Introduction of the Boxtel Formation and implications for the Quaternary lithostratigraphy of the Netherlands

Abstract

Application of the traditional lithostratigraphic framework to subdivide theMiddle- and Upper-Quaternary locally-derived fine-grained deposits in theNetherlands is problematic. Deposits of many formations cannot bedistinguished from each other based on lithological characteristics andstratigraphie position alone. To overcome this problem, we present a new,well-defined lithostratigraphy for these deposits, based on detailedresearch in the central part of the Roer Valley Graben. This area containsan up to 35 m-thick sedimentary record of Middle- and Upper-Quaternary sand,loam and peat deposits. These have mainly been formed by aeolian andsmall-scale fluvial processes and have been preserved as a result oftectonic subsidence. The traditional lithostratigraphic subdivision of thesedeposits into three formations (Eindhoven Formation, Asten Formation andTwente Formation) was based on a combination of litho-, bio- andchronostratigraphic evidence and the presumed widespread presence of ahorizon of organic-rich interglacial sediments of Eemian age. To avoidintermingling of criteria regarding lithological characteristics, genesisand age, we now incorporate all fine-grained sediments into the new BoxtelFormation. The implications for the lithostratigraphic framework in otherparts of the country are explored and discussed. Eight lithostratigraphicmembers are introduced that describe the most characteristic parts of theformation. To fully illustrate the sedimentary sequence in the Roer ValleyGraben, two new members are defined here. The Best Member incorporatesalternating floodloam deposits and sandy aeolian deposits in the lower partof the Boxtel Formation. The Liempde Member includes reworked aeolian loessand sandy loess deposits (‘Brabant loam’) that occur in the upper part ofthe sedimentary sequence.