Genesis of clay lamellae in golf course soils of Mississippi, USA

•Clay lamellae were observed in engineered golf course soils of Mississippi, USA.•We proposed three pedogenic hypothesis to explain the formation of the lamellae.•The clay was likely present at the time of construction and was translocated downwards.•Clay accumulated at boundaries of sand over gravel where water was preferentially retained.

Clay lamellae have been observed in the sand putting green soils of a golf course in Mississippi, USA. These lamellae result in reduced water infiltration, saturated soils, and a decline in turfgrass density. The soils featured an A horizon of 4 to 5 cm, mixed A/C horizons of approximately 10 cm, and C horizons of about 30 cm over gravel. The soils were constructed in 2005 with 90% (quartz) sand and 10% (by volume) sand-sized calcined clay over 10 cm of gravel, which was constructed on a subgrade of compacted native soil. Clay lamellae were commonly observed at the interface of sand and gravel, with the exception of a soil profile directly above a drain pipe. Clay contents in the lamellae ranged from 0.10 to 3.8%. We proposed three hypotheses to explain the formation of these lamellae: 1) clay was present in the sand as a construction contaminant and subsequently moved downward, 2) clay originated from the breakdown and subsequent translocation of a calcined soil amendment that was used to construct the soils, or 3) clay from the underlying compacted subgrade moved upwards through the gravel and into the sand. In each hypothesis, clay accumulated at the boundary of sand and gravel due to preferential retention of water in the sand above the gravel. X-ray diffraction showed that the lamellae contained kaolinite and quartz, whereas the calcined soil amendment contained illite and no kaolinite. The underlying subgrade soil contained kaolinite, quartz, and hydroxy-interlayered vermiculite. Discriminant analysis of X-ray fluorescence spectra showed that the clay fractions of these three different samples had unique chemical fingerprints. These findings suggest that the lamellae did not likely originate from the calcined soil amendment or the subgrade soil. We propose that they originated from clay that was initially present in the sand, which was translocated downwards. This study provides evidence for formation of lamellae in < 10 years, and provides an example of accelerated soil formation due to anthropogenic factors.