Twenty-three vertical open RC drillholes with a total penetration of 2663 m were drilled by MESA during February and March 1995 along four W-E traverses in the Stonefield area near Truro, to determine bedrock geology and geochemistry below sedimentary cover. This program formed part of the South Australian Exploration Initiative (SAEI). The sites selected by MESA for drilling were chosen in an attempt to upgrade their mineral potential, following the promising outcome of a potential field survey and geophysical appraisal of the surrounding Sandleton 1:50 000 mapsheet area which had previously been conducted by the SADME Geophysics Branch during 1991. The results of the Department's SAEI-funded drilling done at Stonefield outlined widespread anomalous bedrock geochemistry. The uppermost basement section penetrated there comprises Neoproterozoic metasediments intruded by Delamerian granitoid rocks, and it is overlain by un-metamorphosed Tertiary sediments. Locally, in proximity to I-type granitoid intrusions, greenschist facies metasediments have been hydrothermally altered in many places, with pervasive sericitic microfracturing, or have been contact metamorphosed to form skarn rocks. Anomalous Ni (500 ppm) and Zn (620 ppm) were recorded from metasediments in hole STO 8, while an average grade of 56% Fe2O3 was recorded in hole STO 15 from 128-153 m depth. Un-metamorphosed Tertiary sediments have also been subjected to a low temperature sulphide-forming event. Arsenic values are elevated to >200 ppm As within the Murray Group Limestone in several drillholes - this unit may be acting as a geochemical trap for this element.