Analysis of lineaments and their relationship to Neogene fracturing, SE Viti Levu, Fiji

Abstract

The Fiji archipelago lies along a complex active section of the Pacific and Australian plate boundary zone in the SW Pacific. The availability of a range of remotely sensed imagery and recent field studies have permitted the exploration of the link between lineaments as seen on such imagery and tectonic fractures observed on the ground in SE Viti Levu, the main island of Fiji. Comparisons of statistical orientation peaks as well as the spatial extent of lineaments with field-mapped fractures indicate that the lineaments are largely a reflection of tectonic fractures in the bedrock emphasized on the surface by topography, drainage, and vegetation. Surface lineaments correspond to broad zones of intense fracturing and strongly influence the landform features of the area. It appears that surface fracture sets are open-upward splay zones that merge downward into single planar discontinuities, represented by sparse uninterrupted magnetic lineaments at depth. Fault-correlated lineament sets extend over greater geographical distances than the equivalent mapped fault zones, and these lineament sets represent more complex regional structural patterns than previously known. This study provides an approach to mapping fracture patterns where outcrop is limited and where conventional field-mapping techniques of structural geology are impractical. It highlights the benefits of mapping lineaments from multiple sets of remote-sensing imagery of the surface and bedrock, mapping them at regional and larger scales, as well as linking lineaments to detailed field-mapped structures. Lineament data derived using such an approach can be used effectively to characterize regional structural patterns, which in turn may provide better understanding of the structural and tectonic evolution and seismic hazards of the region. This approach may also find useful application in groundwater, mineral, and oil and gas exploration.