ancient seas

[Marc Weiss]

If you could answer these questions it would help with article I'm writing
(for hobby press, not peer reviewed). I won't quote you unless you want me
too and it can be a "generally accepted" type of answer: It is a given
that the (mineral) chemical composition of the sea is homgeneous world
wide.

1-At what point in  time did the sea "stabilize" to some approximation of
this chemical proportion that we have today?

2-At what point in time did the scleratina (or other "modern" reef benthos
for that matter) come into being?

Thanks if you can answer or refer me to one.

best,
Marc