T212 Investigating Coastal Environments: A Tribute to Derald G. Smith (Posters)

Tuesday, 3 November 2015
9:00 AM - 6:30 PM
Exhibit Hall

THE 12-LAKES OF LU FENG, SOUTHERN CHINA: WHERE ARE THE MISSING LAKES? GROUND-PENETRATING RADAR INVESTIGATION OF A COASTAL PLAIN

Paper number: T212-9
Program: Technical Sessions
Time: 9:00 AM – 6:30 PM

Authors

Abstract

The coastal plain around Lu Feng, southern China, was once home to 12 lakes, giving rise to its name “12-Lakes”. The number of lakes has been reduced, so now there are only 6 major lakes. If the former lakes could be located and identified, these depositional features could hold evidence for the former environmental history of the area. Therefore, in June, 2014, we conducted Ground-Penetrating Radar (GPR) studies to investigate the subsurface architecture of the 12 Lakes region to determine if any former lakes could be identified and located. We collected over 15 km of 2D GPR data along unsealed roads and sandy/gravel tracks with Pulse EKKO 1000 100 MHz antennae mounted on a smart sled. Antenna separation was fixed at 1 m and data acquisition was triggered by odometer wheel, with a step size of 0.25 m. CMP data were used to establish near surface velocities for topographic correction and depth estimation. Depth of penetration was good, with maximum depth in the region of 15 m. Topographic and positioning data was collected using a combination of a laser level and a Trimble RTK GNSS system.

Preliminary profile analysis indicates a large system of southerly to southeasterly dipping reflections overlying an undulating, laterally extensive, sub-horizontal reflection. These data are interpreted as a beach system prograding southerly to southeasterly over a bedrock (granite) surface and interrupted by bedrock highs, which occasionally break the surface. Along the most northern profile, the depth to the bedrock surface decreases to the north, reducing from a maximum of 10 m to less than 4 m as a result of bedrock shallowing and reduction in topographic elevation. The main west to east line reveals a section of converging dipping reflections, which delineate an area over 700 m wide and approximately 6 m deep, which is possibly the remains of one of the former lakes. This particular area would be a good target for further investigation including coring to gather sedimentological, environmental and dating evidence.