Kwartire land- en zoetwatermollusken uit een boring bij Brielle, Nederland

Quaternary land- and freshwatermolluscs of a boring near Brielle (Netherlands) Samples of a boring near Brielle (20 km west of Rotterdam, province of Zuid Holland) were taken every meter. These samples, containing about 10 to 40 kg of sediment each, yielded a total of 53 species of land- and freshwatermolluscs (table 1). Important are the samples from 127 to 60 m below surface. The molluscs date this part of the deposits as Tiglian. From 127 to 83 m (top of marine “Icenian”) the land- and freshwatermolluscs are found among marine molluscs and they indicate a regression. From 76 to 60 m a fluviatile deposit (Rhine) is found. Some of the species reached this part of N.W.Europe during warm periods (interglacials), e.g. Lithoglyphus naticoides, Vitrinobrachium breve, Perforatella bidentata, Soosia cf diodonta, Helicigona lapicida. Cf Abida sp., Vitrinobrachium breve, Soosia cf diodonta and Helicigona lapicida were found for the first time in the fossil record of the Netherlands. Semilimax kochi is now known from an interglacial. This is not in accordance with the opinion of e.g. Zeissler (1969, 1971), who thought it to be an indication for glacials. Fragments of Perforatella bidentata look much like Perforatella dibothryon, but they are slightly different. The molluscs of the Tiglian, especially those from around 65 m below surface, indicate a river deposit. A big river was meandering through a wide river valley. In this river valley there were quiet pools and marshy areas. Around pools, marshes and river there were river woods and open plains.