Stratigraphy: Early Cretaceous volcanic rocks with ages of approximately 141.1 ± 0.2 million years before present.

Distribution: The Kau Sai Chau Volcanic Group (undifferentiated) occurs as a narrow, east-striking outcrop in the southern end of the Clear Water Bay Penisula, and as a small outlier at the summit of Lantau Peak.

Lithology: Dominantly eutaxitic block- and lapilli-bearing vitric tuff with minor flow-banded rhyolite lava.