De bodemgesteldheid van Noord-Kennemerland

Extraction of drinking water from the dunes in North Kennemerland had caused a permanent fall in watertable in the dune area, impairing the suitability of originally valuable soils for horticulture. At the request of the provincial government of North Holland, this area and adjoining polders were investigated. The study of profiles and fossil gley horizons allowed assessment of former water tables and provided data for the plan to replenish the reserve of fresh water by surface water from the rivers in the central parts of the coastal dune area of the Netherlands. North Kennemerland consists of old dunes (beach barriers or ridges), young dunes, peat and marine deposits. After the formation of the old marine sand and beach ridges (4000-2000 B.C.) the sea broke in and deposited sandy inland deltas (300 B.C.) After reconsolidation of the shore banks, peat started to grow again, till a new transgression (4th-9th century) caused the deposition of the 'knip' clay, which was superficially eroded two centuries later (shallow inland lake-formation). The properties of this clay were studied and yielded a theory on genesis. The absence of CACO ₃ , brackish water and high adsorption of Mg <sup>2+</SUP>seemed to be responsible for the formation of this compact sticky and poorly structured soil