Re: To Jon Harshman -- re geological column


rmcbane wrote:

Zoe wrote:
So, for somewhere between 35 million to 100 million years, here we
are, living happily among the algae, worms, and jellyfish. We're not
sure how we sprang into existence full-fledged, but thankfully, we
exist.

Apparently, during this Cambrian period, we are living under water,
right? Shallow seas, according to the first link above.

One day sediment is deposited, probably through a flash flood that
washes sediment into the sea, and this sudden influx fossilizes my
neighbor, the trilobite, where he lies there in his freshly made,
unlithified bed. What happens to this layer during the millions of
years before another layer is laid down? And as more layers are laid
down, are they continuously under water, or do they emerge as dry land
for millions of years before being submerged again?

The sediment isn't deposited "one day" and need not be through a flash
flood. Take a look at any river and you will see that there is constant
transport of sediment from land to sea. A good example is the
Mississippi River and the massive sediments being deposited in the Gulf
of Mexico. You seem hung up on the idea that the layers and fossils are
deposited as an event rather than a continuous process.

I think the trilobite experiences an event. If it's buried in sand
then it'll try to get out. If it's dead (for whatever reason, heart
attack) then it will be eaten by microbes. Fossils are the very rare
cases where something is left, but why does that happen at all? Now
the creature being suddenly and thoroughly buried is one credible
mechanism. Another is when it ends up in some abiotic environment - I
dunno, poisonous volcanic emissions, so nothing can get to it to eat
it. And I guess there are cases where it /is/ eaten but it has
arleady left its impression in the future rock. Like the Paluxy
tracks :-)

.

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