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estuarine evolution

David W Kirtley Ph.D. dwkirtley at igc.apc.org
Thu Dec 14 21:51:40 EST 1995

Jim Blake writes:

<<Geologically, the estuaries of California are so young, that there are 
<<relatively few endemic invertebrates.

This statement needs to be clarified a bit, I believe, before it 
becomes generally and uncritically accepted, embedded, and perfused 
through the literature.

Some of the present day estuaries may have been at their present 
positions for relatively brief (geologic) time spans, indeed, but 
there is little reason to imagine that there were no antecedent estuarine
habitats along the California coast that occupied laterally contiguous
positions during lower, or higher, relative sea level stands.  

Whether as the result of global glacio-eustatic rise and fall of sea-
level or local tectonic vertical displacement and/or lateral translation
of fault blocks, the size and shapes and areal extent of the estuarine 
habitats may have changed greatly  from time to time, but this would not 
completely obviate the opportunity for the evolution of endemic 
invertebrates in those estuarine habitats. 

If there is evidence that at any time the California coastal margin was 
a high, sheer, strait cliff, and all the rivers and streams were dammed 
up so that there was no fresh water flowing into the ocean, then my
argument would be baseless and my conclusions dead wrong.

I think I'll e-mail it out and find out, pronto!


David W. Kirtley
<dwkirtley at igc,apc.org>

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