(Re)deposition of loess in southern Limbourg, The Netherlands. 2. Micromorphology of the lower silt loam complex and comparison with deposits produced under laboratory conditions

Abstract

AbstractIn this second of five papers on conditions and processes associated with loess accumulation in the southern Netherlands, micromorphology has been used first to characterize deposits ascribed to eolian, fluvial, overland flow, and masswasting processes, and second to recognize features characteristic of deposits produced by simulated processes using comparable testing materials (Mücher and De Ploey (1977); Mücher et al. (1981)).The present paper deals with two stratigraphic units of the Lower Silt Loam complex in the Nagelbeek excavation. These are the Saalian Lower Silt Loam A (unit IV). which seems to consist of eolian material, reworked by sheetflow and modified by Eemian pedogenesis, and the Early Weichselian Lower Silt Loam C (unit VIb), which probably results from channel flow deposition and local masswasting followed by sheetflow deposition. Microscopically, lamination in unit IV suggests alternating eolian conditions and deposition from laminar to smooth turbulent afterflow or meltwater flow. Then followed a period in which deposits of rainwash with smooth turbulent flow, alternated with very thin deposits from laminar flow without splash. Unmodified eolian deposition, or colluviation from splash alone, becomes more dominant upwards. Sedimentary lamination has been accentuated by pedogenic clay illuviation.Unit VIb starts with reworked pedorelicts from Eemian and Early Weichselian paleosols, deposited from rainwash with smooth turbulent flow. Lamination resulted from smooth turbulent to laminar flow without splash. This is followed by intercalations originating from either eolian deposition or splash deposition, and overland flow deposits with evidence for a finely‐branched system of very small rills. Microscopic examination of lobate portions of mass movement deposits within unit VIb does not confirm this origin because of the scale limitations of thin sections. It merely reveals structures that predate the mass movement.