IMAGING FLUVIAL ARCHITECTURE USING GROUND PENETRATING RADAR, MAPLE CREEK, GUYANA

A ground penetrating radar (GPR) survey was used to image the fluvial architecture of a buried paleovalley at Maple Creek, Guyana. The survey was part of a larger study that investigated the local stratigraphy of the valley, interpreted the organization of fluvial elements within the valley-fill, and assessed the economic potential of the valley-fill for placer diamonds and gold. The survey consisted of 44 km of survey line collected with 100 MHz antennae in the southern part and 50 MHz antennae in the northern part of the study area. The grid consisted of 28 east-west cross-sections and 6 north-south tie lines. The cross-sections were spaced 100 m and 400 m in the southern and northern parts of the area, respectively. Tie lines were spaced at 500 m intervals. The survey imaged two strong reflectors interpreted to represent major bounding surfaces. The lower surface was confirmed to be the bedrock-sediment interface and thus represents the valley boundary. The second major surface is either a sequence boundary between the fluvial valley-fill and overlying marine sediments or a weathering contact. In addition to the major surfaces, several minor surfaces and their associated internal reflectors were also imaged, resulting in the identification of 21 radar elements. Sixteen of these elements have been interpreted to represent fluvial architectural elements. Four distinct morphological zones are present and are differentiated by variation in the geometry of the bedrock-sediment interface and various assemblages of architectural elements.