Columnar joints of high island formation in Hong Kong : comparison with overseas examples

Abstract

Columnar joints have been studied comprehensively in overseas examples. However, few studies were carried out on columnar joints of High Island Formation in Hong Kong. This dissertation gives a basic introduction to overseas columnar joints including the origin, terminology, field and laboratory studies and relationship between parameters.122columns in 7 locations in Sai Kung, Hong Kong were studied with regard to the geometry, surface morphology and joint development sequence. After data analysis, the columns in Hong Kong were compared with 4431overseas columns recorded in literature. Columnar joints in Hong Kong were found to be different from the overseas examples in a number of aspects. The columns in Hong Kong were found larger, more regular and more mature. The well-recorded striae and plumose structures in literature were not discovered on the columnar joint surfaces in Hong Kong, however, newly recorded parallel wavy pattern were commonly found near the East Dam. No evidence of upwards or downwards joint propagation can be found on the columnar joints in Hong Kong, while the columnar joints in Long Ke –C outcrop were developed towards south. The mechanism and formation environment of columnar joints in Hong Kong still need further study.