Stratigraphy: Late Cretaceous sedimentary rocks.

Distribution: The Kat O Formation crops out in scattered areas at the northern tip of Crooked Island, on Robinson Island, Ap Lo Chun, Sai Ap Chau, Pak Tun Pai, Ledge Point and North Point. The formation is exposed at the coastline of Lau Fau Shan, and occurs in offshore Deep Bay.

Lithology: Dominantly calcareous breccia, conglomerate and corase sandstone.

Depositional Environment: The sedimentary rocks of the Kat O Formation are interpreted as a talus deposited at the foot of a faultscarp under a semi-arid to arid paleoclimate.

(Conglomerate and coarse sandstone of the Kat O Formation, Robinson Island, northeastern New Territories)