Hong Kong Geology Guide Book Geotechnical Engineering Office ...

Comments
In addition to extensive exposures in the northern New Territories, the Carboniferous
sedimentary rocks of the San Tin Group are also present below Yuen Long and Tin
Shui Wai, and along the eastern side of the Tuen Mun Valley. The San Tin Group
carbonate rocks occur offshore on the northern side of Lantau Island. There, they are
entirely covered by Quaternary superficial deposits, having been proven by drillholes.
The carbonate rocks (now metamorphosed to marble) of the Yuen Long Formation are
soluble, resulting in the formation of solution cavities that have had important
consequences for designing and constructing building foundations in the area.
The graphite bearing siltstone and graphitic schist exposed on The Brothers islands to
the north of Lantau Island belong to the Mai Po Member of the Lok Ma Chau
Formation. Detailed studies have concluded that the Lok Ma Chau Formation was
deposited in a prograding delta (Lai et al., 1988). A prograding delta is one that
extends progressively seaward from a river mouth. Sandstone, conglomeratic
sandstone, and conglomerate are typical deltaic sediments. In contrast, evidence
suggests that the fine sandstone, siltstone and carbonaceous layers of the Mai Po
Member were deposited in a near-shore tidal flat or on the alluvial plain of a delta.
References
Allen, P. M. & Stephens, E. A. 1969. Interim report on the Geological Survey of Hong
Kong. Overseas Division, Institute of Geological Sciences, London, 133 p.
Allen, P. M. & Stephens, E. A. 1971. Report on the Geological Survey of Hong Kong.
Government Printer, 107 p. plus 2 maps.
Atherton, M.J. & Burnett, A.D. 1986. Hong Kong Rocks. Published by the Urban
Council, Hong Kong, 145 p.
Bennett, J.D. 1984b. Review of Hong Kong Stratigraphy. GCO Publication No. 5/84,
Geotechnical Control Office, Hong Kong, 62 p.
Chan, M.C. 1987. Petrography of the Lower Carboniferous San Tin Group, Hong Kong.
Geological Society of Hong Kong Newsletter, v. 5, no. 2, pp 9 - 15.
Davis, S.G. 1952. The geology of Hong Kong. Government Printer, Hong Kong. 231 p.
plus 14 plates & 3 maps.
Fletcher, C.J.N., Campbell, S.D.G., Busby, J.P., Carruthers, R.M. & Lai, K.W. 1997.
Regional tectonic setting of Hong Kong: implications of new gravity models.
Journal of the Geological Society, v. 154, pp 1021–1030.
Frost, D.V. 1992. Geology of Yuen Long, Hong Kong Geological Survey Sheet Report
50