SEDIMENT FABRIC AND ANISOTROPY OF HYDRAULIC CONDUCTIVITY IN SANDY TILL, WISCONSIN, USA

The orientation of macroscopic and microscopic particles in silty, san dy basal till appears to have little effect on aquifer anisotropy. The orientation of 108 elongate pebble and cobble-sized particles was mea sured in a trench adjacent to 25 wells screened in the till. In additi on, the orientation of elongate silt and sand-sized particles was meas ured in thin sections of five oriented samples taken from the same tre nch. The orientations of the macro- and microfabric measurements agree with each other and with drumlin orientations in the vicinity. There is no preferential direction of transmissivity (i.e. no horizontal ani sotropy) based on analysis of pumping test data. This is most likely d ue to the relatively small number of elongated, and therefore oriented , particles in the matrix.