Orogeny posts a challenge
**Show me where a younger deposit is beneath an older deposit in that diagram, **
Obviously there is confusion over terms. It mainly concerns beneath and below. Let me clarify.
A particle is beneath another particle if the top particle is touching the bottom particle. For example my head is beneath my hat (they are touching). The contrary of beneath is on top.
A particle below another one means that if you draw a horizontal line, any particle below the line is below any particle above the line. They can be miles apart. For example if I live up a hill, all those in the valley are below me. The contrary of below is above.
Another term which seems to be misunderstood is upstream and downstream. The words imply that there actually was water, flowing with a current. The current coming from upstream and goes to downstream.
In the light of this terminology letâs see what the experimental data of Guy Berthault shows.
First, it should be noted that it Berthaultâs study of rock formation takes into account the paleohydraulic conditions of strata development.
Let us look at this simple animation:
Fig 1: Sediments are being deposited.
The sedimentary particles are sorted out according to size and water conditions.
Two strata are being formed: the one above and the one below.
In the one above particle A is deposited at time t1.
Fig 2: The strata continue forming downstream at time 2.
Note that particle B (shown in the next figure) has not yet deposited,
particle A however is already aging.
Fig 3: A sedimentary particle B is deposited at time t3 in the lower bed.
It was deposited after particle A.
It is clear is that particles downstream in the lower bed were actually deposited after particles in the upper bed.
Parts of the strata below (B) are younger than parts of the strata above (A).
To se the whole sequence click on the following URL
gberthault.googlepages.com/strata.swf
Once the water has gone only the strata can be seen. Unless the direction of current is known, upstream cannot be determined from downstream and we have no way of knowing whether A was deposited before or after B.
The strata are of no help. This is where Guy Berthault`s work challenges the principle of superposition. It shows why no chronological conclusions can be drawn from strata alone. Based on the superposition principle, B would be wrongly said to be older.
The prinicple of superposition to which Berthault is referring is the standard one defined in the American Geological Institute Glossary of Geology as:
**âA general law upon which all geologic chronology is based: in any sequence of sedimentary strata (or of extrusive igneous rocks) that has not been overturned, the youngest stratum is at the top and the oldest at the base; that is, each bed is younger than the bed beneath, but older than the bed above it. The law was first clearly stated by Steno (1669).â **
(In his publications Berthault referred to Steno in the same way as the AGI).
Here is the visual version:
classzone.com/books/earth_science/terc/content/investigations/es2903/es2903page03.cfm
I hope this helps.
Peter
Havenât we?
What else could that mean? And I guess that you canât account for aeolian deposits or evaporites or carbonates, but I know that you will tell me that is for someone else to research.