2.1.18. Spiennes Chalk Formation - SPI
Authors: F.L. Cornet & Briart (1870), Robaszynski & Christensen (1989).
Description: A white to whitish-grey, rather coarse-grained chalk, which becomes calcarenitic towards the top. It contains many large black to grey-brown cherts and some black chert bands, 10 to 60 cm thick (used by Neolithic man for tool making). At the base there occasionally is a thin layer of phosphatised chalk pebbles and inoceramid, echinoid and ostreid fragments and sponges; at the top sometimes a burrowed level.
Stratotype: No stratotype has been designated for the Spiennes Formation. Outcrops are occasionally available depending on activities in quarries. A good section exposing the Spiennes Fm. pro parte was studied by Robaszynski & Christensen (1989)
Area: Mons Basin, from Hautrage in the west to Havré in the east, in outcrops and boreholes.
Thickness: 20 to 25 m on the margin of the Mons Basin (e.g. at Harmignies) to 50 m in the centre of this basin in its most subsided zones.
Age: Late Late Campanian: fossil content: cephalopods: Belemnitella minor I Jeletzky, Bt. minor II Christensen; echinoids: Cardiaster granulosus, Echinocorys belgica; benthic foraminifers: Bolivinoides australis (4 to 6 pustules), Globorotalites hiltermanni, Gavelinella voltziana involutiformis, Eponides beisseli...
Remarks: References: F.L. Cornet & Briart (1874); J. Cornet (1923); Leriche (1935); Marlière (1936a, b, 1957); Robaszynski & Christensen (1989); Kennedy (1993); Robaszynski (1995); Christensen (1999).
Legend : Creamy coloured granular chalk containing many black flints, characteristic for the Spiennes Chalk Formation. Petit Spiennes neolithic underground quarry, UNESCO World Heritage (photo M. Dusar).