W.N.Ridley Thomas
W.C. Lai
Electronic & Geophysical Services, Ltd, Hong Kong
A detailed gravity survey in the Yuen Long area to map the shallow limestone subcrop
Abstract
Following the discovery of marble limestone concealed beneath variable thicknesses of alluvium in the Yuen Long area, a detailed gravity survey was carried out to investigate the extent of the subcrops. The survey and the data reduction processes are described generally, and a more detailed account is given of the geological interpretation of the data and of the principal assumptions that had to be made.
The results of the interpretation are shown as maps of the limestone subcrop depths and of the limestone isopachs. The gravity anomaly successfully delineated some of the limestone subcrops that were known from shallow boreholes and by correlation it also identified other areas where the limestone may be present at shallow depths. Several structural trends were also implied by the gravity anomaly.