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Just to see if I'm on the same page as you let me make a few introductory
comments.
Since we were not there to see the formation of sedimentary rocks, in order
to attempt to discover how they were formed (and subsequently lithified),
we look to analogous depositions occurring now in the world around us. As
Raymond in Petrology: The Study of Igneous, sedimentary and Metamorphic
Rock, says on pg. 321, "By studying both the processes in present-day
environments and the lithofacies formed by those processes,
sedimentologists are able to infer how similar ancient rocks were formed."
It seems to me that it can be said like this:
1. A Sedimentary Deposition implies a unique Sedimentary Environment,
or SD --> SE.
2. We are able to find Sedimentary Depositions which have similar
lithofacies to Sedimentary Rocks,
or SD ~ SR.
3. We assume that a Sedimentary Rock implies a unique Sedimentary
Environment prior to litification,
or SR --> SRE.
4. Thus we conclude that there existed a Sedimentary Rock Environment that
was similar to a Sedimentary Environment of today,
or SRE ~ SE.
And so geologists spend much time studying the processes of today in-order
to provide a basis for interpreting the sedimentary rock record.
Rock and a known Sedimentary Deposition the more reliable the assignment of
an Sedimentary Environment. It has happened that the interpretation of an
environment has changed. For instance, the Bouma sequences, which had been
interpreted as slow deposition of fines in still water, has since been
reinterpreted as Turbidite deposition (a vastly different, catastrophic
change in environments). It was found that a greater similarity existed
between the Bouma sequences and Turbidite depositions than with the
previously interpreted environment.
The vast majority of sedimentary environments studied today and applied to
sedimentary rocks also apply the same rates of deposition to the rocks.
Thus, by extension, the shear quantity of sedimentary rocks implies a
record of long ages.
There is an increasing awareness that catastrophic events (such as asteroid
impact and explosive volcanism, etc.) are also a part of the geologic
record. As these events and associated environmental impacts are assessed,
depositional facies are determined and studied and the rocks restudied and
their depositional environment reassessed. Of course, there is reluctance
to set aside previous interpretations for an assortment of reasons.
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Just to see if I'm on the same page as =
you let me make a few introductory comments.
Since we were not =
there to see the formation of sedimentary rocks, in order to attempt to =
discover how they were formed (and subsequently lithified), we look to =
analogous depositions occurring now in the world around us. As =
Raymond in Petrology: The Study of Igneous, sedimentary and Metamorphic =
Rock, says on pg. 321, "By studying both the processes in =
present-day environments and the lithofacies formed by those processes, =
sedimentologists are able to infer how similar ancient rocks were =
formed."
It seems to me that it can be said like this: =
1. A Sedimentary Deposition implies a unique Sedimentary =
Environment,
or SD --> =
SE.
2. We are able to find Sedimentary Depositions =
which have similar lithofacies to Sedimentary Rocks,
=
or SD ~ SR.
3. We assume that a =
Sedimentary Rock implies a unique Sedimentary Environment prior to =
litification,
or SR --> =
SRE.
4. Thus we conclude that there existed a Sedimentary Rock =
Environment that was similar to a Sedimentary Environment of =
today,
or SRE ~ SE.
And =
so geologists spend much time studying the processes of today in-order =
to provide a basis for interpreting the sedimentary rock =
record.
From this we can see that the greater the similarity =
between a Sedimentary Rock and a known Sedimentary Deposition the more =
reliable the assignment of an Sedimentary Environment. It has =
happened that the interpretation of an environment has changed. =
For instance, the Bouma sequences, which had been interpreted as =
slow deposition of fines in still water, has since been reinterpreted as =
Turbidite deposition (a vastly different, catastrophic change in =
environments). It was found that a greater similarity existed =
between the Bouma sequences and Turbidite depositions than with the =
previously interpreted environment.
The vast majority of =
sedimentary environments studied today and applied to sedimentary rocks =
also apply the same rates of deposition to the rocks. Thus, by =
extension, the shear quantity of sedimentary rocks implies a record of =
long ages.
There is an increasing awareness that =
catastrophic events (such as asteroid impact and explosive volcanism, =
etc.) are also a part of the geologic record. As these events and =
associated environmental impacts are assessed, depositional facies are =
determined and studied and the rocks restudied and their depositional =
environment reassessed. Of course, there is reluctance to set =
aside previous interpretations for an assortment of =
reasons.