Landbridges and the Pacific

John Grehan jrg13 at PSU.EDU
Tue Sep 28 02:35:18 CDT 1999

>Please entrain, for me, data which connects the Hawaiian Islands to the
>U.S. west coast via a land bridge...Croizat had no problem imagining this.

I doubt I can be very entertaining, and since Fred makes no specific citation
for me to evaluate, I will quote below a reference to Hawaii by Croizat 1958,
vol 1, p. 798 (truncated to save on typing).

Fig. 114. A diagramatic rendering of Pacific palaeogeography such as is demanded
by dispersal of "modern" type. Land connections are essentially required
west, north and east...sector 1...answers an "insular block" within the
general perimeter
Samoa-Tuamotus-Hawaii that was in the competent past...contained sizeable cores
of land...Note This map is not intended to give body to hypothetical
"landbridges". It
stands for a minumum of biogeographic requirements, nor is it implied, even
that everything...was of "continental" mass and proportions.

It seems to me that Croizat, here at least, was being cautious about the
nature of
former land in the Pacific and was not plunging into a miscellany of land

Geologists acknowledge the Pacific as complex, and certainly controversial.
It seems
that biogeography might shed more light on Pacific paleogeography than
geologists are able from surving geological formations.

>Obviously continental rafting is responsible for a lot of currently
>disconnected distribution.  The problem seems to be that Croizat seemed to
>think just about anything (maybe all) might be explained by vicarience.

I recall Croizat using this term once in the 1970's. He may have used it more
than once, but if so, it was very rare.

>Panbiogeography today, is, correctly, a lot less ridged,

Really! In what way? This is interesting.

and my argument is
>with thinking that everything Croizat wrote is defendable.  A lot of it is

Perhaps. What is or is not defendable is an issue at the core of current
Methods and predictions that have been dismessed as indefensible in the past
has since been shown to be otherwise, so its a fluid situation. Mayr once
said that
since Croizat was wrong about Galapagous how could be be right about anything
else? And yet Croizat's geosynclinal hypothesis corresponds with island arc
tectonic models for the eastern Pacific.

John Grehan

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