The geology of Cambodia is the study of the nation's rocks, minerals, water and landforms. Cambodia's ancient geologic history in the Precambrian is poorly understood. The region experienced tectonic activity and low-grade metamorphic rock formation throughout the Paleozoic, which a shift to marine conditions and fossil formation during the Permian and through much of the Mesozoic. Few rocks remain from the Cenozoic. Cambodia has comparatively few natural resources, although there is bauxite formed from laterite weathering, as well as phosphorite, iron, gems, limestone and other materials. [1]
There are no dated Precambrian rocks in Cambodia, but the gneiss and schist of the Proterozoic Kontum Massif Vietnam extend into the northeast of the country from Vietnam. High-grade metamorphic rocks that may be from the Precambrian are also found at Pailin in the west. This area has gneiss and amphibolite, diorite, granodiorite and relatively uniform mineralogy including quartz, plagioclase and hornblende. [1]
Extensive Permian limestone rocks are found at Sisophon in the west and to the south at Kampot, containing coral and brachiopod fossils. These fossils helped to establish the age of the limestone which is sometimes interbedded with clastic rocks. There is extensive karst landscape with many caves underlying much of Cambodia.[ citation needed ]
Triassic rocks are very common in Cambodia, although they do not contain many fossils. Marine Triassic rocks are well documented near Rovieng in the north. Triassic rocks include shale, sandstone, conglomerates and some fragments of volcanic rocks including andesite. The Indosinian Orogeny in the Triassic affected the region with some moderate folding. Hydrocarbon research on the Khorat Plateau suggests that the Indochina Terrane was a series of continental fault blocks separated by Permian rifting. [2] Marine conditions were common, although the later periods were marked by lagoon and continent conditions and red beds formed.
During the Jurassic marine conditions returned. A fossil ammonite was found at one location in eastern Cambodia. The Sre Pok Valley has numerous beds of rock with ammonite fossils, recording deep water sediments near the Vietnamese border by the Middle Jurassic. Continental conditions were the norm and thick sequences of sandstone and conglomerate formed during the Cretaceous. These comprise much of the Cardamome Mountains in the southwest and can be up to one to two kilometers thick. Sometimes these rocks also contain plant and pollen remains. [1]
As far as dinosaurs go there have been no findings in Cambodia however it is not unlikely that they lived there.
There are very few Cenozoic rocks in Cambodia. However, there is quite a bit of evidence from the Quaternary, the last 2.5 million years, particularly in floodplains and valleys where terraces in the sediment are common. However, sometimes these deposits are very thin over underlying bedrock.[ citation needed ]
Cambodia has few natural resources, mainly gold and some non-metallic minerals. Artisanal mining often extracts gold bearing alluvium, which originated from quartz veins in different rocks. Gold was found at Suptrup in 1877 and mined until 1940.[ citation needed ]
Bauxite, iron ore, tin, greisen and aplite are also known, although only bauxite appears to be economically valuable. Bauxite formed from laterite weathering of Cenozoic basalt on the Haut Chhalong Plateau near the Vietnamese border. Phosphorite and limestone are the main non metallic minerals. Phosphorite forms in caves and fissures from Permian organic material. A small phosphorite mine opened in 1966 with a crushing plant after having first been worked starting in 1919. Cambodia also has gems including sapphire. Pailin, in the area of Bokeo is known for large, high quality zircon crystals. [1]
Geological mapping of Cambodia was first carried out by the French service, Service Geologique de l'Indochine based in Hanoi in the years between World War I and World War II. Various mineral prospects were explored at that time and again in the 1950s and 1960s with the assistance after independence of France, China in the UN between 1967 and 1970.[ clarification needed ] The whole country was mapped in a reconnaissance level by French geologists and a 1:200,000 scale map with 14 sheets was published. Out of a pre-1975 staff of 60 only eight returned including four technicians after the Khmer Rouge. Currently the responsibility for mapping rests with the Department of Geology and Mines and the Ministry of Industry.[ citation needed ]
Texas contains a wide variety of geologic settings. The state's stratigraphy has been largely influenced by marine transgressive-regressive cycles during the Phanerozoic, with a lesser but still significant contribution from late Cenozoic tectonic activity, as well as the remnants of a Paleozoic mountain range.
The geology of Germany is heavily influenced by several phases of orogeny in the Paleozoic and the Cenozoic, by sedimentation in shelf seas and epicontinental seas and on plains in the Permian and Mesozoic as well as by the Quaternary glaciations.
The geology of Mozambique is primarily extremely old Precambrian metamorphic and igneous crystalline basement rock, formed in the Archean and Proterozoic, in some cases more than two billion years ago. Mozambique contains greenstone belts and spans the Zimbabwe Craton, a section of ancient stable crust. The region was impacted by major tectonic events, such as the mountain building Irumide orogeny, Pan-African orogeny and the Snowball Earth glaciation. Large basins that formed in the last half-billion years have filled with extensive continental and marine sedimentary rocks, including rocks of the extensive Karoo Supergroup which exist across Southern Africa. In some cases these units are capped by volcanic rocks. As a result of its complex and ancient geology, Mozambique has deposits of iron, coal, gold, mineral sands, bauxite, copper and other natural resources.
The geology of Niger comprises very ancient igneous and metamorphic crystalline basement rocks in the west, more than 2.2 billion years old formed in the late Archean and Proterozoic eons of the Precambrian. The Volta Basin, Air Massif and the Iullemeden Basin began to form in the Neoproterozoic and Paleozoic, along with numerous ring complexes, as the region experienced events such as glaciation and the Pan-African orogeny. Today, Niger has extensive mineral resources due to complex mineralization and laterite weathering including uranium, molybdenum, iron, coal, silver, nickel, cobalt and other resources.
The geology of Arkansas includes deep 1.4 billion year old igneous crystalline basement rock from the Proterozoic known only from boreholes, overlain by extensive sedimentary rocks and some volcanic rocks. The region was a shallow marine, riverine and coastal environment for much of the early Paleozoic as multi-cellular life became commonplace. At the end of the Paleozoic in the Permian the region experienced coal formation and extensive faulting and uplift related to the Ouachita orogeny mountain building event. Extensive erosion of new highlands created a mixture of continental and marine sediments and much of the state remained flooded even into the last 66 million years of the Cenozoic. In recent Pleistocene and Holocene time, glacial sediments poured into the region from the north, down major rivers, forming dunes and sedimentary ridges. Today, Arkansas has an active oil and gas industry, although hydraulic fracturing related earthquake swarms have limited extraction. Mining industries in the state also produce brines, sand, gravel and other industrial minerals.
The geology of South Sudan is founded on Precambrian igneous and metamorphic rocks, that cover 40 percent of the country's surface and underlie other rock units. The region was affected by the Pan-African orogeny in the Neoproterozoic and extensional tectonics in the Mesozoic that deposited very thick oil-bearing sedimentary sequences in rift basins. Younger basalts, sandstones and sediments formed in the last 66 million years of the Cenozoic. The discovery of oil in 1975 was a major factor in the Second Sudanese Civil War, leading up to independence in 2011. The country also has gold, copper, cobalt, zinc, iron, marble, limestone and dolomite.
The geology of Morocco formed beginning up to two billion years ago, in the Paleoproterozoic and potentially even earlier. It was affected by the Pan-African orogeny, although the later Hercynian orogeny produced fewer changes and left the Maseta Domain, a large area of remnant Paleozoic massifs. During the Paleozoic, extensive sedimentary deposits preserved marine fossils. Throughout the Mesozoic, the rifting apart of Pangaea to form the Atlantic Ocean created basins and fault blocks, which were blanketed in terrestrial and marine sediments—particularly as a major marine transgression flooded much of the region. In the Cenozoic, a microcontinent covered in sedimentary rocks from the Triassic and Cretaceous collided with northern Morocco, forming the Rif region. Morocco has extensive phosphate and salt reserves, as well as resources such as lead, zinc, copper and silver.
The geology of Nigeria formed beginning in the Archean and Proterozoic eons of the Precambrian. The country forms the Nigerian Province and more than half of its surface is igneous and metamorphic crystalline basement rock from the Precambrian. Between 2.9 billion and 500 million years ago, Nigeria was affected by three major orogeny mountain-building events and related igneous intrusions. Following the Pan-African orogeny, in the Cambrian at the time that multi-cellular life proliferated, Nigeria began to experience regional sedimentation and witnessed new igneous intrusions. By the Cretaceous period of the late Mesozoic, massive sedimentation was underway in different basins, due to a large marine transgression. By the Eocene, in the Cenozoic, the region returned to terrestrial conditions.
The geology of Ohio formed beginning more than one billion years ago in the Proterozoic eon of the Precambrian. The igneous and metamorphic crystalline basement rock is poorly understood except through deep boreholes and does not outcrop at the surface. The basement rock is divided between the Grenville Province and Superior Province. When the Grenville Province crust collided with Proto-North America, it launched the Grenville orogeny, a major mountain building event. The Grenville mountains eroded, filling in rift basins and Ohio was flooded and periodically exposed as dry land throughout the Paleozoic. In addition to marine carbonates such as limestone and dolomite, large deposits of shale and sandstone formed as subsequent mountain building events such as the Taconic orogeny and Acadian orogeny led to additional sediment deposition. Ohio transitioned to dryland conditions in the Pennsylvanian, forming large coal swamps and the region has been dryland ever since. Until the Pleistocene glaciations erased these features, the landscape was cut with deep stream valleys, which scoured away hundreds of meters of rock leaving little trace of geologic history in the Mesozoic and Cenozoic.
The geology of Alberta encompasses parts of the Canadian Rockies and thick sedimentary sequences, bearing coal, oil and natural gas, atop complex Precambrian crystalline basement rock.
The geology of Utah, in the western United States, includes rocks formed at the edge of the proto-North American continent during the Precambrian. A shallow marine sedimentary environment covered the region for much of the Paleozoic and Mesozoic, followed by dryland conditions, volcanism, and the formation of the basin and range terrain in the Cenozoic.
The geology of Laos includes poorly defined oldest rocks. Marine conditions persisted for much of the Paleozoic and parts of the Mesozoic, followed by periods of uplift and erosion. The country has extensive salt, gypsum and potash, but very little hydrocarbons and limited base metals.
The geology of Afghanistan includes nearly one billion year old rocks from the Precambrian. The region experienced widespread marine transgressions and deposition during the Paleozoic and Mesozoic, that continued into the Cenozoic with the uplift of the Hindu Kush mountains.
The geology of Thailand includes deep crystalline metamorphic basement rocks, overlain by extensive sandstone, limestone, turbidites and some volcanic rocks. The region experienced complicated tectonics during the Paleozoic, long-running shallow water conditions and then renewed uplift and erosion in the past several million years ago.
The geology of North Korea has been studied by the Central Geological Survey of Mineral Resources, rare international research and by inference from South Korea's geology.
The geology of Bulgaria consists of two major structural features. The Rhodope Massif in southern Bulgaria is made up of Archean, Proterozoic and Cambrian rocks and is a sub-province of the Thracian-Anatolian polymetallic province. It has dropped down, faulted basins filled with Cenozoic sediments and volcanic rocks. The Moesian Platform to the north extends into Romania and has Paleozoic rocks covered by rocks from the Mesozoic, typically buried by thick Danube River valley Quaternary sediments. In places, the Moesian Platform has small oil and gas fields. Bulgaria is a country in southeastern Europe. It is bordered by Romania to the north, Serbia and North Macedonia to the west, Greece and Turkey to the south, and the Black Sea to the east.
The geology of Lithuania consists of ancient Proterozoic basement rock overlain by thick sequences of Paleozoic, Mesozoic and Cenozoic marine sedimentary rocks, with some oil reserves, abundant limestone, dolomite, phosphorite and glauconite. Lithuania is a country in the Baltic region of northern-eastern Europe.
The geology of Greece is highly structurally complex due to its position at the junction between the European and African tectonic plates.
The geology of the Czech Republic is very tectonically complex, split between the Western Carpathian Mountains and the Bohemian Massif.
The geology of Italy includes mountain ranges such as the Alps and the Apennines formed from the uplift of igneous and primarily marine sedimentary rocks all formed since the Paleozoic. Some active volcanoes are located in Insular Italy.