Report No. : GEO Report No. 179

Report Title : Updating of Hong Kong Geological Survey 1:20,000-Scale Maps, Major Findings and Revisions Map Sheet 7 - Sha Tin (2010), 44 p.

Author : R.J. Sewell, J.C.F. Wong & R. Shaw

Abstract

There have been many changes in Hong Kong since the first edition of 1:20,000-scale geological maps were surveyed and published by the Hong Kong Geological Survey of the Geotechnical Engineering Office. Consequently, the Hong Kong Geological Survey Section of the Planning Division has embarked on a programme to update the 1:20,000-scale maps and to release them in both printed and digital form. This will make these geological maps more easily accessible to the public, and more useful to engineers and planners.

The map updating work is being digitised on a GIS platform using a standard GIS template, and the maps are being published and disseminated in ArcReader format.

Geological Map Sheet 7 - Sha Tin, surveyed between 1983 and 1984, and published in 1986, is the first of fifteen 1:20,000-scale geological maps to be updated. The ten-year programme of updating gives priority to urban areas. Reliability of the geological maps has been improved after incorporation of the vast amount of new information that has accumulated over the past twenty years, and advances in the understanding Hong Kong's geology since the published maps were first surveyed.

The key findings on, and revisions to, Map Sheet 7 are described in this report. They include: a revision of the stratigraphic nomenclature, a reinterpretation of the onshore and offshore superficial deposits, a revision of the intertidal units and beach deposits, an updated history of reclamation, an improved understanding of magmatic and volcanic events, a revised stratigraphy of the volcanic and sedimentary rocks, and the more accurate location of the concealed major faults and rock type boundaries. A further major improvement is the addition of a solid-only GIS layer, which includes the first interpretation of the offshore solid geology based on geophysical and borehole data, and a large number of additional GIS layers containing geological and related information.

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