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Two samples from Lantau Peak, analysed for miospores by Qin G.R. (Institute of GeologicalSciences of Guangdong Province, written communication, 28 August 1990) (Appendix 3),produced varied miospore populations. Sample HK9329 (1032 1224) is a grey, poorly laminated,slightly tuffaceous mudstone from an exposure on the footpath about 1 km east of Lantau Peak.Qin has reported that several species obtained from this sample also occur in Mesozoic flora inSouth China, and that the dominance of Classopollis annulatus and Psophosphaera minorindicates a Late Jurassic age. A sample (HK 9314, 0927 1086) of grey, finely laminatedmudstone from Kau Nga Ling, about 1.5 km south of Lantau Peak, had insufficient diagnosticmiospore species to constrain it to anything other than the Jurassic.The age of these sedimentary rocks has also been constrained by isotopic dating of quartz syeniteintrusions, at Tong Fuk and Fan Lau, which clearly cross-cut the Lantau Formation. Hence, theminimum age of the sedimentary rocks is c. 145 my (early Late Jurassic; see Darbyshire, 1993).The Early Cretaceous age proposed by Lee et al (1990) appears, therefore, to be too young, andeven the Late Jurassic age suggested by Qin (written communication, 28 August 1990) may betoo young. Other palaeontological ages discussed above are equivocal, but a late Middle to earlyLate Jurassic age is not inconsistent with available field evidence.Cheung Shan MemberThe Cheung Shan Member is defined for the first time in this memoir. It is the basal, eutaxiticmember of the Lantau Formation, and its type locality is on Cheung Shan in west Lantau Island,where it is about 500 m thick. The member is locally unconformably overlain by rhyolite lavas ofthe upper part of the Lantau Formation. Its contact with Carboniferous strata to the northwest isa high-angle reverse fault.In the hills south of Tai 0, the member is about 150m thick. It is succeeded by siltstonc andlava, and overlies tuff of the Shing Mun Formation. Eutaxite, interpreted as part of the samebasal member, is also exposed at Cheung Sha between tuffs below, and rhyolite lava above; therethe member is about 200 m thick. Farther west, the wispy fiamme, which are generally less than20 mm long, are distinctive. The eutaxite is greyish-white to light red and yellow, with relictquartz crystals up to 2 mm across. Fresh exposures of eutaxite are only seen in south LantauIsland, where the rock is a grey, or light grey, crystal-bearing vitric tuff. Thin, wispy fiamme,ranging from 1 to 20 mm in length, are visible on weathered surfaces.DetailsCheung Shan. West of the summit of Cheung Shan, there are exposures of lithic lapilli-bearing tuff and eutaxite.The eutaxite is the main component of this pyroclastic member. The eutaxitic fabric is well preserved even thoughsome exposures display a well-developed platy foliation in addition to alteration of feldspars and matrix. Exposures(0535 1390) on a knoll northwest of Cheung Shan consist of greyish-white eutaxite, weathering red and yellow,with abundant relict, wispy fiamme up to 10 mm wide and 40 mm long, and relict quartz crystals up to 2 mmacross. Nearby exposures (0555 1370) of tuff contain small, pebble-like lithic lapilli set in a vitric matrix.Sham Wat. On the southeast side of Sham Wat Wan, the contact between Carboniferous siltstone to the north andtuff to the south is well exposed. The tuff is light grey, but reddish in parts, with quart/, crystals, mostly less than2 mm across, but ranging up to 8 mm. As well as abundant relict fiamme, there are scarce, siliceous, pebble-likelapilli. These can be up to 200 mm long and are composed of porphyritic rhyolite with strongly alignedpseudomorphs after feldspar and mafic crystals. Unlike the typical eutaxite of this member, these rocks arecharacterized by large fiamme. The flattened fiamme dip to the southwest at 18°, contrasting with the steep,easterly dip of the Carboniferous strata. The contact with the Carboniferous is a near-vertical fault, trendingnortheast-southwest,San Chau. On the ridge and headland west of San Chau, the structural association of the eutaxite andCarboniferous strata is complex. A knoll (0489 1417) south of the contact, consists of light grey, finely foliatedeutaxite which weathers to red and yellow. The rock only occurs as boulders from which it is not possible tomeasure the dip of the primary pyroclastic fabric. To the north, there is an isolated outcrop (048 144) of eutaxitewhich is interpreted as being in faulted contact with Carboniferous strata on both sides. A streaky eutaxitie fabric,54