The information on this page is a summary description.
The full formal description is available here: Saint-Vaast Chalk Formation
| Abbreviation | SVA |
| Parent unit | Chalk group |
| Child units | |
| Lithological description | White togreyishchalk, containing clay minerals but notmarly, difficult to break. The lower part (“Craie de Saint-Vaast inférieure” auct.) contains sponges and grey to black flints but only in the eastern part of the Mons Basin. At the base, a thin conglomerate with phosphatised chalk pebbles, phosphatised and glauconitised sponges and glauconitic grains. The upper part (” Craie de Saint-Vaast supérieure” auct.) is not flinty but chalky with pyritic spheroids. The top is sometimes marked by a hardground. Sponges are more abundant than other fossils. |
| Age | The lower part of the St.-Vaast Fm. is of Coniacian age on the basis of: Micraster decipiens, Volviceramus involutus, the foraminifer Dicarinella gr. concavata. It also contains numerous specimens of Hyotissa semiplana. The upper part of the St.-Vaast Fm. is of Santonian age on the basis of: Micraster coranguinum, Actinocamax verus, Gibbaster belgicus, Sphenoceramus digitatus, and foraminifers: Stensioeina exsculpta gracilis, Gavelinella clementiana, Bolivinoides strigillatus… |
| Thickness | 15 to 25 m on the southern and northern margins of the Basin, about 50 m on the eastern margin near the village of Trivières. |
| Area of occurrence | Mons Basin. The upper part seems to be transgressive over the lower part of the Saint -Vaast Fm. or the Maisières Fm. or Devonian bedrock. |
| Type locality | Stratotype: The quarry at St. Vaast where the Craie de Saint Vaast was originally defined has been filled in. Still visible in the old quarry des crayères at Thieu. |
| Alternative names | |
| Authors | Robaszynski, F., Dhondt, A.V. & Jagt, J.W.M. |
| Date | 01/01/2001 |
| Cite as | Robaszynski, F., Dhondt, A.V. & Jagt, J.W.M., 2001. The Saint-Vaast Chalk Formation, 01/01/2001. National Commission for Stratigraphy Belgium. https://ncs.naturalsciences.be/lithostratigraphy/Saint-Vaast-Chalk-Formation |
| Additional information | At this moment (2000) there are no good outcrops exposing the Saint-Vaast Chalk Fm. Reference: Godfriaux & Sigal (1969). |
