RE: North Horn Formation and the KT Boundary

[Denver Fowler <df9465@yahoo.co.uk>]

A good summary of the North Horn is given at the start
of:

ROSE L. DIFLEY and A.A. EKDALE 
Footprints of Utah's Last Dinosaurs: Track Beds in the
Upper Cretaceous (Maastrichtian) North Horn Formation
of the Wasatch Plateau, Central Utah 
Palaios 2002 17: 327-346

The Fm is divided into units 1, 2A, 2B, 3A, 3B, 3C.
The K-T boundary is thought to occur between 2A and
2B.

Note that dino remains are well known in the lowermost
unit (1):

"Dinosaur remains (bone and eggshell) occur throughout
Unit 1. Taxa include Alamosaurus, Tyrannosaurus rex,
Torosaurus and other ceratopsians, and hadrosaurs
(Gilmore, 1946; Jensen, 1966; Lawson, 1976; Bray,
1999; Cifelli et al., 1999; Difley and Ekdale, 1999;
Loewen et al., 2001; Difley, unpublished data). Less
common and restricted to scattered levels are other
vertebrates, such as mammals, lizards
(Polyglyphanodon), crocodilians, turtles and fish
(Gilmore, 1946; Cifelli et al., 1999; Difley,
unpublished data)."

but very badly known in 2A (at least at time of
publication):

" Freshwater aquatic fauna (including crocodilians,
softshelled turtles, fish, bivalves, gastropods and
ostracods) are common throughout Unit 2, but they are
relatively abundant in Unit 2A (Difley and Ekdale,
1999). The only identifiable dinosaur skeletal
material in Unit 2A is a small fragment of an
ornithiscian jaw that occurs low in the unit. Based
upon poorly preserved, partial tooth sockets, it
cannot be identified more closely than either
ceratopsian or hadrosaurian (Difley, unpublished
data)."

I've not been to the North Horn personally, but it
sounds very familiar and sinmilar to the Ojo Alamo sst
Fm in New Mexico. This unit also spans the K-T.
Dinosaur fossils are common enough at the base, and a
few metres up form the base, but they are then
essentially non-existent from mid-way into the Fm.
Whether this represents the K-T or not is
indeterminable in the Ojo Alamo.

I've posted before as to the age of the 'Alamosaurus
fauna', so won't go into it again in detail. However,
the evidence for a very latest K-lancian-esque age for
the fauna is less solid, than it being a little older:


http://gsa.confex.com/gsa/2004RM/finalprogram/abstract_72303.htm

here I am making the assumption that Alamosaurus
bearing rocks in TX, UT, and NM are the same age. they
may not be, but the faunas seem awful similar, and
comprise some unique ceratopsians at least:

Farke, A. & Williamson, T. (2005): A chasmosaurine
Ceratopsid parietal from the naashoibito member, Ojo
Alamo Formation of New Mexico, with implications for
ceratopsid systematics and biogeography. Sixty-fifth
annual meeting, Society of Vertebrate Paleontology,
Mesa, Arizona. ? J. Vert. Pal. (3), 55.

and let's not foget Torosaurus utahensis etc..

Whether or not you believe this is evidence of
north-south biozones, or a slight variation in age is
up to you. The evidence is more or less equivocal, and
arguable either way. The North Horn might hold the
answer I suppose.

Denver.



--- Ken.Carpenter@dmns.org wrote:

> The North Horn spans the K-T boundary. 
> The College of Eastern Utah and the University of
> Utah have been working the beds.
> some references:
>
http://gsa.confex.com/gsa/2002AM/finalprogram/abstract_46052.htm
>
http://3dparks.wr.usgs.gov/coloradoplateau/lexicon/northhorn.htm
>
http://www.geo.arizona.edu/geodaze/97/program/thursday/05HaldarJ.5.html
> 
> 
> Ken
> 
> Kenneth Carpenter, Ph.D.
> Curator of Lower Vertebrate Paleontology
> and Chief Preparator
> Department of Earth Sciences
> Denver Museum of Nature & Science
> 2001 Colorado Blvd.
> Denver, CO 80205 USA
> 
> ph: 303-370-6392/ or 6403
> fx: 303-331-6492
> 
> for PDFs of my reprints, info about the Cedar Mtn.
> Project, etc. see:
>
https://scientists.dmns.org/sites/kencarpenter/default.aspx
> for fun, see also:
>
http://dino.lm.com/artists/display.php?name=Kcarpenter
> 
> 
> 
> -----Original Message-----
> From: owner-dinosaur@usc.edu on behalf of Rocky
> Barney
> Sent: Tue 11/8/2005 6:19 PM
> To: dinosaur@usc.edu
> Subject: North Horn Formation and the KT Boundary
>  
> I have looked in every doc that I have access to 
> and cannot find if the KT Boundary is directly above
> the North Horn Formation here in Utah, and if so has
> there ever been any extensive research on it? Is
> there any place on the web that I can go to find the
> info?
> Rock
> 
>               
> ---------------------------------
>  Yahoo! FareChase - Search multiple travel sites in
> one click.  
> 
> 



        
        
                
___________________________________________________________ 
Yahoo! Messenger - NEW crystal clear PC to PC calling worldwide with voicemail 
http://uk.messenger.yahoo.com