page_title: Geology of Hong Kong
section_title: Ma Shi Chau
hierarchical_section_title: Geology of Hong Kong / Sedimentary rocks / Ma Shi Chau
caption_attribution_description: English: A fold on Ma Shi Chau, Hong Kong. Red are the limbs, blue line marked the axis
context_page_description: The geology of Hong Kong is dominated by igneous rocks formed during a major volcanic eruption period in the Mesozoic era. It made up 85% of Hong Kong's land surface and the remaining 15% are mostly sedimentary rocks located in the northeast New Territories. There are also a very small percentage of metamorphic rocks in New Territories. These are formed by deformation of pre-existing sedimentary rocks which changed its mineral assemblages.
  The geological history of Hong Kong started as early as the Devonian period which is marked by the discovery of Placoderm fossils in northeast Hong Kong. While the youngest rocks in Hong Kong are formed during the Paleogene period. They are today exposed in Tung Ping Chau in northeast Hong Kong.
  Each of the three types of rocks: igneous, sedimentary, and metamorphic rocks formed spectacular geological features in Hong Kong. Igneous rocks formed the hexagonal columns in Sai Kung. Sedimentary rocks formed various erosion features such as wave-cut platforms and sea stacks in Tung Ping Chau. Metamorphic rocks formed the iron ore deposits in Ma On Shan. Each of these will be introduced in later sections.
context_section_description: Ma Shi Chau is a tidal island in the Tolo Harbour in northeast New Territories. It is an important special area for geological studies. It contains rocks from three different formations: Permian sedimentary rocks, Early Cretaceous volcanic rocks and middle Cretaceous sedimentary rocks. Fossils of ammonoids, corals and bivalves were found in the black Permian sedimentary rocks. Layers of fine volcanic ash deposits formed the light grey colored tuffaceous layers interbedded with the brownish Cretaceous sediments. Ma Shi Chau is very close to a major fault (Tolo channel fault). Rocks on Ma Shi Chau are therefore subjected to deformation by fault activities. Various deformed structures such as folds, kink bands, microfaults and sheared rocks can be observed on Ma Shi Chau.
caption: A fold on Ma Shi Chau, Hong Kong. Red lines show the limbs,the blue line shows the axis
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