Regolith 2004 In: Roach I.C. ed. 2004. Regolith 2004. CRC LEME, pp. 260-263. 260 RELATING SURFICIAL REGOLITH-LANDFORM ATTRIBUTES TO 3D REGOLITH ARCHITECTURE: PRELIMINARY THOUGHTS AND CONCEPTS A. Petts & S.M. Hill CRC LEME, School of Earth & Environmental Sciences, University of Adelaide, SA, 5005 INTRODUCTION The depth of the regolith and how this measurement varies across the landscape is a fundamental attribute in the characterisation of the regolith, having many applications in both mineral exploration and natural resource management. The development of efficient, economical and accurate methods for determining the 3D architecture of regolith-dominated landscapes is a major challenge for regolith researchers and their stakeholders. Many of the present approaches used to understand and model the regolith architecture are limited in their widespread application, mostly because of their high costs and in some cases uncertainties with their accuracy. One of the main challenges faced by companies involved in mineral exploration is to effectively explore through significant thicknesses of regolith. Generations of mineral exploration across those parts of minerals provinces with extensive bedrock exposure and shallow cover has meant that companies are now looking at areas of more extensive regolith thickness for 'green-fields' exploration targets. This has led to a reliance on drilling and geophysical methods to determine the thickness of the regolith and depth to basement, both of which can be costly. Recent research by CRC LEME scientists (particularly those based at CSIRO in Perth, e.g., Butt et al. 2001 Butt 2001) have indicated that many surface regolith exploration sampling media have variably reliable abilities to express mineralisation through greater thicknesses of transported regolith. From this research, many mineral explorers typically use transported regolith thicknesses of less than 5, 10 or in some cases 30 m as thresholds for the application of surface regolith geochemistry to express underlying mineralisation. For these explorers the ability to economically and accurately delineate areas of different transported regolith thicknesses would be of great value. In many parts of Australia the close association between regolith and landforms has enabled accurate and efficient mapping and characterisation of surficial regolith materials, much of which has been represented on regolith-landform maps. The extension of this characterisation beyond surface expression, to greater depths, has previously had limited success and has been restricted in its application. There is potential however that some of the attributes of the surface regolith and landscape can allow for efficient and accurate characterisation of regolith at depth. If this potential can be realised then derivative 3D regolith maps may be produced from the understanding and mapping of surficial regolith attributes. A further implication of identifying surficial regolith attributes, that can be linked to subsurface regolith materials, is that this may also help identify chemical connections between the landsurface and buried materials, such as the possible driving processes and mechanisms behind surface geochemical and biogeochemical anomaly formation. This manuscript discusses some of the surficial attributes of the regolith and how they may be related to subsurface regolith materials and their depth. Particular emphasis will be given to ascertaining the depth of transported regolith, which specifically includes the material that overlies variably weathered bedrock and saprolite, however, some of this approach may also have some implications for determining the depth of weathered material (i.e., total regolith thickness). SURFICAL REGOLITH ATTRIBUTES AND THEIR ASSOCIATION WITH REGOLITH AT DEPTH In regolith-landform mapping many attributes may be noted before assigning a regolith-landform unit label to a particular location. In a similar way, a multi-variate approach may be taken to the problem of relating surface and near-surface attributes to the thickness and the subsurface characteristics of the regolith. This manuscript considers three main surficial regolith attributes that shall be defined and developed as an exploration medium and may be closely associated with defining the 'z-parameter' (depth) of the regolith. These attributes include: • surface regolith materials; • landform expression; and, • biota.