Hong Kong Geology Guide Book Geotechnical Engineering Office ...

Outline of the Geology
The Lam Tsuen Valley is a river valley lying between the mountains of Tai To Yan and
Tai Mo Shan. The hills in the Lam Tsuen Valley and its vicinity are underlain by
Middle Jurassic volcanic and intrusive rocks of the Shing Mun Formation and the Tai
Po Granodiorite, respectively. These units are thought to be roughly the same age. The
granodiorite is restricted in outcrop to the southeastern part of the Lam Tsuen Valley.
Originally, the Lam Tsuen River flowed to the north to enter the Shenzhen River.
However, the Lam Tsuen River was later captured by the Tolo Harbour drainage
system and now drains eastwards into Tolo Harbour. The gradient of Tai To Yan is
steep, with numerous streams flowing into the Lam Tsuen River. The mountain ridge
extending from Tai Mo Shan has a more gentle gradient, but the catchment area is
much larger than that of the Tai To Yan. Most of the streams to the north of Tai Mo
Shan enter the Lam Tsuen River. In the past, the Lam Tsuen River formed a rather
large 1.3 km–wide valley which extended for about 5.5 km in a northeasterly
direction.
Topography of the Lam Tsuen Valley area
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