Re: BARYONYX (Stratigraphy)

["Dr C.J. Underwood" <cju@liverpool.ac.uk>]

> 
>  Shared with...no extant theropods. *Baryonyx* seems to be the lone 
>theropod in this time frame, which would somewhat explain why he grew so 
>big: no competition.>>
>
>Felix Landry points out:
>
><Mmm... What about Becklespinax, Neovenator and Valdoraptor. Are they 
>from the Barremian?>
>
>An earlier post from Tom, which I forgot to post to the list. Mentions 
>*Neovenator*. This was at first humbling, but the notes I have state 
>that Hutt, Martill, and Baker [1997] put the Isle of Wight as Aptian, 
>while others have put it as Barremian. The exact age of the Wealden F. 
>is as cloudy as the Nemegt and Djadohkta Formations, so could be 
>anywhere from Barremian to Aptian, so I should have taken this into 
>consideration. Fossils from the Isle of Wight that may be *Baryonyx* 
>come from the younger strata that housed *Neovenator*, but this is only 
>a slight possibility. Bary's age is thus listed by me as 
>~Barremian/~Aptian, so *Becklespinax*, *Neovenator*, and *Valdoraptor* 
>may all be contemporaries of Bary, and I was in error on my statement 
>earlier.
  As far as I am aware, the wealden of the Isle of Wight is about as
well constrained as any non-marine rocks can be. The lowest rocks
exposed are on the intertidal platform at Brook Point are contain palyno
material suggesting that they are U Hauterivian.The overlying Wessex
Formation (overbank muds and channel sandbodies that have yielded almost
all of the dinosaur material) contain palynomorphs suggestive of the
Barremian. The vectis Fm above this (mostly shales with samll coarsening
upwards sands, mostly freshwater but sone marine influence near top)  
has yielded some dinosaur stuff (including one of the -Polacanthus_
specimens). The base of a large sandbody within this (Barnes High Mbr)
MAY represent the 113Ma sequence boundary of the Exxon Curve i.e.
Barremian, bidentatum Zone. The Wealden is overlain erosively by the
base of the marine
Atherfield Clay of basal aptian, obsoletus Subzone age. The bodei SZ at
the base of the Aptian therefore is either absent, being taken out by
the erosion surface, or is represented by the uppermost extreme part of
the Vectis Fm. It it possible that the increase in marine faunas within
the top couple of metres of the Vectis represent the widespread
sea-level rise in the lower part of the bodei SZ. 
(The Wealden of the mainland, incidently, starts in the Berriasian or
Valanginian, following on from the non-marine carbonates of the Purbeck
Group which are Upper Tithonian to Berriasian in age. )

 Charlie