Distribution and composition of till on Wieringen and in the northern part of the Wieringermeer, The Netherlands

Abstract

The former island of Wieringen is part of a series of low ridges along the southern margin of the till plain in the northern Netherlands. Distribution and variations in thickness of Saalian till on Wieringen and in the surrounding area suggest that some of the low hills of Wieringen are ice-pushed ridges and that a major glaciotectonic basin is located to the south of Wieringen, in the northern part of the Wieringermeer. Compositional characteristics of till indicate the presence of at least two main till types, one in which both flint and smectite are absent and another in which these components are present. An intermediate type contains very little flint but appears to have no smectite in the clay fraction. The flint-poor till is of the Voorst type and belongs to the First Baltic Till as defined for the northern Netherlands. It is suggested that the present morphology of Wieringen shows features related to two phases of glacial overriding of the previously formed ice-pushed ridges. Firstly, ice moved in a southwestern direction, after formation of the ice-pushed ridges. During a later phase of glaciation, ice moved between Wieringen and Gaasterland in a south-southeastern direction towards the Gelderse Vallei in the central Netherlands. During the latter event, streamlined landforms on eastern Wieringen and western Gaasterland obtained their NNW-SSE orientation. These ice-flow phases can be correlated with ice movements in the northeastern Netherlands, where ice moved first in a southwesterly direction over the till plain and later in a southsoutheastern direction in the Hondsrug area.