Laurent Deschodt

Sédimentologie et datation des dépôts fluvio-éoliens du Pléniglaciaire Weichselien à Lille (vallée de la Deûle, bassin de l’Escaut, France)

The Deule River has scoured the chalk substratum in two places in the vicinity of Lille. The older scouring is under the lower slopes of the Weppes country. It occurred prior to the Weichselian. It was still active in the Early Glacial. A more recent scouring, predating the Upper Pleniglacial, appeared one kilometre eastward. The Hegel street excavations allow direct observation of a portion of the in-filled channel; a 12,5 m thick sandy alluvium deposited in small channels associated with indications of cold. It dated to about the end of the Pleniglacial (17 960 ± 90 BP, i.e. 21 639 ± 361 cal. BP). These deposits gave way to-apparently continuous -fluvio-aeolian formations, bedded and clayey at first, becoming loess-like in the upper strata. According to the C 14 date and to two OSL dates (21.7 ± 1.9 and 23.7 ± 2,0 ka), this silty, primarily aeolian formation seems to have been rapidly deposited (about 21.7 ka?). These first dates of loess upper valley infilling from northern France should be considered with caution. They appear to indicate the simultaneity of aeolian deposit on slope and valley bottoms at the end of the Pleniglacial, earlier than in the sandy valleys of Belgium and Netherlands.

Sédimentologie et datation des dépôts fluvio-éoliens du Pléniglaciaire weichselien à Lille (vallée de la Deûle, bassin de l'Escaut, France)@@@Sedimentology and dating of weichselian upper pleniglacial fluvio-aeolian deposits in Lille (Deûle valley, schelde basin, France)

The Deule River has scoured the chalk substratum in two places in the vicinity of Lille. The older scouring is under the lower slopes of the Weppes country. It occurred prior to the Weichselian. It was still active in the Early Glacial. A more recent scouring, predating the Upper Pleniglacial, appeared one kilometre eastward. The Hegel street excavations allow direct observation of a portion of the in-filled channel; a 12,5 m thick sandy alluvium deposited in small channels associated with indications of cold. It dated to about the end of the Pleniglacial (17 960 ± 90 BP, i.e. 21 639 ± 361 cal. BP). These deposits gave way to-apparently continuous -fluvio-aeolian formations, bedded and clayey at first, becoming loess-like in the upper strata. According to the C 14 date and to two OSL dates (21.7 ± 1.9 and 23.7 ± 2,0 ka), this silty, primarily aeolian formation seems to have been rapidly deposited (about 21.7 ka?). These first dates of loess upper valley infilling from northern France should be considered with caution. They appear to indicate the simultaneity of aeolian deposit on slope and valley bottoms at the end of the Pleniglacial, earlier than in the sandy valleys of Belgium and Netherlands.

Sedimentology and dating of weichselian upper pleniglacial fluvio-aeolian deposits in Lille (Deûle valley, schelde basin, France)

The Deule River has scoured the chalk substratum in two places in the vicinity of Lille. The older scouring is under the lower slopes of the Weppes country. It occurred prior to the Weichselian. It was still active in the Early Glacial. A more recent scouring, predating the Upper Pleniglacial, appeared one kilometre eastward. The Hegel street excavations allow direct observation of a portion of the in-filled channel; a 12,5 m thick sandy alluvium deposited in small channels associated with indications of cold. It dated to about the end of the Pleniglacial (17 960 ± 90 BP, i.e. 21 639 ± 361 cal. BP). These deposits gave way to-apparently continuous -fluvio-aeolian formations, bedded and clayey at first, becoming loess-like in the upper strata. According to the C 14 date and to two OSL dates (21.7 ± 1.9 and 23.7 ± 2,0 ka), this silty, primarily aeolian formation seems to have been rapidly deposited (about 21.7 ka?). These first dates of loess upper valley infilling from northern France should be considered with caution. They appear to indicate the simultaneity of aeolian deposit on slope and valley bottoms at the end of the Pleniglacial, earlier than in the sandy valleys of Belgium and Netherlands.