1997 No. 52 Part 1 - Bedfordshire Natural History Society

Bedfordshire Naturalist for 1997, No. 52 (Part 1) (1998)
each visit it became necessary to dig away an ever-increasing quantity ofGault, particularly
as the year progressed, creep and slumping ofthe clays becoming a serious problem.
As in most sqft sedimentary rocks the majority offosslls in the clays are. crushed by
pressure and are uncollectable except as impressions in matrix. "Solid" preservation of
fossils, particularly· ammonites in the junction beds, are in the form ofphosphatic casts
and represent a small proportion ofthe fauna. Many are imperfectly preserved, being
fragmentary and forming part ofa gritty nodule; some are part-phosphatised with one
side only being preserved uncrushed. Many specimens occurring in the junction beds
consist ofbody-chambers only, the inner whorls and phragmocones being represented
by impressions or crushed remnants in the clay. An example ofsuch body-chamber
preservation is illustrated in the 1996 Report (Fig. 1, a - c), and species with
compressed whorls such as Cleoniceras and Beudanticeras appear to be particularly
vulnerable in this respect. Casey (1960-1980, p xxxiv) describes a method by which
the complete form ofa part-phosphatised ammonite can be reconstituted, but his
examples refer to those in relatively hard rocks including phosphorite.The Recorder
has had no success in his attempts to reconstitute part-phosphatised specimens from the
Leighton Buzzard Albian clays.
The rare ammonites from Beds 3(i) and 3(ii) ofthe temporary section in Chamberlain's
Barn pit, and subsequently presented to the Natural History Museum are:
(a) Cleoniceras (Cleoniceras) aff. seunesi Bonarelli (BMNH- CA 1688)
Cleoniceras (Cleoniceras) Spa (BMNH CA 1686)
(b) Cleoniceras (Neosaynella) sublaeve (Casey) (BMNH CA 1685)
(c) Cleoniceras (Cleoniceras) dimorphum Casey (BMNH CA 1682)
(d) Cleoniceras (Cleoniceras) seunesi Bonarelli (BMNH CA 1683)
Cleoniceras (Cleoniceras)jloridum Casey (BMNH CA 307)
Protanisoceras (Protanisoceras) acteon (d'Orbigny) (BMNH CA 1687)
Protanisoceras (Protanisoceras) blancheti (Pictet & Campiche) (BMNH CA 1689)
Single specimens only were obtained ofthese species as listed, the Natural History
Museum Register numbers being shown in parentheses. It is ofparticular interest that
hitherto the distribution of (a), (b), (c) and (d) in the OK has not included the
Leighton Buzzard district, the distribution of (a) and (d) being Kent and Surrey; (b)
Kent, Surrey and the Isle ofWight; and (c) Kent (Casey 1960-1980,553-574).
In addition to the listed species, three small well preserved specimens of Beudanticeras
arduennense Breistroffer and one Douvilleiceras orbignyi Hyatt were collected during the
year from this same temporary section, the first record ofthese two species made by
the writer from the Gault-Woburn Sands junction beds in Chamberlain's Barn.The
importance ofthis assemblage is that in addition to updating the ammonite
biostratigraphy, it provides valuable confirmation ofthe continuing variability ofthe .
Gault-Woburn Sands junction beds in Chamberlain's Barn pit, such variability already
being demonstrated in sections further north and west by, principally, Lamplugh &
Walker (1903); Lamplugh (1922);Wright &Wright (1947); Casey (1961); Owen (1972)
and Smart (1977).
The Gault clays above the junction beds were also investigated regularly, particularly
with regard to vertebrate remains. Such fossils are generally uncommon and no reptilia
were noted. Several teleost and shark teeth were collected from the middle Hoplites
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