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i want to thank you lucy and all those

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who came before me you guys did a

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wonderful job of setting up my my talk

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you saved me a bunch of time and uh that

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stress on me so this is an integrated

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study between uh inorganic and organic

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proxies

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and uh i study other tim lines and

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gordon loves so biomarkers and a lot of

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proxies is what you're going to see in

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this talk so let's get started

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you're going to see

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this huge redox timeline from about 4

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billion euro 4 billion to the present

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first off the red curve you see is the

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classic uh two-step

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oxygenation event that you know the 2.4

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and around the 0.8 or so

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the blue curve is an emerging

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model that shows that right after the

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great oxidation event occurs it dips

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down to about 10 to the -3 pal

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and

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rises again until maybe about 0.9 again

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and you can find this on lions 2014.

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i want to highlight that eukaryotes

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fossils were found at around 1.9 and the

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rise of animals occurred shortly at

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around 500 million years ago

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right below that is the classic redox

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structure of the ocean for the first two

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billion years you see that it's an

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anoxic or fruitiness

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water column that has free iron in the

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ocean

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and then right below that is actual data

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collected from shales and

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why is this important is because

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life as we know it started in the ocean

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and studying what the condition of the

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ocean back then was is really key to

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unraveling the mysteries of how life

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so my study take place at around 1.5

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right after eukaryotes have already

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emerged

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so the boring billion what is it it's a

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period during earth's time during the

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mid protozoax about 1.5

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and

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it got its name from

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very little variation in the delta c13

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record

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and you just see a flat line for about a

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billion years

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and we believe that this is what

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what caused the eu carryout

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diversification to

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stagnate

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and recent studies have shown that you

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know the boring billion is is a misnomer

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it's not really that boring

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because if you guys recall there's two

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oxygenation event that flanks both sides

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of the boring billion so this implies a

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very uh unique ocean chemistry it's

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neither anoxic and ferogenous like the

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archaean

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but it's not uh fully oxygen like the

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phanerozoic either so it's somewhere in

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luckily most of my data uh and uh in

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general because lucy mentioned that

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there is various uh scarcity in the rock

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record to show where these

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oceans come from

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my record my rock record comes from the

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outreach core so thank you uh

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kira for showing what you what the core

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looks like

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and

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this site in northern australia at the

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tip

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was originally

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surveyed because there were reports of

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live oil by jackson and i'm grateful for

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that because they did some

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sedimentological studies and geochemical

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studies to show that these shales were

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marine in origin and paleo geographic

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data showed that it's a lot more

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connected to the ocean than the

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previously studied barney creek where if

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you guys read any of those papers that

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they reported green and purple sulfur

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bacteria which is an indication for

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photic zone eugenia

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so eugenia is an anoxic waters with lots

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so this will be the only data slide to

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see uh just stick with me and i'll guide

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you through it

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on the left is the strat column of my

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outreach core uh these are all shales so

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if you don't see them or they look like

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sandstone i apologize it's just

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compressed

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right away you notice that

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that they're aligned very nicely this is

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organic carbon by weight percent

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two iron proxies which is a ratio here

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and two

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trace metal proxies molybdenum and

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uranium

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overall they show a very unique pattern

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you can see that organic carbon tracks

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the iron and the metals very well

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and every time i meet up with my advisor

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he ends the talk with nice data

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which is something you know you want as

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so once organic carbon kicks in at

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around 700 meters you see that the iron

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also rises above this

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red dash line that i put in now this is

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the upper limit for a cutoff where

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oxygen

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on the left side of the dashed line is

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oxic

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and data points that lie on the other

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side is

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anoxic now these aren't hard cutoffs it

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depends on really a lot about your

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setting and you need to have context

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about your geologic

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rocks so that you know you can move the

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bar slightly left or right depending on

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your settings

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any rocks that are anoxic can also

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further tell you by the

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pyrite uh iron pyrite to the highly

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reactive that they're using so there was

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a lot of hydrogen sulfide that bound to

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these rocks showing that they were

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a zeozitic water column

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so these two alone tell you the local uh

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water redux right now what does the

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trace metal proxy tells you

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intrinsically they're also local so if

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you were to look at molybdenum you see

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that it's flat lining at crystal value

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until you hit

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the

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around 900 to 700 meters

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and then you see that it spikes all the

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way up to about 115 ppm now this is one

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of the highest recorded molybdenum

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concentrations in the mid protozoa

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so you know and if you were to read uh

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scott 2008 he would track the molybdenum

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all the way down to the mid protozoa and

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it's actually

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these concentrations were higher than

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his

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uranium also tells the same story it's

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independent uh berry is independently

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buried next to a molybdenum see

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molybdenum requires hydrogen sulfide to

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be buried whereas uranium only requires

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reducing conditions which is anoxic to

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be buried so you know that these signals

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are genuine and they're not a

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false positive by maybe they try to flux

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when you combine these trace elements

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with the iron proxy

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you can get a lot of data and even infer

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global reservoirs

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so in the orange box when you have

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molybdenum data that is very low in the

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20s to 40s

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global usania is only possible if you

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have

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iron proxies that suggest that

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molybdenum is low which is here

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and the toc is high which you see right

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and also when the iron proxies show that

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it's eugenic

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however that's not the case and we know

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that it's not globally eugenic a

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canfield ocean if you will

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because there were a lot of molybdenum

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being enriched during this time

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and it's using a cure so therefore it's

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not a global extent

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uranium on the other hand just tells you

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that yes this was both also anoxic

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so when you when you when you develop a

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paleo organic

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proxies like this you build a backdrop

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so that you can look for biomarkers a

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lot easier and this is one of the first

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integrated search

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where i combine inorganic proxies so

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that i can look for molecular biomarkers

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a lot easier

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i didn't want to bore you guys with you

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know boring chromatograms but i'll tell

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you that i targeted areas that have high

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molybdenum

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because it's an essential

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nutrient for nitrogen fixation

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and areas of high organic carbon

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just so that you know animals or fecal

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pellets were buried there or just whole

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pains

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you also want areas that are above and

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below

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the eugenic transition so that you can

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have a comparison

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this is one of the very few studies

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where if you find something it's

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fantastic news but if you don't find

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anything that's also good news too

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because it's what you predict so in this

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case

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i wasn't in a losing situation at all

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uh the bottom line was that when i went

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through all these samples about 120 i

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don't really see any detectable steering

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so steering is a cholesterol that is for

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a

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in these

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so to sum it up the evolution of the

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atmosphere in the ocean is a lot more

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complicated than originally theorized

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and that makes sense

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uh long-lived geochemical stability of

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the boring billion the flat line delta

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c13

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australia has some of the best data in

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the world