Permian rock garden of Hong Kong － Ma Shi Chau

Permian rock garden of Hong Kong － Ma Shi Chau
Background Information
The Tolo Channel Geo-Area includes the north shore of Tolo Channel, Ma Shi Chau on the southwest shore and Lai Chi Chong on the south shore. Most of the rocks along the north shore of Tolo Channel and at Bluff Head are the oldest in Hong Kong, formed about 400 million years ago during the Devonian Period. Ma Shi Chau presents the sedimentary rocks formed about 280 million years ago; the rocks are the second oldest rocks in the rock region; Lai Chi Chong showcases various volcanic rocks and sedimentary rocks formed about 146 million years ago. These two geo-sites also show distinctive geological features, such as faults and folds. Although the geology of Ma Shi Chau and Lai Chi Chong is a bit complicated, they are the ideal destinations for geologists. The 61-hectare Ma Shi Chau is made up of Ma Shi Chau, Yeung Chau, Centre Island and an unnamed islet to the northeast of Sam Mun Tsai New Village. Ma Shi Chau is the key site of Hong Kong's Permian Tolo Harbour Formation. Home to well-outcropped rocks, the island is an ideal location for studying strata, rock properties, sedimentation features and different geological compositions because here you can find faults and folds as well as deformed and displaced rock mass. The unnamed islet near Yim Tin Tsai, vegetated with dense woodlands, is a popular roosting ground for egrets and herons. Given such outstanding conservation value, the Ma Shi Chau region was declared a protected Special Area in 1999. The Ma Shi Chau nature trail runs along the southeastern shore of the island. 1.5 km in length, this route presents 16 attractions which highlight local geological features. By observing the rocks on site and reading trailside interpretation plates, visitors can understand how tombolos and various rocks are formed, as well as natural phenomena like wave erosion, weathering and folding .
Geological Information
	Outcropped strata dating back to the Permian (290,000,000 to 250,000,000 years ago) are extremely rare and isolated in Hong Kong. Tolo Harbour Formation is a particularly prominent example. This formation is mainly distributed across Tolo Harbour and its environs, such as Ma Shi Chau, Centre Island, the Chinese University of Hong Kong and the western shore of Three Fathoms Cove. Ma Shi Chau is a representative showcase of this formation. The well-outcropped rocks on the island are composed of mudstone, siltstone and sandstone deformed by folding . Centre Island to its south is made up of the same rocks. The sandstone there exhibit ripple marks corrugated and flaser-bedding, while the siltstone often manifests bioturbation. Extensive Permian sedimentary rock layers are not the only geological attraction of Ma Shi Chau. Here on the island, you can also find faults and folds, deformations and displacements. On the northwestern edge, some outcrops are part of the Early Jurassic Tolo Channel Formation. These include dark siltstone, mudstone and Late Jurassic sedimentary breccia, tuff and tuffite. The Permian rock at Ma Shi Chau is estimated to be approximately 500 metres thick. It has two lithofacies. The lower facies in the southeastern part of the island is an assembly of powdery grey to pale red calcareous siltstone and charcoal-tone alternation beds of mudstone, siltstone and sandstone. The sand content increases upwards progressively and transits to the approximately 0.5m thick sandstone beds. The upper facies in the northern part of the island is mainly thick layers of siltstone, sandstone and conglomerate. Depositional environment is stable and each layer is as thick as 1 metre. Fossils like mollusks, corals, bryozoans, brachiopodas and crinoids have been discovered both in the upper and lower facies. Judging from the rock facies and their features, as well as the presence of both marine fauna  fossils and terrestrial flora fossils, we can make a conjecture that the Permian rocks in Tolo Harbour and nearby regions were formed in a shallow estuary. The well developed stratification, alternate sandstone and siltstone beddings, as well as cross bedding or  flaser-bedding, are evidences of frequent changes in sediment sources and hydrodynamic conditions. All these are characteristics of a shallow estuary environment.

Memories of volcanic lava flows － Sharp Island (Kiu Tsui Chau)

Memories of volcanic lava flows － Sharp Island (Kiu Tsui Chau)
Background Information
Sharp Island (Kiu Tsui Chau) is just 2,000 metres off Sai Kung Pier. Set in Port Shelter, it lies southeast of Sai Kung town centre and east of Kau Sai Chau which is about 1 km away. This south-north trending island is long and narrow, extending some 2,500 metres long and about 500 metres wide from east to west. The highest point is 136 metres above sea level. Kiu Tsui Country Park is the smallest of its kind in Hong Kong. Covering only 100 hectares of island territories, its boundaries take in several islets, including Cham Pin Chau, Pak Sha Chau, Tai Tsan Chau, Cham Tau Chau and Kiu Tau. This popular holiday destination offers lucid water, silvery sand and dreamy vistas of island reefs and pristine woodlands. Visitors can explore the main island along a pleasant hiking trail, or walk across a spectacular natural sand levee that connects Sharp Island with neighbouring Kiu Tau. A sand levee is a coastal sedimentary landform. In geology, it is known as a tombolo. The Sharp Island tombolo is about 250 metres in length. It is flanked on both watersides by medium to fine grain sand and seashell debris, while the centre is coarse sand mixed with gravel. This natural tombolo is one of several tombolos found in Hong Kong. Similar terrain features can be seen in Pui O of Lantau and between Ma Shi Chau and Yim Tin Tsai. The Sharp Island tombolo is not always visible. Emerging only when low tide , it is a popular place for a seaside stroll or a dip in the sea.
Sharp Island is an iconic example of wave erosion landscape. Relentless erosive action has sculpted an eclectic array of bays and headlands : Hoi Sing Wan, Ha Mun Bay, Long Mong Wan, Shek Kwu Wan. Among them Kiu Tsui Beach and Ha Mun Bay are the best beaches. The former, situated near Sharp Island on the western shore of the island, is a favourite destination for seaside recreation. There are lifeguards on duty to ensure safety and visitor facilities include changing rooms, showers and a beachside barbecue area. The latter, situated in southern Sharp Island, is a crescent-shaped beach. Also known as Half Moon Bay, it is an excellent beach backing on to expansive grassland. Facilities include a barbecue area and campsite, changing rooms, showers and kiosk. It is one of the hottest swimming and barbecue destinations of the Sai Kung islands.
Tombolo is accessible when tidal level is lower than 1.4 meter. Visitors should note the tidal levels before crossing the tombolo. Please refer toHong Kong Observatory for tidal information.
Geological Information
	Most outcropped strata of Sharp Island belong to Mesozoic Cretaceous volcanic Clearwater Bay Formation, a formation composed primarily of flow-banded porphyritic rhyolite lava,  rhyolite breccia and eutaxitic vitric tuff. Clearwater Bay Formation is part of the Kau Sai Chau Volcanic Group, the youngest of its kind in the territory. It is marked by features of volcanic activities in Hong Kong during the final stage of the Mesozoic Era. Also found on Sharp Island, just below Clearwater Bay Formation, are Mang Kung Uk Formation volcanic rocks. The rock here is essentially tuffaceous siltstone mixed with crystal bearing fine ash vitric tuff and tuff breccia. All the above are extrusive volcanic rocks. Rhyolite is an acidic extrusive rock formed by solidification of cooled granitic magma extruded upon the ground surface. It is so named for the iconic flowing lines. Observed under a microscope, you can often find rhyolitic and porphyritic vitreous properties, pellets, felstone and micrographic textures. Phenocrysts are usually quartz and alkali feldspar, and occasionally containing a little plagioclase. The groundmass is usually tight cryptocrystalline or vitreous substances. In most cases, distribution of  rhyolite formed by lava flow is limited, as this type of rock is usually outpoured by relatively small volcanic domes and lava flows. Hong Kong is no exception. Apart from Sharp Island, similar flow-banded lava can only be found in Yim Tin Tsai. The rhyolite lava of Sharp Island is living record of ancient volcanic eruptions and lava flows. While characterised by flow lines, it is also highly porphyritic. The phenocrysts are mainly quartz and sanidine, with the occasional presence of plagioclase in varied concentrations. This rhyolitic and porphyritic structure is very often the product of devitrification. Rhyolitic lava is widely distributed in southeast coastal provinces of China, including Liaoning, Inner Mongolia, Hebei, Shanxi, Shandong, Jilin and Heilongjiang. Significant distributions of current acidic volcanic rocks are generally made of welded tuff. This rock is outpoured by sheets, volcanic domes and dykes. In Hong Kong, most outcropped volcanic rocks are such tuff emerging in island arcs and active margins or created by continental intraplate activities. The tectonic setting of Hong Kong lies within a continental margin. In the Late Jurassic and Early Cretaceous massive volcanic eruptions took place. Most volcanic rocks seen today were formed during such times. At the northern tip and west side of Sharp Island, you can find porphyritic fine to medium grained quartz monzonite. This is an acidic intrusive rock whose chemical composition is between granite and granodiorite. Granite and granodiorite are both acidic rocks with abundant quartz and feldspar substances. Major differences being that granodiorite is slightly less acidic than granite; granite contains more potash feldspar than plagioclase; and granodiorite contains more plagioclase (acidic plagioclase) than potash feldspar. When the plagioclase and potash feldspar contents are level, it is known as quartz monzonite. Given that the Sharp Island rock mass has the same property as the quartz monzonite in Tai Mong Tsai, Sai Kung, it is known as the Tai Mong Tsai Quartz Monzonite.

Danxia wonder at sea － Port Island (Chek Chau)

Danxia wonder at sea － Port Island (Chek Chau)
Background Information
Sitting at the mouth of Tolo Harbour in Tai Po, Port Island overlooks the southern Tap Mun Island. This uninhabited island may seem lone and barren, but it is the gateway of Tolo Harbour for it guards the strategic pass of Tolo Channel. As the Chinese name Chek Chau implies, Port Island is a place of red earth. The ground on the entire island is rust-coloured conglomerate and siltstone. From Wong Chuk Kok Hoi to Hung Shek Mun, past Tsat Shue Wan, Cheung Tsui to Hung Pai, it is a grandiose domain of red peaks, rusty soil, red earth and green trees. This extraordinary scene is known as “Danxia Wonder at Sea”.
Red earth landscapes are called “Danxia” wonders in China. Examples are Danxia Shan in Guangdong, Wuyi Shan in Fujian and Lungfu Shan in Jiangxi. Port Island is the number one representative of Hong Kong. Other danxia sites are Kung Chau, Ap Chau and the Hong Kong Red Sea. Dazzling red terrain is the biggest fascination of Port Island. The hills are completely covered with reddish-brown conglomerate and siltstone, making it a true “red island”. What brought about such unusual sights? Geologically, the answer lies in the ancient times. After more than 6 million years of robust lava and volcanic activities, most regions of Hong Kong became igneous rock terrains. When volcanic activities subsided, extended dry climate set in. Great temperature difference between day and night caused avalanches. Weathered rocks toppled down from the uplands and were quickly transported and deposited. Gravel, sand and silt arising from weathering were washed down by seasonal rainstorms to the alluvial plains where they settled. There, the ferric minerals within turned into iron oxide and bonded sand and other sediments to become a unique red sedimentary rock. Hot climate and the scorching sun aided release of iron in the sand and gravel. For this reason they were tinted red or rust in various intensities. Sediments of the alluvial plains and river channels eventually formed the red or coloured terrestrial clastic sedimentary rocks seen on Port Island today. Main components are conglomerate, sandstone and siltstone. These rocks are known as Port Island Formation.

Volcaniclastic sedimentary rock － Lai Chi Chong

Volcaniclastic sedimentary rock － Lai Chi Chong

Background Information

On the southeastern shore of Tolo Channel in the Eastern New Territories, a set of Early Cretaceous volcaniclastic sedimentary rock strata called Lai Chi Chong Formation are distributed around rural Lai Chi Chong and nearby coastal areas. They are “younger” than the sedimentary rock of Ma Shi Chau but “older” than that of Tung Ping Chau. Research has shown that this region has rather complicated geological setting and rock types, with Mesozoic volcaniclastic sedimentary rocks, tuff, rhyolite and Paleozoic sedimentary rocks occurring locally. The uneven stratum on the foreshore near the Lai Chi Chong pier is volcanic ash sedimentary rock. Displaying very distinctive foldings, faults and bedding structure, it is an ideal location for geological study.

Geological Information

Major outcropped sections of Lai Chi Chong Formation can be found on the beach west of Lai Chi Chong pier. Although less than 200m wide, these sections manifest extremely complicated rock properties that include tuffite ,tuffaceous sandstone, siltstone, coarse ash crystal tuff, eutaxitic fine ash tuff and porphyritic rhyolite in current bedding. Bedding development is excellent with a wealth of visible sedimentary structures, such as current bedding, graded bedding, convolute bedding and subaquatic slump. Signs occurring from folding, fault and discordance of strike directions are also clearly noticeable.

Double Haven (Yan Chau Tong)

Serene and picturesque marine park － Double Haven (Yan Chau Tong)

Background Information

Double Haven (Yan Chau Tong) rests on the northeastern shore of Plover Cove Country Park. The Chinese name Yan Chau Tong is probably inspired by an interesting looking islet which takes the shape of a stone seal. To conserve the wildlife and natural features of this lovely area, Double Haven was designated a marine park in 1996. Double Haven is a idyllic arcadia embraced by uplands. It owes its celestial tranquil setting to the surrounding hills. Well shielded on four sides from the open sea, it is relatively unaffected by the southeast summer monsoon and northwest winter monsoon. The air is a little dryer than other parts of Hong Kong and there is seldom heavy rain. Although a whole network of small streams flow into Double Haven, they never cause any widespread flooding. Bestowed with such supreme qualities, it is no surprise that Double Haven astonishes every first-time visitor with her stunning beauty. That unique serene mood is simply unimaginable in bustling Hong Kong.

Geological Information

The present landscape of Double Haven originates from a series of volcanic eruptions in the Middle Jurassic 180 million years ago. Devastating explosions destroyed the original sedimentary rock which comprised mainly sandstone and siltstone. Great clouds of volcanic ash mixed with lava settled on the ground and formed a volcanic rock stratum about 2,000 metres thick ¾ the coarse ash crystal tuff that extends from the area north of Sam A Wan to Lai Chi Wo and Sha Tau Kok today ¾ and Double Island, Crescent Island and Crooked Island. As eruptions and volcanic activities gradually stopped, this region underwent about 20 million years of erosion and weathering when rivers washed sand and gravels down the surrounding mountain ranges to settle in the downstream coastal flats. They formed the conglomerate, sandstone, siltstone and shale of Double Haven, Pat Sin Leng and Port Island (Chek Chau). The sedimentary rocks in these parts are about 500 metres thick.

Hong Kong Global Geopark

Local Participation As a Global Geoparks Network requirement, Hong Kong Global Geopark welcomes any public or private partnership proposal from the community to support the sustainable development of the geopark. Genuine and sustainable local participation Role of Hong Kong Global Geopark Geopark Principles for partnership recommendations

L’hotel Island South has made a partnership arrangement with Hong Kong Geopark to be the first “Hong Kong Geopark Hotel”.  The Hotel is committed to geoconservation and promotion of geopark concept.  Lobby and selected rooms are decorated with geopark theme.  Geopark videos are broadcasted in the hotel lobby and dedicated in-room TV channel.  Specially designed geopark menu is also available in the hotel to assist the publicity of geoconservation and geopark guided tours. Familiarization field trip Staff training

Friendly geo-facilities and service

TV booth for geotour e-Kiosk In-room TV channel Fossil decoration Geolicious Menu Factsheet Appetizer Dish Name Dish Description Geo Park Feature Picture Geo description Iconic Columnar Rocks Go On-stage Tuna Pyramid with Apricot Sauce Hexagonal Columnar Rock  Spectacular hexagonal columnar rock covers the whole Sai Kung area, they are the products of volcanic activities. The Classic Rock Cascade Italian Copper Ham with Potato Salad & Crispy Onion Bluff Head Bluff Head displays the oldest rock in Hong Kong. The inter-layered red and white rock strata formed about four hundred million years ago. Soup Dish Name Dish Description Geo Park Feature Picture Geo description The Cracked Dome Oven-baked Pumpkin Potage with Puff Pastry Sharp Island Continuous sun and rain lead to the exterior of boulders on sharp Island splitting into pieces, which look like a huge pineapple bun. Caution! The Bubbling Lava! Breaded Soup Beef Goulash Bluff Head Crater collapsed when it lost support and formed a large bowl -shaped Caldera. Main Course Dish Name Dish Description Geo Park Feature Picture Geo description Duck’s Eye over the Water Crispy Prawn Wrapped with Kataifi & Fresh Mango Sake Kasu Ap Chau Bedrock  The well-known Duck’s eye is a typical sea arch, it is formed by continued coastal erosion. Challenge the “Jenga” Rocks Oven-baked Australia Miso Cod Fillet with Leek & Matsutake Sedimentary Rock Sedimentary rock is layered rock which is formed by compaction of sediments accumulated in water layer by layer. Geo Trio Charcoal Grilled U.S. Short Rib with Egg-plant Gratin The Ninepin Group The Ninepin Group mainly consists of South, North and East Ninepin Islands. Huge hexagonal rock columns are widely distributed on the islands.   The Muddy Sandstone Crossover  Slow Cooked U.S. Beef Tenderloin with Green Tea Sea Salt Flakes Siltstone Siltstone is a kind of sedimentary rock which is formed by fine rock fragments, the texture is in between of mud and sand. Cake Series Dish Name Dish Description Geo Park Feature Picture Geo description Placoderm the Crispee Vanilla Ice Cream with Crispy Chocolate Placoderm Placoderm is an extinct fish. Its head to thorax were covered by armoured plates. Rock the Rockies Crispy Chocolate Parfait with Mocca Profiteroles Wang Chau Under the erosive power of waves, diverse coastal landforms are well developed along the Sai Kung coast, such as sea cliff and sea cave The Chocodeck Chocolate Mousse Mille Feuille Tung Ping Chau Tung Ping Chau is made up entirely of layered sedimentary rock, which is the youngest rock of Hong Kong with a history of about 55 million years. The Sleeping Beauty Chocolate Chiffron Dome  Volcano Around 160 million years ago, Hong Kong was in the period of volcanic activities, a series of violent volcanic eruption had occurred in Hong Kong. Requirements for organizations seeking a partnership arrangement with Hong Kong Global Geopark of China Be committed to geoconservation and the promotion of Hong Kong Global Geopark. Facilitate the promotion and operation of geopark tours led by Recommended Geopark Guides (R2G)s. Display or exhibit at prominent places in the venue(s) of the programme science popularisation and Hong Kong Global Geopark messages following the geopark communication concepts. Provide products which will help promote geopark branding. Ensure staff members in charge of the programme undertake geopark familiarization training. Designate staff member(s) of managerial grade to address to the geopark-related enquiries. Undertake to work closely with Hong Kong Global Geopark with a view to achieving the key objectives set by the Global Geoparks Network. A partner meeting the above requirements may use the Hong Kong Global Geopark logo as confined to geopark related products or activities agreed by Hong Kong Global Geopark. Either party may terminate this arrangement without advance notice by giving notice to the other in writing.

Geographic History of Hong Kong

Geographic overview A region in the southernmost corner of China, Hong Kong is part of the southeastern Pearl River estuary, neighbouring on Mount Nanling in the north and South China Sea in the south. Local topography is hilly with scattered coastal plains. The Hong Kong SAR comprises Hong Kong Island, Kowloon Peninsula, the New Territories which is connected to Mainland China, Lantau Island and more than 200 outlying islands. Approximate total land area is 1,104 square kilometres. Hong Kong has a myriad of landforms. The long, sinuous coastline is indeed a natural geological gallery, featuring spectacular landforms and rock formations shaped by waves and weathering. Here, one finds wave-cut sea cliffs, sea caves, sea arches, geos, sea stacks, notches and blowholes. Lying alongside are beaches, alluvial plains and mudflats which have come about thanks to millions of years of sedimentation. Inland areas showcase a variety of weathering characteristics. Terrain features arising from physical, chemical or biological weathering effects are prominent across peaks and valleys, ravines and escarpments. For further details, please refer to the publication of CEDD: Hong Kong Geology - A 400-Million Year Journey History

Years ago(Million) Over billions of years, the Earth went through many glacial ages of prolonged low temperature. The last ice age advanced the evolution of Hong Kong's landscape. In the last 2 million years, sea level saw a series of rises and falls. Correspondingly the land surface of Hong Kong was submerged and exposed by turns. There were significant temperature variations during this glacial period. When it was cold, ice glaciers around the world gained size and water was solidified into ice on land, Sea level dropped as the ice melted and land was submerged. During this time seawater of Hong Kong had dropped to 120 metres below the modern day level, while the coastline was 120 kilometres farther to the south. At the end of the last glacial age, rising sea level flooded land areas which were once river valleys. Previous valleys and mid-slopes turned into sinuous coasts and some peaks became islands the jagged coastline of Double Haven (Yan Chau Tong) and Sai Kung and the islands scattered offshore. Indeed, geological vicissitudes have created the most stunning masterpieces. The local climate got warmer and more humid in the last 60 million years. This change led to chemical decomposition of surface rocks and a soft loose layer vulnerable to erosion was established. Erosion persisted. Terrain features continued to evolve. As a result Hong Kong is bestowed with enchanting landforms. The local climate became extremely dry bout 100 million years ago. Conditions were similar to some areas of the Middle East today. Storms activated great and sudden floods. Sharp rocks that came off the peaks settled below the precipitous slopes, forming fan-shaped lithic shards between which intermittent streams coursed down to the lowlands. Along meandering river channels that flowed only in the wet season, pebbles settled while in other places wind carved out striking red sand dunes. Aided by river sediments these alluvial plains gave rise to the magenta sedimentary rocks seen today in Hung Shek Mun and Port Island(Chek Chau) of the Northeastern New Territories. Slowly, arid land moistened between 80 million and 50 million years ago. Rainfall was merely sufficient to form salt lakes nonetheless. In the rainy season when streams flowed, they washed mud, sand and clay into these water bodies. At other times the lakes were so dry the bottom mud cracked open. With the moisture evaporated, salt crystals appeared. In humid times, plants could survive and in turn supported the growth of insects. Remains of dead insects became fossils in the mud. In low-lying areas around Tung Ping Chau in the Northeastern New Territories, huge lakes once existed. As seasons and environments changed, mud and sand settled orderly in layers of different grain sizes. They formed range upon range of sedimentary rocks. These strata, extremely rich in fossils of plants, spore powder, archaeostraca and insects, are the youngest rocks in Hong Kong. Between 165 million and 140 million years ago, volcanic activities rocked the entire region known as the southeastern China coast today. With the magma chamber lying merely 1 to 2 kilometres below surface, eruptions were violent and produced huge clouds of volcanic ash. Falling ash and lava spread across the land, covering small bays and lake beds. These events changed the original landscape. When pyroclastic substances cooled down, they became volcanic rocks that we now see in Sai Kung, Lantau Island and Tai Mo Shan. In some instances where eruption-derived substances were so great in volume that the volcanoes collapsed. Huge round cavities appeared calderas. When volcanoes were less active, the calderas may get waterlogged. According to data for determining the absolute age of rocks, volcanic eruptions and magma intrusion activities took a cyclical pulse pattern. There were great magma intrusions during large eruptions in every cycle. The intrusive rocks so formed are the exposed granite distributed across the territory today, such as the granite strata of Hong Kong Island and the Kowloon Hills. Rainfall sometimes led to cyclical saturation of ground ash cover. For this reason rainfall had been an important factor in the formation of Hong Kong's ancient landscape. Water-saturated substances travelled down the slopes to reach lowlands. These volcanic mudflows were dense mixtures of water and ash. 140 million years ago, volcanic eruptions came to an end. There are no traces of volcanic cones in modern day Hong Kong because subsequently the mountains were seriously eroded. In a later age, sea level dropped considerably. Land around the edges was exposed and coastal marshes emerged. Later when these were submerged yet again their places were taken over by river deltas. During this time the sea level continued to rise, until 280 million years ago the whole territory became the bottom of a deep sea with rich deposits of silt and mud. Following a subsequent period of rising sea level and erosion, the ocean settled and became a medium depth environment between 210 million and 190 million years ago. A cover of silt and mud reappeared and ammonites throve in these waters. Their remains were buried in the mud for long ages and formed the fossils now found within mudstone. In the Early Carboniferous some 360 million years ago, a transgression induced profound changes to Hong Kong's landscape. The sea level rose progressively. Later, between 360 million and 320 million years ago, coastal floodplains were submerged by the tropical ocean. As there were only a handful of major rivers going out to sea, freshwater inflow was lucid and free of sediments. Warm and relatively silt-free ocean water made favourable habitats for diverse marine organisms, in particular those with skeleton and calcium carbonate shells. These species flourished in abundance. Their debris and shells settled on the seabed and formed a thick layer limestone. Covered by sediments, limestone was exposed to increasing pressure and heat. In time it was transformed into subterraneous grained white marble found under some areas of Hong Kong today. Given the many changes over the ages, fossils in these rocks are indistinguishable now. A good guess is that corals and algae, amongst others, lived and bred here. The oldest rocks in Hong Kong, formed by sediments, date back 400 million to 360 million years. Outcropped stratum can only be seen on the north coast of Tolo Channel in Northeastern Hong Kong. In the remote antiquity, stream originating in the southeastern uplands flowed down the hills, bringing sediments to settle at the estuaries. As multiple stream networks washed down sand and pebbles, local sand dunes were erosion. Meanwhile the uplands were reduced in elevation as a result of erosion. Their remaining masses produced finer sand and silt. The estuary floodplains covered by these substances were intruded intermittently by seawater.