This is geology B with all of us trampled.
In 1788, James Hutton, spotted a spectacular and Conformity at
siccar point on the east coast of Scotland.
He was the first to understand that although to sedimentary
rock types were in contact with each other, they're the boundary
between them represented a gap in the geological record.
The Rocks below which contained Marine fossils were deposited in
a deep ocean during the silurian.
But only after these rocks had been folded uplifted and eroded
where the overlying Rocks deposited in a devonian desert.
In this very clear-cut case, 80 million years are missing from
the record but the gaps in the sedimentary record are not
always so obvious. Indeed sedimentary sequences
that look continuous and complete can be quite the
opposite. Clearly if we want to read this
element illogical record to make accurate inferences about the
past, we need to recognize and interpret the gaps in the
record, as well as the parts of the record that survived to the
present day. How do depositional mechanisms
and subsequent events alter or destroy parts of the record more
fundamentally? How can we tell that the record
is good enough to make any solid inferences about the geological
past Bruce level addresses. These questions by combining
field work with systemic analysis based on what we know
about contemporary depositional an erosional processes.
Armed with an understanding of the preservation all biases that
can apply. He has been re-examining, some
widely accepted interpretations of the sedimentary record.
For example, by analyzing sequences of glacially
deposited, rocks, in South West, Scotland.
He has shown that contrary to the widely held snowball Earth.
Hypothesis parts of the earth were not covered by ice.
At least during the earlier of the two snowball.
Glaciations Bruce. Oil is a visiting professor in
the department of Earth Sciences at the University of Oxford.
Previously, he was Chief scientist for Geology at Royal
Dutch. Shell Bruce level.
Welcome to geology, B, pleased to be here.
Oliver, let's start with the fundamental question.
I just raised, how do we know that the sedimentary record is
complete enough to make solid inferences about the past?
This is a very old question, it goes back to Darwin or perhaps
even earlier in the Origin of Species.
He wrote, I Could the geological record as a history of the world
imperfectly, kept and written, in a changing dialect of this
history, we possess the last volume alone relating to only
two or three countries of this. Volume only here and there a
short chapter has been preserved and of each page, only here and
there a few lines. So Darwin's problem was that he
was being challenged to produce the intermediate forms which
document the evolution of one species into another by natural
selection and his defense to not being able to produce that many
examples of intermediate forms, was that the record was
imperfectly kept as you wrote here?
So it's a fundamental question and I think the answer is we
know that the record is incomplete.
So your question is it complete enough?
It also very well phrased. Because whether or not, it's
complete. Depends upon the question that
you're asking. So if we look at Darwin's quote
and we change his metaphor a little bit, if I were to keep a
diary, and I want to miss the occasional entry that might be
sufficient to give you an idea of what I was doing for the
year. If you just wanted to know, what
is Bruce, get up to, when did he go on holiday?
How much time does he spend working?
But if you wanted to know, what did he eat every day, then the
entries wouldn't be complete enough to answer that question.
And they might be incomplete in different ways.
So it might be that I don't write down on Friday.
Evenings what I'm doing because they don't get around to writing
my diary. So you'd have a systematic error
or bias in the record that Friday's won't preserved.
So data has been collected or sedimentary record to ask
exactly this question. This was done by a guy called
Pete, Sadler in the early 80s and he made an extremely
revealing plot which has on the vertical axis, the accumulation
rate of sediments and on the Horizontal axis.
It's got the averaging time over, which the rate has been
measured. So if I measure a rate over the
duration of a flood that would be entered as maybe a week or
perhaps a month on a big river when it was in Spate and we're
how much sediment was deposited during that event at The Other
Extreme? I look at sedimentary basins and
I say, what is the accumulation rate of sediment in say the
Wessex Basin of Southern England and what you find on that plot
is A linear inverse relationship between the accumulation rate
and the time over which its measured.
So my flood, deposit is accumulated relatively fast over
a short period of time, maybe a meter or even 2 m over a month
whereas in the sedimentary Basin, I'm talking about, mm a
year meters over thousands of years, maybe even tens of
thousands of years in some cases.
And what it says is that there are gaps at alterations in the
God and those gaps accumulate as you increase the averaging time
and therefore become more important.
So the record does have the fractal gaps that Darwin
postulated back in 1859 are we sure that we always do know when
something is missing might something look complete when in
fact perhaps it isn't absolutely it often looks complete.
When in fact, it isn't and that's a mistake, I've made many
times in my career typically when you look at core data,
extracted from the subsurface, Yes, it's a vertical column and
maybe only four inches, wide, 10, cm wide.
And I'm always surprised when I get the paleontological data
which tells me that there's time missing, there's always more
missing than you think mind. The gap is a very good slogan
for a sedimentology. Just what?
Exactly would we like to learn about the past?
If only, we could correctly interpret, the sedimentary
record, there are two main ways. We use the sedimentary record to
extract information, The first as a Time series of information
as Darwin would have liked to, he would have liked to have had
a continuous time series. All be it put together from bits
of the record, in different parts of the world to make a
composite time series but a continuous time series from the
origin of life to the present day in the modern day.
With the Fantastic advances in geochemistry particularly
isotope geochemistry people that are wanting to put together,
continuous complete records of the evolution of the Earth's
system. So ocean chemistry.
Chemistry, ocean temperature, any information about the
atmosphere, which you can get from, for instance, plant
remains or even trapped air in Antarctica, and in the ice
cores. So, continuous, time series of
data and some examples of those might be the Paleo climate
interpolating time between points of control, where we have
radiometric ages, understanding the fossil record and how it
evolved and understanding events in geological history.
I'm putting them in their time, sequel.
So those could be major climate shifts.
That could be major storms. They could be sea level changes
could be meteorite impacts various scales of occurrence
from almost daily weekly, monthly events which are making
up geological record by putting deposits down.
In a particular way to these spasmodic episodic revolutionary
events and then the second way in which we use the sedimentary
record is to predict essentially to geometry of sedimentary
deposits. Because we want to use them to
extract things or to store things or to build things on.
So, in that case, we want to understand the three dimensional
geometry. And in order to understand the
three-dimensional geometry, the obvious route to use is the fact
that all sediments are deposited in an environment and that
environment. If you'd have had a sort of
paleo satellite back, when the Rocks were being formed, would
have looked like some sort of map of channels and bars and
beaches and coastlines and tidal inlets.
And Our fans, etc, etc. And if we can reconstruct the T
position of environment, then we can predict to a degree the
three-dimensional geometry of the rock units.
So those are the kind of two main classes of use.
I'd say of the sedimentary archive.
Okay, let's talk about the preservation, 'l bias.
If you like, in the record in the context of each of these
aspects. So first of all, what kinds of
bias would tend to confound our understanding of the Palio So
climate in order to understand the Paleo climate, we need to
make a measurement which response to temperature, so
called proxies can be a wide variety of things.
So for example, people look at the temperature of formation of
soil, nodules using carbon and oxygen Isotopes.
You can say something about the temperature, which is soil
experienced. Alternatively, you might look at
changes in the rate of phytoplankton production or you
could measure the surface temperature of foraminifera
living in the surface of the And you might even be able to
compare that with the temperature of foraminifera,
living on the bottom of the ocean, so you could get the
temperature gradient in the water column.
So you want to take a series of samples, which you can analyze
in a lab and extract some temperature data, typically
using an isotopic proxy. Now, in order to do that, you
need to make a series of assumptions in order to have
that. As a Time series of data, the
first is that the record is indeed continuous at the scale,
at which you wish to sample it. So, So if you're want to
reconstruct this over the time scale of 25,000 years or so,
then you would need on that time scale.
They're not to be gaps in the record so you could go to
sedimentary sequences. We're on the time scale of a few
thousands of years, record is continuous.
And the obvious one to go to is a deep water deposit because
they're the preservation will bias is very low.
Almost everything that falls down to the bottom of the ocean
gets deposited. To provided it doesn't get eaten
or in the deep ocean gets dissolved.
So they're your problem is less great.
If you like you have more chance of being successful, the
preservation biases, due to burrowing organisms coming
across my microorganism and eating it before, it has a
chance to be preserved or eating all of them from a particular
time period before they have a chance to preserve.
If we come back to my soil nodule in a Fluval sequence, the
situation is entirely different because the soil model is
forming. Outside the channel of a river.
Now, that channels of rivers tend to migrate they don't stay
in one place forever, they migrate sideways.
And therefore, they erode, soil profiles and particularly those,
which are closer to the level of the river are going to be
destroyed. And those are going to be
preserved would be the ones for example, on Terraces, which are
at a higher level away from the river itself.
So you'd end up with a record, which would be variably
incomplete and it might even be difficult to reconstitute.
For instance to Terrace deposits will be topographically higher
than the river channel. So they would not be
contemporaneous with that particular River channel.
So, you end up with a problem of sorting out the age
relationships, if your variable sections in which you've
measured these things and you also end up with the record that
quite a lot of the sequence may be destroyed depending on how
far the river eats into the flood Basin.
So those are two contrasting situations in general.
Preservation bias is very strongly controlled by erosion.
Ian, the most dangerous thing for a sediment is after, it's
been deposited is to be re eroded by the next River flood,
or by the next storm. And it's only when it subsided,
a certain increment out of Harm's Way.
So Below the depth of the migrating River Channel or below
the erosional capacity of the subsequent storm, it's been
buried. Sufficiently deeply that it's
definitively preserved. So sediments after d position,
they're kind of tentatively preserved.
And they may spend 10 20 30 40 50 hundred thousand years in
tentative preservation and it's only subsidence.
Which definitively preserves them by removing them from the
zone of active surface, currents and waves, Etc.
You refer to connecting the two different time scales that we
have and indeed a major undertaking over the past
decades has been the marrying of the stratigraphic time scale,
which is So on the sedimentary record with the absolute time
scale, which is determined from radiometric, dating?
Can you quickly remind us how that is done?
Yeah. Reliable, radiometric dates from
sedimentary rocks, are really difficult because you basically
need a high temperature mineral to set the isotopic clock
running and preserve the daughter products, and the best
mineral that we have. The middle of choice is clearly
Zircon with uranium-lead dating because it has a couple of
isotopic systems when you can. Do internal, consistency, checks
and those? Come from, felsic, volcanics.
And so what you need is to find volcanic Tufts into bed with
sediments and ideally. Those sediments should be fossil
bearing and then you can calibrate, the fossil record
with the absolute age that you get from those radiometric dates
as an example. The lower Jurassic blue Liars of
Lyme Regis, which many people know, the radiometric dates,
which date part of that succession come from Peru.
Because that's where no Jurassic have It's a nicely into bedded
with well dated Tufts in the Andes.
So what that means is that you've got a bunch of ammonites
in Peru. Unfortunately, the same evidence
didn't live in Dorset, the different biogeographic
provinces. So you need to connect the two
groups of ammonites and their evolution re records across two
different oceans and you do that by finding intermediate fossil
groups with which both can be interbedded or via you can find
a connection. So you might find pollen or you
might Find foraminifera again or calcareous Nano fossils,
whatever. It might be.
That can connect those two formal provinces together and
then you end up with inferred radiometric ages for Lyme Regis.
Now, you still only got a few ages and quite a lot of rock.
So if you want to make a Time series of paleo climate data,
for the lower, Jurassic in the UK, you have to interpolate
between the radiometric points and method of choice for that is
to use the rhythms, which come from orbital cyclicity.
So you have the change in the Eccentricity the change in
frequency of the orbit and the change in precession of the
Earth's axis just to explain the Earth orbital eccentricity is
the amount by which the Earth's orbit around the Sun deviates
from A Perfect Circle which varies with about 100,000 year
periodicity. The obliquity is the tilt of the
Earth's axis of rotation with respect to the plane of the
Earth's orbit around the Sun and that varies with a periodicity
of about 41,000 years and the procession Is the wobble of the
Earth's axis like that of a spinning top which has about a
26,000-year period. Yeah.
And these combined give you a series of ratios effectively
between those rhythms which you can find back in the geological
record as expressed by differences in the sedimentation
if you're lucky. So if for instance, you've got
difference in the rate of production of calcareous
Plankton that would Express itself in a liveliness of The
Rock and you can measure that line - directly or indirectly
and Up with extracting these rhythms and then you can
so-called astronomically tune the time scale.
So you can count The rhythms in between your radiometric dates
and you can infer a an age between the radiometric age
points. And in the last edition of the
geological time scale, there's been a major major attempt to
astronomically tune large parts of the stratigraphic record and
this is actually a major undertaking but it does require
huge be able to find composite sections in the record which are
eat and continuous and it can be very confusing of sedimentation
rate changes because the Rhythm that you're measuring is in
thickness, not in time and you have to transform it from
thickness to time. Using the argument that you've
got a complete Rhythm. So it is quite an involved
exercise and it sets very high requirements on completeness and
continuity of the record and also steadiness of D position.
If now, there is something that's interfere with the
sedimentary record, Occurred in those intervening bands, between
the radiometric dated bands, does it always show up and can
we then account for that? It's a real detective game that
a night. So nations in this case can give
you a clue as to where things are missing.
But there are some beautiful examples.
If you compare this lower Jurassic in Lyme Regis with the
lower Jurassic on the other side of Southwest England and summer
said, you can see that the Lyme Regis section is extremely
condensed with respect to the somerset section.
And you can actually identify particular bedding planes where
stuff has to be missing based on missing every night.
Sounds and I've been and looked at them and the crawled all over
them. Oliver, there is nothing.
You find a few scattered economic aid, spines and a sharp
bedding plane on a calcareous limestone and that's it.
And yet, the evidence is saying that several tens 200,000 years
is missing on that particular surface.
It's really frightening. It's really frightening because
if you didn't have the more complete Section, you wouldn't
know that's coming back to your earlier question.
You also mention our desire to use the sedimentary record to
understand the environments in which fossils lived in perished,
what sort of bias affects the record then, how can we overcome
their effects? Actually, the paleontologists of
studied preservation potential a much more detailed and
sedimentology is from for a longer period of time.
There's a whole branch of paleontology called to follow me
which is the study of what happens to things when they die.
The extent to, which soft tissues, get preserved, and
also, how you can reconstruct how things came to Die.
The biases in the record. I think the most obvious one in
paleontology is dissolution. So, the sedimentary record is
incomplete. Not only through erosion but
also just dissolution of material.
It's very common in sedimentary sequences to only find
particular fossils. An example would be finding
oysters and economic needs and nothing else.
There's a formation we're working on in a moment.
And at the moment and that's the situation there.
And the reason is that those are calcitic forms and many of the
animals that would have lived at the same time.
Precipitated shells from aragonite and those are
agonistic forms of subsequently been dissolved.
So you've got a preservation bias towards the calcitic forms,
more robust forms, obviously hard bodies as opposed to soft
bodied organisms and then as far as the sediments themselves are
concerned, you preserve the organisms which live in the
sediments, which get preserved. It.
So the organisms, which were happy living in the bottom of a
fast-flowing title Channel, stand a chance of being
preserved, the razor shells, which were at the same time,
living in the tidal Flats which are not being preserved, don't
get preserved. So, it comes with the territory,
the sort of bulk preservation of the sedimentary record as well.
Okay, let's talk about reconstructing discrete events,
that occurred in the geological past.
First of all, what kind of events are you referring?
Dying to hear. So, I'm thinking of the
question, you have an intubated sequence of sounds and modes.
For example, maybe it's a shallow Marine sequence and
you'd like to say something about the intensity of storms.
So I think these are individual graded beds, so they fine
upwards. They're deposited by discrete
events of flows, which are waning over time and hence
depositing. So how strong were they can I
say anything about the relative strength of storm intensity here
versus there? The type of Coast the same for
floods are these Rivers Characterized by very strong
flows seasonally or you could average flows over a long
periods of time in a sort of temperate setting.
What can we say about those kind of situations?
It's a very interesting problem because there was a classical
study done on the coast of Southern California, where they
asked that question of modern shallow Marine sediments whose
age they knew, because they repeatedly surveyed the shelf
and they knew when the deposits have arrived and what they were
able to show was that it was Highly contingent what got
deposited. So firstly, in order for
something to be recognizable in the shallow Marine record, it
should not be burrowed to destruction.
So if you just deposit after a storm, a graded sand bed, and it
stays within about 10, cm to the surface and the burrowing
Foreigner at the bottom of the sea, just destroy it, and it
becomes unrecognizable. All the sand grains are moved
around, you can't recognize it as a bed anymore.
So in order to be preserved, it has to be insulated from Going,
which means buried below the Zone in which the animals live.
So the most important thing for preservation is that something
happens afterwards. It's nothing about the event
itself, but it what happens, subsequently you need a rapid
other event which buries it. So it's telling you nothing
about the magnitude and then they tracked these storm layers
back into the flood basins of the rivers from which they've
been derived and they were able to show that the amount of
material that was being transported to the a shelf in
the first place, had nothing to do with the intensity of the
storm or the flow in the river. It was the event which occurred
the rainfall event, which occurred when the river was
already full of sediment. So previous events had push
sediment from the hill, slopes into the river and the sediments
were in the bars and banks of the river and the bottom of the
river. And it was only when the river
was actually full of sediment that a next event flushed, it
all out to sea. So it was highly contingent.
What got preserve, it was a flood event which happened to
occur when the river was full deposited on the shelf and then
the Shelf event, which happened to be preserved because
something else happened later. So the conclusion is that the
record is highly contingent. And actually almost impossible
on a bed by bed bases, to reconstruct.
So, that's kind of disappointing in terms of what we could
extract from the record but I find it fascinating in the sense
that as scientists. We are taught to see a record, a
sequence of events and interpret it deterministically.
And we don't give perhaps enough credit to the chaotic
interpretation, where a bunch of nonlinear functions are actually
combining to produce a signal which we wish to interpret
deterministic because that's how we've been educated.
But in fact, there is no meaningful deterministic
explanation that we can extract from it.
If only, we were back there, we could have a time-travel machine
and then we'd know actually what happened.
But in fact you're saying that, Contingency both on what
happened prior and what happened after interferes with what
happens in any given time, so it can just be two scrambled up,
too much information. Lost to be able to accurately
reconstruct. Yes, people are working on this
on different scales. I described it on a small scale
there but on a landscape Evolution scale or a larger
scale. What we want to do is extract
the external forcings of a particular event.
So how big was the hurricane? How big was the storm?
How big was the flood or how long was the Ice Age?
How big was the ice age or you can scale this up to what extent
did sediment input change or did the sea level for all?
These are alternative ways of making a coastline move forward
into the ocean, for example, and people talk of signal shredding.
It's a term, I quite like is that the interplay of all the
processes which are involved in bringing that sediment to the
coast, the storage, in the floodplain, they're sweeping out
by subsequent floods, they're actually shredding the input
signal. You're absolutely right.
If you were there. If someone could have observed,
everything that happened but reconstructing it from the
result and inferring a proximate, cause the warning
signs are there from the modern studies, that, that is an
extremely difficult exercise. And again, I'm concerned about
what we said earlier which is, is there evidence for the record
that the shredding has taken place, or might we just simply
blindly assumed that what we're seeing is the faithful record.
Well, this comes to the point of what is the null.
Offices with which you approach the geological record and I
think that's my Essential philosophical point.
You know, I believe that before allocating and external, cause
you need to rule out the chaotic interpretation, you need to rule
out the autogenic interpretation by autogenic.
I mean the processes which are intrinsic to a sedimentary
environment. So the and has migrated sideways
and spits, pro-grade into tidal inlets and barriers, smooth land
words and all of these things. Are happening just by virtue of
natural variability. There's nothing happening to sea
level necessarily or sediment Supply or tectonics, which is
controlling those and only, when you've ruled those out, are you
kind of allowed to go forward and invoke an external?
Cause that's the way I was brought up as a sedimentology.
She used to say that the sedimentology sprayer was Lord,
forgive us our transgressions because we would never invoke a
transgression. And this we had to because there
was no way out. Out of the particular situation
and it strikes me that there's been a bit of a swing of the
pendulum, the other way that people are very eager to move
straight to external forcing. And there are a number of deep
statistical debates as to what the null hypothesis should be
when you claim to see a signal in the sedimentary record,
particularly with this astronomical timescale tuning
and it is not a simple question. You also mention that we'd like
to be able to reconstruct the environment in which the
deposition we see preserved today took place.
Are you talking about things, like whether it was wind-borne
or waterborne, or if it was a water deposit, whether it was
Marine Fluval or from a lake, yes, that's why you'd start off.
And then what we would typically need to do is to go down to the
next level of detail. So if it's within the lake, is
it the beach of a lake lies at the bottom?
Of the lake. Or is it a Delta coming into the
lake? So what we're trying to do is
reconstruct the three-dimensional shape of the
sedimentary bodies that have been preserved, such that we can
either store fluids in the, my carbon dioxide or extract fluids
like water, or oil and gas, or build things on top of them.
So, we'll find a solid footing for our piles.
For instance, for Coastal defenses.
As sea levels rise. So, we need to know where
physically these different, litha somes, these different
little logical bodies actually are.
And What shape they are. So the trick there is to
reconstruct the new position of model.
So a river coming into a lake. For example, typically has low
wave energy. So you see the channels
protruding quite a lot into the lake?
We sometimes call it a bird's foot Delta, because it looks
like the three toes of a bird's foot, as it migrates into the
lake and bigger Lakes, you would see wavery working and you would
end up with smooth, cusp, 8, shorelines for instance, from
the waves. And so those two types of Delta
will give a different shape, Send bodies and we would like to
reconstruct that. And the preservation Point here
is that the body that we want to reconstruct is not simply the
plan view of the body when it was deposited but what ends up
being preserved over time and that depends on this overlay of
erosion due to base level changing, for instance, in a
lake based levels drop as the lake dries up and then they rise
again, maybe on a seasonal basis and each of those base level
lowerings will result in Channel indecision and Erosion of
previous material and make level rising will result in the Strand
plane and the beach truncating, the previous Delta material and
wiping it out. So you have to reconstruct a
three dimensional shape, which reflects the Deep additional
model and the preservation of filter.
It seems that there are actually a huge number of interacting
processes and chance events that can affect what gets preserved.
I wonder where you see the field going and whether perhaps you
think that the Problem of discerning and accounting for
preservation of bias is amenable to artificial intelligence and
machine learning. It probably depends in part on
whether we have a large enough data set of records for which we
know the biases that can serve as training data for a model.
That's a really good point. It strikes me that this problem
that we've got of disentangling, multiple interrelated processes
which have feedbacks between them is one which, Out AI,
you're not going to solve this, put it that way and I think
there is hope there and I'm looking forward to a literature
emerging on that topic. In an earlier podcast, Paul
Hoffman laid out convincing evidence for the snowball Earth
hypothesis, which posits that there are two periods during the
late proterozoic, during which the Earth was completely frozen
over. As I mentioned in my
introduction, you studied a sequence of glacial, deposits
and South West Scotland, corresponding to the earlier of
these two periods. So as to develop, A deeper
understanding of the preservation of bias that might
have been operating there. Can you tell us about that?
Yeah, this unit is the port Escape formation in Southwest
Scotland and it's dirty and it's the older of the two cryogenian
glaciations and it's exceptionally thick for a 30 and
sequins. And the reason why is
exceptionally thick is that the deposits have been preserved in
a basin, which were starting to rift at that time and so was
very Lovely. Subsiding.
And what that enables us to see is that we have a series of
alternations between glacial and non glacial depositional
environments. So we can clearly demonstrate
that ice was advancing and retreating.
We could demonstrate that the ice was grounded.
We have lots of Glacier, click taluk features which indicate
the advance of ice over land surface and we have lots of
periglacial features which indicate the exposure of a land
surface to the air. And we have glacial flow of your
glacial Coastline and Glacial Marine deposits.
So we can demonstrate that there was an active hydrological cycle
during that time and the planet wasn't completely Frozen during
the deposition of that material. Now in the classical snowball,
which I think is not fully believed in its hardest
theoretical form anymore. It posited that the entire Earth
was frozen at that time and a bit of an issue there.
With this particular sequence is that if the Earth Was totally
frozen. And there was nothing happening
based on substance, wouldn't really know about that and
basins would continue to subside.
There's no reason why rifting process has stopped because the
Earth got a little bit cold on the surface.
And therefore, if there was no sediment input into a basement,
because the entire Earth was frozen, you would create large
holes in the ground. And when sedimentation
restarted, you'd have to start in relatively deep water,
filling up, those holes. So, the ice would melt, the
holes will be filled. And then the sentiment would
arrive perhaps as the ice melted into these holes, and that is
not the sequence that we see in Southwest Scotland.
So, we feel that we're adding detail to the nature of the
snowball Earth. What you working on at the
moment? I'm editing the successor to a
standard, sedimentology text book that was published in 1996
by Harold, reading and co-workers.
And her breathing was my supervisor, it's called
sedimentary environments, processes and fasces, one of the
Why I wanted to take that up? Was this point that I wanted to
bring an understanding of preservation to the D positional
models in the next update of that book?
And then another project together with a guy we both
know, I think droste and Mike. So we're working on the
sediments, that were deposited during the Abduction of the
ophiolite in our man. So trying to understand from the
sedimentary record, what we can deduce about, how the continent
reacted to the Loading by the ophiolite slab when it ended up
on top of Mia. And that's turning out to be
quite an interesting problem because what the healthy like
slab did is it caused a carbonate platform to drown and
when the carbonate platform drowned, there was no sediment
production because it became too deep.
So in essence, we have a record of water depth being created
without a sediment in filter record what actually happened in
detail during the abduction process.
So it's a staffed sedimentary Basin sort of an extreme example
where you Reconstruct the record because sediment Supply was so
little that it's not been documented.
Bruce level, thank you very much.
You're welcome. It was fun for more about
geology b as well as pictures and illustrations that support
this podcast, go to geology B.com.