THE BIVALVES OF THE SPILSBY SANDSTONE FORMATION AND CONTIGUOUS DEPOSITS
Abstract
Hitherto the bivalve fauna of the Spilsby Sandstone and contiguous
deposits including the lower part of the Sandringham Sands and Speeton
Clay of-Middle Volgian to Ryazanian age has been inadequately described.
As a consequence of this study 92 taxa have been recorded. 45 of these
are described fully and include 13 new species and one new subgenus.
Information has been obtained from the author's collecting and from museum'
collections. Locality and section information is given for sites examined
by the author. The preservation of the fauna is normally as moulds, but
cold cure silicone rubber has been used to obtain casts with great success.
The ecology of the less well understood bivalves is discussed.
Five bivalve dominated assemblages are recognised. They represent various
shallow marine facies. The sediments include glauconitic sands and silts
with condensed sequences containing phosphatised nodules and also a
sideritic ironstone occurs. A facies model is produced for the East
Midlands Shelf, and the contemporary relationships with other parts of
England are discussed. The Spilsby basin represents a westerly embayment
or estuary of the Southern North Sea basin. In Middle Volgian times there
were marine connections to the Wessex basin to the south, but with the
subsequent draining of this latter area in Upper Volgian to Ryazanian
times to restricted marine, brackish and freshwater lagoonal environments,
open marine connection ceased. The Spilsby basin remained fully marine
during these times, but became more enclosed.
The Spilsby bivalve fauna indicates strong faunal similarities
with Boreal regions, and in particular with East Greenland and the Russian
Platform. The fauna also compares closely with the sandy Upper Kimmeridgian
facies in central England but contrasts strongly with the contemporary
faunas of the Portland and Purbeck Beds. The relationships of the Spilsby
fauna with other Boreal regions and with Tethyan Europe are discussed.
Authors
Kelly, Simon Richard AppletonCollections
- Theses [4125]