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Re: the K-T boundary



At 09:33 AM 7/5/97 -0700, Michael Sternberg wrote:
>What do you mean "have a distinctly modern flavor"?  I'm not picking 
>a fight here, but the Late Cretaceous and Paleocene floras of NA 
>decidely are not modern.  Certainly we see many of the families arise 
>then, but at the genus level not many have modern day correspondents,

I just mean that an ordinary person walking in those forests would not
really be able to tell by general appearance that they were not modern
(while a _Glossopteris_ forest would have looked decidedly odd about anybody).

However, by the Upper Maastrichtian they are extremely similar, at the
genus level, to North American Eocene floras.

And they even compare closely to fully modern floras, just from different
areas: "Dryophyllum", the most common angiosperm, compares closely to
_Castanea_ or _Castanopsis_; and there were forms close to _Platanus_,
_Quercus_, _Rhamnus_, _Ulmus_ and several others present in the flora (even
where not identical at the generic level). -- (Actually I suspect that
_Ulmus_ itself was present, as I have seen both elm-like leaves and
elm-like seeds - not quite identical to modern elm seeds though).

The floodplain forests of the Lance type locality would have looked like a
Chestnut-Mixed Deciduous forest not too different from some floodplain
forests of the modern Mississippi Valley (where Swamp Chestnut Oaks - oaks
with chestnut-like leaves - take the place of "Dryophyllum").

>Don't be bamboozled by the presence of palms and cycads as an 
>indicator of mesothermal climate.  There are a number of extant mid
>to high altitude tropical plants that fit in right at home in cooler,
>lower altitude regions. ...

Hmm, yes, I can see that.  (No cycads I know of in Lancian deposits, and
the palms seem to be restricted to certain sub-habitats)

The fact is that palms go rather further north along the Atlantic coast
than most people realize.

--------------
May the peace of God be with you.         sarima@ix.netcom.com
                                          sfriesen@netlock.com