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Plate 5 - Near Vertical Quartzitic Sandstone, of the Carboniferous Mai Po Member Younging andDipping to the East, at San Shek Wan (0678 1570)Plate 6- Finely Laminated Siltstone and Fine-grained Sandstone, of the Carboniferous Mai PoMember on the Western Foreshore (1606 2194) of East Brother Island (Siu Mo To)
Reef Island. The northern end of the island is mainly composed of quartzite, which forms the island's highestpoint. The strata are massive, or poorly bedded, but a steeply inclined, northerly-dipping, graphitic parting occurs.The silty sandstone to the south contains nodules, possibly iron-cemented, and pebbly patches. Bedding, which dips71° northnorthwest, is well defined in these red-weathering sandstones. The centre of the island is also comprisedof red-weathering silty sandstone, whereas the southern end is composed of finely bedded, or massive quartziticsandstone and graphitic siltstone. The graphitic rock is locally spotted, and may be hornfelsed Generally, the stratadip very shallowly, varying locally up to 29°, towards the northwest or northnorthwest. There are two distinctgraphite siltstone beds, each several metres thick.PetrographyThe fine-grained sandstones and siltstones are predominantly quartzitic. In sample HK 2802(0636 1492) from Sham Wat, the quartz is largely recrystallized, and forms part of aquartz-sericite matrix with grains around 0.2 mm. Some relict quartz grains are still visible, butthe metasandstone is veined, as well as altered, and most original textures are obscured. Phylliticmetasiltstone from Sham Wat (HK 2805, 0624 1514) is greenish white in hand specimen, and isdominantly comprised of a quartz-sericite matrix containing a few quartz crystal relicts, up to0.1 mm.Evidence of the thermal metamorphism on The Brothers islands can be seen in a carbonaceoussandstone from Reef Island (HK8011, 15882083) which contains well developed andalusitecrystals, with chiastolite crosses, about 0.8 mm across. The margins of the andalusite aresericitized. The matrix is dominated by quartz crystals, up to 3 mm across, which displayundulose extinction, together with microcrystalline opaque graphite. Light brown, slightlyweathered, graphitic siltstone with wavy, or flaser cross-bedding from West Brother island,contains abundant opaque microcrystalline graphite flakes, visible in thin section (HK8017,1447 2160). The quartz sericite matrix is dominantly less than 0.1 mm in grain size.PalaeontologyGraphite from West Brother island (HK7250, 14602115) yielded a sparse microfauna(Appendix 1) including Calamospora breviradiata and Densosporites annulatus. The faunaindicate a Carboniferous, and possibly early Carboniferous age. A few miospores, obtained froma graphitic siltstone from Tai O (HK9284, 0276 1307), include (Appendix 1) Knoxisporiteslitheratus, Lycospora pusilla and Gorgonispaeridium sp,, all of which occur in Carboniferousstrata in South China. Other graphitic rocks failed to yield recognisable palynomorphs. Thislimited palaeontological evidence tends to confirm the correlation of strata at Tai 0, and on TheBrothers, with similar lithologies in the northwest New Territories which contain better preservedmicrofauna.Sedimentary EnvironmentThe wavy and lenticular bedding in the fine sedimentary rocks suggests a tidal flat, or delta frontenvironment of deposition. This type of bedding commonly forms where there are fluctuations insediment supply, or current (or wave) activity. Other sedimentary structures, such as small-scalecross- bedding and grading in the fine-grained sandstones, together with rapidly alternating bedsof siltstone and fine-grained sandstone, indicate a shallow water environment with varying tidalor fluvial influences. The carbonaceous material indicates a neritic environment, probably in afan delta. Overall, the facies association is typical of a neritic tidal swamp or deltaic alluvial fan.Evidence from the northwest New Territories (Langford et al, 1989) indicates progradation froma distal to a proximal fluvial floodplain sequence as the sediment coarsens into the overlying TaiShek Mo Member,35
Page 2 and 3: UNIVERSITY OF HONG KONGLIBRARIES
Page 4 and 5: © Government of Hong KongPublished
Page 7 and 8: CONTENTSTitle pagePage1ForewordCont
Page 9 and 10: Distribution and Lithology 73Detail
Page 11 and 12: Chapter 10 Economic Geology 149Intr
Page 13 and 14: (Plates)Plate 22 - Porphyritic Medi
Page 15: Table 1 — Grain Size Description
Page 18 and 19: 0 1 2 3 4 5 k mCONTOURS AT 100m INT
Page 20 and 21: properties of the marine deposits b
Page 22 and 23: Archival DataAll records from the s
Page 24 and 25: Chapter 2Outline of GeologyThe soli
Page 26 and 27: The Mesozoic volcanic rocks are div
Page 29 and 30: Chapter 3Palaeozoic Sedimentary Roc
Page 31 and 32: Carboniferous metasedimentaiy rocks
Page 33 and 34: Plate 1 - Fining-Upward Sequence of
Page 35: Plate 3 - Well-bedded Sandstones an
Page 39 and 40: Table 3. Evolution of Nomenclature
Page 41 and 42: are crudely stratified and welded i
Page 43 and 44: Shing Mun FormationThe type localit
Page 45 and 46: Tai Che Tung. Crystal tuff, interpr
Page 47 and 48: Plate 7 • Lapilli-Ash Crystal Tuf
Page 49 and 50: Plate 11 - Pyroclastic Breccia (086
Page 51 and 52: appears fragmental, and contains mu
Page 53 and 54: exposures in the stream bed consist
Page 55 and 56: Lin Fa Shan. The steep eastern flan
Page 57 and 58: dipping northwest at 46°, is prese
Page 59 and 60: Sunset Peak MemberThe Sunset Peak M
Page 61 and 62: Plate 16- Block and Lapilli-bearing
Page 63 and 64: Chapter 5Major IntrusionsClassifica
Page 65 and 66: in grain size from 0.4 to 1.5 mm, a
Page 67 and 68: 20 - Megacrystic Medium-grained Gra
Page 69 and 70: Pui O Wan. Porphyritic medium-grain
Page 71 and 72: minimum age of c. 145 Ma (see earli
Page 73 and 74: The granite on Chek Lap Kok is most
Page 75 and 76: Southeast of Tin Sam, on the wester
Page 77 and 78: About 1 km east of Nam Shan, exposu
Page 79 and 80: Plate 25 - Thin Section of Porphyri
Page 81 and 82: Chapter 6Minor IntrusionsIntroducti
Page 83 and 84: The microgranite grades southwards
Page 85 and 86: the Lantau Formation, however, and
Page 87 and 88:
Plate 29 - Flow-banded Quartzphyric
Page 89 and 90:
also cut volcanic rocks of the Tsue
Page 91 and 92:
Silver Mine Bay. On the headland so
Page 93 and 94:
Plate 33 - Core stone Development i
Page 95:
Plate 37 - Thin Section ofLamprophy
Page 98 and 99:
Pre-Yensfaanlan StructureWithin the
Page 100 and 101:
separates areas of different lithol
Page 102 and 103:
NeotectonicsFault activity in the r
Page 105 and 106:
Chapter 8Metamorphism and Alteratio
Page 107 and 108:
the majority of rocks in the distri
Page 109:
Chapter 9Superficial GeologyIntrodu
Page 112 and 113:
Detailstal O. Alluvial deposits for
Page 114 and 115:
trains. The regolith on most steep
Page 116 and 117:
Plate 44 - Boulder Debris on the So
Page 118 and 119:
gazetted for recreational purposes.
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DetailsTai O. Extensive intertidal
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Plate 48 - Sandy Beach at Fan Lau S
Page 124 and 125:
Pre-Chek Lap Kok Formation Deposits
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formation. The sequence is usually
Page 128 and 129:
BOREHOLE NO: ESC 17GRID REFERENCE:
Page 130 and 131:
BOREHOLE NO: A5/1GRID REFERENCE: 80
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formation, thinly laminated clays o
Page 134 and 135:
Quinqueloculina seminulum, which is
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Channel and Transgressive Deposits.
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Figure 20 - Areas of Acoustic Turbi
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West Lamma Channel These may be att
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Figure 23 - Depth-Averaged, Maximum
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The formation is Holocene in age. T
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Boreholes (A5/1, A5/2, B2/1, ESC17
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Plate 51 - Deep Weathering Profile
Page 151 and 152:
Chapter 10Economic GeologyIntroduct
Page 153 and 154:
Non-metalliferous MineralsFissure v
Page 155 and 156:
REFERENCESAddison, R. (1986). Geolo
Page 157 and 158:
James, J.W.C. (1993). The offshore
Page 159 and 160:
Sewell, R.J., Strange, PJ., Langfor
Page 161 and 162:
Appendix 1Microfossils identified f
Page 163 and 164:
Appendix 2 (continued)Sample HK9913
Page 165 and 166:
Appendix 2 (continued)Sample HK1054
Page 167 and 168:
Appendix 4aSelective normalized pal
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,Appendix 5 -Radiocarbon and Other
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construction materials 151contact m
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molybdenite 149Mong Tung Hang 151Mo
Page 175 and 176:
talus 107,115Tarn Tsui Wan 71,87Tan
Page 177:
LB 555.125 G34 LGeology of Lantaii
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