They are not fossils. They are most likely calcareous concretions from  what
biostratigraphers call "sedimentary condensed sections"; I have been able to
see these usually giant concretions embedded in  dark shales in most
geologic sections of  the Cretacic/ Tertiary age boundary in Eastern
Venezuela where geologic correlations to find oil reservoirs are usually
done; the shales - and not the concretions- usually contain a lot of deep
water fossil remains, such as forams, nanoplankton and mollusks, sometimes
it is possible to find large, flat inoceramids which are bioindicators for
age  and basin depth correlation of the stratigraphic unit.
Cheers,
Amanda Diaz
----- Original Message -----
From: peter j harries <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, April 24, 2001 2:21 PM
Subject: Re: Giant Shells in Peru's Andes


> The structures are almost surely concretions and certainly not
> inoceramids.  Although inoceramids have all the features David
> Campbell discussed, the large members of the family are all extremely
> flat forms ; ie, they could never the degree of inflation shown in
> the pictures.
>
> Cheers, Peter Harries
> --
>
____________________________________________________________________________
__
> Peter J. Harries                                        Tel: (813)
974-4974
> Dept. of Geology                                        Fax: (813)
974-2654
> University of South Florida
> 4202 E. Fowler Ave., SCA 528
> Tampa, FL  33620-5201