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Re: Obnoxious Oceans [



Augustus T. White wrote:
> 
> -----Original Message-----
> From:   Jim Kirkland [SMTP:dis@gj.net]
> Sent:   Thursday, August 20, 1998 11:34 PM
> To:     Dinosaur Listserver; chris.lavers@nottingham.ac.uk
> Subject:        Re: Trying to UN-falsify the bolide
> 
> <<suggest volcanic origin. Sea levels were near the Cret. Peak and we
> enter an Oceanic Anoxic event at this time. The floodplain was flooded>>
> 
> I've seen a good many references to ocean anoxic events in connection with
> various mass extinctions.  What kind of factors are invoked to explain
> them?
> 
Today deep water is cold(carries more o2). Without ice caps, deep ocean
bottom water is warm saline water from the low latitudes (warm water
carries less O2). During high stands in sealevel evaporitic basins are
flooded leading to less ne bottom water. Deep ocean goes anoxic and
oxygen minimum zone rises spilling over onto shelves and interior seas.
Great source rock for oil (much studied). Two big episodes of this
happened during "middle" Cretaceous (in Albian and at end of
Cenomanian). 
        Nothing like this occurred at end of Cretaceous.

Jim K.