is 500 microns which is

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about the length of that here's what

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fine grain material looks like and

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you'll see it's a lot messier clay is

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kind of mixed in and not in any sort of

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wrap up ordered way and then you get

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this sort of smooth looking appearance

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in the fine grid material in the

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backscatter so why do I bother with

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carbon isotopes so there's three

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isotopes of carbon 12 13 14 12 is the

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most common 13 is a stable I stable

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isotope and 14 is radioactive so we're

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going to ignore 14 for today carbon-12

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and carbon-14 we we measure the ratio

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between them biological processes

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preferentially use carbon-12 and so if

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you have more carbon 12 what you'll see

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in the ratio is you'll see more negative

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as that gets more negative means more

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biology lower carbon 12 is more positive

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so here's an example of how organisms

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can drive carbon isotope ratios and as

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it drives more negative you'll see all

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these different microbes and that can

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drive the ratios more negative so I did

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Sims analysis which secondary ion mass

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spectrometer which we can do isotope

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ratios with

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10 micron spot sizes which is super cool

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we can talk about that later if you want

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here's where the spots are just in case

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you have a hard time seeing them and

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here are the results so triangles are

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adobe creek squares or del cuarto creek

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and what i want to point out first of

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all is negative 8 to negative 13 that's

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a pretty small range here i'm going to

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split it out by rock and by creek to

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kind of see if we can see anything so

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there's the two different rocks from

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adobe creek i investigated that's where

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dolomite calcite and low magnesian

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calcite plot you'll see the first thing

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i noticed here was i thought that

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dolomite might have lower isotope ratios

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you know because more microbial

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involvement but there actually is no

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correlation there because the high

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magnesium Cal sets just as lo del Puerto

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terrific you split it up by rock you see

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no correlations again there's the more

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dolomite than you see in adobe creek and

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then they split it out by textures so

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laminated fine grained vein filling

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nothing pops out of the data there's all

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of it together and so i just spent all

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my time you know i went through all this

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and we didn't we didn't find anything

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interesting in the in the carbon isotope

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data but that doesn't mean that this

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isn't interesting at all and what we see

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is this negative eight to negative 13

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actually matters so that's more negative

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than you're going to find in that

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completely inorganic material but it's

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00:12:37,060 --> 00:12:36,020
not as negative was we wanted to see we

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00:12:39,370 --> 00:12:37,070
thought there would be some sort of

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interaction with microbes on a small

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scale which you get super negative

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numbers which we didn't see which was

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kind of a bummer but it still indicates

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Biogen icity and just to give you a

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sense of how homogenous this material is

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that pink circles are where my samples

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plot whereas the other samples are

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fields of different carbonates in ohio

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light sweets and other systems not

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always dolomite but it's super super

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tight data field which is interesting

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unto itself and so we thought we'd find

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negative carbon isotopes we did but they

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weren't as negative as we wanted and we

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didn't see that dramatic variability but

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we did find the mineralogical

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heterogeneity which is pretty

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00:13:25,090 --> 00:13:21,710
interesting unto itself so there is an

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evidence of life in these rocks but it's

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not a slam dunk

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so thanks do we have any questions for

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do you have any idea at all what the

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microbes how the microbes interacting

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00:14:03,860 --> 00:14:01,680
with the carbonate and forming a bio

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00:14:05,360 --> 00:14:03,870
signature or you just know something is

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00:14:07,100 --> 00:14:05,370
going on we know that something is going

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00:14:08,660 --> 00:14:07,110
on it's hard to say and a lot of people

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00:14:10,790 --> 00:14:08,670
have different theories right now it's

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kind of the the debate in the dolomites

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literature at the moment so sometimes I

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00:14:18,500 --> 00:14:16,620
think it might just be the sort of

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00:14:19,699 --> 00:14:18,510
extracellular material that goes along

370
00:14:21,560 --> 00:14:19,709
with the microbes that might be

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00:14:23,750 --> 00:14:21,570
influencing it but basically you want to

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00:14:25,310 --> 00:14:23,760
separate the magnesium from the water

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because magnesium and water love each

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00:14:28,639 --> 00:14:27,390
other and magnesium can't get into the

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00:14:30,170 --> 00:14:28,649
crystal structure so anything that

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dissociates that magnesium from the

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00:14:33,199 --> 00:14:31,950
water and allows it get into the crystal

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00:14:41,540 --> 00:14:33,209
structure is what's happening

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00:14:43,970 --> 00:14:41,550
essentially you said you're negative

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00:14:45,519 --> 00:14:43,980
carbon isotope values were not a slam

381
00:14:47,960 --> 00:14:45,529
dunk I was wondering if you could

382
00:14:50,810 --> 00:14:47,970
comment on what the minimum negative

383
00:14:52,460 --> 00:14:50,820
slam dunk value would be and then if you

384
00:14:58,069 --> 00:14:52,470
could just give a one-sentence summary

385
00:15:00,199 --> 00:14:58,079
of your oxygen isotope result okay so we

386
00:15:01,639 --> 00:15:00,209
were hoping to see negative 15 and below

387
00:15:06,829 --> 00:15:01,649
that was kind of the number i had in my

388
00:15:08,780 --> 00:15:06,839
head negative 10 could be happening with

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00:15:10,819 --> 00:15:08,790
nothing to do with the microbes so net

390
00:15:12,280 --> 00:15:10,829
rivers naturally have a negative isotope

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00:15:15,079 --> 00:15:12,290
value because you're getting this input

392
00:15:17,300 --> 00:15:15,089
from the surrounding watershed which all

393
00:15:18,530 --> 00:15:17,310
these plants and animals and microbes in

394
00:15:19,910 --> 00:15:18,540
the soil and so you're getting that

395
00:15:22,280 --> 00:15:19,920
negative carbonized to have input into

396
00:15:23,690 --> 00:15:22,290
the water itself so something that

397
00:15:24,949 --> 00:15:23,700
negative doesn't necessarily have

398
00:15:26,540 --> 00:15:24,959
anything to do with the microbes in the

399
00:15:29,180 --> 00:15:26,550
lake it could have something to do with

400
00:15:30,650 --> 00:15:29,190
the organics and the in the watershed so

401
00:15:32,569 --> 00:15:30,660
I really wanted to see things negative

402
00:15:33,740 --> 00:15:32,579
15 negative 20 which is what we thought

403
00:15:35,630 --> 00:15:33,750
we'd find we thought we were seeing

404
00:15:37,069 --> 00:15:35,640
averages in the bulk scale but it turns

405
00:15:38,900 --> 00:15:37,079
out that was actually what is on the

406
00:15:41,720 --> 00:15:38,910
fine scale as well and then with the

407
00:15:43,250 --> 00:15:41,730
oxygen isotopes I just got the data last

408
00:15:45,050 --> 00:15:43,260
week so we're still working on it but

409
00:15:46,400 --> 00:15:45,060
some of the preliminary stuff we saw was

410
00:15:49,220 --> 00:15:46,410
there is separation between the

411
00:15:50,780 --> 00:15:49,230
different textures so fine grained and

412
00:15:52,370 --> 00:15:50,790
laminated material plots in completely

413
00:15:54,050 --> 00:15:52,380
different areas so these are probably

414
00:15:55,550 --> 00:15:54,060
different generations of growth either

415
00:15:57,620 --> 00:15:55,560
they grow in different seasons or a

416
00:15:58,550 --> 00:15:57,630
different times of the day or there's

417
00:16:00,110 --> 00:15:58,560
different like that we don't know

418
00:16:02,480 --> 00:16:00,120
exactly what but there's definitely some

419
00:16:04,069 --> 00:16:02,490
clumping of the oxygen isotopes which I