Hong Kong Geology Guide Book Geotechnical Engineering Office ...

Outline of the Geology
Geological Map of the Tolo Harbour area
(from HKGS 1:100,000-scale Geological Map HGM100)
The Devonian rocks of the Bluff Head
Formation crop out on the northern side of
the Tolo Channel and on the southern side of
Tolo Harbour. Along the northern coast they
occur to the south of Plover Cove Reservoir,
and along the southern coast they occur in
the Ma On Shan area.
The Bluff Head Formation is bounded, to
Devonian quartzitic conglomerate
the north and to the south, by faults. The
Formation, which is over 800 m thick, has
been sub-divided into upper and lower units. Coarse sandstones and conglomerates
interbedded with siltstones make up the lower unit, which contains fossils of bivalves,
ostracods and conchostracans that indicate a Lower to Middle Devonian age. The
upper unit comprises sandstones, conglomeratic sandstones and conglomerates
interbedded with grey siltstones that contain fossils of placoderms, ostracods,
conchostracans and ferns indicating an Upper Devonian age.
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